Migrate away from templ and towards html/template

60 files changed, 22353 insertions, 0 deletions

diff --git a/vendor/golang.org/x/tools/go/ast/astutil/enclosing.go b/vendor/golang.org/x/tools/go/ast/astutil/enclosing.go
new file mode 100644
index 0000000..6e34df4
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ast/astutil/enclosing.go
@@ -0,0 +1,654 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package astutil
+
+// This file defines utilities for working with source positions.
+
+import (
+	"fmt"
+	"go/ast"
+	"go/token"
+	"sort"
+)
+
+// PathEnclosingInterval returns the node that encloses the source
+// interval [start, end), and all its ancestors up to the AST root.
+//
+// The definition of "enclosing" used by this function considers
+// additional whitespace abutting a node to be enclosed by it.
+// In this example:
+//
+//	z := x + y // add them
+//	     <-A->
+//	    <----B----->
+//
+// the ast.BinaryExpr(+) node is considered to enclose interval B
+// even though its [Pos()..End()) is actually only interval A.
+// This behaviour makes user interfaces more tolerant of imperfect
+// input.
+//
+// This function treats tokens as nodes, though they are not included
+// in the result. e.g. PathEnclosingInterval("+") returns the
+// enclosing ast.BinaryExpr("x + y").
+//
+// If start==end, the 1-char interval following start is used instead.
+//
+// The 'exact' result is true if the interval contains only path[0]
+// and perhaps some adjacent whitespace.  It is false if the interval
+// overlaps multiple children of path[0], or if it contains only
+// interior whitespace of path[0].
+// In this example:
+//
+//	z := x + y // add them
+//	  <--C-->     <---E-->
+//	    ^
+//	    D
+//
+// intervals C, D and E are inexact.  C is contained by the
+// z-assignment statement, because it spans three of its children (:=,
+// x, +).  So too is the 1-char interval D, because it contains only
+// interior whitespace of the assignment.  E is considered interior
+// whitespace of the BlockStmt containing the assignment.
+//
+// The resulting path is never empty; it always contains at least the
+// 'root' *ast.File.  Ideally PathEnclosingInterval would reject
+// intervals that lie wholly or partially outside the range of the
+// file, but unfortunately ast.File records only the token.Pos of
+// the 'package' keyword, but not of the start of the file itself.
+func PathEnclosingInterval(root *ast.File, start, end token.Pos) (path []ast.Node, exact bool) {
+	// fmt.Printf("EnclosingInterval %d %d\n", start, end) // debugging
+
+	// Precondition: node.[Pos..End) and adjoining whitespace contain [start, end).
+	var visit func(node ast.Node) bool
+	visit = func(node ast.Node) bool {
+		path = append(path, node)
+
+		nodePos := node.Pos()
+		nodeEnd := node.End()
+
+		// fmt.Printf("visit(%T, %d, %d)\n", node, nodePos, nodeEnd) // debugging
+
+		// Intersect [start, end) with interval of node.
+		if start < nodePos {
+			start = nodePos
+		}
+		if end > nodeEnd {
+			end = nodeEnd
+		}
+
+		// Find sole child that contains [start, end).
+		children := childrenOf(node)
+		l := len(children)
+		for i, child := range children {
+			// [childPos, childEnd) is unaugmented interval of child.
+			childPos := child.Pos()
+			childEnd := child.End()
+
+			// [augPos, augEnd) is whitespace-augmented interval of child.
+			augPos := childPos
+			augEnd := childEnd
+			if i > 0 {
+				augPos = children[i-1].End() // start of preceding whitespace
+			}
+			if i < l-1 {
+				nextChildPos := children[i+1].Pos()
+				// Does [start, end) lie between child and next child?
+				if start >= augEnd && end <= nextChildPos {
+					return false // inexact match
+				}
+				augEnd = nextChildPos // end of following whitespace
+			}
+
+			// fmt.Printf("\tchild %d: [%d..%d)\tcontains interval [%d..%d)?\n",
+			// 	i, augPos, augEnd, start, end) // debugging
+
+			// Does augmented child strictly contain [start, end)?
+			if augPos <= start && end <= augEnd {
+				if is[tokenNode](child) {
+					return true
+				}
+
+				// childrenOf elides the FuncType node beneath FuncDecl.
+				// Add it back here for TypeParams, Params, Results,
+				// all FieldLists). But we don't add it back for the "func" token
+				// even though it is is the tree at FuncDecl.Type.Func.
+				if decl, ok := node.(*ast.FuncDecl); ok {
+					if fields, ok := child.(*ast.FieldList); ok && fields != decl.Recv {
+						path = append(path, decl.Type)
+					}
+				}
+
+				return visit(child)
+			}
+
+			// Does [start, end) overlap multiple children?
+			// i.e. left-augmented child contains start
+			// but LR-augmented child does not contain end.
+			if start < childEnd && end > augEnd {
+				break
+			}
+		}
+
+		// No single child contained [start, end),
+		// so node is the result.  Is it exact?
+
+		// (It's tempting to put this condition before the
+		// child loop, but it gives the wrong result in the
+		// case where a node (e.g. ExprStmt) and its sole
+		// child have equal intervals.)
+		if start == nodePos && end == nodeEnd {
+			return true // exact match
+		}
+
+		return false // inexact: overlaps multiple children
+	}
+
+	// Ensure [start,end) is nondecreasing.
+	if start > end {
+		start, end = end, start
+	}
+
+	if start < root.End() && end > root.Pos() {
+		if start == end {
+			end = start + 1 // empty interval => interval of size 1
+		}
+		exact = visit(root)
+
+		// Reverse the path:
+		for i, l := 0, len(path); i < l/2; i++ {
+			path[i], path[l-1-i] = path[l-1-i], path[i]
+		}
+	} else {
+		// Selection lies within whitespace preceding the
+		// first (or following the last) declaration in the file.
+		// The result nonetheless always includes the ast.File.
+		path = append(path, root)
+	}
+
+	return
+}
+
+// tokenNode is a dummy implementation of ast.Node for a single token.
+// They are used transiently by PathEnclosingInterval but never escape
+// this package.
+type tokenNode struct {
+	pos token.Pos
+	end token.Pos
+}
+
+func (n tokenNode) Pos() token.Pos {
+	return n.pos
+}
+
+func (n tokenNode) End() token.Pos {
+	return n.end
+}
+
+func tok(pos token.Pos, len int) ast.Node {
+	return tokenNode{pos, pos + token.Pos(len)}
+}
+
+// childrenOf returns the direct non-nil children of ast.Node n.
+// It may include fake ast.Node implementations for bare tokens.
+// it is not safe to call (e.g.) ast.Walk on such nodes.
+func childrenOf(n ast.Node) []ast.Node {
+	var children []ast.Node
+
+	// First add nodes for all true subtrees.
+	ast.Inspect(n, func(node ast.Node) bool {
+		if node == n { // push n
+			return true // recur
+		}
+		if node != nil { // push child
+			children = append(children, node)
+		}
+		return false // no recursion
+	})
+
+	// Then add fake Nodes for bare tokens.
+	switch n := n.(type) {
+	case *ast.ArrayType:
+		children = append(children,
+			tok(n.Lbrack, len("[")),
+			tok(n.Elt.End(), len("]")))
+
+	case *ast.AssignStmt:
+		children = append(children,
+			tok(n.TokPos, len(n.Tok.String())))
+
+	case *ast.BasicLit:
+		children = append(children,
+			tok(n.ValuePos, len(n.Value)))
+
+	case *ast.BinaryExpr:
+		children = append(children, tok(n.OpPos, len(n.Op.String())))
+
+	case *ast.BlockStmt:
+		children = append(children,
+			tok(n.Lbrace, len("{")),
+			tok(n.Rbrace, len("}")))
+
+	case *ast.BranchStmt:
+		children = append(children,
+			tok(n.TokPos, len(n.Tok.String())))
+
+	case *ast.CallExpr:
+		children = append(children,
+			tok(n.Lparen, len("(")),
+			tok(n.Rparen, len(")")))
+		if n.Ellipsis != 0 {
+			children = append(children, tok(n.Ellipsis, len("...")))
+		}
+
+	case *ast.CaseClause:
+		if n.List == nil {
+			children = append(children,
+				tok(n.Case, len("default")))
+		} else {
+			children = append(children,
+				tok(n.Case, len("case")))
+		}
+		children = append(children, tok(n.Colon, len(":")))
+
+	case *ast.ChanType:
+		switch n.Dir {
+		case ast.RECV:
+			children = append(children, tok(n.Begin, len("<-chan")))
+		case ast.SEND:
+			children = append(children, tok(n.Begin, len("chan<-")))
+		case ast.RECV | ast.SEND:
+			children = append(children, tok(n.Begin, len("chan")))
+		}
+
+	case *ast.CommClause:
+		if n.Comm == nil {
+			children = append(children,
+				tok(n.Case, len("default")))
+		} else {
+			children = append(children,
+				tok(n.Case, len("case")))
+		}
+		children = append(children, tok(n.Colon, len(":")))
+
+	case *ast.Comment:
+		// nop
+
+	case *ast.CommentGroup:
+		// nop
+
+	case *ast.CompositeLit:
+		children = append(children,
+			tok(n.Lbrace, len("{")),
+			tok(n.Rbrace, len("{")))
+
+	case *ast.DeclStmt:
+		// nop
+
+	case *ast.DeferStmt:
+		children = append(children,
+			tok(n.Defer, len("defer")))
+
+	case *ast.Ellipsis:
+		children = append(children,
+			tok(n.Ellipsis, len("...")))
+
+	case *ast.EmptyStmt:
+		// nop
+
+	case *ast.ExprStmt:
+		// nop
+
+	case *ast.Field:
+		// TODO(adonovan): Field.{Doc,Comment,Tag}?
+
+	case *ast.FieldList:
+		children = append(children,
+			tok(n.Opening, len("(")), // or len("[")
+			tok(n.Closing, len(")"))) // or len("]")
+
+	case *ast.File:
+		// TODO test: Doc
+		children = append(children,
+			tok(n.Package, len("package")))
+
+	case *ast.ForStmt:
+		children = append(children,
+			tok(n.For, len("for")))
+
+	case *ast.FuncDecl:
+		// TODO(adonovan): FuncDecl.Comment?
+
+		// Uniquely, FuncDecl breaks the invariant that
+		// preorder traversal yields tokens in lexical order:
+		// in fact, FuncDecl.Recv precedes FuncDecl.Type.Func.
+		//
+		// As a workaround, we inline the case for FuncType
+		// here and order things correctly.
+		// We also need to insert the elided FuncType just
+		// before the 'visit' recursion.
+		//
+		children = nil // discard ast.Walk(FuncDecl) info subtrees
+		children = append(children, tok(n.Type.Func, len("func")))
+		if n.Recv != nil {
+			children = append(children, n.Recv)
+		}
+		children = append(children, n.Name)
+		if tparams := n.Type.TypeParams; tparams != nil {
+			children = append(children, tparams)
+		}
+		if n.Type.Params != nil {
+			children = append(children, n.Type.Params)
+		}
+		if n.Type.Results != nil {
+			children = append(children, n.Type.Results)
+		}
+		if n.Body != nil {
+			children = append(children, n.Body)
+		}
+
+	case *ast.FuncLit:
+		// nop
+
+	case *ast.FuncType:
+		if n.Func != 0 {
+			children = append(children,
+				tok(n.Func, len("func")))
+		}
+
+	case *ast.GenDecl:
+		children = append(children,
+			tok(n.TokPos, len(n.Tok.String())))
+		if n.Lparen != 0 {
+			children = append(children,
+				tok(n.Lparen, len("(")),
+				tok(n.Rparen, len(")")))
+		}
+
+	case *ast.GoStmt:
+		children = append(children,
+			tok(n.Go, len("go")))
+
+	case *ast.Ident:
+		children = append(children,
+			tok(n.NamePos, len(n.Name)))
+
+	case *ast.IfStmt:
+		children = append(children,
+			tok(n.If, len("if")))
+
+	case *ast.ImportSpec:
+		// TODO(adonovan): ImportSpec.{Doc,EndPos}?
+
+	case *ast.IncDecStmt:
+		children = append(children,
+			tok(n.TokPos, len(n.Tok.String())))
+
+	case *ast.IndexExpr:
+		children = append(children,
+			tok(n.Lbrack, len("[")),
+			tok(n.Rbrack, len("]")))
+
+	case *ast.IndexListExpr:
+		children = append(children,
+			tok(n.Lbrack, len("[")),
+			tok(n.Rbrack, len("]")))
+
+	case *ast.InterfaceType:
+		children = append(children,
+			tok(n.Interface, len("interface")))
+
+	case *ast.KeyValueExpr:
+		children = append(children,
+			tok(n.Colon, len(":")))
+
+	case *ast.LabeledStmt:
+		children = append(children,
+			tok(n.Colon, len(":")))
+
+	case *ast.MapType:
+		children = append(children,
+			tok(n.Map, len("map")))
+
+	case *ast.ParenExpr:
+		children = append(children,
+			tok(n.Lparen, len("(")),
+			tok(n.Rparen, len(")")))
+
+	case *ast.RangeStmt:
+		children = append(children,
+			tok(n.For, len("for")),
+			tok(n.TokPos, len(n.Tok.String())))
+
+	case *ast.ReturnStmt:
+		children = append(children,
+			tok(n.Return, len("return")))
+
+	case *ast.SelectStmt:
+		children = append(children,
+			tok(n.Select, len("select")))
+
+	case *ast.SelectorExpr:
+		// nop
+
+	case *ast.SendStmt:
+		children = append(children,
+			tok(n.Arrow, len("<-")))
+
+	case *ast.SliceExpr:
+		children = append(children,
+			tok(n.Lbrack, len("[")),
+			tok(n.Rbrack, len("]")))
+
+	case *ast.StarExpr:
+		children = append(children, tok(n.Star, len("*")))
+
+	case *ast.StructType:
+		children = append(children, tok(n.Struct, len("struct")))
+
+	case *ast.SwitchStmt:
+		children = append(children, tok(n.Switch, len("switch")))
+
+	case *ast.TypeAssertExpr:
+		children = append(children,
+			tok(n.Lparen-1, len(".")),
+			tok(n.Lparen, len("(")),
+			tok(n.Rparen, len(")")))
+
+	case *ast.TypeSpec:
+		// TODO(adonovan): TypeSpec.{Doc,Comment}?
+
+	case *ast.TypeSwitchStmt:
+		children = append(children, tok(n.Switch, len("switch")))
+
+	case *ast.UnaryExpr:
+		children = append(children, tok(n.OpPos, len(n.Op.String())))
+
+	case *ast.ValueSpec:
+		// TODO(adonovan): ValueSpec.{Doc,Comment}?
+
+	case *ast.BadDecl, *ast.BadExpr, *ast.BadStmt:
+		// nop
+	}
+
+	// TODO(adonovan): opt: merge the logic of ast.Inspect() into
+	// the switch above so we can make interleaved callbacks for
+	// both Nodes and Tokens in the right order and avoid the need
+	// to sort.
+	sort.Sort(byPos(children))
+
+	return children
+}
+
+type byPos []ast.Node
+
+func (sl byPos) Len() int {
+	return len(sl)
+}
+func (sl byPos) Less(i, j int) bool {
+	return sl[i].Pos() < sl[j].Pos()
+}
+func (sl byPos) Swap(i, j int) {
+	sl[i], sl[j] = sl[j], sl[i]
+}
+
+// NodeDescription returns a description of the concrete type of n suitable
+// for a user interface.
+//
+// TODO(adonovan): in some cases (e.g. Field, FieldList, Ident,
+// StarExpr) we could be much more specific given the path to the AST
+// root.  Perhaps we should do that.
+func NodeDescription(n ast.Node) string {
+	switch n := n.(type) {
+	case *ast.ArrayType:
+		return "array type"
+	case *ast.AssignStmt:
+		return "assignment"
+	case *ast.BadDecl:
+		return "bad declaration"
+	case *ast.BadExpr:
+		return "bad expression"
+	case *ast.BadStmt:
+		return "bad statement"
+	case *ast.BasicLit:
+		return "basic literal"
+	case *ast.BinaryExpr:
+		return fmt.Sprintf("binary %s operation", n.Op)
+	case *ast.BlockStmt:
+		return "block"
+	case *ast.BranchStmt:
+		switch n.Tok {
+		case token.BREAK:
+			return "break statement"
+		case token.CONTINUE:
+			return "continue statement"
+		case token.GOTO:
+			return "goto statement"
+		case token.FALLTHROUGH:
+			return "fall-through statement"
+		}
+	case *ast.CallExpr:
+		if len(n.Args) == 1 && !n.Ellipsis.IsValid() {
+			return "function call (or conversion)"
+		}
+		return "function call"
+	case *ast.CaseClause:
+		return "case clause"
+	case *ast.ChanType:
+		return "channel type"
+	case *ast.CommClause:
+		return "communication clause"
+	case *ast.Comment:
+		return "comment"
+	case *ast.CommentGroup:
+		return "comment group"
+	case *ast.CompositeLit:
+		return "composite literal"
+	case *ast.DeclStmt:
+		return NodeDescription(n.Decl) + " statement"
+	case *ast.DeferStmt:
+		return "defer statement"
+	case *ast.Ellipsis:
+		return "ellipsis"
+	case *ast.EmptyStmt:
+		return "empty statement"
+	case *ast.ExprStmt:
+		return "expression statement"
+	case *ast.Field:
+		// Can be any of these:
+		// struct {x, y int}  -- struct field(s)
+		// struct {T}         -- anon struct field
+		// interface {I}      -- interface embedding
+		// interface {f()}    -- interface method
+		// func (A) func(B) C -- receiver, param(s), result(s)
+		return "field/method/parameter"
+	case *ast.FieldList:
+		return "field/method/parameter list"
+	case *ast.File:
+		return "source file"
+	case *ast.ForStmt:
+		return "for loop"
+	case *ast.FuncDecl:
+		return "function declaration"
+	case *ast.FuncLit:
+		return "function literal"
+	case *ast.FuncType:
+		return "function type"
+	case *ast.GenDecl:
+		switch n.Tok {
+		case token.IMPORT:
+			return "import declaration"
+		case token.CONST:
+			return "constant declaration"
+		case token.TYPE:
+			return "type declaration"
+		case token.VAR:
+			return "variable declaration"
+		}
+	case *ast.GoStmt:
+		return "go statement"
+	case *ast.Ident:
+		return "identifier"
+	case *ast.IfStmt:
+		return "if statement"
+	case *ast.ImportSpec:
+		return "import specification"
+	case *ast.IncDecStmt:
+		if n.Tok == token.INC {
+			return "increment statement"
+		}
+		return "decrement statement"
+	case *ast.IndexExpr:
+		return "index expression"
+	case *ast.IndexListExpr:
+		return "index list expression"
+	case *ast.InterfaceType:
+		return "interface type"
+	case *ast.KeyValueExpr:
+		return "key/value association"
+	case *ast.LabeledStmt:
+		return "statement label"
+	case *ast.MapType:
+		return "map type"
+	case *ast.Package:
+		return "package"
+	case *ast.ParenExpr:
+		return "parenthesized " + NodeDescription(n.X)
+	case *ast.RangeStmt:
+		return "range loop"
+	case *ast.ReturnStmt:
+		return "return statement"
+	case *ast.SelectStmt:
+		return "select statement"
+	case *ast.SelectorExpr:
+		return "selector"
+	case *ast.SendStmt:
+		return "channel send"
+	case *ast.SliceExpr:
+		return "slice expression"
+	case *ast.StarExpr:
+		return "*-operation" // load/store expr or pointer type
+	case *ast.StructType:
+		return "struct type"
+	case *ast.SwitchStmt:
+		return "switch statement"
+	case *ast.TypeAssertExpr:
+		return "type assertion"
+	case *ast.TypeSpec:
+		return "type specification"
+	case *ast.TypeSwitchStmt:
+		return "type switch"
+	case *ast.UnaryExpr:
+		return fmt.Sprintf("unary %s operation", n.Op)
+	case *ast.ValueSpec:
+		return "value specification"
+
+	}
+	panic(fmt.Sprintf("unexpected node type: %T", n))
+}
+
+func is[T any](x any) bool {
+	_, ok := x.(T)
+	return ok
+}
diff --git a/vendor/golang.org/x/tools/go/ast/astutil/imports.go b/vendor/golang.org/x/tools/go/ast/astutil/imports.go
new file mode 100644
index 0000000..18d1adb
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ast/astutil/imports.go
@@ -0,0 +1,485 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package astutil contains common utilities for working with the Go AST.
+package astutil // import "golang.org/x/tools/go/ast/astutil"
+
+import (
+	"fmt"
+	"go/ast"
+	"go/token"
+	"strconv"
+	"strings"
+)
+
+// AddImport adds the import path to the file f, if absent.
+func AddImport(fset *token.FileSet, f *ast.File, path string) (added bool) {
+	return AddNamedImport(fset, f, "", path)
+}
+
+// AddNamedImport adds the import with the given name and path to the file f, if absent.
+// If name is not empty, it is used to rename the import.
+//
+// For example, calling
+//
+//	AddNamedImport(fset, f, "pathpkg", "path")
+//
+// adds
+//
+//	import pathpkg "path"
+func AddNamedImport(fset *token.FileSet, f *ast.File, name, path string) (added bool) {
+	if imports(f, name, path) {
+		return false
+	}
+
+	newImport := &ast.ImportSpec{
+		Path: &ast.BasicLit{
+			Kind:  token.STRING,
+			Value: strconv.Quote(path),
+		},
+	}
+	if name != "" {
+		newImport.Name = &ast.Ident{Name: name}
+	}
+
+	// Find an import decl to add to.
+	// The goal is to find an existing import
+	// whose import path has the longest shared
+	// prefix with path.
+	var (
+		bestMatch  = -1         // length of longest shared prefix
+		lastImport = -1         // index in f.Decls of the file's final import decl
+		impDecl    *ast.GenDecl // import decl containing the best match
+		impIndex   = -1         // spec index in impDecl containing the best match
+
+		isThirdPartyPath = isThirdParty(path)
+	)
+	for i, decl := range f.Decls {
+		gen, ok := decl.(*ast.GenDecl)
+		if ok && gen.Tok == token.IMPORT {
+			lastImport = i
+			// Do not add to import "C", to avoid disrupting the
+			// association with its doc comment, breaking cgo.
+			if declImports(gen, "C") {
+				continue
+			}
+
+			// Match an empty import decl if that's all that is available.
+			if len(gen.Specs) == 0 && bestMatch == -1 {
+				impDecl = gen
+			}
+
+			// Compute longest shared prefix with imports in this group and find best
+			// matched import spec.
+			// 1. Always prefer import spec with longest shared prefix.
+			// 2. While match length is 0,
+			// - for stdlib package: prefer first import spec.
+			// - for third party package: prefer first third party import spec.
+			// We cannot use last import spec as best match for third party package
+			// because grouped imports are usually placed last by goimports -local
+			// flag.
+			// See issue #19190.
+			seenAnyThirdParty := false
+			for j, spec := range gen.Specs {
+				impspec := spec.(*ast.ImportSpec)
+				p := importPath(impspec)
+				n := matchLen(p, path)
+				if n > bestMatch || (bestMatch == 0 && !seenAnyThirdParty && isThirdPartyPath) {
+					bestMatch = n
+					impDecl = gen
+					impIndex = j
+				}
+				seenAnyThirdParty = seenAnyThirdParty || isThirdParty(p)
+			}
+		}
+	}
+
+	// If no import decl found, add one after the last import.
+	if impDecl == nil {
+		impDecl = &ast.GenDecl{
+			Tok: token.IMPORT,
+		}
+		if lastImport >= 0 {
+			impDecl.TokPos = f.Decls[lastImport].End()
+		} else {
+			// There are no existing imports.
+			// Our new import, preceded by a blank line,  goes after the package declaration
+			// and after the comment, if any, that starts on the same line as the
+			// package declaration.
+			impDecl.TokPos = f.Package
+
+			file := fset.File(f.Package)
+			pkgLine := file.Line(f.Package)
+			for _, c := range f.Comments {
+				if file.Line(c.Pos()) > pkgLine {
+					break
+				}
+				// +2 for a blank line
+				impDecl.TokPos = c.End() + 2
+			}
+		}
+		f.Decls = append(f.Decls, nil)
+		copy(f.Decls[lastImport+2:], f.Decls[lastImport+1:])
+		f.Decls[lastImport+1] = impDecl
+	}
+
+	// Insert new import at insertAt.
+	insertAt := 0
+	if impIndex >= 0 {
+		// insert after the found import
+		insertAt = impIndex + 1
+	}
+	impDecl.Specs = append(impDecl.Specs, nil)
+	copy(impDecl.Specs[insertAt+1:], impDecl.Specs[insertAt:])
+	impDecl.Specs[insertAt] = newImport
+	pos := impDecl.Pos()
+	if insertAt > 0 {
+		// If there is a comment after an existing import, preserve the comment
+		// position by adding the new import after the comment.
+		if spec, ok := impDecl.Specs[insertAt-1].(*ast.ImportSpec); ok && spec.Comment != nil {
+			pos = spec.Comment.End()
+		} else {
+			// Assign same position as the previous import,
+			// so that the sorter sees it as being in the same block.
+			pos = impDecl.Specs[insertAt-1].Pos()
+		}
+	}
+	if newImport.Name != nil {
+		newImport.Name.NamePos = pos
+	}
+	newImport.Path.ValuePos = pos
+	newImport.EndPos = pos
+
+	// Clean up parens. impDecl contains at least one spec.
+	if len(impDecl.Specs) == 1 {
+		// Remove unneeded parens.
+		impDecl.Lparen = token.NoPos
+	} else if !impDecl.Lparen.IsValid() {
+		// impDecl needs parens added.
+		impDecl.Lparen = impDecl.Specs[0].Pos()
+	}
+
+	f.Imports = append(f.Imports, newImport)
+
+	if len(f.Decls) <= 1 {
+		return true
+	}
+
+	// Merge all the import declarations into the first one.
+	var first *ast.GenDecl
+	for i := 0; i < len(f.Decls); i++ {
+		decl := f.Decls[i]
+		gen, ok := decl.(*ast.GenDecl)
+		if !ok || gen.Tok != token.IMPORT || declImports(gen, "C") {
+			continue
+		}
+		if first == nil {
+			first = gen
+			continue // Don't touch the first one.
+		}
+		// We now know there is more than one package in this import
+		// declaration. Ensure that it ends up parenthesized.
+		first.Lparen = first.Pos()
+		// Move the imports of the other import declaration to the first one.
+		for _, spec := range gen.Specs {
+			spec.(*ast.ImportSpec).Path.ValuePos = first.Pos()
+			first.Specs = append(first.Specs, spec)
+		}
+		f.Decls = append(f.Decls[:i], f.Decls[i+1:]...)
+		i--
+	}
+
+	return true
+}
+
+func isThirdParty(importPath string) bool {
+	// Third party package import path usually contains "." (".com", ".org", ...)
+	// This logic is taken from golang.org/x/tools/imports package.
+	return strings.Contains(importPath, ".")
+}
+
+// DeleteImport deletes the import path from the file f, if present.
+// If there are duplicate import declarations, all matching ones are deleted.
+func DeleteImport(fset *token.FileSet, f *ast.File, path string) (deleted bool) {
+	return DeleteNamedImport(fset, f, "", path)
+}
+
+// DeleteNamedImport deletes the import with the given name and path from the file f, if present.
+// If there are duplicate import declarations, all matching ones are deleted.
+func DeleteNamedImport(fset *token.FileSet, f *ast.File, name, path string) (deleted bool) {
+	var delspecs []*ast.ImportSpec
+	var delcomments []*ast.CommentGroup
+
+	// Find the import nodes that import path, if any.
+	for i := 0; i < len(f.Decls); i++ {
+		decl := f.Decls[i]
+		gen, ok := decl.(*ast.GenDecl)
+		if !ok || gen.Tok != token.IMPORT {
+			continue
+		}
+		for j := 0; j < len(gen.Specs); j++ {
+			spec := gen.Specs[j]
+			impspec := spec.(*ast.ImportSpec)
+			if importName(impspec) != name || importPath(impspec) != path {
+				continue
+			}
+
+			// We found an import spec that imports path.
+			// Delete it.
+			delspecs = append(delspecs, impspec)
+			deleted = true
+			copy(gen.Specs[j:], gen.Specs[j+1:])
+			gen.Specs = gen.Specs[:len(gen.Specs)-1]
+
+			// If this was the last import spec in this decl,
+			// delete the decl, too.
+			if len(gen.Specs) == 0 {
+				copy(f.Decls[i:], f.Decls[i+1:])
+				f.Decls = f.Decls[:len(f.Decls)-1]
+				i--
+				break
+			} else if len(gen.Specs) == 1 {
+				if impspec.Doc != nil {
+					delcomments = append(delcomments, impspec.Doc)
+				}
+				if impspec.Comment != nil {
+					delcomments = append(delcomments, impspec.Comment)
+				}
+				for _, cg := range f.Comments {
+					// Found comment on the same line as the import spec.
+					if cg.End() < impspec.Pos() && fset.Position(cg.End()).Line == fset.Position(impspec.Pos()).Line {
+						delcomments = append(delcomments, cg)
+						break
+					}
+				}
+
+				spec := gen.Specs[0].(*ast.ImportSpec)
+
+				// Move the documentation right after the import decl.
+				if spec.Doc != nil {
+					for fset.Position(gen.TokPos).Line+1 < fset.Position(spec.Doc.Pos()).Line {
+						fset.File(gen.TokPos).MergeLine(fset.Position(gen.TokPos).Line)
+					}
+				}
+				for _, cg := range f.Comments {
+					if cg.End() < spec.Pos() && fset.Position(cg.End()).Line == fset.Position(spec.Pos()).Line {
+						for fset.Position(gen.TokPos).Line+1 < fset.Position(spec.Pos()).Line {
+							fset.File(gen.TokPos).MergeLine(fset.Position(gen.TokPos).Line)
+						}
+						break
+					}
+				}
+			}
+			if j > 0 {
+				lastImpspec := gen.Specs[j-1].(*ast.ImportSpec)
+				lastLine := fset.PositionFor(lastImpspec.Path.ValuePos, false).Line
+				line := fset.PositionFor(impspec.Path.ValuePos, false).Line
+
+				// We deleted an entry but now there may be
+				// a blank line-sized hole where the import was.
+				if line-lastLine > 1 || !gen.Rparen.IsValid() {
+					// There was a blank line immediately preceding the deleted import,
+					// so there's no need to close the hole. The right parenthesis is
+					// invalid after AddImport to an import statement without parenthesis.
+					// Do nothing.
+				} else if line != fset.File(gen.Rparen).LineCount() {
+					// There was no blank line. Close the hole.
+					fset.File(gen.Rparen).MergeLine(line)
+				}
+			}
+			j--
+		}
+	}
+
+	// Delete imports from f.Imports.
+	for i := 0; i < len(f.Imports); i++ {
+		imp := f.Imports[i]
+		for j, del := range delspecs {
+			if imp == del {
+				copy(f.Imports[i:], f.Imports[i+1:])
+				f.Imports = f.Imports[:len(f.Imports)-1]
+				copy(delspecs[j:], delspecs[j+1:])
+				delspecs = delspecs[:len(delspecs)-1]
+				i--
+				break
+			}
+		}
+	}
+
+	// Delete comments from f.Comments.
+	for i := 0; i < len(f.Comments); i++ {
+		cg := f.Comments[i]
+		for j, del := range delcomments {
+			if cg == del {
+				copy(f.Comments[i:], f.Comments[i+1:])
+				f.Comments = f.Comments[:len(f.Comments)-1]
+				copy(delcomments[j:], delcomments[j+1:])
+				delcomments = delcomments[:len(delcomments)-1]
+				i--
+				break
+			}
+		}
+	}
+
+	if len(delspecs) > 0 {
+		panic(fmt.Sprintf("deleted specs from Decls but not Imports: %v", delspecs))
+	}
+
+	return
+}
+
+// RewriteImport rewrites any import of path oldPath to path newPath.
+func RewriteImport(fset *token.FileSet, f *ast.File, oldPath, newPath string) (rewrote bool) {
+	for _, imp := range f.Imports {
+		if importPath(imp) == oldPath {
+			rewrote = true
+			// record old End, because the default is to compute
+			// it using the length of imp.Path.Value.
+			imp.EndPos = imp.End()
+			imp.Path.Value = strconv.Quote(newPath)
+		}
+	}
+	return
+}
+
+// UsesImport reports whether a given import is used.
+func UsesImport(f *ast.File, path string) (used bool) {
+	spec := importSpec(f, path)
+	if spec == nil {
+		return
+	}
+
+	name := spec.Name.String()
+	switch name {
+	case "<nil>":
+		// If the package name is not explicitly specified,
+		// make an educated guess. This is not guaranteed to be correct.
+		lastSlash := strings.LastIndex(path, "/")
+		if lastSlash == -1 {
+			name = path
+		} else {
+			name = path[lastSlash+1:]
+		}
+	case "_", ".":
+		// Not sure if this import is used - err on the side of caution.
+		return true
+	}
+
+	ast.Walk(visitFn(func(n ast.Node) {
+		sel, ok := n.(*ast.SelectorExpr)
+		if ok && isTopName(sel.X, name) {
+			used = true
+		}
+	}), f)
+
+	return
+}
+
+type visitFn func(node ast.Node)
+
+func (fn visitFn) Visit(node ast.Node) ast.Visitor {
+	fn(node)
+	return fn
+}
+
+// imports reports whether f has an import with the specified name and path.
+func imports(f *ast.File, name, path string) bool {
+	for _, s := range f.Imports {
+		if importName(s) == name && importPath(s) == path {
+			return true
+		}
+	}
+	return false
+}
+
+// importSpec returns the import spec if f imports path,
+// or nil otherwise.
+func importSpec(f *ast.File, path string) *ast.ImportSpec {
+	for _, s := range f.Imports {
+		if importPath(s) == path {
+			return s
+		}
+	}
+	return nil
+}
+
+// importName returns the name of s,
+// or "" if the import is not named.
+func importName(s *ast.ImportSpec) string {
+	if s.Name == nil {
+		return ""
+	}
+	return s.Name.Name
+}
+
+// importPath returns the unquoted import path of s,
+// or "" if the path is not properly quoted.
+func importPath(s *ast.ImportSpec) string {
+	t, err := strconv.Unquote(s.Path.Value)
+	if err != nil {
+		return ""
+	}
+	return t
+}
+
+// declImports reports whether gen contains an import of path.
+func declImports(gen *ast.GenDecl, path string) bool {
+	if gen.Tok != token.IMPORT {
+		return false
+	}
+	for _, spec := range gen.Specs {
+		impspec := spec.(*ast.ImportSpec)
+		if importPath(impspec) == path {
+			return true
+		}
+	}
+	return false
+}
+
+// matchLen returns the length of the longest path segment prefix shared by x and y.
+func matchLen(x, y string) int {
+	n := 0
+	for i := 0; i < len(x) && i < len(y) && x[i] == y[i]; i++ {
+		if x[i] == '/' {
+			n++
+		}
+	}
+	return n
+}
+
+// isTopName returns true if n is a top-level unresolved identifier with the given name.
+func isTopName(n ast.Expr, name string) bool {
+	id, ok := n.(*ast.Ident)
+	return ok && id.Name == name && id.Obj == nil
+}
+
+// Imports returns the file imports grouped by paragraph.
+func Imports(fset *token.FileSet, f *ast.File) [][]*ast.ImportSpec {
+	var groups [][]*ast.ImportSpec
+
+	for _, decl := range f.Decls {
+		genDecl, ok := decl.(*ast.GenDecl)
+		if !ok || genDecl.Tok != token.IMPORT {
+			break
+		}
+
+		group := []*ast.ImportSpec{}
+
+		var lastLine int
+		for _, spec := range genDecl.Specs {
+			importSpec := spec.(*ast.ImportSpec)
+			pos := importSpec.Path.ValuePos
+			line := fset.Position(pos).Line
+			if lastLine > 0 && pos > 0 && line-lastLine > 1 {
+				groups = append(groups, group)
+				group = []*ast.ImportSpec{}
+			}
+			group = append(group, importSpec)
+			lastLine = line
+		}
+		groups = append(groups, group)
+	}
+
+	return groups
+}
diff --git a/vendor/golang.org/x/tools/go/ast/astutil/rewrite.go b/vendor/golang.org/x/tools/go/ast/astutil/rewrite.go
new file mode 100644
index 0000000..58934f7
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ast/astutil/rewrite.go
@@ -0,0 +1,486 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package astutil
+
+import (
+	"fmt"
+	"go/ast"
+	"reflect"
+	"sort"
+)
+
+// An ApplyFunc is invoked by Apply for each node n, even if n is nil,
+// before and/or after the node's children, using a Cursor describing
+// the current node and providing operations on it.
+//
+// The return value of ApplyFunc controls the syntax tree traversal.
+// See Apply for details.
+type ApplyFunc func(*Cursor) bool
+
+// Apply traverses a syntax tree recursively, starting with root,
+// and calling pre and post for each node as described below.
+// Apply returns the syntax tree, possibly modified.
+//
+// If pre is not nil, it is called for each node before the node's
+// children are traversed (pre-order). If pre returns false, no
+// children are traversed, and post is not called for that node.
+//
+// If post is not nil, and a prior call of pre didn't return false,
+// post is called for each node after its children are traversed
+// (post-order). If post returns false, traversal is terminated and
+// Apply returns immediately.
+//
+// Only fields that refer to AST nodes are considered children;
+// i.e., token.Pos, Scopes, Objects, and fields of basic types
+// (strings, etc.) are ignored.
+//
+// Children are traversed in the order in which they appear in the
+// respective node's struct definition. A package's files are
+// traversed in the filenames' alphabetical order.
+func Apply(root ast.Node, pre, post ApplyFunc) (result ast.Node) {
+	parent := &struct{ ast.Node }{root}
+	defer func() {
+		if r := recover(); r != nil && r != abort {
+			panic(r)
+		}
+		result = parent.Node
+	}()
+	a := &application{pre: pre, post: post}
+	a.apply(parent, "Node", nil, root)
+	return
+}
+
+var abort = new(int) // singleton, to signal termination of Apply
+
+// A Cursor describes a node encountered during Apply.
+// Information about the node and its parent is available
+// from the Node, Parent, Name, and Index methods.
+//
+// If p is a variable of type and value of the current parent node
+// c.Parent(), and f is the field identifier with name c.Name(),
+// the following invariants hold:
+//
+//	p.f            == c.Node()  if c.Index() <  0
+//	p.f[c.Index()] == c.Node()  if c.Index() >= 0
+//
+// The methods Replace, Delete, InsertBefore, and InsertAfter
+// can be used to change the AST without disrupting Apply.
+type Cursor struct {
+	parent ast.Node
+	name   string
+	iter   *iterator // valid if non-nil
+	node   ast.Node
+}
+
+// Node returns the current Node.
+func (c *Cursor) Node() ast.Node { return c.node }
+
+// Parent returns the parent of the current Node.
+func (c *Cursor) Parent() ast.Node { return c.parent }
+
+// Name returns the name of the parent Node field that contains the current Node.
+// If the parent is a *ast.Package and the current Node is a *ast.File, Name returns
+// the filename for the current Node.
+func (c *Cursor) Name() string { return c.name }
+
+// Index reports the index >= 0 of the current Node in the slice of Nodes that
+// contains it, or a value < 0 if the current Node is not part of a slice.
+// The index of the current node changes if InsertBefore is called while
+// processing the current node.
+func (c *Cursor) Index() int {
+	if c.iter != nil {
+		return c.iter.index
+	}
+	return -1
+}
+
+// field returns the current node's parent field value.
+func (c *Cursor) field() reflect.Value {
+	return reflect.Indirect(reflect.ValueOf(c.parent)).FieldByName(c.name)
+}
+
+// Replace replaces the current Node with n.
+// The replacement node is not walked by Apply.
+func (c *Cursor) Replace(n ast.Node) {
+	if _, ok := c.node.(*ast.File); ok {
+		file, ok := n.(*ast.File)
+		if !ok {
+			panic("attempt to replace *ast.File with non-*ast.File")
+		}
+		c.parent.(*ast.Package).Files[c.name] = file
+		return
+	}
+
+	v := c.field()
+	if i := c.Index(); i >= 0 {
+		v = v.Index(i)
+	}
+	v.Set(reflect.ValueOf(n))
+}
+
+// Delete deletes the current Node from its containing slice.
+// If the current Node is not part of a slice, Delete panics.
+// As a special case, if the current node is a package file,
+// Delete removes it from the package's Files map.
+func (c *Cursor) Delete() {
+	if _, ok := c.node.(*ast.File); ok {
+		delete(c.parent.(*ast.Package).Files, c.name)
+		return
+	}
+
+	i := c.Index()
+	if i < 0 {
+		panic("Delete node not contained in slice")
+	}
+	v := c.field()
+	l := v.Len()
+	reflect.Copy(v.Slice(i, l), v.Slice(i+1, l))
+	v.Index(l - 1).Set(reflect.Zero(v.Type().Elem()))
+	v.SetLen(l - 1)
+	c.iter.step--
+}
+
+// InsertAfter inserts n after the current Node in its containing slice.
+// If the current Node is not part of a slice, InsertAfter panics.
+// Apply does not walk n.
+func (c *Cursor) InsertAfter(n ast.Node) {
+	i := c.Index()
+	if i < 0 {
+		panic("InsertAfter node not contained in slice")
+	}
+	v := c.field()
+	v.Set(reflect.Append(v, reflect.Zero(v.Type().Elem())))
+	l := v.Len()
+	reflect.Copy(v.Slice(i+2, l), v.Slice(i+1, l))
+	v.Index(i + 1).Set(reflect.ValueOf(n))
+	c.iter.step++
+}
+
+// InsertBefore inserts n before the current Node in its containing slice.
+// If the current Node is not part of a slice, InsertBefore panics.
+// Apply will not walk n.
+func (c *Cursor) InsertBefore(n ast.Node) {
+	i := c.Index()
+	if i < 0 {
+		panic("InsertBefore node not contained in slice")
+	}
+	v := c.field()
+	v.Set(reflect.Append(v, reflect.Zero(v.Type().Elem())))
+	l := v.Len()
+	reflect.Copy(v.Slice(i+1, l), v.Slice(i, l))
+	v.Index(i).Set(reflect.ValueOf(n))
+	c.iter.index++
+}
+
+// application carries all the shared data so we can pass it around cheaply.
+type application struct {
+	pre, post ApplyFunc
+	cursor    Cursor
+	iter      iterator
+}
+
+func (a *application) apply(parent ast.Node, name string, iter *iterator, n ast.Node) {
+	// convert typed nil into untyped nil
+	if v := reflect.ValueOf(n); v.Kind() == reflect.Ptr && v.IsNil() {
+		n = nil
+	}
+
+	// avoid heap-allocating a new cursor for each apply call; reuse a.cursor instead
+	saved := a.cursor
+	a.cursor.parent = parent
+	a.cursor.name = name
+	a.cursor.iter = iter
+	a.cursor.node = n
+
+	if a.pre != nil && !a.pre(&a.cursor) {
+		a.cursor = saved
+		return
+	}
+
+	// walk children
+	// (the order of the cases matches the order of the corresponding node types in go/ast)
+	switch n := n.(type) {
+	case nil:
+		// nothing to do
+
+	// Comments and fields
+	case *ast.Comment:
+		// nothing to do
+
+	case *ast.CommentGroup:
+		if n != nil {
+			a.applyList(n, "List")
+		}
+
+	case *ast.Field:
+		a.apply(n, "Doc", nil, n.Doc)
+		a.applyList(n, "Names")
+		a.apply(n, "Type", nil, n.Type)
+		a.apply(n, "Tag", nil, n.Tag)
+		a.apply(n, "Comment", nil, n.Comment)
+
+	case *ast.FieldList:
+		a.applyList(n, "List")
+
+	// Expressions
+	case *ast.BadExpr, *ast.Ident, *ast.BasicLit:
+		// nothing to do
+
+	case *ast.Ellipsis:
+		a.apply(n, "Elt", nil, n.Elt)
+
+	case *ast.FuncLit:
+		a.apply(n, "Type", nil, n.Type)
+		a.apply(n, "Body", nil, n.Body)
+
+	case *ast.CompositeLit:
+		a.apply(n, "Type", nil, n.Type)
+		a.applyList(n, "Elts")
+
+	case *ast.ParenExpr:
+		a.apply(n, "X", nil, n.X)
+
+	case *ast.SelectorExpr:
+		a.apply(n, "X", nil, n.X)
+		a.apply(n, "Sel", nil, n.Sel)
+
+	case *ast.IndexExpr:
+		a.apply(n, "X", nil, n.X)
+		a.apply(n, "Index", nil, n.Index)
+
+	case *ast.IndexListExpr:
+		a.apply(n, "X", nil, n.X)
+		a.applyList(n, "Indices")
+
+	case *ast.SliceExpr:
+		a.apply(n, "X", nil, n.X)
+		a.apply(n, "Low", nil, n.Low)
+		a.apply(n, "High", nil, n.High)
+		a.apply(n, "Max", nil, n.Max)
+
+	case *ast.TypeAssertExpr:
+		a.apply(n, "X", nil, n.X)
+		a.apply(n, "Type", nil, n.Type)
+
+	case *ast.CallExpr:
+		a.apply(n, "Fun", nil, n.Fun)
+		a.applyList(n, "Args")
+
+	case *ast.StarExpr:
+		a.apply(n, "X", nil, n.X)
+
+	case *ast.UnaryExpr:
+		a.apply(n, "X", nil, n.X)
+
+	case *ast.BinaryExpr:
+		a.apply(n, "X", nil, n.X)
+		a.apply(n, "Y", nil, n.Y)
+
+	case *ast.KeyValueExpr:
+		a.apply(n, "Key", nil, n.Key)
+		a.apply(n, "Value", nil, n.Value)
+
+	// Types
+	case *ast.ArrayType:
+		a.apply(n, "Len", nil, n.Len)
+		a.apply(n, "Elt", nil, n.Elt)
+
+	case *ast.StructType:
+		a.apply(n, "Fields", nil, n.Fields)
+
+	case *ast.FuncType:
+		if tparams := n.TypeParams; tparams != nil {
+			a.apply(n, "TypeParams", nil, tparams)
+		}
+		a.apply(n, "Params", nil, n.Params)
+		a.apply(n, "Results", nil, n.Results)
+
+	case *ast.InterfaceType:
+		a.apply(n, "Methods", nil, n.Methods)
+
+	case *ast.MapType:
+		a.apply(n, "Key", nil, n.Key)
+		a.apply(n, "Value", nil, n.Value)
+
+	case *ast.ChanType:
+		a.apply(n, "Value", nil, n.Value)
+
+	// Statements
+	case *ast.BadStmt:
+		// nothing to do
+
+	case *ast.DeclStmt:
+		a.apply(n, "Decl", nil, n.Decl)
+
+	case *ast.EmptyStmt:
+		// nothing to do
+
+	case *ast.LabeledStmt:
+		a.apply(n, "Label", nil, n.Label)
+		a.apply(n, "Stmt", nil, n.Stmt)
+
+	case *ast.ExprStmt:
+		a.apply(n, "X", nil, n.X)
+
+	case *ast.SendStmt:
+		a.apply(n, "Chan", nil, n.Chan)
+		a.apply(n, "Value", nil, n.Value)
+
+	case *ast.IncDecStmt:
+		a.apply(n, "X", nil, n.X)
+
+	case *ast.AssignStmt:
+		a.applyList(n, "Lhs")
+		a.applyList(n, "Rhs")
+
+	case *ast.GoStmt:
+		a.apply(n, "Call", nil, n.Call)
+
+	case *ast.DeferStmt:
+		a.apply(n, "Call", nil, n.Call)
+
+	case *ast.ReturnStmt:
+		a.applyList(n, "Results")
+
+	case *ast.BranchStmt:
+		a.apply(n, "Label", nil, n.Label)
+
+	case *ast.BlockStmt:
+		a.applyList(n, "List")
+
+	case *ast.IfStmt:
+		a.apply(n, "Init", nil, n.Init)
+		a.apply(n, "Cond", nil, n.Cond)
+		a.apply(n, "Body", nil, n.Body)
+		a.apply(n, "Else", nil, n.Else)
+
+	case *ast.CaseClause:
+		a.applyList(n, "List")
+		a.applyList(n, "Body")
+
+	case *ast.SwitchStmt:
+		a.apply(n, "Init", nil, n.Init)
+		a.apply(n, "Tag", nil, n.Tag)
+		a.apply(n, "Body", nil, n.Body)
+
+	case *ast.TypeSwitchStmt:
+		a.apply(n, "Init", nil, n.Init)
+		a.apply(n, "Assign", nil, n.Assign)
+		a.apply(n, "Body", nil, n.Body)
+
+	case *ast.CommClause:
+		a.apply(n, "Comm", nil, n.Comm)
+		a.applyList(n, "Body")
+
+	case *ast.SelectStmt:
+		a.apply(n, "Body", nil, n.Body)
+
+	case *ast.ForStmt:
+		a.apply(n, "Init", nil, n.Init)
+		a.apply(n, "Cond", nil, n.Cond)
+		a.apply(n, "Post", nil, n.Post)
+		a.apply(n, "Body", nil, n.Body)
+
+	case *ast.RangeStmt:
+		a.apply(n, "Key", nil, n.Key)
+		a.apply(n, "Value", nil, n.Value)
+		a.apply(n, "X", nil, n.X)
+		a.apply(n, "Body", nil, n.Body)
+
+	// Declarations
+	case *ast.ImportSpec:
+		a.apply(n, "Doc", nil, n.Doc)
+		a.apply(n, "Name", nil, n.Name)
+		a.apply(n, "Path", nil, n.Path)
+		a.apply(n, "Comment", nil, n.Comment)
+
+	case *ast.ValueSpec:
+		a.apply(n, "Doc", nil, n.Doc)
+		a.applyList(n, "Names")
+		a.apply(n, "Type", nil, n.Type)
+		a.applyList(n, "Values")
+		a.apply(n, "Comment", nil, n.Comment)
+
+	case *ast.TypeSpec:
+		a.apply(n, "Doc", nil, n.Doc)
+		a.apply(n, "Name", nil, n.Name)
+		if tparams := n.TypeParams; tparams != nil {
+			a.apply(n, "TypeParams", nil, tparams)
+		}
+		a.apply(n, "Type", nil, n.Type)
+		a.apply(n, "Comment", nil, n.Comment)
+
+	case *ast.BadDecl:
+		// nothing to do
+
+	case *ast.GenDecl:
+		a.apply(n, "Doc", nil, n.Doc)
+		a.applyList(n, "Specs")
+
+	case *ast.FuncDecl:
+		a.apply(n, "Doc", nil, n.Doc)
+		a.apply(n, "Recv", nil, n.Recv)
+		a.apply(n, "Name", nil, n.Name)
+		a.apply(n, "Type", nil, n.Type)
+		a.apply(n, "Body", nil, n.Body)
+
+	// Files and packages
+	case *ast.File:
+		a.apply(n, "Doc", nil, n.Doc)
+		a.apply(n, "Name", nil, n.Name)
+		a.applyList(n, "Decls")
+		// Don't walk n.Comments; they have either been walked already if
+		// they are Doc comments, or they can be easily walked explicitly.
+
+	case *ast.Package:
+		// collect and sort names for reproducible behavior
+		var names []string
+		for name := range n.Files {
+			names = append(names, name)
+		}
+		sort.Strings(names)
+		for _, name := range names {
+			a.apply(n, name, nil, n.Files[name])
+		}
+
+	default:
+		panic(fmt.Sprintf("Apply: unexpected node type %T", n))
+	}
+
+	if a.post != nil && !a.post(&a.cursor) {
+		panic(abort)
+	}
+
+	a.cursor = saved
+}
+
+// An iterator controls iteration over a slice of nodes.
+type iterator struct {
+	index, step int
+}
+
+func (a *application) applyList(parent ast.Node, name string) {
+	// avoid heap-allocating a new iterator for each applyList call; reuse a.iter instead
+	saved := a.iter
+	a.iter.index = 0
+	for {
+		// must reload parent.name each time, since cursor modifications might change it
+		v := reflect.Indirect(reflect.ValueOf(parent)).FieldByName(name)
+		if a.iter.index >= v.Len() {
+			break
+		}
+
+		// element x may be nil in a bad AST - be cautious
+		var x ast.Node
+		if e := v.Index(a.iter.index); e.IsValid() {
+			x = e.Interface().(ast.Node)
+		}
+
+		a.iter.step = 1
+		a.apply(parent, name, &a.iter, x)
+		a.iter.index += a.iter.step
+	}
+	a.iter = saved
+}
diff --git a/vendor/golang.org/x/tools/go/ast/astutil/util.go b/vendor/golang.org/x/tools/go/ast/astutil/util.go
new file mode 100644
index 0000000..6bdcf70
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ast/astutil/util.go
@@ -0,0 +1,19 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package astutil
+
+import "go/ast"
+
+// Unparen returns e with any enclosing parentheses stripped.
+// TODO(adonovan): use go1.22's ast.Unparen.
+func Unparen(e ast.Expr) ast.Expr {
+	for {
+		p, ok := e.(*ast.ParenExpr)
+		if !ok {
+			return e
+		}
+		e = p.X
+	}
+}
diff --git a/vendor/golang.org/x/tools/go/buildutil/allpackages.go b/vendor/golang.org/x/tools/go/buildutil/allpackages.go
new file mode 100644
index 0000000..dfb8cd6
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/buildutil/allpackages.go
@@ -0,0 +1,195 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package buildutil provides utilities related to the go/build
+// package in the standard library.
+//
+// All I/O is done via the build.Context file system interface, which must
+// be concurrency-safe.
+package buildutil // import "golang.org/x/tools/go/buildutil"
+
+import (
+	"go/build"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+	"sync"
+)
+
+// AllPackages returns the package path of each Go package in any source
+// directory of the specified build context (e.g. $GOROOT or an element
+// of $GOPATH).  Errors are ignored.  The results are sorted.
+// All package paths are canonical, and thus may contain "/vendor/".
+//
+// The result may include import paths for directories that contain no
+// *.go files, such as "archive" (in $GOROOT/src).
+//
+// All I/O is done via the build.Context file system interface,
+// which must be concurrency-safe.
+func AllPackages(ctxt *build.Context) []string {
+	var list []string
+	ForEachPackage(ctxt, func(pkg string, _ error) {
+		list = append(list, pkg)
+	})
+	sort.Strings(list)
+	return list
+}
+
+// ForEachPackage calls the found function with the package path of
+// each Go package it finds in any source directory of the specified
+// build context (e.g. $GOROOT or an element of $GOPATH).
+// All package paths are canonical, and thus may contain "/vendor/".
+//
+// If the package directory exists but could not be read, the second
+// argument to the found function provides the error.
+//
+// All I/O is done via the build.Context file system interface,
+// which must be concurrency-safe.
+func ForEachPackage(ctxt *build.Context, found func(importPath string, err error)) {
+	ch := make(chan item)
+
+	var wg sync.WaitGroup
+	for _, root := range ctxt.SrcDirs() {
+		root := root
+		wg.Add(1)
+		go func() {
+			allPackages(ctxt, root, ch)
+			wg.Done()
+		}()
+	}
+	go func() {
+		wg.Wait()
+		close(ch)
+	}()
+
+	// All calls to found occur in the caller's goroutine.
+	for i := range ch {
+		found(i.importPath, i.err)
+	}
+}
+
+type item struct {
+	importPath string
+	err        error // (optional)
+}
+
+// We use a process-wide counting semaphore to limit
+// the number of parallel calls to ReadDir.
+var ioLimit = make(chan bool, 20)
+
+func allPackages(ctxt *build.Context, root string, ch chan<- item) {
+	root = filepath.Clean(root) + string(os.PathSeparator)
+
+	var wg sync.WaitGroup
+
+	var walkDir func(dir string)
+	walkDir = func(dir string) {
+		// Avoid .foo, _foo, and testdata directory trees.
+		base := filepath.Base(dir)
+		if base == "" || base[0] == '.' || base[0] == '_' || base == "testdata" {
+			return
+		}
+
+		pkg := filepath.ToSlash(strings.TrimPrefix(dir, root))
+
+		// Prune search if we encounter any of these import paths.
+		switch pkg {
+		case "builtin":
+			return
+		}
+
+		ioLimit <- true
+		files, err := ReadDir(ctxt, dir)
+		<-ioLimit
+		if pkg != "" || err != nil {
+			ch <- item{pkg, err}
+		}
+		for _, fi := range files {
+			fi := fi
+			if fi.IsDir() {
+				wg.Add(1)
+				go func() {
+					walkDir(filepath.Join(dir, fi.Name()))
+					wg.Done()
+				}()
+			}
+		}
+	}
+
+	walkDir(root)
+	wg.Wait()
+}
+
+// ExpandPatterns returns the set of packages matched by patterns,
+// which may have the following forms:
+//
+//	golang.org/x/tools/cmd/guru     # a single package
+//	golang.org/x/tools/...          # all packages beneath dir
+//	...                             # the entire workspace.
+//
+// Order is significant: a pattern preceded by '-' removes matching
+// packages from the set.  For example, these patterns match all encoding
+// packages except encoding/xml:
+//
+//	encoding/... -encoding/xml
+//
+// A trailing slash in a pattern is ignored.  (Path components of Go
+// package names are separated by slash, not the platform's path separator.)
+func ExpandPatterns(ctxt *build.Context, patterns []string) map[string]bool {
+	// TODO(adonovan): support other features of 'go list':
+	// - "std"/"cmd"/"all" meta-packages
+	// - "..." not at the end of a pattern
+	// - relative patterns using "./" or "../" prefix
+
+	pkgs := make(map[string]bool)
+	doPkg := func(pkg string, neg bool) {
+		if neg {
+			delete(pkgs, pkg)
+		} else {
+			pkgs[pkg] = true
+		}
+	}
+
+	// Scan entire workspace if wildcards are present.
+	// TODO(adonovan): opt: scan only the necessary subtrees of the workspace.
+	var all []string
+	for _, arg := range patterns {
+		if strings.HasSuffix(arg, "...") {
+			all = AllPackages(ctxt)
+			break
+		}
+	}
+
+	for _, arg := range patterns {
+		if arg == "" {
+			continue
+		}
+
+		neg := arg[0] == '-'
+		if neg {
+			arg = arg[1:]
+		}
+
+		if arg == "..." {
+			// ... matches all packages
+			for _, pkg := range all {
+				doPkg(pkg, neg)
+			}
+		} else if dir := strings.TrimSuffix(arg, "/..."); dir != arg {
+			// dir/... matches all packages beneath dir
+			for _, pkg := range all {
+				if strings.HasPrefix(pkg, dir) &&
+					(len(pkg) == len(dir) || pkg[len(dir)] == '/') {
+					doPkg(pkg, neg)
+				}
+			}
+		} else {
+			// single package
+			doPkg(strings.TrimSuffix(arg, "/"), neg)
+		}
+	}
+
+	return pkgs
+}
diff --git a/vendor/golang.org/x/tools/go/buildutil/fakecontext.go b/vendor/golang.org/x/tools/go/buildutil/fakecontext.go
new file mode 100644
index 0000000..763d188
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/buildutil/fakecontext.go
@@ -0,0 +1,111 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package buildutil
+
+import (
+	"fmt"
+	"go/build"
+	"io"
+	"os"
+	"path"
+	"path/filepath"
+	"sort"
+	"strings"
+	"time"
+)
+
+// FakeContext returns a build.Context for the fake file tree specified
+// by pkgs, which maps package import paths to a mapping from file base
+// names to contents.
+//
+// The fake Context has a GOROOT of "/go" and no GOPATH, and overrides
+// the necessary file access methods to read from memory instead of the
+// real file system.
+//
+// Unlike a real file tree, the fake one has only two levels---packages
+// and files---so ReadDir("/go/src/") returns all packages under
+// /go/src/ including, for instance, "math" and "math/big".
+// ReadDir("/go/src/math/big") would return all the files in the
+// "math/big" package.
+func FakeContext(pkgs map[string]map[string]string) *build.Context {
+	clean := func(filename string) string {
+		f := path.Clean(filepath.ToSlash(filename))
+		// Removing "/go/src" while respecting segment
+		// boundaries has this unfortunate corner case:
+		if f == "/go/src" {
+			return ""
+		}
+		return strings.TrimPrefix(f, "/go/src/")
+	}
+
+	ctxt := build.Default // copy
+	ctxt.GOROOT = "/go"
+	ctxt.GOPATH = ""
+	ctxt.Compiler = "gc"
+	ctxt.IsDir = func(dir string) bool {
+		dir = clean(dir)
+		if dir == "" {
+			return true // needed by (*build.Context).SrcDirs
+		}
+		return pkgs[dir] != nil
+	}
+	ctxt.ReadDir = func(dir string) ([]os.FileInfo, error) {
+		dir = clean(dir)
+		var fis []os.FileInfo
+		if dir == "" {
+			// enumerate packages
+			for importPath := range pkgs {
+				fis = append(fis, fakeDirInfo(importPath))
+			}
+		} else {
+			// enumerate files of package
+			for basename := range pkgs[dir] {
+				fis = append(fis, fakeFileInfo(basename))
+			}
+		}
+		sort.Sort(byName(fis))
+		return fis, nil
+	}
+	ctxt.OpenFile = func(filename string) (io.ReadCloser, error) {
+		filename = clean(filename)
+		dir, base := path.Split(filename)
+		content, ok := pkgs[path.Clean(dir)][base]
+		if !ok {
+			return nil, fmt.Errorf("file not found: %s", filename)
+		}
+		return io.NopCloser(strings.NewReader(content)), nil
+	}
+	ctxt.IsAbsPath = func(path string) bool {
+		path = filepath.ToSlash(path)
+		// Don't rely on the default (filepath.Path) since on
+		// Windows, it reports virtual paths as non-absolute.
+		return strings.HasPrefix(path, "/")
+	}
+	return &ctxt
+}
+
+type byName []os.FileInfo
+
+func (s byName) Len() int           { return len(s) }
+func (s byName) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
+func (s byName) Less(i, j int) bool { return s[i].Name() < s[j].Name() }
+
+type fakeFileInfo string
+
+func (fi fakeFileInfo) Name() string    { return string(fi) }
+func (fakeFileInfo) Sys() interface{}   { return nil }
+func (fakeFileInfo) ModTime() time.Time { return time.Time{} }
+func (fakeFileInfo) IsDir() bool        { return false }
+func (fakeFileInfo) Size() int64        { return 0 }
+func (fakeFileInfo) Mode() os.FileMode  { return 0644 }
+
+type fakeDirInfo string
+
+func (fd fakeDirInfo) Name() string    { return string(fd) }
+func (fakeDirInfo) Sys() interface{}   { return nil }
+func (fakeDirInfo) ModTime() time.Time { return time.Time{} }
+func (fakeDirInfo) IsDir() bool        { return true }
+func (fakeDirInfo) Size() int64        { return 0 }
+func (fakeDirInfo) Mode() os.FileMode  { return 0755 }
diff --git a/vendor/golang.org/x/tools/go/buildutil/overlay.go b/vendor/golang.org/x/tools/go/buildutil/overlay.go
new file mode 100644
index 0000000..7e37165
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/buildutil/overlay.go
@@ -0,0 +1,101 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package buildutil
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"go/build"
+	"io"
+	"path/filepath"
+	"strconv"
+	"strings"
+)
+
+// OverlayContext overlays a build.Context with additional files from
+// a map. Files in the map take precedence over other files.
+//
+// In addition to plain string comparison, two file names are
+// considered equal if their base names match and their directory
+// components point at the same directory on the file system. That is,
+// symbolic links are followed for directories, but not files.
+//
+// A common use case for OverlayContext is to allow editors to pass in
+// a set of unsaved, modified files.
+//
+// Currently, only the Context.OpenFile function will respect the
+// overlay. This may change in the future.
+func OverlayContext(orig *build.Context, overlay map[string][]byte) *build.Context {
+	// TODO(dominikh): Implement IsDir, HasSubdir and ReadDir
+
+	rc := func(data []byte) (io.ReadCloser, error) {
+		return io.NopCloser(bytes.NewBuffer(data)), nil
+	}
+
+	copy := *orig // make a copy
+	ctxt := &copy
+	ctxt.OpenFile = func(path string) (io.ReadCloser, error) {
+		// Fast path: names match exactly.
+		if content, ok := overlay[path]; ok {
+			return rc(content)
+		}
+
+		// Slow path: check for same file under a different
+		// alias, perhaps due to a symbolic link.
+		for filename, content := range overlay {
+			if sameFile(path, filename) {
+				return rc(content)
+			}
+		}
+
+		return OpenFile(orig, path)
+	}
+	return ctxt
+}
+
+// ParseOverlayArchive parses an archive containing Go files and their
+// contents. The result is intended to be used with OverlayContext.
+//
+// # Archive format
+//
+// The archive consists of a series of files. Each file consists of a
+// name, a decimal file size and the file contents, separated by
+// newlines. No newline follows after the file contents.
+func ParseOverlayArchive(archive io.Reader) (map[string][]byte, error) {
+	overlay := make(map[string][]byte)
+	r := bufio.NewReader(archive)
+	for {
+		// Read file name.
+		filename, err := r.ReadString('\n')
+		if err != nil {
+			if err == io.EOF {
+				break // OK
+			}
+			return nil, fmt.Errorf("reading archive file name: %v", err)
+		}
+		filename = filepath.Clean(strings.TrimSpace(filename))
+
+		// Read file size.
+		sz, err := r.ReadString('\n')
+		if err != nil {
+			return nil, fmt.Errorf("reading size of archive file %s: %v", filename, err)
+		}
+		sz = strings.TrimSpace(sz)
+		size, err := strconv.ParseUint(sz, 10, 32)
+		if err != nil {
+			return nil, fmt.Errorf("parsing size of archive file %s: %v", filename, err)
+		}
+
+		// Read file content.
+		content := make([]byte, size)
+		if _, err := io.ReadFull(r, content); err != nil {
+			return nil, fmt.Errorf("reading archive file %s: %v", filename, err)
+		}
+		overlay[filename] = content
+	}
+
+	return overlay, nil
+}
diff --git a/vendor/golang.org/x/tools/go/buildutil/tags.go b/vendor/golang.org/x/tools/go/buildutil/tags.go
new file mode 100644
index 0000000..32c8d14
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/buildutil/tags.go
@@ -0,0 +1,100 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package buildutil
+
+// This duplicated logic must be kept in sync with that from go build:
+//   $GOROOT/src/cmd/go/internal/work/build.go (tagsFlag.Set)
+//   $GOROOT/src/cmd/go/internal/base/flag.go (StringsFlag.Set)
+//   $GOROOT/src/cmd/internal/quoted/quoted.go (isSpaceByte, Split)
+
+import (
+	"fmt"
+	"strings"
+)
+
+const TagsFlagDoc = "a list of `build tags` to consider satisfied during the build. " +
+	"For more information about build tags, see the description of " +
+	"build constraints in the documentation for the go/build package"
+
+// TagsFlag is an implementation of the flag.Value and flag.Getter interfaces that parses
+// a flag value the same as go build's -tags flag and populates a []string slice.
+//
+// See $GOROOT/src/go/build/doc.go for description of build tags.
+// See $GOROOT/src/cmd/go/doc.go for description of 'go build -tags' flag.
+//
+// Example:
+//
+//	flag.Var((*buildutil.TagsFlag)(&build.Default.BuildTags), "tags", buildutil.TagsFlagDoc)
+type TagsFlag []string
+
+func (v *TagsFlag) Set(s string) error {
+	// See $GOROOT/src/cmd/go/internal/work/build.go (tagsFlag.Set)
+	// For compatibility with Go 1.12 and earlier, allow "-tags='a b c'" or even just "-tags='a'".
+	if strings.Contains(s, " ") || strings.Contains(s, "'") {
+		var err error
+		*v, err = splitQuotedFields(s)
+		if *v == nil {
+			*v = []string{}
+		}
+		return err
+	}
+
+	// Starting in Go 1.13, the -tags flag is a comma-separated list of build tags.
+	*v = []string{}
+	for _, s := range strings.Split(s, ",") {
+		if s != "" {
+			*v = append(*v, s)
+		}
+	}
+	return nil
+}
+
+func (v *TagsFlag) Get() interface{} { return *v }
+
+func splitQuotedFields(s string) ([]string, error) {
+	// See $GOROOT/src/cmd/internal/quoted/quoted.go (Split)
+	// This must remain in sync with that logic.
+	var f []string
+	for len(s) > 0 {
+		for len(s) > 0 && isSpaceByte(s[0]) {
+			s = s[1:]
+		}
+		if len(s) == 0 {
+			break
+		}
+		// Accepted quoted string. No unescaping inside.
+		if s[0] == '"' || s[0] == '\'' {
+			quote := s[0]
+			s = s[1:]
+			i := 0
+			for i < len(s) && s[i] != quote {
+				i++
+			}
+			if i >= len(s) {
+				return nil, fmt.Errorf("unterminated %c string", quote)
+			}
+			f = append(f, s[:i])
+			s = s[i+1:]
+			continue
+		}
+		i := 0
+		for i < len(s) && !isSpaceByte(s[i]) {
+			i++
+		}
+		f = append(f, s[:i])
+		s = s[i:]
+	}
+	return f, nil
+}
+
+func (v *TagsFlag) String() string {
+	return "<tagsFlag>"
+}
+
+func isSpaceByte(c byte) bool {
+	// See $GOROOT/src/cmd/internal/quoted/quoted.go (isSpaceByte, Split)
+	// This list must remain in sync with that.
+	return c == ' ' || c == '\t' || c == '\n' || c == '\r'
+}
diff --git a/vendor/golang.org/x/tools/go/buildutil/util.go b/vendor/golang.org/x/tools/go/buildutil/util.go
new file mode 100644
index 0000000..bee6390
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/buildutil/util.go
@@ -0,0 +1,209 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package buildutil
+
+import (
+	"fmt"
+	"go/ast"
+	"go/build"
+	"go/parser"
+	"go/token"
+	"io"
+	"io/ioutil"
+	"os"
+	"path"
+	"path/filepath"
+	"strings"
+)
+
+// ParseFile behaves like parser.ParseFile,
+// but uses the build context's file system interface, if any.
+//
+// If file is not absolute (as defined by IsAbsPath), the (dir, file)
+// components are joined using JoinPath; dir must be absolute.
+//
+// The displayPath function, if provided, is used to transform the
+// filename that will be attached to the ASTs.
+//
+// TODO(adonovan): call this from go/loader.parseFiles when the tree thaws.
+func ParseFile(fset *token.FileSet, ctxt *build.Context, displayPath func(string) string, dir string, file string, mode parser.Mode) (*ast.File, error) {
+	if !IsAbsPath(ctxt, file) {
+		file = JoinPath(ctxt, dir, file)
+	}
+	rd, err := OpenFile(ctxt, file)
+	if err != nil {
+		return nil, err
+	}
+	defer rd.Close() // ignore error
+	if displayPath != nil {
+		file = displayPath(file)
+	}
+	return parser.ParseFile(fset, file, rd, mode)
+}
+
+// ContainingPackage returns the package containing filename.
+//
+// If filename is not absolute, it is interpreted relative to working directory dir.
+// All I/O is via the build context's file system interface, if any.
+//
+// The '...Files []string' fields of the resulting build.Package are not
+// populated (build.FindOnly mode).
+func ContainingPackage(ctxt *build.Context, dir, filename string) (*build.Package, error) {
+	if !IsAbsPath(ctxt, filename) {
+		filename = JoinPath(ctxt, dir, filename)
+	}
+
+	// We must not assume the file tree uses
+	// "/" always,
+	// `\` always,
+	// or os.PathSeparator (which varies by platform),
+	// but to make any progress, we are forced to assume that
+	// paths will not use `\` unless the PathSeparator
+	// is also `\`, thus we can rely on filepath.ToSlash for some sanity.
+
+	dirSlash := path.Dir(filepath.ToSlash(filename)) + "/"
+
+	// We assume that no source root (GOPATH[i] or GOROOT) contains any other.
+	for _, srcdir := range ctxt.SrcDirs() {
+		srcdirSlash := filepath.ToSlash(srcdir) + "/"
+		if importPath, ok := HasSubdir(ctxt, srcdirSlash, dirSlash); ok {
+			return ctxt.Import(importPath, dir, build.FindOnly)
+		}
+	}
+
+	return nil, fmt.Errorf("can't find package containing %s", filename)
+}
+
+// -- Effective methods of file system interface -------------------------
+
+// (go/build.Context defines these as methods, but does not export them.)
+
+// HasSubdir calls ctxt.HasSubdir (if not nil) or else uses
+// the local file system to answer the question.
+func HasSubdir(ctxt *build.Context, root, dir string) (rel string, ok bool) {
+	if f := ctxt.HasSubdir; f != nil {
+		return f(root, dir)
+	}
+
+	// Try using paths we received.
+	if rel, ok = hasSubdir(root, dir); ok {
+		return
+	}
+
+	// Try expanding symlinks and comparing
+	// expanded against unexpanded and
+	// expanded against expanded.
+	rootSym, _ := filepath.EvalSymlinks(root)
+	dirSym, _ := filepath.EvalSymlinks(dir)
+
+	if rel, ok = hasSubdir(rootSym, dir); ok {
+		return
+	}
+	if rel, ok = hasSubdir(root, dirSym); ok {
+		return
+	}
+	return hasSubdir(rootSym, dirSym)
+}
+
+func hasSubdir(root, dir string) (rel string, ok bool) {
+	const sep = string(filepath.Separator)
+	root = filepath.Clean(root)
+	if !strings.HasSuffix(root, sep) {
+		root += sep
+	}
+
+	dir = filepath.Clean(dir)
+	if !strings.HasPrefix(dir, root) {
+		return "", false
+	}
+
+	return filepath.ToSlash(dir[len(root):]), true
+}
+
+// FileExists returns true if the specified file exists,
+// using the build context's file system interface.
+func FileExists(ctxt *build.Context, path string) bool {
+	if ctxt.OpenFile != nil {
+		r, err := ctxt.OpenFile(path)
+		if err != nil {
+			return false
+		}
+		r.Close() // ignore error
+		return true
+	}
+	_, err := os.Stat(path)
+	return err == nil
+}
+
+// OpenFile behaves like os.Open,
+// but uses the build context's file system interface, if any.
+func OpenFile(ctxt *build.Context, path string) (io.ReadCloser, error) {
+	if ctxt.OpenFile != nil {
+		return ctxt.OpenFile(path)
+	}
+	return os.Open(path)
+}
+
+// IsAbsPath behaves like filepath.IsAbs,
+// but uses the build context's file system interface, if any.
+func IsAbsPath(ctxt *build.Context, path string) bool {
+	if ctxt.IsAbsPath != nil {
+		return ctxt.IsAbsPath(path)
+	}
+	return filepath.IsAbs(path)
+}
+
+// JoinPath behaves like filepath.Join,
+// but uses the build context's file system interface, if any.
+func JoinPath(ctxt *build.Context, path ...string) string {
+	if ctxt.JoinPath != nil {
+		return ctxt.JoinPath(path...)
+	}
+	return filepath.Join(path...)
+}
+
+// IsDir behaves like os.Stat plus IsDir,
+// but uses the build context's file system interface, if any.
+func IsDir(ctxt *build.Context, path string) bool {
+	if ctxt.IsDir != nil {
+		return ctxt.IsDir(path)
+	}
+	fi, err := os.Stat(path)
+	return err == nil && fi.IsDir()
+}
+
+// ReadDir behaves like ioutil.ReadDir,
+// but uses the build context's file system interface, if any.
+func ReadDir(ctxt *build.Context, path string) ([]os.FileInfo, error) {
+	if ctxt.ReadDir != nil {
+		return ctxt.ReadDir(path)
+	}
+	return ioutil.ReadDir(path)
+}
+
+// SplitPathList behaves like filepath.SplitList,
+// but uses the build context's file system interface, if any.
+func SplitPathList(ctxt *build.Context, s string) []string {
+	if ctxt.SplitPathList != nil {
+		return ctxt.SplitPathList(s)
+	}
+	return filepath.SplitList(s)
+}
+
+// sameFile returns true if x and y have the same basename and denote
+// the same file.
+func sameFile(x, y string) bool {
+	if path.Clean(x) == path.Clean(y) {
+		return true
+	}
+	if filepath.Base(x) == filepath.Base(y) { // (optimisation)
+		if xi, err := os.Stat(x); err == nil {
+			if yi, err := os.Stat(y); err == nil {
+				return os.SameFile(xi, yi)
+			}
+		}
+	}
+	return false
+}
diff --git a/vendor/golang.org/x/tools/go/callgraph/callgraph.go b/vendor/golang.org/x/tools/go/callgraph/callgraph.go
new file mode 100644
index 0000000..a1b0ca5
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/callgraph/callgraph.go
@@ -0,0 +1,129 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+/*
+Package callgraph defines the call graph and various algorithms
+and utilities to operate on it.
+
+A call graph is a labelled directed graph whose nodes represent
+functions and whose edge labels represent syntactic function call
+sites.  The presence of a labelled edge (caller, site, callee)
+indicates that caller may call callee at the specified call site.
+
+A call graph is a multigraph: it may contain multiple edges (caller,
+*, callee) connecting the same pair of nodes, so long as the edges
+differ by label; this occurs when one function calls another function
+from multiple call sites.  Also, it may contain multiple edges
+(caller, site, *) that differ only by callee; this indicates a
+polymorphic call.
+
+A SOUND call graph is one that overapproximates the dynamic calling
+behaviors of the program in all possible executions.  One call graph
+is more PRECISE than another if it is a smaller overapproximation of
+the dynamic behavior.
+
+All call graphs have a synthetic root node which is responsible for
+calling main() and init().
+
+Calls to built-in functions (e.g. panic, println) are not represented
+in the call graph; they are treated like built-in operators of the
+language.
+*/
+package callgraph // import "golang.org/x/tools/go/callgraph"
+
+// TODO(adonovan): add a function to eliminate wrappers from the
+// callgraph, preserving topology.
+// More generally, we could eliminate "uninteresting" nodes such as
+// nodes from packages we don't care about.
+
+// TODO(zpavlinovic): decide how callgraphs handle calls to and from generic function bodies.
+
+import (
+	"fmt"
+	"go/token"
+
+	"golang.org/x/tools/go/ssa"
+)
+
+// A Graph represents a call graph.
+//
+// A graph may contain nodes that are not reachable from the root.
+// If the call graph is sound, such nodes indicate unreachable
+// functions.
+type Graph struct {
+	Root  *Node                   // the distinguished root node
+	Nodes map[*ssa.Function]*Node // all nodes by function
+}
+
+// New returns a new Graph with the specified root node.
+func New(root *ssa.Function) *Graph {
+	g := &Graph{Nodes: make(map[*ssa.Function]*Node)}
+	g.Root = g.CreateNode(root)
+	return g
+}
+
+// CreateNode returns the Node for fn, creating it if not present.
+// The root node may have fn=nil.
+func (g *Graph) CreateNode(fn *ssa.Function) *Node {
+	n, ok := g.Nodes[fn]
+	if !ok {
+		n = &Node{Func: fn, ID: len(g.Nodes)}
+		g.Nodes[fn] = n
+	}
+	return n
+}
+
+// A Node represents a node in a call graph.
+type Node struct {
+	Func *ssa.Function // the function this node represents
+	ID   int           // 0-based sequence number
+	In   []*Edge       // unordered set of incoming call edges (n.In[*].Callee == n)
+	Out  []*Edge       // unordered set of outgoing call edges (n.Out[*].Caller == n)
+}
+
+func (n *Node) String() string {
+	return fmt.Sprintf("n%d:%s", n.ID, n.Func)
+}
+
+// A Edge represents an edge in the call graph.
+//
+// Site is nil for edges originating in synthetic or intrinsic
+// functions, e.g. reflect.Value.Call or the root of the call graph.
+type Edge struct {
+	Caller *Node
+	Site   ssa.CallInstruction
+	Callee *Node
+}
+
+func (e Edge) String() string {
+	return fmt.Sprintf("%s --> %s", e.Caller, e.Callee)
+}
+
+func (e Edge) Description() string {
+	var prefix string
+	switch e.Site.(type) {
+	case nil:
+		return "synthetic call"
+	case *ssa.Go:
+		prefix = "concurrent "
+	case *ssa.Defer:
+		prefix = "deferred "
+	}
+	return prefix + e.Site.Common().Description()
+}
+
+func (e Edge) Pos() token.Pos {
+	if e.Site == nil {
+		return token.NoPos
+	}
+	return e.Site.Pos()
+}
+
+// AddEdge adds the edge (caller, site, callee) to the call graph.
+// Elimination of duplicate edges is the caller's responsibility.
+func AddEdge(caller *Node, site ssa.CallInstruction, callee *Node) {
+	e := &Edge{caller, site, callee}
+	callee.In = append(callee.In, e)
+	caller.Out = append(caller.Out, e)
+}
diff --git a/vendor/golang.org/x/tools/go/callgraph/cha/cha.go b/vendor/golang.org/x/tools/go/callgraph/cha/cha.go
new file mode 100644
index 0000000..3040f3d
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/callgraph/cha/cha.go
@@ -0,0 +1,164 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package cha computes the call graph of a Go program using the Class
+// Hierarchy Analysis (CHA) algorithm.
+//
+// CHA was first described in "Optimization of Object-Oriented Programs
+// Using Static Class Hierarchy Analysis", Jeffrey Dean, David Grove,
+// and Craig Chambers, ECOOP'95.
+//
+// CHA is related to RTA (see go/callgraph/rta); the difference is that
+// CHA conservatively computes the entire "implements" relation between
+// interfaces and concrete types ahead of time, whereas RTA uses dynamic
+// programming to construct it on the fly as it encounters new functions
+// reachable from main.  CHA may thus include spurious call edges for
+// types that haven't been instantiated yet, or types that are never
+// instantiated.
+//
+// Since CHA conservatively assumes that all functions are address-taken
+// and all concrete types are put into interfaces, it is sound to run on
+// partial programs, such as libraries without a main or test function.
+package cha // import "golang.org/x/tools/go/callgraph/cha"
+
+// TODO(zpavlinovic): update CHA for how it handles generic function bodies.
+
+import (
+	"go/types"
+
+	"golang.org/x/tools/go/callgraph"
+	"golang.org/x/tools/go/ssa"
+	"golang.org/x/tools/go/ssa/ssautil"
+	"golang.org/x/tools/go/types/typeutil"
+)
+
+// CallGraph computes the call graph of the specified program using the
+// Class Hierarchy Analysis algorithm.
+func CallGraph(prog *ssa.Program) *callgraph.Graph {
+	cg := callgraph.New(nil) // TODO(adonovan) eliminate concept of rooted callgraph
+
+	allFuncs := ssautil.AllFunctions(prog)
+
+	calleesOf := lazyCallees(allFuncs)
+
+	addEdge := func(fnode *callgraph.Node, site ssa.CallInstruction, g *ssa.Function) {
+		gnode := cg.CreateNode(g)
+		callgraph.AddEdge(fnode, site, gnode)
+	}
+
+	addEdges := func(fnode *callgraph.Node, site ssa.CallInstruction, callees []*ssa.Function) {
+		// Because every call to a highly polymorphic and
+		// frequently used abstract method such as
+		// (io.Writer).Write is assumed to call every concrete
+		// Write method in the program, the call graph can
+		// contain a lot of duplication.
+		//
+		// TODO(taking): opt: consider making lazyCallees public.
+		// Using the same benchmarks as callgraph_test.go, removing just
+		// the explicit callgraph.Graph construction is 4x less memory
+		// and is 37% faster.
+		// CHA			86 ms/op	16 MB/op
+		// lazyCallees	63 ms/op	 4 MB/op
+		for _, g := range callees {
+			addEdge(fnode, site, g)
+		}
+	}
+
+	for f := range allFuncs {
+		fnode := cg.CreateNode(f)
+		for _, b := range f.Blocks {
+			for _, instr := range b.Instrs {
+				if site, ok := instr.(ssa.CallInstruction); ok {
+					if g := site.Common().StaticCallee(); g != nil {
+						addEdge(fnode, site, g)
+					} else {
+						addEdges(fnode, site, calleesOf(site))
+					}
+				}
+			}
+		}
+	}
+
+	return cg
+}
+
+// lazyCallees returns a function that maps a call site (in a function in fns)
+// to its callees within fns.
+//
+// The resulting function is not concurrency safe.
+func lazyCallees(fns map[*ssa.Function]bool) func(site ssa.CallInstruction) []*ssa.Function {
+	// funcsBySig contains all functions, keyed by signature.  It is
+	// the effective set of address-taken functions used to resolve
+	// a dynamic call of a particular signature.
+	var funcsBySig typeutil.Map // value is []*ssa.Function
+
+	// methodsByID contains all methods, grouped by ID for efficient
+	// lookup.
+	//
+	// We must key by ID, not name, for correct resolution of interface
+	// calls to a type with two (unexported) methods spelled the same but
+	// from different packages. The fact that the concrete type implements
+	// the interface does not mean the call dispatches to both methods.
+	methodsByID := make(map[string][]*ssa.Function)
+
+	// An imethod represents an interface method I.m.
+	// (There's no go/types object for it;
+	// a *types.Func may be shared by many interfaces due to interface embedding.)
+	type imethod struct {
+		I  *types.Interface
+		id string
+	}
+	// methodsMemo records, for every abstract method call I.m on
+	// interface type I, the set of concrete methods C.m of all
+	// types C that satisfy interface I.
+	//
+	// Abstract methods may be shared by several interfaces,
+	// hence we must pass I explicitly, not guess from m.
+	//
+	// methodsMemo is just a cache, so it needn't be a typeutil.Map.
+	methodsMemo := make(map[imethod][]*ssa.Function)
+	lookupMethods := func(I *types.Interface, m *types.Func) []*ssa.Function {
+		id := m.Id()
+		methods, ok := methodsMemo[imethod{I, id}]
+		if !ok {
+			for _, f := range methodsByID[id] {
+				C := f.Signature.Recv().Type() // named or *named
+				if types.Implements(C, I) {
+					methods = append(methods, f)
+				}
+			}
+			methodsMemo[imethod{I, id}] = methods
+		}
+		return methods
+	}
+
+	for f := range fns {
+		if f.Signature.Recv() == nil {
+			// Package initializers can never be address-taken.
+			if f.Name() == "init" && f.Synthetic == "package initializer" {
+				continue
+			}
+			funcs, _ := funcsBySig.At(f.Signature).([]*ssa.Function)
+			funcs = append(funcs, f)
+			funcsBySig.Set(f.Signature, funcs)
+		} else if obj := f.Object(); obj != nil {
+			id := obj.(*types.Func).Id()
+			methodsByID[id] = append(methodsByID[id], f)
+		}
+	}
+
+	return func(site ssa.CallInstruction) []*ssa.Function {
+		call := site.Common()
+		if call.IsInvoke() {
+			tiface := call.Value.Type().Underlying().(*types.Interface)
+			return lookupMethods(tiface, call.Method)
+		} else if g := call.StaticCallee(); g != nil {
+			return []*ssa.Function{g}
+		} else if _, ok := call.Value.(*ssa.Builtin); !ok {
+			fns, _ := funcsBySig.At(call.Signature()).([]*ssa.Function)
+			return fns
+		}
+		return nil
+	}
+}
diff --git a/vendor/golang.org/x/tools/go/callgraph/util.go b/vendor/golang.org/x/tools/go/callgraph/util.go
new file mode 100644
index 0000000..5499320
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/callgraph/util.go
@@ -0,0 +1,180 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package callgraph
+
+import "golang.org/x/tools/go/ssa"
+
+// This file provides various utilities over call graphs, such as
+// visitation and path search.
+
+// CalleesOf returns a new set containing all direct callees of the
+// caller node.
+func CalleesOf(caller *Node) map[*Node]bool {
+	callees := make(map[*Node]bool)
+	for _, e := range caller.Out {
+		callees[e.Callee] = true
+	}
+	return callees
+}
+
+// GraphVisitEdges visits all the edges in graph g in depth-first order.
+// The edge function is called for each edge in postorder.  If it
+// returns non-nil, visitation stops and GraphVisitEdges returns that
+// value.
+func GraphVisitEdges(g *Graph, edge func(*Edge) error) error {
+	seen := make(map[*Node]bool)
+	var visit func(n *Node) error
+	visit = func(n *Node) error {
+		if !seen[n] {
+			seen[n] = true
+			for _, e := range n.Out {
+				if err := visit(e.Callee); err != nil {
+					return err
+				}
+				if err := edge(e); err != nil {
+					return err
+				}
+			}
+		}
+		return nil
+	}
+	for _, n := range g.Nodes {
+		if err := visit(n); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// PathSearch finds an arbitrary path starting at node start and
+// ending at some node for which isEnd() returns true.  On success,
+// PathSearch returns the path as an ordered list of edges; on
+// failure, it returns nil.
+func PathSearch(start *Node, isEnd func(*Node) bool) []*Edge {
+	stack := make([]*Edge, 0, 32)
+	seen := make(map[*Node]bool)
+	var search func(n *Node) []*Edge
+	search = func(n *Node) []*Edge {
+		if !seen[n] {
+			seen[n] = true
+			if isEnd(n) {
+				return stack
+			}
+			for _, e := range n.Out {
+				stack = append(stack, e) // push
+				if found := search(e.Callee); found != nil {
+					return found
+				}
+				stack = stack[:len(stack)-1] // pop
+			}
+		}
+		return nil
+	}
+	return search(start)
+}
+
+// DeleteSyntheticNodes removes from call graph g all nodes for
+// functions that do not correspond to source syntax. For historical
+// reasons, nodes for g.Root and package initializers are always
+// kept.
+//
+// As nodes are removed, edges are created to preserve the
+// reachability relation of the remaining nodes.
+func (g *Graph) DeleteSyntheticNodes() {
+	// Measurements on the standard library and go.tools show that
+	// resulting graph has ~15% fewer nodes and 4-8% fewer edges
+	// than the input.
+	//
+	// Inlining a wrapper of in-degree m, out-degree n adds m*n
+	// and removes m+n edges.  Since most wrappers are monomorphic
+	// (n=1) this results in a slight reduction.  Polymorphic
+	// wrappers (n>1), e.g. from embedding an interface value
+	// inside a struct to satisfy some interface, cause an
+	// increase in the graph, but they seem to be uncommon.
+
+	// Hash all existing edges to avoid creating duplicates.
+	edges := make(map[Edge]bool)
+	for _, cgn := range g.Nodes {
+		for _, e := range cgn.Out {
+			edges[*e] = true
+		}
+	}
+	for fn, cgn := range g.Nodes {
+		if cgn == g.Root || isInit(cgn.Func) || fn.Syntax() != nil {
+			continue // keep
+		}
+		for _, eIn := range cgn.In {
+			for _, eOut := range cgn.Out {
+				newEdge := Edge{eIn.Caller, eIn.Site, eOut.Callee}
+				if edges[newEdge] {
+					continue // don't add duplicate
+				}
+				AddEdge(eIn.Caller, eIn.Site, eOut.Callee)
+				edges[newEdge] = true
+			}
+		}
+		g.DeleteNode(cgn)
+	}
+}
+
+func isInit(fn *ssa.Function) bool {
+	return fn.Pkg != nil && fn.Pkg.Func("init") == fn
+}
+
+// DeleteNode removes node n and its edges from the graph g.
+// (NB: not efficient for batch deletion.)
+func (g *Graph) DeleteNode(n *Node) {
+	n.deleteIns()
+	n.deleteOuts()
+	delete(g.Nodes, n.Func)
+}
+
+// deleteIns deletes all incoming edges to n.
+func (n *Node) deleteIns() {
+	for _, e := range n.In {
+		removeOutEdge(e)
+	}
+	n.In = nil
+}
+
+// deleteOuts deletes all outgoing edges from n.
+func (n *Node) deleteOuts() {
+	for _, e := range n.Out {
+		removeInEdge(e)
+	}
+	n.Out = nil
+}
+
+// removeOutEdge removes edge.Caller's outgoing edge 'edge'.
+func removeOutEdge(edge *Edge) {
+	caller := edge.Caller
+	n := len(caller.Out)
+	for i, e := range caller.Out {
+		if e == edge {
+			// Replace it with the final element and shrink the slice.
+			caller.Out[i] = caller.Out[n-1]
+			caller.Out[n-1] = nil // aid GC
+			caller.Out = caller.Out[:n-1]
+			return
+		}
+	}
+	panic("edge not found: " + edge.String())
+}
+
+// removeInEdge removes edge.Callee's incoming edge 'edge'.
+func removeInEdge(edge *Edge) {
+	caller := edge.Callee
+	n := len(caller.In)
+	for i, e := range caller.In {
+		if e == edge {
+			// Replace it with the final element and shrink the slice.
+			caller.In[i] = caller.In[n-1]
+			caller.In[n-1] = nil // aid GC
+			caller.In = caller.In[:n-1]
+			return
+		}
+	}
+	panic("edge not found: " + edge.String())
+}
diff --git a/vendor/golang.org/x/tools/go/gcexportdata/gcexportdata.go b/vendor/golang.org/x/tools/go/gcexportdata/gcexportdata.go
new file mode 100644
index 0000000..137cc8d
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/gcexportdata/gcexportdata.go
@@ -0,0 +1,186 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package gcexportdata provides functions for locating, reading, and
+// writing export data files containing type information produced by the
+// gc compiler.  This package supports go1.7 export data format and all
+// later versions.
+//
+// Although it might seem convenient for this package to live alongside
+// go/types in the standard library, this would cause version skew
+// problems for developer tools that use it, since they must be able to
+// consume the outputs of the gc compiler both before and after a Go
+// update such as from Go 1.7 to Go 1.8.  Because this package lives in
+// golang.org/x/tools, sites can update their version of this repo some
+// time before the Go 1.8 release and rebuild and redeploy their
+// developer tools, which will then be able to consume both Go 1.7 and
+// Go 1.8 export data files, so they will work before and after the
+// Go update. (See discussion at https://golang.org/issue/15651.)
+package gcexportdata // import "golang.org/x/tools/go/gcexportdata"
+
+import (
+	"bufio"
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"go/token"
+	"go/types"
+	"io"
+	"os/exec"
+
+	"golang.org/x/tools/internal/gcimporter"
+)
+
+// Find returns the name of an object (.o) or archive (.a) file
+// containing type information for the specified import path,
+// using the go command.
+// If no file was found, an empty filename is returned.
+//
+// A relative srcDir is interpreted relative to the current working directory.
+//
+// Find also returns the package's resolved (canonical) import path,
+// reflecting the effects of srcDir and vendoring on importPath.
+//
+// Deprecated: Use the higher-level API in golang.org/x/tools/go/packages,
+// which is more efficient.
+func Find(importPath, srcDir string) (filename, path string) {
+	cmd := exec.Command("go", "list", "-json", "-export", "--", importPath)
+	cmd.Dir = srcDir
+	out, err := cmd.Output()
+	if err != nil {
+		return "", ""
+	}
+	var data struct {
+		ImportPath string
+		Export     string
+	}
+	json.Unmarshal(out, &data)
+	return data.Export, data.ImportPath
+}
+
+// NewReader returns a reader for the export data section of an object
+// (.o) or archive (.a) file read from r.  The new reader may provide
+// additional trailing data beyond the end of the export data.
+func NewReader(r io.Reader) (io.Reader, error) {
+	buf := bufio.NewReader(r)
+	_, size, err := gcimporter.FindExportData(buf)
+	if err != nil {
+		return nil, err
+	}
+
+	if size >= 0 {
+		// We were given an archive and found the __.PKGDEF in it.
+		// This tells us the size of the export data, and we don't
+		// need to return the entire file.
+		return &io.LimitedReader{
+			R: buf,
+			N: size,
+		}, nil
+	} else {
+		// We were given an object file. As such, we don't know how large
+		// the export data is and must return the entire file.
+		return buf, nil
+	}
+}
+
+// readAll works the same way as io.ReadAll, but avoids allocations and copies
+// by preallocating a byte slice of the necessary size if the size is known up
+// front. This is always possible when the input is an archive. In that case,
+// NewReader will return the known size using an io.LimitedReader.
+func readAll(r io.Reader) ([]byte, error) {
+	if lr, ok := r.(*io.LimitedReader); ok {
+		data := make([]byte, lr.N)
+		_, err := io.ReadFull(lr, data)
+		return data, err
+	}
+	return io.ReadAll(r)
+}
+
+// Read reads export data from in, decodes it, and returns type
+// information for the package.
+//
+// The package path (effectively its linker symbol prefix) is
+// specified by path, since unlike the package name, this information
+// may not be recorded in the export data.
+//
+// File position information is added to fset.
+//
+// Read may inspect and add to the imports map to ensure that references
+// within the export data to other packages are consistent.  The caller
+// must ensure that imports[path] does not exist, or exists but is
+// incomplete (see types.Package.Complete), and Read inserts the
+// resulting package into this map entry.
+//
+// On return, the state of the reader is undefined.
+func Read(in io.Reader, fset *token.FileSet, imports map[string]*types.Package, path string) (*types.Package, error) {
+	data, err := readAll(in)
+	if err != nil {
+		return nil, fmt.Errorf("reading export data for %q: %v", path, err)
+	}
+
+	if bytes.HasPrefix(data, []byte("!<arch>")) {
+		return nil, fmt.Errorf("can't read export data for %q directly from an archive file (call gcexportdata.NewReader first to extract export data)", path)
+	}
+
+	// The indexed export format starts with an 'i'; the older
+	// binary export format starts with a 'c', 'd', or 'v'
+	// (from "version"). Select appropriate importer.
+	if len(data) > 0 {
+		switch data[0] {
+		case 'v', 'c', 'd': // binary, till go1.10
+			return nil, fmt.Errorf("binary (%c) import format is no longer supported", data[0])
+
+		case 'i': // indexed, till go1.19
+			_, pkg, err := gcimporter.IImportData(fset, imports, data[1:], path)
+			return pkg, err
+
+		case 'u': // unified, from go1.20
+			_, pkg, err := gcimporter.UImportData(fset, imports, data[1:], path)
+			return pkg, err
+
+		default:
+			l := len(data)
+			if l > 10 {
+				l = 10
+			}
+			return nil, fmt.Errorf("unexpected export data with prefix %q for path %s", string(data[:l]), path)
+		}
+	}
+	return nil, fmt.Errorf("empty export data for %s", path)
+}
+
+// Write writes encoded type information for the specified package to out.
+// The FileSet provides file position information for named objects.
+func Write(out io.Writer, fset *token.FileSet, pkg *types.Package) error {
+	if _, err := io.WriteString(out, "i"); err != nil {
+		return err
+	}
+	return gcimporter.IExportData(out, fset, pkg)
+}
+
+// ReadBundle reads an export bundle from in, decodes it, and returns type
+// information for the packages.
+// File position information is added to fset.
+//
+// ReadBundle may inspect and add to the imports map to ensure that references
+// within the export bundle to other packages are consistent.
+//
+// On return, the state of the reader is undefined.
+//
+// Experimental: This API is experimental and may change in the future.
+func ReadBundle(in io.Reader, fset *token.FileSet, imports map[string]*types.Package) ([]*types.Package, error) {
+	data, err := readAll(in)
+	if err != nil {
+		return nil, fmt.Errorf("reading export bundle: %v", err)
+	}
+	return gcimporter.IImportBundle(fset, imports, data)
+}
+
+// WriteBundle writes encoded type information for the specified packages to out.
+// The FileSet provides file position information for named objects.
+//
+// Experimental: This API is experimental and may change in the future.
+func WriteBundle(out io.Writer, fset *token.FileSet, pkgs []*types.Package) error {
+	return gcimporter.IExportBundle(out, fset, pkgs)
+}
diff --git a/vendor/golang.org/x/tools/go/gcexportdata/importer.go b/vendor/golang.org/x/tools/go/gcexportdata/importer.go
new file mode 100644
index 0000000..37a7247
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/gcexportdata/importer.go
@@ -0,0 +1,75 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gcexportdata
+
+import (
+	"fmt"
+	"go/token"
+	"go/types"
+	"os"
+)
+
+// NewImporter returns a new instance of the types.Importer interface
+// that reads type information from export data files written by gc.
+// The Importer also satisfies types.ImporterFrom.
+//
+// Export data files are located using "go build" workspace conventions
+// and the build.Default context.
+//
+// Use this importer instead of go/importer.For("gc", ...) to avoid the
+// version-skew problems described in the documentation of this package,
+// or to control the FileSet or access the imports map populated during
+// package loading.
+//
+// Deprecated: Use the higher-level API in golang.org/x/tools/go/packages,
+// which is more efficient.
+func NewImporter(fset *token.FileSet, imports map[string]*types.Package) types.ImporterFrom {
+	return importer{fset, imports}
+}
+
+type importer struct {
+	fset    *token.FileSet
+	imports map[string]*types.Package
+}
+
+func (imp importer) Import(importPath string) (*types.Package, error) {
+	return imp.ImportFrom(importPath, "", 0)
+}
+
+func (imp importer) ImportFrom(importPath, srcDir string, mode types.ImportMode) (_ *types.Package, err error) {
+	filename, path := Find(importPath, srcDir)
+	if filename == "" {
+		if importPath == "unsafe" {
+			// Even for unsafe, call Find first in case
+			// the package was vendored.
+			return types.Unsafe, nil
+		}
+		return nil, fmt.Errorf("can't find import: %s", importPath)
+	}
+
+	if pkg, ok := imp.imports[path]; ok && pkg.Complete() {
+		return pkg, nil // cache hit
+	}
+
+	// open file
+	f, err := os.Open(filename)
+	if err != nil {
+		return nil, err
+	}
+	defer func() {
+		f.Close()
+		if err != nil {
+			// add file name to error
+			err = fmt.Errorf("reading export data: %s: %v", filename, err)
+		}
+	}()
+
+	r, err := NewReader(f)
+	if err != nil {
+		return nil, err
+	}
+
+	return Read(r, imp.fset, imp.imports, path)
+}
diff --git a/vendor/golang.org/x/tools/go/internal/cgo/cgo.go b/vendor/golang.org/x/tools/go/internal/cgo/cgo.go
new file mode 100644
index 0000000..697974b
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/internal/cgo/cgo.go
@@ -0,0 +1,219 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package cgo handles cgo preprocessing of files containing `import "C"`.
+//
+// DESIGN
+//
+// The approach taken is to run the cgo processor on the package's
+// CgoFiles and parse the output, faking the filenames of the
+// resulting ASTs so that the synthetic file containing the C types is
+// called "C" (e.g. "~/go/src/net/C") and the preprocessed files
+// have their original names (e.g. "~/go/src/net/cgo_unix.go"),
+// not the names of the actual temporary files.
+//
+// The advantage of this approach is its fidelity to 'go build'.  The
+// downside is that the token.Position.Offset for each AST node is
+// incorrect, being an offset within the temporary file.  Line numbers
+// should still be correct because of the //line comments.
+//
+// The logic of this file is mostly plundered from the 'go build'
+// tool, which also invokes the cgo preprocessor.
+//
+//
+// REJECTED ALTERNATIVE
+//
+// An alternative approach that we explored is to extend go/types'
+// Importer mechanism to provide the identity of the importing package
+// so that each time `import "C"` appears it resolves to a different
+// synthetic package containing just the objects needed in that case.
+// The loader would invoke cgo but parse only the cgo_types.go file
+// defining the package-level objects, discarding the other files
+// resulting from preprocessing.
+//
+// The benefit of this approach would have been that source-level
+// syntax information would correspond exactly to the original cgo
+// file, with no preprocessing involved, making source tools like
+// godoc, guru, and eg happy.  However, the approach was rejected
+// due to the additional complexity it would impose on go/types.  (It
+// made for a beautiful demo, though.)
+//
+// cgo files, despite their *.go extension, are not legal Go source
+// files per the specification since they may refer to unexported
+// members of package "C" such as C.int.  Also, a function such as
+// C.getpwent has in effect two types, one matching its C type and one
+// which additionally returns (errno C.int).  The cgo preprocessor
+// uses name mangling to distinguish these two functions in the
+// processed code, but go/types would need to duplicate this logic in
+// its handling of function calls, analogous to the treatment of map
+// lookups in which y=m[k] and y,ok=m[k] are both legal.
+
+package cgo
+
+import (
+	"fmt"
+	"go/ast"
+	"go/build"
+	"go/parser"
+	"go/token"
+	"log"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"regexp"
+	"strings"
+)
+
+// ProcessFiles invokes the cgo preprocessor on bp.CgoFiles, parses
+// the output and returns the resulting ASTs.
+func ProcessFiles(bp *build.Package, fset *token.FileSet, DisplayPath func(path string) string, mode parser.Mode) ([]*ast.File, error) {
+	tmpdir, err := os.MkdirTemp("", strings.Replace(bp.ImportPath, "/", "_", -1)+"_C")
+	if err != nil {
+		return nil, err
+	}
+	defer os.RemoveAll(tmpdir)
+
+	pkgdir := bp.Dir
+	if DisplayPath != nil {
+		pkgdir = DisplayPath(pkgdir)
+	}
+
+	cgoFiles, cgoDisplayFiles, err := Run(bp, pkgdir, tmpdir, false)
+	if err != nil {
+		return nil, err
+	}
+	var files []*ast.File
+	for i := range cgoFiles {
+		rd, err := os.Open(cgoFiles[i])
+		if err != nil {
+			return nil, err
+		}
+		display := filepath.Join(bp.Dir, cgoDisplayFiles[i])
+		f, err := parser.ParseFile(fset, display, rd, mode)
+		rd.Close()
+		if err != nil {
+			return nil, err
+		}
+		files = append(files, f)
+	}
+	return files, nil
+}
+
+var cgoRe = regexp.MustCompile(`[/\\:]`)
+
+// Run invokes the cgo preprocessor on bp.CgoFiles and returns two
+// lists of files: the resulting processed files (in temporary
+// directory tmpdir) and the corresponding names of the unprocessed files.
+//
+// Run is adapted from (*builder).cgo in
+// $GOROOT/src/cmd/go/build.go, but these features are unsupported:
+// Objective C, CGOPKGPATH, CGO_FLAGS.
+//
+// If useabs is set to true, absolute paths of the bp.CgoFiles will be passed in
+// to the cgo preprocessor. This in turn will set the // line comments
+// referring to those files to use absolute paths. This is needed for
+// go/packages using the legacy go list support so it is able to find
+// the original files.
+func Run(bp *build.Package, pkgdir, tmpdir string, useabs bool) (files, displayFiles []string, err error) {
+	cgoCPPFLAGS, _, _, _ := cflags(bp, true)
+	_, cgoexeCFLAGS, _, _ := cflags(bp, false)
+
+	if len(bp.CgoPkgConfig) > 0 {
+		pcCFLAGS, err := pkgConfigFlags(bp)
+		if err != nil {
+			return nil, nil, err
+		}
+		cgoCPPFLAGS = append(cgoCPPFLAGS, pcCFLAGS...)
+	}
+
+	// Allows including _cgo_export.h from .[ch] files in the package.
+	cgoCPPFLAGS = append(cgoCPPFLAGS, "-I", tmpdir)
+
+	// _cgo_gotypes.go (displayed "C") contains the type definitions.
+	files = append(files, filepath.Join(tmpdir, "_cgo_gotypes.go"))
+	displayFiles = append(displayFiles, "C")
+	for _, fn := range bp.CgoFiles {
+		// "foo.cgo1.go" (displayed "foo.go") is the processed Go source.
+		f := cgoRe.ReplaceAllString(fn[:len(fn)-len("go")], "_")
+		files = append(files, filepath.Join(tmpdir, f+"cgo1.go"))
+		displayFiles = append(displayFiles, fn)
+	}
+
+	var cgoflags []string
+	if bp.Goroot && bp.ImportPath == "runtime/cgo" {
+		cgoflags = append(cgoflags, "-import_runtime_cgo=false")
+	}
+	if bp.Goroot && bp.ImportPath == "runtime/race" || bp.ImportPath == "runtime/cgo" {
+		cgoflags = append(cgoflags, "-import_syscall=false")
+	}
+
+	var cgoFiles []string = bp.CgoFiles
+	if useabs {
+		cgoFiles = make([]string, len(bp.CgoFiles))
+		for i := range cgoFiles {
+			cgoFiles[i] = filepath.Join(pkgdir, bp.CgoFiles[i])
+		}
+	}
+
+	args := stringList(
+		"go", "tool", "cgo", "-objdir", tmpdir, cgoflags, "--",
+		cgoCPPFLAGS, cgoexeCFLAGS, cgoFiles,
+	)
+	if false {
+		log.Printf("Running cgo for package %q: %s (dir=%s)", bp.ImportPath, args, pkgdir)
+	}
+	cmd := exec.Command(args[0], args[1:]...)
+	cmd.Dir = pkgdir
+	cmd.Env = append(os.Environ(), "PWD="+pkgdir)
+	cmd.Stdout = os.Stderr
+	cmd.Stderr = os.Stderr
+	if err := cmd.Run(); err != nil {
+		return nil, nil, fmt.Errorf("cgo failed: %s: %s", args, err)
+	}
+
+	return files, displayFiles, nil
+}
+
+// -- unmodified from 'go build' ---------------------------------------
+
+// Return the flags to use when invoking the C or C++ compilers, or cgo.
+func cflags(p *build.Package, def bool) (cppflags, cflags, cxxflags, ldflags []string) {
+	var defaults string
+	if def {
+		defaults = "-g -O2"
+	}
+
+	cppflags = stringList(envList("CGO_CPPFLAGS", ""), p.CgoCPPFLAGS)
+	cflags = stringList(envList("CGO_CFLAGS", defaults), p.CgoCFLAGS)
+	cxxflags = stringList(envList("CGO_CXXFLAGS", defaults), p.CgoCXXFLAGS)
+	ldflags = stringList(envList("CGO_LDFLAGS", defaults), p.CgoLDFLAGS)
+	return
+}
+
+// envList returns the value of the given environment variable broken
+// into fields, using the default value when the variable is empty.
+func envList(key, def string) []string {
+	v := os.Getenv(key)
+	if v == "" {
+		v = def
+	}
+	return strings.Fields(v)
+}
+
+// stringList's arguments should be a sequence of string or []string values.
+// stringList flattens them into a single []string.
+func stringList(args ...interface{}) []string {
+	var x []string
+	for _, arg := range args {
+		switch arg := arg.(type) {
+		case []string:
+			x = append(x, arg...)
+		case string:
+			x = append(x, arg)
+		default:
+			panic("stringList: invalid argument")
+		}
+	}
+	return x
+}
diff --git a/vendor/golang.org/x/tools/go/internal/cgo/cgo_pkgconfig.go b/vendor/golang.org/x/tools/go/internal/cgo/cgo_pkgconfig.go
new file mode 100644
index 0000000..2455be5
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/internal/cgo/cgo_pkgconfig.go
@@ -0,0 +1,42 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package cgo
+
+import (
+	"errors"
+	"fmt"
+	"go/build"
+	"os/exec"
+	"strings"
+)
+
+// pkgConfig runs pkg-config with the specified arguments and returns the flags it prints.
+func pkgConfig(mode string, pkgs []string) (flags []string, err error) {
+	cmd := exec.Command("pkg-config", append([]string{mode}, pkgs...)...)
+	out, err := cmd.Output()
+	if err != nil {
+		s := fmt.Sprintf("%s failed: %v", strings.Join(cmd.Args, " "), err)
+		if len(out) > 0 {
+			s = fmt.Sprintf("%s: %s", s, out)
+		}
+		if err, ok := err.(*exec.ExitError); ok && len(err.Stderr) > 0 {
+			s = fmt.Sprintf("%s\nstderr:\n%s", s, err.Stderr)
+		}
+		return nil, errors.New(s)
+	}
+	if len(out) > 0 {
+		flags = strings.Fields(string(out))
+	}
+	return
+}
+
+// pkgConfigFlags calls pkg-config if needed and returns the cflags
+// needed to build the package.
+func pkgConfigFlags(p *build.Package) (cflags []string, err error) {
+	if len(p.CgoPkgConfig) == 0 {
+		return nil, nil
+	}
+	return pkgConfig("--cflags", p.CgoPkgConfig)
+}
diff --git a/vendor/golang.org/x/tools/go/loader/doc.go b/vendor/golang.org/x/tools/go/loader/doc.go
new file mode 100644
index 0000000..e35b1fd
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/loader/doc.go
@@ -0,0 +1,202 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package loader loads a complete Go program from source code, parsing
+// and type-checking the initial packages plus their transitive closure
+// of dependencies.  The ASTs and the derived facts are retained for
+// later use.
+//
+// Deprecated: This is an older API and does not have support
+// for modules. Use golang.org/x/tools/go/packages instead.
+//
+// The package defines two primary types: Config, which specifies a
+// set of initial packages to load and various other options; and
+// Program, which is the result of successfully loading the packages
+// specified by a configuration.
+//
+// The configuration can be set directly, but *Config provides various
+// convenience methods to simplify the common cases, each of which can
+// be called any number of times.  Finally, these are followed by a
+// call to Load() to actually load and type-check the program.
+//
+//	var conf loader.Config
+//
+//	// Use the command-line arguments to specify
+//	// a set of initial packages to load from source.
+//	// See FromArgsUsage for help.
+//	rest, err := conf.FromArgs(os.Args[1:], wantTests)
+//
+//	// Parse the specified files and create an ad hoc package with path "foo".
+//	// All files must have the same 'package' declaration.
+//	conf.CreateFromFilenames("foo", "foo.go", "bar.go")
+//
+//	// Create an ad hoc package with path "foo" from
+//	// the specified already-parsed files.
+//	// All ASTs must have the same 'package' declaration.
+//	conf.CreateFromFiles("foo", parsedFiles)
+//
+//	// Add "runtime" to the set of packages to be loaded.
+//	conf.Import("runtime")
+//
+//	// Adds "fmt" and "fmt_test" to the set of packages
+//	// to be loaded.  "fmt" will include *_test.go files.
+//	conf.ImportWithTests("fmt")
+//
+//	// Finally, load all the packages specified by the configuration.
+//	prog, err := conf.Load()
+//
+// See examples_test.go for examples of API usage.
+//
+// # CONCEPTS AND TERMINOLOGY
+//
+// The WORKSPACE is the set of packages accessible to the loader.  The
+// workspace is defined by Config.Build, a *build.Context.  The
+// default context treats subdirectories of $GOROOT and $GOPATH as
+// packages, but this behavior may be overridden.
+//
+// An AD HOC package is one specified as a set of source files on the
+// command line.  In the simplest case, it may consist of a single file
+// such as $GOROOT/src/net/http/triv.go.
+//
+// EXTERNAL TEST packages are those comprised of a set of *_test.go
+// files all with the same 'package foo_test' declaration, all in the
+// same directory.  (go/build.Package calls these files XTestFiles.)
+//
+// An IMPORTABLE package is one that can be referred to by some import
+// spec.  Every importable package is uniquely identified by its
+// PACKAGE PATH or just PATH, a string such as "fmt", "encoding/json",
+// or "cmd/vendor/golang.org/x/arch/x86/x86asm".  A package path
+// typically denotes a subdirectory of the workspace.
+//
+// An import declaration uses an IMPORT PATH to refer to a package.
+// Most import declarations use the package path as the import path.
+//
+// Due to VENDORING (https://golang.org/s/go15vendor), the
+// interpretation of an import path may depend on the directory in which
+// it appears.  To resolve an import path to a package path, go/build
+// must search the enclosing directories for a subdirectory named
+// "vendor".
+//
+// ad hoc packages and external test packages are NON-IMPORTABLE.  The
+// path of an ad hoc package is inferred from the package
+// declarations of its files and is therefore not a unique package key.
+// For example, Config.CreatePkgs may specify two initial ad hoc
+// packages, both with path "main".
+//
+// An AUGMENTED package is an importable package P plus all the
+// *_test.go files with same 'package foo' declaration as P.
+// (go/build.Package calls these files TestFiles.)
+//
+// The INITIAL packages are those specified in the configuration.  A
+// DEPENDENCY is a package loaded to satisfy an import in an initial
+// package or another dependency.
+package loader
+
+// IMPLEMENTATION NOTES
+//
+// 'go test', in-package test files, and import cycles
+// ---------------------------------------------------
+//
+// An external test package may depend upon members of the augmented
+// package that are not in the unaugmented package, such as functions
+// that expose internals.  (See bufio/export_test.go for an example.)
+// So, the loader must ensure that for each external test package
+// it loads, it also augments the corresponding non-test package.
+//
+// The import graph over n unaugmented packages must be acyclic; the
+// import graph over n-1 unaugmented packages plus one augmented
+// package must also be acyclic.  ('go test' relies on this.)  But the
+// import graph over n augmented packages may contain cycles.
+//
+// First, all the (unaugmented) non-test packages and their
+// dependencies are imported in the usual way; the loader reports an
+// error if it detects an import cycle.
+//
+// Then, each package P for which testing is desired is augmented by
+// the list P' of its in-package test files, by calling
+// (*types.Checker).Files.  This arrangement ensures that P' may
+// reference definitions within P, but P may not reference definitions
+// within P'.  Furthermore, P' may import any other package, including
+// ones that depend upon P, without an import cycle error.
+//
+// Consider two packages A and B, both of which have lists of
+// in-package test files we'll call A' and B', and which have the
+// following import graph edges:
+//    B  imports A
+//    B' imports A
+//    A' imports B
+// This last edge would be expected to create an error were it not
+// for the special type-checking discipline above.
+// Cycles of size greater than two are possible.  For example:
+//   compress/bzip2/bzip2_test.go (package bzip2)  imports "io/ioutil"
+//   io/ioutil/tempfile_test.go   (package ioutil) imports "regexp"
+//   regexp/exec_test.go          (package regexp) imports "compress/bzip2"
+//
+//
+// Concurrency
+// -----------
+//
+// Let us define the import dependency graph as follows.  Each node is a
+// list of files passed to (Checker).Files at once.  Many of these lists
+// are the production code of an importable Go package, so those nodes
+// are labelled by the package's path.  The remaining nodes are
+// ad hoc packages and lists of in-package *_test.go files that augment
+// an importable package; those nodes have no label.
+//
+// The edges of the graph represent import statements appearing within a
+// file.  An edge connects a node (a list of files) to the node it
+// imports, which is importable and thus always labelled.
+//
+// Loading is controlled by this dependency graph.
+//
+// To reduce I/O latency, we start loading a package's dependencies
+// asynchronously as soon as we've parsed its files and enumerated its
+// imports (scanImports).  This performs a preorder traversal of the
+// import dependency graph.
+//
+// To exploit hardware parallelism, we type-check unrelated packages in
+// parallel, where "unrelated" means not ordered by the partial order of
+// the import dependency graph.
+//
+// We use a concurrency-safe non-blocking cache (importer.imported) to
+// record the results of type-checking, whether success or failure.  An
+// entry is created in this cache by startLoad the first time the
+// package is imported.  The first goroutine to request an entry becomes
+// responsible for completing the task and broadcasting completion to
+// subsequent requestors, which block until then.
+//
+// Type checking occurs in (parallel) postorder: we cannot type-check a
+// set of files until we have loaded and type-checked all of their
+// immediate dependencies (and thus all of their transitive
+// dependencies). If the input were guaranteed free of import cycles,
+// this would be trivial: we could simply wait for completion of the
+// dependencies and then invoke the typechecker.
+//
+// But as we saw in the 'go test' section above, some cycles in the
+// import graph over packages are actually legal, so long as the
+// cycle-forming edge originates in the in-package test files that
+// augment the package.  This explains why the nodes of the import
+// dependency graph are not packages, but lists of files: the unlabelled
+// nodes avoid the cycles.  Consider packages A and B where B imports A
+// and A's in-package tests AT import B.  The naively constructed import
+// graph over packages would contain a cycle (A+AT) --> B --> (A+AT) but
+// the graph over lists of files is AT --> B --> A, where AT is an
+// unlabelled node.
+//
+// Awaiting completion of the dependencies in a cyclic graph would
+// deadlock, so we must materialize the import dependency graph (as
+// importer.graph) and check whether each import edge forms a cycle.  If
+// x imports y, and the graph already contains a path from y to x, then
+// there is an import cycle, in which case the processing of x must not
+// wait for the completion of processing of y.
+//
+// When the type-checker makes a callback (doImport) to the loader for a
+// given import edge, there are two possible cases.  In the normal case,
+// the dependency has already been completely type-checked; doImport
+// does a cache lookup and returns it.  In the cyclic case, the entry in
+// the cache is still necessarily incomplete, indicating a cycle.  We
+// perform the cycle check again to obtain the error message, and return
+// the error.
+//
+// The result of using concurrency is about a 2.5x speedup for stdlib_test.
diff --git a/vendor/golang.org/x/tools/go/loader/loader.go b/vendor/golang.org/x/tools/go/loader/loader.go
new file mode 100644
index 0000000..013c0f5
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/loader/loader.go
@@ -0,0 +1,1066 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package loader
+
+// See doc.go for package documentation and implementation notes.
+
+import (
+	"errors"
+	"fmt"
+	"go/ast"
+	"go/build"
+	"go/parser"
+	"go/token"
+	"go/types"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+	"sync"
+	"time"
+
+	"golang.org/x/tools/go/ast/astutil"
+	"golang.org/x/tools/go/internal/cgo"
+	"golang.org/x/tools/internal/versions"
+)
+
+var ignoreVendor build.ImportMode
+
+const trace = false // show timing info for type-checking
+
+// Config specifies the configuration for loading a whole program from
+// Go source code.
+// The zero value for Config is a ready-to-use default configuration.
+type Config struct {
+	// Fset is the file set for the parser to use when loading the
+	// program.  If nil, it may be lazily initialized by any
+	// method of Config.
+	Fset *token.FileSet
+
+	// ParserMode specifies the mode to be used by the parser when
+	// loading source packages.
+	ParserMode parser.Mode
+
+	// TypeChecker contains options relating to the type checker.
+	//
+	// The supplied IgnoreFuncBodies is not used; the effective
+	// value comes from the TypeCheckFuncBodies func below.
+	// The supplied Import function is not used either.
+	TypeChecker types.Config
+
+	// TypeCheckFuncBodies is a predicate over package paths.
+	// A package for which the predicate is false will
+	// have its package-level declarations type checked, but not
+	// its function bodies; this can be used to quickly load
+	// dependencies from source.  If nil, all func bodies are type
+	// checked.
+	TypeCheckFuncBodies func(path string) bool
+
+	// If Build is non-nil, it is used to locate source packages.
+	// Otherwise &build.Default is used.
+	//
+	// By default, cgo is invoked to preprocess Go files that
+	// import the fake package "C".  This behaviour can be
+	// disabled by setting CGO_ENABLED=0 in the environment prior
+	// to startup, or by setting Build.CgoEnabled=false.
+	Build *build.Context
+
+	// The current directory, used for resolving relative package
+	// references such as "./go/loader".  If empty, os.Getwd will be
+	// used instead.
+	Cwd string
+
+	// If DisplayPath is non-nil, it is used to transform each
+	// file name obtained from Build.Import().  This can be used
+	// to prevent a virtualized build.Config's file names from
+	// leaking into the user interface.
+	DisplayPath func(path string) string
+
+	// If AllowErrors is true, Load will return a Program even
+	// if some of the its packages contained I/O, parser or type
+	// errors; such errors are accessible via PackageInfo.Errors.  If
+	// false, Load will fail if any package had an error.
+	AllowErrors bool
+
+	// CreatePkgs specifies a list of non-importable initial
+	// packages to create.  The resulting packages will appear in
+	// the corresponding elements of the Program.Created slice.
+	CreatePkgs []PkgSpec
+
+	// ImportPkgs specifies a set of initial packages to load.
+	// The map keys are package paths.
+	//
+	// The map value indicates whether to load tests.  If true, Load
+	// will add and type-check two lists of files to the package:
+	// non-test files followed by in-package *_test.go files.  In
+	// addition, it will append the external test package (if any)
+	// to Program.Created.
+	ImportPkgs map[string]bool
+
+	// FindPackage is called during Load to create the build.Package
+	// for a given import path from a given directory.
+	// If FindPackage is nil, (*build.Context).Import is used.
+	// A client may use this hook to adapt to a proprietary build
+	// system that does not follow the "go build" layout
+	// conventions, for example.
+	//
+	// It must be safe to call concurrently from multiple goroutines.
+	FindPackage func(ctxt *build.Context, importPath, fromDir string, mode build.ImportMode) (*build.Package, error)
+
+	// AfterTypeCheck is called immediately after a list of files
+	// has been type-checked and appended to info.Files.
+	//
+	// This optional hook function is the earliest opportunity for
+	// the client to observe the output of the type checker,
+	// which may be useful to reduce analysis latency when loading
+	// a large program.
+	//
+	// The function is permitted to modify info.Info, for instance
+	// to clear data structures that are no longer needed, which can
+	// dramatically reduce peak memory consumption.
+	//
+	// The function may be called twice for the same PackageInfo:
+	// once for the files of the package and again for the
+	// in-package test files.
+	//
+	// It must be safe to call concurrently from multiple goroutines.
+	AfterTypeCheck func(info *PackageInfo, files []*ast.File)
+}
+
+// A PkgSpec specifies a non-importable package to be created by Load.
+// Files are processed first, but typically only one of Files and
+// Filenames is provided.  The path needn't be globally unique.
+//
+// For vendoring purposes, the package's directory is the one that
+// contains the first file.
+type PkgSpec struct {
+	Path      string      // package path ("" => use package declaration)
+	Files     []*ast.File // ASTs of already-parsed files
+	Filenames []string    // names of files to be parsed
+}
+
+// A Program is a Go program loaded from source as specified by a Config.
+type Program struct {
+	Fset *token.FileSet // the file set for this program
+
+	// Created[i] contains the initial package whose ASTs or
+	// filenames were supplied by Config.CreatePkgs[i], followed by
+	// the external test package, if any, of each package in
+	// Config.ImportPkgs ordered by ImportPath.
+	//
+	// NOTE: these files must not import "C".  Cgo preprocessing is
+	// only performed on imported packages, not ad hoc packages.
+	//
+	// TODO(adonovan): we need to copy and adapt the logic of
+	// goFilesPackage (from $GOROOT/src/cmd/go/build.go) and make
+	// Config.Import and Config.Create methods return the same kind
+	// of entity, essentially a build.Package.
+	// Perhaps we can even reuse that type directly.
+	Created []*PackageInfo
+
+	// Imported contains the initially imported packages,
+	// as specified by Config.ImportPkgs.
+	Imported map[string]*PackageInfo
+
+	// AllPackages contains the PackageInfo of every package
+	// encountered by Load: all initial packages and all
+	// dependencies, including incomplete ones.
+	AllPackages map[*types.Package]*PackageInfo
+
+	// importMap is the canonical mapping of package paths to
+	// packages.  It contains all Imported initial packages, but not
+	// Created ones, and all imported dependencies.
+	importMap map[string]*types.Package
+}
+
+// PackageInfo holds the ASTs and facts derived by the type-checker
+// for a single package.
+//
+// Not mutated once exposed via the API.
+type PackageInfo struct {
+	Pkg                   *types.Package
+	Importable            bool        // true if 'import "Pkg.Path()"' would resolve to this
+	TransitivelyErrorFree bool        // true if Pkg and all its dependencies are free of errors
+	Files                 []*ast.File // syntax trees for the package's files
+	Errors                []error     // non-nil if the package had errors
+	types.Info                        // type-checker deductions.
+	dir                   string      // package directory
+
+	checker   *types.Checker // transient type-checker state
+	errorFunc func(error)
+}
+
+func (info *PackageInfo) String() string { return info.Pkg.Path() }
+
+func (info *PackageInfo) appendError(err error) {
+	if info.errorFunc != nil {
+		info.errorFunc(err)
+	} else {
+		fmt.Fprintln(os.Stderr, err)
+	}
+	info.Errors = append(info.Errors, err)
+}
+
+func (conf *Config) fset() *token.FileSet {
+	if conf.Fset == nil {
+		conf.Fset = token.NewFileSet()
+	}
+	return conf.Fset
+}
+
+// ParseFile is a convenience function (intended for testing) that invokes
+// the parser using the Config's FileSet, which is initialized if nil.
+//
+// src specifies the parser input as a string, []byte, or io.Reader, and
+// filename is its apparent name.  If src is nil, the contents of
+// filename are read from the file system.
+func (conf *Config) ParseFile(filename string, src interface{}) (*ast.File, error) {
+	// TODO(adonovan): use conf.build() etc like parseFiles does.
+	return parser.ParseFile(conf.fset(), filename, src, conf.ParserMode)
+}
+
+// FromArgsUsage is a partial usage message that applications calling
+// FromArgs may wish to include in their -help output.
+const FromArgsUsage = `
+<args> is a list of arguments denoting a set of initial packages.
+It may take one of two forms:
+
+1. A list of *.go source files.
+
+   All of the specified files are loaded, parsed and type-checked
+   as a single package.  All the files must belong to the same directory.
+
+2. A list of import paths, each denoting a package.
+
+   The package's directory is found relative to the $GOROOT and
+   $GOPATH using similar logic to 'go build', and the *.go files in
+   that directory are loaded, parsed and type-checked as a single
+   package.
+
+   In addition, all *_test.go files in the directory are then loaded
+   and parsed.  Those files whose package declaration equals that of
+   the non-*_test.go files are included in the primary package.  Test
+   files whose package declaration ends with "_test" are type-checked
+   as another package, the 'external' test package, so that a single
+   import path may denote two packages.  (Whether this behaviour is
+   enabled is tool-specific, and may depend on additional flags.)
+
+A '--' argument terminates the list of packages.
+`
+
+// FromArgs interprets args as a set of initial packages to load from
+// source and updates the configuration.  It returns the list of
+// unconsumed arguments.
+//
+// It is intended for use in command-line interfaces that require a
+// set of initial packages to be specified; see FromArgsUsage message
+// for details.
+//
+// Only superficial errors are reported at this stage; errors dependent
+// on I/O are detected during Load.
+func (conf *Config) FromArgs(args []string, xtest bool) ([]string, error) {
+	var rest []string
+	for i, arg := range args {
+		if arg == "--" {
+			rest = args[i+1:]
+			args = args[:i]
+			break // consume "--" and return the remaining args
+		}
+	}
+
+	if len(args) > 0 && strings.HasSuffix(args[0], ".go") {
+		// Assume args is a list of a *.go files
+		// denoting a single ad hoc package.
+		for _, arg := range args {
+			if !strings.HasSuffix(arg, ".go") {
+				return nil, fmt.Errorf("named files must be .go files: %s", arg)
+			}
+		}
+		conf.CreateFromFilenames("", args...)
+	} else {
+		// Assume args are directories each denoting a
+		// package and (perhaps) an external test, iff xtest.
+		for _, arg := range args {
+			if xtest {
+				conf.ImportWithTests(arg)
+			} else {
+				conf.Import(arg)
+			}
+		}
+	}
+
+	return rest, nil
+}
+
+// CreateFromFilenames is a convenience function that adds
+// a conf.CreatePkgs entry to create a package of the specified *.go
+// files.
+func (conf *Config) CreateFromFilenames(path string, filenames ...string) {
+	conf.CreatePkgs = append(conf.CreatePkgs, PkgSpec{Path: path, Filenames: filenames})
+}
+
+// CreateFromFiles is a convenience function that adds a conf.CreatePkgs
+// entry to create package of the specified path and parsed files.
+func (conf *Config) CreateFromFiles(path string, files ...*ast.File) {
+	conf.CreatePkgs = append(conf.CreatePkgs, PkgSpec{Path: path, Files: files})
+}
+
+// ImportWithTests is a convenience function that adds path to
+// ImportPkgs, the set of initial source packages located relative to
+// $GOPATH.  The package will be augmented by any *_test.go files in
+// its directory that contain a "package x" (not "package x_test")
+// declaration.
+//
+// In addition, if any *_test.go files contain a "package x_test"
+// declaration, an additional package comprising just those files will
+// be added to CreatePkgs.
+func (conf *Config) ImportWithTests(path string) { conf.addImport(path, true) }
+
+// Import is a convenience function that adds path to ImportPkgs, the
+// set of initial packages that will be imported from source.
+func (conf *Config) Import(path string) { conf.addImport(path, false) }
+
+func (conf *Config) addImport(path string, tests bool) {
+	if path == "C" {
+		return // ignore; not a real package
+	}
+	if conf.ImportPkgs == nil {
+		conf.ImportPkgs = make(map[string]bool)
+	}
+	conf.ImportPkgs[path] = conf.ImportPkgs[path] || tests
+}
+
+// PathEnclosingInterval returns the PackageInfo and ast.Node that
+// contain source interval [start, end), and all the node's ancestors
+// up to the AST root.  It searches all ast.Files of all packages in prog.
+// exact is defined as for astutil.PathEnclosingInterval.
+//
+// The zero value is returned if not found.
+func (prog *Program) PathEnclosingInterval(start, end token.Pos) (pkg *PackageInfo, path []ast.Node, exact bool) {
+	for _, info := range prog.AllPackages {
+		for _, f := range info.Files {
+			if f.Pos() == token.NoPos {
+				// This can happen if the parser saw
+				// too many errors and bailed out.
+				// (Use parser.AllErrors to prevent that.)
+				continue
+			}
+			if !tokenFileContainsPos(prog.Fset.File(f.Pos()), start) {
+				continue
+			}
+			if path, exact := astutil.PathEnclosingInterval(f, start, end); path != nil {
+				return info, path, exact
+			}
+		}
+	}
+	return nil, nil, false
+}
+
+// InitialPackages returns a new slice containing the set of initial
+// packages (Created + Imported) in unspecified order.
+func (prog *Program) InitialPackages() []*PackageInfo {
+	infos := make([]*PackageInfo, 0, len(prog.Created)+len(prog.Imported))
+	infos = append(infos, prog.Created...)
+	for _, info := range prog.Imported {
+		infos = append(infos, info)
+	}
+	return infos
+}
+
+// Package returns the ASTs and results of type checking for the
+// specified package.
+func (prog *Program) Package(path string) *PackageInfo {
+	if info, ok := prog.AllPackages[prog.importMap[path]]; ok {
+		return info
+	}
+	for _, info := range prog.Created {
+		if path == info.Pkg.Path() {
+			return info
+		}
+	}
+	return nil
+}
+
+// ---------- Implementation ----------
+
+// importer holds the working state of the algorithm.
+type importer struct {
+	conf  *Config   // the client configuration
+	start time.Time // for logging
+
+	progMu sync.Mutex // guards prog
+	prog   *Program   // the resulting program
+
+	// findpkg is a memoization of FindPackage.
+	findpkgMu sync.Mutex // guards findpkg
+	findpkg   map[findpkgKey]*findpkgValue
+
+	importedMu sync.Mutex             // guards imported
+	imported   map[string]*importInfo // all imported packages (incl. failures) by import path
+
+	// import dependency graph: graph[x][y] => x imports y
+	//
+	// Since non-importable packages cannot be cyclic, we ignore
+	// their imports, thus we only need the subgraph over importable
+	// packages.  Nodes are identified by their import paths.
+	graphMu sync.Mutex
+	graph   map[string]map[string]bool
+}
+
+type findpkgKey struct {
+	importPath string
+	fromDir    string
+	mode       build.ImportMode
+}
+
+type findpkgValue struct {
+	ready chan struct{} // closed to broadcast readiness
+	bp    *build.Package
+	err   error
+}
+
+// importInfo tracks the success or failure of a single import.
+//
+// Upon completion, exactly one of info and err is non-nil:
+// info on successful creation of a package, err otherwise.
+// A successful package may still contain type errors.
+type importInfo struct {
+	path     string        // import path
+	info     *PackageInfo  // results of typechecking (including errors)
+	complete chan struct{} // closed to broadcast that info is set.
+}
+
+// awaitCompletion blocks until ii is complete,
+// i.e. the info field is safe to inspect.
+func (ii *importInfo) awaitCompletion() {
+	<-ii.complete // wait for close
+}
+
+// Complete marks ii as complete.
+// Its info and err fields will not be subsequently updated.
+func (ii *importInfo) Complete(info *PackageInfo) {
+	if info == nil {
+		panic("info == nil")
+	}
+	ii.info = info
+	close(ii.complete)
+}
+
+type importError struct {
+	path string // import path
+	err  error  // reason for failure to create a package
+}
+
+// Load creates the initial packages specified by conf.{Create,Import}Pkgs,
+// loading their dependencies packages as needed.
+//
+// On success, Load returns a Program containing a PackageInfo for
+// each package.  On failure, it returns an error.
+//
+// If AllowErrors is true, Load will return a Program even if some
+// packages contained I/O, parser or type errors, or if dependencies
+// were missing.  (Such errors are accessible via PackageInfo.Errors.  If
+// false, Load will fail if any package had an error.
+//
+// It is an error if no packages were loaded.
+func (conf *Config) Load() (*Program, error) {
+	// Create a simple default error handler for parse/type errors.
+	if conf.TypeChecker.Error == nil {
+		conf.TypeChecker.Error = func(e error) { fmt.Fprintln(os.Stderr, e) }
+	}
+
+	// Set default working directory for relative package references.
+	if conf.Cwd == "" {
+		var err error
+		conf.Cwd, err = os.Getwd()
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	// Install default FindPackage hook using go/build logic.
+	if conf.FindPackage == nil {
+		conf.FindPackage = (*build.Context).Import
+	}
+
+	prog := &Program{
+		Fset:        conf.fset(),
+		Imported:    make(map[string]*PackageInfo),
+		importMap:   make(map[string]*types.Package),
+		AllPackages: make(map[*types.Package]*PackageInfo),
+	}
+
+	imp := importer{
+		conf:     conf,
+		prog:     prog,
+		findpkg:  make(map[findpkgKey]*findpkgValue),
+		imported: make(map[string]*importInfo),
+		start:    time.Now(),
+		graph:    make(map[string]map[string]bool),
+	}
+
+	// -- loading proper (concurrent phase) --------------------------------
+
+	var errpkgs []string // packages that contained errors
+
+	// Load the initially imported packages and their dependencies,
+	// in parallel.
+	// No vendor check on packages imported from the command line.
+	infos, importErrors := imp.importAll("", conf.Cwd, conf.ImportPkgs, ignoreVendor)
+	for _, ie := range importErrors {
+		conf.TypeChecker.Error(ie.err) // failed to create package
+		errpkgs = append(errpkgs, ie.path)
+	}
+	for _, info := range infos {
+		prog.Imported[info.Pkg.Path()] = info
+	}
+
+	// Augment the designated initial packages by their tests.
+	// Dependencies are loaded in parallel.
+	var xtestPkgs []*build.Package
+	for importPath, augment := range conf.ImportPkgs {
+		if !augment {
+			continue
+		}
+
+		// No vendor check on packages imported from command line.
+		bp, err := imp.findPackage(importPath, conf.Cwd, ignoreVendor)
+		if err != nil {
+			// Package not found, or can't even parse package declaration.
+			// Already reported by previous loop; ignore it.
+			continue
+		}
+
+		// Needs external test package?
+		if len(bp.XTestGoFiles) > 0 {
+			xtestPkgs = append(xtestPkgs, bp)
+		}
+
+		// Consult the cache using the canonical package path.
+		path := bp.ImportPath
+		imp.importedMu.Lock() // (unnecessary, we're sequential here)
+		ii, ok := imp.imported[path]
+		// Paranoid checks added due to issue #11012.
+		if !ok {
+			// Unreachable.
+			// The previous loop called importAll and thus
+			// startLoad for each path in ImportPkgs, which
+			// populates imp.imported[path] with a non-zero value.
+			panic(fmt.Sprintf("imported[%q] not found", path))
+		}
+		if ii == nil {
+			// Unreachable.
+			// The ii values in this loop are the same as in
+			// the previous loop, which enforced the invariant
+			// that at least one of ii.err and ii.info is non-nil.
+			panic(fmt.Sprintf("imported[%q] == nil", path))
+		}
+		if ii.info == nil {
+			// Unreachable.
+			// awaitCompletion has the postcondition
+			// ii.info != nil.
+			panic(fmt.Sprintf("imported[%q].info = nil", path))
+		}
+		info := ii.info
+		imp.importedMu.Unlock()
+
+		// Parse the in-package test files.
+		files, errs := imp.conf.parsePackageFiles(bp, 't')
+		for _, err := range errs {
+			info.appendError(err)
+		}
+
+		// The test files augmenting package P cannot be imported,
+		// but may import packages that import P,
+		// so we must disable the cycle check.
+		imp.addFiles(info, files, false)
+	}
+
+	createPkg := func(path, dir string, files []*ast.File, errs []error) {
+		info := imp.newPackageInfo(path, dir)
+		for _, err := range errs {
+			info.appendError(err)
+		}
+
+		// Ad hoc packages are non-importable,
+		// so no cycle check is needed.
+		// addFiles loads dependencies in parallel.
+		imp.addFiles(info, files, false)
+		prog.Created = append(prog.Created, info)
+	}
+
+	// Create packages specified by conf.CreatePkgs.
+	for _, cp := range conf.CreatePkgs {
+		files, errs := parseFiles(conf.fset(), conf.build(), nil, conf.Cwd, cp.Filenames, conf.ParserMode)
+		files = append(files, cp.Files...)
+
+		path := cp.Path
+		if path == "" {
+			if len(files) > 0 {
+				path = files[0].Name.Name
+			} else {
+				path = "(unnamed)"
+			}
+		}
+
+		dir := conf.Cwd
+		if len(files) > 0 && files[0].Pos().IsValid() {
+			dir = filepath.Dir(conf.fset().File(files[0].Pos()).Name())
+		}
+		createPkg(path, dir, files, errs)
+	}
+
+	// Create external test packages.
+	sort.Sort(byImportPath(xtestPkgs))
+	for _, bp := range xtestPkgs {
+		files, errs := imp.conf.parsePackageFiles(bp, 'x')
+		createPkg(bp.ImportPath+"_test", bp.Dir, files, errs)
+	}
+
+	// -- finishing up (sequential) ----------------------------------------
+
+	if len(prog.Imported)+len(prog.Created) == 0 {
+		return nil, errors.New("no initial packages were loaded")
+	}
+
+	// Create infos for indirectly imported packages.
+	// e.g. incomplete packages without syntax, loaded from export data.
+	for _, obj := range prog.importMap {
+		info := prog.AllPackages[obj]
+		if info == nil {
+			prog.AllPackages[obj] = &PackageInfo{Pkg: obj, Importable: true}
+		} else {
+			// finished
+			info.checker = nil
+			info.errorFunc = nil
+		}
+	}
+
+	if !conf.AllowErrors {
+		// Report errors in indirectly imported packages.
+		for _, info := range prog.AllPackages {
+			if len(info.Errors) > 0 {
+				errpkgs = append(errpkgs, info.Pkg.Path())
+			}
+		}
+		if errpkgs != nil {
+			var more string
+			if len(errpkgs) > 3 {
+				more = fmt.Sprintf(" and %d more", len(errpkgs)-3)
+				errpkgs = errpkgs[:3]
+			}
+			return nil, fmt.Errorf("couldn't load packages due to errors: %s%s",
+				strings.Join(errpkgs, ", "), more)
+		}
+	}
+
+	markErrorFreePackages(prog.AllPackages)
+
+	return prog, nil
+}
+
+type byImportPath []*build.Package
+
+func (b byImportPath) Len() int           { return len(b) }
+func (b byImportPath) Less(i, j int) bool { return b[i].ImportPath < b[j].ImportPath }
+func (b byImportPath) Swap(i, j int)      { b[i], b[j] = b[j], b[i] }
+
+// markErrorFreePackages sets the TransitivelyErrorFree flag on all
+// applicable packages.
+func markErrorFreePackages(allPackages map[*types.Package]*PackageInfo) {
+	// Build the transpose of the import graph.
+	importedBy := make(map[*types.Package]map[*types.Package]bool)
+	for P := range allPackages {
+		for _, Q := range P.Imports() {
+			clients, ok := importedBy[Q]
+			if !ok {
+				clients = make(map[*types.Package]bool)
+				importedBy[Q] = clients
+			}
+			clients[P] = true
+		}
+	}
+
+	// Find all packages reachable from some error package.
+	reachable := make(map[*types.Package]bool)
+	var visit func(*types.Package)
+	visit = func(p *types.Package) {
+		if !reachable[p] {
+			reachable[p] = true
+			for q := range importedBy[p] {
+				visit(q)
+			}
+		}
+	}
+	for _, info := range allPackages {
+		if len(info.Errors) > 0 {
+			visit(info.Pkg)
+		}
+	}
+
+	// Mark the others as "transitively error-free".
+	for _, info := range allPackages {
+		if !reachable[info.Pkg] {
+			info.TransitivelyErrorFree = true
+		}
+	}
+}
+
+// build returns the effective build context.
+func (conf *Config) build() *build.Context {
+	if conf.Build != nil {
+		return conf.Build
+	}
+	return &build.Default
+}
+
+// parsePackageFiles enumerates the files belonging to package path,
+// then loads, parses and returns them, plus a list of I/O or parse
+// errors that were encountered.
+//
+// 'which' indicates which files to include:
+//
+//	'g': include non-test *.go source files (GoFiles + processed CgoFiles)
+//	't': include in-package *_test.go source files (TestGoFiles)
+//	'x': include external *_test.go source files. (XTestGoFiles)
+func (conf *Config) parsePackageFiles(bp *build.Package, which rune) ([]*ast.File, []error) {
+	if bp.ImportPath == "unsafe" {
+		return nil, nil
+	}
+	var filenames []string
+	switch which {
+	case 'g':
+		filenames = bp.GoFiles
+	case 't':
+		filenames = bp.TestGoFiles
+	case 'x':
+		filenames = bp.XTestGoFiles
+	default:
+		panic(which)
+	}
+
+	files, errs := parseFiles(conf.fset(), conf.build(), conf.DisplayPath, bp.Dir, filenames, conf.ParserMode)
+
+	// Preprocess CgoFiles and parse the outputs (sequentially).
+	if which == 'g' && bp.CgoFiles != nil {
+		cgofiles, err := cgo.ProcessFiles(bp, conf.fset(), conf.DisplayPath, conf.ParserMode)
+		if err != nil {
+			errs = append(errs, err)
+		} else {
+			files = append(files, cgofiles...)
+		}
+	}
+
+	return files, errs
+}
+
+// doImport imports the package denoted by path.
+// It implements the types.Importer signature.
+//
+// It returns an error if a package could not be created
+// (e.g. go/build or parse error), but type errors are reported via
+// the types.Config.Error callback (the first of which is also saved
+// in the package's PackageInfo).
+//
+// Idempotent.
+func (imp *importer) doImport(from *PackageInfo, to string) (*types.Package, error) {
+	if to == "C" {
+		// This should be unreachable, but ad hoc packages are
+		// not currently subject to cgo preprocessing.
+		// See https://golang.org/issue/11627.
+		return nil, fmt.Errorf(`the loader doesn't cgo-process ad hoc packages like %q; see Go issue 11627`,
+			from.Pkg.Path())
+	}
+
+	bp, err := imp.findPackage(to, from.dir, 0)
+	if err != nil {
+		return nil, err
+	}
+
+	// The standard unsafe package is handled specially,
+	// and has no PackageInfo.
+	if bp.ImportPath == "unsafe" {
+		return types.Unsafe, nil
+	}
+
+	// Look for the package in the cache using its canonical path.
+	path := bp.ImportPath
+	imp.importedMu.Lock()
+	ii := imp.imported[path]
+	imp.importedMu.Unlock()
+	if ii == nil {
+		panic("internal error: unexpected import: " + path)
+	}
+	if ii.info != nil {
+		return ii.info.Pkg, nil
+	}
+
+	// Import of incomplete package: this indicates a cycle.
+	fromPath := from.Pkg.Path()
+	if cycle := imp.findPath(path, fromPath); cycle != nil {
+		// Normalize cycle: start from alphabetically largest node.
+		pos, start := -1, ""
+		for i, s := range cycle {
+			if pos < 0 || s > start {
+				pos, start = i, s
+			}
+		}
+		cycle = append(cycle, cycle[:pos]...)[pos:] // rotate cycle to start from largest
+		cycle = append(cycle, cycle[0])             // add start node to end to show cycliness
+		return nil, fmt.Errorf("import cycle: %s", strings.Join(cycle, " -> "))
+	}
+
+	panic("internal error: import of incomplete (yet acyclic) package: " + fromPath)
+}
+
+// findPackage locates the package denoted by the importPath in the
+// specified directory.
+func (imp *importer) findPackage(importPath, fromDir string, mode build.ImportMode) (*build.Package, error) {
+	// We use a non-blocking duplicate-suppressing cache (gopl.io §9.7)
+	// to avoid holding the lock around FindPackage.
+	key := findpkgKey{importPath, fromDir, mode}
+	imp.findpkgMu.Lock()
+	v, ok := imp.findpkg[key]
+	if ok {
+		// cache hit
+		imp.findpkgMu.Unlock()
+
+		<-v.ready // wait for entry to become ready
+	} else {
+		// Cache miss: this goroutine becomes responsible for
+		// populating the map entry and broadcasting its readiness.
+		v = &findpkgValue{ready: make(chan struct{})}
+		imp.findpkg[key] = v
+		imp.findpkgMu.Unlock()
+
+		ioLimit <- true
+		v.bp, v.err = imp.conf.FindPackage(imp.conf.build(), importPath, fromDir, mode)
+		<-ioLimit
+
+		if _, ok := v.err.(*build.NoGoError); ok {
+			v.err = nil // empty directory is not an error
+		}
+
+		close(v.ready) // broadcast ready condition
+	}
+	return v.bp, v.err
+}
+
+// importAll loads, parses, and type-checks the specified packages in
+// parallel and returns their completed importInfos in unspecified order.
+//
+// fromPath is the package path of the importing package, if it is
+// importable, "" otherwise.  It is used for cycle detection.
+//
+// fromDir is the directory containing the import declaration that
+// caused these imports.
+func (imp *importer) importAll(fromPath, fromDir string, imports map[string]bool, mode build.ImportMode) (infos []*PackageInfo, errors []importError) {
+	if fromPath != "" {
+		// We're loading a set of imports.
+		//
+		// We must record graph edges from the importing package
+		// to its dependencies, and check for cycles.
+		imp.graphMu.Lock()
+		deps, ok := imp.graph[fromPath]
+		if !ok {
+			deps = make(map[string]bool)
+			imp.graph[fromPath] = deps
+		}
+		for importPath := range imports {
+			deps[importPath] = true
+		}
+		imp.graphMu.Unlock()
+	}
+
+	var pending []*importInfo
+	for importPath := range imports {
+		if fromPath != "" {
+			if cycle := imp.findPath(importPath, fromPath); cycle != nil {
+				// Cycle-forming import: we must not check it
+				// since it would deadlock.
+				if trace {
+					fmt.Fprintf(os.Stderr, "import cycle: %q\n", cycle)
+				}
+				continue
+			}
+		}
+		bp, err := imp.findPackage(importPath, fromDir, mode)
+		if err != nil {
+			errors = append(errors, importError{
+				path: importPath,
+				err:  err,
+			})
+			continue
+		}
+		pending = append(pending, imp.startLoad(bp))
+	}
+
+	for _, ii := range pending {
+		ii.awaitCompletion()
+		infos = append(infos, ii.info)
+	}
+
+	return infos, errors
+}
+
+// findPath returns an arbitrary path from 'from' to 'to' in the import
+// graph, or nil if there was none.
+func (imp *importer) findPath(from, to string) []string {
+	imp.graphMu.Lock()
+	defer imp.graphMu.Unlock()
+
+	seen := make(map[string]bool)
+	var search func(stack []string, importPath string) []string
+	search = func(stack []string, importPath string) []string {
+		if !seen[importPath] {
+			seen[importPath] = true
+			stack = append(stack, importPath)
+			if importPath == to {
+				return stack
+			}
+			for x := range imp.graph[importPath] {
+				if p := search(stack, x); p != nil {
+					return p
+				}
+			}
+		}
+		return nil
+	}
+	return search(make([]string, 0, 20), from)
+}
+
+// startLoad initiates the loading, parsing and type-checking of the
+// specified package and its dependencies, if it has not already begun.
+//
+// It returns an importInfo, not necessarily in a completed state.  The
+// caller must call awaitCompletion() before accessing its info field.
+//
+// startLoad is concurrency-safe and idempotent.
+func (imp *importer) startLoad(bp *build.Package) *importInfo {
+	path := bp.ImportPath
+	imp.importedMu.Lock()
+	ii, ok := imp.imported[path]
+	if !ok {
+		ii = &importInfo{path: path, complete: make(chan struct{})}
+		imp.imported[path] = ii
+		go func() {
+			info := imp.load(bp)
+			ii.Complete(info)
+		}()
+	}
+	imp.importedMu.Unlock()
+
+	return ii
+}
+
+// load implements package loading by parsing Go source files
+// located by go/build.
+func (imp *importer) load(bp *build.Package) *PackageInfo {
+	info := imp.newPackageInfo(bp.ImportPath, bp.Dir)
+	info.Importable = true
+	files, errs := imp.conf.parsePackageFiles(bp, 'g')
+	for _, err := range errs {
+		info.appendError(err)
+	}
+
+	imp.addFiles(info, files, true)
+
+	imp.progMu.Lock()
+	imp.prog.importMap[bp.ImportPath] = info.Pkg
+	imp.progMu.Unlock()
+
+	return info
+}
+
+// addFiles adds and type-checks the specified files to info, loading
+// their dependencies if needed.  The order of files determines the
+// package initialization order.  It may be called multiple times on the
+// same package.  Errors are appended to the info.Errors field.
+//
+// cycleCheck determines whether the imports within files create
+// dependency edges that should be checked for potential cycles.
+func (imp *importer) addFiles(info *PackageInfo, files []*ast.File, cycleCheck bool) {
+	// Ensure the dependencies are loaded, in parallel.
+	var fromPath string
+	if cycleCheck {
+		fromPath = info.Pkg.Path()
+	}
+	// TODO(adonovan): opt: make the caller do scanImports.
+	// Callers with a build.Package can skip it.
+	imp.importAll(fromPath, info.dir, scanImports(files), 0)
+
+	if trace {
+		fmt.Fprintf(os.Stderr, "%s: start %q (%d)\n",
+			time.Since(imp.start), info.Pkg.Path(), len(files))
+	}
+
+	// Don't call checker.Files on Unsafe, even with zero files,
+	// because it would mutate the package, which is a global.
+	if info.Pkg == types.Unsafe {
+		if len(files) > 0 {
+			panic(`"unsafe" package contains unexpected files`)
+		}
+	} else {
+		// Ignore the returned (first) error since we
+		// already collect them all in the PackageInfo.
+		info.checker.Files(files)
+		info.Files = append(info.Files, files...)
+	}
+
+	if imp.conf.AfterTypeCheck != nil {
+		imp.conf.AfterTypeCheck(info, files)
+	}
+
+	if trace {
+		fmt.Fprintf(os.Stderr, "%s: stop %q\n",
+			time.Since(imp.start), info.Pkg.Path())
+	}
+}
+
+func (imp *importer) newPackageInfo(path, dir string) *PackageInfo {
+	var pkg *types.Package
+	if path == "unsafe" {
+		pkg = types.Unsafe
+	} else {
+		pkg = types.NewPackage(path, "")
+	}
+	info := &PackageInfo{
+		Pkg: pkg,
+		Info: types.Info{
+			Types:      make(map[ast.Expr]types.TypeAndValue),
+			Defs:       make(map[*ast.Ident]types.Object),
+			Uses:       make(map[*ast.Ident]types.Object),
+			Implicits:  make(map[ast.Node]types.Object),
+			Instances:  make(map[*ast.Ident]types.Instance),
+			Scopes:     make(map[ast.Node]*types.Scope),
+			Selections: make(map[*ast.SelectorExpr]*types.Selection),
+		},
+		errorFunc: imp.conf.TypeChecker.Error,
+		dir:       dir,
+	}
+	versions.InitFileVersions(&info.Info)
+
+	// Copy the types.Config so we can vary it across PackageInfos.
+	tc := imp.conf.TypeChecker
+	tc.IgnoreFuncBodies = false
+	if f := imp.conf.TypeCheckFuncBodies; f != nil {
+		tc.IgnoreFuncBodies = !f(path)
+	}
+	tc.Importer = closure{imp, info}
+	tc.Error = info.appendError // appendError wraps the user's Error function
+
+	info.checker = types.NewChecker(&tc, imp.conf.fset(), pkg, &info.Info)
+	imp.progMu.Lock()
+	imp.prog.AllPackages[pkg] = info
+	imp.progMu.Unlock()
+	return info
+}
+
+type closure struct {
+	imp  *importer
+	info *PackageInfo
+}
+
+func (c closure) Import(to string) (*types.Package, error) { return c.imp.doImport(c.info, to) }
diff --git a/vendor/golang.org/x/tools/go/loader/util.go b/vendor/golang.org/x/tools/go/loader/util.go
new file mode 100644
index 0000000..3a80aca
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/loader/util.go
@@ -0,0 +1,123 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package loader
+
+import (
+	"go/ast"
+	"go/build"
+	"go/parser"
+	"go/token"
+	"io"
+	"os"
+	"strconv"
+	"sync"
+
+	"golang.org/x/tools/go/buildutil"
+)
+
+// We use a counting semaphore to limit
+// the number of parallel I/O calls per process.
+var ioLimit = make(chan bool, 10)
+
+// parseFiles parses the Go source files within directory dir and
+// returns the ASTs of the ones that could be at least partially parsed,
+// along with a list of I/O and parse errors encountered.
+//
+// I/O is done via ctxt, which may specify a virtual file system.
+// displayPath is used to transform the filenames attached to the ASTs.
+func parseFiles(fset *token.FileSet, ctxt *build.Context, displayPath func(string) string, dir string, files []string, mode parser.Mode) ([]*ast.File, []error) {
+	if displayPath == nil {
+		displayPath = func(path string) string { return path }
+	}
+	var wg sync.WaitGroup
+	n := len(files)
+	parsed := make([]*ast.File, n)
+	errors := make([]error, n)
+	for i, file := range files {
+		if !buildutil.IsAbsPath(ctxt, file) {
+			file = buildutil.JoinPath(ctxt, dir, file)
+		}
+		wg.Add(1)
+		go func(i int, file string) {
+			ioLimit <- true // wait
+			defer func() {
+				wg.Done()
+				<-ioLimit // signal
+			}()
+			var rd io.ReadCloser
+			var err error
+			if ctxt.OpenFile != nil {
+				rd, err = ctxt.OpenFile(file)
+			} else {
+				rd, err = os.Open(file)
+			}
+			if err != nil {
+				errors[i] = err // open failed
+				return
+			}
+
+			// ParseFile may return both an AST and an error.
+			parsed[i], errors[i] = parser.ParseFile(fset, displayPath(file), rd, mode)
+			rd.Close()
+		}(i, file)
+	}
+	wg.Wait()
+
+	// Eliminate nils, preserving order.
+	var o int
+	for _, f := range parsed {
+		if f != nil {
+			parsed[o] = f
+			o++
+		}
+	}
+	parsed = parsed[:o]
+
+	o = 0
+	for _, err := range errors {
+		if err != nil {
+			errors[o] = err
+			o++
+		}
+	}
+	errors = errors[:o]
+
+	return parsed, errors
+}
+
+// scanImports returns the set of all import paths from all
+// import specs in the specified files.
+func scanImports(files []*ast.File) map[string]bool {
+	imports := make(map[string]bool)
+	for _, f := range files {
+		for _, decl := range f.Decls {
+			if decl, ok := decl.(*ast.GenDecl); ok && decl.Tok == token.IMPORT {
+				for _, spec := range decl.Specs {
+					spec := spec.(*ast.ImportSpec)
+
+					// NB: do not assume the program is well-formed!
+					path, err := strconv.Unquote(spec.Path.Value)
+					if err != nil {
+						continue // quietly ignore the error
+					}
+					if path == "C" {
+						continue // skip pseudopackage
+					}
+					imports[path] = true
+				}
+			}
+		}
+	}
+	return imports
+}
+
+// ---------- Internal helpers ----------
+
+// TODO(adonovan): make this a method: func (*token.File) Contains(token.Pos)
+func tokenFileContainsPos(f *token.File, pos token.Pos) bool {
+	p := int(pos)
+	base := f.Base()
+	return base <= p && p < base+f.Size()
+}
diff --git a/vendor/golang.org/x/tools/go/packages/doc.go b/vendor/golang.org/x/tools/go/packages/doc.go
new file mode 100644
index 0000000..3531ac8
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/packages/doc.go
@@ -0,0 +1,242 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+/*
+Package packages loads Go packages for inspection and analysis.
+
+The [Load] function takes as input a list of patterns and returns a
+list of [Package] values describing individual packages matched by those
+patterns.
+A [Config] specifies configuration options, the most important of which is
+the [LoadMode], which controls the amount of detail in the loaded packages.
+
+Load passes most patterns directly to the underlying build tool.
+The default build tool is the go command.
+Its supported patterns are described at
+https://pkg.go.dev/cmd/go#hdr-Package_lists_and_patterns.
+Other build systems may be supported by providing a "driver";
+see [The driver protocol].
+
+All patterns with the prefix "query=", where query is a
+non-empty string of letters from [a-z], are reserved and may be
+interpreted as query operators.
+
+Two query operators are currently supported: "file" and "pattern".
+
+The query "file=path/to/file.go" matches the package or packages enclosing
+the Go source file path/to/file.go.  For example "file=~/go/src/fmt/print.go"
+might return the packages "fmt" and "fmt [fmt.test]".
+
+The query "pattern=string" causes "string" to be passed directly to
+the underlying build tool. In most cases this is unnecessary,
+but an application can use Load("pattern=" + x) as an escaping mechanism
+to ensure that x is not interpreted as a query operator if it contains '='.
+
+All other query operators are reserved for future use and currently
+cause Load to report an error.
+
+The Package struct provides basic information about the package, including
+
+  - ID, a unique identifier for the package in the returned set;
+  - GoFiles, the names of the package's Go source files;
+  - Imports, a map from source import strings to the Packages they name;
+  - Types, the type information for the package's exported symbols;
+  - Syntax, the parsed syntax trees for the package's source code; and
+  - TypesInfo, the result of a complete type-check of the package syntax trees.
+
+(See the documentation for type Package for the complete list of fields
+and more detailed descriptions.)
+
+For example,
+
+	Load(nil, "bytes", "unicode...")
+
+returns four Package structs describing the standard library packages
+bytes, unicode, unicode/utf16, and unicode/utf8. Note that one pattern
+can match multiple packages and that a package might be matched by
+multiple patterns: in general it is not possible to determine which
+packages correspond to which patterns.
+
+Note that the list returned by Load contains only the packages matched
+by the patterns. Their dependencies can be found by walking the import
+graph using the Imports fields.
+
+The Load function can be configured by passing a pointer to a Config as
+the first argument. A nil Config is equivalent to the zero Config, which
+causes Load to run in LoadFiles mode, collecting minimal information.
+See the documentation for type Config for details.
+
+As noted earlier, the Config.Mode controls the amount of detail
+reported about the loaded packages. See the documentation for type LoadMode
+for details.
+
+Most tools should pass their command-line arguments (after any flags)
+uninterpreted to [Load], so that it can interpret them
+according to the conventions of the underlying build system.
+
+See the Example function for typical usage.
+
+# The driver protocol
+
+[Load] may be used to load Go packages even in Go projects that use
+alternative build systems, by installing an appropriate "driver"
+program for the build system and specifying its location in the
+GOPACKAGESDRIVER environment variable.
+For example,
+https://github.com/bazelbuild/rules_go/wiki/Editor-and-tool-integration
+explains how to use the driver for Bazel.
+
+The driver program is responsible for interpreting patterns in its
+preferred notation and reporting information about the packages that
+those patterns identify. Drivers must also support the special "file="
+and "pattern=" patterns described above.
+
+The patterns are provided as positional command-line arguments. A
+JSON-encoded [DriverRequest] message providing additional information
+is written to the driver's standard input. The driver must write a
+JSON-encoded [DriverResponse] message to its standard output. (This
+message differs from the JSON schema produced by 'go list'.)
+*/
+package packages // import "golang.org/x/tools/go/packages"
+
+/*
+
+Motivation and design considerations
+
+The new package's design solves problems addressed by two existing
+packages: go/build, which locates and describes packages, and
+golang.org/x/tools/go/loader, which loads, parses and type-checks them.
+The go/build.Package structure encodes too much of the 'go build' way
+of organizing projects, leaving us in need of a data type that describes a
+package of Go source code independent of the underlying build system.
+We wanted something that works equally well with go build and vgo, and
+also other build systems such as Bazel and Blaze, making it possible to
+construct analysis tools that work in all these environments.
+Tools such as errcheck and staticcheck were essentially unavailable to
+the Go community at Google, and some of Google's internal tools for Go
+are unavailable externally.
+This new package provides a uniform way to obtain package metadata by
+querying each of these build systems, optionally supporting their
+preferred command-line notations for packages, so that tools integrate
+neatly with users' build environments. The Metadata query function
+executes an external query tool appropriate to the current workspace.
+
+Loading packages always returns the complete import graph "all the way down",
+even if all you want is information about a single package, because the query
+mechanisms of all the build systems we currently support ({go,vgo} list, and
+blaze/bazel aspect-based query) cannot provide detailed information
+about one package without visiting all its dependencies too, so there is
+no additional asymptotic cost to providing transitive information.
+(This property might not be true of a hypothetical 5th build system.)
+
+In calls to TypeCheck, all initial packages, and any package that
+transitively depends on one of them, must be loaded from source.
+Consider A->B->C->D->E: if A,C are initial, A,B,C must be loaded from
+source; D may be loaded from export data, and E may not be loaded at all
+(though it's possible that D's export data mentions it, so a
+types.Package may be created for it and exposed.)
+
+The old loader had a feature to suppress type-checking of function
+bodies on a per-package basis, primarily intended to reduce the work of
+obtaining type information for imported packages. Now that imports are
+satisfied by export data, the optimization no longer seems necessary.
+
+Despite some early attempts, the old loader did not exploit export data,
+instead always using the equivalent of WholeProgram mode. This was due
+to the complexity of mixing source and export data packages (now
+resolved by the upward traversal mentioned above), and because export data
+files were nearly always missing or stale. Now that 'go build' supports
+caching, all the underlying build systems can guarantee to produce
+export data in a reasonable (amortized) time.
+
+Test "main" packages synthesized by the build system are now reported as
+first-class packages, avoiding the need for clients (such as go/ssa) to
+reinvent this generation logic.
+
+One way in which go/packages is simpler than the old loader is in its
+treatment of in-package tests. In-package tests are packages that
+consist of all the files of the library under test, plus the test files.
+The old loader constructed in-package tests by a two-phase process of
+mutation called "augmentation": first it would construct and type check
+all the ordinary library packages and type-check the packages that
+depend on them; then it would add more (test) files to the package and
+type-check again. This two-phase approach had four major problems:
+1) in processing the tests, the loader modified the library package,
+   leaving no way for a client application to see both the test
+   package and the library package; one would mutate into the other.
+2) because test files can declare additional methods on types defined in
+   the library portion of the package, the dispatch of method calls in
+   the library portion was affected by the presence of the test files.
+   This should have been a clue that the packages were logically
+   different.
+3) this model of "augmentation" assumed at most one in-package test
+   per library package, which is true of projects using 'go build',
+   but not other build systems.
+4) because of the two-phase nature of test processing, all packages that
+   import the library package had to be processed before augmentation,
+   forcing a "one-shot" API and preventing the client from calling Load
+   in several times in sequence as is now possible in WholeProgram mode.
+   (TypeCheck mode has a similar one-shot restriction for a different reason.)
+
+Early drafts of this package supported "multi-shot" operation.
+Although it allowed clients to make a sequence of calls (or concurrent
+calls) to Load, building up the graph of Packages incrementally,
+it was of marginal value: it complicated the API
+(since it allowed some options to vary across calls but not others),
+it complicated the implementation,
+it cannot be made to work in Types mode, as explained above,
+and it was less efficient than making one combined call (when this is possible).
+Among the clients we have inspected, none made multiple calls to load
+but could not be easily and satisfactorily modified to make only a single call.
+However, applications changes may be required.
+For example, the ssadump command loads the user-specified packages
+and in addition the runtime package.  It is tempting to simply append
+"runtime" to the user-provided list, but that does not work if the user
+specified an ad-hoc package such as [a.go b.go].
+Instead, ssadump no longer requests the runtime package,
+but seeks it among the dependencies of the user-specified packages,
+and emits an error if it is not found.
+
+Questions & Tasks
+
+- Add GOARCH/GOOS?
+  They are not portable concepts, but could be made portable.
+  Our goal has been to allow users to express themselves using the conventions
+  of the underlying build system: if the build system honors GOARCH
+  during a build and during a metadata query, then so should
+  applications built atop that query mechanism.
+  Conversely, if the target architecture of the build is determined by
+  command-line flags, the application can pass the relevant
+  flags through to the build system using a command such as:
+    myapp -query_flag="--cpu=amd64" -query_flag="--os=darwin"
+  However, this approach is low-level, unwieldy, and non-portable.
+  GOOS and GOARCH seem important enough to warrant a dedicated option.
+
+- How should we handle partial failures such as a mixture of good and
+  malformed patterns, existing and non-existent packages, successful and
+  failed builds, import failures, import cycles, and so on, in a call to
+  Load?
+
+- Support bazel, blaze, and go1.10 list, not just go1.11 list.
+
+- Handle (and test) various partial success cases, e.g.
+  a mixture of good packages and:
+  invalid patterns
+  nonexistent packages
+  empty packages
+  packages with malformed package or import declarations
+  unreadable files
+  import cycles
+  other parse errors
+  type errors
+  Make sure we record errors at the correct place in the graph.
+
+- Missing packages among initial arguments are not reported.
+  Return bogus packages for them, like golist does.
+
+- "undeclared name" errors (for example) are reported out of source file
+  order. I suspect this is due to the breadth-first resolution now used
+  by go/types. Is that a bug? Discuss with gri.
+
+*/
diff --git a/vendor/golang.org/x/tools/go/packages/external.go b/vendor/golang.org/x/tools/go/packages/external.go
new file mode 100644
index 0000000..c2b4b71
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/packages/external.go
@@ -0,0 +1,156 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packages
+
+// This file defines the protocol that enables an external "driver"
+// tool to supply package metadata in place of 'go list'.
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"os"
+	"os/exec"
+	"strings"
+)
+
+// DriverRequest defines the schema of a request for package metadata
+// from an external driver program. The JSON-encoded DriverRequest
+// message is provided to the driver program's standard input. The
+// query patterns are provided as command-line arguments.
+//
+// See the package documentation for an overview.
+type DriverRequest struct {
+	Mode LoadMode `json:"mode"`
+
+	// Env specifies the environment the underlying build system should be run in.
+	Env []string `json:"env"`
+
+	// BuildFlags are flags that should be passed to the underlying build system.
+	BuildFlags []string `json:"build_flags"`
+
+	// Tests specifies whether the patterns should also return test packages.
+	Tests bool `json:"tests"`
+
+	// Overlay maps file paths (relative to the driver's working directory)
+	// to the contents of overlay files (see Config.Overlay).
+	Overlay map[string][]byte `json:"overlay"`
+}
+
+// DriverResponse defines the schema of a response from an external
+// driver program, providing the results of a query for package
+// metadata. The driver program must write a JSON-encoded
+// DriverResponse message to its standard output.
+//
+// See the package documentation for an overview.
+type DriverResponse struct {
+	// NotHandled is returned if the request can't be handled by the current
+	// driver. If an external driver returns a response with NotHandled, the
+	// rest of the DriverResponse is ignored, and go/packages will fallback
+	// to the next driver. If go/packages is extended in the future to support
+	// lists of multiple drivers, go/packages will fall back to the next driver.
+	NotHandled bool
+
+	// Compiler and Arch are the arguments pass of types.SizesFor
+	// to get a types.Sizes to use when type checking.
+	Compiler string
+	Arch     string
+
+	// Roots is the set of package IDs that make up the root packages.
+	// We have to encode this separately because when we encode a single package
+	// we cannot know if it is one of the roots as that requires knowledge of the
+	// graph it is part of.
+	Roots []string `json:",omitempty"`
+
+	// Packages is the full set of packages in the graph.
+	// The packages are not connected into a graph.
+	// The Imports if populated will be stubs that only have their ID set.
+	// Imports will be connected and then type and syntax information added in a
+	// later pass (see refine).
+	Packages []*Package
+
+	// GoVersion is the minor version number used by the driver
+	// (e.g. the go command on the PATH) when selecting .go files.
+	// Zero means unknown.
+	GoVersion int
+}
+
+// driver is the type for functions that query the build system for the
+// packages named by the patterns.
+type driver func(cfg *Config, patterns ...string) (*DriverResponse, error)
+
+// findExternalDriver returns the file path of a tool that supplies
+// the build system package structure, or "" if not found."
+// If GOPACKAGESDRIVER is set in the environment findExternalTool returns its
+// value, otherwise it searches for a binary named gopackagesdriver on the PATH.
+func findExternalDriver(cfg *Config) driver {
+	const toolPrefix = "GOPACKAGESDRIVER="
+	tool := ""
+	for _, env := range cfg.Env {
+		if val := strings.TrimPrefix(env, toolPrefix); val != env {
+			tool = val
+		}
+	}
+	if tool != "" && tool == "off" {
+		return nil
+	}
+	if tool == "" {
+		var err error
+		tool, err = exec.LookPath("gopackagesdriver")
+		if err != nil {
+			return nil
+		}
+	}
+	return func(cfg *Config, words ...string) (*DriverResponse, error) {
+		req, err := json.Marshal(DriverRequest{
+			Mode:       cfg.Mode,
+			Env:        cfg.Env,
+			BuildFlags: cfg.BuildFlags,
+			Tests:      cfg.Tests,
+			Overlay:    cfg.Overlay,
+		})
+		if err != nil {
+			return nil, fmt.Errorf("failed to encode message to driver tool: %v", err)
+		}
+
+		buf := new(bytes.Buffer)
+		stderr := new(bytes.Buffer)
+		cmd := exec.CommandContext(cfg.Context, tool, words...)
+		cmd.Dir = cfg.Dir
+		// The cwd gets resolved to the real path. On Darwin, where
+		// /tmp is a symlink, this breaks anything that expects the
+		// working directory to keep the original path, including the
+		// go command when dealing with modules.
+		//
+		// os.Getwd stdlib has a special feature where if the
+		// cwd and the PWD are the same node then it trusts
+		// the PWD, so by setting it in the env for the child
+		// process we fix up all the paths returned by the go
+		// command.
+		//
+		// (See similar trick in Invocation.run in ../../internal/gocommand/invoke.go)
+		cmd.Env = append(slicesClip(cfg.Env), "PWD="+cfg.Dir)
+		cmd.Stdin = bytes.NewReader(req)
+		cmd.Stdout = buf
+		cmd.Stderr = stderr
+
+		if err := cmd.Run(); err != nil {
+			return nil, fmt.Errorf("%v: %v: %s", tool, err, cmd.Stderr)
+		}
+		if len(stderr.Bytes()) != 0 && os.Getenv("GOPACKAGESPRINTDRIVERERRORS") != "" {
+			fmt.Fprintf(os.Stderr, "%s stderr: <<%s>>\n", cmdDebugStr(cmd), stderr)
+		}
+
+		var response DriverResponse
+		if err := json.Unmarshal(buf.Bytes(), &response); err != nil {
+			return nil, err
+		}
+		return &response, nil
+	}
+}
+
+// slicesClip removes unused capacity from the slice, returning s[:len(s):len(s)].
+// TODO(adonovan): use go1.21 slices.Clip.
+func slicesClip[S ~[]E, E any](s S) S { return s[:len(s):len(s)] }
diff --git a/vendor/golang.org/x/tools/go/packages/golist.go b/vendor/golang.org/x/tools/go/packages/golist.go
new file mode 100644
index 0000000..1a3a5b4
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/packages/golist.go
@@ -0,0 +1,1066 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packages
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"log"
+	"os"
+	"os/exec"
+	"path"
+	"path/filepath"
+	"reflect"
+	"sort"
+	"strconv"
+	"strings"
+	"sync"
+	"unicode"
+
+	"golang.org/x/tools/internal/gocommand"
+	"golang.org/x/tools/internal/packagesinternal"
+)
+
+// debug controls verbose logging.
+var debug, _ = strconv.ParseBool(os.Getenv("GOPACKAGESDEBUG"))
+
+// A goTooOldError reports that the go command
+// found by exec.LookPath is too old to use the new go list behavior.
+type goTooOldError struct {
+	error
+}
+
+// responseDeduper wraps a DriverResponse, deduplicating its contents.
+type responseDeduper struct {
+	seenRoots    map[string]bool
+	seenPackages map[string]*Package
+	dr           *DriverResponse
+}
+
+func newDeduper() *responseDeduper {
+	return &responseDeduper{
+		dr:           &DriverResponse{},
+		seenRoots:    map[string]bool{},
+		seenPackages: map[string]*Package{},
+	}
+}
+
+// addAll fills in r with a DriverResponse.
+func (r *responseDeduper) addAll(dr *DriverResponse) {
+	for _, pkg := range dr.Packages {
+		r.addPackage(pkg)
+	}
+	for _, root := range dr.Roots {
+		r.addRoot(root)
+	}
+	r.dr.GoVersion = dr.GoVersion
+}
+
+func (r *responseDeduper) addPackage(p *Package) {
+	if r.seenPackages[p.ID] != nil {
+		return
+	}
+	r.seenPackages[p.ID] = p
+	r.dr.Packages = append(r.dr.Packages, p)
+}
+
+func (r *responseDeduper) addRoot(id string) {
+	if r.seenRoots[id] {
+		return
+	}
+	r.seenRoots[id] = true
+	r.dr.Roots = append(r.dr.Roots, id)
+}
+
+type golistState struct {
+	cfg *Config
+	ctx context.Context
+
+	envOnce    sync.Once
+	goEnvError error
+	goEnv      map[string]string
+
+	rootsOnce     sync.Once
+	rootDirsError error
+	rootDirs      map[string]string
+
+	goVersionOnce  sync.Once
+	goVersionError error
+	goVersion      int // The X in Go 1.X.
+
+	// vendorDirs caches the (non)existence of vendor directories.
+	vendorDirs map[string]bool
+}
+
+// getEnv returns Go environment variables. Only specific variables are
+// populated -- computing all of them is slow.
+func (state *golistState) getEnv() (map[string]string, error) {
+	state.envOnce.Do(func() {
+		var b *bytes.Buffer
+		b, state.goEnvError = state.invokeGo("env", "-json", "GOMOD", "GOPATH")
+		if state.goEnvError != nil {
+			return
+		}
+
+		state.goEnv = make(map[string]string)
+		decoder := json.NewDecoder(b)
+		if state.goEnvError = decoder.Decode(&state.goEnv); state.goEnvError != nil {
+			return
+		}
+	})
+	return state.goEnv, state.goEnvError
+}
+
+// mustGetEnv is a convenience function that can be used if getEnv has already succeeded.
+func (state *golistState) mustGetEnv() map[string]string {
+	env, err := state.getEnv()
+	if err != nil {
+		panic(fmt.Sprintf("mustGetEnv: %v", err))
+	}
+	return env
+}
+
+// goListDriver uses the go list command to interpret the patterns and produce
+// the build system package structure.
+// See driver for more details.
+func goListDriver(cfg *Config, patterns ...string) (_ *DriverResponse, err error) {
+	// Make sure that any asynchronous go commands are killed when we return.
+	parentCtx := cfg.Context
+	if parentCtx == nil {
+		parentCtx = context.Background()
+	}
+	ctx, cancel := context.WithCancel(parentCtx)
+	defer cancel()
+
+	response := newDeduper()
+
+	state := &golistState{
+		cfg:        cfg,
+		ctx:        ctx,
+		vendorDirs: map[string]bool{},
+	}
+
+	// Fill in response.Sizes asynchronously if necessary.
+	if cfg.Mode&NeedTypesSizes != 0 || cfg.Mode&NeedTypes != 0 {
+		errCh := make(chan error)
+		go func() {
+			compiler, arch, err := getSizesForArgs(ctx, state.cfgInvocation(), cfg.gocmdRunner)
+			response.dr.Compiler = compiler
+			response.dr.Arch = arch
+			errCh <- err
+		}()
+		defer func() {
+			if sizesErr := <-errCh; sizesErr != nil {
+				err = sizesErr
+			}
+		}()
+	}
+
+	// Determine files requested in contains patterns
+	var containFiles []string
+	restPatterns := make([]string, 0, len(patterns))
+	// Extract file= and other [querytype]= patterns. Report an error if querytype
+	// doesn't exist.
+extractQueries:
+	for _, pattern := range patterns {
+		eqidx := strings.Index(pattern, "=")
+		if eqidx < 0 {
+			restPatterns = append(restPatterns, pattern)
+		} else {
+			query, value := pattern[:eqidx], pattern[eqidx+len("="):]
+			switch query {
+			case "file":
+				containFiles = append(containFiles, value)
+			case "pattern":
+				restPatterns = append(restPatterns, value)
+			case "": // not a reserved query
+				restPatterns = append(restPatterns, pattern)
+			default:
+				for _, rune := range query {
+					if rune < 'a' || rune > 'z' { // not a reserved query
+						restPatterns = append(restPatterns, pattern)
+						continue extractQueries
+					}
+				}
+				// Reject all other patterns containing "="
+				return nil, fmt.Errorf("invalid query type %q in query pattern %q", query, pattern)
+			}
+		}
+	}
+
+	// See if we have any patterns to pass through to go list. Zero initial
+	// patterns also requires a go list call, since it's the equivalent of
+	// ".".
+	if len(restPatterns) > 0 || len(patterns) == 0 {
+		dr, err := state.createDriverResponse(restPatterns...)
+		if err != nil {
+			return nil, err
+		}
+		response.addAll(dr)
+	}
+
+	if len(containFiles) != 0 {
+		if err := state.runContainsQueries(response, containFiles); err != nil {
+			return nil, err
+		}
+	}
+
+	// (We may yet return an error due to defer.)
+	return response.dr, nil
+}
+
+func (state *golistState) runContainsQueries(response *responseDeduper, queries []string) error {
+	for _, query := range queries {
+		// TODO(matloob): Do only one query per directory.
+		fdir := filepath.Dir(query)
+		// Pass absolute path of directory to go list so that it knows to treat it as a directory,
+		// not a package path.
+		pattern, err := filepath.Abs(fdir)
+		if err != nil {
+			return fmt.Errorf("could not determine absolute path of file= query path %q: %v", query, err)
+		}
+		dirResponse, err := state.createDriverResponse(pattern)
+
+		// If there was an error loading the package, or no packages are returned,
+		// or the package is returned with errors, try to load the file as an
+		// ad-hoc package.
+		// Usually the error will appear in a returned package, but may not if we're
+		// in module mode and the ad-hoc is located outside a module.
+		if err != nil || len(dirResponse.Packages) == 0 || len(dirResponse.Packages) == 1 && len(dirResponse.Packages[0].GoFiles) == 0 &&
+			len(dirResponse.Packages[0].Errors) == 1 {
+			var queryErr error
+			if dirResponse, queryErr = state.adhocPackage(pattern, query); queryErr != nil {
+				return err // return the original error
+			}
+		}
+		isRoot := make(map[string]bool, len(dirResponse.Roots))
+		for _, root := range dirResponse.Roots {
+			isRoot[root] = true
+		}
+		for _, pkg := range dirResponse.Packages {
+			// Add any new packages to the main set
+			// We don't bother to filter packages that will be dropped by the changes of roots,
+			// that will happen anyway during graph construction outside this function.
+			// Over-reporting packages is not a problem.
+			response.addPackage(pkg)
+			// if the package was not a root one, it cannot have the file
+			if !isRoot[pkg.ID] {
+				continue
+			}
+			for _, pkgFile := range pkg.GoFiles {
+				if filepath.Base(query) == filepath.Base(pkgFile) {
+					response.addRoot(pkg.ID)
+					break
+				}
+			}
+		}
+	}
+	return nil
+}
+
+// adhocPackage attempts to load or construct an ad-hoc package for a given
+// query, if the original call to the driver produced inadequate results.
+func (state *golistState) adhocPackage(pattern, query string) (*DriverResponse, error) {
+	response, err := state.createDriverResponse(query)
+	if err != nil {
+		return nil, err
+	}
+	// If we get nothing back from `go list`,
+	// try to make this file into its own ad-hoc package.
+	// TODO(rstambler): Should this check against the original response?
+	if len(response.Packages) == 0 {
+		response.Packages = append(response.Packages, &Package{
+			ID:              "command-line-arguments",
+			PkgPath:         query,
+			GoFiles:         []string{query},
+			CompiledGoFiles: []string{query},
+			Imports:         make(map[string]*Package),
+		})
+		response.Roots = append(response.Roots, "command-line-arguments")
+	}
+	// Handle special cases.
+	if len(response.Packages) == 1 {
+		// golang/go#33482: If this is a file= query for ad-hoc packages where
+		// the file only exists on an overlay, and exists outside of a module,
+		// add the file to the package and remove the errors.
+		if response.Packages[0].ID == "command-line-arguments" ||
+			filepath.ToSlash(response.Packages[0].PkgPath) == filepath.ToSlash(query) {
+			if len(response.Packages[0].GoFiles) == 0 {
+				filename := filepath.Join(pattern, filepath.Base(query)) // avoid recomputing abspath
+				// TODO(matloob): check if the file is outside of a root dir?
+				for path := range state.cfg.Overlay {
+					if path == filename {
+						response.Packages[0].Errors = nil
+						response.Packages[0].GoFiles = []string{path}
+						response.Packages[0].CompiledGoFiles = []string{path}
+					}
+				}
+			}
+		}
+	}
+	return response, nil
+}
+
+// Fields must match go list;
+// see $GOROOT/src/cmd/go/internal/load/pkg.go.
+type jsonPackage struct {
+	ImportPath        string
+	Dir               string
+	Name              string
+	Export            string
+	GoFiles           []string
+	CompiledGoFiles   []string
+	IgnoredGoFiles    []string
+	IgnoredOtherFiles []string
+	EmbedPatterns     []string
+	EmbedFiles        []string
+	CFiles            []string
+	CgoFiles          []string
+	CXXFiles          []string
+	MFiles            []string
+	HFiles            []string
+	FFiles            []string
+	SFiles            []string
+	SwigFiles         []string
+	SwigCXXFiles      []string
+	SysoFiles         []string
+	Imports           []string
+	ImportMap         map[string]string
+	Deps              []string
+	Module            *Module
+	TestGoFiles       []string
+	TestImports       []string
+	XTestGoFiles      []string
+	XTestImports      []string
+	ForTest           string // q in a "p [q.test]" package, else ""
+	DepOnly           bool
+
+	Error      *packagesinternal.PackageError
+	DepsErrors []*packagesinternal.PackageError
+}
+
+type jsonPackageError struct {
+	ImportStack []string
+	Pos         string
+	Err         string
+}
+
+func otherFiles(p *jsonPackage) [][]string {
+	return [][]string{p.CFiles, p.CXXFiles, p.MFiles, p.HFiles, p.FFiles, p.SFiles, p.SwigFiles, p.SwigCXXFiles, p.SysoFiles}
+}
+
+// createDriverResponse uses the "go list" command to expand the pattern
+// words and return a response for the specified packages.
+func (state *golistState) createDriverResponse(words ...string) (*DriverResponse, error) {
+	// go list uses the following identifiers in ImportPath and Imports:
+	//
+	// 	"p"			-- importable package or main (command)
+	// 	"q.test"		-- q's test executable
+	// 	"p [q.test]"		-- variant of p as built for q's test executable
+	// 	"q_test [q.test]"	-- q's external test package
+	//
+	// The packages p that are built differently for a test q.test
+	// are q itself, plus any helpers used by the external test q_test,
+	// typically including "testing" and all its dependencies.
+
+	// Run "go list" for complete
+	// information on the specified packages.
+	goVersion, err := state.getGoVersion()
+	if err != nil {
+		return nil, err
+	}
+	buf, err := state.invokeGo("list", golistargs(state.cfg, words, goVersion)...)
+	if err != nil {
+		return nil, err
+	}
+
+	seen := make(map[string]*jsonPackage)
+	pkgs := make(map[string]*Package)
+	additionalErrors := make(map[string][]Error)
+	// Decode the JSON and convert it to Package form.
+	response := &DriverResponse{
+		GoVersion: goVersion,
+	}
+	for dec := json.NewDecoder(buf); dec.More(); {
+		p := new(jsonPackage)
+		if err := dec.Decode(p); err != nil {
+			return nil, fmt.Errorf("JSON decoding failed: %v", err)
+		}
+
+		if p.ImportPath == "" {
+			// The documentation for go list says that “[e]rroneous packages will have
+			// a non-empty ImportPath”. If for some reason it comes back empty, we
+			// prefer to error out rather than silently discarding data or handing
+			// back a package without any way to refer to it.
+			if p.Error != nil {
+				return nil, Error{
+					Pos: p.Error.Pos,
+					Msg: p.Error.Err,
+				}
+			}
+			return nil, fmt.Errorf("package missing import path: %+v", p)
+		}
+
+		// Work around https://golang.org/issue/33157:
+		// go list -e, when given an absolute path, will find the package contained at
+		// that directory. But when no package exists there, it will return a fake package
+		// with an error and the ImportPath set to the absolute path provided to go list.
+		// Try to convert that absolute path to what its package path would be if it's
+		// contained in a known module or GOPATH entry. This will allow the package to be
+		// properly "reclaimed" when overlays are processed.
+		if filepath.IsAbs(p.ImportPath) && p.Error != nil {
+			pkgPath, ok, err := state.getPkgPath(p.ImportPath)
+			if err != nil {
+				return nil, err
+			}
+			if ok {
+				p.ImportPath = pkgPath
+			}
+		}
+
+		if old, found := seen[p.ImportPath]; found {
+			// If one version of the package has an error, and the other doesn't, assume
+			// that this is a case where go list is reporting a fake dependency variant
+			// of the imported package: When a package tries to invalidly import another
+			// package, go list emits a variant of the imported package (with the same
+			// import path, but with an error on it, and the package will have a
+			// DepError set on it). An example of when this can happen is for imports of
+			// main packages: main packages can not be imported, but they may be
+			// separately matched and listed by another pattern.
+			// See golang.org/issue/36188 for more details.
+
+			// The plan is that eventually, hopefully in Go 1.15, the error will be
+			// reported on the importing package rather than the duplicate "fake"
+			// version of the imported package. Once all supported versions of Go
+			// have the new behavior this logic can be deleted.
+			// TODO(matloob): delete the workaround logic once all supported versions of
+			// Go return the errors on the proper package.
+
+			// There should be exactly one version of a package that doesn't have an
+			// error.
+			if old.Error == nil && p.Error == nil {
+				if !reflect.DeepEqual(p, old) {
+					return nil, fmt.Errorf("internal error: go list gives conflicting information for package %v", p.ImportPath)
+				}
+				continue
+			}
+
+			// Determine if this package's error needs to be bubbled up.
+			// This is a hack, and we expect for go list to eventually set the error
+			// on the package.
+			if old.Error != nil {
+				var errkind string
+				if strings.Contains(old.Error.Err, "not an importable package") {
+					errkind = "not an importable package"
+				} else if strings.Contains(old.Error.Err, "use of internal package") && strings.Contains(old.Error.Err, "not allowed") {
+					errkind = "use of internal package not allowed"
+				}
+				if errkind != "" {
+					if len(old.Error.ImportStack) < 1 {
+						return nil, fmt.Errorf(`internal error: go list gave a %q error with empty import stack`, errkind)
+					}
+					importingPkg := old.Error.ImportStack[len(old.Error.ImportStack)-1]
+					if importingPkg == old.ImportPath {
+						// Using an older version of Go which put this package itself on top of import
+						// stack, instead of the importer. Look for importer in second from top
+						// position.
+						if len(old.Error.ImportStack) < 2 {
+							return nil, fmt.Errorf(`internal error: go list gave a %q error with an import stack without importing package`, errkind)
+						}
+						importingPkg = old.Error.ImportStack[len(old.Error.ImportStack)-2]
+					}
+					additionalErrors[importingPkg] = append(additionalErrors[importingPkg], Error{
+						Pos:  old.Error.Pos,
+						Msg:  old.Error.Err,
+						Kind: ListError,
+					})
+				}
+			}
+
+			// Make sure that if there's a version of the package without an error,
+			// that's the one reported to the user.
+			if old.Error == nil {
+				continue
+			}
+
+			// This package will replace the old one at the end of the loop.
+		}
+		seen[p.ImportPath] = p
+
+		pkg := &Package{
+			Name:            p.Name,
+			ID:              p.ImportPath,
+			GoFiles:         absJoin(p.Dir, p.GoFiles, p.CgoFiles),
+			CompiledGoFiles: absJoin(p.Dir, p.CompiledGoFiles),
+			OtherFiles:      absJoin(p.Dir, otherFiles(p)...),
+			EmbedFiles:      absJoin(p.Dir, p.EmbedFiles),
+			EmbedPatterns:   absJoin(p.Dir, p.EmbedPatterns),
+			IgnoredFiles:    absJoin(p.Dir, p.IgnoredGoFiles, p.IgnoredOtherFiles),
+			forTest:         p.ForTest,
+			depsErrors:      p.DepsErrors,
+			Module:          p.Module,
+		}
+
+		if (state.cfg.Mode&typecheckCgo) != 0 && len(p.CgoFiles) != 0 {
+			if len(p.CompiledGoFiles) > len(p.GoFiles) {
+				// We need the cgo definitions, which are in the first
+				// CompiledGoFile after the non-cgo ones. This is a hack but there
+				// isn't currently a better way to find it. We also need the pure
+				// Go files and unprocessed cgo files, all of which are already
+				// in pkg.GoFiles.
+				cgoTypes := p.CompiledGoFiles[len(p.GoFiles)]
+				pkg.CompiledGoFiles = append([]string{cgoTypes}, pkg.GoFiles...)
+			} else {
+				// golang/go#38990: go list silently fails to do cgo processing
+				pkg.CompiledGoFiles = nil
+				pkg.Errors = append(pkg.Errors, Error{
+					Msg:  "go list failed to return CompiledGoFiles. This may indicate failure to perform cgo processing; try building at the command line. See https://golang.org/issue/38990.",
+					Kind: ListError,
+				})
+			}
+		}
+
+		// Work around https://golang.org/issue/28749:
+		// cmd/go puts assembly, C, and C++ files in CompiledGoFiles.
+		// Remove files from CompiledGoFiles that are non-go files
+		// (or are not files that look like they are from the cache).
+		if len(pkg.CompiledGoFiles) > 0 {
+			out := pkg.CompiledGoFiles[:0]
+			for _, f := range pkg.CompiledGoFiles {
+				if ext := filepath.Ext(f); ext != ".go" && ext != "" { // ext == "" means the file is from the cache, so probably cgo-processed file
+					continue
+				}
+				out = append(out, f)
+			}
+			pkg.CompiledGoFiles = out
+		}
+
+		// Extract the PkgPath from the package's ID.
+		if i := strings.IndexByte(pkg.ID, ' '); i >= 0 {
+			pkg.PkgPath = pkg.ID[:i]
+		} else {
+			pkg.PkgPath = pkg.ID
+		}
+
+		if pkg.PkgPath == "unsafe" {
+			pkg.CompiledGoFiles = nil // ignore fake unsafe.go file (#59929)
+		} else if len(pkg.CompiledGoFiles) == 0 {
+			// Work around for pre-go.1.11 versions of go list.
+			// TODO(matloob): they should be handled by the fallback.
+			// Can we delete this?
+			pkg.CompiledGoFiles = pkg.GoFiles
+		}
+
+		// Assume go list emits only absolute paths for Dir.
+		if p.Dir != "" && !filepath.IsAbs(p.Dir) {
+			log.Fatalf("internal error: go list returned non-absolute Package.Dir: %s", p.Dir)
+		}
+
+		if p.Export != "" && !filepath.IsAbs(p.Export) {
+			pkg.ExportFile = filepath.Join(p.Dir, p.Export)
+		} else {
+			pkg.ExportFile = p.Export
+		}
+
+		// imports
+		//
+		// Imports contains the IDs of all imported packages.
+		// ImportsMap records (path, ID) only where they differ.
+		ids := make(map[string]bool)
+		for _, id := range p.Imports {
+			ids[id] = true
+		}
+		pkg.Imports = make(map[string]*Package)
+		for path, id := range p.ImportMap {
+			pkg.Imports[path] = &Package{ID: id} // non-identity import
+			delete(ids, id)
+		}
+		for id := range ids {
+			if id == "C" {
+				continue
+			}
+
+			pkg.Imports[id] = &Package{ID: id} // identity import
+		}
+		if !p.DepOnly {
+			response.Roots = append(response.Roots, pkg.ID)
+		}
+
+		// Temporary work-around for golang/go#39986. Parse filenames out of
+		// error messages. This happens if there are unrecoverable syntax
+		// errors in the source, so we can't match on a specific error message.
+		//
+		// TODO(rfindley): remove this heuristic, in favor of considering
+		// InvalidGoFiles from the list driver.
+		if err := p.Error; err != nil && state.shouldAddFilenameFromError(p) {
+			addFilenameFromPos := func(pos string) bool {
+				split := strings.Split(pos, ":")
+				if len(split) < 1 {
+					return false
+				}
+				filename := strings.TrimSpace(split[0])
+				if filename == "" {
+					return false
+				}
+				if !filepath.IsAbs(filename) {
+					filename = filepath.Join(state.cfg.Dir, filename)
+				}
+				info, _ := os.Stat(filename)
+				if info == nil {
+					return false
+				}
+				pkg.CompiledGoFiles = append(pkg.CompiledGoFiles, filename)
+				pkg.GoFiles = append(pkg.GoFiles, filename)
+				return true
+			}
+			found := addFilenameFromPos(err.Pos)
+			// In some cases, go list only reports the error position in the
+			// error text, not the error position. One such case is when the
+			// file's package name is a keyword (see golang.org/issue/39763).
+			if !found {
+				addFilenameFromPos(err.Err)
+			}
+		}
+
+		if p.Error != nil {
+			msg := strings.TrimSpace(p.Error.Err) // Trim to work around golang.org/issue/32363.
+			// Address golang.org/issue/35964 by appending import stack to error message.
+			if msg == "import cycle not allowed" && len(p.Error.ImportStack) != 0 {
+				msg += fmt.Sprintf(": import stack: %v", p.Error.ImportStack)
+			}
+			pkg.Errors = append(pkg.Errors, Error{
+				Pos:  p.Error.Pos,
+				Msg:  msg,
+				Kind: ListError,
+			})
+		}
+
+		pkgs[pkg.ID] = pkg
+	}
+
+	for id, errs := range additionalErrors {
+		if p, ok := pkgs[id]; ok {
+			p.Errors = append(p.Errors, errs...)
+		}
+	}
+	for _, pkg := range pkgs {
+		response.Packages = append(response.Packages, pkg)
+	}
+	sort.Slice(response.Packages, func(i, j int) bool { return response.Packages[i].ID < response.Packages[j].ID })
+
+	return response, nil
+}
+
+func (state *golistState) shouldAddFilenameFromError(p *jsonPackage) bool {
+	if len(p.GoFiles) > 0 || len(p.CompiledGoFiles) > 0 {
+		return false
+	}
+
+	goV, err := state.getGoVersion()
+	if err != nil {
+		return false
+	}
+
+	// On Go 1.14 and earlier, only add filenames from errors if the import stack is empty.
+	// The import stack behaves differently for these versions than newer Go versions.
+	if goV < 15 {
+		return len(p.Error.ImportStack) == 0
+	}
+
+	// On Go 1.15 and later, only parse filenames out of error if there's no import stack,
+	// or the current package is at the top of the import stack. This is not guaranteed
+	// to work perfectly, but should avoid some cases where files in errors don't belong to this
+	// package.
+	return len(p.Error.ImportStack) == 0 || p.Error.ImportStack[len(p.Error.ImportStack)-1] == p.ImportPath
+}
+
+// getGoVersion returns the effective minor version of the go command.
+func (state *golistState) getGoVersion() (int, error) {
+	state.goVersionOnce.Do(func() {
+		state.goVersion, state.goVersionError = gocommand.GoVersion(state.ctx, state.cfgInvocation(), state.cfg.gocmdRunner)
+	})
+	return state.goVersion, state.goVersionError
+}
+
+// getPkgPath finds the package path of a directory if it's relative to a root
+// directory.
+func (state *golistState) getPkgPath(dir string) (string, bool, error) {
+	absDir, err := filepath.Abs(dir)
+	if err != nil {
+		return "", false, err
+	}
+	roots, err := state.determineRootDirs()
+	if err != nil {
+		return "", false, err
+	}
+
+	for rdir, rpath := range roots {
+		// Make sure that the directory is in the module,
+		// to avoid creating a path relative to another module.
+		if !strings.HasPrefix(absDir, rdir) {
+			continue
+		}
+		// TODO(matloob): This doesn't properly handle symlinks.
+		r, err := filepath.Rel(rdir, dir)
+		if err != nil {
+			continue
+		}
+		if rpath != "" {
+			// We choose only one root even though the directory even it can belong in multiple modules
+			// or GOPATH entries. This is okay because we only need to work with absolute dirs when a
+			// file is missing from disk, for instance when gopls calls go/packages in an overlay.
+			// Once the file is saved, gopls, or the next invocation of the tool will get the correct
+			// result straight from golist.
+			// TODO(matloob): Implement module tiebreaking?
+			return path.Join(rpath, filepath.ToSlash(r)), true, nil
+		}
+		return filepath.ToSlash(r), true, nil
+	}
+	return "", false, nil
+}
+
+// absJoin absolutizes and flattens the lists of files.
+func absJoin(dir string, fileses ...[]string) (res []string) {
+	for _, files := range fileses {
+		for _, file := range files {
+			if !filepath.IsAbs(file) {
+				file = filepath.Join(dir, file)
+			}
+			res = append(res, file)
+		}
+	}
+	return res
+}
+
+func jsonFlag(cfg *Config, goVersion int) string {
+	if goVersion < 19 {
+		return "-json"
+	}
+	var fields []string
+	added := make(map[string]bool)
+	addFields := func(fs ...string) {
+		for _, f := range fs {
+			if !added[f] {
+				added[f] = true
+				fields = append(fields, f)
+			}
+		}
+	}
+	addFields("Name", "ImportPath", "Error") // These fields are always needed
+	if cfg.Mode&NeedFiles != 0 || cfg.Mode&NeedTypes != 0 {
+		addFields("Dir", "GoFiles", "IgnoredGoFiles", "IgnoredOtherFiles", "CFiles",
+			"CgoFiles", "CXXFiles", "MFiles", "HFiles", "FFiles", "SFiles",
+			"SwigFiles", "SwigCXXFiles", "SysoFiles")
+		if cfg.Tests {
+			addFields("TestGoFiles", "XTestGoFiles")
+		}
+	}
+	if cfg.Mode&NeedTypes != 0 {
+		// CompiledGoFiles seems to be required for the test case TestCgoNoSyntax,
+		// even when -compiled isn't passed in.
+		// TODO(#52435): Should we make the test ask for -compiled, or automatically
+		// request CompiledGoFiles in certain circumstances?
+		addFields("Dir", "CompiledGoFiles")
+	}
+	if cfg.Mode&NeedCompiledGoFiles != 0 {
+		addFields("Dir", "CompiledGoFiles", "Export")
+	}
+	if cfg.Mode&NeedImports != 0 {
+		// When imports are requested, DepOnly is used to distinguish between packages
+		// explicitly requested and transitive imports of those packages.
+		addFields("DepOnly", "Imports", "ImportMap")
+		if cfg.Tests {
+			addFields("TestImports", "XTestImports")
+		}
+	}
+	if cfg.Mode&NeedDeps != 0 {
+		addFields("DepOnly")
+	}
+	if usesExportData(cfg) {
+		// Request Dir in the unlikely case Export is not absolute.
+		addFields("Dir", "Export")
+	}
+	if cfg.Mode&needInternalForTest != 0 {
+		addFields("ForTest")
+	}
+	if cfg.Mode&needInternalDepsErrors != 0 {
+		addFields("DepsErrors")
+	}
+	if cfg.Mode&NeedModule != 0 {
+		addFields("Module")
+	}
+	if cfg.Mode&NeedEmbedFiles != 0 {
+		addFields("EmbedFiles")
+	}
+	if cfg.Mode&NeedEmbedPatterns != 0 {
+		addFields("EmbedPatterns")
+	}
+	return "-json=" + strings.Join(fields, ",")
+}
+
+func golistargs(cfg *Config, words []string, goVersion int) []string {
+	const findFlags = NeedImports | NeedTypes | NeedSyntax | NeedTypesInfo
+	fullargs := []string{
+		"-e", jsonFlag(cfg, goVersion),
+		fmt.Sprintf("-compiled=%t", cfg.Mode&(NeedCompiledGoFiles|NeedSyntax|NeedTypes|NeedTypesInfo|NeedTypesSizes) != 0),
+		fmt.Sprintf("-test=%t", cfg.Tests),
+		fmt.Sprintf("-export=%t", usesExportData(cfg)),
+		fmt.Sprintf("-deps=%t", cfg.Mode&NeedImports != 0),
+		// go list doesn't let you pass -test and -find together,
+		// probably because you'd just get the TestMain.
+		fmt.Sprintf("-find=%t", !cfg.Tests && cfg.Mode&findFlags == 0 && !usesExportData(cfg)),
+	}
+
+	// golang/go#60456: with go1.21 and later, go list serves pgo variants, which
+	// can be costly to compute and may result in redundant processing for the
+	// caller. Disable these variants. If someone wants to add e.g. a NeedPGO
+	// mode flag, that should be a separate proposal.
+	if goVersion >= 21 {
+		fullargs = append(fullargs, "-pgo=off")
+	}
+
+	fullargs = append(fullargs, cfg.BuildFlags...)
+	fullargs = append(fullargs, "--")
+	fullargs = append(fullargs, words...)
+	return fullargs
+}
+
+// cfgInvocation returns an Invocation that reflects cfg's settings.
+func (state *golistState) cfgInvocation() gocommand.Invocation {
+	cfg := state.cfg
+	return gocommand.Invocation{
+		BuildFlags: cfg.BuildFlags,
+		ModFile:    cfg.modFile,
+		ModFlag:    cfg.modFlag,
+		CleanEnv:   cfg.Env != nil,
+		Env:        cfg.Env,
+		Logf:       cfg.Logf,
+		WorkingDir: cfg.Dir,
+		Overlay:    cfg.goListOverlayFile,
+	}
+}
+
+// invokeGo returns the stdout of a go command invocation.
+func (state *golistState) invokeGo(verb string, args ...string) (*bytes.Buffer, error) {
+	cfg := state.cfg
+
+	inv := state.cfgInvocation()
+	inv.Verb = verb
+	inv.Args = args
+	gocmdRunner := cfg.gocmdRunner
+	if gocmdRunner == nil {
+		gocmdRunner = &gocommand.Runner{}
+	}
+	stdout, stderr, friendlyErr, err := gocmdRunner.RunRaw(cfg.Context, inv)
+	if err != nil {
+		// Check for 'go' executable not being found.
+		if ee, ok := err.(*exec.Error); ok && ee.Err == exec.ErrNotFound {
+			return nil, fmt.Errorf("'go list' driver requires 'go', but %s", exec.ErrNotFound)
+		}
+
+		exitErr, ok := err.(*exec.ExitError)
+		if !ok {
+			// Catastrophic error:
+			// - context cancellation
+			return nil, fmt.Errorf("couldn't run 'go': %w", err)
+		}
+
+		// Old go version?
+		if strings.Contains(stderr.String(), "flag provided but not defined") {
+			return nil, goTooOldError{fmt.Errorf("unsupported version of go: %s: %s", exitErr, stderr)}
+		}
+
+		// Related to #24854
+		if len(stderr.String()) > 0 && strings.Contains(stderr.String(), "unexpected directory layout") {
+			return nil, friendlyErr
+		}
+
+		// Is there an error running the C compiler in cgo? This will be reported in the "Error" field
+		// and should be suppressed by go list -e.
+		//
+		// This condition is not perfect yet because the error message can include other error messages than runtime/cgo.
+		isPkgPathRune := func(r rune) bool {
+			// From https://golang.org/ref/spec#Import_declarations:
+			//    Implementation restriction: A compiler may restrict ImportPaths to non-empty strings
+			//    using only characters belonging to Unicode's L, M, N, P, and S general categories
+			//    (the Graphic characters without spaces) and may also exclude the
+			//    characters !"#$%&'()*,:;<=>?[\]^`{|} and the Unicode replacement character U+FFFD.
+			return unicode.IsOneOf([]*unicode.RangeTable{unicode.L, unicode.M, unicode.N, unicode.P, unicode.S}, r) &&
+				!strings.ContainsRune("!\"#$%&'()*,:;<=>?[\\]^`{|}\uFFFD", r)
+		}
+		// golang/go#36770: Handle case where cmd/go prints module download messages before the error.
+		msg := stderr.String()
+		for strings.HasPrefix(msg, "go: downloading") {
+			msg = msg[strings.IndexRune(msg, '\n')+1:]
+		}
+		if len(stderr.String()) > 0 && strings.HasPrefix(stderr.String(), "# ") {
+			msg := msg[len("# "):]
+			if strings.HasPrefix(strings.TrimLeftFunc(msg, isPkgPathRune), "\n") {
+				return stdout, nil
+			}
+			// Treat pkg-config errors as a special case (golang.org/issue/36770).
+			if strings.HasPrefix(msg, "pkg-config") {
+				return stdout, nil
+			}
+		}
+
+		// This error only appears in stderr. See golang.org/cl/166398 for a fix in go list to show
+		// the error in the Err section of stdout in case -e option is provided.
+		// This fix is provided for backwards compatibility.
+		if len(stderr.String()) > 0 && strings.Contains(stderr.String(), "named files must be .go files") {
+			output := fmt.Sprintf(`{"ImportPath": "command-line-arguments","Incomplete": true,"Error": {"Pos": "","Err": %q}}`,
+				strings.Trim(stderr.String(), "\n"))
+			return bytes.NewBufferString(output), nil
+		}
+
+		// Similar to the previous error, but currently lacks a fix in Go.
+		if len(stderr.String()) > 0 && strings.Contains(stderr.String(), "named files must all be in one directory") {
+			output := fmt.Sprintf(`{"ImportPath": "command-line-arguments","Incomplete": true,"Error": {"Pos": "","Err": %q}}`,
+				strings.Trim(stderr.String(), "\n"))
+			return bytes.NewBufferString(output), nil
+		}
+
+		// Backwards compatibility for Go 1.11 because 1.12 and 1.13 put the directory in the ImportPath.
+		// If the package doesn't exist, put the absolute path of the directory into the error message,
+		// as Go 1.13 list does.
+		const noSuchDirectory = "no such directory"
+		if len(stderr.String()) > 0 && strings.Contains(stderr.String(), noSuchDirectory) {
+			errstr := stderr.String()
+			abspath := strings.TrimSpace(errstr[strings.Index(errstr, noSuchDirectory)+len(noSuchDirectory):])
+			output := fmt.Sprintf(`{"ImportPath": %q,"Incomplete": true,"Error": {"Pos": "","Err": %q}}`,
+				abspath, strings.Trim(stderr.String(), "\n"))
+			return bytes.NewBufferString(output), nil
+		}
+
+		// Workaround for #29280: go list -e has incorrect behavior when an ad-hoc package doesn't exist.
+		// Note that the error message we look for in this case is different that the one looked for above.
+		if len(stderr.String()) > 0 && strings.Contains(stderr.String(), "no such file or directory") {
+			output := fmt.Sprintf(`{"ImportPath": "command-line-arguments","Incomplete": true,"Error": {"Pos": "","Err": %q}}`,
+				strings.Trim(stderr.String(), "\n"))
+			return bytes.NewBufferString(output), nil
+		}
+
+		// Workaround for #34273. go list -e with GO111MODULE=on has incorrect behavior when listing a
+		// directory outside any module.
+		if len(stderr.String()) > 0 && strings.Contains(stderr.String(), "outside available modules") {
+			output := fmt.Sprintf(`{"ImportPath": %q,"Incomplete": true,"Error": {"Pos": "","Err": %q}}`,
+				// TODO(matloob): command-line-arguments isn't correct here.
+				"command-line-arguments", strings.Trim(stderr.String(), "\n"))
+			return bytes.NewBufferString(output), nil
+		}
+
+		// Another variation of the previous error
+		if len(stderr.String()) > 0 && strings.Contains(stderr.String(), "outside module root") {
+			output := fmt.Sprintf(`{"ImportPath": %q,"Incomplete": true,"Error": {"Pos": "","Err": %q}}`,
+				// TODO(matloob): command-line-arguments isn't correct here.
+				"command-line-arguments", strings.Trim(stderr.String(), "\n"))
+			return bytes.NewBufferString(output), nil
+		}
+
+		// Workaround for an instance of golang.org/issue/26755: go list -e  will return a non-zero exit
+		// status if there's a dependency on a package that doesn't exist. But it should return
+		// a zero exit status and set an error on that package.
+		if len(stderr.String()) > 0 && strings.Contains(stderr.String(), "no Go files in") {
+			// Don't clobber stdout if `go list` actually returned something.
+			if len(stdout.String()) > 0 {
+				return stdout, nil
+			}
+			// try to extract package name from string
+			stderrStr := stderr.String()
+			var importPath string
+			colon := strings.Index(stderrStr, ":")
+			if colon > 0 && strings.HasPrefix(stderrStr, "go build ") {
+				importPath = stderrStr[len("go build "):colon]
+			}
+			output := fmt.Sprintf(`{"ImportPath": %q,"Incomplete": true,"Error": {"Pos": "","Err": %q}}`,
+				importPath, strings.Trim(stderrStr, "\n"))
+			return bytes.NewBufferString(output), nil
+		}
+
+		// Export mode entails a build.
+		// If that build fails, errors appear on stderr
+		// (despite the -e flag) and the Export field is blank.
+		// Do not fail in that case.
+		// The same is true if an ad-hoc package given to go list doesn't exist.
+		// TODO(matloob): Remove these once we can depend on go list to exit with a zero status with -e even when
+		// packages don't exist or a build fails.
+		if !usesExportData(cfg) && !containsGoFile(args) {
+			return nil, friendlyErr
+		}
+	}
+	return stdout, nil
+}
+
+func containsGoFile(s []string) bool {
+	for _, f := range s {
+		if strings.HasSuffix(f, ".go") {
+			return true
+		}
+	}
+	return false
+}
+
+func cmdDebugStr(cmd *exec.Cmd) string {
+	env := make(map[string]string)
+	for _, kv := range cmd.Env {
+		split := strings.SplitN(kv, "=", 2)
+		k, v := split[0], split[1]
+		env[k] = v
+	}
+
+	var args []string
+	for _, arg := range cmd.Args {
+		quoted := strconv.Quote(arg)
+		if quoted[1:len(quoted)-1] != arg || strings.Contains(arg, " ") {
+			args = append(args, quoted)
+		} else {
+			args = append(args, arg)
+		}
+	}
+	return fmt.Sprintf("GOROOT=%v GOPATH=%v GO111MODULE=%v GOPROXY=%v PWD=%v %v", env["GOROOT"], env["GOPATH"], env["GO111MODULE"], env["GOPROXY"], env["PWD"], strings.Join(args, " "))
+}
+
+// getSizesForArgs queries 'go list' for the appropriate
+// Compiler and GOARCH arguments to pass to [types.SizesFor].
+func getSizesForArgs(ctx context.Context, inv gocommand.Invocation, gocmdRunner *gocommand.Runner) (string, string, error) {
+	inv.Verb = "list"
+	inv.Args = []string{"-f", "{{context.GOARCH}} {{context.Compiler}}", "--", "unsafe"}
+	stdout, stderr, friendlyErr, rawErr := gocmdRunner.RunRaw(ctx, inv)
+	var goarch, compiler string
+	if rawErr != nil {
+		rawErrMsg := rawErr.Error()
+		if strings.Contains(rawErrMsg, "cannot find main module") ||
+			strings.Contains(rawErrMsg, "go.mod file not found") {
+			// User's running outside of a module.
+			// All bets are off. Get GOARCH and guess compiler is gc.
+			// TODO(matloob): Is this a problem in practice?
+			inv.Verb = "env"
+			inv.Args = []string{"GOARCH"}
+			envout, enverr := gocmdRunner.Run(ctx, inv)
+			if enverr != nil {
+				return "", "", enverr
+			}
+			goarch = strings.TrimSpace(envout.String())
+			compiler = "gc"
+		} else if friendlyErr != nil {
+			return "", "", friendlyErr
+		} else {
+			// This should be unreachable, but be defensive
+			// in case RunRaw's error results are inconsistent.
+			return "", "", rawErr
+		}
+	} else {
+		fields := strings.Fields(stdout.String())
+		if len(fields) < 2 {
+			return "", "", fmt.Errorf("could not parse GOARCH and Go compiler in format \"<GOARCH> <compiler>\":\nstdout: <<%s>>\nstderr: <<%s>>",
+				stdout.String(), stderr.String())
+		}
+		goarch = fields[0]
+		compiler = fields[1]
+	}
+	return compiler, goarch, nil
+}
diff --git a/vendor/golang.org/x/tools/go/packages/golist_overlay.go b/vendor/golang.org/x/tools/go/packages/golist_overlay.go
new file mode 100644
index 0000000..d823c47
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/packages/golist_overlay.go
@@ -0,0 +1,83 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packages
+
+import (
+	"encoding/json"
+	"path/filepath"
+
+	"golang.org/x/tools/internal/gocommand"
+)
+
+// determineRootDirs returns a mapping from absolute directories that could
+// contain code to their corresponding import path prefixes.
+func (state *golistState) determineRootDirs() (map[string]string, error) {
+	env, err := state.getEnv()
+	if err != nil {
+		return nil, err
+	}
+	if env["GOMOD"] != "" {
+		state.rootsOnce.Do(func() {
+			state.rootDirs, state.rootDirsError = state.determineRootDirsModules()
+		})
+	} else {
+		state.rootsOnce.Do(func() {
+			state.rootDirs, state.rootDirsError = state.determineRootDirsGOPATH()
+		})
+	}
+	return state.rootDirs, state.rootDirsError
+}
+
+func (state *golistState) determineRootDirsModules() (map[string]string, error) {
+	// List all of the modules--the first will be the directory for the main
+	// module. Any replaced modules will also need to be treated as roots.
+	// Editing files in the module cache isn't a great idea, so we don't
+	// plan to ever support that.
+	out, err := state.invokeGo("list", "-m", "-json", "all")
+	if err != nil {
+		// 'go list all' will fail if we're outside of a module and
+		// GO111MODULE=on. Try falling back without 'all'.
+		var innerErr error
+		out, innerErr = state.invokeGo("list", "-m", "-json")
+		if innerErr != nil {
+			return nil, err
+		}
+	}
+	roots := map[string]string{}
+	modules := map[string]string{}
+	var i int
+	for dec := json.NewDecoder(out); dec.More(); {
+		mod := new(gocommand.ModuleJSON)
+		if err := dec.Decode(mod); err != nil {
+			return nil, err
+		}
+		if mod.Dir != "" && mod.Path != "" {
+			// This is a valid module; add it to the map.
+			absDir, err := filepath.Abs(mod.Dir)
+			if err != nil {
+				return nil, err
+			}
+			modules[absDir] = mod.Path
+			// The first result is the main module.
+			if i == 0 || mod.Replace != nil && mod.Replace.Path != "" {
+				roots[absDir] = mod.Path
+			}
+		}
+		i++
+	}
+	return roots, nil
+}
+
+func (state *golistState) determineRootDirsGOPATH() (map[string]string, error) {
+	m := map[string]string{}
+	for _, dir := range filepath.SplitList(state.mustGetEnv()["GOPATH"]) {
+		absDir, err := filepath.Abs(dir)
+		if err != nil {
+			return nil, err
+		}
+		m[filepath.Join(absDir, "src")] = ""
+	}
+	return m, nil
+}
diff --git a/vendor/golang.org/x/tools/go/packages/loadmode_string.go b/vendor/golang.org/x/tools/go/packages/loadmode_string.go
new file mode 100644
index 0000000..5c080d2
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/packages/loadmode_string.go
@@ -0,0 +1,57 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packages
+
+import (
+	"fmt"
+	"strings"
+)
+
+var allModes = []LoadMode{
+	NeedName,
+	NeedFiles,
+	NeedCompiledGoFiles,
+	NeedImports,
+	NeedDeps,
+	NeedExportFile,
+	NeedTypes,
+	NeedSyntax,
+	NeedTypesInfo,
+	NeedTypesSizes,
+}
+
+var modeStrings = []string{
+	"NeedName",
+	"NeedFiles",
+	"NeedCompiledGoFiles",
+	"NeedImports",
+	"NeedDeps",
+	"NeedExportFile",
+	"NeedTypes",
+	"NeedSyntax",
+	"NeedTypesInfo",
+	"NeedTypesSizes",
+}
+
+func (mod LoadMode) String() string {
+	m := mod
+	if m == 0 {
+		return "LoadMode(0)"
+	}
+	var out []string
+	for i, x := range allModes {
+		if x > m {
+			break
+		}
+		if (m & x) != 0 {
+			out = append(out, modeStrings[i])
+			m = m ^ x
+		}
+	}
+	if m != 0 {
+		out = append(out, "Unknown")
+	}
+	return fmt.Sprintf("LoadMode(%s)", strings.Join(out, "|"))
+}
diff --git a/vendor/golang.org/x/tools/go/packages/packages.go b/vendor/golang.org/x/tools/go/packages/packages.go
new file mode 100644
index 0000000..0b6bfaf
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/packages/packages.go
@@ -0,0 +1,1515 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packages
+
+// See doc.go for package documentation and implementation notes.
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"go/ast"
+	"go/parser"
+	"go/scanner"
+	"go/token"
+	"go/types"
+	"io"
+	"log"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"sync"
+	"time"
+
+	"golang.org/x/sync/errgroup"
+
+	"golang.org/x/tools/go/gcexportdata"
+	"golang.org/x/tools/internal/gocommand"
+	"golang.org/x/tools/internal/packagesinternal"
+	"golang.org/x/tools/internal/typesinternal"
+	"golang.org/x/tools/internal/versions"
+)
+
+// A LoadMode controls the amount of detail to return when loading.
+// The bits below can be combined to specify which fields should be
+// filled in the result packages.
+//
+// The zero value is a special case, equivalent to combining
+// the NeedName, NeedFiles, and NeedCompiledGoFiles bits.
+//
+// ID and Errors (if present) will always be filled.
+// [Load] may return more information than requested.
+//
+// Unfortunately there are a number of open bugs related to
+// interactions among the LoadMode bits:
+// - https://github.com/golang/go/issues/56633
+// - https://github.com/golang/go/issues/56677
+// - https://github.com/golang/go/issues/58726
+// - https://github.com/golang/go/issues/63517
+type LoadMode int
+
+const (
+	// NeedName adds Name and PkgPath.
+	NeedName LoadMode = 1 << iota
+
+	// NeedFiles adds GoFiles and OtherFiles.
+	NeedFiles
+
+	// NeedCompiledGoFiles adds CompiledGoFiles.
+	NeedCompiledGoFiles
+
+	// NeedImports adds Imports. If NeedDeps is not set, the Imports field will contain
+	// "placeholder" Packages with only the ID set.
+	NeedImports
+
+	// NeedDeps adds the fields requested by the LoadMode in the packages in Imports.
+	NeedDeps
+
+	// NeedExportFile adds ExportFile.
+	NeedExportFile
+
+	// NeedTypes adds Types, Fset, and IllTyped.
+	NeedTypes
+
+	// NeedSyntax adds Syntax and Fset.
+	NeedSyntax
+
+	// NeedTypesInfo adds TypesInfo.
+	NeedTypesInfo
+
+	// NeedTypesSizes adds TypesSizes.
+	NeedTypesSizes
+
+	// needInternalDepsErrors adds the internal deps errors field for use by gopls.
+	needInternalDepsErrors
+
+	// needInternalForTest adds the internal forTest field.
+	// Tests must also be set on the context for this field to be populated.
+	needInternalForTest
+
+	// typecheckCgo enables full support for type checking cgo. Requires Go 1.15+.
+	// Modifies CompiledGoFiles and Types, and has no effect on its own.
+	typecheckCgo
+
+	// NeedModule adds Module.
+	NeedModule
+
+	// NeedEmbedFiles adds EmbedFiles.
+	NeedEmbedFiles
+
+	// NeedEmbedPatterns adds EmbedPatterns.
+	NeedEmbedPatterns
+)
+
+const (
+	// Deprecated: LoadFiles exists for historical compatibility
+	// and should not be used. Please directly specify the needed fields using the Need values.
+	LoadFiles = NeedName | NeedFiles | NeedCompiledGoFiles
+
+	// Deprecated: LoadImports exists for historical compatibility
+	// and should not be used. Please directly specify the needed fields using the Need values.
+	LoadImports = LoadFiles | NeedImports
+
+	// Deprecated: LoadTypes exists for historical compatibility
+	// and should not be used. Please directly specify the needed fields using the Need values.
+	LoadTypes = LoadImports | NeedTypes | NeedTypesSizes
+
+	// Deprecated: LoadSyntax exists for historical compatibility
+	// and should not be used. Please directly specify the needed fields using the Need values.
+	LoadSyntax = LoadTypes | NeedSyntax | NeedTypesInfo
+
+	// Deprecated: LoadAllSyntax exists for historical compatibility
+	// and should not be used. Please directly specify the needed fields using the Need values.
+	LoadAllSyntax = LoadSyntax | NeedDeps
+
+	// Deprecated: NeedExportsFile is a historical misspelling of NeedExportFile.
+	NeedExportsFile = NeedExportFile
+)
+
+// A Config specifies details about how packages should be loaded.
+// The zero value is a valid configuration.
+//
+// Calls to Load do not modify this struct.
+//
+// TODO(adonovan): #67702: this is currently false: in fact,
+// calls to [Load] do not modify the public fields of this struct, but
+// may modify hidden fields, so concurrent calls to [Load] must not
+// use the same Config. But perhaps we should reestablish the
+// documented invariant.
+type Config struct {
+	// Mode controls the level of information returned for each package.
+	Mode LoadMode
+
+	// Context specifies the context for the load operation.
+	// Cancelling the context may cause [Load] to abort and
+	// return an error.
+	Context context.Context
+
+	// Logf is the logger for the config.
+	// If the user provides a logger, debug logging is enabled.
+	// If the GOPACKAGESDEBUG environment variable is set to true,
+	// but the logger is nil, default to log.Printf.
+	Logf func(format string, args ...interface{})
+
+	// Dir is the directory in which to run the build system's query tool
+	// that provides information about the packages.
+	// If Dir is empty, the tool is run in the current directory.
+	Dir string
+
+	// Env is the environment to use when invoking the build system's query tool.
+	// If Env is nil, the current environment is used.
+	// As in os/exec's Cmd, only the last value in the slice for
+	// each environment key is used. To specify the setting of only
+	// a few variables, append to the current environment, as in:
+	//
+	//	opt.Env = append(os.Environ(), "GOOS=plan9", "GOARCH=386")
+	//
+	Env []string
+
+	// gocmdRunner guards go command calls from concurrency errors.
+	gocmdRunner *gocommand.Runner
+
+	// BuildFlags is a list of command-line flags to be passed through to
+	// the build system's query tool.
+	BuildFlags []string
+
+	// modFile will be used for -modfile in go command invocations.
+	modFile string
+
+	// modFlag will be used for -modfile in go command invocations.
+	modFlag string
+
+	// Fset provides source position information for syntax trees and types.
+	// If Fset is nil, Load will use a new fileset, but preserve Fset's value.
+	Fset *token.FileSet
+
+	// ParseFile is called to read and parse each file
+	// when preparing a package's type-checked syntax tree.
+	// It must be safe to call ParseFile simultaneously from multiple goroutines.
+	// If ParseFile is nil, the loader will uses parser.ParseFile.
+	//
+	// ParseFile should parse the source from src and use filename only for
+	// recording position information.
+	//
+	// An application may supply a custom implementation of ParseFile
+	// to change the effective file contents or the behavior of the parser,
+	// or to modify the syntax tree. For example, selectively eliminating
+	// unwanted function bodies can significantly accelerate type checking.
+	ParseFile func(fset *token.FileSet, filename string, src []byte) (*ast.File, error)
+
+	// If Tests is set, the loader includes not just the packages
+	// matching a particular pattern but also any related test packages,
+	// including test-only variants of the package and the test executable.
+	//
+	// For example, when using the go command, loading "fmt" with Tests=true
+	// returns four packages, with IDs "fmt" (the standard package),
+	// "fmt [fmt.test]" (the package as compiled for the test),
+	// "fmt_test" (the test functions from source files in package fmt_test),
+	// and "fmt.test" (the test binary).
+	//
+	// In build systems with explicit names for tests,
+	// setting Tests may have no effect.
+	Tests bool
+
+	// Overlay is a mapping from absolute file paths to file contents.
+	//
+	// For each map entry, [Load] uses the alternative file
+	// contents provided by the overlay mapping instead of reading
+	// from the file system. This mechanism can be used to enable
+	// editor-integrated tools to correctly analyze the contents
+	// of modified but unsaved buffers, for example.
+	//
+	// The overlay mapping is passed to the build system's driver
+	// (see "The driver protocol") so that it too can report
+	// consistent package metadata about unsaved files. However,
+	// drivers may vary in their level of support for overlays.
+	Overlay map[string][]byte
+
+	// goListOverlayFile is the JSON file that encodes the Overlay
+	// mapping, used by 'go list -overlay=...'
+	goListOverlayFile string
+}
+
+// Load loads and returns the Go packages named by the given patterns.
+//
+// Config specifies loading options;
+// nil behaves the same as an empty Config.
+//
+// The [Config.Mode] field is a set of bits that determine what kinds
+// of information should be computed and returned. Modes that require
+// more information tend to be slower. See [LoadMode] for details
+// and important caveats. Its zero value is equivalent to
+// NeedName | NeedFiles | NeedCompiledGoFiles.
+//
+// Each call to Load returns a new set of [Package] instances.
+// The Packages and their Imports form a directed acyclic graph.
+//
+// If the [NeedTypes] mode flag was set, each call to Load uses a new
+// [types.Importer], so [types.Object] and [types.Type] values from
+// different calls to Load must not be mixed as they will have
+// inconsistent notions of type identity.
+//
+// If any of the patterns was invalid as defined by the
+// underlying build system, Load returns an error.
+// It may return an empty list of packages without an error,
+// for instance for an empty expansion of a valid wildcard.
+// Errors associated with a particular package are recorded in the
+// corresponding Package's Errors list, and do not cause Load to
+// return an error. Clients may need to handle such errors before
+// proceeding with further analysis. The PrintErrors function is
+// provided for convenient display of all errors.
+func Load(cfg *Config, patterns ...string) ([]*Package, error) {
+	ld := newLoader(cfg)
+	response, external, err := defaultDriver(&ld.Config, patterns...)
+	if err != nil {
+		return nil, err
+	}
+
+	ld.sizes = types.SizesFor(response.Compiler, response.Arch)
+	if ld.sizes == nil && ld.Config.Mode&(NeedTypes|NeedTypesSizes|NeedTypesInfo) != 0 {
+		// Type size information is needed but unavailable.
+		if external {
+			// An external driver may fail to populate the Compiler/GOARCH fields,
+			// especially since they are relatively new (see #63700).
+			// Provide a sensible fallback in this case.
+			ld.sizes = types.SizesFor("gc", runtime.GOARCH)
+			if ld.sizes == nil { // gccgo-only arch
+				ld.sizes = types.SizesFor("gc", "amd64")
+			}
+		} else {
+			// Go list should never fail to deliver accurate size information.
+			// Reject the whole Load since the error is the same for every package.
+			return nil, fmt.Errorf("can't determine type sizes for compiler %q on GOARCH %q",
+				response.Compiler, response.Arch)
+		}
+	}
+
+	return ld.refine(response)
+}
+
+// defaultDriver is a driver that implements go/packages' fallback behavior.
+// It will try to request to an external driver, if one exists. If there's
+// no external driver, or the driver returns a response with NotHandled set,
+// defaultDriver will fall back to the go list driver.
+// The boolean result indicates that an external driver handled the request.
+func defaultDriver(cfg *Config, patterns ...string) (*DriverResponse, bool, error) {
+	const (
+		// windowsArgMax specifies the maximum command line length for
+		// the Windows' CreateProcess function.
+		windowsArgMax = 32767
+		// maxEnvSize is a very rough estimation of the maximum environment
+		// size of a user.
+		maxEnvSize = 16384
+		// safeArgMax specifies the maximum safe command line length to use
+		// by the underlying driver excl. the environment. We choose the Windows'
+		// ARG_MAX as the starting point because it's one of the lowest ARG_MAX
+		// constants out of the different supported platforms,
+		// e.g., https://www.in-ulm.de/~mascheck/various/argmax/#results.
+		safeArgMax = windowsArgMax - maxEnvSize
+	)
+	chunks, err := splitIntoChunks(patterns, safeArgMax)
+	if err != nil {
+		return nil, false, err
+	}
+
+	if driver := findExternalDriver(cfg); driver != nil {
+		response, err := callDriverOnChunks(driver, cfg, chunks)
+		if err != nil {
+			return nil, false, err
+		} else if !response.NotHandled {
+			return response, true, nil
+		}
+		// (fall through)
+	}
+
+	// go list fallback
+	//
+	// Write overlays once, as there are many calls
+	// to 'go list' (one per chunk plus others too).
+	overlay, cleanupOverlay, err := gocommand.WriteOverlays(cfg.Overlay)
+	if err != nil {
+		return nil, false, err
+	}
+	defer cleanupOverlay()
+	cfg.goListOverlayFile = overlay
+
+	response, err := callDriverOnChunks(goListDriver, cfg, chunks)
+	if err != nil {
+		return nil, false, err
+	}
+	return response, false, err
+}
+
+// splitIntoChunks chunks the slice so that the total number of characters
+// in a chunk is no longer than argMax.
+func splitIntoChunks(patterns []string, argMax int) ([][]string, error) {
+	if argMax <= 0 {
+		return nil, errors.New("failed to split patterns into chunks, negative safe argMax value")
+	}
+	var chunks [][]string
+	charsInChunk := 0
+	nextChunkStart := 0
+	for i, v := range patterns {
+		vChars := len(v)
+		if vChars > argMax {
+			// a single pattern is longer than the maximum safe ARG_MAX, hardly should happen
+			return nil, errors.New("failed to split patterns into chunks, a pattern is too long")
+		}
+		charsInChunk += vChars + 1 // +1 is for a whitespace between patterns that has to be counted too
+		if charsInChunk > argMax {
+			chunks = append(chunks, patterns[nextChunkStart:i])
+			nextChunkStart = i
+			charsInChunk = vChars
+		}
+	}
+	// add the last chunk
+	if nextChunkStart < len(patterns) {
+		chunks = append(chunks, patterns[nextChunkStart:])
+	}
+	return chunks, nil
+}
+
+func callDriverOnChunks(driver driver, cfg *Config, chunks [][]string) (*DriverResponse, error) {
+	if len(chunks) == 0 {
+		return driver(cfg)
+	}
+	responses := make([]*DriverResponse, len(chunks))
+	errNotHandled := errors.New("driver returned NotHandled")
+	var g errgroup.Group
+	for i, chunk := range chunks {
+		i := i
+		chunk := chunk
+		g.Go(func() (err error) {
+			responses[i], err = driver(cfg, chunk...)
+			if responses[i] != nil && responses[i].NotHandled {
+				err = errNotHandled
+			}
+			return err
+		})
+	}
+	if err := g.Wait(); err != nil {
+		if errors.Is(err, errNotHandled) {
+			return &DriverResponse{NotHandled: true}, nil
+		}
+		return nil, err
+	}
+	return mergeResponses(responses...), nil
+}
+
+func mergeResponses(responses ...*DriverResponse) *DriverResponse {
+	if len(responses) == 0 {
+		return nil
+	}
+	response := newDeduper()
+	response.dr.NotHandled = false
+	response.dr.Compiler = responses[0].Compiler
+	response.dr.Arch = responses[0].Arch
+	response.dr.GoVersion = responses[0].GoVersion
+	for _, v := range responses {
+		response.addAll(v)
+	}
+	return response.dr
+}
+
+// A Package describes a loaded Go package.
+//
+// It also defines part of the JSON schema of [DriverResponse].
+// See the package documentation for an overview.
+type Package struct {
+	// ID is a unique identifier for a package,
+	// in a syntax provided by the underlying build system.
+	//
+	// Because the syntax varies based on the build system,
+	// clients should treat IDs as opaque and not attempt to
+	// interpret them.
+	ID string
+
+	// Name is the package name as it appears in the package source code.
+	Name string
+
+	// PkgPath is the package path as used by the go/types package.
+	PkgPath string
+
+	// Errors contains any errors encountered querying the metadata
+	// of the package, or while parsing or type-checking its files.
+	Errors []Error
+
+	// TypeErrors contains the subset of errors produced during type checking.
+	TypeErrors []types.Error
+
+	// GoFiles lists the absolute file paths of the package's Go source files.
+	// It may include files that should not be compiled, for example because
+	// they contain non-matching build tags, are documentary pseudo-files such as
+	// unsafe/unsafe.go or builtin/builtin.go, or are subject to cgo preprocessing.
+	GoFiles []string
+
+	// CompiledGoFiles lists the absolute file paths of the package's source
+	// files that are suitable for type checking.
+	// This may differ from GoFiles if files are processed before compilation.
+	CompiledGoFiles []string
+
+	// OtherFiles lists the absolute file paths of the package's non-Go source files,
+	// including assembly, C, C++, Fortran, Objective-C, SWIG, and so on.
+	OtherFiles []string
+
+	// EmbedFiles lists the absolute file paths of the package's files
+	// embedded with go:embed.
+	EmbedFiles []string
+
+	// EmbedPatterns lists the absolute file patterns of the package's
+	// files embedded with go:embed.
+	EmbedPatterns []string
+
+	// IgnoredFiles lists source files that are not part of the package
+	// using the current build configuration but that might be part of
+	// the package using other build configurations.
+	IgnoredFiles []string
+
+	// ExportFile is the absolute path to a file containing type
+	// information for the package as provided by the build system.
+	ExportFile string
+
+	// Imports maps import paths appearing in the package's Go source files
+	// to corresponding loaded Packages.
+	Imports map[string]*Package
+
+	// Module is the module information for the package if it exists.
+	//
+	// Note: it may be missing for std and cmd; see Go issue #65816.
+	Module *Module
+
+	// -- The following fields are not part of the driver JSON schema. --
+
+	// Types provides type information for the package.
+	// The NeedTypes LoadMode bit sets this field for packages matching the
+	// patterns; type information for dependencies may be missing or incomplete,
+	// unless NeedDeps and NeedImports are also set.
+	//
+	// Each call to [Load] returns a consistent set of type
+	// symbols, as defined by the comment at [types.Identical].
+	// Avoid mixing type information from two or more calls to [Load].
+	Types *types.Package `json:"-"`
+
+	// Fset provides position information for Types, TypesInfo, and Syntax.
+	// It is set only when Types is set.
+	Fset *token.FileSet `json:"-"`
+
+	// IllTyped indicates whether the package or any dependency contains errors.
+	// It is set only when Types is set.
+	IllTyped bool `json:"-"`
+
+	// Syntax is the package's syntax trees, for the files listed in CompiledGoFiles.
+	//
+	// The NeedSyntax LoadMode bit populates this field for packages matching the patterns.
+	// If NeedDeps and NeedImports are also set, this field will also be populated
+	// for dependencies.
+	//
+	// Syntax is kept in the same order as CompiledGoFiles, with the caveat that nils are
+	// removed.  If parsing returned nil, Syntax may be shorter than CompiledGoFiles.
+	Syntax []*ast.File `json:"-"`
+
+	// TypesInfo provides type information about the package's syntax trees.
+	// It is set only when Syntax is set.
+	TypesInfo *types.Info `json:"-"`
+
+	// TypesSizes provides the effective size function for types in TypesInfo.
+	TypesSizes types.Sizes `json:"-"`
+
+	// -- internal --
+
+	// forTest is the package under test, if any.
+	forTest string
+
+	// depsErrors is the DepsErrors field from the go list response, if any.
+	depsErrors []*packagesinternal.PackageError
+}
+
+// Module provides module information for a package.
+//
+// It also defines part of the JSON schema of [DriverResponse].
+// See the package documentation for an overview.
+type Module struct {
+	Path      string       // module path
+	Version   string       // module version
+	Replace   *Module      // replaced by this module
+	Time      *time.Time   // time version was created
+	Main      bool         // is this the main module?
+	Indirect  bool         // is this module only an indirect dependency of main module?
+	Dir       string       // directory holding files for this module, if any
+	GoMod     string       // path to go.mod file used when loading this module, if any
+	GoVersion string       // go version used in module
+	Error     *ModuleError // error loading module
+}
+
+// ModuleError holds errors loading a module.
+type ModuleError struct {
+	Err string // the error itself
+}
+
+func init() {
+	packagesinternal.GetForTest = func(p interface{}) string {
+		return p.(*Package).forTest
+	}
+	packagesinternal.GetDepsErrors = func(p interface{}) []*packagesinternal.PackageError {
+		return p.(*Package).depsErrors
+	}
+	packagesinternal.SetModFile = func(config interface{}, value string) {
+		config.(*Config).modFile = value
+	}
+	packagesinternal.SetModFlag = func(config interface{}, value string) {
+		config.(*Config).modFlag = value
+	}
+	packagesinternal.TypecheckCgo = int(typecheckCgo)
+	packagesinternal.DepsErrors = int(needInternalDepsErrors)
+	packagesinternal.ForTest = int(needInternalForTest)
+}
+
+// An Error describes a problem with a package's metadata, syntax, or types.
+type Error struct {
+	Pos  string // "file:line:col" or "file:line" or "" or "-"
+	Msg  string
+	Kind ErrorKind
+}
+
+// ErrorKind describes the source of the error, allowing the user to
+// differentiate between errors generated by the driver, the parser, or the
+// type-checker.
+type ErrorKind int
+
+const (
+	UnknownError ErrorKind = iota
+	ListError
+	ParseError
+	TypeError
+)
+
+func (err Error) Error() string {
+	pos := err.Pos
+	if pos == "" {
+		pos = "-" // like token.Position{}.String()
+	}
+	return pos + ": " + err.Msg
+}
+
+// flatPackage is the JSON form of Package
+// It drops all the type and syntax fields, and transforms the Imports
+//
+// TODO(adonovan): identify this struct with Package, effectively
+// publishing the JSON protocol.
+type flatPackage struct {
+	ID              string
+	Name            string            `json:",omitempty"`
+	PkgPath         string            `json:",omitempty"`
+	Errors          []Error           `json:",omitempty"`
+	GoFiles         []string          `json:",omitempty"`
+	CompiledGoFiles []string          `json:",omitempty"`
+	OtherFiles      []string          `json:",omitempty"`
+	EmbedFiles      []string          `json:",omitempty"`
+	EmbedPatterns   []string          `json:",omitempty"`
+	IgnoredFiles    []string          `json:",omitempty"`
+	ExportFile      string            `json:",omitempty"`
+	Imports         map[string]string `json:",omitempty"`
+}
+
+// MarshalJSON returns the Package in its JSON form.
+// For the most part, the structure fields are written out unmodified, and
+// the type and syntax fields are skipped.
+// The imports are written out as just a map of path to package id.
+// The errors are written using a custom type that tries to preserve the
+// structure of error types we know about.
+//
+// This method exists to enable support for additional build systems.  It is
+// not intended for use by clients of the API and we may change the format.
+func (p *Package) MarshalJSON() ([]byte, error) {
+	flat := &flatPackage{
+		ID:              p.ID,
+		Name:            p.Name,
+		PkgPath:         p.PkgPath,
+		Errors:          p.Errors,
+		GoFiles:         p.GoFiles,
+		CompiledGoFiles: p.CompiledGoFiles,
+		OtherFiles:      p.OtherFiles,
+		EmbedFiles:      p.EmbedFiles,
+		EmbedPatterns:   p.EmbedPatterns,
+		IgnoredFiles:    p.IgnoredFiles,
+		ExportFile:      p.ExportFile,
+	}
+	if len(p.Imports) > 0 {
+		flat.Imports = make(map[string]string, len(p.Imports))
+		for path, ipkg := range p.Imports {
+			flat.Imports[path] = ipkg.ID
+		}
+	}
+	return json.Marshal(flat)
+}
+
+// UnmarshalJSON reads in a Package from its JSON format.
+// See MarshalJSON for details about the format accepted.
+func (p *Package) UnmarshalJSON(b []byte) error {
+	flat := &flatPackage{}
+	if err := json.Unmarshal(b, &flat); err != nil {
+		return err
+	}
+	*p = Package{
+		ID:              flat.ID,
+		Name:            flat.Name,
+		PkgPath:         flat.PkgPath,
+		Errors:          flat.Errors,
+		GoFiles:         flat.GoFiles,
+		CompiledGoFiles: flat.CompiledGoFiles,
+		OtherFiles:      flat.OtherFiles,
+		EmbedFiles:      flat.EmbedFiles,
+		EmbedPatterns:   flat.EmbedPatterns,
+		IgnoredFiles:    flat.IgnoredFiles,
+		ExportFile:      flat.ExportFile,
+	}
+	if len(flat.Imports) > 0 {
+		p.Imports = make(map[string]*Package, len(flat.Imports))
+		for path, id := range flat.Imports {
+			p.Imports[path] = &Package{ID: id}
+		}
+	}
+	return nil
+}
+
+func (p *Package) String() string { return p.ID }
+
+// loaderPackage augments Package with state used during the loading phase
+type loaderPackage struct {
+	*Package
+	importErrors map[string]error // maps each bad import to its error
+	loadOnce     sync.Once
+	color        uint8 // for cycle detection
+	needsrc      bool  // load from source (Mode >= LoadTypes)
+	needtypes    bool  // type information is either requested or depended on
+	initial      bool  // package was matched by a pattern
+	goVersion    int   // minor version number of go command on PATH
+}
+
+// loader holds the working state of a single call to load.
+type loader struct {
+	pkgs map[string]*loaderPackage
+	Config
+	sizes        types.Sizes // non-nil if needed by mode
+	parseCache   map[string]*parseValue
+	parseCacheMu sync.Mutex
+	exportMu     sync.Mutex // enforces mutual exclusion of exportdata operations
+
+	// Config.Mode contains the implied mode (see impliedLoadMode).
+	// Implied mode contains all the fields we need the data for.
+	// In requestedMode there are the actually requested fields.
+	// We'll zero them out before returning packages to the user.
+	// This makes it easier for us to get the conditions where
+	// we need certain modes right.
+	requestedMode LoadMode
+}
+
+type parseValue struct {
+	f     *ast.File
+	err   error
+	ready chan struct{}
+}
+
+func newLoader(cfg *Config) *loader {
+	ld := &loader{
+		parseCache: map[string]*parseValue{},
+	}
+	if cfg != nil {
+		ld.Config = *cfg
+		// If the user has provided a logger, use it.
+		ld.Config.Logf = cfg.Logf
+	}
+	if ld.Config.Logf == nil {
+		// If the GOPACKAGESDEBUG environment variable is set to true,
+		// but the user has not provided a logger, default to log.Printf.
+		if debug {
+			ld.Config.Logf = log.Printf
+		} else {
+			ld.Config.Logf = func(format string, args ...interface{}) {}
+		}
+	}
+	if ld.Config.Mode == 0 {
+		ld.Config.Mode = NeedName | NeedFiles | NeedCompiledGoFiles // Preserve zero behavior of Mode for backwards compatibility.
+	}
+	if ld.Config.Env == nil {
+		ld.Config.Env = os.Environ()
+	}
+	if ld.Config.gocmdRunner == nil {
+		ld.Config.gocmdRunner = &gocommand.Runner{}
+	}
+	if ld.Context == nil {
+		ld.Context = context.Background()
+	}
+	if ld.Dir == "" {
+		if dir, err := os.Getwd(); err == nil {
+			ld.Dir = dir
+		}
+	}
+
+	// Save the actually requested fields. We'll zero them out before returning packages to the user.
+	ld.requestedMode = ld.Mode
+	ld.Mode = impliedLoadMode(ld.Mode)
+
+	if ld.Mode&NeedTypes != 0 || ld.Mode&NeedSyntax != 0 {
+		if ld.Fset == nil {
+			ld.Fset = token.NewFileSet()
+		}
+
+		// ParseFile is required even in LoadTypes mode
+		// because we load source if export data is missing.
+		if ld.ParseFile == nil {
+			ld.ParseFile = func(fset *token.FileSet, filename string, src []byte) (*ast.File, error) {
+				const mode = parser.AllErrors | parser.ParseComments
+				return parser.ParseFile(fset, filename, src, mode)
+			}
+		}
+	}
+
+	return ld
+}
+
+// refine connects the supplied packages into a graph and then adds type
+// and syntax information as requested by the LoadMode.
+func (ld *loader) refine(response *DriverResponse) ([]*Package, error) {
+	roots := response.Roots
+	rootMap := make(map[string]int, len(roots))
+	for i, root := range roots {
+		rootMap[root] = i
+	}
+	ld.pkgs = make(map[string]*loaderPackage)
+	// first pass, fixup and build the map and roots
+	var initial = make([]*loaderPackage, len(roots))
+	for _, pkg := range response.Packages {
+		rootIndex := -1
+		if i, found := rootMap[pkg.ID]; found {
+			rootIndex = i
+		}
+
+		// Overlays can invalidate export data.
+		// TODO(matloob): make this check fine-grained based on dependencies on overlaid files
+		exportDataInvalid := len(ld.Overlay) > 0 || pkg.ExportFile == "" && pkg.PkgPath != "unsafe"
+		// This package needs type information if the caller requested types and the package is
+		// either a root, or it's a non-root and the user requested dependencies ...
+		needtypes := (ld.Mode&NeedTypes|NeedTypesInfo != 0 && (rootIndex >= 0 || ld.Mode&NeedDeps != 0))
+		// This package needs source if the call requested source (or types info, which implies source)
+		// and the package is either a root, or itas a non- root and the user requested dependencies...
+		needsrc := ((ld.Mode&(NeedSyntax|NeedTypesInfo) != 0 && (rootIndex >= 0 || ld.Mode&NeedDeps != 0)) ||
+			// ... or if we need types and the exportData is invalid. We fall back to (incompletely)
+			// typechecking packages from source if they fail to compile.
+			(ld.Mode&(NeedTypes|NeedTypesInfo) != 0 && exportDataInvalid)) && pkg.PkgPath != "unsafe"
+		lpkg := &loaderPackage{
+			Package:   pkg,
+			needtypes: needtypes,
+			needsrc:   needsrc,
+			goVersion: response.GoVersion,
+		}
+		ld.pkgs[lpkg.ID] = lpkg
+		if rootIndex >= 0 {
+			initial[rootIndex] = lpkg
+			lpkg.initial = true
+		}
+	}
+	for i, root := range roots {
+		if initial[i] == nil {
+			return nil, fmt.Errorf("root package %v is missing", root)
+		}
+	}
+
+	if ld.Mode&NeedImports != 0 {
+		// Materialize the import graph.
+
+		const (
+			white = 0 // new
+			grey  = 1 // in progress
+			black = 2 // complete
+		)
+
+		// visit traverses the import graph, depth-first,
+		// and materializes the graph as Packages.Imports.
+		//
+		// Valid imports are saved in the Packages.Import map.
+		// Invalid imports (cycles and missing nodes) are saved in the importErrors map.
+		// Thus, even in the presence of both kinds of errors,
+		// the Import graph remains a DAG.
+		//
+		// visit returns whether the package needs src or has a transitive
+		// dependency on a package that does. These are the only packages
+		// for which we load source code.
+		var stack []*loaderPackage
+		var visit func(lpkg *loaderPackage) bool
+		visit = func(lpkg *loaderPackage) bool {
+			switch lpkg.color {
+			case black:
+				return lpkg.needsrc
+			case grey:
+				panic("internal error: grey node")
+			}
+			lpkg.color = grey
+			stack = append(stack, lpkg) // push
+			stubs := lpkg.Imports       // the structure form has only stubs with the ID in the Imports
+			lpkg.Imports = make(map[string]*Package, len(stubs))
+			for importPath, ipkg := range stubs {
+				var importErr error
+				imp := ld.pkgs[ipkg.ID]
+				if imp == nil {
+					// (includes package "C" when DisableCgo)
+					importErr = fmt.Errorf("missing package: %q", ipkg.ID)
+				} else if imp.color == grey {
+					importErr = fmt.Errorf("import cycle: %s", stack)
+				}
+				if importErr != nil {
+					if lpkg.importErrors == nil {
+						lpkg.importErrors = make(map[string]error)
+					}
+					lpkg.importErrors[importPath] = importErr
+					continue
+				}
+
+				if visit(imp) {
+					lpkg.needsrc = true
+				}
+				lpkg.Imports[importPath] = imp.Package
+			}
+
+			// Complete type information is required for the
+			// immediate dependencies of each source package.
+			if lpkg.needsrc && ld.Mode&NeedTypes != 0 {
+				for _, ipkg := range lpkg.Imports {
+					ld.pkgs[ipkg.ID].needtypes = true
+				}
+			}
+
+			// NeedTypeSizes causes TypeSizes to be set even
+			// on packages for which types aren't needed.
+			if ld.Mode&NeedTypesSizes != 0 {
+				lpkg.TypesSizes = ld.sizes
+			}
+			stack = stack[:len(stack)-1] // pop
+			lpkg.color = black
+
+			return lpkg.needsrc
+		}
+
+		// For each initial package, create its import DAG.
+		for _, lpkg := range initial {
+			visit(lpkg)
+		}
+
+	} else {
+		// !NeedImports: drop the stub (ID-only) import packages
+		// that we are not even going to try to resolve.
+		for _, lpkg := range initial {
+			lpkg.Imports = nil
+		}
+	}
+
+	// Load type data and syntax if needed, starting at
+	// the initial packages (roots of the import DAG).
+	if ld.Mode&NeedTypes != 0 || ld.Mode&NeedSyntax != 0 {
+		var wg sync.WaitGroup
+		for _, lpkg := range initial {
+			wg.Add(1)
+			go func(lpkg *loaderPackage) {
+				ld.loadRecursive(lpkg)
+				wg.Done()
+			}(lpkg)
+		}
+		wg.Wait()
+	}
+
+	// If the context is done, return its error and
+	// throw out [likely] incomplete packages.
+	if err := ld.Context.Err(); err != nil {
+		return nil, err
+	}
+
+	result := make([]*Package, len(initial))
+	for i, lpkg := range initial {
+		result[i] = lpkg.Package
+	}
+	for i := range ld.pkgs {
+		// Clear all unrequested fields,
+		// to catch programs that use more than they request.
+		if ld.requestedMode&NeedName == 0 {
+			ld.pkgs[i].Name = ""
+			ld.pkgs[i].PkgPath = ""
+		}
+		if ld.requestedMode&NeedFiles == 0 {
+			ld.pkgs[i].GoFiles = nil
+			ld.pkgs[i].OtherFiles = nil
+			ld.pkgs[i].IgnoredFiles = nil
+		}
+		if ld.requestedMode&NeedEmbedFiles == 0 {
+			ld.pkgs[i].EmbedFiles = nil
+		}
+		if ld.requestedMode&NeedEmbedPatterns == 0 {
+			ld.pkgs[i].EmbedPatterns = nil
+		}
+		if ld.requestedMode&NeedCompiledGoFiles == 0 {
+			ld.pkgs[i].CompiledGoFiles = nil
+		}
+		if ld.requestedMode&NeedImports == 0 {
+			ld.pkgs[i].Imports = nil
+		}
+		if ld.requestedMode&NeedExportFile == 0 {
+			ld.pkgs[i].ExportFile = ""
+		}
+		if ld.requestedMode&NeedTypes == 0 {
+			ld.pkgs[i].Types = nil
+			ld.pkgs[i].IllTyped = false
+		}
+		if ld.requestedMode&NeedSyntax == 0 {
+			ld.pkgs[i].Syntax = nil
+		}
+		if ld.requestedMode&NeedTypes == 0 && ld.requestedMode&NeedSyntax == 0 {
+			ld.pkgs[i].Fset = nil
+		}
+		if ld.requestedMode&NeedTypesInfo == 0 {
+			ld.pkgs[i].TypesInfo = nil
+		}
+		if ld.requestedMode&NeedTypesSizes == 0 {
+			ld.pkgs[i].TypesSizes = nil
+		}
+		if ld.requestedMode&NeedModule == 0 {
+			ld.pkgs[i].Module = nil
+		}
+	}
+
+	return result, nil
+}
+
+// loadRecursive loads the specified package and its dependencies,
+// recursively, in parallel, in topological order.
+// It is atomic and idempotent.
+// Precondition: ld.Mode&NeedTypes.
+func (ld *loader) loadRecursive(lpkg *loaderPackage) {
+	lpkg.loadOnce.Do(func() {
+		// Load the direct dependencies, in parallel.
+		var wg sync.WaitGroup
+		for _, ipkg := range lpkg.Imports {
+			imp := ld.pkgs[ipkg.ID]
+			wg.Add(1)
+			go func(imp *loaderPackage) {
+				ld.loadRecursive(imp)
+				wg.Done()
+			}(imp)
+		}
+		wg.Wait()
+		ld.loadPackage(lpkg)
+	})
+}
+
+// loadPackage loads the specified package.
+// It must be called only once per Package,
+// after immediate dependencies are loaded.
+// Precondition: ld.Mode & NeedTypes.
+func (ld *loader) loadPackage(lpkg *loaderPackage) {
+	if lpkg.PkgPath == "unsafe" {
+		// Fill in the blanks to avoid surprises.
+		lpkg.Types = types.Unsafe
+		lpkg.Fset = ld.Fset
+		lpkg.Syntax = []*ast.File{}
+		lpkg.TypesInfo = new(types.Info)
+		lpkg.TypesSizes = ld.sizes
+		return
+	}
+
+	// Call NewPackage directly with explicit name.
+	// This avoids skew between golist and go/types when the files'
+	// package declarations are inconsistent.
+	lpkg.Types = types.NewPackage(lpkg.PkgPath, lpkg.Name)
+	lpkg.Fset = ld.Fset
+
+	// Start shutting down if the context is done and do not load
+	// source or export data files.
+	// Packages that import this one will have ld.Context.Err() != nil.
+	// ld.Context.Err() will be returned later by refine.
+	if ld.Context.Err() != nil {
+		return
+	}
+
+	// Subtle: we populate all Types fields with an empty Package
+	// before loading export data so that export data processing
+	// never has to create a types.Package for an indirect dependency,
+	// which would then require that such created packages be explicitly
+	// inserted back into the Import graph as a final step after export data loading.
+	// (Hence this return is after the Types assignment.)
+	// The Diamond test exercises this case.
+	if !lpkg.needtypes && !lpkg.needsrc {
+		return
+	}
+	if !lpkg.needsrc {
+		if err := ld.loadFromExportData(lpkg); err != nil {
+			lpkg.Errors = append(lpkg.Errors, Error{
+				Pos:  "-",
+				Msg:  err.Error(),
+				Kind: UnknownError, // e.g. can't find/open/parse export data
+			})
+		}
+		return // not a source package, don't get syntax trees
+	}
+
+	appendError := func(err error) {
+		// Convert various error types into the one true Error.
+		var errs []Error
+		switch err := err.(type) {
+		case Error:
+			// from driver
+			errs = append(errs, err)
+
+		case *os.PathError:
+			// from parser
+			errs = append(errs, Error{
+				Pos:  err.Path + ":1",
+				Msg:  err.Err.Error(),
+				Kind: ParseError,
+			})
+
+		case scanner.ErrorList:
+			// from parser
+			for _, err := range err {
+				errs = append(errs, Error{
+					Pos:  err.Pos.String(),
+					Msg:  err.Msg,
+					Kind: ParseError,
+				})
+			}
+
+		case types.Error:
+			// from type checker
+			lpkg.TypeErrors = append(lpkg.TypeErrors, err)
+			errs = append(errs, Error{
+				Pos:  err.Fset.Position(err.Pos).String(),
+				Msg:  err.Msg,
+				Kind: TypeError,
+			})
+
+		default:
+			// unexpected impoverished error from parser?
+			errs = append(errs, Error{
+				Pos:  "-",
+				Msg:  err.Error(),
+				Kind: UnknownError,
+			})
+
+			// If you see this error message, please file a bug.
+			log.Printf("internal error: error %q (%T) without position", err, err)
+		}
+
+		lpkg.Errors = append(lpkg.Errors, errs...)
+	}
+
+	// If the go command on the PATH is newer than the runtime,
+	// then the go/{scanner,ast,parser,types} packages from the
+	// standard library may be unable to process the files
+	// selected by go list.
+	//
+	// There is currently no way to downgrade the effective
+	// version of the go command (see issue 52078), so we proceed
+	// with the newer go command but, in case of parse or type
+	// errors, we emit an additional diagnostic.
+	//
+	// See:
+	// - golang.org/issue/52078 (flag to set release tags)
+	// - golang.org/issue/50825 (gopls legacy version support)
+	// - golang.org/issue/55883 (go/packages confusing error)
+	//
+	// Should we assert a hard minimum of (currently) go1.16 here?
+	var runtimeVersion int
+	if _, err := fmt.Sscanf(runtime.Version(), "go1.%d", &runtimeVersion); err == nil && runtimeVersion < lpkg.goVersion {
+		defer func() {
+			if len(lpkg.Errors) > 0 {
+				appendError(Error{
+					Pos:  "-",
+					Msg:  fmt.Sprintf("This application uses version go1.%d of the source-processing packages but runs version go1.%d of 'go list'. It may fail to process source files that rely on newer language features. If so, rebuild the application using a newer version of Go.", runtimeVersion, lpkg.goVersion),
+					Kind: UnknownError,
+				})
+			}
+		}()
+	}
+
+	if ld.Config.Mode&NeedTypes != 0 && len(lpkg.CompiledGoFiles) == 0 && lpkg.ExportFile != "" {
+		// The config requested loading sources and types, but sources are missing.
+		// Add an error to the package and fall back to loading from export data.
+		appendError(Error{"-", fmt.Sprintf("sources missing for package %s", lpkg.ID), ParseError})
+		_ = ld.loadFromExportData(lpkg) // ignore any secondary errors
+
+		return // can't get syntax trees for this package
+	}
+
+	files, errs := ld.parseFiles(lpkg.CompiledGoFiles)
+	for _, err := range errs {
+		appendError(err)
+	}
+
+	lpkg.Syntax = files
+	if ld.Config.Mode&NeedTypes == 0 {
+		return
+	}
+
+	// Start shutting down if the context is done and do not type check.
+	// Packages that import this one will have ld.Context.Err() != nil.
+	// ld.Context.Err() will be returned later by refine.
+	if ld.Context.Err() != nil {
+		return
+	}
+
+	lpkg.TypesInfo = &types.Info{
+		Types:      make(map[ast.Expr]types.TypeAndValue),
+		Defs:       make(map[*ast.Ident]types.Object),
+		Uses:       make(map[*ast.Ident]types.Object),
+		Implicits:  make(map[ast.Node]types.Object),
+		Instances:  make(map[*ast.Ident]types.Instance),
+		Scopes:     make(map[ast.Node]*types.Scope),
+		Selections: make(map[*ast.SelectorExpr]*types.Selection),
+	}
+	versions.InitFileVersions(lpkg.TypesInfo)
+	lpkg.TypesSizes = ld.sizes
+
+	importer := importerFunc(func(path string) (*types.Package, error) {
+		if path == "unsafe" {
+			return types.Unsafe, nil
+		}
+
+		// The imports map is keyed by import path.
+		ipkg := lpkg.Imports[path]
+		if ipkg == nil {
+			if err := lpkg.importErrors[path]; err != nil {
+				return nil, err
+			}
+			// There was skew between the metadata and the
+			// import declarations, likely due to an edit
+			// race, or because the ParseFile feature was
+			// used to supply alternative file contents.
+			return nil, fmt.Errorf("no metadata for %s", path)
+		}
+
+		if ipkg.Types != nil && ipkg.Types.Complete() {
+			return ipkg.Types, nil
+		}
+		log.Fatalf("internal error: package %q without types was imported from %q", path, lpkg)
+		panic("unreachable")
+	})
+
+	// type-check
+	tc := &types.Config{
+		Importer: importer,
+
+		// Type-check bodies of functions only in initial packages.
+		// Example: for import graph A->B->C and initial packages {A,C},
+		// we can ignore function bodies in B.
+		IgnoreFuncBodies: ld.Mode&NeedDeps == 0 && !lpkg.initial,
+
+		Error: appendError,
+		Sizes: ld.sizes, // may be nil
+	}
+	if lpkg.Module != nil && lpkg.Module.GoVersion != "" {
+		tc.GoVersion = "go" + lpkg.Module.GoVersion
+	}
+	if (ld.Mode & typecheckCgo) != 0 {
+		if !typesinternal.SetUsesCgo(tc) {
+			appendError(Error{
+				Msg:  "typecheckCgo requires Go 1.15+",
+				Kind: ListError,
+			})
+			return
+		}
+	}
+
+	typErr := types.NewChecker(tc, ld.Fset, lpkg.Types, lpkg.TypesInfo).Files(lpkg.Syntax)
+	lpkg.importErrors = nil // no longer needed
+
+	// In go/types go1.21 and go1.22, Checker.Files failed fast with a
+	// a "too new" error, without calling tc.Error and without
+	// proceeding to type-check the package (#66525).
+	// We rely on the runtimeVersion error to give the suggested remedy.
+	if typErr != nil && len(lpkg.Errors) == 0 && len(lpkg.Syntax) > 0 {
+		if msg := typErr.Error(); strings.HasPrefix(msg, "package requires newer Go version") {
+			appendError(types.Error{
+				Fset: ld.Fset,
+				Pos:  lpkg.Syntax[0].Package,
+				Msg:  msg,
+			})
+		}
+	}
+
+	// If !Cgo, the type-checker uses FakeImportC mode, so
+	// it doesn't invoke the importer for import "C",
+	// nor report an error for the import,
+	// or for any undefined C.f reference.
+	// We must detect this explicitly and correctly
+	// mark the package as IllTyped (by reporting an error).
+	// TODO(adonovan): if these errors are annoying,
+	// we could just set IllTyped quietly.
+	if tc.FakeImportC {
+	outer:
+		for _, f := range lpkg.Syntax {
+			for _, imp := range f.Imports {
+				if imp.Path.Value == `"C"` {
+					err := types.Error{Fset: ld.Fset, Pos: imp.Pos(), Msg: `import "C" ignored`}
+					appendError(err)
+					break outer
+				}
+			}
+		}
+	}
+
+	// If types.Checker.Files had an error that was unreported,
+	// make sure to report the unknown error so the package is illTyped.
+	if typErr != nil && len(lpkg.Errors) == 0 {
+		appendError(typErr)
+	}
+
+	// Record accumulated errors.
+	illTyped := len(lpkg.Errors) > 0
+	if !illTyped {
+		for _, imp := range lpkg.Imports {
+			if imp.IllTyped {
+				illTyped = true
+				break
+			}
+		}
+	}
+	lpkg.IllTyped = illTyped
+}
+
+// An importFunc is an implementation of the single-method
+// types.Importer interface based on a function value.
+type importerFunc func(path string) (*types.Package, error)
+
+func (f importerFunc) Import(path string) (*types.Package, error) { return f(path) }
+
+// We use a counting semaphore to limit
+// the number of parallel I/O calls per process.
+var ioLimit = make(chan bool, 20)
+
+func (ld *loader) parseFile(filename string) (*ast.File, error) {
+	ld.parseCacheMu.Lock()
+	v, ok := ld.parseCache[filename]
+	if ok {
+		// cache hit
+		ld.parseCacheMu.Unlock()
+		<-v.ready
+	} else {
+		// cache miss
+		v = &parseValue{ready: make(chan struct{})}
+		ld.parseCache[filename] = v
+		ld.parseCacheMu.Unlock()
+
+		var src []byte
+		for f, contents := range ld.Config.Overlay {
+			if sameFile(f, filename) {
+				src = contents
+			}
+		}
+		var err error
+		if src == nil {
+			ioLimit <- true // wait
+			src, err = os.ReadFile(filename)
+			<-ioLimit // signal
+		}
+		if err != nil {
+			v.err = err
+		} else {
+			v.f, v.err = ld.ParseFile(ld.Fset, filename, src)
+		}
+
+		close(v.ready)
+	}
+	return v.f, v.err
+}
+
+// parseFiles reads and parses the Go source files and returns the ASTs
+// of the ones that could be at least partially parsed, along with a
+// list of I/O and parse errors encountered.
+//
+// Because files are scanned in parallel, the token.Pos
+// positions of the resulting ast.Files are not ordered.
+func (ld *loader) parseFiles(filenames []string) ([]*ast.File, []error) {
+	var wg sync.WaitGroup
+	n := len(filenames)
+	parsed := make([]*ast.File, n)
+	errors := make([]error, n)
+	for i, file := range filenames {
+		wg.Add(1)
+		go func(i int, filename string) {
+			parsed[i], errors[i] = ld.parseFile(filename)
+			wg.Done()
+		}(i, file)
+	}
+	wg.Wait()
+
+	// Eliminate nils, preserving order.
+	var o int
+	for _, f := range parsed {
+		if f != nil {
+			parsed[o] = f
+			o++
+		}
+	}
+	parsed = parsed[:o]
+
+	o = 0
+	for _, err := range errors {
+		if err != nil {
+			errors[o] = err
+			o++
+		}
+	}
+	errors = errors[:o]
+
+	return parsed, errors
+}
+
+// sameFile returns true if x and y have the same basename and denote
+// the same file.
+func sameFile(x, y string) bool {
+	if x == y {
+		// It could be the case that y doesn't exist.
+		// For instance, it may be an overlay file that
+		// hasn't been written to disk. To handle that case
+		// let x == y through. (We added the exact absolute path
+		// string to the CompiledGoFiles list, so the unwritten
+		// overlay case implies x==y.)
+		return true
+	}
+	if strings.EqualFold(filepath.Base(x), filepath.Base(y)) { // (optimisation)
+		if xi, err := os.Stat(x); err == nil {
+			if yi, err := os.Stat(y); err == nil {
+				return os.SameFile(xi, yi)
+			}
+		}
+	}
+	return false
+}
+
+// loadFromExportData ensures that type information is present for the specified
+// package, loading it from an export data file on the first request.
+// On success it sets lpkg.Types to a new Package.
+func (ld *loader) loadFromExportData(lpkg *loaderPackage) error {
+	if lpkg.PkgPath == "" {
+		log.Fatalf("internal error: Package %s has no PkgPath", lpkg)
+	}
+
+	// Because gcexportdata.Read has the potential to create or
+	// modify the types.Package for each node in the transitive
+	// closure of dependencies of lpkg, all exportdata operations
+	// must be sequential. (Finer-grained locking would require
+	// changes to the gcexportdata API.)
+	//
+	// The exportMu lock guards the lpkg.Types field and the
+	// types.Package it points to, for each loaderPackage in the graph.
+	//
+	// Not all accesses to Package.Pkg need to be protected by exportMu:
+	// graph ordering ensures that direct dependencies of source
+	// packages are fully loaded before the importer reads their Pkg field.
+	ld.exportMu.Lock()
+	defer ld.exportMu.Unlock()
+
+	if tpkg := lpkg.Types; tpkg != nil && tpkg.Complete() {
+		return nil // cache hit
+	}
+
+	lpkg.IllTyped = true // fail safe
+
+	if lpkg.ExportFile == "" {
+		// Errors while building export data will have been printed to stderr.
+		return fmt.Errorf("no export data file")
+	}
+	f, err := os.Open(lpkg.ExportFile)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	// Read gc export data.
+	//
+	// We don't currently support gccgo export data because all
+	// underlying workspaces use the gc toolchain. (Even build
+	// systems that support gccgo don't use it for workspace
+	// queries.)
+	r, err := gcexportdata.NewReader(f)
+	if err != nil {
+		return fmt.Errorf("reading %s: %v", lpkg.ExportFile, err)
+	}
+
+	// Build the view.
+	//
+	// The gcexportdata machinery has no concept of package ID.
+	// It identifies packages by their PkgPath, which although not
+	// globally unique is unique within the scope of one invocation
+	// of the linker, type-checker, or gcexportdata.
+	//
+	// So, we must build a PkgPath-keyed view of the global
+	// (conceptually ID-keyed) cache of packages and pass it to
+	// gcexportdata. The view must contain every existing
+	// package that might possibly be mentioned by the
+	// current package---its transitive closure.
+	//
+	// In loadPackage, we unconditionally create a types.Package for
+	// each dependency so that export data loading does not
+	// create new ones.
+	//
+	// TODO(adonovan): it would be simpler and more efficient
+	// if the export data machinery invoked a callback to
+	// get-or-create a package instead of a map.
+	//
+	view := make(map[string]*types.Package) // view seen by gcexportdata
+	seen := make(map[*loaderPackage]bool)   // all visited packages
+	var visit func(pkgs map[string]*Package)
+	visit = func(pkgs map[string]*Package) {
+		for _, p := range pkgs {
+			lpkg := ld.pkgs[p.ID]
+			if !seen[lpkg] {
+				seen[lpkg] = true
+				view[lpkg.PkgPath] = lpkg.Types
+				visit(lpkg.Imports)
+			}
+		}
+	}
+	visit(lpkg.Imports)
+
+	viewLen := len(view) + 1 // adding the self package
+	// Parse the export data.
+	// (May modify incomplete packages in view but not create new ones.)
+	tpkg, err := gcexportdata.Read(r, ld.Fset, view, lpkg.PkgPath)
+	if err != nil {
+		return fmt.Errorf("reading %s: %v", lpkg.ExportFile, err)
+	}
+	if _, ok := view["go.shape"]; ok {
+		// Account for the pseudopackage "go.shape" that gets
+		// created by generic code.
+		viewLen++
+	}
+	if viewLen != len(view) {
+		log.Panicf("golang.org/x/tools/go/packages: unexpected new packages during load of %s", lpkg.PkgPath)
+	}
+
+	lpkg.Types = tpkg
+	lpkg.IllTyped = false
+	return nil
+}
+
+// impliedLoadMode returns loadMode with its dependencies.
+func impliedLoadMode(loadMode LoadMode) LoadMode {
+	if loadMode&(NeedDeps|NeedTypes|NeedTypesInfo) != 0 {
+		// All these things require knowing the import graph.
+		loadMode |= NeedImports
+	}
+	if loadMode&NeedTypes != 0 {
+		// Types require the GoVersion from Module.
+		loadMode |= NeedModule
+	}
+
+	return loadMode
+}
+
+func usesExportData(cfg *Config) bool {
+	return cfg.Mode&NeedExportFile != 0 || cfg.Mode&NeedTypes != 0 && cfg.Mode&NeedDeps == 0
+}
+
+var _ interface{} = io.Discard // assert build toolchain is go1.16 or later
diff --git a/vendor/golang.org/x/tools/go/packages/visit.go b/vendor/golang.org/x/tools/go/packages/visit.go
new file mode 100644
index 0000000..df14ffd
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/packages/visit.go
@@ -0,0 +1,68 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packages
+
+import (
+	"fmt"
+	"os"
+	"sort"
+)
+
+// Visit visits all the packages in the import graph whose roots are
+// pkgs, calling the optional pre function the first time each package
+// is encountered (preorder), and the optional post function after a
+// package's dependencies have been visited (postorder).
+// The boolean result of pre(pkg) determines whether
+// the imports of package pkg are visited.
+func Visit(pkgs []*Package, pre func(*Package) bool, post func(*Package)) {
+	seen := make(map[*Package]bool)
+	var visit func(*Package)
+	visit = func(pkg *Package) {
+		if !seen[pkg] {
+			seen[pkg] = true
+
+			if pre == nil || pre(pkg) {
+				paths := make([]string, 0, len(pkg.Imports))
+				for path := range pkg.Imports {
+					paths = append(paths, path)
+				}
+				sort.Strings(paths) // Imports is a map, this makes visit stable
+				for _, path := range paths {
+					visit(pkg.Imports[path])
+				}
+			}
+
+			if post != nil {
+				post(pkg)
+			}
+		}
+	}
+	for _, pkg := range pkgs {
+		visit(pkg)
+	}
+}
+
+// PrintErrors prints to os.Stderr the accumulated errors of all
+// packages in the import graph rooted at pkgs, dependencies first.
+// PrintErrors returns the number of errors printed.
+func PrintErrors(pkgs []*Package) int {
+	var n int
+	errModules := make(map[*Module]bool)
+	Visit(pkgs, nil, func(pkg *Package) {
+		for _, err := range pkg.Errors {
+			fmt.Fprintln(os.Stderr, err)
+			n++
+		}
+
+		// Print pkg.Module.Error once if present.
+		mod := pkg.Module
+		if mod != nil && mod.Error != nil && !errModules[mod] {
+			errModules[mod] = true
+			fmt.Fprintln(os.Stderr, mod.Error.Err)
+			n++
+		}
+	})
+	return n
+}
diff --git a/vendor/golang.org/x/tools/go/ssa/TODO b/vendor/golang.org/x/tools/go/ssa/TODO
new file mode 100644
index 0000000..6c35253
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ssa/TODO
@@ -0,0 +1,16 @@
+-*- text -*-
+
+SSA Generics to-do list
+===========================
+
+DOCUMENTATION:
+- Read me for internals
+
+TYPE PARAMETERIZED GENERIC FUNCTIONS:
+- sanity.go updates.
+- Check source functions going to generics.
+- Tests, tests, tests...
+
+USAGE:
+- Back fill users for handling ssa.InstantiateGenerics being off.
+
diff --git a/vendor/golang.org/x/tools/go/ssa/block.go b/vendor/golang.org/x/tools/go/ssa/block.go
new file mode 100644
index 0000000..28170c7
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ssa/block.go
@@ -0,0 +1,113 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+import "fmt"
+
+// This file implements the BasicBlock type.
+
+// addEdge adds a control-flow graph edge from from to to.
+func addEdge(from, to *BasicBlock) {
+	from.Succs = append(from.Succs, to)
+	to.Preds = append(to.Preds, from)
+}
+
+// Parent returns the function that contains block b.
+func (b *BasicBlock) Parent() *Function { return b.parent }
+
+// String returns a human-readable label of this block.
+// It is not guaranteed unique within the function.
+func (b *BasicBlock) String() string {
+	return fmt.Sprintf("%d", b.Index)
+}
+
+// emit appends an instruction to the current basic block.
+// If the instruction defines a Value, it is returned.
+func (b *BasicBlock) emit(i Instruction) Value {
+	i.setBlock(b)
+	b.Instrs = append(b.Instrs, i)
+	v, _ := i.(Value)
+	return v
+}
+
+// predIndex returns the i such that b.Preds[i] == c or panics if
+// there is none.
+func (b *BasicBlock) predIndex(c *BasicBlock) int {
+	for i, pred := range b.Preds {
+		if pred == c {
+			return i
+		}
+	}
+	panic(fmt.Sprintf("no edge %s -> %s", c, b))
+}
+
+// hasPhi returns true if b.Instrs contains φ-nodes.
+func (b *BasicBlock) hasPhi() bool {
+	_, ok := b.Instrs[0].(*Phi)
+	return ok
+}
+
+// phis returns the prefix of b.Instrs containing all the block's φ-nodes.
+func (b *BasicBlock) phis() []Instruction {
+	for i, instr := range b.Instrs {
+		if _, ok := instr.(*Phi); !ok {
+			return b.Instrs[:i]
+		}
+	}
+	return nil // unreachable in well-formed blocks
+}
+
+// replacePred replaces all occurrences of p in b's predecessor list with q.
+// Ordinarily there should be at most one.
+func (b *BasicBlock) replacePred(p, q *BasicBlock) {
+	for i, pred := range b.Preds {
+		if pred == p {
+			b.Preds[i] = q
+		}
+	}
+}
+
+// replaceSucc replaces all occurrences of p in b's successor list with q.
+// Ordinarily there should be at most one.
+func (b *BasicBlock) replaceSucc(p, q *BasicBlock) {
+	for i, succ := range b.Succs {
+		if succ == p {
+			b.Succs[i] = q
+		}
+	}
+}
+
+// removePred removes all occurrences of p in b's
+// predecessor list and φ-nodes.
+// Ordinarily there should be at most one.
+func (b *BasicBlock) removePred(p *BasicBlock) {
+	phis := b.phis()
+
+	// We must preserve edge order for φ-nodes.
+	j := 0
+	for i, pred := range b.Preds {
+		if pred != p {
+			b.Preds[j] = b.Preds[i]
+			// Strike out φ-edge too.
+			for _, instr := range phis {
+				phi := instr.(*Phi)
+				phi.Edges[j] = phi.Edges[i]
+			}
+			j++
+		}
+	}
+	// Nil out b.Preds[j:] and φ-edges[j:] to aid GC.
+	for i := j; i < len(b.Preds); i++ {
+		b.Preds[i] = nil
+		for _, instr := range phis {
+			instr.(*Phi).Edges[i] = nil
+		}
+	}
+	b.Preds = b.Preds[:j]
+	for _, instr := range phis {
+		phi := instr.(*Phi)
+		phi.Edges = phi.Edges[:j]
+	}
+}
diff --git a/vendor/golang.org/x/tools/go/ssa/blockopt.go b/vendor/golang.org/x/tools/go/ssa/blockopt.go
new file mode 100644
index 0000000..7dabce8
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ssa/blockopt.go
@@ -0,0 +1,183 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// Simple block optimizations to simplify the control flow graph.
+
+// TODO(adonovan): opt: instead of creating several "unreachable" blocks
+// per function in the Builder, reuse a single one (e.g. at Blocks[1])
+// to reduce garbage.
+
+import (
+	"fmt"
+	"os"
+)
+
+// If true, perform sanity checking and show progress at each
+// successive iteration of optimizeBlocks.  Very verbose.
+const debugBlockOpt = false
+
+// markReachable sets Index=-1 for all blocks reachable from b.
+func markReachable(b *BasicBlock) {
+	b.Index = -1
+	for _, succ := range b.Succs {
+		if succ.Index == 0 {
+			markReachable(succ)
+		}
+	}
+}
+
+// deleteUnreachableBlocks marks all reachable blocks of f and
+// eliminates (nils) all others, including possibly cyclic subgraphs.
+func deleteUnreachableBlocks(f *Function) {
+	const white, black = 0, -1
+	// We borrow b.Index temporarily as the mark bit.
+	for _, b := range f.Blocks {
+		b.Index = white
+	}
+	markReachable(f.Blocks[0])
+	if f.Recover != nil {
+		markReachable(f.Recover)
+	}
+	for i, b := range f.Blocks {
+		if b.Index == white {
+			for _, c := range b.Succs {
+				if c.Index == black {
+					c.removePred(b) // delete white->black edge
+				}
+			}
+			if debugBlockOpt {
+				fmt.Fprintln(os.Stderr, "unreachable", b)
+			}
+			f.Blocks[i] = nil // delete b
+		}
+	}
+	f.removeNilBlocks()
+}
+
+// jumpThreading attempts to apply simple jump-threading to block b,
+// in which a->b->c become a->c if b is just a Jump.
+// The result is true if the optimization was applied.
+func jumpThreading(f *Function, b *BasicBlock) bool {
+	if b.Index == 0 {
+		return false // don't apply to entry block
+	}
+	if b.Instrs == nil {
+		return false
+	}
+	if _, ok := b.Instrs[0].(*Jump); !ok {
+		return false // not just a jump
+	}
+	c := b.Succs[0]
+	if c == b {
+		return false // don't apply to degenerate jump-to-self.
+	}
+	if c.hasPhi() {
+		return false // not sound without more effort
+	}
+	for j, a := range b.Preds {
+		a.replaceSucc(b, c)
+
+		// If a now has two edges to c, replace its degenerate If by Jump.
+		if len(a.Succs) == 2 && a.Succs[0] == c && a.Succs[1] == c {
+			jump := new(Jump)
+			jump.setBlock(a)
+			a.Instrs[len(a.Instrs)-1] = jump
+			a.Succs = a.Succs[:1]
+			c.removePred(b)
+		} else {
+			if j == 0 {
+				c.replacePred(b, a)
+			} else {
+				c.Preds = append(c.Preds, a)
+			}
+		}
+
+		if debugBlockOpt {
+			fmt.Fprintln(os.Stderr, "jumpThreading", a, b, c)
+		}
+	}
+	f.Blocks[b.Index] = nil // delete b
+	return true
+}
+
+// fuseBlocks attempts to apply the block fusion optimization to block
+// a, in which a->b becomes ab if len(a.Succs)==len(b.Preds)==1.
+// The result is true if the optimization was applied.
+func fuseBlocks(f *Function, a *BasicBlock) bool {
+	if len(a.Succs) != 1 {
+		return false
+	}
+	b := a.Succs[0]
+	if len(b.Preds) != 1 {
+		return false
+	}
+
+	// Degenerate &&/|| ops may result in a straight-line CFG
+	// containing φ-nodes. (Ideally we'd replace such them with
+	// their sole operand but that requires Referrers, built later.)
+	if b.hasPhi() {
+		return false // not sound without further effort
+	}
+
+	// Eliminate jump at end of A, then copy all of B across.
+	a.Instrs = append(a.Instrs[:len(a.Instrs)-1], b.Instrs...)
+	for _, instr := range b.Instrs {
+		instr.setBlock(a)
+	}
+
+	// A inherits B's successors
+	a.Succs = append(a.succs2[:0], b.Succs...)
+
+	// Fix up Preds links of all successors of B.
+	for _, c := range b.Succs {
+		c.replacePred(b, a)
+	}
+
+	if debugBlockOpt {
+		fmt.Fprintln(os.Stderr, "fuseBlocks", a, b)
+	}
+
+	f.Blocks[b.Index] = nil // delete b
+	return true
+}
+
+// optimizeBlocks() performs some simple block optimizations on a
+// completed function: dead block elimination, block fusion, jump
+// threading.
+func optimizeBlocks(f *Function) {
+	deleteUnreachableBlocks(f)
+
+	// Loop until no further progress.
+	changed := true
+	for changed {
+		changed = false
+
+		if debugBlockOpt {
+			f.WriteTo(os.Stderr)
+			mustSanityCheck(f, nil)
+		}
+
+		for _, b := range f.Blocks {
+			// f.Blocks will temporarily contain nils to indicate
+			// deleted blocks; we remove them at the end.
+			if b == nil {
+				continue
+			}
+
+			// Fuse blocks.  b->c becomes bc.
+			if fuseBlocks(f, b) {
+				changed = true
+			}
+
+			// a->b->c becomes a->c if b contains only a Jump.
+			if jumpThreading(f, b) {
+				changed = true
+				continue // (b was disconnected)
+			}
+		}
+	}
+	f.removeNilBlocks()
+}
diff --git a/vendor/golang.org/x/tools/go/ssa/builder.go b/vendor/golang.org/x/tools/go/ssa/builder.go
new file mode 100644
index 0000000..55943e4
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ssa/builder.go
@@ -0,0 +1,3276 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// This file defines the builder, which builds SSA-form IR for function bodies.
+//
+// SSA construction has two phases, "create" and "build". First, one
+// or more packages are created in any order by a sequence of calls to
+// CreatePackage, either from syntax or from mere type information.
+// Each created package has a complete set of Members (const, var,
+// type, func) that can be accessed through methods like
+// Program.FuncValue.
+//
+// It is not necessary to call CreatePackage for all dependencies of
+// each syntax package, only for its direct imports. (In future
+// perhaps even this restriction may be lifted.)
+//
+// Second, packages created from syntax are built, by one or more
+// calls to Package.Build, which may be concurrent; or by a call to
+// Program.Build, which builds all packages in parallel. Building
+// traverses the type-annotated syntax tree of each function body and
+// creates SSA-form IR, a control-flow graph of instructions,
+// populating fields such as Function.Body, .Params, and others.
+//
+// Building may create additional methods, including:
+// - wrapper methods (e.g. for embeddding, or implicit &recv)
+// - bound method closures (e.g. for use(recv.f))
+// - thunks (e.g. for use(I.f) or use(T.f))
+// - generic instances (e.g. to produce f[int] from f[any]).
+// As these methods are created, they are added to the build queue,
+// and then processed in turn, until a fixed point is reached,
+// Since these methods might belong to packages that were not
+// created (by a call to CreatePackage), their Pkg field is unset.
+//
+// Instances of generic functions may be either instantiated (f[int]
+// is a copy of f[T] with substitutions) or wrapped (f[int] delegates
+// to f[T]), depending on the availability of generic syntax and the
+// InstantiateGenerics mode flag.
+//
+// Each package has an initializer function named "init" that calls
+// the initializer functions of each direct import, computes and
+// assigns the initial value of each global variable, and calls each
+// source-level function named "init". (These generate SSA functions
+// named "init#1", "init#2", etc.)
+//
+// Runtime types
+//
+// Each MakeInterface operation is a conversion from a non-interface
+// type to an interface type. The semantics of this operation requires
+// a runtime type descriptor, which is the type portion of an
+// interface, and the value abstracted by reflect.Type.
+//
+// The program accumulates all non-parameterized types that are
+// encountered as MakeInterface operands, along with all types that
+// may be derived from them using reflection. This set is available as
+// Program.RuntimeTypes, and the methods of these types may be
+// reachable via interface calls or reflection even if they are never
+// referenced from the SSA IR. (In practice, algorithms such as RTA
+// that compute reachability from package main perform their own
+// tracking of runtime types at a finer grain, so this feature is not
+// very useful.)
+//
+// Function literals
+//
+// Anonymous functions must be built as soon as they are encountered,
+// as it may affect locals of the enclosing function, but they are not
+// marked 'built' until the end of the outermost enclosing function.
+// (Among other things, this causes them to be logged in top-down order.)
+//
+// The Function.build fields determines the algorithm for building the
+// function body. It is cleared to mark that building is complete.
+
+import (
+	"fmt"
+	"go/ast"
+	"go/constant"
+	"go/token"
+	"go/types"
+	"os"
+	"runtime"
+	"sync"
+
+	"golang.org/x/tools/internal/aliases"
+	"golang.org/x/tools/internal/typeparams"
+	"golang.org/x/tools/internal/versions"
+)
+
+type opaqueType struct{ name string }
+
+func (t *opaqueType) String() string         { return t.name }
+func (t *opaqueType) Underlying() types.Type { return t }
+
+var (
+	varOk    = newVar("ok", tBool)
+	varIndex = newVar("index", tInt)
+
+	// Type constants.
+	tBool       = types.Typ[types.Bool]
+	tByte       = types.Typ[types.Byte]
+	tInt        = types.Typ[types.Int]
+	tInvalid    = types.Typ[types.Invalid]
+	tString     = types.Typ[types.String]
+	tUntypedNil = types.Typ[types.UntypedNil]
+
+	tRangeIter  = &opaqueType{"iter"}                         // the type of all "range" iterators
+	tDeferStack = types.NewPointer(&opaqueType{"deferStack"}) // the type of a "deferStack" from ssa:deferstack()
+	tEface      = types.NewInterfaceType(nil, nil).Complete()
+
+	// SSA Value constants.
+	vZero  = intConst(0)
+	vOne   = intConst(1)
+	vTrue  = NewConst(constant.MakeBool(true), tBool)
+	vFalse = NewConst(constant.MakeBool(false), tBool)
+
+	jReady = intConst(0)  // range-over-func jump is READY
+	jBusy  = intConst(-1) // range-over-func jump is BUSY
+	jDone  = intConst(-2) // range-over-func jump is DONE
+
+	// The ssa:deferstack intrinsic returns the current function's defer stack.
+	vDeferStack = &Builtin{
+		name: "ssa:deferstack",
+		sig:  types.NewSignatureType(nil, nil, nil, nil, types.NewTuple(anonVar(tDeferStack)), false),
+	}
+)
+
+// builder holds state associated with the package currently being built.
+// Its methods contain all the logic for AST-to-SSA conversion.
+//
+// All Functions belong to the same Program.
+//
+// builders are not thread-safe.
+type builder struct {
+	fns []*Function // Functions that have finished their CREATE phases.
+
+	finished int // finished is the length of the prefix of fns containing built functions.
+
+	// The task of building shared functions within the builder.
+	// Shared functions are ones the the builder may either create or lookup.
+	// These may be built by other builders in parallel.
+	// The task is done when the builder has finished iterating, and it
+	// waits for all shared functions to finish building.
+	// nil implies there are no hared functions to wait on.
+	buildshared *task
+}
+
+// shared is done when the builder has built all of the
+// enqueued functions to a fixed-point.
+func (b *builder) shared() *task {
+	if b.buildshared == nil { // lazily-initialize
+		b.buildshared = &task{done: make(chan unit)}
+	}
+	return b.buildshared
+}
+
+// enqueue fn to be built by the builder.
+func (b *builder) enqueue(fn *Function) {
+	b.fns = append(b.fns, fn)
+}
+
+// waitForSharedFunction indicates that the builder should wait until
+// the potentially shared function fn has finished building.
+//
+// This should include any functions that may be built by other
+// builders.
+func (b *builder) waitForSharedFunction(fn *Function) {
+	if fn.buildshared != nil { // maybe need to wait?
+		s := b.shared()
+		s.addEdge(fn.buildshared)
+	}
+}
+
+// cond emits to fn code to evaluate boolean condition e and jump
+// to t or f depending on its value, performing various simplifications.
+//
+// Postcondition: fn.currentBlock is nil.
+func (b *builder) cond(fn *Function, e ast.Expr, t, f *BasicBlock) {
+	switch e := e.(type) {
+	case *ast.ParenExpr:
+		b.cond(fn, e.X, t, f)
+		return
+
+	case *ast.BinaryExpr:
+		switch e.Op {
+		case token.LAND:
+			ltrue := fn.newBasicBlock("cond.true")
+			b.cond(fn, e.X, ltrue, f)
+			fn.currentBlock = ltrue
+			b.cond(fn, e.Y, t, f)
+			return
+
+		case token.LOR:
+			lfalse := fn.newBasicBlock("cond.false")
+			b.cond(fn, e.X, t, lfalse)
+			fn.currentBlock = lfalse
+			b.cond(fn, e.Y, t, f)
+			return
+		}
+
+	case *ast.UnaryExpr:
+		if e.Op == token.NOT {
+			b.cond(fn, e.X, f, t)
+			return
+		}
+	}
+
+	// A traditional compiler would simplify "if false" (etc) here
+	// but we do not, for better fidelity to the source code.
+	//
+	// The value of a constant condition may be platform-specific,
+	// and may cause blocks that are reachable in some configuration
+	// to be hidden from subsequent analyses such as bug-finding tools.
+	emitIf(fn, b.expr(fn, e), t, f)
+}
+
+// logicalBinop emits code to fn to evaluate e, a &&- or
+// ||-expression whose reified boolean value is wanted.
+// The value is returned.
+func (b *builder) logicalBinop(fn *Function, e *ast.BinaryExpr) Value {
+	rhs := fn.newBasicBlock("binop.rhs")
+	done := fn.newBasicBlock("binop.done")
+
+	// T(e) = T(e.X) = T(e.Y) after untyped constants have been
+	// eliminated.
+	// TODO(adonovan): not true; MyBool==MyBool yields UntypedBool.
+	t := fn.typeOf(e)
+
+	var short Value // value of the short-circuit path
+	switch e.Op {
+	case token.LAND:
+		b.cond(fn, e.X, rhs, done)
+		short = NewConst(constant.MakeBool(false), t)
+
+	case token.LOR:
+		b.cond(fn, e.X, done, rhs)
+		short = NewConst(constant.MakeBool(true), t)
+	}
+
+	// Is rhs unreachable?
+	if rhs.Preds == nil {
+		// Simplify false&&y to false, true||y to true.
+		fn.currentBlock = done
+		return short
+	}
+
+	// Is done unreachable?
+	if done.Preds == nil {
+		// Simplify true&&y (or false||y) to y.
+		fn.currentBlock = rhs
+		return b.expr(fn, e.Y)
+	}
+
+	// All edges from e.X to done carry the short-circuit value.
+	var edges []Value
+	for range done.Preds {
+		edges = append(edges, short)
+	}
+
+	// The edge from e.Y to done carries the value of e.Y.
+	fn.currentBlock = rhs
+	edges = append(edges, b.expr(fn, e.Y))
+	emitJump(fn, done)
+	fn.currentBlock = done
+
+	phi := &Phi{Edges: edges, Comment: e.Op.String()}
+	phi.pos = e.OpPos
+	phi.typ = t
+	return done.emit(phi)
+}
+
+// exprN lowers a multi-result expression e to SSA form, emitting code
+// to fn and returning a single Value whose type is a *types.Tuple.
+// The caller must access the components via Extract.
+//
+// Multi-result expressions include CallExprs in a multi-value
+// assignment or return statement, and "value,ok" uses of
+// TypeAssertExpr, IndexExpr (when X is a map), and UnaryExpr (when Op
+// is token.ARROW).
+func (b *builder) exprN(fn *Function, e ast.Expr) Value {
+	typ := fn.typeOf(e).(*types.Tuple)
+	switch e := e.(type) {
+	case *ast.ParenExpr:
+		return b.exprN(fn, e.X)
+
+	case *ast.CallExpr:
+		// Currently, no built-in function nor type conversion
+		// has multiple results, so we can avoid some of the
+		// cases for single-valued CallExpr.
+		var c Call
+		b.setCall(fn, e, &c.Call)
+		c.typ = typ
+		return fn.emit(&c)
+
+	case *ast.IndexExpr:
+		mapt := typeparams.CoreType(fn.typeOf(e.X)).(*types.Map) // ,ok must be a map.
+		lookup := &Lookup{
+			X:       b.expr(fn, e.X),
+			Index:   emitConv(fn, b.expr(fn, e.Index), mapt.Key()),
+			CommaOk: true,
+		}
+		lookup.setType(typ)
+		lookup.setPos(e.Lbrack)
+		return fn.emit(lookup)
+
+	case *ast.TypeAssertExpr:
+		return emitTypeTest(fn, b.expr(fn, e.X), typ.At(0).Type(), e.Lparen)
+
+	case *ast.UnaryExpr: // must be receive <-
+		unop := &UnOp{
+			Op:      token.ARROW,
+			X:       b.expr(fn, e.X),
+			CommaOk: true,
+		}
+		unop.setType(typ)
+		unop.setPos(e.OpPos)
+		return fn.emit(unop)
+	}
+	panic(fmt.Sprintf("exprN(%T) in %s", e, fn))
+}
+
+// builtin emits to fn SSA instructions to implement a call to the
+// built-in function obj with the specified arguments
+// and return type.  It returns the value defined by the result.
+//
+// The result is nil if no special handling was required; in this case
+// the caller should treat this like an ordinary library function
+// call.
+func (b *builder) builtin(fn *Function, obj *types.Builtin, args []ast.Expr, typ types.Type, pos token.Pos) Value {
+	typ = fn.typ(typ)
+	switch obj.Name() {
+	case "make":
+		switch ct := typeparams.CoreType(typ).(type) {
+		case *types.Slice:
+			n := b.expr(fn, args[1])
+			m := n
+			if len(args) == 3 {
+				m = b.expr(fn, args[2])
+			}
+			if m, ok := m.(*Const); ok {
+				// treat make([]T, n, m) as new([m]T)[:n]
+				cap := m.Int64()
+				at := types.NewArray(ct.Elem(), cap)
+				v := &Slice{
+					X:    emitNew(fn, at, pos, "makeslice"),
+					High: n,
+				}
+				v.setPos(pos)
+				v.setType(typ)
+				return fn.emit(v)
+			}
+			v := &MakeSlice{
+				Len: n,
+				Cap: m,
+			}
+			v.setPos(pos)
+			v.setType(typ)
+			return fn.emit(v)
+
+		case *types.Map:
+			var res Value
+			if len(args) == 2 {
+				res = b.expr(fn, args[1])
+			}
+			v := &MakeMap{Reserve: res}
+			v.setPos(pos)
+			v.setType(typ)
+			return fn.emit(v)
+
+		case *types.Chan:
+			var sz Value = vZero
+			if len(args) == 2 {
+				sz = b.expr(fn, args[1])
+			}
+			v := &MakeChan{Size: sz}
+			v.setPos(pos)
+			v.setType(typ)
+			return fn.emit(v)
+		}
+
+	case "new":
+		return emitNew(fn, typeparams.MustDeref(typ), pos, "new")
+
+	case "len", "cap":
+		// Special case: len or cap of an array or *array is
+		// based on the type, not the value which may be nil.
+		// We must still evaluate the value, though.  (If it
+		// was side-effect free, the whole call would have
+		// been constant-folded.)
+		t := typeparams.Deref(fn.typeOf(args[0]))
+		if at, ok := typeparams.CoreType(t).(*types.Array); ok {
+			b.expr(fn, args[0]) // for effects only
+			return intConst(at.Len())
+		}
+		// Otherwise treat as normal.
+
+	case "panic":
+		fn.emit(&Panic{
+			X:   emitConv(fn, b.expr(fn, args[0]), tEface),
+			pos: pos,
+		})
+		fn.currentBlock = fn.newBasicBlock("unreachable")
+		return vTrue // any non-nil Value will do
+	}
+	return nil // treat all others as a regular function call
+}
+
+// addr lowers a single-result addressable expression e to SSA form,
+// emitting code to fn and returning the location (an lvalue) defined
+// by the expression.
+//
+// If escaping is true, addr marks the base variable of the
+// addressable expression e as being a potentially escaping pointer
+// value.  For example, in this code:
+//
+//	a := A{
+//	  b: [1]B{B{c: 1}}
+//	}
+//	return &a.b[0].c
+//
+// the application of & causes a.b[0].c to have its address taken,
+// which means that ultimately the local variable a must be
+// heap-allocated.  This is a simple but very conservative escape
+// analysis.
+//
+// Operations forming potentially escaping pointers include:
+// - &x, including when implicit in method call or composite literals.
+// - a[:] iff a is an array (not *array)
+// - references to variables in lexically enclosing functions.
+func (b *builder) addr(fn *Function, e ast.Expr, escaping bool) lvalue {
+	switch e := e.(type) {
+	case *ast.Ident:
+		if isBlankIdent(e) {
+			return blank{}
+		}
+		obj := fn.objectOf(e).(*types.Var)
+		var v Value
+		if g := fn.Prog.packageLevelMember(obj); g != nil {
+			v = g.(*Global) // var (address)
+		} else {
+			v = fn.lookup(obj, escaping)
+		}
+		return &address{addr: v, pos: e.Pos(), expr: e}
+
+	case *ast.CompositeLit:
+		typ := typeparams.Deref(fn.typeOf(e))
+		var v *Alloc
+		if escaping {
+			v = emitNew(fn, typ, e.Lbrace, "complit")
+		} else {
+			v = emitLocal(fn, typ, e.Lbrace, "complit")
+		}
+		var sb storebuf
+		b.compLit(fn, v, e, true, &sb)
+		sb.emit(fn)
+		return &address{addr: v, pos: e.Lbrace, expr: e}
+
+	case *ast.ParenExpr:
+		return b.addr(fn, e.X, escaping)
+
+	case *ast.SelectorExpr:
+		sel := fn.selection(e)
+		if sel == nil {
+			// qualified identifier
+			return b.addr(fn, e.Sel, escaping)
+		}
+		if sel.kind != types.FieldVal {
+			panic(sel)
+		}
+		wantAddr := true
+		v := b.receiver(fn, e.X, wantAddr, escaping, sel)
+		index := sel.index[len(sel.index)-1]
+		fld := fieldOf(typeparams.MustDeref(v.Type()), index) // v is an addr.
+
+		// Due to the two phases of resolving AssignStmt, a panic from x.f = p()
+		// when x is nil is required to come after the side-effects of
+		// evaluating x and p().
+		emit := func(fn *Function) Value {
+			return emitFieldSelection(fn, v, index, true, e.Sel)
+		}
+		return &lazyAddress{addr: emit, t: fld.Type(), pos: e.Sel.Pos(), expr: e.Sel}
+
+	case *ast.IndexExpr:
+		xt := fn.typeOf(e.X)
+		elem, mode := indexType(xt)
+		var x Value
+		var et types.Type
+		switch mode {
+		case ixArrVar: // array, array|slice, array|*array, or array|*array|slice.
+			x = b.addr(fn, e.X, escaping).address(fn)
+			et = types.NewPointer(elem)
+		case ixVar: // *array, slice, *array|slice
+			x = b.expr(fn, e.X)
+			et = types.NewPointer(elem)
+		case ixMap:
+			mt := typeparams.CoreType(xt).(*types.Map)
+			return &element{
+				m:   b.expr(fn, e.X),
+				k:   emitConv(fn, b.expr(fn, e.Index), mt.Key()),
+				t:   mt.Elem(),
+				pos: e.Lbrack,
+			}
+		default:
+			panic("unexpected container type in IndexExpr: " + xt.String())
+		}
+		index := b.expr(fn, e.Index)
+		if isUntyped(index.Type()) {
+			index = emitConv(fn, index, tInt)
+		}
+		// Due to the two phases of resolving AssignStmt, a panic from x[i] = p()
+		// when x is nil or i is out-of-bounds is required to come after the
+		// side-effects of evaluating x, i and p().
+		emit := func(fn *Function) Value {
+			v := &IndexAddr{
+				X:     x,
+				Index: index,
+			}
+			v.setPos(e.Lbrack)
+			v.setType(et)
+			return fn.emit(v)
+		}
+		return &lazyAddress{addr: emit, t: typeparams.MustDeref(et), pos: e.Lbrack, expr: e}
+
+	case *ast.StarExpr:
+		return &address{addr: b.expr(fn, e.X), pos: e.Star, expr: e}
+	}
+
+	panic(fmt.Sprintf("unexpected address expression: %T", e))
+}
+
+type store struct {
+	lhs lvalue
+	rhs Value
+}
+
+type storebuf struct{ stores []store }
+
+func (sb *storebuf) store(lhs lvalue, rhs Value) {
+	sb.stores = append(sb.stores, store{lhs, rhs})
+}
+
+func (sb *storebuf) emit(fn *Function) {
+	for _, s := range sb.stores {
+		s.lhs.store(fn, s.rhs)
+	}
+}
+
+// assign emits to fn code to initialize the lvalue loc with the value
+// of expression e.  If isZero is true, assign assumes that loc holds
+// the zero value for its type.
+//
+// This is equivalent to loc.store(fn, b.expr(fn, e)), but may generate
+// better code in some cases, e.g., for composite literals in an
+// addressable location.
+//
+// If sb is not nil, assign generates code to evaluate expression e, but
+// not to update loc.  Instead, the necessary stores are appended to the
+// storebuf sb so that they can be executed later.  This allows correct
+// in-place update of existing variables when the RHS is a composite
+// literal that may reference parts of the LHS.
+func (b *builder) assign(fn *Function, loc lvalue, e ast.Expr, isZero bool, sb *storebuf) {
+	// Can we initialize it in place?
+	if e, ok := unparen(e).(*ast.CompositeLit); ok {
+		// A CompositeLit never evaluates to a pointer,
+		// so if the type of the location is a pointer,
+		// an &-operation is implied.
+		if !is[blank](loc) && isPointerCore(loc.typ()) { // avoid calling blank.typ()
+			ptr := b.addr(fn, e, true).address(fn)
+			// copy address
+			if sb != nil {
+				sb.store(loc, ptr)
+			} else {
+				loc.store(fn, ptr)
+			}
+			return
+		}
+
+		if _, ok := loc.(*address); ok {
+			if isNonTypeParamInterface(loc.typ()) {
+				// e.g. var x interface{} = T{...}
+				// Can't in-place initialize an interface value.
+				// Fall back to copying.
+			} else {
+				// x = T{...} or x := T{...}
+				addr := loc.address(fn)
+				if sb != nil {
+					b.compLit(fn, addr, e, isZero, sb)
+				} else {
+					var sb storebuf
+					b.compLit(fn, addr, e, isZero, &sb)
+					sb.emit(fn)
+				}
+
+				// Subtle: emit debug ref for aggregate types only;
+				// slice and map are handled by store ops in compLit.
+				switch typeparams.CoreType(loc.typ()).(type) {
+				case *types.Struct, *types.Array:
+					emitDebugRef(fn, e, addr, true)
+				}
+
+				return
+			}
+		}
+	}
+
+	// simple case: just copy
+	rhs := b.expr(fn, e)
+	if sb != nil {
+		sb.store(loc, rhs)
+	} else {
+		loc.store(fn, rhs)
+	}
+}
+
+// expr lowers a single-result expression e to SSA form, emitting code
+// to fn and returning the Value defined by the expression.
+func (b *builder) expr(fn *Function, e ast.Expr) Value {
+	e = unparen(e)
+
+	tv := fn.info.Types[e]
+
+	// Is expression a constant?
+	if tv.Value != nil {
+		return NewConst(tv.Value, fn.typ(tv.Type))
+	}
+
+	var v Value
+	if tv.Addressable() {
+		// Prefer pointer arithmetic ({Index,Field}Addr) followed
+		// by Load over subelement extraction (e.g. Index, Field),
+		// to avoid large copies.
+		v = b.addr(fn, e, false).load(fn)
+	} else {
+		v = b.expr0(fn, e, tv)
+	}
+	if fn.debugInfo() {
+		emitDebugRef(fn, e, v, false)
+	}
+	return v
+}
+
+func (b *builder) expr0(fn *Function, e ast.Expr, tv types.TypeAndValue) Value {
+	switch e := e.(type) {
+	case *ast.BasicLit:
+		panic("non-constant BasicLit") // unreachable
+
+	case *ast.FuncLit:
+		/* function literal */
+		anon := &Function{
+			name:           fmt.Sprintf("%s$%d", fn.Name(), 1+len(fn.AnonFuncs)),
+			Signature:      fn.typeOf(e.Type).(*types.Signature),
+			pos:            e.Type.Func,
+			parent:         fn,
+			anonIdx:        int32(len(fn.AnonFuncs)),
+			Pkg:            fn.Pkg,
+			Prog:           fn.Prog,
+			syntax:         e,
+			info:           fn.info,
+			goversion:      fn.goversion,
+			build:          (*builder).buildFromSyntax,
+			topLevelOrigin: nil,           // use anonIdx to lookup an anon instance's origin.
+			typeparams:     fn.typeparams, // share the parent's type parameters.
+			typeargs:       fn.typeargs,   // share the parent's type arguments.
+			subst:          fn.subst,      // share the parent's type substitutions.
+			uniq:           fn.uniq,       // start from parent's unique values
+		}
+		fn.AnonFuncs = append(fn.AnonFuncs, anon)
+		// Build anon immediately, as it may cause fn's locals to escape.
+		// (It is not marked 'built' until the end of the enclosing FuncDecl.)
+		anon.build(b, anon)
+		fn.uniq = anon.uniq // resume after anon's unique values
+		if anon.FreeVars == nil {
+			return anon
+		}
+		v := &MakeClosure{Fn: anon}
+		v.setType(fn.typ(tv.Type))
+		for _, fv := range anon.FreeVars {
+			v.Bindings = append(v.Bindings, fv.outer)
+			fv.outer = nil
+		}
+		return fn.emit(v)
+
+	case *ast.TypeAssertExpr: // single-result form only
+		return emitTypeAssert(fn, b.expr(fn, e.X), fn.typ(tv.Type), e.Lparen)
+
+	case *ast.CallExpr:
+		if fn.info.Types[e.Fun].IsType() {
+			// Explicit type conversion, e.g. string(x) or big.Int(x)
+			x := b.expr(fn, e.Args[0])
+			y := emitConv(fn, x, fn.typ(tv.Type))
+			if y != x {
+				switch y := y.(type) {
+				case *Convert:
+					y.pos = e.Lparen
+				case *ChangeType:
+					y.pos = e.Lparen
+				case *MakeInterface:
+					y.pos = e.Lparen
+				case *SliceToArrayPointer:
+					y.pos = e.Lparen
+				case *UnOp: // conversion from slice to array.
+					y.pos = e.Lparen
+				}
+			}
+			return y
+		}
+		// Call to "intrinsic" built-ins, e.g. new, make, panic.
+		if id, ok := unparen(e.Fun).(*ast.Ident); ok {
+			if obj, ok := fn.info.Uses[id].(*types.Builtin); ok {
+				if v := b.builtin(fn, obj, e.Args, fn.typ(tv.Type), e.Lparen); v != nil {
+					return v
+				}
+			}
+		}
+		// Regular function call.
+		var v Call
+		b.setCall(fn, e, &v.Call)
+		v.setType(fn.typ(tv.Type))
+		return fn.emit(&v)
+
+	case *ast.UnaryExpr:
+		switch e.Op {
+		case token.AND: // &X --- potentially escaping.
+			addr := b.addr(fn, e.X, true)
+			if _, ok := unparen(e.X).(*ast.StarExpr); ok {
+				// &*p must panic if p is nil (http://golang.org/s/go12nil).
+				// For simplicity, we'll just (suboptimally) rely
+				// on the side effects of a load.
+				// TODO(adonovan): emit dedicated nilcheck.
+				addr.load(fn)
+			}
+			return addr.address(fn)
+		case token.ADD:
+			return b.expr(fn, e.X)
+		case token.NOT, token.ARROW, token.SUB, token.XOR: // ! <- - ^
+			v := &UnOp{
+				Op: e.Op,
+				X:  b.expr(fn, e.X),
+			}
+			v.setPos(e.OpPos)
+			v.setType(fn.typ(tv.Type))
+			return fn.emit(v)
+		default:
+			panic(e.Op)
+		}
+
+	case *ast.BinaryExpr:
+		switch e.Op {
+		case token.LAND, token.LOR:
+			return b.logicalBinop(fn, e)
+		case token.SHL, token.SHR:
+			fallthrough
+		case token.ADD, token.SUB, token.MUL, token.QUO, token.REM, token.AND, token.OR, token.XOR, token.AND_NOT:
+			return emitArith(fn, e.Op, b.expr(fn, e.X), b.expr(fn, e.Y), fn.typ(tv.Type), e.OpPos)
+
+		case token.EQL, token.NEQ, token.GTR, token.LSS, token.LEQ, token.GEQ:
+			cmp := emitCompare(fn, e.Op, b.expr(fn, e.X), b.expr(fn, e.Y), e.OpPos)
+			// The type of x==y may be UntypedBool.
+			return emitConv(fn, cmp, types.Default(fn.typ(tv.Type)))
+		default:
+			panic("illegal op in BinaryExpr: " + e.Op.String())
+		}
+
+	case *ast.SliceExpr:
+		var low, high, max Value
+		var x Value
+		xtyp := fn.typeOf(e.X)
+		switch typeparams.CoreType(xtyp).(type) {
+		case *types.Array:
+			// Potentially escaping.
+			x = b.addr(fn, e.X, true).address(fn)
+		case *types.Basic, *types.Slice, *types.Pointer: // *array
+			x = b.expr(fn, e.X)
+		default:
+			// core type exception?
+			if isBytestring(xtyp) {
+				x = b.expr(fn, e.X) // bytestring is handled as string and []byte.
+			} else {
+				panic("unexpected sequence type in SliceExpr")
+			}
+		}
+		if e.Low != nil {
+			low = b.expr(fn, e.Low)
+		}
+		if e.High != nil {
+			high = b.expr(fn, e.High)
+		}
+		if e.Slice3 {
+			max = b.expr(fn, e.Max)
+		}
+		v := &Slice{
+			X:    x,
+			Low:  low,
+			High: high,
+			Max:  max,
+		}
+		v.setPos(e.Lbrack)
+		v.setType(fn.typ(tv.Type))
+		return fn.emit(v)
+
+	case *ast.Ident:
+		obj := fn.info.Uses[e]
+		// Universal built-in or nil?
+		switch obj := obj.(type) {
+		case *types.Builtin:
+			return &Builtin{name: obj.Name(), sig: fn.instanceType(e).(*types.Signature)}
+		case *types.Nil:
+			return zeroConst(fn.instanceType(e))
+		}
+
+		// Package-level func or var?
+		// (obj must belong to same package or a direct import.)
+		if v := fn.Prog.packageLevelMember(obj); v != nil {
+			if g, ok := v.(*Global); ok {
+				return emitLoad(fn, g) // var (address)
+			}
+			callee := v.(*Function) // (func)
+			if callee.typeparams.Len() > 0 {
+				targs := fn.subst.types(instanceArgs(fn.info, e))
+				callee = callee.instance(targs, b)
+			}
+			return callee
+		}
+		// Local var.
+		return emitLoad(fn, fn.lookup(obj.(*types.Var), false)) // var (address)
+
+	case *ast.SelectorExpr:
+		sel := fn.selection(e)
+		if sel == nil {
+			// builtin unsafe.{Add,Slice}
+			if obj, ok := fn.info.Uses[e.Sel].(*types.Builtin); ok {
+				return &Builtin{name: obj.Name(), sig: fn.typ(tv.Type).(*types.Signature)}
+			}
+			// qualified identifier
+			return b.expr(fn, e.Sel)
+		}
+		switch sel.kind {
+		case types.MethodExpr:
+			// (*T).f or T.f, the method f from the method-set of type T.
+			// The result is a "thunk".
+			thunk := createThunk(fn.Prog, sel)
+			b.enqueue(thunk)
+			return emitConv(fn, thunk, fn.typ(tv.Type))
+
+		case types.MethodVal:
+			// e.f where e is an expression and f is a method.
+			// The result is a "bound".
+			obj := sel.obj.(*types.Func)
+			rt := fn.typ(recvType(obj))
+			wantAddr := isPointer(rt)
+			escaping := true
+			v := b.receiver(fn, e.X, wantAddr, escaping, sel)
+
+			if types.IsInterface(rt) {
+				// If v may be an interface type I (after instantiating),
+				// we must emit a check that v is non-nil.
+				if recv, ok := aliases.Unalias(sel.recv).(*types.TypeParam); ok {
+					// Emit a nil check if any possible instantiation of the
+					// type parameter is an interface type.
+					if typeSetOf(recv).Len() > 0 {
+						// recv has a concrete term its typeset.
+						// So it cannot be instantiated as an interface.
+						//
+						// Example:
+						// func _[T interface{~int; Foo()}] () {
+						//    var v T
+						//    _ = v.Foo // <-- MethodVal
+						// }
+					} else {
+						// rt may be instantiated as an interface.
+						// Emit nil check: typeassert (any(v)).(any).
+						emitTypeAssert(fn, emitConv(fn, v, tEface), tEface, token.NoPos)
+					}
+				} else {
+					// non-type param interface
+					// Emit nil check: typeassert v.(I).
+					emitTypeAssert(fn, v, rt, e.Sel.Pos())
+				}
+			}
+			if targs := receiverTypeArgs(obj); len(targs) > 0 {
+				// obj is generic.
+				obj = fn.Prog.canon.instantiateMethod(obj, fn.subst.types(targs), fn.Prog.ctxt)
+			}
+			bound := createBound(fn.Prog, obj)
+			b.enqueue(bound)
+
+			c := &MakeClosure{
+				Fn:       bound,
+				Bindings: []Value{v},
+			}
+			c.setPos(e.Sel.Pos())
+			c.setType(fn.typ(tv.Type))
+			return fn.emit(c)
+
+		case types.FieldVal:
+			indices := sel.index
+			last := len(indices) - 1
+			v := b.expr(fn, e.X)
+			v = emitImplicitSelections(fn, v, indices[:last], e.Pos())
+			v = emitFieldSelection(fn, v, indices[last], false, e.Sel)
+			return v
+		}
+
+		panic("unexpected expression-relative selector")
+
+	case *ast.IndexListExpr:
+		// f[X, Y] must be a generic function
+		if !instance(fn.info, e.X) {
+			panic("unexpected expression-could not match index list to instantiation")
+		}
+		return b.expr(fn, e.X) // Handle instantiation within the *Ident or *SelectorExpr cases.
+
+	case *ast.IndexExpr:
+		if instance(fn.info, e.X) {
+			return b.expr(fn, e.X) // Handle instantiation within the *Ident or *SelectorExpr cases.
+		}
+		// not a generic instantiation.
+		xt := fn.typeOf(e.X)
+		switch et, mode := indexType(xt); mode {
+		case ixVar:
+			// Addressable slice/array; use IndexAddr and Load.
+			return b.addr(fn, e, false).load(fn)
+
+		case ixArrVar, ixValue:
+			// An array in a register, a string or a combined type that contains
+			// either an [_]array (ixArrVar) or string (ixValue).
+
+			// Note: for ixArrVar and CoreType(xt)==nil can be IndexAddr and Load.
+			index := b.expr(fn, e.Index)
+			if isUntyped(index.Type()) {
+				index = emitConv(fn, index, tInt)
+			}
+			v := &Index{
+				X:     b.expr(fn, e.X),
+				Index: index,
+			}
+			v.setPos(e.Lbrack)
+			v.setType(et)
+			return fn.emit(v)
+
+		case ixMap:
+			ct := typeparams.CoreType(xt).(*types.Map)
+			v := &Lookup{
+				X:     b.expr(fn, e.X),
+				Index: emitConv(fn, b.expr(fn, e.Index), ct.Key()),
+			}
+			v.setPos(e.Lbrack)
+			v.setType(ct.Elem())
+			return fn.emit(v)
+		default:
+			panic("unexpected container type in IndexExpr: " + xt.String())
+		}
+
+	case *ast.CompositeLit, *ast.StarExpr:
+		// Addressable types (lvalues)
+		return b.addr(fn, e, false).load(fn)
+	}
+
+	panic(fmt.Sprintf("unexpected expr: %T", e))
+}
+
+// stmtList emits to fn code for all statements in list.
+func (b *builder) stmtList(fn *Function, list []ast.Stmt) {
+	for _, s := range list {
+		b.stmt(fn, s)
+	}
+}
+
+// receiver emits to fn code for expression e in the "receiver"
+// position of selection e.f (where f may be a field or a method) and
+// returns the effective receiver after applying the implicit field
+// selections of sel.
+//
+// wantAddr requests that the result is an address.  If
+// !sel.indirect, this may require that e be built in addr() mode; it
+// must thus be addressable.
+//
+// escaping is defined as per builder.addr().
+func (b *builder) receiver(fn *Function, e ast.Expr, wantAddr, escaping bool, sel *selection) Value {
+	var v Value
+	if wantAddr && !sel.indirect && !isPointerCore(fn.typeOf(e)) {
+		v = b.addr(fn, e, escaping).address(fn)
+	} else {
+		v = b.expr(fn, e)
+	}
+
+	last := len(sel.index) - 1
+	// The position of implicit selection is the position of the inducing receiver expression.
+	v = emitImplicitSelections(fn, v, sel.index[:last], e.Pos())
+	if types.IsInterface(v.Type()) {
+		// When v is an interface, sel.Kind()==MethodValue and v.f is invoked.
+		// So v is not loaded, even if v has a pointer core type.
+	} else if !wantAddr && isPointerCore(v.Type()) {
+		v = emitLoad(fn, v)
+	}
+	return v
+}
+
+// setCallFunc populates the function parts of a CallCommon structure
+// (Func, Method, Recv, Args[0]) based on the kind of invocation
+// occurring in e.
+func (b *builder) setCallFunc(fn *Function, e *ast.CallExpr, c *CallCommon) {
+	c.pos = e.Lparen
+
+	// Is this a method call?
+	if selector, ok := unparen(e.Fun).(*ast.SelectorExpr); ok {
+		sel := fn.selection(selector)
+		if sel != nil && sel.kind == types.MethodVal {
+			obj := sel.obj.(*types.Func)
+			recv := recvType(obj)
+
+			wantAddr := isPointer(recv)
+			escaping := true
+			v := b.receiver(fn, selector.X, wantAddr, escaping, sel)
+			if types.IsInterface(recv) {
+				// Invoke-mode call.
+				c.Value = v // possibly type param
+				c.Method = obj
+			} else {
+				// "Call"-mode call.
+				c.Value = fn.Prog.objectMethod(obj, b)
+				c.Args = append(c.Args, v)
+			}
+			return
+		}
+
+		// sel.kind==MethodExpr indicates T.f() or (*T).f():
+		// a statically dispatched call to the method f in the
+		// method-set of T or *T.  T may be an interface.
+		//
+		// e.Fun would evaluate to a concrete method, interface
+		// wrapper function, or promotion wrapper.
+		//
+		// For now, we evaluate it in the usual way.
+		//
+		// TODO(adonovan): opt: inline expr() here, to make the
+		// call static and to avoid generation of wrappers.
+		// It's somewhat tricky as it may consume the first
+		// actual parameter if the call is "invoke" mode.
+		//
+		// Examples:
+		//  type T struct{}; func (T) f() {}   // "call" mode
+		//  type T interface { f() }           // "invoke" mode
+		//
+		//  type S struct{ T }
+		//
+		//  var s S
+		//  S.f(s)
+		//  (*S).f(&s)
+		//
+		// Suggested approach:
+		// - consume the first actual parameter expression
+		//   and build it with b.expr().
+		// - apply implicit field selections.
+		// - use MethodVal logic to populate fields of c.
+	}
+
+	// Evaluate the function operand in the usual way.
+	c.Value = b.expr(fn, e.Fun)
+}
+
+// emitCallArgs emits to f code for the actual parameters of call e to
+// a (possibly built-in) function of effective type sig.
+// The argument values are appended to args, which is then returned.
+func (b *builder) emitCallArgs(fn *Function, sig *types.Signature, e *ast.CallExpr, args []Value) []Value {
+	// f(x, y, z...): pass slice z straight through.
+	if e.Ellipsis != 0 {
+		for i, arg := range e.Args {
+			v := emitConv(fn, b.expr(fn, arg), sig.Params().At(i).Type())
+			args = append(args, v)
+		}
+		return args
+	}
+
+	offset := len(args) // 1 if call has receiver, 0 otherwise
+
+	// Evaluate actual parameter expressions.
+	//
+	// If this is a chained call of the form f(g()) where g has
+	// multiple return values (MRV), they are flattened out into
+	// args; a suffix of them may end up in a varargs slice.
+	for _, arg := range e.Args {
+		v := b.expr(fn, arg)
+		if ttuple, ok := v.Type().(*types.Tuple); ok { // MRV chain
+			for i, n := 0, ttuple.Len(); i < n; i++ {
+				args = append(args, emitExtract(fn, v, i))
+			}
+		} else {
+			args = append(args, v)
+		}
+	}
+
+	// Actual->formal assignability conversions for normal parameters.
+	np := sig.Params().Len() // number of normal parameters
+	if sig.Variadic() {
+		np--
+	}
+	for i := 0; i < np; i++ {
+		args[offset+i] = emitConv(fn, args[offset+i], sig.Params().At(i).Type())
+	}
+
+	// Actual->formal assignability conversions for variadic parameter,
+	// and construction of slice.
+	if sig.Variadic() {
+		varargs := args[offset+np:]
+		st := sig.Params().At(np).Type().(*types.Slice)
+		vt := st.Elem()
+		if len(varargs) == 0 {
+			args = append(args, zeroConst(st))
+		} else {
+			// Replace a suffix of args with a slice containing it.
+			at := types.NewArray(vt, int64(len(varargs)))
+			a := emitNew(fn, at, token.NoPos, "varargs")
+			a.setPos(e.Rparen)
+			for i, arg := range varargs {
+				iaddr := &IndexAddr{
+					X:     a,
+					Index: intConst(int64(i)),
+				}
+				iaddr.setType(types.NewPointer(vt))
+				fn.emit(iaddr)
+				emitStore(fn, iaddr, arg, arg.Pos())
+			}
+			s := &Slice{X: a}
+			s.setType(st)
+			args[offset+np] = fn.emit(s)
+			args = args[:offset+np+1]
+		}
+	}
+	return args
+}
+
+// setCall emits to fn code to evaluate all the parameters of a function
+// call e, and populates *c with those values.
+func (b *builder) setCall(fn *Function, e *ast.CallExpr, c *CallCommon) {
+	// First deal with the f(...) part and optional receiver.
+	b.setCallFunc(fn, e, c)
+
+	// Then append the other actual parameters.
+	sig, _ := typeparams.CoreType(fn.typeOf(e.Fun)).(*types.Signature)
+	if sig == nil {
+		panic(fmt.Sprintf("no signature for call of %s", e.Fun))
+	}
+	c.Args = b.emitCallArgs(fn, sig, e, c.Args)
+}
+
+// assignOp emits to fn code to perform loc <op>= val.
+func (b *builder) assignOp(fn *Function, loc lvalue, val Value, op token.Token, pos token.Pos) {
+	loc.store(fn, emitArith(fn, op, loc.load(fn), val, loc.typ(), pos))
+}
+
+// localValueSpec emits to fn code to define all of the vars in the
+// function-local ValueSpec, spec.
+func (b *builder) localValueSpec(fn *Function, spec *ast.ValueSpec) {
+	switch {
+	case len(spec.Values) == len(spec.Names):
+		// e.g. var x, y = 0, 1
+		// 1:1 assignment
+		for i, id := range spec.Names {
+			if !isBlankIdent(id) {
+				emitLocalVar(fn, identVar(fn, id))
+			}
+			lval := b.addr(fn, id, false) // non-escaping
+			b.assign(fn, lval, spec.Values[i], true, nil)
+		}
+
+	case len(spec.Values) == 0:
+		// e.g. var x, y int
+		// Locals are implicitly zero-initialized.
+		for _, id := range spec.Names {
+			if !isBlankIdent(id) {
+				lhs := emitLocalVar(fn, identVar(fn, id))
+				if fn.debugInfo() {
+					emitDebugRef(fn, id, lhs, true)
+				}
+			}
+		}
+
+	default:
+		// e.g. var x, y = pos()
+		tuple := b.exprN(fn, spec.Values[0])
+		for i, id := range spec.Names {
+			if !isBlankIdent(id) {
+				emitLocalVar(fn, identVar(fn, id))
+				lhs := b.addr(fn, id, false) // non-escaping
+				lhs.store(fn, emitExtract(fn, tuple, i))
+			}
+		}
+	}
+}
+
+// assignStmt emits code to fn for a parallel assignment of rhss to lhss.
+// isDef is true if this is a short variable declaration (:=).
+//
+// Note the similarity with localValueSpec.
+func (b *builder) assignStmt(fn *Function, lhss, rhss []ast.Expr, isDef bool) {
+	// Side effects of all LHSs and RHSs must occur in left-to-right order.
+	lvals := make([]lvalue, len(lhss))
+	isZero := make([]bool, len(lhss))
+	for i, lhs := range lhss {
+		var lval lvalue = blank{}
+		if !isBlankIdent(lhs) {
+			if isDef {
+				if obj, ok := fn.info.Defs[lhs.(*ast.Ident)].(*types.Var); ok {
+					emitLocalVar(fn, obj)
+					isZero[i] = true
+				}
+			}
+			lval = b.addr(fn, lhs, false) // non-escaping
+		}
+		lvals[i] = lval
+	}
+	if len(lhss) == len(rhss) {
+		// Simple assignment:   x     = f()        (!isDef)
+		// Parallel assignment: x, y  = f(), g()   (!isDef)
+		// or short var decl:   x, y := f(), g()   (isDef)
+		//
+		// In all cases, the RHSs may refer to the LHSs,
+		// so we need a storebuf.
+		var sb storebuf
+		for i := range rhss {
+			b.assign(fn, lvals[i], rhss[i], isZero[i], &sb)
+		}
+		sb.emit(fn)
+	} else {
+		// e.g. x, y = pos()
+		tuple := b.exprN(fn, rhss[0])
+		emitDebugRef(fn, rhss[0], tuple, false)
+		for i, lval := range lvals {
+			lval.store(fn, emitExtract(fn, tuple, i))
+		}
+	}
+}
+
+// arrayLen returns the length of the array whose composite literal elements are elts.
+func (b *builder) arrayLen(fn *Function, elts []ast.Expr) int64 {
+	var max int64 = -1
+	var i int64 = -1
+	for _, e := range elts {
+		if kv, ok := e.(*ast.KeyValueExpr); ok {
+			i = b.expr(fn, kv.Key).(*Const).Int64()
+		} else {
+			i++
+		}
+		if i > max {
+			max = i
+		}
+	}
+	return max + 1
+}
+
+// compLit emits to fn code to initialize a composite literal e at
+// address addr with type typ.
+//
+// Nested composite literals are recursively initialized in place
+// where possible. If isZero is true, compLit assumes that addr
+// holds the zero value for typ.
+//
+// Because the elements of a composite literal may refer to the
+// variables being updated, as in the second line below,
+//
+//	x := T{a: 1}
+//	x = T{a: x.a}
+//
+// all the reads must occur before all the writes.  Thus all stores to
+// loc are emitted to the storebuf sb for later execution.
+//
+// A CompositeLit may have pointer type only in the recursive (nested)
+// case when the type name is implicit.  e.g. in []*T{{}}, the inner
+// literal has type *T behaves like &T{}.
+// In that case, addr must hold a T, not a *T.
+func (b *builder) compLit(fn *Function, addr Value, e *ast.CompositeLit, isZero bool, sb *storebuf) {
+	typ := typeparams.Deref(fn.typeOf(e)) // retain the named/alias/param type, if any
+	switch t := typeparams.CoreType(typ).(type) {
+	case *types.Struct:
+		if !isZero && len(e.Elts) != t.NumFields() {
+			// memclear
+			zt := typeparams.MustDeref(addr.Type())
+			sb.store(&address{addr, e.Lbrace, nil}, zeroConst(zt))
+			isZero = true
+		}
+		for i, e := range e.Elts {
+			fieldIndex := i
+			pos := e.Pos()
+			if kv, ok := e.(*ast.KeyValueExpr); ok {
+				fname := kv.Key.(*ast.Ident).Name
+				for i, n := 0, t.NumFields(); i < n; i++ {
+					sf := t.Field(i)
+					if sf.Name() == fname {
+						fieldIndex = i
+						pos = kv.Colon
+						e = kv.Value
+						break
+					}
+				}
+			}
+			sf := t.Field(fieldIndex)
+			faddr := &FieldAddr{
+				X:     addr,
+				Field: fieldIndex,
+			}
+			faddr.setPos(pos)
+			faddr.setType(types.NewPointer(sf.Type()))
+			fn.emit(faddr)
+			b.assign(fn, &address{addr: faddr, pos: pos, expr: e}, e, isZero, sb)
+		}
+
+	case *types.Array, *types.Slice:
+		var at *types.Array
+		var array Value
+		switch t := t.(type) {
+		case *types.Slice:
+			at = types.NewArray(t.Elem(), b.arrayLen(fn, e.Elts))
+			array = emitNew(fn, at, e.Lbrace, "slicelit")
+		case *types.Array:
+			at = t
+			array = addr
+
+			if !isZero && int64(len(e.Elts)) != at.Len() {
+				// memclear
+				zt := typeparams.MustDeref(array.Type())
+				sb.store(&address{array, e.Lbrace, nil}, zeroConst(zt))
+			}
+		}
+
+		var idx *Const
+		for _, e := range e.Elts {
+			pos := e.Pos()
+			if kv, ok := e.(*ast.KeyValueExpr); ok {
+				idx = b.expr(fn, kv.Key).(*Const)
+				pos = kv.Colon
+				e = kv.Value
+			} else {
+				var idxval int64
+				if idx != nil {
+					idxval = idx.Int64() + 1
+				}
+				idx = intConst(idxval)
+			}
+			iaddr := &IndexAddr{
+				X:     array,
+				Index: idx,
+			}
+			iaddr.setType(types.NewPointer(at.Elem()))
+			fn.emit(iaddr)
+			if t != at { // slice
+				// backing array is unaliased => storebuf not needed.
+				b.assign(fn, &address{addr: iaddr, pos: pos, expr: e}, e, true, nil)
+			} else {
+				b.assign(fn, &address{addr: iaddr, pos: pos, expr: e}, e, true, sb)
+			}
+		}
+
+		if t != at { // slice
+			s := &Slice{X: array}
+			s.setPos(e.Lbrace)
+			s.setType(typ)
+			sb.store(&address{addr: addr, pos: e.Lbrace, expr: e}, fn.emit(s))
+		}
+
+	case *types.Map:
+		m := &MakeMap{Reserve: intConst(int64(len(e.Elts)))}
+		m.setPos(e.Lbrace)
+		m.setType(typ)
+		fn.emit(m)
+		for _, e := range e.Elts {
+			e := e.(*ast.KeyValueExpr)
+
+			// If a key expression in a map literal is itself a
+			// composite literal, the type may be omitted.
+			// For example:
+			//	map[*struct{}]bool{{}: true}
+			// An &-operation may be implied:
+			//	map[*struct{}]bool{&struct{}{}: true}
+			wantAddr := false
+			if _, ok := unparen(e.Key).(*ast.CompositeLit); ok {
+				wantAddr = isPointerCore(t.Key())
+			}
+
+			var key Value
+			if wantAddr {
+				// A CompositeLit never evaluates to a pointer,
+				// so if the type of the location is a pointer,
+				// an &-operation is implied.
+				key = b.addr(fn, e.Key, true).address(fn)
+			} else {
+				key = b.expr(fn, e.Key)
+			}
+
+			loc := element{
+				m:   m,
+				k:   emitConv(fn, key, t.Key()),
+				t:   t.Elem(),
+				pos: e.Colon,
+			}
+
+			// We call assign() only because it takes care
+			// of any &-operation required in the recursive
+			// case, e.g.,
+			// map[int]*struct{}{0: {}} implies &struct{}{}.
+			// In-place update is of course impossible,
+			// and no storebuf is needed.
+			b.assign(fn, &loc, e.Value, true, nil)
+		}
+		sb.store(&address{addr: addr, pos: e.Lbrace, expr: e}, m)
+
+	default:
+		panic("unexpected CompositeLit type: " + typ.String())
+	}
+}
+
+// switchStmt emits to fn code for the switch statement s, optionally
+// labelled by label.
+func (b *builder) switchStmt(fn *Function, s *ast.SwitchStmt, label *lblock) {
+	// We treat SwitchStmt like a sequential if-else chain.
+	// Multiway dispatch can be recovered later by ssautil.Switches()
+	// to those cases that are free of side effects.
+	if s.Init != nil {
+		b.stmt(fn, s.Init)
+	}
+	var tag Value = vTrue
+	if s.Tag != nil {
+		tag = b.expr(fn, s.Tag)
+	}
+	done := fn.newBasicBlock("switch.done")
+	if label != nil {
+		label._break = done
+	}
+	// We pull the default case (if present) down to the end.
+	// But each fallthrough label must point to the next
+	// body block in source order, so we preallocate a
+	// body block (fallthru) for the next case.
+	// Unfortunately this makes for a confusing block order.
+	var dfltBody *[]ast.Stmt
+	var dfltFallthrough *BasicBlock
+	var fallthru, dfltBlock *BasicBlock
+	ncases := len(s.Body.List)
+	for i, clause := range s.Body.List {
+		body := fallthru
+		if body == nil {
+			body = fn.newBasicBlock("switch.body") // first case only
+		}
+
+		// Preallocate body block for the next case.
+		fallthru = done
+		if i+1 < ncases {
+			fallthru = fn.newBasicBlock("switch.body")
+		}
+
+		cc := clause.(*ast.CaseClause)
+		if cc.List == nil {
+			// Default case.
+			dfltBody = &cc.Body
+			dfltFallthrough = fallthru
+			dfltBlock = body
+			continue
+		}
+
+		var nextCond *BasicBlock
+		for _, cond := range cc.List {
+			nextCond = fn.newBasicBlock("switch.next")
+			// TODO(adonovan): opt: when tag==vTrue, we'd
+			// get better code if we use b.cond(cond)
+			// instead of BinOp(EQL, tag, b.expr(cond))
+			// followed by If.  Don't forget conversions
+			// though.
+			cond := emitCompare(fn, token.EQL, tag, b.expr(fn, cond), cond.Pos())
+			emitIf(fn, cond, body, nextCond)
+			fn.currentBlock = nextCond
+		}
+		fn.currentBlock = body
+		fn.targets = &targets{
+			tail:         fn.targets,
+			_break:       done,
+			_fallthrough: fallthru,
+		}
+		b.stmtList(fn, cc.Body)
+		fn.targets = fn.targets.tail
+		emitJump(fn, done)
+		fn.currentBlock = nextCond
+	}
+	if dfltBlock != nil {
+		emitJump(fn, dfltBlock)
+		fn.currentBlock = dfltBlock
+		fn.targets = &targets{
+			tail:         fn.targets,
+			_break:       done,
+			_fallthrough: dfltFallthrough,
+		}
+		b.stmtList(fn, *dfltBody)
+		fn.targets = fn.targets.tail
+	}
+	emitJump(fn, done)
+	fn.currentBlock = done
+}
+
+// typeSwitchStmt emits to fn code for the type switch statement s, optionally
+// labelled by label.
+func (b *builder) typeSwitchStmt(fn *Function, s *ast.TypeSwitchStmt, label *lblock) {
+	// We treat TypeSwitchStmt like a sequential if-else chain.
+	// Multiway dispatch can be recovered later by ssautil.Switches().
+
+	// Typeswitch lowering:
+	//
+	// var x X
+	// switch y := x.(type) {
+	// case T1, T2: S1                  // >1 	(y := x)
+	// case nil:    SN                  // nil 	(y := x)
+	// default:     SD                  // 0 types 	(y := x)
+	// case T3:     S3                  // 1 type 	(y := x.(T3))
+	// }
+	//
+	//      ...s.Init...
+	// 	x := eval x
+	// .caseT1:
+	// 	t1, ok1 := typeswitch,ok x <T1>
+	// 	if ok1 then goto S1 else goto .caseT2
+	// .caseT2:
+	// 	t2, ok2 := typeswitch,ok x <T2>
+	// 	if ok2 then goto S1 else goto .caseNil
+	// .S1:
+	//      y := x
+	// 	...S1...
+	// 	goto done
+	// .caseNil:
+	// 	if t2, ok2 := typeswitch,ok x <T2>
+	// 	if x == nil then goto SN else goto .caseT3
+	// .SN:
+	//      y := x
+	// 	...SN...
+	// 	goto done
+	// .caseT3:
+	// 	t3, ok3 := typeswitch,ok x <T3>
+	// 	if ok3 then goto S3 else goto default
+	// .S3:
+	//      y := t3
+	// 	...S3...
+	// 	goto done
+	// .default:
+	//      y := x
+	// 	...SD...
+	// 	goto done
+	// .done:
+	if s.Init != nil {
+		b.stmt(fn, s.Init)
+	}
+
+	var x Value
+	switch ass := s.Assign.(type) {
+	case *ast.ExprStmt: // x.(type)
+		x = b.expr(fn, unparen(ass.X).(*ast.TypeAssertExpr).X)
+	case *ast.AssignStmt: // y := x.(type)
+		x = b.expr(fn, unparen(ass.Rhs[0]).(*ast.TypeAssertExpr).X)
+	}
+
+	done := fn.newBasicBlock("typeswitch.done")
+	if label != nil {
+		label._break = done
+	}
+	var default_ *ast.CaseClause
+	for _, clause := range s.Body.List {
+		cc := clause.(*ast.CaseClause)
+		if cc.List == nil {
+			default_ = cc
+			continue
+		}
+		body := fn.newBasicBlock("typeswitch.body")
+		var next *BasicBlock
+		var casetype types.Type
+		var ti Value // ti, ok := typeassert,ok x <Ti>
+		for _, cond := range cc.List {
+			next = fn.newBasicBlock("typeswitch.next")
+			casetype = fn.typeOf(cond)
+			var condv Value
+			if casetype == tUntypedNil {
+				condv = emitCompare(fn, token.EQL, x, zeroConst(x.Type()), cond.Pos())
+				ti = x
+			} else {
+				yok := emitTypeTest(fn, x, casetype, cc.Case)
+				ti = emitExtract(fn, yok, 0)
+				condv = emitExtract(fn, yok, 1)
+			}
+			emitIf(fn, condv, body, next)
+			fn.currentBlock = next
+		}
+		if len(cc.List) != 1 {
+			ti = x
+		}
+		fn.currentBlock = body
+		b.typeCaseBody(fn, cc, ti, done)
+		fn.currentBlock = next
+	}
+	if default_ != nil {
+		b.typeCaseBody(fn, default_, x, done)
+	} else {
+		emitJump(fn, done)
+	}
+	fn.currentBlock = done
+}
+
+func (b *builder) typeCaseBody(fn *Function, cc *ast.CaseClause, x Value, done *BasicBlock) {
+	if obj, ok := fn.info.Implicits[cc].(*types.Var); ok {
+		// In a switch y := x.(type), each case clause
+		// implicitly declares a distinct object y.
+		// In a single-type case, y has that type.
+		// In multi-type cases, 'case nil' and default,
+		// y has the same type as the interface operand.
+		emitStore(fn, emitLocalVar(fn, obj), x, obj.Pos())
+	}
+	fn.targets = &targets{
+		tail:   fn.targets,
+		_break: done,
+	}
+	b.stmtList(fn, cc.Body)
+	fn.targets = fn.targets.tail
+	emitJump(fn, done)
+}
+
+// selectStmt emits to fn code for the select statement s, optionally
+// labelled by label.
+func (b *builder) selectStmt(fn *Function, s *ast.SelectStmt, label *lblock) {
+	// A blocking select of a single case degenerates to a
+	// simple send or receive.
+	// TODO(adonovan): opt: is this optimization worth its weight?
+	if len(s.Body.List) == 1 {
+		clause := s.Body.List[0].(*ast.CommClause)
+		if clause.Comm != nil {
+			b.stmt(fn, clause.Comm)
+			done := fn.newBasicBlock("select.done")
+			if label != nil {
+				label._break = done
+			}
+			fn.targets = &targets{
+				tail:   fn.targets,
+				_break: done,
+			}
+			b.stmtList(fn, clause.Body)
+			fn.targets = fn.targets.tail
+			emitJump(fn, done)
+			fn.currentBlock = done
+			return
+		}
+	}
+
+	// First evaluate all channels in all cases, and find
+	// the directions of each state.
+	var states []*SelectState
+	blocking := true
+	debugInfo := fn.debugInfo()
+	for _, clause := range s.Body.List {
+		var st *SelectState
+		switch comm := clause.(*ast.CommClause).Comm.(type) {
+		case nil: // default case
+			blocking = false
+			continue
+
+		case *ast.SendStmt: // ch<- i
+			ch := b.expr(fn, comm.Chan)
+			chtyp := typeparams.CoreType(fn.typ(ch.Type())).(*types.Chan)
+			st = &SelectState{
+				Dir:  types.SendOnly,
+				Chan: ch,
+				Send: emitConv(fn, b.expr(fn, comm.Value), chtyp.Elem()),
+				Pos:  comm.Arrow,
+			}
+			if debugInfo {
+				st.DebugNode = comm
+			}
+
+		case *ast.AssignStmt: // x := <-ch
+			recv := unparen(comm.Rhs[0]).(*ast.UnaryExpr)
+			st = &SelectState{
+				Dir:  types.RecvOnly,
+				Chan: b.expr(fn, recv.X),
+				Pos:  recv.OpPos,
+			}
+			if debugInfo {
+				st.DebugNode = recv
+			}
+
+		case *ast.ExprStmt: // <-ch
+			recv := unparen(comm.X).(*ast.UnaryExpr)
+			st = &SelectState{
+				Dir:  types.RecvOnly,
+				Chan: b.expr(fn, recv.X),
+				Pos:  recv.OpPos,
+			}
+			if debugInfo {
+				st.DebugNode = recv
+			}
+		}
+		states = append(states, st)
+	}
+
+	// We dispatch on the (fair) result of Select using a
+	// sequential if-else chain, in effect:
+	//
+	// idx, recvOk, r0...r_n-1 := select(...)
+	// if idx == 0 {  // receive on channel 0  (first receive => r0)
+	//     x, ok := r0, recvOk
+	//     ...state0...
+	// } else if v == 1 {   // send on channel 1
+	//     ...state1...
+	// } else {
+	//     ...default...
+	// }
+	sel := &Select{
+		States:   states,
+		Blocking: blocking,
+	}
+	sel.setPos(s.Select)
+	var vars []*types.Var
+	vars = append(vars, varIndex, varOk)
+	for _, st := range states {
+		if st.Dir == types.RecvOnly {
+			chtyp := typeparams.CoreType(fn.typ(st.Chan.Type())).(*types.Chan)
+			vars = append(vars, anonVar(chtyp.Elem()))
+		}
+	}
+	sel.setType(types.NewTuple(vars...))
+
+	fn.emit(sel)
+	idx := emitExtract(fn, sel, 0)
+
+	done := fn.newBasicBlock("select.done")
+	if label != nil {
+		label._break = done
+	}
+
+	var defaultBody *[]ast.Stmt
+	state := 0
+	r := 2 // index in 'sel' tuple of value; increments if st.Dir==RECV
+	for _, cc := range s.Body.List {
+		clause := cc.(*ast.CommClause)
+		if clause.Comm == nil {
+			defaultBody = &clause.Body
+			continue
+		}
+		body := fn.newBasicBlock("select.body")
+		next := fn.newBasicBlock("select.next")
+		emitIf(fn, emitCompare(fn, token.EQL, idx, intConst(int64(state)), token.NoPos), body, next)
+		fn.currentBlock = body
+		fn.targets = &targets{
+			tail:   fn.targets,
+			_break: done,
+		}
+		switch comm := clause.Comm.(type) {
+		case *ast.ExprStmt: // <-ch
+			if debugInfo {
+				v := emitExtract(fn, sel, r)
+				emitDebugRef(fn, states[state].DebugNode.(ast.Expr), v, false)
+			}
+			r++
+
+		case *ast.AssignStmt: // x := <-states[state].Chan
+			if comm.Tok == token.DEFINE {
+				emitLocalVar(fn, identVar(fn, comm.Lhs[0].(*ast.Ident)))
+			}
+			x := b.addr(fn, comm.Lhs[0], false) // non-escaping
+			v := emitExtract(fn, sel, r)
+			if debugInfo {
+				emitDebugRef(fn, states[state].DebugNode.(ast.Expr), v, false)
+			}
+			x.store(fn, v)
+
+			if len(comm.Lhs) == 2 { // x, ok := ...
+				if comm.Tok == token.DEFINE {
+					emitLocalVar(fn, identVar(fn, comm.Lhs[1].(*ast.Ident)))
+				}
+				ok := b.addr(fn, comm.Lhs[1], false) // non-escaping
+				ok.store(fn, emitExtract(fn, sel, 1))
+			}
+			r++
+		}
+		b.stmtList(fn, clause.Body)
+		fn.targets = fn.targets.tail
+		emitJump(fn, done)
+		fn.currentBlock = next
+		state++
+	}
+	if defaultBody != nil {
+		fn.targets = &targets{
+			tail:   fn.targets,
+			_break: done,
+		}
+		b.stmtList(fn, *defaultBody)
+		fn.targets = fn.targets.tail
+	} else {
+		// A blocking select must match some case.
+		// (This should really be a runtime.errorString, not a string.)
+		fn.emit(&Panic{
+			X: emitConv(fn, stringConst("blocking select matched no case"), tEface),
+		})
+		fn.currentBlock = fn.newBasicBlock("unreachable")
+	}
+	emitJump(fn, done)
+	fn.currentBlock = done
+}
+
+// forStmt emits to fn code for the for statement s, optionally
+// labelled by label.
+func (b *builder) forStmt(fn *Function, s *ast.ForStmt, label *lblock) {
+	// Use forStmtGo122 instead if it applies.
+	if s.Init != nil {
+		if assign, ok := s.Init.(*ast.AssignStmt); ok && assign.Tok == token.DEFINE {
+			if versions.AtLeast(fn.goversion, versions.Go1_22) {
+				b.forStmtGo122(fn, s, label)
+				return
+			}
+		}
+	}
+
+	//     ...init...
+	//     jump loop
+	// loop:
+	//     if cond goto body else done
+	// body:
+	//     ...body...
+	//     jump post
+	// post:                                 (target of continue)
+	//     ...post...
+	//     jump loop
+	// done:                                 (target of break)
+	if s.Init != nil {
+		b.stmt(fn, s.Init)
+	}
+
+	body := fn.newBasicBlock("for.body")
+	done := fn.newBasicBlock("for.done") // target of 'break'
+	loop := body                         // target of back-edge
+	if s.Cond != nil {
+		loop = fn.newBasicBlock("for.loop")
+	}
+	cont := loop // target of 'continue'
+	if s.Post != nil {
+		cont = fn.newBasicBlock("for.post")
+	}
+	if label != nil {
+		label._break = done
+		label._continue = cont
+	}
+	emitJump(fn, loop)
+	fn.currentBlock = loop
+	if loop != body {
+		b.cond(fn, s.Cond, body, done)
+		fn.currentBlock = body
+	}
+	fn.targets = &targets{
+		tail:      fn.targets,
+		_break:    done,
+		_continue: cont,
+	}
+	b.stmt(fn, s.Body)
+	fn.targets = fn.targets.tail
+	emitJump(fn, cont)
+
+	if s.Post != nil {
+		fn.currentBlock = cont
+		b.stmt(fn, s.Post)
+		emitJump(fn, loop) // back-edge
+	}
+	fn.currentBlock = done
+}
+
+// forStmtGo122 emits to fn code for the for statement s, optionally
+// labelled by label. s must define its variables.
+//
+// This allocates once per loop iteration. This is only correct in
+// GoVersions >= go1.22.
+func (b *builder) forStmtGo122(fn *Function, s *ast.ForStmt, label *lblock) {
+	//     i_outer = alloc[T]
+	//     *i_outer = ...init...        // under objects[i] = i_outer
+	//     jump loop
+	// loop:
+	//     i = phi [head: i_outer, loop: i_next]
+	//     ...cond...                   // under objects[i] = i
+	//     if cond goto body else done
+	// body:
+	//     ...body...                   // under objects[i] = i (same as loop)
+	//     jump post
+	// post:
+	//     tmp = *i
+	//     i_next = alloc[T]
+	//     *i_next = tmp
+	//     ...post...                   // under objects[i] = i_next
+	//     goto loop
+	// done:
+
+	init := s.Init.(*ast.AssignStmt)
+	startingBlocks := len(fn.Blocks)
+
+	pre := fn.currentBlock               // current block before starting
+	loop := fn.newBasicBlock("for.loop") // target of back-edge
+	body := fn.newBasicBlock("for.body")
+	post := fn.newBasicBlock("for.post") // target of 'continue'
+	done := fn.newBasicBlock("for.done") // target of 'break'
+
+	// For each of the n loop variables, we create five SSA values,
+	// outer, phi, next, load, and store in pre, loop, and post.
+	// There is no limit on n.
+	type loopVar struct {
+		obj   *types.Var
+		outer *Alloc
+		phi   *Phi
+		load  *UnOp
+		next  *Alloc
+		store *Store
+	}
+	vars := make([]loopVar, len(init.Lhs))
+	for i, lhs := range init.Lhs {
+		v := identVar(fn, lhs.(*ast.Ident))
+		typ := fn.typ(v.Type())
+
+		fn.currentBlock = pre
+		outer := emitLocal(fn, typ, v.Pos(), v.Name())
+
+		fn.currentBlock = loop
+		phi := &Phi{Comment: v.Name()}
+		phi.pos = v.Pos()
+		phi.typ = outer.Type()
+		fn.emit(phi)
+
+		fn.currentBlock = post
+		// If next is local, it reuses the address and zeroes the old value so
+		// load before allocating next.
+		load := emitLoad(fn, phi)
+		next := emitLocal(fn, typ, v.Pos(), v.Name())
+		store := emitStore(fn, next, load, token.NoPos)
+
+		phi.Edges = []Value{outer, next} // pre edge is emitted before post edge.
+
+		vars[i] = loopVar{v, outer, phi, load, next, store}
+	}
+
+	// ...init... under fn.objects[v] = i_outer
+	fn.currentBlock = pre
+	for _, v := range vars {
+		fn.vars[v.obj] = v.outer
+	}
+	const isDef = false // assign to already-allocated outers
+	b.assignStmt(fn, init.Lhs, init.Rhs, isDef)
+	if label != nil {
+		label._break = done
+		label._continue = post
+	}
+	emitJump(fn, loop)
+
+	// ...cond... under fn.objects[v] = i
+	fn.currentBlock = loop
+	for _, v := range vars {
+		fn.vars[v.obj] = v.phi
+	}
+	if s.Cond != nil {
+		b.cond(fn, s.Cond, body, done)
+	} else {
+		emitJump(fn, body)
+	}
+
+	// ...body... under fn.objects[v] = i
+	fn.currentBlock = body
+	fn.targets = &targets{
+		tail:      fn.targets,
+		_break:    done,
+		_continue: post,
+	}
+	b.stmt(fn, s.Body)
+	fn.targets = fn.targets.tail
+	emitJump(fn, post)
+
+	// ...post... under fn.objects[v] = i_next
+	for _, v := range vars {
+		fn.vars[v.obj] = v.next
+	}
+	fn.currentBlock = post
+	if s.Post != nil {
+		b.stmt(fn, s.Post)
+	}
+	emitJump(fn, loop) // back-edge
+	fn.currentBlock = done
+
+	// For each loop variable that does not escape,
+	// (the common case), fuse its next cells into its
+	// (local) outer cell as they have disjoint live ranges.
+	//
+	// It is sufficient to test whether i_next escapes,
+	// because its Heap flag will be marked true if either
+	// the cond or post expression causes i to escape
+	// (because escape distributes over phi).
+	var nlocals int
+	for _, v := range vars {
+		if !v.next.Heap {
+			nlocals++
+		}
+	}
+	if nlocals > 0 {
+		replace := make(map[Value]Value, 2*nlocals)
+		dead := make(map[Instruction]bool, 4*nlocals)
+		for _, v := range vars {
+			if !v.next.Heap {
+				replace[v.next] = v.outer
+				replace[v.phi] = v.outer
+				dead[v.phi], dead[v.next], dead[v.load], dead[v.store] = true, true, true, true
+			}
+		}
+
+		// Replace all uses of i_next and phi with i_outer.
+		// Referrers have not been built for fn yet so only update Instruction operands.
+		// We need only look within the blocks added by the loop.
+		var operands []*Value // recycle storage
+		for _, b := range fn.Blocks[startingBlocks:] {
+			for _, instr := range b.Instrs {
+				operands = instr.Operands(operands[:0])
+				for _, ptr := range operands {
+					k := *ptr
+					if v := replace[k]; v != nil {
+						*ptr = v
+					}
+				}
+			}
+		}
+
+		// Remove instructions for phi, load, and store.
+		// lift() will remove the unused i_next *Alloc.
+		isDead := func(i Instruction) bool { return dead[i] }
+		loop.Instrs = removeInstrsIf(loop.Instrs, isDead)
+		post.Instrs = removeInstrsIf(post.Instrs, isDead)
+	}
+}
+
+// rangeIndexed emits to fn the header for an integer-indexed loop
+// over array, *array or slice value x.
+// The v result is defined only if tv is non-nil.
+// forPos is the position of the "for" token.
+func (b *builder) rangeIndexed(fn *Function, x Value, tv types.Type, pos token.Pos) (k, v Value, loop, done *BasicBlock) {
+	//
+	//     length = len(x)
+	//     index = -1
+	// loop:                                     (target of continue)
+	//     index++
+	//     if index < length goto body else done
+	// body:
+	//     k = index
+	//     v = x[index]
+	//     ...body...
+	//     jump loop
+	// done:                                     (target of break)
+
+	// Determine number of iterations.
+	var length Value
+	dt := typeparams.Deref(x.Type())
+	if arr, ok := typeparams.CoreType(dt).(*types.Array); ok {
+		// For array or *array, the number of iterations is
+		// known statically thanks to the type.  We avoid a
+		// data dependence upon x, permitting later dead-code
+		// elimination if x is pure, static unrolling, etc.
+		// Ranging over a nil *array may have >0 iterations.
+		// We still generate code for x, in case it has effects.
+		length = intConst(arr.Len())
+	} else {
+		// length = len(x).
+		var c Call
+		c.Call.Value = makeLen(x.Type())
+		c.Call.Args = []Value{x}
+		c.setType(tInt)
+		length = fn.emit(&c)
+	}
+
+	index := emitLocal(fn, tInt, token.NoPos, "rangeindex")
+	emitStore(fn, index, intConst(-1), pos)
+
+	loop = fn.newBasicBlock("rangeindex.loop")
+	emitJump(fn, loop)
+	fn.currentBlock = loop
+
+	incr := &BinOp{
+		Op: token.ADD,
+		X:  emitLoad(fn, index),
+		Y:  vOne,
+	}
+	incr.setType(tInt)
+	emitStore(fn, index, fn.emit(incr), pos)
+
+	body := fn.newBasicBlock("rangeindex.body")
+	done = fn.newBasicBlock("rangeindex.done")
+	emitIf(fn, emitCompare(fn, token.LSS, incr, length, token.NoPos), body, done)
+	fn.currentBlock = body
+
+	k = emitLoad(fn, index)
+	if tv != nil {
+		switch t := typeparams.CoreType(x.Type()).(type) {
+		case *types.Array:
+			instr := &Index{
+				X:     x,
+				Index: k,
+			}
+			instr.setType(t.Elem())
+			instr.setPos(x.Pos())
+			v = fn.emit(instr)
+
+		case *types.Pointer: // *array
+			instr := &IndexAddr{
+				X:     x,
+				Index: k,
+			}
+			instr.setType(types.NewPointer(t.Elem().Underlying().(*types.Array).Elem()))
+			instr.setPos(x.Pos())
+			v = emitLoad(fn, fn.emit(instr))
+
+		case *types.Slice:
+			instr := &IndexAddr{
+				X:     x,
+				Index: k,
+			}
+			instr.setType(types.NewPointer(t.Elem()))
+			instr.setPos(x.Pos())
+			v = emitLoad(fn, fn.emit(instr))
+
+		default:
+			panic("rangeIndexed x:" + t.String())
+		}
+	}
+	return
+}
+
+// rangeIter emits to fn the header for a loop using
+// Range/Next/Extract to iterate over map or string value x.
+// tk and tv are the types of the key/value results k and v, or nil
+// if the respective component is not wanted.
+func (b *builder) rangeIter(fn *Function, x Value, tk, tv types.Type, pos token.Pos) (k, v Value, loop, done *BasicBlock) {
+	//
+	//     it = range x
+	// loop:                                   (target of continue)
+	//     okv = next it                       (ok, key, value)
+	//     ok = extract okv #0
+	//     if ok goto body else done
+	// body:
+	//     k = extract okv #1
+	//     v = extract okv #2
+	//     ...body...
+	//     jump loop
+	// done:                                   (target of break)
+	//
+
+	if tk == nil {
+		tk = tInvalid
+	}
+	if tv == nil {
+		tv = tInvalid
+	}
+
+	rng := &Range{X: x}
+	rng.setPos(pos)
+	rng.setType(tRangeIter)
+	it := fn.emit(rng)
+
+	loop = fn.newBasicBlock("rangeiter.loop")
+	emitJump(fn, loop)
+	fn.currentBlock = loop
+
+	okv := &Next{
+		Iter:     it,
+		IsString: isBasic(typeparams.CoreType(x.Type())),
+	}
+	okv.setType(types.NewTuple(
+		varOk,
+		newVar("k", tk),
+		newVar("v", tv),
+	))
+	fn.emit(okv)
+
+	body := fn.newBasicBlock("rangeiter.body")
+	done = fn.newBasicBlock("rangeiter.done")
+	emitIf(fn, emitExtract(fn, okv, 0), body, done)
+	fn.currentBlock = body
+
+	if tk != tInvalid {
+		k = emitExtract(fn, okv, 1)
+	}
+	if tv != tInvalid {
+		v = emitExtract(fn, okv, 2)
+	}
+	return
+}
+
+// rangeChan emits to fn the header for a loop that receives from
+// channel x until it fails.
+// tk is the channel's element type, or nil if the k result is
+// not wanted
+// pos is the position of the '=' or ':=' token.
+func (b *builder) rangeChan(fn *Function, x Value, tk types.Type, pos token.Pos) (k Value, loop, done *BasicBlock) {
+	//
+	// loop:                                   (target of continue)
+	//     ko = <-x                            (key, ok)
+	//     ok = extract ko #1
+	//     if ok goto body else done
+	// body:
+	//     k = extract ko #0
+	//     ...body...
+	//     goto loop
+	// done:                                   (target of break)
+
+	loop = fn.newBasicBlock("rangechan.loop")
+	emitJump(fn, loop)
+	fn.currentBlock = loop
+	recv := &UnOp{
+		Op:      token.ARROW,
+		X:       x,
+		CommaOk: true,
+	}
+	recv.setPos(pos)
+	recv.setType(types.NewTuple(
+		newVar("k", typeparams.CoreType(x.Type()).(*types.Chan).Elem()),
+		varOk,
+	))
+	ko := fn.emit(recv)
+	body := fn.newBasicBlock("rangechan.body")
+	done = fn.newBasicBlock("rangechan.done")
+	emitIf(fn, emitExtract(fn, ko, 1), body, done)
+	fn.currentBlock = body
+	if tk != nil {
+		k = emitExtract(fn, ko, 0)
+	}
+	return
+}
+
+// rangeInt emits to fn the header for a range loop with an integer operand.
+// tk is the key value's type, or nil if the k result is not wanted.
+// pos is the position of the "for" token.
+func (b *builder) rangeInt(fn *Function, x Value, tk types.Type, pos token.Pos) (k Value, loop, done *BasicBlock) {
+	//
+	//     iter = 0
+	//     if 0 < x goto body else done
+	// loop:                                   (target of continue)
+	//     iter++
+	//     if iter < x goto body else done
+	// body:
+	//     k = x
+	//     ...body...
+	//     jump loop
+	// done:                                   (target of break)
+
+	if isUntyped(x.Type()) {
+		x = emitConv(fn, x, tInt)
+	}
+
+	T := x.Type()
+	iter := emitLocal(fn, T, token.NoPos, "rangeint.iter")
+	// x may be unsigned. Avoid initializing x to -1.
+
+	body := fn.newBasicBlock("rangeint.body")
+	done = fn.newBasicBlock("rangeint.done")
+	emitIf(fn, emitCompare(fn, token.LSS, zeroConst(T), x, token.NoPos), body, done)
+
+	loop = fn.newBasicBlock("rangeint.loop")
+	fn.currentBlock = loop
+
+	incr := &BinOp{
+		Op: token.ADD,
+		X:  emitLoad(fn, iter),
+		Y:  emitConv(fn, vOne, T),
+	}
+	incr.setType(T)
+	emitStore(fn, iter, fn.emit(incr), pos)
+	emitIf(fn, emitCompare(fn, token.LSS, incr, x, token.NoPos), body, done)
+	fn.currentBlock = body
+
+	if tk != nil {
+		// Integer types (int, uint8, etc.) are named and
+		// we know that k is assignable to x when tk != nil.
+		// This implies tk and T are identical so no conversion is needed.
+		k = emitLoad(fn, iter)
+	}
+
+	return
+}
+
+// rangeStmt emits to fn code for the range statement s, optionally
+// labelled by label.
+func (b *builder) rangeStmt(fn *Function, s *ast.RangeStmt, label *lblock) {
+	var tk, tv types.Type
+	if s.Key != nil && !isBlankIdent(s.Key) {
+		tk = fn.typeOf(s.Key)
+	}
+	if s.Value != nil && !isBlankIdent(s.Value) {
+		tv = fn.typeOf(s.Value)
+	}
+
+	// create locals for s.Key and s.Value.
+	createVars := func() {
+		// Unlike a short variable declaration, a RangeStmt
+		// using := never redeclares an existing variable; it
+		// always creates a new one.
+		if tk != nil {
+			emitLocalVar(fn, identVar(fn, s.Key.(*ast.Ident)))
+		}
+		if tv != nil {
+			emitLocalVar(fn, identVar(fn, s.Value.(*ast.Ident)))
+		}
+	}
+
+	afterGo122 := versions.AtLeast(fn.goversion, versions.Go1_22)
+	if s.Tok == token.DEFINE && !afterGo122 {
+		// pre-go1.22: If iteration variables are defined (:=), this
+		// occurs once outside the loop.
+		createVars()
+	}
+
+	x := b.expr(fn, s.X)
+
+	var k, v Value
+	var loop, done *BasicBlock
+	switch rt := typeparams.CoreType(x.Type()).(type) {
+	case *types.Slice, *types.Array, *types.Pointer: // *array
+		k, v, loop, done = b.rangeIndexed(fn, x, tv, s.For)
+
+	case *types.Chan:
+		k, loop, done = b.rangeChan(fn, x, tk, s.For)
+
+	case *types.Map:
+		k, v, loop, done = b.rangeIter(fn, x, tk, tv, s.For)
+
+	case *types.Basic:
+		switch {
+		case rt.Info()&types.IsString != 0:
+			k, v, loop, done = b.rangeIter(fn, x, tk, tv, s.For)
+
+		case rt.Info()&types.IsInteger != 0:
+			k, loop, done = b.rangeInt(fn, x, tk, s.For)
+
+		default:
+			panic("Cannot range over basic type: " + rt.String())
+		}
+
+	case *types.Signature:
+		// Special case rewrite (fn.goversion >= go1.23):
+		// 	for x := range f { ... }
+		// into
+		// 	f(func(x T) bool { ... })
+		b.rangeFunc(fn, x, tk, tv, s, label)
+		return
+
+	default:
+		panic("Cannot range over: " + rt.String())
+	}
+
+	if s.Tok == token.DEFINE && afterGo122 {
+		// go1.22: If iteration variables are defined (:=), this occurs inside the loop.
+		createVars()
+	}
+
+	// Evaluate both LHS expressions before we update either.
+	var kl, vl lvalue
+	if tk != nil {
+		kl = b.addr(fn, s.Key, false) // non-escaping
+	}
+	if tv != nil {
+		vl = b.addr(fn, s.Value, false) // non-escaping
+	}
+	if tk != nil {
+		kl.store(fn, k)
+	}
+	if tv != nil {
+		vl.store(fn, v)
+	}
+
+	if label != nil {
+		label._break = done
+		label._continue = loop
+	}
+
+	fn.targets = &targets{
+		tail:      fn.targets,
+		_break:    done,
+		_continue: loop,
+	}
+	b.stmt(fn, s.Body)
+	fn.targets = fn.targets.tail
+	emitJump(fn, loop) // back-edge
+	fn.currentBlock = done
+}
+
+// rangeFunc emits to fn code for the range-over-func rng.Body of the iterator
+// function x, optionally labelled by label. It creates a new anonymous function
+// yield for rng and builds the function.
+func (b *builder) rangeFunc(fn *Function, x Value, tk, tv types.Type, rng *ast.RangeStmt, label *lblock) {
+	// Consider the SSA code for the outermost range-over-func in fn:
+	//
+	//   func fn(...) (ret R) {
+	//     ...
+	//     for k, v = range x {
+	// 	     ...
+	//     }
+	//     ...
+	//   }
+	//
+	// The code emitted into fn will look something like this.
+	//
+	// loop:
+	//     jump := READY
+	//     y := make closure yield [ret, deferstack, jump, k, v]
+	//     x(y)
+	//     switch jump {
+	//        [see resuming execution]
+	//     }
+	//     goto done
+	// done:
+	//     ...
+	//
+	// where yield is a new synthetic yield function:
+	//
+	// func yield(_k tk, _v tv) bool
+	//   free variables: [ret, stack, jump, k, v]
+	// {
+	//    entry:
+	//      if jump != READY then goto invalid else valid
+	//    invalid:
+	//      panic("iterator called when it is not in a ready state")
+	//    valid:
+	//      jump = BUSY
+	//      k = _k
+	//      v = _v
+	//    ...
+	//    cont:
+	//      jump = READY
+	//      return true
+	// }
+	//
+	// Yield state:
+	//
+	// Each range loop has an associated jump variable that records
+	// the state of the iterator. A yield function is initially
+	// in a READY (0) and callable state.  If the yield function is called
+	// and is not in READY state, it panics. When it is called in a callable
+	// state, it becomes BUSY. When execution reaches the end of the body
+	// of the loop (or a continue statement targeting the loop is executed),
+	// the yield function returns true and resumes being in a READY state.
+	// After the iterator function x(y) returns, then if the yield function
+	// is in a READY state, the yield enters the DONE state.
+	//
+	// Each lowered control statement (break X, continue X, goto Z, or return)
+	// that exits the loop sets the variable to a unique positive EXIT value,
+	// before returning false from the yield function.
+	//
+	// If the yield function returns abruptly due to a panic or GoExit,
+	// it remains in a BUSY state. The generated code asserts that, after
+	// the iterator call x(y) returns normally, the jump variable state
+	// is DONE.
+	//
+	// Resuming execution:
+	//
+	// The code generated for the range statement checks the jump
+	// variable to determine how to resume execution.
+	//
+	//    switch jump {
+	//    case BUSY:  panic("...")
+	//    case DONE:  goto done
+	//    case READY: state = DONE; goto done
+	//    case 123:   ... // action for exit 123.
+	//    case 456:   ... // action for exit 456.
+	//    ...
+	//    }
+	//
+	// Forward goto statements within a yield are jumps to labels that
+	// have not yet been traversed in fn. They may be in the Body of the
+	// function. What we emit for these is:
+	//
+	//    goto target
+	//  target:
+	//    ...
+	//
+	// We leave an unresolved exit in yield.exits to check at the end
+	// of building yield if it encountered target in the body. If it
+	// encountered target, no additional work is required. Otherwise,
+	// the yield emits a new early exit in the basic block for target.
+	// We expect that blockopt will fuse the early exit into the case
+	// block later. The unresolved exit is then added to yield.parent.exits.
+
+	loop := fn.newBasicBlock("rangefunc.loop")
+	done := fn.newBasicBlock("rangefunc.done")
+
+	// These are targets within y.
+	fn.targets = &targets{
+		tail:   fn.targets,
+		_break: done,
+		// _continue is within y.
+	}
+	if label != nil {
+		label._break = done
+		// _continue is within y
+	}
+
+	emitJump(fn, loop)
+	fn.currentBlock = loop
+
+	// loop:
+	//     jump := READY
+
+	anonIdx := len(fn.AnonFuncs)
+
+	jump := newVar(fmt.Sprintf("jump$%d", anonIdx+1), tInt)
+	emitLocalVar(fn, jump) // zero value is READY
+
+	xsig := typeparams.CoreType(x.Type()).(*types.Signature)
+	ysig := typeparams.CoreType(xsig.Params().At(0).Type()).(*types.Signature)
+
+	/* synthetic yield function for body of range-over-func loop */
+	y := &Function{
+		name:           fmt.Sprintf("%s$%d", fn.Name(), anonIdx+1),
+		Signature:      ysig,
+		Synthetic:      "range-over-func yield",
+		pos:            rangePosition(rng),
+		parent:         fn,
+		anonIdx:        int32(len(fn.AnonFuncs)),
+		Pkg:            fn.Pkg,
+		Prog:           fn.Prog,
+		syntax:         rng,
+		info:           fn.info,
+		goversion:      fn.goversion,
+		build:          (*builder).buildYieldFunc,
+		topLevelOrigin: nil,
+		typeparams:     fn.typeparams,
+		typeargs:       fn.typeargs,
+		subst:          fn.subst,
+		jump:           jump,
+		deferstack:     fn.deferstack,
+		returnVars:     fn.returnVars, // use the parent's return variables
+		uniq:           fn.uniq,       // start from parent's unique values
+	}
+
+	// If the RangeStmt has a label, this is how it is passed to buildYieldFunc.
+	if label != nil {
+		y.lblocks = map[*types.Label]*lblock{label.label: nil}
+	}
+	fn.AnonFuncs = append(fn.AnonFuncs, y)
+
+	// Build y immediately. It may:
+	// * cause fn's locals to escape, and
+	// * create new exit nodes in exits.
+	// (y is not marked 'built' until the end of the enclosing FuncDecl.)
+	unresolved := len(fn.exits)
+	y.build(b, y)
+	fn.uniq = y.uniq // resume after y's unique values
+
+	// Emit the call of y.
+	//   c := MakeClosure y
+	//   x(c)
+	c := &MakeClosure{Fn: y}
+	c.setType(ysig)
+	for _, fv := range y.FreeVars {
+		c.Bindings = append(c.Bindings, fv.outer)
+		fv.outer = nil
+	}
+	fn.emit(c)
+	call := Call{
+		Call: CallCommon{
+			Value: x,
+			Args:  []Value{c},
+			pos:   token.NoPos,
+		},
+	}
+	call.setType(xsig.Results())
+	fn.emit(&call)
+
+	exits := fn.exits[unresolved:]
+	b.buildYieldResume(fn, jump, exits, done)
+
+	emitJump(fn, done)
+	fn.currentBlock = done
+}
+
+// buildYieldResume emits to fn code for how to resume execution once a call to
+// the iterator function over the yield function returns x(y). It does this by building
+// a switch over the value of jump for when it is READY, BUSY, or EXIT(id).
+func (b *builder) buildYieldResume(fn *Function, jump *types.Var, exits []*exit, done *BasicBlock) {
+	//    v := *jump
+	//    switch v {
+	//    case BUSY:    panic("...")
+	//    case READY:   jump = DONE; goto done
+	//    case EXIT(a): ...
+	//    case EXIT(b): ...
+	//    ...
+	//    }
+	v := emitLoad(fn, fn.lookup(jump, false))
+
+	// case BUSY: panic("...")
+	isbusy := fn.newBasicBlock("rangefunc.resume.busy")
+	ifready := fn.newBasicBlock("rangefunc.resume.ready.check")
+	emitIf(fn, emitCompare(fn, token.EQL, v, jBusy, token.NoPos), isbusy, ifready)
+	fn.currentBlock = isbusy
+	fn.emit(&Panic{
+		X: emitConv(fn, stringConst("iterator call did not preserve panic"), tEface),
+	})
+	fn.currentBlock = ifready
+
+	// case READY: jump = DONE; goto done
+	isready := fn.newBasicBlock("rangefunc.resume.ready")
+	ifexit := fn.newBasicBlock("rangefunc.resume.exits")
+	emitIf(fn, emitCompare(fn, token.EQL, v, jReady, token.NoPos), isready, ifexit)
+	fn.currentBlock = isready
+	storeVar(fn, jump, jDone, token.NoPos)
+	emitJump(fn, done)
+	fn.currentBlock = ifexit
+
+	for _, e := range exits {
+		id := intConst(e.id)
+
+		//  case EXIT(id): { /* do e */ }
+		cond := emitCompare(fn, token.EQL, v, id, e.pos)
+		matchb := fn.newBasicBlock("rangefunc.resume.match")
+		cndb := fn.newBasicBlock("rangefunc.resume.cnd")
+		emitIf(fn, cond, matchb, cndb)
+		fn.currentBlock = matchb
+
+		// Cases to fill in the { /* do e */ } bit.
+		switch {
+		case e.label != nil: // forward goto?
+			// case EXIT(id): goto lb // label
+			lb := fn.lblockOf(e.label)
+			// Do not mark lb as resolved.
+			// If fn does not contain label, lb remains unresolved and
+			// fn must itself be a range-over-func function. lb will be:
+			//   lb:
+			//     fn.jump = id
+			//     return false
+			emitJump(fn, lb._goto)
+
+		case e.to != fn: // e jumps to an ancestor of fn?
+			// case EXIT(id): { fn.jump = id; return false }
+			// fn is a range-over-func function.
+			storeVar(fn, fn.jump, id, token.NoPos)
+			fn.emit(&Return{Results: []Value{vFalse}, pos: e.pos})
+
+		case e.block == nil && e.label == nil: // return from fn?
+			// case EXIT(id): { return ... }
+			fn.emit(new(RunDefers))
+			results := make([]Value, len(fn.results))
+			for i, r := range fn.results {
+				results[i] = emitLoad(fn, r)
+			}
+			fn.emit(&Return{Results: results, pos: e.pos})
+
+		case e.block != nil:
+			// case EXIT(id): goto block
+			emitJump(fn, e.block)
+
+		default:
+			panic("unreachable")
+		}
+		fn.currentBlock = cndb
+	}
+}
+
+// stmt lowers statement s to SSA form, emitting code to fn.
+func (b *builder) stmt(fn *Function, _s ast.Stmt) {
+	// The label of the current statement.  If non-nil, its _goto
+	// target is always set; its _break and _continue are set only
+	// within the body of switch/typeswitch/select/for/range.
+	// It is effectively an additional default-nil parameter of stmt().
+	var label *lblock
+start:
+	switch s := _s.(type) {
+	case *ast.EmptyStmt:
+		// ignore.  (Usually removed by gofmt.)
+
+	case *ast.DeclStmt: // Con, Var or Typ
+		d := s.Decl.(*ast.GenDecl)
+		if d.Tok == token.VAR {
+			for _, spec := range d.Specs {
+				if vs, ok := spec.(*ast.ValueSpec); ok {
+					b.localValueSpec(fn, vs)
+				}
+			}
+		}
+
+	case *ast.LabeledStmt:
+		if s.Label.Name == "_" {
+			// Blank labels can't be the target of a goto, break,
+			// or continue statement, so we don't need a new block.
+			_s = s.Stmt
+			goto start
+		}
+		label = fn.lblockOf(fn.label(s.Label))
+		label.resolved = true
+		emitJump(fn, label._goto)
+		fn.currentBlock = label._goto
+		_s = s.Stmt
+		goto start // effectively: tailcall stmt(fn, s.Stmt, label)
+
+	case *ast.ExprStmt:
+		b.expr(fn, s.X)
+
+	case *ast.SendStmt:
+		chtyp := typeparams.CoreType(fn.typeOf(s.Chan)).(*types.Chan)
+		fn.emit(&Send{
+			Chan: b.expr(fn, s.Chan),
+			X:    emitConv(fn, b.expr(fn, s.Value), chtyp.Elem()),
+			pos:  s.Arrow,
+		})
+
+	case *ast.IncDecStmt:
+		op := token.ADD
+		if s.Tok == token.DEC {
+			op = token.SUB
+		}
+		loc := b.addr(fn, s.X, false)
+		b.assignOp(fn, loc, NewConst(constant.MakeInt64(1), loc.typ()), op, s.Pos())
+
+	case *ast.AssignStmt:
+		switch s.Tok {
+		case token.ASSIGN, token.DEFINE:
+			b.assignStmt(fn, s.Lhs, s.Rhs, s.Tok == token.DEFINE)
+
+		default: // +=, etc.
+			op := s.Tok + token.ADD - token.ADD_ASSIGN
+			b.assignOp(fn, b.addr(fn, s.Lhs[0], false), b.expr(fn, s.Rhs[0]), op, s.Pos())
+		}
+
+	case *ast.GoStmt:
+		// The "intrinsics" new/make/len/cap are forbidden here.
+		// panic is treated like an ordinary function call.
+		v := Go{pos: s.Go}
+		b.setCall(fn, s.Call, &v.Call)
+		fn.emit(&v)
+
+	case *ast.DeferStmt:
+		// The "intrinsics" new/make/len/cap are forbidden here.
+		// panic is treated like an ordinary function call.
+		deferstack := emitLoad(fn, fn.lookup(fn.deferstack, false))
+		v := Defer{pos: s.Defer, DeferStack: deferstack}
+		b.setCall(fn, s.Call, &v.Call)
+		fn.emit(&v)
+
+		// A deferred call can cause recovery from panic,
+		// and control resumes at the Recover block.
+		createRecoverBlock(fn.source)
+
+	case *ast.ReturnStmt:
+		b.returnStmt(fn, s)
+
+	case *ast.BranchStmt:
+		b.branchStmt(fn, s)
+
+	case *ast.BlockStmt:
+		b.stmtList(fn, s.List)
+
+	case *ast.IfStmt:
+		if s.Init != nil {
+			b.stmt(fn, s.Init)
+		}
+		then := fn.newBasicBlock("if.then")
+		done := fn.newBasicBlock("if.done")
+		els := done
+		if s.Else != nil {
+			els = fn.newBasicBlock("if.else")
+		}
+		b.cond(fn, s.Cond, then, els)
+		fn.currentBlock = then
+		b.stmt(fn, s.Body)
+		emitJump(fn, done)
+
+		if s.Else != nil {
+			fn.currentBlock = els
+			b.stmt(fn, s.Else)
+			emitJump(fn, done)
+		}
+
+		fn.currentBlock = done
+
+	case *ast.SwitchStmt:
+		b.switchStmt(fn, s, label)
+
+	case *ast.TypeSwitchStmt:
+		b.typeSwitchStmt(fn, s, label)
+
+	case *ast.SelectStmt:
+		b.selectStmt(fn, s, label)
+
+	case *ast.ForStmt:
+		b.forStmt(fn, s, label)
+
+	case *ast.RangeStmt:
+		b.rangeStmt(fn, s, label)
+
+	default:
+		panic(fmt.Sprintf("unexpected statement kind: %T", s))
+	}
+}
+
+func (b *builder) branchStmt(fn *Function, s *ast.BranchStmt) {
+	var block *BasicBlock
+	if s.Label == nil {
+		block = targetedBlock(fn, s.Tok)
+	} else {
+		target := fn.label(s.Label)
+		block = labelledBlock(fn, target, s.Tok)
+		if block == nil { // forward goto
+			lb := fn.lblockOf(target)
+			block = lb._goto // jump to lb._goto
+			if fn.jump != nil {
+				// fn is a range-over-func and the goto may exit fn.
+				// Create an exit and resolve it at the end of
+				// builder.buildYieldFunc.
+				labelExit(fn, target, s.Pos())
+			}
+		}
+	}
+	to := block.parent
+
+	if to == fn {
+		emitJump(fn, block)
+	} else { // break outside of fn.
+		// fn must be a range-over-func
+		e := blockExit(fn, block, s.Pos())
+		storeVar(fn, fn.jump, intConst(e.id), e.pos)
+		fn.emit(&Return{Results: []Value{vFalse}, pos: e.pos})
+	}
+	fn.currentBlock = fn.newBasicBlock("unreachable")
+}
+
+func (b *builder) returnStmt(fn *Function, s *ast.ReturnStmt) {
+	var results []Value
+
+	sig := fn.source.Signature // signature of the enclosing source function
+
+	// Convert return operands to result type.
+	if len(s.Results) == 1 && sig.Results().Len() > 1 {
+		// Return of one expression in a multi-valued function.
+		tuple := b.exprN(fn, s.Results[0])
+		ttuple := tuple.Type().(*types.Tuple)
+		for i, n := 0, ttuple.Len(); i < n; i++ {
+			results = append(results,
+				emitConv(fn, emitExtract(fn, tuple, i),
+					sig.Results().At(i).Type()))
+		}
+	} else {
+		// 1:1 return, or no-arg return in non-void function.
+		for i, r := range s.Results {
+			v := emitConv(fn, b.expr(fn, r), sig.Results().At(i).Type())
+			results = append(results, v)
+		}
+	}
+
+	// Store the results.
+	for i, r := range results {
+		var result Value // fn.source.result[i] conceptually
+		if fn == fn.source {
+			result = fn.results[i]
+		} else { // lookup needed?
+			result = fn.lookup(fn.returnVars[i], false)
+		}
+		emitStore(fn, result, r, s.Return)
+	}
+
+	if fn.jump != nil {
+		// Return from body of a range-over-func.
+		// The return statement is syntactically within the loop,
+		// but the generated code is in the 'switch jump {...}' after it.
+		e := returnExit(fn, s.Pos())
+		storeVar(fn, fn.jump, intConst(e.id), e.pos)
+		fn.emit(&Return{Results: []Value{vFalse}, pos: e.pos})
+		fn.currentBlock = fn.newBasicBlock("unreachable")
+		return
+	}
+
+	// Run function calls deferred in this
+	// function when explicitly returning from it.
+	fn.emit(new(RunDefers))
+	// Reload (potentially) named result variables to form the result tuple.
+	results = results[:0]
+	for _, nr := range fn.results {
+		results = append(results, emitLoad(fn, nr))
+	}
+	fn.emit(&Return{Results: results, pos: s.Return})
+	fn.currentBlock = fn.newBasicBlock("unreachable")
+}
+
+// A buildFunc is a strategy for building the SSA body for a function.
+type buildFunc = func(*builder, *Function)
+
+// iterate causes all created but unbuilt functions to be built. As
+// this may create new methods, the process is iterated until it
+// converges.
+//
+// Waits for any dependencies to finish building.
+func (b *builder) iterate() {
+	for ; b.finished < len(b.fns); b.finished++ {
+		fn := b.fns[b.finished]
+		b.buildFunction(fn)
+	}
+
+	b.buildshared.markDone()
+	b.buildshared.wait()
+}
+
+// buildFunction builds SSA code for the body of function fn.  Idempotent.
+func (b *builder) buildFunction(fn *Function) {
+	if fn.build != nil {
+		assert(fn.parent == nil, "anonymous functions should not be built by buildFunction()")
+
+		if fn.Prog.mode&LogSource != 0 {
+			defer logStack("build %s @ %s", fn, fn.Prog.Fset.Position(fn.pos))()
+		}
+		fn.build(b, fn)
+		fn.done()
+	}
+}
+
+// buildParamsOnly builds fn.Params from fn.Signature, but does not build fn.Body.
+func (b *builder) buildParamsOnly(fn *Function) {
+	// For external (C, asm) functions or functions loaded from
+	// export data, we must set fn.Params even though there is no
+	// body code to reference them.
+	if recv := fn.Signature.Recv(); recv != nil {
+		fn.addParamVar(recv)
+	}
+	params := fn.Signature.Params()
+	for i, n := 0, params.Len(); i < n; i++ {
+		fn.addParamVar(params.At(i))
+	}
+}
+
+// buildFromSyntax builds fn.Body from fn.syntax, which must be non-nil.
+func (b *builder) buildFromSyntax(fn *Function) {
+	var (
+		recvField *ast.FieldList
+		body      *ast.BlockStmt
+		functype  *ast.FuncType
+	)
+	switch syntax := fn.syntax.(type) {
+	case *ast.FuncDecl:
+		functype = syntax.Type
+		recvField = syntax.Recv
+		body = syntax.Body
+		if body == nil {
+			b.buildParamsOnly(fn) // no body (non-Go function)
+			return
+		}
+	case *ast.FuncLit:
+		functype = syntax.Type
+		body = syntax.Body
+	case nil:
+		panic("no syntax")
+	default:
+		panic(syntax) // unexpected syntax
+	}
+	fn.source = fn
+	fn.startBody()
+	fn.createSyntacticParams(recvField, functype)
+	fn.createDeferStack()
+	b.stmt(fn, body)
+	if cb := fn.currentBlock; cb != nil && (cb == fn.Blocks[0] || cb == fn.Recover || cb.Preds != nil) {
+		// Control fell off the end of the function's body block.
+		//
+		// Block optimizations eliminate the current block, if
+		// unreachable.  It is a builder invariant that
+		// if this no-arg return is ill-typed for
+		// fn.Signature.Results, this block must be
+		// unreachable.  The sanity checker checks this.
+		fn.emit(new(RunDefers))
+		fn.emit(new(Return))
+	}
+	fn.finishBody()
+}
+
+// buildYieldFunc builds the body of the yield function created
+// from a range-over-func *ast.RangeStmt.
+func (b *builder) buildYieldFunc(fn *Function) {
+	// See builder.rangeFunc for detailed documentation on how fn is set up.
+	//
+	// In psuedo-Go this roughly builds:
+	// func yield(_k tk, _v tv) bool {
+	// 	   if jump != READY { panic("yield function called after range loop exit") }
+	//     jump = BUSY
+	//     k, v = _k, _v // assign the iterator variable (if needed)
+	//     ... // rng.Body
+	//   continue:
+	//     jump = READY
+	//     return true
+	// }
+	s := fn.syntax.(*ast.RangeStmt)
+	fn.source = fn.parent.source
+	fn.startBody()
+	params := fn.Signature.Params()
+	for i := 0; i < params.Len(); i++ {
+		fn.addParamVar(params.At(i))
+	}
+
+	// Initial targets
+	ycont := fn.newBasicBlock("yield-continue")
+	// lblocks is either {} or is {label: nil} where label is the label of syntax.
+	for label := range fn.lblocks {
+		fn.lblocks[label] = &lblock{
+			label:     label,
+			resolved:  true,
+			_goto:     ycont,
+			_continue: ycont,
+			// `break label` statement targets fn.parent.targets._break
+		}
+	}
+	fn.targets = &targets{
+		_continue: ycont,
+		// `break` statement targets fn.parent.targets._break.
+	}
+
+	// continue:
+	//   jump = READY
+	//   return true
+	saved := fn.currentBlock
+	fn.currentBlock = ycont
+	storeVar(fn, fn.jump, jReady, s.Body.Rbrace)
+	// A yield function's own deferstack is always empty, so rundefers is not needed.
+	fn.emit(&Return{Results: []Value{vTrue}, pos: token.NoPos})
+
+	// Emit header:
+	//
+	//   if jump != READY { panic("yield iterator accessed after exit") }
+	//   jump = BUSY
+	//   k, v = _k, _v
+	fn.currentBlock = saved
+	yloop := fn.newBasicBlock("yield-loop")
+	invalid := fn.newBasicBlock("yield-invalid")
+
+	jumpVal := emitLoad(fn, fn.lookup(fn.jump, true))
+	emitIf(fn, emitCompare(fn, token.EQL, jumpVal, jReady, token.NoPos), yloop, invalid)
+	fn.currentBlock = invalid
+	fn.emit(&Panic{
+		X: emitConv(fn, stringConst("yield function called after range loop exit"), tEface),
+	})
+
+	fn.currentBlock = yloop
+	storeVar(fn, fn.jump, jBusy, s.Body.Rbrace)
+
+	// Initialize k and v from params.
+	var tk, tv types.Type
+	if s.Key != nil && !isBlankIdent(s.Key) {
+		tk = fn.typeOf(s.Key) // fn.parent.typeOf is identical
+	}
+	if s.Value != nil && !isBlankIdent(s.Value) {
+		tv = fn.typeOf(s.Value)
+	}
+	if s.Tok == token.DEFINE {
+		if tk != nil {
+			emitLocalVar(fn, identVar(fn, s.Key.(*ast.Ident)))
+		}
+		if tv != nil {
+			emitLocalVar(fn, identVar(fn, s.Value.(*ast.Ident)))
+		}
+	}
+	var k, v Value
+	if len(fn.Params) > 0 {
+		k = fn.Params[0]
+	}
+	if len(fn.Params) > 1 {
+		v = fn.Params[1]
+	}
+	var kl, vl lvalue
+	if tk != nil {
+		kl = b.addr(fn, s.Key, false) // non-escaping
+	}
+	if tv != nil {
+		vl = b.addr(fn, s.Value, false) // non-escaping
+	}
+	if tk != nil {
+		kl.store(fn, k)
+	}
+	if tv != nil {
+		vl.store(fn, v)
+	}
+
+	// Build the body of the range loop.
+	b.stmt(fn, s.Body)
+	if cb := fn.currentBlock; cb != nil && (cb == fn.Blocks[0] || cb == fn.Recover || cb.Preds != nil) {
+		// Control fell off the end of the function's body block.
+		// Block optimizations eliminate the current block, if
+		// unreachable.
+		emitJump(fn, ycont)
+	}
+
+	// Clean up exits and promote any unresolved exits to fn.parent.
+	for _, e := range fn.exits {
+		if e.label != nil {
+			lb := fn.lblocks[e.label]
+			if lb.resolved {
+				// label was resolved. Do not turn lb into an exit.
+				// e does not need to be handled by the parent.
+				continue
+			}
+
+			// _goto becomes an exit.
+			//   _goto:
+			//     jump = id
+			//     return false
+			fn.currentBlock = lb._goto
+			id := intConst(e.id)
+			storeVar(fn, fn.jump, id, e.pos)
+			fn.emit(&Return{Results: []Value{vFalse}, pos: e.pos})
+		}
+
+		if e.to != fn { // e needs to be handled by the parent too.
+			fn.parent.exits = append(fn.parent.exits, e)
+		}
+	}
+
+	fn.finishBody()
+}
+
+// addRuntimeType records t as a runtime type,
+// along with all types derivable from it using reflection.
+//
+// Acquires prog.runtimeTypesMu.
+func addRuntimeType(prog *Program, t types.Type) {
+	prog.runtimeTypesMu.Lock()
+	defer prog.runtimeTypesMu.Unlock()
+	forEachReachable(&prog.MethodSets, t, func(t types.Type) bool {
+		prev, _ := prog.runtimeTypes.Set(t, true).(bool)
+		return !prev // already seen?
+	})
+}
+
+// Build calls Package.Build for each package in prog.
+// Building occurs in parallel unless the BuildSerially mode flag was set.
+//
+// Build is intended for whole-program analysis; a typical compiler
+// need only build a single package.
+//
+// Build is idempotent and thread-safe.
+func (prog *Program) Build() {
+	var wg sync.WaitGroup
+	for _, p := range prog.packages {
+		if prog.mode&BuildSerially != 0 {
+			p.Build()
+		} else {
+			wg.Add(1)
+			cpuLimit <- unit{} // acquire a token
+			go func(p *Package) {
+				p.Build()
+				wg.Done()
+				<-cpuLimit // release a token
+			}(p)
+		}
+	}
+	wg.Wait()
+}
+
+// cpuLimit is a counting semaphore to limit CPU parallelism.
+var cpuLimit = make(chan unit, runtime.GOMAXPROCS(0))
+
+// Build builds SSA code for all functions and vars in package p.
+//
+// CreatePackage must have been called for all of p's direct imports
+// (and hence its direct imports must have been error-free). It is not
+// necessary to call CreatePackage for indirect dependencies.
+// Functions will be created for all necessary methods in those
+// packages on demand.
+//
+// Build is idempotent and thread-safe.
+func (p *Package) Build() { p.buildOnce.Do(p.build) }
+
+func (p *Package) build() {
+	if p.info == nil {
+		return // synthetic package, e.g. "testmain"
+	}
+	if p.Prog.mode&LogSource != 0 {
+		defer logStack("build %s", p)()
+	}
+
+	b := builder{fns: p.created}
+	b.iterate()
+
+	// We no longer need transient information: ASTs or go/types deductions.
+	p.info = nil
+	p.created = nil
+	p.files = nil
+	p.initVersion = nil
+
+	if p.Prog.mode&SanityCheckFunctions != 0 {
+		sanityCheckPackage(p)
+	}
+}
+
+// buildPackageInit builds fn.Body for the synthetic package initializer.
+func (b *builder) buildPackageInit(fn *Function) {
+	p := fn.Pkg
+	fn.startBody()
+
+	var done *BasicBlock
+
+	if p.Prog.mode&BareInits == 0 {
+		// Make init() skip if package is already initialized.
+		initguard := p.Var("init$guard")
+		doinit := fn.newBasicBlock("init.start")
+		done = fn.newBasicBlock("init.done")
+		emitIf(fn, emitLoad(fn, initguard), done, doinit)
+		fn.currentBlock = doinit
+		emitStore(fn, initguard, vTrue, token.NoPos)
+
+		// Call the init() function of each package we import.
+		for _, pkg := range p.Pkg.Imports() {
+			prereq := p.Prog.packages[pkg]
+			if prereq == nil {
+				panic(fmt.Sprintf("Package(%q).Build(): unsatisfied import: Program.CreatePackage(%q) was not called", p.Pkg.Path(), pkg.Path()))
+			}
+			var v Call
+			v.Call.Value = prereq.init
+			v.Call.pos = fn.pos
+			v.setType(types.NewTuple())
+			fn.emit(&v)
+		}
+	}
+
+	// Initialize package-level vars in correct order.
+	if len(p.info.InitOrder) > 0 && len(p.files) == 0 {
+		panic("no source files provided for package. cannot initialize globals")
+	}
+
+	for _, varinit := range p.info.InitOrder {
+		if fn.Prog.mode&LogSource != 0 {
+			fmt.Fprintf(os.Stderr, "build global initializer %v @ %s\n",
+				varinit.Lhs, p.Prog.Fset.Position(varinit.Rhs.Pos()))
+		}
+		// Initializers for global vars are evaluated in dependency
+		// order, but may come from arbitrary files of the package
+		// with different versions, so we transiently update
+		// fn.goversion for each one. (Since init is a synthetic
+		// function it has no syntax of its own that needs a version.)
+		fn.goversion = p.initVersion[varinit.Rhs]
+		if len(varinit.Lhs) == 1 {
+			// 1:1 initialization: var x, y = a(), b()
+			var lval lvalue
+			if v := varinit.Lhs[0]; v.Name() != "_" {
+				lval = &address{addr: p.objects[v].(*Global), pos: v.Pos()}
+			} else {
+				lval = blank{}
+			}
+			b.assign(fn, lval, varinit.Rhs, true, nil)
+		} else {
+			// n:1 initialization: var x, y :=  f()
+			tuple := b.exprN(fn, varinit.Rhs)
+			for i, v := range varinit.Lhs {
+				if v.Name() == "_" {
+					continue
+				}
+				emitStore(fn, p.objects[v].(*Global), emitExtract(fn, tuple, i), v.Pos())
+			}
+		}
+	}
+
+	// The rest of the init function is synthetic:
+	// no syntax, info, goversion.
+	fn.info = nil
+	fn.goversion = ""
+
+	// Call all of the declared init() functions in source order.
+	for _, file := range p.files {
+		for _, decl := range file.Decls {
+			if decl, ok := decl.(*ast.FuncDecl); ok {
+				id := decl.Name
+				if !isBlankIdent(id) && id.Name == "init" && decl.Recv == nil {
+					declaredInit := p.objects[p.info.Defs[id]].(*Function)
+					var v Call
+					v.Call.Value = declaredInit
+					v.setType(types.NewTuple())
+					p.init.emit(&v)
+				}
+			}
+		}
+	}
+
+	// Finish up init().
+	if p.Prog.mode&BareInits == 0 {
+		emitJump(fn, done)
+		fn.currentBlock = done
+	}
+	fn.emit(new(Return))
+	fn.finishBody()
+}
diff --git a/vendor/golang.org/x/tools/go/ssa/const.go b/vendor/golang.org/x/tools/go/ssa/const.go
new file mode 100644
index 0000000..2a4e0dd
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ssa/const.go
@@ -0,0 +1,232 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// This file defines the Const SSA value type.
+
+import (
+	"fmt"
+	"go/constant"
+	"go/token"
+	"go/types"
+	"strconv"
+	"strings"
+
+	"golang.org/x/tools/internal/aliases"
+	"golang.org/x/tools/internal/typeparams"
+)
+
+// NewConst returns a new constant of the specified value and type.
+// val must be valid according to the specification of Const.Value.
+func NewConst(val constant.Value, typ types.Type) *Const {
+	if val == nil {
+		switch soleTypeKind(typ) {
+		case types.IsBoolean:
+			val = constant.MakeBool(false)
+		case types.IsInteger:
+			val = constant.MakeInt64(0)
+		case types.IsString:
+			val = constant.MakeString("")
+		}
+	}
+	return &Const{typ, val}
+}
+
+// soleTypeKind returns a BasicInfo for which constant.Value can
+// represent all zero values for the types in the type set.
+//
+//	types.IsBoolean for false is a representative.
+//	types.IsInteger for 0
+//	types.IsString for ""
+//	0 otherwise.
+func soleTypeKind(typ types.Type) types.BasicInfo {
+	// State records the set of possible zero values (false, 0, "").
+	// Candidates (perhaps all) are eliminated during the type-set
+	// iteration, which executes at least once.
+	state := types.IsBoolean | types.IsInteger | types.IsString
+	underIs(typeSetOf(typ), func(ut types.Type) bool {
+		var c types.BasicInfo
+		if t, ok := ut.(*types.Basic); ok {
+			c = t.Info()
+		}
+		if c&types.IsNumeric != 0 { // int/float/complex
+			c = types.IsInteger
+		}
+		state = state & c
+		return state != 0
+	})
+	return state
+}
+
+// intConst returns an 'int' constant that evaluates to i.
+// (i is an int64 in case the host is narrower than the target.)
+func intConst(i int64) *Const {
+	return NewConst(constant.MakeInt64(i), tInt)
+}
+
+// stringConst returns a 'string' constant that evaluates to s.
+func stringConst(s string) *Const {
+	return NewConst(constant.MakeString(s), tString)
+}
+
+// zeroConst returns a new "zero" constant of the specified type.
+func zeroConst(t types.Type) *Const {
+	return NewConst(nil, t)
+}
+
+func (c *Const) RelString(from *types.Package) string {
+	var s string
+	if c.Value == nil {
+		s = zeroString(c.typ, from)
+	} else if c.Value.Kind() == constant.String {
+		s = constant.StringVal(c.Value)
+		const max = 20
+		// TODO(adonovan): don't cut a rune in half.
+		if len(s) > max {
+			s = s[:max-3] + "..." // abbreviate
+		}
+		s = strconv.Quote(s)
+	} else {
+		s = c.Value.String()
+	}
+	return s + ":" + relType(c.Type(), from)
+}
+
+// zeroString returns the string representation of the "zero" value of the type t.
+func zeroString(t types.Type, from *types.Package) string {
+	switch t := t.(type) {
+	case *types.Basic:
+		switch {
+		case t.Info()&types.IsBoolean != 0:
+			return "false"
+		case t.Info()&types.IsNumeric != 0:
+			return "0"
+		case t.Info()&types.IsString != 0:
+			return `""`
+		case t.Kind() == types.UnsafePointer:
+			fallthrough
+		case t.Kind() == types.UntypedNil:
+			return "nil"
+		default:
+			panic(fmt.Sprint("zeroString for unexpected type:", t))
+		}
+	case *types.Pointer, *types.Slice, *types.Interface, *types.Chan, *types.Map, *types.Signature:
+		return "nil"
+	case *types.Named, *aliases.Alias:
+		return zeroString(t.Underlying(), from)
+	case *types.Array, *types.Struct:
+		return relType(t, from) + "{}"
+	case *types.Tuple:
+		// Tuples are not normal values.
+		// We are currently format as "(t[0], ..., t[n])". Could be something else.
+		components := make([]string, t.Len())
+		for i := 0; i < t.Len(); i++ {
+			components[i] = zeroString(t.At(i).Type(), from)
+		}
+		return "(" + strings.Join(components, ", ") + ")"
+	case *types.TypeParam:
+		return "*new(" + relType(t, from) + ")"
+	}
+	panic(fmt.Sprint("zeroString: unexpected ", t))
+}
+
+func (c *Const) Name() string {
+	return c.RelString(nil)
+}
+
+func (c *Const) String() string {
+	return c.Name()
+}
+
+func (c *Const) Type() types.Type {
+	return c.typ
+}
+
+func (c *Const) Referrers() *[]Instruction {
+	return nil
+}
+
+func (c *Const) Parent() *Function { return nil }
+
+func (c *Const) Pos() token.Pos {
+	return token.NoPos
+}
+
+// IsNil returns true if this constant is a nil value of
+// a nillable reference type (pointer, slice, channel, map, or function),
+// a basic interface type, or
+// a type parameter all of whose possible instantiations are themselves nillable.
+func (c *Const) IsNil() bool {
+	return c.Value == nil && nillable(c.typ)
+}
+
+// nillable reports whether *new(T) == nil is legal for type T.
+func nillable(t types.Type) bool {
+	if typeparams.IsTypeParam(t) {
+		return underIs(typeSetOf(t), func(u types.Type) bool {
+			// empty type set (u==nil) => any underlying types => not nillable
+			return u != nil && nillable(u)
+		})
+	}
+	switch t.Underlying().(type) {
+	case *types.Pointer, *types.Slice, *types.Chan, *types.Map, *types.Signature:
+		return true
+	case *types.Interface:
+		return true // basic interface.
+	default:
+		return false
+	}
+}
+
+// TODO(adonovan): move everything below into golang.org/x/tools/go/ssa/interp.
+
+// Int64 returns the numeric value of this constant truncated to fit
+// a signed 64-bit integer.
+func (c *Const) Int64() int64 {
+	switch x := constant.ToInt(c.Value); x.Kind() {
+	case constant.Int:
+		if i, ok := constant.Int64Val(x); ok {
+			return i
+		}
+		return 0
+	case constant.Float:
+		f, _ := constant.Float64Val(x)
+		return int64(f)
+	}
+	panic(fmt.Sprintf("unexpected constant value: %T", c.Value))
+}
+
+// Uint64 returns the numeric value of this constant truncated to fit
+// an unsigned 64-bit integer.
+func (c *Const) Uint64() uint64 {
+	switch x := constant.ToInt(c.Value); x.Kind() {
+	case constant.Int:
+		if u, ok := constant.Uint64Val(x); ok {
+			return u
+		}
+		return 0
+	case constant.Float:
+		f, _ := constant.Float64Val(x)
+		return uint64(f)
+	}
+	panic(fmt.Sprintf("unexpected constant value: %T", c.Value))
+}
+
+// Float64 returns the numeric value of this constant truncated to fit
+// a float64.
+func (c *Const) Float64() float64 {
+	x := constant.ToFloat(c.Value) // (c.Value == nil) => x.Kind() == Unknown
+	f, _ := constant.Float64Val(x)
+	return f
+}
+
+// Complex128 returns the complex value of this constant truncated to
+// fit a complex128.
+func (c *Const) Complex128() complex128 {
+	x := constant.ToComplex(c.Value) // (c.Value == nil) => x.Kind() == Unknown
+	re, _ := constant.Float64Val(constant.Real(x))
+	im, _ := constant.Float64Val(constant.Imag(x))
+	return complex(re, im)
+}
diff --git a/vendor/golang.org/x/tools/go/ssa/coretype.go b/vendor/golang.org/x/tools/go/ssa/coretype.go
new file mode 100644
index 0000000..8c218f9
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ssa/coretype.go
@@ -0,0 +1,161 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+import (
+	"go/types"
+
+	"golang.org/x/tools/internal/aliases"
+	"golang.org/x/tools/internal/typeparams"
+)
+
+// Utilities for dealing with core types.
+
+// isBytestring returns true if T has the same terms as interface{[]byte | string}.
+// These act like a core type for some operations: slice expressions, append and copy.
+//
+// See https://go.dev/ref/spec#Core_types for the details on bytestring.
+func isBytestring(T types.Type) bool {
+	U := T.Underlying()
+	if _, ok := U.(*types.Interface); !ok {
+		return false
+	}
+
+	tset := typeSetOf(U)
+	if tset.Len() != 2 {
+		return false
+	}
+	hasBytes, hasString := false, false
+	underIs(tset, func(t types.Type) bool {
+		switch {
+		case isString(t):
+			hasString = true
+		case isByteSlice(t):
+			hasBytes = true
+		}
+		return hasBytes || hasString
+	})
+	return hasBytes && hasString
+}
+
+// termList is a list of types.
+type termList []*types.Term            // type terms of the type set
+func (s termList) Len() int            { return len(s) }
+func (s termList) At(i int) types.Type { return s[i].Type() }
+
+// typeSetOf returns the type set of typ. Returns an empty typeset on an error.
+func typeSetOf(typ types.Type) termList {
+	// This is a adaptation of x/exp/typeparams.NormalTerms which x/tools cannot depend on.
+	var terms []*types.Term
+	var err error
+	// typeSetOf(t) == typeSetOf(Unalias(t))
+	switch typ := aliases.Unalias(typ).(type) {
+	case *types.TypeParam:
+		terms, err = typeparams.StructuralTerms(typ)
+	case *types.Union:
+		terms, err = typeparams.UnionTermSet(typ)
+	case *types.Interface:
+		terms, err = typeparams.InterfaceTermSet(typ)
+	default:
+		// Common case.
+		// Specializing the len=1 case to avoid a slice
+		// had no measurable space/time benefit.
+		terms = []*types.Term{types.NewTerm(false, typ)}
+	}
+
+	if err != nil {
+		return termList(nil)
+	}
+	return termList(terms)
+}
+
+// underIs calls f with the underlying types of the specific type terms
+// of s and reports whether all calls to f returned true. If there are
+// no specific terms, underIs returns the result of f(nil).
+func underIs(s termList, f func(types.Type) bool) bool {
+	if s.Len() == 0 {
+		return f(nil)
+	}
+	for i := 0; i < s.Len(); i++ {
+		u := s.At(i).Underlying()
+		if !f(u) {
+			return false
+		}
+	}
+	return true
+}
+
+// indexType returns the element type and index mode of a IndexExpr over a type.
+// It returns (nil, invalid) if the type is not indexable; this should never occur in a well-typed program.
+func indexType(typ types.Type) (types.Type, indexMode) {
+	switch U := typ.Underlying().(type) {
+	case *types.Array:
+		return U.Elem(), ixArrVar
+	case *types.Pointer:
+		if arr, ok := U.Elem().Underlying().(*types.Array); ok {
+			return arr.Elem(), ixVar
+		}
+	case *types.Slice:
+		return U.Elem(), ixVar
+	case *types.Map:
+		return U.Elem(), ixMap
+	case *types.Basic:
+		return tByte, ixValue // must be a string
+	case *types.Interface:
+		tset := typeSetOf(U)
+		if tset.Len() == 0 {
+			return nil, ixInvalid // no underlying terms or error is empty.
+		}
+
+		elem, mode := indexType(tset.At(0))
+		for i := 1; i < tset.Len() && mode != ixInvalid; i++ {
+			e, m := indexType(tset.At(i))
+			if !types.Identical(elem, e) { // if type checked, just a sanity check
+				return nil, ixInvalid
+			}
+			// Update the mode to the most constrained address type.
+			mode = mode.meet(m)
+		}
+		if mode != ixInvalid {
+			return elem, mode
+		}
+	}
+	return nil, ixInvalid
+}
+
+// An indexMode specifies the (addressing) mode of an index operand.
+//
+// Addressing mode of an index operation is based on the set of
+// underlying types.
+// Hasse diagram of the indexMode meet semi-lattice:
+//
+//	ixVar     ixMap
+//	  |          |
+//	ixArrVar     |
+//	  |          |
+//	ixValue      |
+//	   \        /
+//	  ixInvalid
+type indexMode byte
+
+const (
+	ixInvalid indexMode = iota // index is invalid
+	ixValue                    // index is a computed value (not addressable)
+	ixArrVar                   // like ixVar, but index operand contains an array
+	ixVar                      // index is an addressable variable
+	ixMap                      // index is a map index expression (acts like a variable on lhs, commaok on rhs of an assignment)
+)
+
+// meet is the address type that is constrained by both x and y.
+func (x indexMode) meet(y indexMode) indexMode {
+	if (x == ixMap || y == ixMap) && x != y {
+		return ixInvalid
+	}
+	// Use int representation and return min.
+	if x < y {
+		return y
+	}
+	return x
+}
diff --git a/vendor/golang.org/x/tools/go/ssa/create.go b/vendor/golang.org/x/tools/go/ssa/create.go
new file mode 100644
index 0000000..423bce8
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ssa/create.go
@@ -0,0 +1,318 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// This file implements the CREATE phase of SSA construction.
+// See builder.go for explanation.
+
+import (
+	"fmt"
+	"go/ast"
+	"go/token"
+	"go/types"
+	"os"
+	"sync"
+
+	"golang.org/x/tools/internal/versions"
+)
+
+// NewProgram returns a new SSA Program.
+//
+// mode controls diagnostics and checking during SSA construction.
+//
+// To construct an SSA program:
+//
+//   - Call NewProgram to create an empty Program.
+//   - Call CreatePackage providing typed syntax for each package
+//     you want to build, and call it with types but not
+//     syntax for each of those package's direct dependencies.
+//   - Call [Package.Build] on each syntax package you wish to build,
+//     or [Program.Build] to build all of them.
+//
+// See the Example tests for simple examples.
+func NewProgram(fset *token.FileSet, mode BuilderMode) *Program {
+	return &Program{
+		Fset:     fset,
+		imported: make(map[string]*Package),
+		packages: make(map[*types.Package]*Package),
+		mode:     mode,
+		canon:    newCanonizer(),
+		ctxt:     types.NewContext(),
+	}
+}
+
+// memberFromObject populates package pkg with a member for the
+// typechecker object obj.
+//
+// For objects from Go source code, syntax is the associated syntax
+// tree (for funcs and vars only) and goversion defines the
+// appropriate interpretation; they will be used during the build
+// phase.
+func memberFromObject(pkg *Package, obj types.Object, syntax ast.Node, goversion string) {
+	name := obj.Name()
+	switch obj := obj.(type) {
+	case *types.Builtin:
+		if pkg.Pkg != types.Unsafe {
+			panic("unexpected builtin object: " + obj.String())
+		}
+
+	case *types.TypeName:
+		if name != "_" {
+			pkg.Members[name] = &Type{
+				object: obj,
+				pkg:    pkg,
+			}
+		}
+
+	case *types.Const:
+		c := &NamedConst{
+			object: obj,
+			Value:  NewConst(obj.Val(), obj.Type()),
+			pkg:    pkg,
+		}
+		pkg.objects[obj] = c
+		if name != "_" {
+			pkg.Members[name] = c
+		}
+
+	case *types.Var:
+		g := &Global{
+			Pkg:    pkg,
+			name:   name,
+			object: obj,
+			typ:    types.NewPointer(obj.Type()), // address
+			pos:    obj.Pos(),
+		}
+		pkg.objects[obj] = g
+		if name != "_" {
+			pkg.Members[name] = g
+		}
+
+	case *types.Func:
+		sig := obj.Type().(*types.Signature)
+		if sig.Recv() == nil && name == "init" {
+			pkg.ninit++
+			name = fmt.Sprintf("init#%d", pkg.ninit)
+		}
+		fn := createFunction(pkg.Prog, obj, name, syntax, pkg.info, goversion)
+		fn.Pkg = pkg
+		pkg.created = append(pkg.created, fn)
+		pkg.objects[obj] = fn
+		if name != "_" && sig.Recv() == nil {
+			pkg.Members[name] = fn // package-level function
+		}
+
+	default: // (incl. *types.Package)
+		panic("unexpected Object type: " + obj.String())
+	}
+}
+
+// createFunction creates a function or method. It supports both
+// CreatePackage (with or without syntax) and the on-demand creation
+// of methods in non-created packages based on their types.Func.
+func createFunction(prog *Program, obj *types.Func, name string, syntax ast.Node, info *types.Info, goversion string) *Function {
+	sig := obj.Type().(*types.Signature)
+
+	// Collect type parameters.
+	var tparams *types.TypeParamList
+	if rtparams := sig.RecvTypeParams(); rtparams.Len() > 0 {
+		tparams = rtparams // method of generic type
+	} else if sigparams := sig.TypeParams(); sigparams.Len() > 0 {
+		tparams = sigparams // generic function
+	}
+
+	/* declared function/method (from syntax or export data) */
+	fn := &Function{
+		name:       name,
+		object:     obj,
+		Signature:  sig,
+		build:      (*builder).buildFromSyntax,
+		syntax:     syntax,
+		info:       info,
+		goversion:  goversion,
+		pos:        obj.Pos(),
+		Pkg:        nil, // may be set by caller
+		Prog:       prog,
+		typeparams: tparams,
+	}
+	if fn.syntax == nil {
+		fn.Synthetic = "from type information"
+		fn.build = (*builder).buildParamsOnly
+	}
+	if tparams.Len() > 0 {
+		fn.generic = new(generic)
+	}
+	return fn
+}
+
+// membersFromDecl populates package pkg with members for each
+// typechecker object (var, func, const or type) associated with the
+// specified decl.
+func membersFromDecl(pkg *Package, decl ast.Decl, goversion string) {
+	switch decl := decl.(type) {
+	case *ast.GenDecl: // import, const, type or var
+		switch decl.Tok {
+		case token.CONST:
+			for _, spec := range decl.Specs {
+				for _, id := range spec.(*ast.ValueSpec).Names {
+					memberFromObject(pkg, pkg.info.Defs[id], nil, "")
+				}
+			}
+
+		case token.VAR:
+			for _, spec := range decl.Specs {
+				for _, rhs := range spec.(*ast.ValueSpec).Values {
+					pkg.initVersion[rhs] = goversion
+				}
+				for _, id := range spec.(*ast.ValueSpec).Names {
+					memberFromObject(pkg, pkg.info.Defs[id], spec, goversion)
+				}
+			}
+
+		case token.TYPE:
+			for _, spec := range decl.Specs {
+				id := spec.(*ast.TypeSpec).Name
+				memberFromObject(pkg, pkg.info.Defs[id], nil, "")
+			}
+		}
+
+	case *ast.FuncDecl:
+		id := decl.Name
+		memberFromObject(pkg, pkg.info.Defs[id], decl, goversion)
+	}
+}
+
+// CreatePackage creates and returns an SSA Package from the
+// specified type-checked, error-free file ASTs, and populates its
+// Members mapping.
+//
+// importable determines whether this package should be returned by a
+// subsequent call to ImportedPackage(pkg.Path()).
+//
+// The real work of building SSA form for each function is not done
+// until a subsequent call to Package.Build.
+//
+// CreatePackage should not be called after building any package in
+// the program.
+func (prog *Program) CreatePackage(pkg *types.Package, files []*ast.File, info *types.Info, importable bool) *Package {
+	// TODO(adonovan): assert that no package has yet been built.
+	if pkg == nil {
+		panic("nil pkg") // otherwise pkg.Scope below returns types.Universe!
+	}
+	p := &Package{
+		Prog:    prog,
+		Members: make(map[string]Member),
+		objects: make(map[types.Object]Member),
+		Pkg:     pkg,
+		syntax:  info != nil,
+		// transient values (cleared after Package.Build)
+		info:        info,
+		files:       files,
+		initVersion: make(map[ast.Expr]string),
+	}
+
+	/* synthesized package initializer */
+	p.init = &Function{
+		name:      "init",
+		Signature: new(types.Signature),
+		Synthetic: "package initializer",
+		Pkg:       p,
+		Prog:      prog,
+		build:     (*builder).buildPackageInit,
+		info:      p.info,
+		goversion: "", // See Package.build for details.
+	}
+	p.Members[p.init.name] = p.init
+	p.created = append(p.created, p.init)
+
+	// Allocate all package members: vars, funcs, consts and types.
+	if len(files) > 0 {
+		// Go source package.
+		for _, file := range files {
+			goversion := versions.Lang(versions.FileVersion(p.info, file))
+			for _, decl := range file.Decls {
+				membersFromDecl(p, decl, goversion)
+			}
+		}
+	} else {
+		// GC-compiled binary package (or "unsafe")
+		// No code.
+		// No position information.
+		scope := p.Pkg.Scope()
+		for _, name := range scope.Names() {
+			obj := scope.Lookup(name)
+			memberFromObject(p, obj, nil, "")
+			if obj, ok := obj.(*types.TypeName); ok {
+				// No Unalias: aliases should not duplicate methods.
+				if named, ok := obj.Type().(*types.Named); ok {
+					for i, n := 0, named.NumMethods(); i < n; i++ {
+						memberFromObject(p, named.Method(i), nil, "")
+					}
+				}
+			}
+		}
+	}
+
+	if prog.mode&BareInits == 0 {
+		// Add initializer guard variable.
+		initguard := &Global{
+			Pkg:  p,
+			name: "init$guard",
+			typ:  types.NewPointer(tBool),
+		}
+		p.Members[initguard.Name()] = initguard
+	}
+
+	if prog.mode&GlobalDebug != 0 {
+		p.SetDebugMode(true)
+	}
+
+	if prog.mode&PrintPackages != 0 {
+		printMu.Lock()
+		p.WriteTo(os.Stdout)
+		printMu.Unlock()
+	}
+
+	if importable {
+		prog.imported[p.Pkg.Path()] = p
+	}
+	prog.packages[p.Pkg] = p
+
+	return p
+}
+
+// printMu serializes printing of Packages/Functions to stdout.
+var printMu sync.Mutex
+
+// AllPackages returns a new slice containing all packages created by
+// prog.CreatePackage in unspecified order.
+func (prog *Program) AllPackages() []*Package {
+	pkgs := make([]*Package, 0, len(prog.packages))
+	for _, pkg := range prog.packages {
+		pkgs = append(pkgs, pkg)
+	}
+	return pkgs
+}
+
+// ImportedPackage returns the importable Package whose PkgPath
+// is path, or nil if no such Package has been created.
+//
+// A parameter to CreatePackage determines whether a package should be
+// considered importable. For example, no import declaration can resolve
+// to the ad-hoc main package created by 'go build foo.go'.
+//
+// TODO(adonovan): rethink this function and the "importable" concept;
+// most packages are importable. This function assumes that all
+// types.Package.Path values are unique within the ssa.Program, which is
+// false---yet this function remains very convenient.
+// Clients should use (*Program).Package instead where possible.
+// SSA doesn't really need a string-keyed map of packages.
+//
+// Furthermore, the graph of packages may contain multiple variants
+// (e.g. "p" vs "p as compiled for q.test"), and each has a different
+// view of its dependencies.
+func (prog *Program) ImportedPackage(path string) *Package {
+	return prog.imported[path]
+}
diff --git a/vendor/golang.org/x/tools/go/ssa/doc.go b/vendor/golang.org/x/tools/go/ssa/doc.go
new file mode 100644
index 0000000..3310b55
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ssa/doc.go
@@ -0,0 +1,122 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package ssa defines a representation of the elements of Go programs
+// (packages, types, functions, variables and constants) using a
+// static single-assignment (SSA) form intermediate representation
+// (IR) for the bodies of functions.
+//
+// For an introduction to SSA form, see
+// http://en.wikipedia.org/wiki/Static_single_assignment_form.
+// This page provides a broader reading list:
+// http://www.dcs.gla.ac.uk/~jsinger/ssa.html.
+//
+// The level of abstraction of the SSA form is intentionally close to
+// the source language to facilitate construction of source analysis
+// tools.  It is not intended for machine code generation.
+//
+// All looping, branching and switching constructs are replaced with
+// unstructured control flow.  Higher-level control flow constructs
+// such as multi-way branch can be reconstructed as needed; see
+// [golang.org/x/tools/go/ssa/ssautil.Switches] for an example.
+//
+// The simplest way to create the SSA representation of a package is
+// to load typed syntax trees using [golang.org/x/tools/go/packages], then
+// invoke the [golang.org/x/tools/go/ssa/ssautil.Packages] helper function.
+// (See the package-level Examples named LoadPackages and LoadWholeProgram.)
+// The resulting [ssa.Program] contains all the packages and their
+// members, but SSA code is not created for function bodies until a
+// subsequent call to [Package.Build] or [Program.Build].
+//
+// The builder initially builds a naive SSA form in which all local
+// variables are addresses of stack locations with explicit loads and
+// stores.  Registerisation of eligible locals and φ-node insertion
+// using dominance and dataflow are then performed as a second pass
+// called "lifting" to improve the accuracy and performance of
+// subsequent analyses; this pass can be skipped by setting the
+// NaiveForm builder flag.
+//
+// The primary interfaces of this package are:
+//
+//   - [Member]: a named member of a Go package.
+//   - [Value]: an expression that yields a value.
+//   - [Instruction]: a statement that consumes values and performs computation.
+//   - [Node]: a [Value] or [Instruction] (emphasizing its membership in the SSA value graph)
+//
+// A computation that yields a result implements both the [Value] and
+// [Instruction] interfaces.  The following table shows for each
+// concrete type which of these interfaces it implements.
+//
+//	                   Value?          Instruction?      Member?
+//	*Alloc                ✔               ✔
+//	*BinOp                ✔               ✔
+//	*Builtin              ✔
+//	*Call                 ✔               ✔
+//	*ChangeInterface      ✔               ✔
+//	*ChangeType           ✔               ✔
+//	*Const                ✔
+//	*Convert              ✔               ✔
+//	*DebugRef                             ✔
+//	*Defer                                ✔
+//	*Extract              ✔               ✔
+//	*Field                ✔               ✔
+//	*FieldAddr            ✔               ✔
+//	*FreeVar              ✔
+//	*Function             ✔                               ✔ (func)
+//	*Global               ✔                               ✔ (var)
+//	*Go                                   ✔
+//	*If                                   ✔
+//	*Index                ✔               ✔
+//	*IndexAddr            ✔               ✔
+//	*Jump                                 ✔
+//	*Lookup               ✔               ✔
+//	*MakeChan             ✔               ✔
+//	*MakeClosure          ✔               ✔
+//	*MakeInterface        ✔               ✔
+//	*MakeMap              ✔               ✔
+//	*MakeSlice            ✔               ✔
+//	*MapUpdate                            ✔
+//	*MultiConvert         ✔               ✔
+//	*NamedConst                                           ✔ (const)
+//	*Next                 ✔               ✔
+//	*Panic                                ✔
+//	*Parameter            ✔
+//	*Phi                  ✔               ✔
+//	*Range                ✔               ✔
+//	*Return                               ✔
+//	*RunDefers                            ✔
+//	*Select               ✔               ✔
+//	*Send                                 ✔
+//	*Slice                ✔               ✔
+//	*SliceToArrayPointer  ✔               ✔
+//	*Store                                ✔
+//	*Type                                                 ✔ (type)
+//	*TypeAssert           ✔               ✔
+//	*UnOp                 ✔               ✔
+//
+// Other key types in this package include: [Program], [Package], [Function]
+// and [BasicBlock].
+//
+// The program representation constructed by this package is fully
+// resolved internally, i.e. it does not rely on the names of Values,
+// Packages, Functions, Types or BasicBlocks for the correct
+// interpretation of the program.  Only the identities of objects and
+// the topology of the SSA and type graphs are semantically
+// significant.  (There is one exception: [types.Id] values, which identify field
+// and method names, contain strings.)  Avoidance of name-based
+// operations simplifies the implementation of subsequent passes and
+// can make them very efficient.  Many objects are nonetheless named
+// to aid in debugging, but it is not essential that the names be
+// either accurate or unambiguous.  The public API exposes a number of
+// name-based maps for client convenience.
+//
+// The [golang.org/x/tools/go/ssa/ssautil] package provides various
+// helper functions, for example to simplify loading a Go program into
+// SSA form.
+//
+// TODO(adonovan): write a how-to document for all the various cases
+// of trying to determine corresponding elements across the four
+// domains of source locations, ast.Nodes, types.Objects,
+// ssa.Values/Instructions.
+package ssa // import "golang.org/x/tools/go/ssa"
diff --git a/vendor/golang.org/x/tools/go/ssa/dom.go b/vendor/golang.org/x/tools/go/ssa/dom.go
new file mode 100644
index 0000000..02c1ae8
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ssa/dom.go
@@ -0,0 +1,340 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// This file defines algorithms related to dominance.
+
+// Dominator tree construction ----------------------------------------
+//
+// We use the algorithm described in Lengauer & Tarjan. 1979.  A fast
+// algorithm for finding dominators in a flowgraph.
+// http://doi.acm.org/10.1145/357062.357071
+//
+// We also apply the optimizations to SLT described in Georgiadis et
+// al, Finding Dominators in Practice, JGAA 2006,
+// http://jgaa.info/accepted/2006/GeorgiadisTarjanWerneck2006.10.1.pdf
+// to avoid the need for buckets of size > 1.
+
+import (
+	"bytes"
+	"fmt"
+	"math/big"
+	"os"
+	"sort"
+)
+
+// Idom returns the block that immediately dominates b:
+// its parent in the dominator tree, if any.
+// Neither the entry node (b.Index==0) nor recover node
+// (b==b.Parent().Recover()) have a parent.
+func (b *BasicBlock) Idom() *BasicBlock { return b.dom.idom }
+
+// Dominees returns the list of blocks that b immediately dominates:
+// its children in the dominator tree.
+func (b *BasicBlock) Dominees() []*BasicBlock { return b.dom.children }
+
+// Dominates reports whether b dominates c.
+func (b *BasicBlock) Dominates(c *BasicBlock) bool {
+	return b.dom.pre <= c.dom.pre && c.dom.post <= b.dom.post
+}
+
+// DomPreorder returns a new slice containing the blocks of f
+// in a preorder traversal of the dominator tree.
+func (f *Function) DomPreorder() []*BasicBlock {
+	slice := append([]*BasicBlock(nil), f.Blocks...)
+	sort.Slice(slice, func(i, j int) bool {
+		return slice[i].dom.pre < slice[j].dom.pre
+	})
+	return slice
+}
+
+// DomPostorder returns a new slice containing the blocks of f
+// in a postorder traversal of the dominator tree.
+// (This is not the same as a postdominance order.)
+func (f *Function) DomPostorder() []*BasicBlock {
+	slice := append([]*BasicBlock(nil), f.Blocks...)
+	sort.Slice(slice, func(i, j int) bool {
+		return slice[i].dom.post < slice[j].dom.post
+	})
+	return slice
+}
+
+// domInfo contains a BasicBlock's dominance information.
+type domInfo struct {
+	idom      *BasicBlock   // immediate dominator (parent in domtree)
+	children  []*BasicBlock // nodes immediately dominated by this one
+	pre, post int32         // pre- and post-order numbering within domtree
+}
+
+// ltState holds the working state for Lengauer-Tarjan algorithm
+// (during which domInfo.pre is repurposed for CFG DFS preorder number).
+type ltState struct {
+	// Each slice is indexed by b.Index.
+	sdom     []*BasicBlock // b's semidominator
+	parent   []*BasicBlock // b's parent in DFS traversal of CFG
+	ancestor []*BasicBlock // b's ancestor with least sdom
+}
+
+// dfs implements the depth-first search part of the LT algorithm.
+func (lt *ltState) dfs(v *BasicBlock, i int32, preorder []*BasicBlock) int32 {
+	preorder[i] = v
+	v.dom.pre = i // For now: DFS preorder of spanning tree of CFG
+	i++
+	lt.sdom[v.Index] = v
+	lt.link(nil, v)
+	for _, w := range v.Succs {
+		if lt.sdom[w.Index] == nil {
+			lt.parent[w.Index] = v
+			i = lt.dfs(w, i, preorder)
+		}
+	}
+	return i
+}
+
+// eval implements the EVAL part of the LT algorithm.
+func (lt *ltState) eval(v *BasicBlock) *BasicBlock {
+	// TODO(adonovan): opt: do path compression per simple LT.
+	u := v
+	for ; lt.ancestor[v.Index] != nil; v = lt.ancestor[v.Index] {
+		if lt.sdom[v.Index].dom.pre < lt.sdom[u.Index].dom.pre {
+			u = v
+		}
+	}
+	return u
+}
+
+// link implements the LINK part of the LT algorithm.
+func (lt *ltState) link(v, w *BasicBlock) {
+	lt.ancestor[w.Index] = v
+}
+
+// buildDomTree computes the dominator tree of f using the LT algorithm.
+// Precondition: all blocks are reachable (e.g. optimizeBlocks has been run).
+func buildDomTree(f *Function) {
+	// The step numbers refer to the original LT paper; the
+	// reordering is due to Georgiadis.
+
+	// Clear any previous domInfo.
+	for _, b := range f.Blocks {
+		b.dom = domInfo{}
+	}
+
+	n := len(f.Blocks)
+	// Allocate space for 5 contiguous [n]*BasicBlock arrays:
+	// sdom, parent, ancestor, preorder, buckets.
+	space := make([]*BasicBlock, 5*n)
+	lt := ltState{
+		sdom:     space[0:n],
+		parent:   space[n : 2*n],
+		ancestor: space[2*n : 3*n],
+	}
+
+	// Step 1.  Number vertices by depth-first preorder.
+	preorder := space[3*n : 4*n]
+	root := f.Blocks[0]
+	prenum := lt.dfs(root, 0, preorder)
+	recover := f.Recover
+	if recover != nil {
+		lt.dfs(recover, prenum, preorder)
+	}
+
+	buckets := space[4*n : 5*n]
+	copy(buckets, preorder)
+
+	// In reverse preorder...
+	for i := int32(n) - 1; i > 0; i-- {
+		w := preorder[i]
+
+		// Step 3. Implicitly define the immediate dominator of each node.
+		for v := buckets[i]; v != w; v = buckets[v.dom.pre] {
+			u := lt.eval(v)
+			if lt.sdom[u.Index].dom.pre < i {
+				v.dom.idom = u
+			} else {
+				v.dom.idom = w
+			}
+		}
+
+		// Step 2. Compute the semidominators of all nodes.
+		lt.sdom[w.Index] = lt.parent[w.Index]
+		for _, v := range w.Preds {
+			u := lt.eval(v)
+			if lt.sdom[u.Index].dom.pre < lt.sdom[w.Index].dom.pre {
+				lt.sdom[w.Index] = lt.sdom[u.Index]
+			}
+		}
+
+		lt.link(lt.parent[w.Index], w)
+
+		if lt.parent[w.Index] == lt.sdom[w.Index] {
+			w.dom.idom = lt.parent[w.Index]
+		} else {
+			buckets[i] = buckets[lt.sdom[w.Index].dom.pre]
+			buckets[lt.sdom[w.Index].dom.pre] = w
+		}
+	}
+
+	// The final 'Step 3' is now outside the loop.
+	for v := buckets[0]; v != root; v = buckets[v.dom.pre] {
+		v.dom.idom = root
+	}
+
+	// Step 4. Explicitly define the immediate dominator of each
+	// node, in preorder.
+	for _, w := range preorder[1:] {
+		if w == root || w == recover {
+			w.dom.idom = nil
+		} else {
+			if w.dom.idom != lt.sdom[w.Index] {
+				w.dom.idom = w.dom.idom.dom.idom
+			}
+			// Calculate Children relation as inverse of Idom.
+			w.dom.idom.dom.children = append(w.dom.idom.dom.children, w)
+		}
+	}
+
+	pre, post := numberDomTree(root, 0, 0)
+	if recover != nil {
+		numberDomTree(recover, pre, post)
+	}
+
+	// printDomTreeDot(os.Stderr, f)        // debugging
+	// printDomTreeText(os.Stderr, root, 0) // debugging
+
+	if f.Prog.mode&SanityCheckFunctions != 0 {
+		sanityCheckDomTree(f)
+	}
+}
+
+// numberDomTree sets the pre- and post-order numbers of a depth-first
+// traversal of the dominator tree rooted at v.  These are used to
+// answer dominance queries in constant time.
+func numberDomTree(v *BasicBlock, pre, post int32) (int32, int32) {
+	v.dom.pre = pre
+	pre++
+	for _, child := range v.dom.children {
+		pre, post = numberDomTree(child, pre, post)
+	}
+	v.dom.post = post
+	post++
+	return pre, post
+}
+
+// Testing utilities ----------------------------------------
+
+// sanityCheckDomTree checks the correctness of the dominator tree
+// computed by the LT algorithm by comparing against the dominance
+// relation computed by a naive Kildall-style forward dataflow
+// analysis (Algorithm 10.16 from the "Dragon" book).
+func sanityCheckDomTree(f *Function) {
+	n := len(f.Blocks)
+
+	// D[i] is the set of blocks that dominate f.Blocks[i],
+	// represented as a bit-set of block indices.
+	D := make([]big.Int, n)
+
+	one := big.NewInt(1)
+
+	// all is the set of all blocks; constant.
+	var all big.Int
+	all.Set(one).Lsh(&all, uint(n)).Sub(&all, one)
+
+	// Initialization.
+	for i, b := range f.Blocks {
+		if i == 0 || b == f.Recover {
+			// A root is dominated only by itself.
+			D[i].SetBit(&D[0], 0, 1)
+		} else {
+			// All other blocks are (initially) dominated
+			// by every block.
+			D[i].Set(&all)
+		}
+	}
+
+	// Iteration until fixed point.
+	for changed := true; changed; {
+		changed = false
+		for i, b := range f.Blocks {
+			if i == 0 || b == f.Recover {
+				continue
+			}
+			// Compute intersection across predecessors.
+			var x big.Int
+			x.Set(&all)
+			for _, pred := range b.Preds {
+				x.And(&x, &D[pred.Index])
+			}
+			x.SetBit(&x, i, 1) // a block always dominates itself.
+			if D[i].Cmp(&x) != 0 {
+				D[i].Set(&x)
+				changed = true
+			}
+		}
+	}
+
+	// Check the entire relation.  O(n^2).
+	// The Recover block (if any) must be treated specially so we skip it.
+	ok := true
+	for i := 0; i < n; i++ {
+		for j := 0; j < n; j++ {
+			b, c := f.Blocks[i], f.Blocks[j]
+			if c == f.Recover {
+				continue
+			}
+			actual := b.Dominates(c)
+			expected := D[j].Bit(i) == 1
+			if actual != expected {
+				fmt.Fprintf(os.Stderr, "dominates(%s, %s)==%t, want %t\n", b, c, actual, expected)
+				ok = false
+			}
+		}
+	}
+
+	preorder := f.DomPreorder()
+	for _, b := range f.Blocks {
+		if got := preorder[b.dom.pre]; got != b {
+			fmt.Fprintf(os.Stderr, "preorder[%d]==%s, want %s\n", b.dom.pre, got, b)
+			ok = false
+		}
+	}
+
+	if !ok {
+		panic("sanityCheckDomTree failed for " + f.String())
+	}
+
+}
+
+// Printing functions ----------------------------------------
+
+// printDomTreeText prints the dominator tree as text, using indentation.
+func printDomTreeText(buf *bytes.Buffer, v *BasicBlock, indent int) {
+	fmt.Fprintf(buf, "%*s%s\n", 4*indent, "", v)
+	for _, child := range v.dom.children {
+		printDomTreeText(buf, child, indent+1)
+	}
+}
+
+// printDomTreeDot prints the dominator tree of f in AT&T GraphViz
+// (.dot) format.
+func printDomTreeDot(buf *bytes.Buffer, f *Function) {
+	fmt.Fprintln(buf, "//", f)
+	fmt.Fprintln(buf, "digraph domtree {")
+	for i, b := range f.Blocks {
+		v := b.dom
+		fmt.Fprintf(buf, "\tn%d [label=\"%s (%d, %d)\",shape=\"rectangle\"];\n", v.pre, b, v.pre, v.post)
+		// TODO(adonovan): improve appearance of edges
+		// belonging to both dominator tree and CFG.
+
+		// Dominator tree edge.
+		if i != 0 {
+			fmt.Fprintf(buf, "\tn%d -> n%d [style=\"solid\",weight=100];\n", v.idom.dom.pre, v.pre)
+		}
+		// CFG edges.
+		for _, pred := range b.Preds {
+			fmt.Fprintf(buf, "\tn%d -> n%d [style=\"dotted\",weight=0];\n", pred.dom.pre, v.pre)
+		}
+	}
+	fmt.Fprintln(buf, "}")
+}
diff --git a/vendor/golang.org/x/tools/go/ssa/emit.go b/vendor/golang.org/x/tools/go/ssa/emit.go
new file mode 100644
index 0000000..c664ff8
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ssa/emit.go
@@ -0,0 +1,614 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// Helpers for emitting SSA instructions.
+
+import (
+	"fmt"
+	"go/ast"
+	"go/token"
+	"go/types"
+
+	"golang.org/x/tools/internal/typeparams"
+)
+
+// emitAlloc emits to f a new Alloc instruction allocating a variable
+// of type typ.
+//
+// The caller must set Alloc.Heap=true (for an heap-allocated variable)
+// or add the Alloc to f.Locals (for a frame-allocated variable).
+//
+// During building, a variable in f.Locals may have its Heap flag
+// set when it is discovered that its address is taken.
+// These Allocs are removed from f.Locals at the end.
+//
+// The builder should generally call one of the emit{New,Local,LocalVar} wrappers instead.
+func emitAlloc(f *Function, typ types.Type, pos token.Pos, comment string) *Alloc {
+	v := &Alloc{Comment: comment}
+	v.setType(types.NewPointer(typ))
+	v.setPos(pos)
+	f.emit(v)
+	return v
+}
+
+// emitNew emits to f a new Alloc instruction heap-allocating a
+// variable of type typ. pos is the optional source location.
+func emitNew(f *Function, typ types.Type, pos token.Pos, comment string) *Alloc {
+	alloc := emitAlloc(f, typ, pos, comment)
+	alloc.Heap = true
+	return alloc
+}
+
+// emitLocal creates a local var for (t, pos, comment) and
+// emits an Alloc instruction for it.
+//
+// (Use this function or emitNew for synthetic variables;
+// for source-level variables in the same function, use emitLocalVar.)
+func emitLocal(f *Function, t types.Type, pos token.Pos, comment string) *Alloc {
+	local := emitAlloc(f, t, pos, comment)
+	f.Locals = append(f.Locals, local)
+	return local
+}
+
+// emitLocalVar creates a local var for v and emits an Alloc instruction for it.
+// Subsequent calls to f.lookup(v) return it.
+// It applies the appropriate generic instantiation to the type.
+func emitLocalVar(f *Function, v *types.Var) *Alloc {
+	alloc := emitLocal(f, f.typ(v.Type()), v.Pos(), v.Name())
+	f.vars[v] = alloc
+	return alloc
+}
+
+// emitLoad emits to f an instruction to load the address addr into a
+// new temporary, and returns the value so defined.
+func emitLoad(f *Function, addr Value) *UnOp {
+	v := &UnOp{Op: token.MUL, X: addr}
+	v.setType(typeparams.MustDeref(addr.Type()))
+	f.emit(v)
+	return v
+}
+
+// emitDebugRef emits to f a DebugRef pseudo-instruction associating
+// expression e with value v.
+func emitDebugRef(f *Function, e ast.Expr, v Value, isAddr bool) {
+	if !f.debugInfo() {
+		return // debugging not enabled
+	}
+	if v == nil || e == nil {
+		panic("nil")
+	}
+	var obj types.Object
+	e = unparen(e)
+	if id, ok := e.(*ast.Ident); ok {
+		if isBlankIdent(id) {
+			return
+		}
+		obj = f.objectOf(id)
+		switch obj.(type) {
+		case *types.Nil, *types.Const, *types.Builtin:
+			return
+		}
+	}
+	f.emit(&DebugRef{
+		X:      v,
+		Expr:   e,
+		IsAddr: isAddr,
+		object: obj,
+	})
+}
+
+// emitArith emits to f code to compute the binary operation op(x, y)
+// where op is an eager shift, logical or arithmetic operation.
+// (Use emitCompare() for comparisons and Builder.logicalBinop() for
+// non-eager operations.)
+func emitArith(f *Function, op token.Token, x, y Value, t types.Type, pos token.Pos) Value {
+	switch op {
+	case token.SHL, token.SHR:
+		x = emitConv(f, x, t)
+		// y may be signed or an 'untyped' constant.
+
+		// There is a runtime panic if y is signed and <0. Instead of inserting a check for y<0
+		// and converting to an unsigned value (like the compiler) leave y as is.
+
+		if isUntyped(y.Type().Underlying()) {
+			// Untyped conversion:
+			// Spec https://go.dev/ref/spec#Operators:
+			// The right operand in a shift expression must have integer type or be an untyped constant
+			// representable by a value of type uint.
+			y = emitConv(f, y, types.Typ[types.Uint])
+		}
+
+	case token.ADD, token.SUB, token.MUL, token.QUO, token.REM, token.AND, token.OR, token.XOR, token.AND_NOT:
+		x = emitConv(f, x, t)
+		y = emitConv(f, y, t)
+
+	default:
+		panic("illegal op in emitArith: " + op.String())
+
+	}
+	v := &BinOp{
+		Op: op,
+		X:  x,
+		Y:  y,
+	}
+	v.setPos(pos)
+	v.setType(t)
+	return f.emit(v)
+}
+
+// emitCompare emits to f code compute the boolean result of
+// comparison 'x op y'.
+func emitCompare(f *Function, op token.Token, x, y Value, pos token.Pos) Value {
+	xt := x.Type().Underlying()
+	yt := y.Type().Underlying()
+
+	// Special case to optimise a tagless SwitchStmt so that
+	// these are equivalent
+	//   switch { case e: ...}
+	//   switch true { case e: ... }
+	//   if e==true { ... }
+	// even in the case when e's type is an interface.
+	// TODO(adonovan): opt: generalise to x==true, false!=y, etc.
+	if x == vTrue && op == token.EQL {
+		if yt, ok := yt.(*types.Basic); ok && yt.Info()&types.IsBoolean != 0 {
+			return y
+		}
+	}
+
+	if types.Identical(xt, yt) {
+		// no conversion necessary
+	} else if isNonTypeParamInterface(x.Type()) {
+		y = emitConv(f, y, x.Type())
+	} else if isNonTypeParamInterface(y.Type()) {
+		x = emitConv(f, x, y.Type())
+	} else if _, ok := x.(*Const); ok {
+		x = emitConv(f, x, y.Type())
+	} else if _, ok := y.(*Const); ok {
+		y = emitConv(f, y, x.Type())
+	} else {
+		// other cases, e.g. channels.  No-op.
+	}
+
+	v := &BinOp{
+		Op: op,
+		X:  x,
+		Y:  y,
+	}
+	v.setPos(pos)
+	v.setType(tBool)
+	return f.emit(v)
+}
+
+// isValuePreserving returns true if a conversion from ut_src to
+// ut_dst is value-preserving, i.e. just a change of type.
+// Precondition: neither argument is a named or alias type.
+func isValuePreserving(ut_src, ut_dst types.Type) bool {
+	// Identical underlying types?
+	if types.IdenticalIgnoreTags(ut_dst, ut_src) {
+		return true
+	}
+
+	switch ut_dst.(type) {
+	case *types.Chan:
+		// Conversion between channel types?
+		_, ok := ut_src.(*types.Chan)
+		return ok
+
+	case *types.Pointer:
+		// Conversion between pointers with identical base types?
+		_, ok := ut_src.(*types.Pointer)
+		return ok
+	}
+	return false
+}
+
+// emitConv emits to f code to convert Value val to exactly type typ,
+// and returns the converted value.  Implicit conversions are required
+// by language assignability rules in assignments, parameter passing,
+// etc.
+func emitConv(f *Function, val Value, typ types.Type) Value {
+	t_src := val.Type()
+
+	// Identical types?  Conversion is a no-op.
+	if types.Identical(t_src, typ) {
+		return val
+	}
+	ut_dst := typ.Underlying()
+	ut_src := t_src.Underlying()
+
+	// Conversion to, or construction of a value of, an interface type?
+	if isNonTypeParamInterface(typ) {
+		// Interface name change?
+		if isValuePreserving(ut_src, ut_dst) {
+			c := &ChangeType{X: val}
+			c.setType(typ)
+			return f.emit(c)
+		}
+
+		// Assignment from one interface type to another?
+		if isNonTypeParamInterface(t_src) {
+			c := &ChangeInterface{X: val}
+			c.setType(typ)
+			return f.emit(c)
+		}
+
+		// Untyped nil constant?  Return interface-typed nil constant.
+		if ut_src == tUntypedNil {
+			return zeroConst(typ)
+		}
+
+		// Convert (non-nil) "untyped" literals to their default type.
+		if t, ok := ut_src.(*types.Basic); ok && t.Info()&types.IsUntyped != 0 {
+			val = emitConv(f, val, types.Default(ut_src))
+		}
+
+		// Record the types of operands to MakeInterface, if
+		// non-parameterized, as they are the set of runtime types.
+		t := val.Type()
+		if f.typeparams.Len() == 0 || !f.Prog.isParameterized(t) {
+			addRuntimeType(f.Prog, t)
+		}
+
+		mi := &MakeInterface{X: val}
+		mi.setType(typ)
+		return f.emit(mi)
+	}
+
+	// In the common case, the typesets of src and dst are singletons
+	// and we emit an appropriate conversion. But if either contains
+	// a type parameter, the conversion may represent a cross product,
+	// in which case which we emit a MultiConvert.
+	dst_terms := typeSetOf(ut_dst)
+	src_terms := typeSetOf(ut_src)
+
+	// conversionCase describes an instruction pattern that maybe emitted to
+	// model d <- s for d in dst_terms and s in src_terms.
+	// Multiple conversions can match the same pattern.
+	type conversionCase uint8
+	const (
+		changeType conversionCase = 1 << iota
+		sliceToArray
+		sliceToArrayPtr
+		sliceTo0Array
+		sliceTo0ArrayPtr
+		convert
+	)
+	// classify the conversion case of a source type us to a destination type ud.
+	// us and ud are underlying types (not *Named or *Alias)
+	classify := func(us, ud types.Type) conversionCase {
+		// Just a change of type, but not value or representation?
+		if isValuePreserving(us, ud) {
+			return changeType
+		}
+
+		// Conversion from slice to array or slice to array pointer?
+		if slice, ok := us.(*types.Slice); ok {
+			var arr *types.Array
+			var ptr bool
+			// Conversion from slice to array pointer?
+			switch d := ud.(type) {
+			case *types.Array:
+				arr = d
+			case *types.Pointer:
+				arr, _ = d.Elem().Underlying().(*types.Array)
+				ptr = true
+			}
+			if arr != nil && types.Identical(slice.Elem(), arr.Elem()) {
+				if arr.Len() == 0 {
+					if ptr {
+						return sliceTo0ArrayPtr
+					} else {
+						return sliceTo0Array
+					}
+				}
+				if ptr {
+					return sliceToArrayPtr
+				} else {
+					return sliceToArray
+				}
+			}
+		}
+
+		// The only remaining case in well-typed code is a representation-
+		// changing conversion of basic types (possibly with []byte/[]rune).
+		if !isBasic(us) && !isBasic(ud) {
+			panic(fmt.Sprintf("in %s: cannot convert term %s (%s [within %s]) to type %s [within %s]", f, val, val.Type(), us, typ, ud))
+		}
+		return convert
+	}
+
+	var classifications conversionCase
+	for _, s := range src_terms {
+		us := s.Type().Underlying()
+		for _, d := range dst_terms {
+			ud := d.Type().Underlying()
+			classifications |= classify(us, ud)
+		}
+	}
+	if classifications == 0 {
+		panic(fmt.Sprintf("in %s: cannot convert %s (%s) to %s", f, val, val.Type(), typ))
+	}
+
+	// Conversion of a compile-time constant value?
+	if c, ok := val.(*Const); ok {
+		// Conversion to a basic type?
+		if isBasic(ut_dst) {
+			// Conversion of a compile-time constant to
+			// another constant type results in a new
+			// constant of the destination type and
+			// (initially) the same abstract value.
+			// We don't truncate the value yet.
+			return NewConst(c.Value, typ)
+		}
+		// Can we always convert from zero value without panicking?
+		const mayPanic = sliceToArray | sliceToArrayPtr
+		if c.Value == nil && classifications&mayPanic == 0 {
+			return NewConst(nil, typ)
+		}
+
+		// We're converting from constant to non-constant type,
+		// e.g. string -> []byte/[]rune.
+	}
+
+	switch classifications {
+	case changeType: // representation-preserving change
+		c := &ChangeType{X: val}
+		c.setType(typ)
+		return f.emit(c)
+
+	case sliceToArrayPtr, sliceTo0ArrayPtr: // slice to array pointer
+		c := &SliceToArrayPointer{X: val}
+		c.setType(typ)
+		return f.emit(c)
+
+	case sliceToArray: // slice to arrays (not zero-length)
+		ptype := types.NewPointer(typ)
+		p := &SliceToArrayPointer{X: val}
+		p.setType(ptype)
+		x := f.emit(p)
+		unOp := &UnOp{Op: token.MUL, X: x}
+		unOp.setType(typ)
+		return f.emit(unOp)
+
+	case sliceTo0Array: // slice to zero-length arrays (constant)
+		return zeroConst(typ)
+
+	case convert: // representation-changing conversion
+		c := &Convert{X: val}
+		c.setType(typ)
+		return f.emit(c)
+
+	default: // multiple conversion
+		c := &MultiConvert{X: val, from: src_terms, to: dst_terms}
+		c.setType(typ)
+		return f.emit(c)
+	}
+}
+
+// emitTypeCoercion emits to f code to coerce the type of a
+// Value v to exactly type typ, and returns the coerced value.
+//
+// Requires that coercing v.Typ() to typ is a value preserving change.
+//
+// Currently used only when v.Type() is a type instance of typ or vice versa.
+// A type v is a type instance of a type t if there exists a
+// type parameter substitution σ s.t. σ(v) == t. Example:
+//
+//	σ(func(T) T) == func(int) int for σ == [T ↦ int]
+//
+// This happens in instantiation wrappers for conversion
+// from an instantiation to a parameterized type (and vice versa)
+// with σ substituting f.typeparams by f.typeargs.
+func emitTypeCoercion(f *Function, v Value, typ types.Type) Value {
+	if types.Identical(v.Type(), typ) {
+		return v // no coercion needed
+	}
+	// TODO(taking): for instances should we record which side is the instance?
+	c := &ChangeType{
+		X: v,
+	}
+	c.setType(typ)
+	f.emit(c)
+	return c
+}
+
+// emitStore emits to f an instruction to store value val at location
+// addr, applying implicit conversions as required by assignability rules.
+func emitStore(f *Function, addr, val Value, pos token.Pos) *Store {
+	typ := typeparams.MustDeref(addr.Type())
+	s := &Store{
+		Addr: addr,
+		Val:  emitConv(f, val, typ),
+		pos:  pos,
+	}
+	f.emit(s)
+	return s
+}
+
+// emitJump emits to f a jump to target, and updates the control-flow graph.
+// Postcondition: f.currentBlock is nil.
+func emitJump(f *Function, target *BasicBlock) {
+	b := f.currentBlock
+	b.emit(new(Jump))
+	addEdge(b, target)
+	f.currentBlock = nil
+}
+
+// emitIf emits to f a conditional jump to tblock or fblock based on
+// cond, and updates the control-flow graph.
+// Postcondition: f.currentBlock is nil.
+func emitIf(f *Function, cond Value, tblock, fblock *BasicBlock) {
+	b := f.currentBlock
+	b.emit(&If{Cond: cond})
+	addEdge(b, tblock)
+	addEdge(b, fblock)
+	f.currentBlock = nil
+}
+
+// emitExtract emits to f an instruction to extract the index'th
+// component of tuple.  It returns the extracted value.
+func emitExtract(f *Function, tuple Value, index int) Value {
+	e := &Extract{Tuple: tuple, Index: index}
+	e.setType(tuple.Type().(*types.Tuple).At(index).Type())
+	return f.emit(e)
+}
+
+// emitTypeAssert emits to f a type assertion value := x.(t) and
+// returns the value.  x.Type() must be an interface.
+func emitTypeAssert(f *Function, x Value, t types.Type, pos token.Pos) Value {
+	a := &TypeAssert{X: x, AssertedType: t}
+	a.setPos(pos)
+	a.setType(t)
+	return f.emit(a)
+}
+
+// emitTypeTest emits to f a type test value,ok := x.(t) and returns
+// a (value, ok) tuple.  x.Type() must be an interface.
+func emitTypeTest(f *Function, x Value, t types.Type, pos token.Pos) Value {
+	a := &TypeAssert{
+		X:            x,
+		AssertedType: t,
+		CommaOk:      true,
+	}
+	a.setPos(pos)
+	a.setType(types.NewTuple(
+		newVar("value", t),
+		varOk,
+	))
+	return f.emit(a)
+}
+
+// emitTailCall emits to f a function call in tail position.  The
+// caller is responsible for all fields of 'call' except its type.
+// Intended for wrapper methods.
+// Precondition: f does/will not use deferred procedure calls.
+// Postcondition: f.currentBlock is nil.
+func emitTailCall(f *Function, call *Call) {
+	tresults := f.Signature.Results()
+	nr := tresults.Len()
+	if nr == 1 {
+		call.typ = tresults.At(0).Type()
+	} else {
+		call.typ = tresults
+	}
+	tuple := f.emit(call)
+	var ret Return
+	switch nr {
+	case 0:
+		// no-op
+	case 1:
+		ret.Results = []Value{tuple}
+	default:
+		for i := 0; i < nr; i++ {
+			v := emitExtract(f, tuple, i)
+			// TODO(adonovan): in principle, this is required:
+			//   v = emitConv(f, o.Type, f.Signature.Results[i].Type)
+			// but in practice emitTailCall is only used when
+			// the types exactly match.
+			ret.Results = append(ret.Results, v)
+		}
+	}
+	f.emit(&ret)
+	f.currentBlock = nil
+}
+
+// emitImplicitSelections emits to f code to apply the sequence of
+// implicit field selections specified by indices to base value v, and
+// returns the selected value.
+//
+// If v is the address of a struct, the result will be the address of
+// a field; if it is the value of a struct, the result will be the
+// value of a field.
+func emitImplicitSelections(f *Function, v Value, indices []int, pos token.Pos) Value {
+	for _, index := range indices {
+		if isPointerCore(v.Type()) {
+			fld := fieldOf(typeparams.MustDeref(v.Type()), index)
+			instr := &FieldAddr{
+				X:     v,
+				Field: index,
+			}
+			instr.setPos(pos)
+			instr.setType(types.NewPointer(fld.Type()))
+			v = f.emit(instr)
+			// Load the field's value iff indirectly embedded.
+			if isPointerCore(fld.Type()) {
+				v = emitLoad(f, v)
+			}
+		} else {
+			fld := fieldOf(v.Type(), index)
+			instr := &Field{
+				X:     v,
+				Field: index,
+			}
+			instr.setPos(pos)
+			instr.setType(fld.Type())
+			v = f.emit(instr)
+		}
+	}
+	return v
+}
+
+// emitFieldSelection emits to f code to select the index'th field of v.
+//
+// If wantAddr, the input must be a pointer-to-struct and the result
+// will be the field's address; otherwise the result will be the
+// field's value.
+// Ident id is used for position and debug info.
+func emitFieldSelection(f *Function, v Value, index int, wantAddr bool, id *ast.Ident) Value {
+	if isPointerCore(v.Type()) {
+		fld := fieldOf(typeparams.MustDeref(v.Type()), index)
+		instr := &FieldAddr{
+			X:     v,
+			Field: index,
+		}
+		instr.setPos(id.Pos())
+		instr.setType(types.NewPointer(fld.Type()))
+		v = f.emit(instr)
+		// Load the field's value iff we don't want its address.
+		if !wantAddr {
+			v = emitLoad(f, v)
+		}
+	} else {
+		fld := fieldOf(v.Type(), index)
+		instr := &Field{
+			X:     v,
+			Field: index,
+		}
+		instr.setPos(id.Pos())
+		instr.setType(fld.Type())
+		v = f.emit(instr)
+	}
+	emitDebugRef(f, id, v, wantAddr)
+	return v
+}
+
+// createRecoverBlock emits to f a block of code to return after a
+// recovered panic, and sets f.Recover to it.
+//
+// If f's result parameters are named, the code loads and returns
+// their current values, otherwise it returns the zero values of their
+// type.
+//
+// Idempotent.
+func createRecoverBlock(f *Function) {
+	if f.Recover != nil {
+		return // already created
+	}
+	saved := f.currentBlock
+
+	f.Recover = f.newBasicBlock("recover")
+	f.currentBlock = f.Recover
+
+	var results []Value
+	// Reload NRPs to form value tuple.
+	for _, nr := range f.results {
+		results = append(results, emitLoad(f, nr))
+	}
+
+	f.emit(&Return{Results: results})
+
+	f.currentBlock = saved
+}
diff --git a/vendor/golang.org/x/tools/go/ssa/func.go b/vendor/golang.org/x/tools/go/ssa/func.go
new file mode 100644
index 0000000..2ed63bf
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ssa/func.go
@@ -0,0 +1,816 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// This file implements the Function type.
+
+import (
+	"bytes"
+	"fmt"
+	"go/ast"
+	"go/token"
+	"go/types"
+	"io"
+	"os"
+	"strings"
+
+	"golang.org/x/tools/internal/typeparams"
+)
+
+// Like ObjectOf, but panics instead of returning nil.
+// Only valid during f's create and build phases.
+func (f *Function) objectOf(id *ast.Ident) types.Object {
+	if o := f.info.ObjectOf(id); o != nil {
+		return o
+	}
+	panic(fmt.Sprintf("no types.Object for ast.Ident %s @ %s",
+		id.Name, f.Prog.Fset.Position(id.Pos())))
+}
+
+// Like TypeOf, but panics instead of returning nil.
+// Only valid during f's create and build phases.
+func (f *Function) typeOf(e ast.Expr) types.Type {
+	if T := f.info.TypeOf(e); T != nil {
+		return f.typ(T)
+	}
+	panic(fmt.Sprintf("no type for %T @ %s", e, f.Prog.Fset.Position(e.Pos())))
+}
+
+// typ is the locally instantiated type of T.
+// If f is not an instantiation, then f.typ(T)==T.
+func (f *Function) typ(T types.Type) types.Type {
+	return f.subst.typ(T)
+}
+
+// If id is an Instance, returns info.Instances[id].Type.
+// Otherwise returns f.typeOf(id).
+func (f *Function) instanceType(id *ast.Ident) types.Type {
+	if t, ok := f.info.Instances[id]; ok {
+		return t.Type
+	}
+	return f.typeOf(id)
+}
+
+// selection returns a *selection corresponding to f.info.Selections[selector]
+// with potential updates for type substitution.
+func (f *Function) selection(selector *ast.SelectorExpr) *selection {
+	sel := f.info.Selections[selector]
+	if sel == nil {
+		return nil
+	}
+
+	switch sel.Kind() {
+	case types.MethodExpr, types.MethodVal:
+		if recv := f.typ(sel.Recv()); recv != sel.Recv() {
+			// recv changed during type substitution.
+			pkg := f.declaredPackage().Pkg
+			obj, index, indirect := types.LookupFieldOrMethod(recv, true, pkg, sel.Obj().Name())
+
+			// sig replaces sel.Type(). See (types.Selection).Typ() for details.
+			sig := obj.Type().(*types.Signature)
+			sig = changeRecv(sig, newVar(sig.Recv().Name(), recv))
+			if sel.Kind() == types.MethodExpr {
+				sig = recvAsFirstArg(sig)
+			}
+			return &selection{
+				kind:     sel.Kind(),
+				recv:     recv,
+				typ:      sig,
+				obj:      obj,
+				index:    index,
+				indirect: indirect,
+			}
+		}
+	}
+	return toSelection(sel)
+}
+
+// Destinations associated with unlabelled for/switch/select stmts.
+// We push/pop one of these as we enter/leave each construct and for
+// each BranchStmt we scan for the innermost target of the right type.
+type targets struct {
+	tail         *targets // rest of stack
+	_break       *BasicBlock
+	_continue    *BasicBlock
+	_fallthrough *BasicBlock
+}
+
+// Destinations associated with a labelled block.
+// We populate these as labels are encountered in forward gotos or
+// labelled statements.
+// Forward gotos are resolved once it is known which statement they
+// are associated with inside the Function.
+type lblock struct {
+	label     *types.Label // Label targeted by the blocks.
+	resolved  bool         // _goto block encountered (back jump or resolved fwd jump)
+	_goto     *BasicBlock
+	_break    *BasicBlock
+	_continue *BasicBlock
+}
+
+// label returns the symbol denoted by a label identifier.
+//
+// label should be a non-blank identifier (label.Name != "_").
+func (f *Function) label(label *ast.Ident) *types.Label {
+	return f.objectOf(label).(*types.Label)
+}
+
+// lblockOf returns the branch target associated with the
+// specified label, creating it if needed.
+func (f *Function) lblockOf(label *types.Label) *lblock {
+	lb := f.lblocks[label]
+	if lb == nil {
+		lb = &lblock{
+			label: label,
+			_goto: f.newBasicBlock(label.Name()),
+		}
+		if f.lblocks == nil {
+			f.lblocks = make(map[*types.Label]*lblock)
+		}
+		f.lblocks[label] = lb
+	}
+	return lb
+}
+
+// labelledBlock searches f for the block of the specified label.
+//
+// If f is a yield function, it additionally searches ancestor Functions
+// corresponding to enclosing range-over-func statements within the
+// same source function, so the returned block may belong to a different Function.
+func labelledBlock(f *Function, label *types.Label, tok token.Token) *BasicBlock {
+	if lb := f.lblocks[label]; lb != nil {
+		var block *BasicBlock
+		switch tok {
+		case token.BREAK:
+			block = lb._break
+		case token.CONTINUE:
+			block = lb._continue
+		case token.GOTO:
+			block = lb._goto
+		}
+		if block != nil {
+			return block
+		}
+	}
+	// Search ancestors if this is a yield function.
+	if f.jump != nil {
+		return labelledBlock(f.parent, label, tok)
+	}
+	return nil
+}
+
+// targetedBlock looks for the nearest block in f.targets
+// (and f's ancestors) that matches tok's type, and returns
+// the block and function it was found in.
+func targetedBlock(f *Function, tok token.Token) *BasicBlock {
+	if f == nil {
+		return nil
+	}
+	for t := f.targets; t != nil; t = t.tail {
+		var block *BasicBlock
+		switch tok {
+		case token.BREAK:
+			block = t._break
+		case token.CONTINUE:
+			block = t._continue
+		case token.FALLTHROUGH:
+			block = t._fallthrough
+		}
+		if block != nil {
+			return block
+		}
+	}
+	// Search f's ancestors (in case f is a yield function).
+	return targetedBlock(f.parent, tok)
+}
+
+// addResultVar adds a result for a variable v to f.results and v to f.returnVars.
+func (f *Function) addResultVar(v *types.Var) {
+	result := emitLocalVar(f, v)
+	f.results = append(f.results, result)
+	f.returnVars = append(f.returnVars, v)
+}
+
+// addParamVar adds a parameter to f.Params.
+func (f *Function) addParamVar(v *types.Var) *Parameter {
+	name := v.Name()
+	if name == "" {
+		name = fmt.Sprintf("arg%d", len(f.Params))
+	}
+	param := &Parameter{
+		name:   name,
+		object: v,
+		typ:    f.typ(v.Type()),
+		parent: f,
+	}
+	f.Params = append(f.Params, param)
+	return param
+}
+
+// addSpilledParam declares a parameter that is pre-spilled to the
+// stack; the function body will load/store the spilled location.
+// Subsequent lifting will eliminate spills where possible.
+func (f *Function) addSpilledParam(obj *types.Var) {
+	param := f.addParamVar(obj)
+	spill := emitLocalVar(f, obj)
+	f.emit(&Store{Addr: spill, Val: param})
+}
+
+// startBody initializes the function prior to generating SSA code for its body.
+// Precondition: f.Type() already set.
+func (f *Function) startBody() {
+	f.currentBlock = f.newBasicBlock("entry")
+	f.vars = make(map[*types.Var]Value) // needed for some synthetics, e.g. init
+}
+
+// createSyntacticParams populates f.Params and generates code (spills
+// and named result locals) for all the parameters declared in the
+// syntax.  In addition it populates the f.objects mapping.
+//
+// Preconditions:
+// f.startBody() was called. f.info != nil.
+// Postcondition:
+// len(f.Params) == len(f.Signature.Params) + (f.Signature.Recv() ? 1 : 0)
+func (f *Function) createSyntacticParams(recv *ast.FieldList, functype *ast.FuncType) {
+	// Receiver (at most one inner iteration).
+	if recv != nil {
+		for _, field := range recv.List {
+			for _, n := range field.Names {
+				f.addSpilledParam(identVar(f, n))
+			}
+			// Anonymous receiver?  No need to spill.
+			if field.Names == nil {
+				f.addParamVar(f.Signature.Recv())
+			}
+		}
+	}
+
+	// Parameters.
+	if functype.Params != nil {
+		n := len(f.Params) // 1 if has recv, 0 otherwise
+		for _, field := range functype.Params.List {
+			for _, n := range field.Names {
+				f.addSpilledParam(identVar(f, n))
+			}
+			// Anonymous parameter?  No need to spill.
+			if field.Names == nil {
+				f.addParamVar(f.Signature.Params().At(len(f.Params) - n))
+			}
+		}
+	}
+
+	// Results.
+	if functype.Results != nil {
+		for _, field := range functype.Results.List {
+			// Implicit "var" decl of locals for named results.
+			for _, n := range field.Names {
+				v := identVar(f, n)
+				f.addResultVar(v)
+			}
+			// Implicit "var" decl of local for an unnamed result.
+			if field.Names == nil {
+				v := f.Signature.Results().At(len(f.results))
+				f.addResultVar(v)
+			}
+		}
+	}
+}
+
+// createDeferStack initializes fn.deferstack to local variable
+// initialized to a ssa:deferstack() call.
+func (fn *Function) createDeferStack() {
+	// Each syntactic function makes a call to ssa:deferstack,
+	// which is spilled to a local. Unused ones are later removed.
+	fn.deferstack = newVar("defer$stack", tDeferStack)
+	call := &Call{Call: CallCommon{Value: vDeferStack}}
+	call.setType(tDeferStack)
+	deferstack := fn.emit(call)
+	spill := emitLocalVar(fn, fn.deferstack)
+	emitStore(fn, spill, deferstack, token.NoPos)
+}
+
+type setNumable interface {
+	setNum(int)
+}
+
+// numberRegisters assigns numbers to all SSA registers
+// (value-defining Instructions) in f, to aid debugging.
+// (Non-Instruction Values are named at construction.)
+func numberRegisters(f *Function) {
+	v := 0
+	for _, b := range f.Blocks {
+		for _, instr := range b.Instrs {
+			switch instr.(type) {
+			case Value:
+				instr.(setNumable).setNum(v)
+				v++
+			}
+		}
+	}
+}
+
+// buildReferrers populates the def/use information in all non-nil
+// Value.Referrers slice.
+// Precondition: all such slices are initially empty.
+func buildReferrers(f *Function) {
+	var rands []*Value
+	for _, b := range f.Blocks {
+		for _, instr := range b.Instrs {
+			rands = instr.Operands(rands[:0]) // recycle storage
+			for _, rand := range rands {
+				if r := *rand; r != nil {
+					if ref := r.Referrers(); ref != nil {
+						*ref = append(*ref, instr)
+					}
+				}
+			}
+		}
+	}
+}
+
+// finishBody() finalizes the contents of the function after SSA code generation of its body.
+//
+// The function is not done being built until done() is called.
+func (f *Function) finishBody() {
+	f.currentBlock = nil
+	f.lblocks = nil
+	f.returnVars = nil
+	f.jump = nil
+	f.source = nil
+	f.exits = nil
+
+	// Remove from f.Locals any Allocs that escape to the heap.
+	j := 0
+	for _, l := range f.Locals {
+		if !l.Heap {
+			f.Locals[j] = l
+			j++
+		}
+	}
+	// Nil out f.Locals[j:] to aid GC.
+	for i := j; i < len(f.Locals); i++ {
+		f.Locals[i] = nil
+	}
+	f.Locals = f.Locals[:j]
+
+	optimizeBlocks(f)
+
+	buildReferrers(f)
+
+	buildDomTree(f)
+
+	if f.Prog.mode&NaiveForm == 0 {
+		// For debugging pre-state of lifting pass:
+		// numberRegisters(f)
+		// f.WriteTo(os.Stderr)
+		lift(f)
+	}
+
+	// clear remaining builder state
+	f.results = nil    // (used by lifting)
+	f.deferstack = nil // (used by lifting)
+	f.vars = nil       // (used by lifting)
+	f.subst = nil
+
+	numberRegisters(f) // uses f.namedRegisters
+}
+
+// done marks the building of f's SSA body complete,
+// along with any nested functions, and optionally prints them.
+func (f *Function) done() {
+	assert(f.parent == nil, "done called on an anonymous function")
+
+	var visit func(*Function)
+	visit = func(f *Function) {
+		for _, anon := range f.AnonFuncs {
+			visit(anon) // anon is done building before f.
+		}
+
+		f.uniq = 0    // done with uniq
+		f.build = nil // function is built
+
+		if f.Prog.mode&PrintFunctions != 0 {
+			printMu.Lock()
+			f.WriteTo(os.Stdout)
+			printMu.Unlock()
+		}
+
+		if f.Prog.mode&SanityCheckFunctions != 0 {
+			mustSanityCheck(f, nil)
+		}
+	}
+	visit(f)
+}
+
+// removeNilBlocks eliminates nils from f.Blocks and updates each
+// BasicBlock.Index.  Use this after any pass that may delete blocks.
+func (f *Function) removeNilBlocks() {
+	j := 0
+	for _, b := range f.Blocks {
+		if b != nil {
+			b.Index = j
+			f.Blocks[j] = b
+			j++
+		}
+	}
+	// Nil out f.Blocks[j:] to aid GC.
+	for i := j; i < len(f.Blocks); i++ {
+		f.Blocks[i] = nil
+	}
+	f.Blocks = f.Blocks[:j]
+}
+
+// SetDebugMode sets the debug mode for package pkg.  If true, all its
+// functions will include full debug info.  This greatly increases the
+// size of the instruction stream, and causes Functions to depend upon
+// the ASTs, potentially keeping them live in memory for longer.
+func (pkg *Package) SetDebugMode(debug bool) {
+	pkg.debug = debug
+}
+
+// debugInfo reports whether debug info is wanted for this function.
+func (f *Function) debugInfo() bool {
+	// debug info for instantiations follows the debug info of their origin.
+	p := f.declaredPackage()
+	return p != nil && p.debug
+}
+
+// lookup returns the address of the named variable identified by obj
+// that is local to function f or one of its enclosing functions.
+// If escaping, the reference comes from a potentially escaping pointer
+// expression and the referent must be heap-allocated.
+// We assume the referent is a *Alloc or *Phi.
+// (The only Phis at this stage are those created directly by go1.22 "for" loops.)
+func (f *Function) lookup(obj *types.Var, escaping bool) Value {
+	if v, ok := f.vars[obj]; ok {
+		if escaping {
+			switch v := v.(type) {
+			case *Alloc:
+				v.Heap = true
+			case *Phi:
+				for _, edge := range v.Edges {
+					if alloc, ok := edge.(*Alloc); ok {
+						alloc.Heap = true
+					}
+				}
+			}
+		}
+		return v // function-local var (address)
+	}
+
+	// Definition must be in an enclosing function;
+	// plumb it through intervening closures.
+	if f.parent == nil {
+		panic("no ssa.Value for " + obj.String())
+	}
+	outer := f.parent.lookup(obj, true) // escaping
+	v := &FreeVar{
+		name:   obj.Name(),
+		typ:    outer.Type(),
+		pos:    outer.Pos(),
+		outer:  outer,
+		parent: f,
+	}
+	f.vars[obj] = v
+	f.FreeVars = append(f.FreeVars, v)
+	return v
+}
+
+// emit emits the specified instruction to function f.
+func (f *Function) emit(instr Instruction) Value {
+	return f.currentBlock.emit(instr)
+}
+
+// RelString returns the full name of this function, qualified by
+// package name, receiver type, etc.
+//
+// The specific formatting rules are not guaranteed and may change.
+//
+// Examples:
+//
+//	"math.IsNaN"                  // a package-level function
+//	"(*bytes.Buffer).Bytes"       // a declared method or a wrapper
+//	"(*bytes.Buffer).Bytes$thunk" // thunk (func wrapping method; receiver is param 0)
+//	"(*bytes.Buffer).Bytes$bound" // bound (func wrapping method; receiver supplied by closure)
+//	"main.main$1"                 // an anonymous function in main
+//	"main.init#1"                 // a declared init function
+//	"main.init"                   // the synthesized package initializer
+//
+// When these functions are referred to from within the same package
+// (i.e. from == f.Pkg.Object), they are rendered without the package path.
+// For example: "IsNaN", "(*Buffer).Bytes", etc.
+//
+// All non-synthetic functions have distinct package-qualified names.
+// (But two methods may have the same name "(T).f" if one is a synthetic
+// wrapper promoting a non-exported method "f" from another package; in
+// that case, the strings are equal but the identifiers "f" are distinct.)
+func (f *Function) RelString(from *types.Package) string {
+	// Anonymous?
+	if f.parent != nil {
+		// An anonymous function's Name() looks like "parentName$1",
+		// but its String() should include the type/package/etc.
+		parent := f.parent.RelString(from)
+		for i, anon := range f.parent.AnonFuncs {
+			if anon == f {
+				return fmt.Sprintf("%s$%d", parent, 1+i)
+			}
+		}
+
+		return f.name // should never happen
+	}
+
+	// Method (declared or wrapper)?
+	if recv := f.Signature.Recv(); recv != nil {
+		return f.relMethod(from, recv.Type())
+	}
+
+	// Thunk?
+	if f.method != nil {
+		return f.relMethod(from, f.method.recv)
+	}
+
+	// Bound?
+	if len(f.FreeVars) == 1 && strings.HasSuffix(f.name, "$bound") {
+		return f.relMethod(from, f.FreeVars[0].Type())
+	}
+
+	// Package-level function?
+	// Prefix with package name for cross-package references only.
+	if p := f.relPkg(); p != nil && p != from {
+		return fmt.Sprintf("%s.%s", p.Path(), f.name)
+	}
+
+	// Unknown.
+	return f.name
+}
+
+func (f *Function) relMethod(from *types.Package, recv types.Type) string {
+	return fmt.Sprintf("(%s).%s", relType(recv, from), f.name)
+}
+
+// writeSignature writes to buf the signature sig in declaration syntax.
+func writeSignature(buf *bytes.Buffer, from *types.Package, name string, sig *types.Signature) {
+	buf.WriteString("func ")
+	if recv := sig.Recv(); recv != nil {
+		buf.WriteString("(")
+		if name := recv.Name(); name != "" {
+			buf.WriteString(name)
+			buf.WriteString(" ")
+		}
+		types.WriteType(buf, recv.Type(), types.RelativeTo(from))
+		buf.WriteString(") ")
+	}
+	buf.WriteString(name)
+	types.WriteSignature(buf, sig, types.RelativeTo(from))
+}
+
+// declaredPackage returns the package fn is declared in or nil if the
+// function is not declared in a package.
+func (fn *Function) declaredPackage() *Package {
+	switch {
+	case fn.Pkg != nil:
+		return fn.Pkg // non-generic function  (does that follow??)
+	case fn.topLevelOrigin != nil:
+		return fn.topLevelOrigin.Pkg // instance of a named generic function
+	case fn.parent != nil:
+		return fn.parent.declaredPackage() // instance of an anonymous [generic] function
+	default:
+		return nil // function is not declared in a package, e.g. a wrapper.
+	}
+}
+
+// relPkg returns types.Package fn is printed in relationship to.
+func (fn *Function) relPkg() *types.Package {
+	if p := fn.declaredPackage(); p != nil {
+		return p.Pkg
+	}
+	return nil
+}
+
+var _ io.WriterTo = (*Function)(nil) // *Function implements io.Writer
+
+func (f *Function) WriteTo(w io.Writer) (int64, error) {
+	var buf bytes.Buffer
+	WriteFunction(&buf, f)
+	n, err := w.Write(buf.Bytes())
+	return int64(n), err
+}
+
+// WriteFunction writes to buf a human-readable "disassembly" of f.
+func WriteFunction(buf *bytes.Buffer, f *Function) {
+	fmt.Fprintf(buf, "# Name: %s\n", f.String())
+	if f.Pkg != nil {
+		fmt.Fprintf(buf, "# Package: %s\n", f.Pkg.Pkg.Path())
+	}
+	if syn := f.Synthetic; syn != "" {
+		fmt.Fprintln(buf, "# Synthetic:", syn)
+	}
+	if pos := f.Pos(); pos.IsValid() {
+		fmt.Fprintf(buf, "# Location: %s\n", f.Prog.Fset.Position(pos))
+	}
+
+	if f.parent != nil {
+		fmt.Fprintf(buf, "# Parent: %s\n", f.parent.Name())
+	}
+
+	if f.Recover != nil {
+		fmt.Fprintf(buf, "# Recover: %s\n", f.Recover)
+	}
+
+	from := f.relPkg()
+
+	if f.FreeVars != nil {
+		buf.WriteString("# Free variables:\n")
+		for i, fv := range f.FreeVars {
+			fmt.Fprintf(buf, "# % 3d:\t%s %s\n", i, fv.Name(), relType(fv.Type(), from))
+		}
+	}
+
+	if len(f.Locals) > 0 {
+		buf.WriteString("# Locals:\n")
+		for i, l := range f.Locals {
+			fmt.Fprintf(buf, "# % 3d:\t%s %s\n", i, l.Name(), relType(typeparams.MustDeref(l.Type()), from))
+		}
+	}
+	writeSignature(buf, from, f.Name(), f.Signature)
+	buf.WriteString(":\n")
+
+	if f.Blocks == nil {
+		buf.WriteString("\t(external)\n")
+	}
+
+	// NB. column calculations are confused by non-ASCII
+	// characters and assume 8-space tabs.
+	const punchcard = 80 // for old time's sake.
+	const tabwidth = 8
+	for _, b := range f.Blocks {
+		if b == nil {
+			// Corrupt CFG.
+			fmt.Fprintf(buf, ".nil:\n")
+			continue
+		}
+		n, _ := fmt.Fprintf(buf, "%d:", b.Index)
+		bmsg := fmt.Sprintf("%s P:%d S:%d", b.Comment, len(b.Preds), len(b.Succs))
+		fmt.Fprintf(buf, "%*s%s\n", punchcard-1-n-len(bmsg), "", bmsg)
+
+		if false { // CFG debugging
+			fmt.Fprintf(buf, "\t# CFG: %s --> %s --> %s\n", b.Preds, b, b.Succs)
+		}
+		for _, instr := range b.Instrs {
+			buf.WriteString("\t")
+			switch v := instr.(type) {
+			case Value:
+				l := punchcard - tabwidth
+				// Left-align the instruction.
+				if name := v.Name(); name != "" {
+					n, _ := fmt.Fprintf(buf, "%s = ", name)
+					l -= n
+				}
+				n, _ := buf.WriteString(instr.String())
+				l -= n
+				// Right-align the type if there's space.
+				if t := v.Type(); t != nil {
+					buf.WriteByte(' ')
+					ts := relType(t, from)
+					l -= len(ts) + len("  ") // (spaces before and after type)
+					if l > 0 {
+						fmt.Fprintf(buf, "%*s", l, "")
+					}
+					buf.WriteString(ts)
+				}
+			case nil:
+				// Be robust against bad transforms.
+				buf.WriteString("<deleted>")
+			default:
+				buf.WriteString(instr.String())
+			}
+			// -mode=S: show line numbers
+			if f.Prog.mode&LogSource != 0 {
+				if pos := instr.Pos(); pos.IsValid() {
+					fmt.Fprintf(buf, " L%d", f.Prog.Fset.Position(pos).Line)
+				}
+			}
+			buf.WriteString("\n")
+		}
+	}
+	fmt.Fprintf(buf, "\n")
+}
+
+// newBasicBlock adds to f a new basic block and returns it.  It does
+// not automatically become the current block for subsequent calls to emit.
+// comment is an optional string for more readable debugging output.
+func (f *Function) newBasicBlock(comment string) *BasicBlock {
+	b := &BasicBlock{
+		Index:   len(f.Blocks),
+		Comment: comment,
+		parent:  f,
+	}
+	b.Succs = b.succs2[:0]
+	f.Blocks = append(f.Blocks, b)
+	return b
+}
+
+// NewFunction returns a new synthetic Function instance belonging to
+// prog, with its name and signature fields set as specified.
+//
+// The caller is responsible for initializing the remaining fields of
+// the function object, e.g. Pkg, Params, Blocks.
+//
+// It is practically impossible for clients to construct well-formed
+// SSA functions/packages/programs directly, so we assume this is the
+// job of the Builder alone.  NewFunction exists to provide clients a
+// little flexibility.  For example, analysis tools may wish to
+// construct fake Functions for the root of the callgraph, a fake
+// "reflect" package, etc.
+//
+// TODO(adonovan): think harder about the API here.
+func (prog *Program) NewFunction(name string, sig *types.Signature, provenance string) *Function {
+	return &Function{Prog: prog, name: name, Signature: sig, Synthetic: provenance}
+}
+
+// Syntax returns the function's syntax (*ast.Func{Decl,Lit})
+// if it was produced from syntax or an *ast.RangeStmt if
+// it is a range-over-func yield function.
+func (f *Function) Syntax() ast.Node { return f.syntax }
+
+// identVar returns the variable defined by id.
+func identVar(fn *Function, id *ast.Ident) *types.Var {
+	return fn.info.Defs[id].(*types.Var)
+}
+
+// unique returns a unique positive int within the source tree of f.
+// The source tree of f includes all of f's ancestors by parent and all
+// of the AnonFuncs contained within these.
+func unique(f *Function) int64 {
+	f.uniq++
+	return f.uniq
+}
+
+// exit is a change of control flow going from a range-over-func
+// yield function to an ancestor function caused by a break, continue,
+// goto, or return statement.
+//
+// There are 3 types of exits:
+// * return from the source function (from ReturnStmt),
+// * jump to a block (from break and continue statements [labelled/unlabelled]),
+// * go to a label (from goto statements).
+//
+// As the builder does one pass over the ast, it is unclear whether
+// a forward goto statement will leave a range-over-func body.
+// The function being exited to is unresolved until the end
+// of building the range-over-func body.
+type exit struct {
+	id   int64     // unique value for exit within from and to
+	from *Function // the function the exit starts from
+	to   *Function // the function being exited to (nil if unresolved)
+	pos  token.Pos
+
+	block *BasicBlock  // basic block within to being jumped to.
+	label *types.Label // forward label being jumped to via goto.
+	// block == nil && label == nil => return
+}
+
+// storeVar emits to function f code to store a value v to a *types.Var x.
+func storeVar(f *Function, x *types.Var, v Value, pos token.Pos) {
+	emitStore(f, f.lookup(x, true), v, pos)
+}
+
+// labelExit creates a new exit to a yield fn to exit the function using a label.
+func labelExit(fn *Function, label *types.Label, pos token.Pos) *exit {
+	e := &exit{
+		id:    unique(fn),
+		from:  fn,
+		to:    nil,
+		pos:   pos,
+		label: label,
+	}
+	fn.exits = append(fn.exits, e)
+	return e
+}
+
+// blockExit creates a new exit to a yield fn that jumps to a basic block.
+func blockExit(fn *Function, block *BasicBlock, pos token.Pos) *exit {
+	e := &exit{
+		id:    unique(fn),
+		from:  fn,
+		to:    block.parent,
+		pos:   pos,
+		block: block,
+	}
+	fn.exits = append(fn.exits, e)
+	return e
+}
+
+// blockExit creates a new exit to a yield fn that returns the source function.
+func returnExit(fn *Function, pos token.Pos) *exit {
+	e := &exit{
+		id:   unique(fn),
+		from: fn,
+		to:   fn.source,
+		pos:  pos,
+	}
+	fn.exits = append(fn.exits, e)
+	return e
+}
diff --git a/vendor/golang.org/x/tools/go/ssa/instantiate.go b/vendor/golang.org/x/tools/go/ssa/instantiate.go
new file mode 100644
index 0000000..2512f32
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ssa/instantiate.go
@@ -0,0 +1,131 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+import (
+	"fmt"
+	"go/types"
+	"sync"
+)
+
+// A generic records information about a generic origin function,
+// including a cache of existing instantiations.
+type generic struct {
+	instancesMu sync.Mutex
+	instances   map[*typeList]*Function // canonical type arguments to an instance.
+}
+
+// instance returns a Function that is the instantiation of generic
+// origin function fn with the type arguments targs.
+//
+// Any created instance is added to cr.
+//
+// Acquires fn.generic.instancesMu.
+func (fn *Function) instance(targs []types.Type, b *builder) *Function {
+	key := fn.Prog.canon.List(targs)
+
+	gen := fn.generic
+
+	gen.instancesMu.Lock()
+	defer gen.instancesMu.Unlock()
+	inst, ok := gen.instances[key]
+	if !ok {
+		inst = createInstance(fn, targs)
+		inst.buildshared = b.shared()
+		b.enqueue(inst)
+
+		if gen.instances == nil {
+			gen.instances = make(map[*typeList]*Function)
+		}
+		gen.instances[key] = inst
+	} else {
+		b.waitForSharedFunction(inst)
+	}
+	return inst
+}
+
+// createInstance returns the instantiation of generic function fn using targs.
+//
+// Requires fn.generic.instancesMu.
+func createInstance(fn *Function, targs []types.Type) *Function {
+	prog := fn.Prog
+
+	// Compute signature.
+	var sig *types.Signature
+	var obj *types.Func
+	if recv := fn.Signature.Recv(); recv != nil {
+		// method
+		obj = prog.canon.instantiateMethod(fn.object, targs, prog.ctxt)
+		sig = obj.Type().(*types.Signature)
+	} else {
+		// function
+		instSig, err := types.Instantiate(prog.ctxt, fn.Signature, targs, false)
+		if err != nil {
+			panic(err)
+		}
+		instance, ok := instSig.(*types.Signature)
+		if !ok {
+			panic("Instantiate of a Signature returned a non-signature")
+		}
+		obj = fn.object // instantiation does not exist yet
+		sig = prog.canon.Type(instance).(*types.Signature)
+	}
+
+	// Choose strategy (instance or wrapper).
+	var (
+		synthetic string
+		subst     *subster
+		build     buildFunc
+	)
+	if prog.mode&InstantiateGenerics != 0 && !prog.isParameterized(targs...) {
+		synthetic = fmt.Sprintf("instance of %s", fn.Name())
+		if fn.syntax != nil {
+			subst = makeSubster(prog.ctxt, obj, fn.typeparams, targs, false)
+			build = (*builder).buildFromSyntax
+		} else {
+			build = (*builder).buildParamsOnly
+		}
+	} else {
+		synthetic = fmt.Sprintf("instantiation wrapper of %s", fn.Name())
+		build = (*builder).buildInstantiationWrapper
+	}
+
+	/* generic instance or instantiation wrapper */
+	return &Function{
+		name:           fmt.Sprintf("%s%s", fn.Name(), targs), // may not be unique
+		object:         obj,
+		Signature:      sig,
+		Synthetic:      synthetic,
+		syntax:         fn.syntax,    // \
+		info:           fn.info,      //  } empty for non-created packages
+		goversion:      fn.goversion, // /
+		build:          build,
+		topLevelOrigin: fn,
+		pos:            obj.Pos(),
+		Pkg:            nil,
+		Prog:           fn.Prog,
+		typeparams:     fn.typeparams, // share with origin
+		typeargs:       targs,
+		subst:          subst,
+	}
+}
+
+// isParameterized reports whether any of the specified types contains
+// a free type parameter. It is safe to call concurrently.
+func (prog *Program) isParameterized(ts ...types.Type) bool {
+	prog.hasParamsMu.Lock()
+	defer prog.hasParamsMu.Unlock()
+
+	// TODO(adonovan): profile. If this operation is expensive,
+	// handle the most common but shallow cases such as T, pkg.T,
+	// *T without consulting the cache under the lock.
+
+	for _, t := range ts {
+		if prog.hasParams.Has(t) {
+			return true
+		}
+	}
+	return false
+}
diff --git a/vendor/golang.org/x/tools/go/ssa/lift.go b/vendor/golang.org/x/tools/go/ssa/lift.go
new file mode 100644
index 0000000..aada3dc
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ssa/lift.go
@@ -0,0 +1,688 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// This file defines the lifting pass which tries to "lift" Alloc
+// cells (new/local variables) into SSA registers, replacing loads
+// with the dominating stored value, eliminating loads and stores, and
+// inserting φ-nodes as needed.
+
+// Cited papers and resources:
+//
+// Ron Cytron et al. 1991. Efficiently computing SSA form...
+// http://doi.acm.org/10.1145/115372.115320
+//
+// Cooper, Harvey, Kennedy.  2001.  A Simple, Fast Dominance Algorithm.
+// Software Practice and Experience 2001, 4:1-10.
+// http://www.hipersoft.rice.edu/grads/publications/dom14.pdf
+//
+// Daniel Berlin, llvmdev mailing list, 2012.
+// http://lists.cs.uiuc.edu/pipermail/llvmdev/2012-January/046638.html
+// (Be sure to expand the whole thread.)
+
+// TODO(adonovan): opt: there are many optimizations worth evaluating, and
+// the conventional wisdom for SSA construction is that a simple
+// algorithm well engineered often beats those of better asymptotic
+// complexity on all but the most egregious inputs.
+//
+// Danny Berlin suggests that the Cooper et al. algorithm for
+// computing the dominance frontier is superior to Cytron et al.
+// Furthermore he recommends that rather than computing the DF for the
+// whole function then renaming all alloc cells, it may be cheaper to
+// compute the DF for each alloc cell separately and throw it away.
+//
+// Consider exploiting liveness information to avoid creating dead
+// φ-nodes which we then immediately remove.
+//
+// Also see many other "TODO: opt" suggestions in the code.
+
+import (
+	"fmt"
+	"go/token"
+	"math/big"
+	"os"
+
+	"golang.org/x/tools/internal/typeparams"
+)
+
+// If true, show diagnostic information at each step of lifting.
+// Very verbose.
+const debugLifting = false
+
+// domFrontier maps each block to the set of blocks in its dominance
+// frontier.  The outer slice is conceptually a map keyed by
+// Block.Index.  The inner slice is conceptually a set, possibly
+// containing duplicates.
+//
+// TODO(adonovan): opt: measure impact of dups; consider a packed bit
+// representation, e.g. big.Int, and bitwise parallel operations for
+// the union step in the Children loop.
+//
+// domFrontier's methods mutate the slice's elements but not its
+// length, so their receivers needn't be pointers.
+type domFrontier [][]*BasicBlock
+
+func (df domFrontier) add(u, v *BasicBlock) {
+	p := &df[u.Index]
+	*p = append(*p, v)
+}
+
+// build builds the dominance frontier df for the dominator (sub)tree
+// rooted at u, using the Cytron et al. algorithm.
+//
+// TODO(adonovan): opt: consider Berlin approach, computing pruned SSA
+// by pruning the entire IDF computation, rather than merely pruning
+// the DF -> IDF step.
+func (df domFrontier) build(u *BasicBlock) {
+	// Encounter each node u in postorder of dom tree.
+	for _, child := range u.dom.children {
+		df.build(child)
+	}
+	for _, vb := range u.Succs {
+		if v := vb.dom; v.idom != u {
+			df.add(u, vb)
+		}
+	}
+	for _, w := range u.dom.children {
+		for _, vb := range df[w.Index] {
+			// TODO(adonovan): opt: use word-parallel bitwise union.
+			if v := vb.dom; v.idom != u {
+				df.add(u, vb)
+			}
+		}
+	}
+}
+
+func buildDomFrontier(fn *Function) domFrontier {
+	df := make(domFrontier, len(fn.Blocks))
+	df.build(fn.Blocks[0])
+	if fn.Recover != nil {
+		df.build(fn.Recover)
+	}
+	return df
+}
+
+func removeInstr(refs []Instruction, instr Instruction) []Instruction {
+	return removeInstrsIf(refs, func(i Instruction) bool { return i == instr })
+}
+
+func removeInstrsIf(refs []Instruction, p func(Instruction) bool) []Instruction {
+	// TODO(taking): replace with go1.22 slices.DeleteFunc.
+	i := 0
+	for _, ref := range refs {
+		if p(ref) {
+			continue
+		}
+		refs[i] = ref
+		i++
+	}
+	for j := i; j != len(refs); j++ {
+		refs[j] = nil // aid GC
+	}
+	return refs[:i]
+}
+
+// lift replaces local and new Allocs accessed only with
+// load/store by SSA registers, inserting φ-nodes where necessary.
+// The result is a program in classical pruned SSA form.
+//
+// Preconditions:
+// - fn has no dead blocks (blockopt has run).
+// - Def/use info (Operands and Referrers) is up-to-date.
+// - The dominator tree is up-to-date.
+func lift(fn *Function) {
+	// TODO(adonovan): opt: lots of little optimizations may be
+	// worthwhile here, especially if they cause us to avoid
+	// buildDomFrontier.  For example:
+	//
+	// - Alloc never loaded?  Eliminate.
+	// - Alloc never stored?  Replace all loads with a zero constant.
+	// - Alloc stored once?  Replace loads with dominating store;
+	//   don't forget that an Alloc is itself an effective store
+	//   of zero.
+	// - Alloc used only within a single block?
+	//   Use degenerate algorithm avoiding φ-nodes.
+	// - Consider synergy with scalar replacement of aggregates (SRA).
+	//   e.g. *(&x.f) where x is an Alloc.
+	//   Perhaps we'd get better results if we generated this as x.f
+	//   i.e. Field(x, .f) instead of Load(FieldIndex(x, .f)).
+	//   Unclear.
+	//
+	// But we will start with the simplest correct code.
+	df := buildDomFrontier(fn)
+
+	if debugLifting {
+		title := false
+		for i, blocks := range df {
+			if blocks != nil {
+				if !title {
+					fmt.Fprintf(os.Stderr, "Dominance frontier of %s:\n", fn)
+					title = true
+				}
+				fmt.Fprintf(os.Stderr, "\t%s: %s\n", fn.Blocks[i], blocks)
+			}
+		}
+	}
+
+	newPhis := make(newPhiMap)
+
+	// During this pass we will replace some BasicBlock.Instrs
+	// (allocs, loads and stores) with nil, keeping a count in
+	// BasicBlock.gaps.  At the end we will reset Instrs to the
+	// concatenation of all non-dead newPhis and non-nil Instrs
+	// for the block, reusing the original array if space permits.
+
+	// While we're here, we also eliminate 'rundefers'
+	// instructions and ssa:deferstack() in functions that contain no
+	// 'defer' instructions. For now, we also eliminate
+	// 's = ssa:deferstack()' calls if s doesn't escape, replacing s
+	// with nil in Defer{DeferStack: s}. This has the same meaning,
+	// but allows eliminating the intrinsic function `ssa:deferstack()`
+	// (unless it is needed due to range-over-func instances). This gives
+	// ssa users more time to support range-over-func.
+	usesDefer := false
+	deferstackAlloc, deferstackCall := deferstackPreamble(fn)
+	eliminateDeferStack := deferstackAlloc != nil && !deferstackAlloc.Heap
+
+	// A counter used to generate ~unique ids for Phi nodes, as an
+	// aid to debugging.  We use large numbers to make them highly
+	// visible.  All nodes are renumbered later.
+	fresh := 1000
+
+	// Determine which allocs we can lift and number them densely.
+	// The renaming phase uses this numbering for compact maps.
+	numAllocs := 0
+	for _, b := range fn.Blocks {
+		b.gaps = 0
+		b.rundefers = 0
+		for _, instr := range b.Instrs {
+			switch instr := instr.(type) {
+			case *Alloc:
+				index := -1
+				if liftAlloc(df, instr, newPhis, &fresh) {
+					index = numAllocs
+					numAllocs++
+				}
+				instr.index = index
+			case *Defer:
+				usesDefer = true
+				if eliminateDeferStack {
+					// Clear DeferStack and remove references to loads
+					if instr.DeferStack != nil {
+						if refs := instr.DeferStack.Referrers(); refs != nil {
+							*refs = removeInstr(*refs, instr)
+						}
+						instr.DeferStack = nil
+					}
+				}
+			case *RunDefers:
+				b.rundefers++
+			}
+		}
+	}
+
+	// renaming maps an alloc (keyed by index) to its replacement
+	// value.  Initially the renaming contains nil, signifying the
+	// zero constant of the appropriate type; we construct the
+	// Const lazily at most once on each path through the domtree.
+	// TODO(adonovan): opt: cache per-function not per subtree.
+	renaming := make([]Value, numAllocs)
+
+	// Renaming.
+	rename(fn.Blocks[0], renaming, newPhis)
+
+	// Eliminate dead φ-nodes.
+	removeDeadPhis(fn.Blocks, newPhis)
+
+	// Eliminate ssa:deferstack() call.
+	if eliminateDeferStack {
+		b := deferstackCall.block
+		for i, instr := range b.Instrs {
+			if instr == deferstackCall {
+				b.Instrs[i] = nil
+				b.gaps++
+				break
+			}
+		}
+	}
+
+	// Prepend remaining live φ-nodes to each block.
+	for _, b := range fn.Blocks {
+		nps := newPhis[b]
+		j := len(nps)
+
+		rundefersToKill := b.rundefers
+		if usesDefer {
+			rundefersToKill = 0
+		}
+
+		if j+b.gaps+rundefersToKill == 0 {
+			continue // fast path: no new phis or gaps
+		}
+
+		// Compact nps + non-nil Instrs into a new slice.
+		// TODO(adonovan): opt: compact in situ (rightwards)
+		// if Instrs has sufficient space or slack.
+		dst := make([]Instruction, len(b.Instrs)+j-b.gaps-rundefersToKill)
+		for i, np := range nps {
+			dst[i] = np.phi
+		}
+		for _, instr := range b.Instrs {
+			if instr == nil {
+				continue
+			}
+			if !usesDefer {
+				if _, ok := instr.(*RunDefers); ok {
+					continue
+				}
+			}
+			dst[j] = instr
+			j++
+		}
+		b.Instrs = dst
+	}
+
+	// Remove any fn.Locals that were lifted.
+	j := 0
+	for _, l := range fn.Locals {
+		if l.index < 0 {
+			fn.Locals[j] = l
+			j++
+		}
+	}
+	// Nil out fn.Locals[j:] to aid GC.
+	for i := j; i < len(fn.Locals); i++ {
+		fn.Locals[i] = nil
+	}
+	fn.Locals = fn.Locals[:j]
+}
+
+// removeDeadPhis removes φ-nodes not transitively needed by a
+// non-Phi, non-DebugRef instruction.
+func removeDeadPhis(blocks []*BasicBlock, newPhis newPhiMap) {
+	// First pass: find the set of "live" φ-nodes: those reachable
+	// from some non-Phi instruction.
+	//
+	// We compute reachability in reverse, starting from each φ,
+	// rather than forwards, starting from each live non-Phi
+	// instruction, because this way visits much less of the
+	// Value graph.
+	livePhis := make(map[*Phi]bool)
+	for _, npList := range newPhis {
+		for _, np := range npList {
+			phi := np.phi
+			if !livePhis[phi] && phiHasDirectReferrer(phi) {
+				markLivePhi(livePhis, phi)
+			}
+		}
+	}
+
+	// Existing φ-nodes due to && and || operators
+	// are all considered live (see Go issue 19622).
+	for _, b := range blocks {
+		for _, phi := range b.phis() {
+			markLivePhi(livePhis, phi.(*Phi))
+		}
+	}
+
+	// Second pass: eliminate unused phis from newPhis.
+	for block, npList := range newPhis {
+		j := 0
+		for _, np := range npList {
+			if livePhis[np.phi] {
+				npList[j] = np
+				j++
+			} else {
+				// discard it, first removing it from referrers
+				for _, val := range np.phi.Edges {
+					if refs := val.Referrers(); refs != nil {
+						*refs = removeInstr(*refs, np.phi)
+					}
+				}
+				np.phi.block = nil
+			}
+		}
+		newPhis[block] = npList[:j]
+	}
+}
+
+// markLivePhi marks phi, and all φ-nodes transitively reachable via
+// its Operands, live.
+func markLivePhi(livePhis map[*Phi]bool, phi *Phi) {
+	livePhis[phi] = true
+	for _, rand := range phi.Operands(nil) {
+		if q, ok := (*rand).(*Phi); ok {
+			if !livePhis[q] {
+				markLivePhi(livePhis, q)
+			}
+		}
+	}
+}
+
+// phiHasDirectReferrer reports whether phi is directly referred to by
+// a non-Phi instruction.  Such instructions are the
+// roots of the liveness traversal.
+func phiHasDirectReferrer(phi *Phi) bool {
+	for _, instr := range *phi.Referrers() {
+		if _, ok := instr.(*Phi); !ok {
+			return true
+		}
+	}
+	return false
+}
+
+type blockSet struct{ big.Int } // (inherit methods from Int)
+
+// add adds b to the set and returns true if the set changed.
+func (s *blockSet) add(b *BasicBlock) bool {
+	i := b.Index
+	if s.Bit(i) != 0 {
+		return false
+	}
+	s.SetBit(&s.Int, i, 1)
+	return true
+}
+
+// take removes an arbitrary element from a set s and
+// returns its index, or returns -1 if empty.
+func (s *blockSet) take() int {
+	l := s.BitLen()
+	for i := 0; i < l; i++ {
+		if s.Bit(i) == 1 {
+			s.SetBit(&s.Int, i, 0)
+			return i
+		}
+	}
+	return -1
+}
+
+// newPhi is a pair of a newly introduced φ-node and the lifted Alloc
+// it replaces.
+type newPhi struct {
+	phi   *Phi
+	alloc *Alloc
+}
+
+// newPhiMap records for each basic block, the set of newPhis that
+// must be prepended to the block.
+type newPhiMap map[*BasicBlock][]newPhi
+
+// liftAlloc determines whether alloc can be lifted into registers,
+// and if so, it populates newPhis with all the φ-nodes it may require
+// and returns true.
+//
+// fresh is a source of fresh ids for phi nodes.
+func liftAlloc(df domFrontier, alloc *Alloc, newPhis newPhiMap, fresh *int) bool {
+	// Don't lift result values in functions that defer
+	// calls that may recover from panic.
+	if fn := alloc.Parent(); fn.Recover != nil {
+		for _, nr := range fn.results {
+			if nr == alloc {
+				return false
+			}
+		}
+	}
+
+	// Compute defblocks, the set of blocks containing a
+	// definition of the alloc cell.
+	var defblocks blockSet
+	for _, instr := range *alloc.Referrers() {
+		// Bail out if we discover the alloc is not liftable;
+		// the only operations permitted to use the alloc are
+		// loads/stores into the cell, and DebugRef.
+		switch instr := instr.(type) {
+		case *Store:
+			if instr.Val == alloc {
+				return false // address used as value
+			}
+			if instr.Addr != alloc {
+				panic("Alloc.Referrers is inconsistent")
+			}
+			defblocks.add(instr.Block())
+		case *UnOp:
+			if instr.Op != token.MUL {
+				return false // not a load
+			}
+			if instr.X != alloc {
+				panic("Alloc.Referrers is inconsistent")
+			}
+		case *DebugRef:
+			// ok
+		default:
+			return false // some other instruction
+		}
+	}
+	// The Alloc itself counts as a (zero) definition of the cell.
+	defblocks.add(alloc.Block())
+
+	if debugLifting {
+		fmt.Fprintln(os.Stderr, "\tlifting ", alloc, alloc.Name())
+	}
+
+	fn := alloc.Parent()
+
+	// Φ-insertion.
+	//
+	// What follows is the body of the main loop of the insert-φ
+	// function described by Cytron et al, but instead of using
+	// counter tricks, we just reset the 'hasAlready' and 'work'
+	// sets each iteration.  These are bitmaps so it's pretty cheap.
+	//
+	// TODO(adonovan): opt: recycle slice storage for W,
+	// hasAlready, defBlocks across liftAlloc calls.
+	var hasAlready blockSet
+
+	// Initialize W and work to defblocks.
+	var work blockSet = defblocks // blocks seen
+	var W blockSet                // blocks to do
+	W.Set(&defblocks.Int)
+
+	// Traverse iterated dominance frontier, inserting φ-nodes.
+	for i := W.take(); i != -1; i = W.take() {
+		u := fn.Blocks[i]
+		for _, v := range df[u.Index] {
+			if hasAlready.add(v) {
+				// Create φ-node.
+				// It will be prepended to v.Instrs later, if needed.
+				phi := &Phi{
+					Edges:   make([]Value, len(v.Preds)),
+					Comment: alloc.Comment,
+				}
+				// This is merely a debugging aid:
+				phi.setNum(*fresh)
+				*fresh++
+
+				phi.pos = alloc.Pos()
+				phi.setType(typeparams.MustDeref(alloc.Type()))
+				phi.block = v
+				if debugLifting {
+					fmt.Fprintf(os.Stderr, "\tplace %s = %s at block %s\n", phi.Name(), phi, v)
+				}
+				newPhis[v] = append(newPhis[v], newPhi{phi, alloc})
+
+				if work.add(v) {
+					W.add(v)
+				}
+			}
+		}
+	}
+
+	return true
+}
+
+// replaceAll replaces all intraprocedural uses of x with y,
+// updating x.Referrers and y.Referrers.
+// Precondition: x.Referrers() != nil, i.e. x must be local to some function.
+func replaceAll(x, y Value) {
+	var rands []*Value
+	pxrefs := x.Referrers()
+	pyrefs := y.Referrers()
+	for _, instr := range *pxrefs {
+		rands = instr.Operands(rands[:0]) // recycle storage
+		for _, rand := range rands {
+			if *rand != nil {
+				if *rand == x {
+					*rand = y
+				}
+			}
+		}
+		if pyrefs != nil {
+			*pyrefs = append(*pyrefs, instr) // dups ok
+		}
+	}
+	*pxrefs = nil // x is now unreferenced
+}
+
+// renamed returns the value to which alloc is being renamed,
+// constructing it lazily if it's the implicit zero initialization.
+func renamed(renaming []Value, alloc *Alloc) Value {
+	v := renaming[alloc.index]
+	if v == nil {
+		v = zeroConst(typeparams.MustDeref(alloc.Type()))
+		renaming[alloc.index] = v
+	}
+	return v
+}
+
+// rename implements the (Cytron et al) SSA renaming algorithm, a
+// preorder traversal of the dominator tree replacing all loads of
+// Alloc cells with the value stored to that cell by the dominating
+// store instruction.  For lifting, we need only consider loads,
+// stores and φ-nodes.
+//
+// renaming is a map from *Alloc (keyed by index number) to its
+// dominating stored value; newPhis[x] is the set of new φ-nodes to be
+// prepended to block x.
+func rename(u *BasicBlock, renaming []Value, newPhis newPhiMap) {
+	// Each φ-node becomes the new name for its associated Alloc.
+	for _, np := range newPhis[u] {
+		phi := np.phi
+		alloc := np.alloc
+		renaming[alloc.index] = phi
+	}
+
+	// Rename loads and stores of allocs.
+	for i, instr := range u.Instrs {
+		switch instr := instr.(type) {
+		case *Alloc:
+			if instr.index >= 0 { // store of zero to Alloc cell
+				// Replace dominated loads by the zero value.
+				renaming[instr.index] = nil
+				if debugLifting {
+					fmt.Fprintf(os.Stderr, "\tkill alloc %s\n", instr)
+				}
+				// Delete the Alloc.
+				u.Instrs[i] = nil
+				u.gaps++
+			}
+
+		case *Store:
+			if alloc, ok := instr.Addr.(*Alloc); ok && alloc.index >= 0 { // store to Alloc cell
+				// Replace dominated loads by the stored value.
+				renaming[alloc.index] = instr.Val
+				if debugLifting {
+					fmt.Fprintf(os.Stderr, "\tkill store %s; new value: %s\n",
+						instr, instr.Val.Name())
+				}
+				// Remove the store from the referrer list of the stored value.
+				if refs := instr.Val.Referrers(); refs != nil {
+					*refs = removeInstr(*refs, instr)
+				}
+				// Delete the Store.
+				u.Instrs[i] = nil
+				u.gaps++
+			}
+
+		case *UnOp:
+			if instr.Op == token.MUL {
+				if alloc, ok := instr.X.(*Alloc); ok && alloc.index >= 0 { // load of Alloc cell
+					newval := renamed(renaming, alloc)
+					if debugLifting {
+						fmt.Fprintf(os.Stderr, "\tupdate load %s = %s with %s\n",
+							instr.Name(), instr, newval.Name())
+					}
+					// Replace all references to
+					// the loaded value by the
+					// dominating stored value.
+					replaceAll(instr, newval)
+					// Delete the Load.
+					u.Instrs[i] = nil
+					u.gaps++
+				}
+			}
+
+		case *DebugRef:
+			if alloc, ok := instr.X.(*Alloc); ok && alloc.index >= 0 { // ref of Alloc cell
+				if instr.IsAddr {
+					instr.X = renamed(renaming, alloc)
+					instr.IsAddr = false
+
+					// Add DebugRef to instr.X's referrers.
+					if refs := instr.X.Referrers(); refs != nil {
+						*refs = append(*refs, instr)
+					}
+				} else {
+					// A source expression denotes the address
+					// of an Alloc that was optimized away.
+					instr.X = nil
+
+					// Delete the DebugRef.
+					u.Instrs[i] = nil
+					u.gaps++
+				}
+			}
+		}
+	}
+
+	// For each φ-node in a CFG successor, rename the edge.
+	for _, v := range u.Succs {
+		phis := newPhis[v]
+		if len(phis) == 0 {
+			continue
+		}
+		i := v.predIndex(u)
+		for _, np := range phis {
+			phi := np.phi
+			alloc := np.alloc
+			newval := renamed(renaming, alloc)
+			if debugLifting {
+				fmt.Fprintf(os.Stderr, "\tsetphi %s edge %s -> %s (#%d) (alloc=%s) := %s\n",
+					phi.Name(), u, v, i, alloc.Name(), newval.Name())
+			}
+			phi.Edges[i] = newval
+			if prefs := newval.Referrers(); prefs != nil {
+				*prefs = append(*prefs, phi)
+			}
+		}
+	}
+
+	// Continue depth-first recursion over domtree, pushing a
+	// fresh copy of the renaming map for each subtree.
+	for i, v := range u.dom.children {
+		r := renaming
+		if i < len(u.dom.children)-1 {
+			// On all but the final iteration, we must make
+			// a copy to avoid destructive update.
+			r = make([]Value, len(renaming))
+			copy(r, renaming)
+		}
+		rename(v, r, newPhis)
+	}
+
+}
+
+// deferstackPreamble returns the *Alloc and ssa:deferstack() call for fn.deferstack.
+func deferstackPreamble(fn *Function) (*Alloc, *Call) {
+	if alloc, _ := fn.vars[fn.deferstack].(*Alloc); alloc != nil {
+		for _, ref := range *alloc.Referrers() {
+			if ref, _ := ref.(*Store); ref != nil && ref.Addr == alloc {
+				if call, _ := ref.Val.(*Call); call != nil {
+					return alloc, call
+				}
+			}
+		}
+	}
+	return nil, nil
+}
diff --git a/vendor/golang.org/x/tools/go/ssa/lvalue.go b/vendor/golang.org/x/tools/go/ssa/lvalue.go
new file mode 100644
index 0000000..eede307
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ssa/lvalue.go
@@ -0,0 +1,155 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// lvalues are the union of addressable expressions and map-index
+// expressions.
+
+import (
+	"go/ast"
+	"go/token"
+	"go/types"
+
+	"golang.org/x/tools/internal/typeparams"
+)
+
+// An lvalue represents an assignable location that may appear on the
+// left-hand side of an assignment.  This is a generalization of a
+// pointer to permit updates to elements of maps.
+type lvalue interface {
+	store(fn *Function, v Value) // stores v into the location
+	load(fn *Function) Value     // loads the contents of the location
+	address(fn *Function) Value  // address of the location
+	typ() types.Type             // returns the type of the location
+}
+
+// An address is an lvalue represented by a true pointer.
+type address struct {
+	addr Value     // must have a pointer core type.
+	pos  token.Pos // source position
+	expr ast.Expr  // source syntax of the value (not address) [debug mode]
+}
+
+func (a *address) load(fn *Function) Value {
+	load := emitLoad(fn, a.addr)
+	load.pos = a.pos
+	return load
+}
+
+func (a *address) store(fn *Function, v Value) {
+	store := emitStore(fn, a.addr, v, a.pos)
+	if a.expr != nil {
+		// store.Val is v, converted for assignability.
+		emitDebugRef(fn, a.expr, store.Val, false)
+	}
+}
+
+func (a *address) address(fn *Function) Value {
+	if a.expr != nil {
+		emitDebugRef(fn, a.expr, a.addr, true)
+	}
+	return a.addr
+}
+
+func (a *address) typ() types.Type {
+	return typeparams.MustDeref(a.addr.Type())
+}
+
+// An element is an lvalue represented by m[k], the location of an
+// element of a map.  These locations are not addressable
+// since pointers cannot be formed from them, but they do support
+// load() and store().
+type element struct {
+	m, k Value      // map
+	t    types.Type // map element type
+	pos  token.Pos  // source position of colon ({k:v}) or lbrack (m[k]=v)
+}
+
+func (e *element) load(fn *Function) Value {
+	l := &Lookup{
+		X:     e.m,
+		Index: e.k,
+	}
+	l.setPos(e.pos)
+	l.setType(e.t)
+	return fn.emit(l)
+}
+
+func (e *element) store(fn *Function, v Value) {
+	up := &MapUpdate{
+		Map:   e.m,
+		Key:   e.k,
+		Value: emitConv(fn, v, e.t),
+	}
+	up.pos = e.pos
+	fn.emit(up)
+}
+
+func (e *element) address(fn *Function) Value {
+	panic("map elements are not addressable")
+}
+
+func (e *element) typ() types.Type {
+	return e.t
+}
+
+// A lazyAddress is an lvalue whose address is the result of an instruction.
+// These work like an *address except a new address.address() Value
+// is created on each load, store and address call.
+// A lazyAddress can be used to control when a side effect (nil pointer
+// dereference, index out of bounds) of using a location happens.
+type lazyAddress struct {
+	addr func(fn *Function) Value // emit to fn the computation of the address
+	t    types.Type               // type of the location
+	pos  token.Pos                // source position
+	expr ast.Expr                 // source syntax of the value (not address) [debug mode]
+}
+
+func (l *lazyAddress) load(fn *Function) Value {
+	load := emitLoad(fn, l.addr(fn))
+	load.pos = l.pos
+	return load
+}
+
+func (l *lazyAddress) store(fn *Function, v Value) {
+	store := emitStore(fn, l.addr(fn), v, l.pos)
+	if l.expr != nil {
+		// store.Val is v, converted for assignability.
+		emitDebugRef(fn, l.expr, store.Val, false)
+	}
+}
+
+func (l *lazyAddress) address(fn *Function) Value {
+	addr := l.addr(fn)
+	if l.expr != nil {
+		emitDebugRef(fn, l.expr, addr, true)
+	}
+	return addr
+}
+
+func (l *lazyAddress) typ() types.Type { return l.t }
+
+// A blank is a dummy variable whose name is "_".
+// It is not reified: loads are illegal and stores are ignored.
+type blank struct{}
+
+func (bl blank) load(fn *Function) Value {
+	panic("blank.load is illegal")
+}
+
+func (bl blank) store(fn *Function, v Value) {
+	// no-op
+}
+
+func (bl blank) address(fn *Function) Value {
+	panic("blank var is not addressable")
+}
+
+func (bl blank) typ() types.Type {
+	// This should be the type of the blank Ident; the typechecker
+	// doesn't provide this yet, but fortunately, we don't need it
+	// yet either.
+	panic("blank.typ is unimplemented")
+}
diff --git a/vendor/golang.org/x/tools/go/ssa/methods.go b/vendor/golang.org/x/tools/go/ssa/methods.go
new file mode 100644
index 0000000..b956018
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ssa/methods.go
@@ -0,0 +1,281 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// This file defines utilities for population of method sets.
+
+import (
+	"fmt"
+	"go/types"
+
+	"golang.org/x/tools/go/types/typeutil"
+	"golang.org/x/tools/internal/aliases"
+)
+
+// MethodValue returns the Function implementing method sel, building
+// wrapper methods on demand. It returns nil if sel denotes an
+// interface or generic method.
+//
+// Precondition: sel.Kind() == MethodVal.
+//
+// Thread-safe.
+//
+// Acquires prog.methodsMu.
+func (prog *Program) MethodValue(sel *types.Selection) *Function {
+	if sel.Kind() != types.MethodVal {
+		panic(fmt.Sprintf("MethodValue(%s) kind != MethodVal", sel))
+	}
+	T := sel.Recv()
+	if types.IsInterface(T) {
+		return nil // interface method or type parameter
+	}
+
+	if prog.isParameterized(T) {
+		return nil // generic method
+	}
+
+	if prog.mode&LogSource != 0 {
+		defer logStack("MethodValue %s %v", T, sel)()
+	}
+
+	var b builder
+
+	m := func() *Function {
+		prog.methodsMu.Lock()
+		defer prog.methodsMu.Unlock()
+
+		// Get or create SSA method set.
+		mset, ok := prog.methodSets.At(T).(*methodSet)
+		if !ok {
+			mset = &methodSet{mapping: make(map[string]*Function)}
+			prog.methodSets.Set(T, mset)
+		}
+
+		// Get or create SSA method.
+		id := sel.Obj().Id()
+		fn, ok := mset.mapping[id]
+		if !ok {
+			obj := sel.Obj().(*types.Func)
+			needsPromotion := len(sel.Index()) > 1
+			needsIndirection := !isPointer(recvType(obj)) && isPointer(T)
+			if needsPromotion || needsIndirection {
+				fn = createWrapper(prog, toSelection(sel))
+				fn.buildshared = b.shared()
+				b.enqueue(fn)
+			} else {
+				fn = prog.objectMethod(obj, &b)
+			}
+			if fn.Signature.Recv() == nil {
+				panic(fn)
+			}
+			mset.mapping[id] = fn
+		} else {
+			b.waitForSharedFunction(fn)
+		}
+
+		return fn
+	}()
+
+	b.iterate()
+
+	return m
+}
+
+// objectMethod returns the Function for a given method symbol.
+// The symbol may be an instance of a generic function. It need not
+// belong to an existing SSA package created by a call to
+// prog.CreatePackage.
+//
+// objectMethod panics if the function is not a method.
+//
+// Acquires prog.objectMethodsMu.
+func (prog *Program) objectMethod(obj *types.Func, b *builder) *Function {
+	sig := obj.Type().(*types.Signature)
+	if sig.Recv() == nil {
+		panic("not a method: " + obj.String())
+	}
+
+	// Belongs to a created package?
+	if fn := prog.FuncValue(obj); fn != nil {
+		return fn
+	}
+
+	// Instantiation of generic?
+	if originObj := obj.Origin(); originObj != obj {
+		origin := prog.objectMethod(originObj, b)
+		assert(origin.typeparams.Len() > 0, "origin is not generic")
+		targs := receiverTypeArgs(obj)
+		return origin.instance(targs, b)
+	}
+
+	// Consult/update cache of methods created from types.Func.
+	prog.objectMethodsMu.Lock()
+	defer prog.objectMethodsMu.Unlock()
+	fn, ok := prog.objectMethods[obj]
+	if !ok {
+		fn = createFunction(prog, obj, obj.Name(), nil, nil, "")
+		fn.Synthetic = "from type information (on demand)"
+		fn.buildshared = b.shared()
+		b.enqueue(fn)
+
+		if prog.objectMethods == nil {
+			prog.objectMethods = make(map[*types.Func]*Function)
+		}
+		prog.objectMethods[obj] = fn
+	} else {
+		b.waitForSharedFunction(fn)
+	}
+	return fn
+}
+
+// LookupMethod returns the implementation of the method of type T
+// identified by (pkg, name).  It returns nil if the method exists but
+// is an interface method or generic method, and panics if T has no such method.
+func (prog *Program) LookupMethod(T types.Type, pkg *types.Package, name string) *Function {
+	sel := prog.MethodSets.MethodSet(T).Lookup(pkg, name)
+	if sel == nil {
+		panic(fmt.Sprintf("%s has no method %s", T, types.Id(pkg, name)))
+	}
+	return prog.MethodValue(sel)
+}
+
+// methodSet contains the (concrete) methods of a concrete type (non-interface, non-parameterized).
+type methodSet struct {
+	mapping map[string]*Function // populated lazily
+}
+
+// RuntimeTypes returns a new unordered slice containing all types in
+// the program for which a runtime type is required.
+//
+// A runtime type is required for any non-parameterized, non-interface
+// type that is converted to an interface, or for any type (including
+// interface types) derivable from one through reflection.
+//
+// The methods of such types may be reachable through reflection or
+// interface calls even if they are never called directly.
+//
+// Thread-safe.
+//
+// Acquires prog.runtimeTypesMu.
+func (prog *Program) RuntimeTypes() []types.Type {
+	prog.runtimeTypesMu.Lock()
+	defer prog.runtimeTypesMu.Unlock()
+	return prog.runtimeTypes.Keys()
+}
+
+// forEachReachable calls f for type T and each type reachable from
+// its type through reflection.
+//
+// The function f must use memoization to break cycles and
+// return false when the type has already been visited.
+//
+// TODO(adonovan): publish in typeutil and share with go/callgraph/rta.
+func forEachReachable(msets *typeutil.MethodSetCache, T types.Type, f func(types.Type) bool) {
+	var visit func(T types.Type, skip bool)
+	visit = func(T types.Type, skip bool) {
+		if !skip {
+			if !f(T) {
+				return
+			}
+		}
+
+		// Recursion over signatures of each method.
+		tmset := msets.MethodSet(T)
+		for i := 0; i < tmset.Len(); i++ {
+			sig := tmset.At(i).Type().(*types.Signature)
+			// It is tempting to call visit(sig, false)
+			// but, as noted in golang.org/cl/65450043,
+			// the Signature.Recv field is ignored by
+			// types.Identical and typeutil.Map, which
+			// is confusing at best.
+			//
+			// More importantly, the true signature rtype
+			// reachable from a method using reflection
+			// has no receiver but an extra ordinary parameter.
+			// For the Read method of io.Reader we want:
+			//   func(Reader, []byte) (int, error)
+			// but here sig is:
+			//   func([]byte) (int, error)
+			// with .Recv = Reader (though it is hard to
+			// notice because it doesn't affect Signature.String
+			// or types.Identical).
+			//
+			// TODO(adonovan): construct and visit the correct
+			// non-method signature with an extra parameter
+			// (though since unnamed func types have no methods
+			// there is essentially no actual demand for this).
+			//
+			// TODO(adonovan): document whether or not it is
+			// safe to skip non-exported methods (as RTA does).
+			visit(sig.Params(), true)  // skip the Tuple
+			visit(sig.Results(), true) // skip the Tuple
+		}
+
+		switch T := T.(type) {
+		case *aliases.Alias:
+			visit(aliases.Unalias(T), skip) // emulates the pre-Alias behavior
+
+		case *types.Basic:
+			// nop
+
+		case *types.Interface:
+			// nop---handled by recursion over method set.
+
+		case *types.Pointer:
+			visit(T.Elem(), false)
+
+		case *types.Slice:
+			visit(T.Elem(), false)
+
+		case *types.Chan:
+			visit(T.Elem(), false)
+
+		case *types.Map:
+			visit(T.Key(), false)
+			visit(T.Elem(), false)
+
+		case *types.Signature:
+			if T.Recv() != nil {
+				panic(fmt.Sprintf("Signature %s has Recv %s", T, T.Recv()))
+			}
+			visit(T.Params(), true)  // skip the Tuple
+			visit(T.Results(), true) // skip the Tuple
+
+		case *types.Named:
+			// A pointer-to-named type can be derived from a named
+			// type via reflection.  It may have methods too.
+			visit(types.NewPointer(T), false)
+
+			// Consider 'type T struct{S}' where S has methods.
+			// Reflection provides no way to get from T to struct{S},
+			// only to S, so the method set of struct{S} is unwanted,
+			// so set 'skip' flag during recursion.
+			visit(T.Underlying(), true) // skip the unnamed type
+
+		case *types.Array:
+			visit(T.Elem(), false)
+
+		case *types.Struct:
+			for i, n := 0, T.NumFields(); i < n; i++ {
+				// TODO(adonovan): document whether or not
+				// it is safe to skip non-exported fields.
+				visit(T.Field(i).Type(), false)
+			}
+
+		case *types.Tuple:
+			for i, n := 0, T.Len(); i < n; i++ {
+				visit(T.At(i).Type(), false)
+			}
+
+		case *types.TypeParam, *types.Union:
+			// forEachReachable must not be called on parameterized types.
+			panic(T)
+
+		default:
+			panic(T)
+		}
+	}
+	visit(T, false)
+}
diff --git a/vendor/golang.org/x/tools/go/ssa/mode.go b/vendor/golang.org/x/tools/go/ssa/mode.go
new file mode 100644
index 0000000..8381639
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ssa/mode.go
@@ -0,0 +1,111 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// This file defines the BuilderMode type and its command-line flag.
+
+import (
+	"bytes"
+	"fmt"
+)
+
+// BuilderMode is a bitmask of options for diagnostics and checking.
+//
+// *BuilderMode satisfies the flag.Value interface.  Example:
+//
+//	var mode = ssa.BuilderMode(0)
+//	func init() { flag.Var(&mode, "build", ssa.BuilderModeDoc) }
+type BuilderMode uint
+
+const (
+	PrintPackages        BuilderMode = 1 << iota // Print package inventory to stdout
+	PrintFunctions                               // Print function SSA code to stdout
+	LogSource                                    // Log source locations as SSA builder progresses
+	SanityCheckFunctions                         // Perform sanity checking of function bodies
+	NaiveForm                                    // Build naïve SSA form: don't replace local loads/stores with registers
+	BuildSerially                                // Build packages serially, not in parallel.
+	GlobalDebug                                  // Enable debug info for all packages
+	BareInits                                    // Build init functions without guards or calls to dependent inits
+	InstantiateGenerics                          // Instantiate generics functions (monomorphize) while building
+)
+
+const BuilderModeDoc = `Options controlling the SSA builder.
+The value is a sequence of zero or more of these letters:
+C	perform sanity [C]hecking of the SSA form.
+D	include [D]ebug info for every function.
+P	print [P]ackage inventory.
+F	print [F]unction SSA code.
+S	log [S]ource locations as SSA builder progresses.
+L	build distinct packages seria[L]ly instead of in parallel.
+N	build [N]aive SSA form: don't replace local loads/stores with registers.
+I	build bare [I]nit functions: no init guards or calls to dependent inits.
+G   instantiate [G]eneric function bodies via monomorphization
+`
+
+func (m BuilderMode) String() string {
+	var buf bytes.Buffer
+	if m&GlobalDebug != 0 {
+		buf.WriteByte('D')
+	}
+	if m&PrintPackages != 0 {
+		buf.WriteByte('P')
+	}
+	if m&PrintFunctions != 0 {
+		buf.WriteByte('F')
+	}
+	if m&LogSource != 0 {
+		buf.WriteByte('S')
+	}
+	if m&SanityCheckFunctions != 0 {
+		buf.WriteByte('C')
+	}
+	if m&NaiveForm != 0 {
+		buf.WriteByte('N')
+	}
+	if m&BuildSerially != 0 {
+		buf.WriteByte('L')
+	}
+	if m&BareInits != 0 {
+		buf.WriteByte('I')
+	}
+	if m&InstantiateGenerics != 0 {
+		buf.WriteByte('G')
+	}
+	return buf.String()
+}
+
+// Set parses the flag characters in s and updates *m.
+func (m *BuilderMode) Set(s string) error {
+	var mode BuilderMode
+	for _, c := range s {
+		switch c {
+		case 'D':
+			mode |= GlobalDebug
+		case 'P':
+			mode |= PrintPackages
+		case 'F':
+			mode |= PrintFunctions
+		case 'S':
+			mode |= LogSource | BuildSerially
+		case 'C':
+			mode |= SanityCheckFunctions
+		case 'N':
+			mode |= NaiveForm
+		case 'L':
+			mode |= BuildSerially
+		case 'I':
+			mode |= BareInits
+		case 'G':
+			mode |= InstantiateGenerics
+		default:
+			return fmt.Errorf("unknown BuilderMode option: %q", c)
+		}
+	}
+	*m = mode
+	return nil
+}
+
+// Get returns m.
+func (m BuilderMode) Get() interface{} { return m }
diff --git a/vendor/golang.org/x/tools/go/ssa/print.go b/vendor/golang.org/x/tools/go/ssa/print.go
new file mode 100644
index 0000000..c890d7e
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ssa/print.go
@@ -0,0 +1,470 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// This file implements the String() methods for all Value and
+// Instruction types.
+
+import (
+	"bytes"
+	"fmt"
+	"go/types"
+	"io"
+	"reflect"
+	"sort"
+	"strings"
+
+	"golang.org/x/tools/go/types/typeutil"
+	"golang.org/x/tools/internal/typeparams"
+)
+
+// relName returns the name of v relative to i.
+// In most cases, this is identical to v.Name(), but references to
+// Functions (including methods) and Globals use RelString and
+// all types are displayed with relType, so that only cross-package
+// references are package-qualified.
+func relName(v Value, i Instruction) string {
+	var from *types.Package
+	if i != nil {
+		from = i.Parent().relPkg()
+	}
+	switch v := v.(type) {
+	case Member: // *Function or *Global
+		return v.RelString(from)
+	case *Const:
+		return v.RelString(from)
+	}
+	return v.Name()
+}
+
+// normalizeAnyForTesting controls whether we replace occurrences of
+// interface{} with any. It is only used for normalizing test output.
+var normalizeAnyForTesting bool
+
+func relType(t types.Type, from *types.Package) string {
+	s := types.TypeString(t, types.RelativeTo(from))
+	if normalizeAnyForTesting {
+		s = strings.ReplaceAll(s, "interface{}", "any")
+	}
+	return s
+}
+
+func relTerm(term *types.Term, from *types.Package) string {
+	s := relType(term.Type(), from)
+	if term.Tilde() {
+		return "~" + s
+	}
+	return s
+}
+
+func relString(m Member, from *types.Package) string {
+	// NB: not all globals have an Object (e.g. init$guard),
+	// so use Package().Object not Object.Package().
+	if pkg := m.Package().Pkg; pkg != nil && pkg != from {
+		return fmt.Sprintf("%s.%s", pkg.Path(), m.Name())
+	}
+	return m.Name()
+}
+
+// Value.String()
+//
+// This method is provided only for debugging.
+// It never appears in disassembly, which uses Value.Name().
+
+func (v *Parameter) String() string {
+	from := v.Parent().relPkg()
+	return fmt.Sprintf("parameter %s : %s", v.Name(), relType(v.Type(), from))
+}
+
+func (v *FreeVar) String() string {
+	from := v.Parent().relPkg()
+	return fmt.Sprintf("freevar %s : %s", v.Name(), relType(v.Type(), from))
+}
+
+func (v *Builtin) String() string {
+	return fmt.Sprintf("builtin %s", v.Name())
+}
+
+// Instruction.String()
+
+func (v *Alloc) String() string {
+	op := "local"
+	if v.Heap {
+		op = "new"
+	}
+	from := v.Parent().relPkg()
+	return fmt.Sprintf("%s %s (%s)", op, relType(typeparams.MustDeref(v.Type()), from), v.Comment)
+}
+
+func (v *Phi) String() string {
+	var b bytes.Buffer
+	b.WriteString("phi [")
+	for i, edge := range v.Edges {
+		if i > 0 {
+			b.WriteString(", ")
+		}
+		// Be robust against malformed CFG.
+		if v.block == nil {
+			b.WriteString("??")
+			continue
+		}
+		block := -1
+		if i < len(v.block.Preds) {
+			block = v.block.Preds[i].Index
+		}
+		fmt.Fprintf(&b, "%d: ", block)
+		edgeVal := "<nil>" // be robust
+		if edge != nil {
+			edgeVal = relName(edge, v)
+		}
+		b.WriteString(edgeVal)
+	}
+	b.WriteString("]")
+	if v.Comment != "" {
+		b.WriteString(" #")
+		b.WriteString(v.Comment)
+	}
+	return b.String()
+}
+
+func printCall(v *CallCommon, prefix string, instr Instruction) string {
+	var b bytes.Buffer
+	b.WriteString(prefix)
+	if !v.IsInvoke() {
+		b.WriteString(relName(v.Value, instr))
+	} else {
+		fmt.Fprintf(&b, "invoke %s.%s", relName(v.Value, instr), v.Method.Name())
+	}
+	b.WriteString("(")
+	for i, arg := range v.Args {
+		if i > 0 {
+			b.WriteString(", ")
+		}
+		b.WriteString(relName(arg, instr))
+	}
+	if v.Signature().Variadic() {
+		b.WriteString("...")
+	}
+	b.WriteString(")")
+	return b.String()
+}
+
+func (c *CallCommon) String() string {
+	return printCall(c, "", nil)
+}
+
+func (v *Call) String() string {
+	return printCall(&v.Call, "", v)
+}
+
+func (v *BinOp) String() string {
+	return fmt.Sprintf("%s %s %s", relName(v.X, v), v.Op.String(), relName(v.Y, v))
+}
+
+func (v *UnOp) String() string {
+	return fmt.Sprintf("%s%s%s", v.Op, relName(v.X, v), commaOk(v.CommaOk))
+}
+
+func printConv(prefix string, v, x Value) string {
+	from := v.Parent().relPkg()
+	return fmt.Sprintf("%s %s <- %s (%s)",
+		prefix,
+		relType(v.Type(), from),
+		relType(x.Type(), from),
+		relName(x, v.(Instruction)))
+}
+
+func (v *ChangeType) String() string          { return printConv("changetype", v, v.X) }
+func (v *Convert) String() string             { return printConv("convert", v, v.X) }
+func (v *ChangeInterface) String() string     { return printConv("change interface", v, v.X) }
+func (v *SliceToArrayPointer) String() string { return printConv("slice to array pointer", v, v.X) }
+func (v *MakeInterface) String() string       { return printConv("make", v, v.X) }
+
+func (v *MultiConvert) String() string {
+	from := v.Parent().relPkg()
+
+	var b strings.Builder
+	b.WriteString(printConv("multiconvert", v, v.X))
+	b.WriteString(" [")
+	for i, s := range v.from {
+		for j, d := range v.to {
+			if i != 0 || j != 0 {
+				b.WriteString(" | ")
+			}
+			fmt.Fprintf(&b, "%s <- %s", relTerm(d, from), relTerm(s, from))
+		}
+	}
+	b.WriteString("]")
+	return b.String()
+}
+
+func (v *MakeClosure) String() string {
+	var b bytes.Buffer
+	fmt.Fprintf(&b, "make closure %s", relName(v.Fn, v))
+	if v.Bindings != nil {
+		b.WriteString(" [")
+		for i, c := range v.Bindings {
+			if i > 0 {
+				b.WriteString(", ")
+			}
+			b.WriteString(relName(c, v))
+		}
+		b.WriteString("]")
+	}
+	return b.String()
+}
+
+func (v *MakeSlice) String() string {
+	from := v.Parent().relPkg()
+	return fmt.Sprintf("make %s %s %s",
+		relType(v.Type(), from),
+		relName(v.Len, v),
+		relName(v.Cap, v))
+}
+
+func (v *Slice) String() string {
+	var b bytes.Buffer
+	b.WriteString("slice ")
+	b.WriteString(relName(v.X, v))
+	b.WriteString("[")
+	if v.Low != nil {
+		b.WriteString(relName(v.Low, v))
+	}
+	b.WriteString(":")
+	if v.High != nil {
+		b.WriteString(relName(v.High, v))
+	}
+	if v.Max != nil {
+		b.WriteString(":")
+		b.WriteString(relName(v.Max, v))
+	}
+	b.WriteString("]")
+	return b.String()
+}
+
+func (v *MakeMap) String() string {
+	res := ""
+	if v.Reserve != nil {
+		res = relName(v.Reserve, v)
+	}
+	from := v.Parent().relPkg()
+	return fmt.Sprintf("make %s %s", relType(v.Type(), from), res)
+}
+
+func (v *MakeChan) String() string {
+	from := v.Parent().relPkg()
+	return fmt.Sprintf("make %s %s", relType(v.Type(), from), relName(v.Size, v))
+}
+
+func (v *FieldAddr) String() string {
+	// Be robust against a bad index.
+	name := "?"
+	if fld := fieldOf(typeparams.MustDeref(v.X.Type()), v.Field); fld != nil {
+		name = fld.Name()
+	}
+	return fmt.Sprintf("&%s.%s [#%d]", relName(v.X, v), name, v.Field)
+}
+
+func (v *Field) String() string {
+	// Be robust against a bad index.
+	name := "?"
+	if fld := fieldOf(v.X.Type(), v.Field); fld != nil {
+		name = fld.Name()
+	}
+	return fmt.Sprintf("%s.%s [#%d]", relName(v.X, v), name, v.Field)
+}
+
+func (v *IndexAddr) String() string {
+	return fmt.Sprintf("&%s[%s]", relName(v.X, v), relName(v.Index, v))
+}
+
+func (v *Index) String() string {
+	return fmt.Sprintf("%s[%s]", relName(v.X, v), relName(v.Index, v))
+}
+
+func (v *Lookup) String() string {
+	return fmt.Sprintf("%s[%s]%s", relName(v.X, v), relName(v.Index, v), commaOk(v.CommaOk))
+}
+
+func (v *Range) String() string {
+	return "range " + relName(v.X, v)
+}
+
+func (v *Next) String() string {
+	return "next " + relName(v.Iter, v)
+}
+
+func (v *TypeAssert) String() string {
+	from := v.Parent().relPkg()
+	return fmt.Sprintf("typeassert%s %s.(%s)", commaOk(v.CommaOk), relName(v.X, v), relType(v.AssertedType, from))
+}
+
+func (v *Extract) String() string {
+	return fmt.Sprintf("extract %s #%d", relName(v.Tuple, v), v.Index)
+}
+
+func (s *Jump) String() string {
+	// Be robust against malformed CFG.
+	block := -1
+	if s.block != nil && len(s.block.Succs) == 1 {
+		block = s.block.Succs[0].Index
+	}
+	return fmt.Sprintf("jump %d", block)
+}
+
+func (s *If) String() string {
+	// Be robust against malformed CFG.
+	tblock, fblock := -1, -1
+	if s.block != nil && len(s.block.Succs) == 2 {
+		tblock = s.block.Succs[0].Index
+		fblock = s.block.Succs[1].Index
+	}
+	return fmt.Sprintf("if %s goto %d else %d", relName(s.Cond, s), tblock, fblock)
+}
+
+func (s *Go) String() string {
+	return printCall(&s.Call, "go ", s)
+}
+
+func (s *Panic) String() string {
+	return "panic " + relName(s.X, s)
+}
+
+func (s *Return) String() string {
+	var b bytes.Buffer
+	b.WriteString("return")
+	for i, r := range s.Results {
+		if i == 0 {
+			b.WriteString(" ")
+		} else {
+			b.WriteString(", ")
+		}
+		b.WriteString(relName(r, s))
+	}
+	return b.String()
+}
+
+func (*RunDefers) String() string {
+	return "rundefers"
+}
+
+func (s *Send) String() string {
+	return fmt.Sprintf("send %s <- %s", relName(s.Chan, s), relName(s.X, s))
+}
+
+func (s *Defer) String() string {
+	prefix := "defer "
+	if s.DeferStack != nil {
+		prefix += "[" + relName(s.DeferStack, s) + "] "
+	}
+	c := printCall(&s.Call, prefix, s)
+	return c
+}
+
+func (s *Select) String() string {
+	var b bytes.Buffer
+	for i, st := range s.States {
+		if i > 0 {
+			b.WriteString(", ")
+		}
+		if st.Dir == types.RecvOnly {
+			b.WriteString("<-")
+			b.WriteString(relName(st.Chan, s))
+		} else {
+			b.WriteString(relName(st.Chan, s))
+			b.WriteString("<-")
+			b.WriteString(relName(st.Send, s))
+		}
+	}
+	non := ""
+	if !s.Blocking {
+		non = "non"
+	}
+	return fmt.Sprintf("select %sblocking [%s]", non, b.String())
+}
+
+func (s *Store) String() string {
+	return fmt.Sprintf("*%s = %s", relName(s.Addr, s), relName(s.Val, s))
+}
+
+func (s *MapUpdate) String() string {
+	return fmt.Sprintf("%s[%s] = %s", relName(s.Map, s), relName(s.Key, s), relName(s.Value, s))
+}
+
+func (s *DebugRef) String() string {
+	p := s.Parent().Prog.Fset.Position(s.Pos())
+	var descr interface{}
+	if s.object != nil {
+		descr = s.object // e.g. "var x int"
+	} else {
+		descr = reflect.TypeOf(s.Expr) // e.g. "*ast.CallExpr"
+	}
+	var addr string
+	if s.IsAddr {
+		addr = "address of "
+	}
+	return fmt.Sprintf("; %s%s @ %d:%d is %s", addr, descr, p.Line, p.Column, s.X.Name())
+}
+
+func (p *Package) String() string {
+	return "package " + p.Pkg.Path()
+}
+
+var _ io.WriterTo = (*Package)(nil) // *Package implements io.Writer
+
+func (p *Package) WriteTo(w io.Writer) (int64, error) {
+	var buf bytes.Buffer
+	WritePackage(&buf, p)
+	n, err := w.Write(buf.Bytes())
+	return int64(n), err
+}
+
+// WritePackage writes to buf a human-readable summary of p.
+func WritePackage(buf *bytes.Buffer, p *Package) {
+	fmt.Fprintf(buf, "%s:\n", p)
+
+	var names []string
+	maxname := 0
+	for name := range p.Members {
+		if l := len(name); l > maxname {
+			maxname = l
+		}
+		names = append(names, name)
+	}
+
+	from := p.Pkg
+	sort.Strings(names)
+	for _, name := range names {
+		switch mem := p.Members[name].(type) {
+		case *NamedConst:
+			fmt.Fprintf(buf, "  const %-*s %s = %s\n",
+				maxname, name, mem.Name(), mem.Value.RelString(from))
+
+		case *Function:
+			fmt.Fprintf(buf, "  func  %-*s %s\n",
+				maxname, name, relType(mem.Type(), from))
+
+		case *Type:
+			fmt.Fprintf(buf, "  type  %-*s %s\n",
+				maxname, name, relType(mem.Type().Underlying(), from))
+			for _, meth := range typeutil.IntuitiveMethodSet(mem.Type(), &p.Prog.MethodSets) {
+				fmt.Fprintf(buf, "    %s\n", types.SelectionString(meth, types.RelativeTo(from)))
+			}
+
+		case *Global:
+			fmt.Fprintf(buf, "  var   %-*s %s\n",
+				maxname, name, relType(typeparams.MustDeref(mem.Type()), from))
+		}
+	}
+
+	fmt.Fprintf(buf, "\n")
+}
+
+func commaOk(x bool) string {
+	if x {
+		return ",ok"
+	}
+	return ""
+}
diff --git a/vendor/golang.org/x/tools/go/ssa/sanity.go b/vendor/golang.org/x/tools/go/ssa/sanity.go
new file mode 100644
index 0000000..285cba0
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ssa/sanity.go
@@ -0,0 +1,560 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// An optional pass for sanity-checking invariants of the SSA representation.
+// Currently it checks CFG invariants but little at the instruction level.
+
+import (
+	"bytes"
+	"fmt"
+	"go/ast"
+	"go/types"
+	"io"
+	"os"
+	"strings"
+)
+
+type sanity struct {
+	reporter io.Writer
+	fn       *Function
+	block    *BasicBlock
+	instrs   map[Instruction]unit
+	insane   bool
+}
+
+// sanityCheck performs integrity checking of the SSA representation
+// of the function fn and returns true if it was valid.  Diagnostics
+// are written to reporter if non-nil, os.Stderr otherwise.  Some
+// diagnostics are only warnings and do not imply a negative result.
+//
+// Sanity-checking is intended to facilitate the debugging of code
+// transformation passes.
+func sanityCheck(fn *Function, reporter io.Writer) bool {
+	if reporter == nil {
+		reporter = os.Stderr
+	}
+	return (&sanity{reporter: reporter}).checkFunction(fn)
+}
+
+// mustSanityCheck is like sanityCheck but panics instead of returning
+// a negative result.
+func mustSanityCheck(fn *Function, reporter io.Writer) {
+	if !sanityCheck(fn, reporter) {
+		fn.WriteTo(os.Stderr)
+		panic("SanityCheck failed")
+	}
+}
+
+func (s *sanity) diagnostic(prefix, format string, args ...interface{}) {
+	fmt.Fprintf(s.reporter, "%s: function %s", prefix, s.fn)
+	if s.block != nil {
+		fmt.Fprintf(s.reporter, ", block %s", s.block)
+	}
+	io.WriteString(s.reporter, ": ")
+	fmt.Fprintf(s.reporter, format, args...)
+	io.WriteString(s.reporter, "\n")
+}
+
+func (s *sanity) errorf(format string, args ...interface{}) {
+	s.insane = true
+	s.diagnostic("Error", format, args...)
+}
+
+func (s *sanity) warnf(format string, args ...interface{}) {
+	s.diagnostic("Warning", format, args...)
+}
+
+// findDuplicate returns an arbitrary basic block that appeared more
+// than once in blocks, or nil if all were unique.
+func findDuplicate(blocks []*BasicBlock) *BasicBlock {
+	if len(blocks) < 2 {
+		return nil
+	}
+	if blocks[0] == blocks[1] {
+		return blocks[0]
+	}
+	// Slow path:
+	m := make(map[*BasicBlock]bool)
+	for _, b := range blocks {
+		if m[b] {
+			return b
+		}
+		m[b] = true
+	}
+	return nil
+}
+
+func (s *sanity) checkInstr(idx int, instr Instruction) {
+	switch instr := instr.(type) {
+	case *If, *Jump, *Return, *Panic:
+		s.errorf("control flow instruction not at end of block")
+	case *Phi:
+		if idx == 0 {
+			// It suffices to apply this check to just the first phi node.
+			if dup := findDuplicate(s.block.Preds); dup != nil {
+				s.errorf("phi node in block with duplicate predecessor %s", dup)
+			}
+		} else {
+			prev := s.block.Instrs[idx-1]
+			if _, ok := prev.(*Phi); !ok {
+				s.errorf("Phi instruction follows a non-Phi: %T", prev)
+			}
+		}
+		if ne, np := len(instr.Edges), len(s.block.Preds); ne != np {
+			s.errorf("phi node has %d edges but %d predecessors", ne, np)
+
+		} else {
+			for i, e := range instr.Edges {
+				if e == nil {
+					s.errorf("phi node '%s' has no value for edge #%d from %s", instr.Comment, i, s.block.Preds[i])
+				} else if !types.Identical(instr.typ, e.Type()) {
+					s.errorf("phi node '%s' has a different type (%s) for edge #%d from %s (%s)",
+						instr.Comment, instr.Type(), i, s.block.Preds[i], e.Type())
+				}
+			}
+		}
+
+	case *Alloc:
+		if !instr.Heap {
+			found := false
+			for _, l := range s.fn.Locals {
+				if l == instr {
+					found = true
+					break
+				}
+			}
+			if !found {
+				s.errorf("local alloc %s = %s does not appear in Function.Locals", instr.Name(), instr)
+			}
+		}
+
+	case *BinOp:
+	case *Call:
+		if common := instr.Call; common.IsInvoke() {
+			if !types.IsInterface(common.Value.Type()) {
+				s.errorf("invoke on %s (%s) which is not an interface type (or type param)", common.Value, common.Value.Type())
+			}
+		}
+	case *ChangeInterface:
+	case *ChangeType:
+	case *SliceToArrayPointer:
+	case *Convert:
+		if from := instr.X.Type(); !isBasicConvTypes(typeSetOf(from)) {
+			if to := instr.Type(); !isBasicConvTypes(typeSetOf(to)) {
+				s.errorf("convert %s -> %s: at least one type must be basic (or all basic, []byte, or []rune)", from, to)
+			}
+		}
+	case *MultiConvert:
+	case *Defer:
+	case *Extract:
+	case *Field:
+	case *FieldAddr:
+	case *Go:
+	case *Index:
+	case *IndexAddr:
+	case *Lookup:
+	case *MakeChan:
+	case *MakeClosure:
+		numFree := len(instr.Fn.(*Function).FreeVars)
+		numBind := len(instr.Bindings)
+		if numFree != numBind {
+			s.errorf("MakeClosure has %d Bindings for function %s with %d free vars",
+				numBind, instr.Fn, numFree)
+
+		}
+		if recv := instr.Type().(*types.Signature).Recv(); recv != nil {
+			s.errorf("MakeClosure's type includes receiver %s", recv.Type())
+		}
+
+	case *MakeInterface:
+	case *MakeMap:
+	case *MakeSlice:
+	case *MapUpdate:
+	case *Next:
+	case *Range:
+	case *RunDefers:
+	case *Select:
+	case *Send:
+	case *Slice:
+	case *Store:
+	case *TypeAssert:
+	case *UnOp:
+	case *DebugRef:
+		// TODO(adonovan): implement checks.
+	default:
+		panic(fmt.Sprintf("Unknown instruction type: %T", instr))
+	}
+
+	if call, ok := instr.(CallInstruction); ok {
+		if call.Common().Signature() == nil {
+			s.errorf("nil signature: %s", call)
+		}
+	}
+
+	// Check that value-defining instructions have valid types
+	// and a valid referrer list.
+	if v, ok := instr.(Value); ok {
+		t := v.Type()
+		if t == nil {
+			s.errorf("no type: %s = %s", v.Name(), v)
+		} else if t == tRangeIter || t == tDeferStack {
+			// not a proper type; ignore.
+		} else if b, ok := t.Underlying().(*types.Basic); ok && b.Info()&types.IsUntyped != 0 {
+			s.errorf("instruction has 'untyped' result: %s = %s : %s", v.Name(), v, t)
+		}
+		s.checkReferrerList(v)
+	}
+
+	// Untyped constants are legal as instruction Operands(),
+	// for example:
+	//   _ = "foo"[0]
+	// or:
+	//   if wordsize==64 {...}
+
+	// All other non-Instruction Values can be found via their
+	// enclosing Function or Package.
+}
+
+func (s *sanity) checkFinalInstr(instr Instruction) {
+	switch instr := instr.(type) {
+	case *If:
+		if nsuccs := len(s.block.Succs); nsuccs != 2 {
+			s.errorf("If-terminated block has %d successors; expected 2", nsuccs)
+			return
+		}
+		if s.block.Succs[0] == s.block.Succs[1] {
+			s.errorf("If-instruction has same True, False target blocks: %s", s.block.Succs[0])
+			return
+		}
+
+	case *Jump:
+		if nsuccs := len(s.block.Succs); nsuccs != 1 {
+			s.errorf("Jump-terminated block has %d successors; expected 1", nsuccs)
+			return
+		}
+
+	case *Return:
+		if nsuccs := len(s.block.Succs); nsuccs != 0 {
+			s.errorf("Return-terminated block has %d successors; expected none", nsuccs)
+			return
+		}
+		if na, nf := len(instr.Results), s.fn.Signature.Results().Len(); nf != na {
+			s.errorf("%d-ary return in %d-ary function", na, nf)
+		}
+
+	case *Panic:
+		if nsuccs := len(s.block.Succs); nsuccs != 0 {
+			s.errorf("Panic-terminated block has %d successors; expected none", nsuccs)
+			return
+		}
+
+	default:
+		s.errorf("non-control flow instruction at end of block")
+	}
+}
+
+func (s *sanity) checkBlock(b *BasicBlock, index int) {
+	s.block = b
+
+	if b.Index != index {
+		s.errorf("block has incorrect Index %d", b.Index)
+	}
+	if b.parent != s.fn {
+		s.errorf("block has incorrect parent %s", b.parent)
+	}
+
+	// Check all blocks are reachable.
+	// (The entry block is always implicitly reachable,
+	// as is the Recover block, if any.)
+	if (index > 0 && b != b.parent.Recover) && len(b.Preds) == 0 {
+		s.warnf("unreachable block")
+		if b.Instrs == nil {
+			// Since this block is about to be pruned,
+			// tolerating transient problems in it
+			// simplifies other optimizations.
+			return
+		}
+	}
+
+	// Check predecessor and successor relations are dual,
+	// and that all blocks in CFG belong to same function.
+	for _, a := range b.Preds {
+		found := false
+		for _, bb := range a.Succs {
+			if bb == b {
+				found = true
+				break
+			}
+		}
+		if !found {
+			s.errorf("expected successor edge in predecessor %s; found only: %s", a, a.Succs)
+		}
+		if a.parent != s.fn {
+			s.errorf("predecessor %s belongs to different function %s", a, a.parent)
+		}
+	}
+	for _, c := range b.Succs {
+		found := false
+		for _, bb := range c.Preds {
+			if bb == b {
+				found = true
+				break
+			}
+		}
+		if !found {
+			s.errorf("expected predecessor edge in successor %s; found only: %s", c, c.Preds)
+		}
+		if c.parent != s.fn {
+			s.errorf("successor %s belongs to different function %s", c, c.parent)
+		}
+	}
+
+	// Check each instruction is sane.
+	n := len(b.Instrs)
+	if n == 0 {
+		s.errorf("basic block contains no instructions")
+	}
+	var rands [10]*Value // reuse storage
+	for j, instr := range b.Instrs {
+		if instr == nil {
+			s.errorf("nil instruction at index %d", j)
+			continue
+		}
+		if b2 := instr.Block(); b2 == nil {
+			s.errorf("nil Block() for instruction at index %d", j)
+			continue
+		} else if b2 != b {
+			s.errorf("wrong Block() (%s) for instruction at index %d ", b2, j)
+			continue
+		}
+		if j < n-1 {
+			s.checkInstr(j, instr)
+		} else {
+			s.checkFinalInstr(instr)
+		}
+
+		// Check Instruction.Operands.
+	operands:
+		for i, op := range instr.Operands(rands[:0]) {
+			if op == nil {
+				s.errorf("nil operand pointer %d of %s", i, instr)
+				continue
+			}
+			val := *op
+			if val == nil {
+				continue // a nil operand is ok
+			}
+
+			// Check that "untyped" types only appear on constant operands.
+			if _, ok := (*op).(*Const); !ok {
+				if basic, ok := (*op).Type().Underlying().(*types.Basic); ok {
+					if basic.Info()&types.IsUntyped != 0 {
+						s.errorf("operand #%d of %s is untyped: %s", i, instr, basic)
+					}
+				}
+			}
+
+			// Check that Operands that are also Instructions belong to same function.
+			// TODO(adonovan): also check their block dominates block b.
+			if val, ok := val.(Instruction); ok {
+				if val.Block() == nil {
+					s.errorf("operand %d of %s is an instruction (%s) that belongs to no block", i, instr, val)
+				} else if val.Parent() != s.fn {
+					s.errorf("operand %d of %s is an instruction (%s) from function %s", i, instr, val, val.Parent())
+				}
+			}
+
+			// Check that each function-local operand of
+			// instr refers back to instr.  (NB: quadratic)
+			switch val := val.(type) {
+			case *Const, *Global, *Builtin:
+				continue // not local
+			case *Function:
+				if val.parent == nil {
+					continue // only anon functions are local
+				}
+			}
+
+			// TODO(adonovan): check val.Parent() != nil <=> val.Referrers() is defined.
+
+			if refs := val.Referrers(); refs != nil {
+				for _, ref := range *refs {
+					if ref == instr {
+						continue operands
+					}
+				}
+				s.errorf("operand %d of %s (%s) does not refer to us", i, instr, val)
+			} else {
+				s.errorf("operand %d of %s (%s) has no referrers", i, instr, val)
+			}
+		}
+	}
+}
+
+func (s *sanity) checkReferrerList(v Value) {
+	refs := v.Referrers()
+	if refs == nil {
+		s.errorf("%s has missing referrer list", v.Name())
+		return
+	}
+	for i, ref := range *refs {
+		if _, ok := s.instrs[ref]; !ok {
+			s.errorf("%s.Referrers()[%d] = %s is not an instruction belonging to this function", v.Name(), i, ref)
+		}
+	}
+}
+
+func (s *sanity) checkFunction(fn *Function) bool {
+	// TODO(adonovan): check Function invariants:
+	// - check params match signature
+	// - check transient fields are nil
+	// - warn if any fn.Locals do not appear among block instructions.
+
+	// TODO(taking): Sanity check origin, typeparams, and typeargs.
+	s.fn = fn
+	if fn.Prog == nil {
+		s.errorf("nil Prog")
+	}
+
+	var buf bytes.Buffer
+	_ = fn.String()               // must not crash
+	_ = fn.RelString(fn.relPkg()) // must not crash
+	WriteFunction(&buf, fn)       // must not crash
+
+	// All functions have a package, except delegates (which are
+	// shared across packages, or duplicated as weak symbols in a
+	// separate-compilation model), and error.Error.
+	if fn.Pkg == nil {
+		if strings.HasPrefix(fn.Synthetic, "from type information (on demand)") ||
+			strings.HasPrefix(fn.Synthetic, "wrapper ") ||
+			strings.HasPrefix(fn.Synthetic, "bound ") ||
+			strings.HasPrefix(fn.Synthetic, "thunk ") ||
+			strings.HasSuffix(fn.name, "Error") ||
+			strings.HasPrefix(fn.Synthetic, "instance ") ||
+			strings.HasPrefix(fn.Synthetic, "instantiation ") ||
+			(fn.parent != nil && len(fn.typeargs) > 0) /* anon fun in instance */ {
+			// ok
+		} else {
+			s.errorf("nil Pkg")
+		}
+	}
+	if src, syn := fn.Synthetic == "", fn.Syntax() != nil; src != syn {
+		if len(fn.typeargs) > 0 && fn.Prog.mode&InstantiateGenerics != 0 {
+			// ok (instantiation with InstantiateGenerics on)
+		} else if fn.topLevelOrigin != nil && len(fn.typeargs) > 0 {
+			// ok (we always have the syntax set for instantiation)
+		} else if _, rng := fn.syntax.(*ast.RangeStmt); rng && fn.Synthetic == "range-over-func yield" {
+			// ok (range-func-yields are both synthetic and keep syntax)
+		} else {
+			s.errorf("got fromSource=%t, hasSyntax=%t; want same values", src, syn)
+		}
+	}
+	for i, l := range fn.Locals {
+		if l.Parent() != fn {
+			s.errorf("Local %s at index %d has wrong parent", l.Name(), i)
+		}
+		if l.Heap {
+			s.errorf("Local %s at index %d has Heap flag set", l.Name(), i)
+		}
+	}
+	// Build the set of valid referrers.
+	s.instrs = make(map[Instruction]unit)
+	for _, b := range fn.Blocks {
+		for _, instr := range b.Instrs {
+			s.instrs[instr] = unit{}
+		}
+	}
+	for i, p := range fn.Params {
+		if p.Parent() != fn {
+			s.errorf("Param %s at index %d has wrong parent", p.Name(), i)
+		}
+		// Check common suffix of Signature and Params match type.
+		if sig := fn.Signature; sig != nil {
+			j := i - len(fn.Params) + sig.Params().Len() // index within sig.Params
+			if j < 0 {
+				continue
+			}
+			if !types.Identical(p.Type(), sig.Params().At(j).Type()) {
+				s.errorf("Param %s at index %d has wrong type (%s, versus %s in Signature)", p.Name(), i, p.Type(), sig.Params().At(j).Type())
+
+			}
+		}
+		s.checkReferrerList(p)
+	}
+	for i, fv := range fn.FreeVars {
+		if fv.Parent() != fn {
+			s.errorf("FreeVar %s at index %d has wrong parent", fv.Name(), i)
+		}
+		s.checkReferrerList(fv)
+	}
+
+	if fn.Blocks != nil && len(fn.Blocks) == 0 {
+		// Function _had_ blocks (so it's not external) but
+		// they were "optimized" away, even the entry block.
+		s.errorf("Blocks slice is non-nil but empty")
+	}
+	for i, b := range fn.Blocks {
+		if b == nil {
+			s.warnf("nil *BasicBlock at f.Blocks[%d]", i)
+			continue
+		}
+		s.checkBlock(b, i)
+	}
+	if fn.Recover != nil && fn.Blocks[fn.Recover.Index] != fn.Recover {
+		s.errorf("Recover block is not in Blocks slice")
+	}
+
+	s.block = nil
+	for i, anon := range fn.AnonFuncs {
+		if anon.Parent() != fn {
+			s.errorf("AnonFuncs[%d]=%s but %s.Parent()=%s", i, anon, anon, anon.Parent())
+		}
+		if i != int(anon.anonIdx) {
+			s.errorf("AnonFuncs[%d]=%s but %s.anonIdx=%d", i, anon, anon, anon.anonIdx)
+		}
+	}
+	s.fn = nil
+	return !s.insane
+}
+
+// sanityCheckPackage checks invariants of packages upon creation.
+// It does not require that the package is built.
+// Unlike sanityCheck (for functions), it just panics at the first error.
+func sanityCheckPackage(pkg *Package) {
+	if pkg.Pkg == nil {
+		panic(fmt.Sprintf("Package %s has no Object", pkg))
+	}
+	_ = pkg.String() // must not crash
+
+	for name, mem := range pkg.Members {
+		if name != mem.Name() {
+			panic(fmt.Sprintf("%s: %T.Name() = %s, want %s",
+				pkg.Pkg.Path(), mem, mem.Name(), name))
+		}
+		obj := mem.Object()
+		if obj == nil {
+			// This check is sound because fields
+			// {Global,Function}.object have type
+			// types.Object.  (If they were declared as
+			// *types.{Var,Func}, we'd have a non-empty
+			// interface containing a nil pointer.)
+
+			continue // not all members have typechecker objects
+		}
+		if obj.Name() != name {
+			if obj.Name() == "init" && strings.HasPrefix(mem.Name(), "init#") {
+				// Ok.  The name of a declared init function varies between
+				// its types.Func ("init") and its ssa.Function ("init#%d").
+			} else {
+				panic(fmt.Sprintf("%s: %T.Object().Name() = %s, want %s",
+					pkg.Pkg.Path(), mem, obj.Name(), name))
+			}
+		}
+		if obj.Pos() != mem.Pos() {
+			panic(fmt.Sprintf("%s Pos=%d obj.Pos=%d", mem, mem.Pos(), obj.Pos()))
+		}
+	}
+}
diff --git a/vendor/golang.org/x/tools/go/ssa/source.go b/vendor/golang.org/x/tools/go/ssa/source.go
new file mode 100644
index 0000000..7b71c88
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ssa/source.go
@@ -0,0 +1,288 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// This file defines utilities for working with source positions
+// or source-level named entities ("objects").
+
+// TODO(adonovan): test that {Value,Instruction}.Pos() positions match
+// the originating syntax, as specified.
+
+import (
+	"go/ast"
+	"go/token"
+	"go/types"
+)
+
+// EnclosingFunction returns the function that contains the syntax
+// node denoted by path.
+//
+// Syntax associated with package-level variable specifications is
+// enclosed by the package's init() function.
+//
+// Returns nil if not found; reasons might include:
+//   - the node is not enclosed by any function.
+//   - the node is within an anonymous function (FuncLit) and
+//     its SSA function has not been created yet
+//     (pkg.Build() has not yet been called).
+func EnclosingFunction(pkg *Package, path []ast.Node) *Function {
+	// Start with package-level function...
+	fn := findEnclosingPackageLevelFunction(pkg, path)
+	if fn == nil {
+		return nil // not in any function
+	}
+
+	// ...then walk down the nested anonymous functions.
+	n := len(path)
+outer:
+	for i := range path {
+		if lit, ok := path[n-1-i].(*ast.FuncLit); ok {
+			for _, anon := range fn.AnonFuncs {
+				if anon.Pos() == lit.Type.Func {
+					fn = anon
+					continue outer
+				}
+			}
+			// SSA function not found:
+			// - package not yet built, or maybe
+			// - builder skipped FuncLit in dead block
+			//   (in principle; but currently the Builder
+			//   generates even dead FuncLits).
+			return nil
+		}
+	}
+	return fn
+}
+
+// HasEnclosingFunction returns true if the AST node denoted by path
+// is contained within the declaration of some function or
+// package-level variable.
+//
+// Unlike EnclosingFunction, the behaviour of this function does not
+// depend on whether SSA code for pkg has been built, so it can be
+// used to quickly reject check inputs that will cause
+// EnclosingFunction to fail, prior to SSA building.
+func HasEnclosingFunction(pkg *Package, path []ast.Node) bool {
+	return findEnclosingPackageLevelFunction(pkg, path) != nil
+}
+
+// findEnclosingPackageLevelFunction returns the Function
+// corresponding to the package-level function enclosing path.
+func findEnclosingPackageLevelFunction(pkg *Package, path []ast.Node) *Function {
+	if n := len(path); n >= 2 { // [... {Gen,Func}Decl File]
+		switch decl := path[n-2].(type) {
+		case *ast.GenDecl:
+			if decl.Tok == token.VAR && n >= 3 {
+				// Package-level 'var' initializer.
+				return pkg.init
+			}
+
+		case *ast.FuncDecl:
+			if decl.Recv == nil && decl.Name.Name == "init" {
+				// Explicit init() function.
+				for _, b := range pkg.init.Blocks {
+					for _, instr := range b.Instrs {
+						if instr, ok := instr.(*Call); ok {
+							if callee, ok := instr.Call.Value.(*Function); ok && callee.Pkg == pkg && callee.Pos() == decl.Name.NamePos {
+								return callee
+							}
+						}
+					}
+				}
+				// Hack: return non-nil when SSA is not yet
+				// built so that HasEnclosingFunction works.
+				return pkg.init
+			}
+			// Declared function/method.
+			return findNamedFunc(pkg, decl.Name.NamePos)
+		}
+	}
+	return nil // not in any function
+}
+
+// findNamedFunc returns the named function whose FuncDecl.Ident is at
+// position pos.
+func findNamedFunc(pkg *Package, pos token.Pos) *Function {
+	// Look at all package members and method sets of named types.
+	// Not very efficient.
+	for _, mem := range pkg.Members {
+		switch mem := mem.(type) {
+		case *Function:
+			if mem.Pos() == pos {
+				return mem
+			}
+		case *Type:
+			mset := pkg.Prog.MethodSets.MethodSet(types.NewPointer(mem.Type()))
+			for i, n := 0, mset.Len(); i < n; i++ {
+				// Don't call Program.Method: avoid creating wrappers.
+				obj := mset.At(i).Obj().(*types.Func)
+				if obj.Pos() == pos {
+					// obj from MethodSet may not be the origin type.
+					m := obj.Origin()
+					return pkg.objects[m].(*Function)
+				}
+			}
+		}
+	}
+	return nil
+}
+
+// ValueForExpr returns the SSA Value that corresponds to non-constant
+// expression e.
+//
+// It returns nil if no value was found, e.g.
+//   - the expression is not lexically contained within f;
+//   - f was not built with debug information; or
+//   - e is a constant expression.  (For efficiency, no debug
+//     information is stored for constants. Use
+//     go/types.Info.Types[e].Value instead.)
+//   - e is a reference to nil or a built-in function.
+//   - the value was optimised away.
+//
+// If e is an addressable expression used in an lvalue context,
+// value is the address denoted by e, and isAddr is true.
+//
+// The types of e (or &e, if isAddr) and the result are equal
+// (modulo "untyped" bools resulting from comparisons).
+//
+// (Tip: to find the ssa.Value given a source position, use
+// astutil.PathEnclosingInterval to locate the ast.Node, then
+// EnclosingFunction to locate the Function, then ValueForExpr to find
+// the ssa.Value.)
+func (f *Function) ValueForExpr(e ast.Expr) (value Value, isAddr bool) {
+	if f.debugInfo() { // (opt)
+		e = unparen(e)
+		for _, b := range f.Blocks {
+			for _, instr := range b.Instrs {
+				if ref, ok := instr.(*DebugRef); ok {
+					if ref.Expr == e {
+						return ref.X, ref.IsAddr
+					}
+				}
+			}
+		}
+	}
+	return
+}
+
+// --- Lookup functions for source-level named entities (types.Objects) ---
+
+// Package returns the SSA Package corresponding to the specified
+// type-checker package. It returns nil if no such Package was
+// created by a prior call to prog.CreatePackage.
+func (prog *Program) Package(pkg *types.Package) *Package {
+	return prog.packages[pkg]
+}
+
+// packageLevelMember returns the package-level member corresponding
+// to the specified symbol, which may be a package-level const
+// (*NamedConst), var (*Global) or func/method (*Function) of some
+// package in prog.
+//
+// It returns nil if the object belongs to a package that has not been
+// created by prog.CreatePackage.
+func (prog *Program) packageLevelMember(obj types.Object) Member {
+	if pkg, ok := prog.packages[obj.Pkg()]; ok {
+		return pkg.objects[obj]
+	}
+	return nil
+}
+
+// FuncValue returns the SSA function or (non-interface) method
+// denoted by the specified func symbol. It returns nil id the symbol
+// denotes an interface method, or belongs to a package that was not
+// created by prog.CreatePackage.
+func (prog *Program) FuncValue(obj *types.Func) *Function {
+	fn, _ := prog.packageLevelMember(obj).(*Function)
+	return fn
+}
+
+// ConstValue returns the SSA constant denoted by the specified const symbol.
+func (prog *Program) ConstValue(obj *types.Const) *Const {
+	// TODO(adonovan): opt: share (don't reallocate)
+	// Consts for const objects and constant ast.Exprs.
+
+	// Universal constant? {true,false,nil}
+	if obj.Parent() == types.Universe {
+		return NewConst(obj.Val(), obj.Type())
+	}
+	// Package-level named constant?
+	if v := prog.packageLevelMember(obj); v != nil {
+		return v.(*NamedConst).Value
+	}
+	return NewConst(obj.Val(), obj.Type())
+}
+
+// VarValue returns the SSA Value that corresponds to a specific
+// identifier denoting the specified var symbol.
+//
+// VarValue returns nil if a local variable was not found, perhaps
+// because its package was not built, the debug information was not
+// requested during SSA construction, or the value was optimized away.
+//
+// ref is the path to an ast.Ident (e.g. from PathEnclosingInterval),
+// and that ident must resolve to obj.
+//
+// pkg is the package enclosing the reference.  (A reference to a var
+// always occurs within a function, so we need to know where to find it.)
+//
+// If the identifier is a field selector and its base expression is
+// non-addressable, then VarValue returns the value of that field.
+// For example:
+//
+//	func f() struct {x int}
+//	f().x  // VarValue(x) returns a *Field instruction of type int
+//
+// All other identifiers denote addressable locations (variables).
+// For them, VarValue may return either the variable's address or its
+// value, even when the expression is evaluated only for its value; the
+// situation is reported by isAddr, the second component of the result.
+//
+// If !isAddr, the returned value is the one associated with the
+// specific identifier.  For example,
+//
+//	var x int    // VarValue(x) returns Const 0 here
+//	x = 1        // VarValue(x) returns Const 1 here
+//
+// It is not specified whether the value or the address is returned in
+// any particular case, as it may depend upon optimizations performed
+// during SSA code generation, such as registerization, constant
+// folding, avoidance of materialization of subexpressions, etc.
+func (prog *Program) VarValue(obj *types.Var, pkg *Package, ref []ast.Node) (value Value, isAddr bool) {
+	// All references to a var are local to some function, possibly init.
+	fn := EnclosingFunction(pkg, ref)
+	if fn == nil {
+		return // e.g. def of struct field; SSA not built?
+	}
+
+	id := ref[0].(*ast.Ident)
+
+	// Defining ident of a parameter?
+	if id.Pos() == obj.Pos() {
+		for _, param := range fn.Params {
+			if param.Object() == obj {
+				return param, false
+			}
+		}
+	}
+
+	// Other ident?
+	for _, b := range fn.Blocks {
+		for _, instr := range b.Instrs {
+			if dr, ok := instr.(*DebugRef); ok {
+				if dr.Pos() == id.Pos() {
+					return dr.X, dr.IsAddr
+				}
+			}
+		}
+	}
+
+	// Defining ident of package-level var?
+	if v := prog.packageLevelMember(obj); v != nil {
+		return v.(*Global), true
+	}
+
+	return // e.g. debug info not requested, or var optimized away
+}
diff --git a/vendor/golang.org/x/tools/go/ssa/ssa.go b/vendor/golang.org/x/tools/go/ssa/ssa.go
new file mode 100644
index 0000000..1231afd
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ssa/ssa.go
@@ -0,0 +1,1871 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// This package defines a high-level intermediate representation for
+// Go programs using static single-assignment (SSA) form.
+
+import (
+	"fmt"
+	"go/ast"
+	"go/constant"
+	"go/token"
+	"go/types"
+	"sync"
+
+	"golang.org/x/tools/go/types/typeutil"
+	"golang.org/x/tools/internal/typeparams"
+)
+
+// A Program is a partial or complete Go program converted to SSA form.
+type Program struct {
+	Fset       *token.FileSet              // position information for the files of this Program
+	imported   map[string]*Package         // all importable Packages, keyed by import path
+	packages   map[*types.Package]*Package // all created Packages
+	mode       BuilderMode                 // set of mode bits for SSA construction
+	MethodSets typeutil.MethodSetCache     // cache of type-checker's method-sets
+
+	canon *canonizer     // type canonicalization map
+	ctxt  *types.Context // cache for type checking instantiations
+
+	methodsMu  sync.Mutex
+	methodSets typeutil.Map // maps type to its concrete *methodSet
+
+	// memoization of whether a type refers to type parameters
+	hasParamsMu sync.Mutex
+	hasParams   typeparams.Free
+
+	runtimeTypesMu sync.Mutex
+	runtimeTypes   typeutil.Map // set of runtime types (from MakeInterface)
+
+	// objectMethods is a memoization of objectMethod
+	// to avoid creation of duplicate methods from type information.
+	objectMethodsMu sync.Mutex
+	objectMethods   map[*types.Func]*Function
+}
+
+// A Package is a single analyzed Go package containing Members for
+// all package-level functions, variables, constants and types it
+// declares.  These may be accessed directly via Members, or via the
+// type-specific accessor methods Func, Type, Var and Const.
+//
+// Members also contains entries for "init" (the synthetic package
+// initializer) and "init#%d", the nth declared init function,
+// and unspecified other things too.
+type Package struct {
+	Prog    *Program                // the owning program
+	Pkg     *types.Package          // the corresponding go/types.Package
+	Members map[string]Member       // all package members keyed by name (incl. init and init#%d)
+	objects map[types.Object]Member // mapping of package objects to members (incl. methods). Contains *NamedConst, *Global, *Function (values but not types)
+	init    *Function               // Func("init"); the package's init function
+	debug   bool                    // include full debug info in this package
+	syntax  bool                    // package was loaded from syntax
+
+	// The following fields are set transiently, then cleared
+	// after building.
+	buildOnce   sync.Once           // ensures package building occurs once
+	ninit       int32               // number of init functions
+	info        *types.Info         // package type information
+	files       []*ast.File         // package ASTs
+	created     []*Function         // members created as a result of building this package (includes declared functions, wrappers)
+	initVersion map[ast.Expr]string // goversion to use for each global var init expr
+}
+
+// A Member is a member of a Go package, implemented by *NamedConst,
+// *Global, *Function, or *Type; they are created by package-level
+// const, var, func and type declarations respectively.
+type Member interface {
+	Name() string                    // declared name of the package member
+	String() string                  // package-qualified name of the package member
+	RelString(*types.Package) string // like String, but relative refs are unqualified
+	Object() types.Object            // typechecker's object for this member, if any
+	Pos() token.Pos                  // position of member's declaration, if known
+	Type() types.Type                // type of the package member
+	Token() token.Token              // token.{VAR,FUNC,CONST,TYPE}
+	Package() *Package               // the containing package
+}
+
+// A Type is a Member of a Package representing a package-level named type.
+type Type struct {
+	object *types.TypeName
+	pkg    *Package
+}
+
+// A NamedConst is a Member of a Package representing a package-level
+// named constant.
+//
+// Pos() returns the position of the declaring ast.ValueSpec.Names[*]
+// identifier.
+//
+// NB: a NamedConst is not a Value; it contains a constant Value, which
+// it augments with the name and position of its 'const' declaration.
+type NamedConst struct {
+	object *types.Const
+	Value  *Const
+	pkg    *Package
+}
+
+// A Value is an SSA value that can be referenced by an instruction.
+type Value interface {
+	// Name returns the name of this value, and determines how
+	// this Value appears when used as an operand of an
+	// Instruction.
+	//
+	// This is the same as the source name for Parameters,
+	// Builtins, Functions, FreeVars, Globals.
+	// For constants, it is a representation of the constant's value
+	// and type.  For all other Values this is the name of the
+	// virtual register defined by the instruction.
+	//
+	// The name of an SSA Value is not semantically significant,
+	// and may not even be unique within a function.
+	Name() string
+
+	// If this value is an Instruction, String returns its
+	// disassembled form; otherwise it returns unspecified
+	// human-readable information about the Value, such as its
+	// kind, name and type.
+	String() string
+
+	// Type returns the type of this value.  Many instructions
+	// (e.g. IndexAddr) change their behaviour depending on the
+	// types of their operands.
+	Type() types.Type
+
+	// Parent returns the function to which this Value belongs.
+	// It returns nil for named Functions, Builtin, Const and Global.
+	Parent() *Function
+
+	// Referrers returns the list of instructions that have this
+	// value as one of their operands; it may contain duplicates
+	// if an instruction has a repeated operand.
+	//
+	// Referrers actually returns a pointer through which the
+	// caller may perform mutations to the object's state.
+	//
+	// Referrers is currently only defined if Parent()!=nil,
+	// i.e. for the function-local values FreeVar, Parameter,
+	// Functions (iff anonymous) and all value-defining instructions.
+	// It returns nil for named Functions, Builtin, Const and Global.
+	//
+	// Instruction.Operands contains the inverse of this relation.
+	Referrers() *[]Instruction
+
+	// Pos returns the location of the AST token most closely
+	// associated with the operation that gave rise to this value,
+	// or token.NoPos if it was not explicit in the source.
+	//
+	// For each ast.Node type, a particular token is designated as
+	// the closest location for the expression, e.g. the Lparen
+	// for an *ast.CallExpr.  This permits a compact but
+	// approximate mapping from Values to source positions for use
+	// in diagnostic messages, for example.
+	//
+	// (Do not use this position to determine which Value
+	// corresponds to an ast.Expr; use Function.ValueForExpr
+	// instead.  NB: it requires that the function was built with
+	// debug information.)
+	Pos() token.Pos
+}
+
+// An Instruction is an SSA instruction that computes a new Value or
+// has some effect.
+//
+// An Instruction that defines a value (e.g. BinOp) also implements
+// the Value interface; an Instruction that only has an effect (e.g. Store)
+// does not.
+type Instruction interface {
+	// String returns the disassembled form of this value.
+	//
+	// Examples of Instructions that are Values:
+	//       "x + y"     (BinOp)
+	//       "len([])"   (Call)
+	// Note that the name of the Value is not printed.
+	//
+	// Examples of Instructions that are not Values:
+	//       "return x"  (Return)
+	//       "*y = x"    (Store)
+	//
+	// (The separation Value.Name() from Value.String() is useful
+	// for some analyses which distinguish the operation from the
+	// value it defines, e.g., 'y = local int' is both an allocation
+	// of memory 'local int' and a definition of a pointer y.)
+	String() string
+
+	// Parent returns the function to which this instruction
+	// belongs.
+	Parent() *Function
+
+	// Block returns the basic block to which this instruction
+	// belongs.
+	Block() *BasicBlock
+
+	// setBlock sets the basic block to which this instruction belongs.
+	setBlock(*BasicBlock)
+
+	// Operands returns the operands of this instruction: the
+	// set of Values it references.
+	//
+	// Specifically, it appends their addresses to rands, a
+	// user-provided slice, and returns the resulting slice,
+	// permitting avoidance of memory allocation.
+	//
+	// The operands are appended in undefined order, but the order
+	// is consistent for a given Instruction; the addresses are
+	// always non-nil but may point to a nil Value.  Clients may
+	// store through the pointers, e.g. to effect a value
+	// renaming.
+	//
+	// Value.Referrers is a subset of the inverse of this
+	// relation.  (Referrers are not tracked for all types of
+	// Values.)
+	Operands(rands []*Value) []*Value
+
+	// Pos returns the location of the AST token most closely
+	// associated with the operation that gave rise to this
+	// instruction, or token.NoPos if it was not explicit in the
+	// source.
+	//
+	// For each ast.Node type, a particular token is designated as
+	// the closest location for the expression, e.g. the Go token
+	// for an *ast.GoStmt.  This permits a compact but approximate
+	// mapping from Instructions to source positions for use in
+	// diagnostic messages, for example.
+	//
+	// (Do not use this position to determine which Instruction
+	// corresponds to an ast.Expr; see the notes for Value.Pos.
+	// This position may be used to determine which non-Value
+	// Instruction corresponds to some ast.Stmts, but not all: If
+	// and Jump instructions have no Pos(), for example.)
+	Pos() token.Pos
+}
+
+// A Node is a node in the SSA value graph.  Every concrete type that
+// implements Node is also either a Value, an Instruction, or both.
+//
+// Node contains the methods common to Value and Instruction, plus the
+// Operands and Referrers methods generalized to return nil for
+// non-Instructions and non-Values, respectively.
+//
+// Node is provided to simplify SSA graph algorithms.  Clients should
+// use the more specific and informative Value or Instruction
+// interfaces where appropriate.
+type Node interface {
+	// Common methods:
+	String() string
+	Pos() token.Pos
+	Parent() *Function
+
+	// Partial methods:
+	Operands(rands []*Value) []*Value // nil for non-Instructions
+	Referrers() *[]Instruction        // nil for non-Values
+}
+
+// Function represents the parameters, results, and code of a function
+// or method.
+//
+// If Blocks is nil, this indicates an external function for which no
+// Go source code is available.  In this case, FreeVars, Locals, and
+// Params are nil too.  Clients performing whole-program analysis must
+// handle external functions specially.
+//
+// Blocks contains the function's control-flow graph (CFG).
+// Blocks[0] is the function entry point; block order is not otherwise
+// semantically significant, though it may affect the readability of
+// the disassembly.
+// To iterate over the blocks in dominance order, use DomPreorder().
+//
+// Recover is an optional second entry point to which control resumes
+// after a recovered panic.  The Recover block may contain only a return
+// statement, preceded by a load of the function's named return
+// parameters, if any.
+//
+// A nested function (Parent()!=nil) that refers to one or more
+// lexically enclosing local variables ("free variables") has FreeVars.
+// Such functions cannot be called directly but require a
+// value created by MakeClosure which, via its Bindings, supplies
+// values for these parameters.
+//
+// If the function is a method (Signature.Recv() != nil) then the first
+// element of Params is the receiver parameter.
+//
+// A Go package may declare many functions called "init".
+// For each one, Object().Name() returns "init" but Name() returns
+// "init#1", etc, in declaration order.
+//
+// Pos() returns the declaring ast.FuncLit.Type.Func or the position
+// of the ast.FuncDecl.Name, if the function was explicit in the
+// source. Synthetic wrappers, for which Synthetic != "", may share
+// the same position as the function they wrap.
+// Syntax.Pos() always returns the position of the declaring "func" token.
+//
+// When the operand of a range statement is an iterator function,
+// the loop body is transformed into a synthetic anonymous function
+// that is passed as the yield argument in a call to the iterator.
+// In that case, Function.Pos is the position of the "range" token,
+// and Function.Syntax is the ast.RangeStmt.
+//
+// Synthetic functions, for which Synthetic != "", are functions
+// that do not appear in the source AST. These include:
+//   - method wrappers,
+//   - thunks,
+//   - bound functions,
+//   - empty functions built from loaded type information,
+//   - yield functions created from range-over-func loops,
+//   - package init functions, and
+//   - instantiations of generic functions.
+//
+// Synthetic wrapper functions may share the same position
+// as the function they wrap.
+//
+// Type() returns the function's Signature.
+//
+// A generic function is a function or method that has uninstantiated type
+// parameters (TypeParams() != nil). Consider a hypothetical generic
+// method, (*Map[K,V]).Get. It may be instantiated with all
+// non-parameterized types as (*Map[string,int]).Get or with
+// parameterized types as (*Map[string,U]).Get, where U is a type parameter.
+// In both instantiations, Origin() refers to the instantiated generic
+// method, (*Map[K,V]).Get, TypeParams() refers to the parameters [K,V] of
+// the generic method. TypeArgs() refers to [string,U] or [string,int],
+// respectively, and is nil in the generic method.
+type Function struct {
+	name      string
+	object    *types.Func // symbol for declared function (nil for FuncLit or synthetic init)
+	method    *selection  // info about provenance of synthetic methods; thunk => non-nil
+	Signature *types.Signature
+	pos       token.Pos
+
+	// source information
+	Synthetic string      // provenance of synthetic function; "" for true source functions
+	syntax    ast.Node    // *ast.Func{Decl,Lit}, if from syntax (incl. generic instances) or (*ast.RangeStmt if a yield function)
+	info      *types.Info // type annotations (iff syntax != nil)
+	goversion string      // Go version of syntax (NB: init is special)
+
+	parent *Function // enclosing function if anon; nil if global
+	Pkg    *Package  // enclosing package; nil for shared funcs (wrappers and error.Error)
+	Prog   *Program  // enclosing program
+
+	buildshared *task // wait for a shared function to be done building (may be nil if <=1 builder ever needs to wait)
+
+	// These fields are populated only when the function body is built:
+
+	Params    []*Parameter  // function parameters; for methods, includes receiver
+	FreeVars  []*FreeVar    // free variables whose values must be supplied by closure
+	Locals    []*Alloc      // frame-allocated variables of this function
+	Blocks    []*BasicBlock // basic blocks of the function; nil => external
+	Recover   *BasicBlock   // optional; control transfers here after recovered panic
+	AnonFuncs []*Function   // anonymous functions (from FuncLit,RangeStmt) directly beneath this one
+	referrers []Instruction // referring instructions (iff Parent() != nil)
+	anonIdx   int32         // position of a nested function in parent's AnonFuncs. fn.Parent()!=nil => fn.Parent().AnonFunc[fn.anonIdx] == fn.
+
+	typeparams     *types.TypeParamList // type parameters of this function. typeparams.Len() > 0 => generic or instance of generic function
+	typeargs       []types.Type         // type arguments that instantiated typeparams. len(typeargs) > 0 => instance of generic function
+	topLevelOrigin *Function            // the origin function if this is an instance of a source function. nil if Parent()!=nil.
+	generic        *generic             // instances of this function, if generic
+
+	// The following fields are cleared after building.
+	build        buildFunc                // algorithm to build function body (nil => built)
+	currentBlock *BasicBlock              // where to emit code
+	vars         map[*types.Var]Value     // addresses of local variables
+	results      []*Alloc                 // result allocations of the current function
+	returnVars   []*types.Var             // variables for a return statement. Either results or for range-over-func a parent's results
+	targets      *targets                 // linked stack of branch targets
+	lblocks      map[*types.Label]*lblock // labelled blocks
+	subst        *subster                 // type parameter substitutions (if non-nil)
+	jump         *types.Var               // synthetic variable for the yield state (non-nil => range-over-func)
+	deferstack   *types.Var               // synthetic variable holding enclosing ssa:deferstack()
+	source       *Function                // nearest enclosing source function
+	exits        []*exit                  // exits of the function that need to be resolved
+	uniq         int64                    // source of unique ints within the source tree while building
+}
+
+// BasicBlock represents an SSA basic block.
+//
+// The final element of Instrs is always an explicit transfer of
+// control (If, Jump, Return, or Panic).
+//
+// A block may contain no Instructions only if it is unreachable,
+// i.e., Preds is nil.  Empty blocks are typically pruned.
+//
+// BasicBlocks and their Preds/Succs relation form a (possibly cyclic)
+// graph independent of the SSA Value graph: the control-flow graph or
+// CFG.  It is illegal for multiple edges to exist between the same
+// pair of blocks.
+//
+// Each BasicBlock is also a node in the dominator tree of the CFG.
+// The tree may be navigated using Idom()/Dominees() and queried using
+// Dominates().
+//
+// The order of Preds and Succs is significant (to Phi and If
+// instructions, respectively).
+type BasicBlock struct {
+	Index        int            // index of this block within Parent().Blocks
+	Comment      string         // optional label; no semantic significance
+	parent       *Function      // parent function
+	Instrs       []Instruction  // instructions in order
+	Preds, Succs []*BasicBlock  // predecessors and successors
+	succs2       [2]*BasicBlock // initial space for Succs
+	dom          domInfo        // dominator tree info
+	gaps         int            // number of nil Instrs (transient)
+	rundefers    int            // number of rundefers (transient)
+}
+
+// Pure values ----------------------------------------
+
+// A FreeVar represents a free variable of the function to which it
+// belongs.
+//
+// FreeVars are used to implement anonymous functions, whose free
+// variables are lexically captured in a closure formed by
+// MakeClosure.  The value of such a free var is an Alloc or another
+// FreeVar and is considered a potentially escaping heap address, with
+// pointer type.
+//
+// FreeVars are also used to implement bound method closures.  Such a
+// free var represents the receiver value and may be of any type that
+// has concrete methods.
+//
+// Pos() returns the position of the value that was captured, which
+// belongs to an enclosing function.
+type FreeVar struct {
+	name      string
+	typ       types.Type
+	pos       token.Pos
+	parent    *Function
+	referrers []Instruction
+
+	// Transiently needed during building.
+	outer Value // the Value captured from the enclosing context.
+}
+
+// A Parameter represents an input parameter of a function.
+type Parameter struct {
+	name      string
+	object    *types.Var // non-nil
+	typ       types.Type
+	parent    *Function
+	referrers []Instruction
+}
+
+// A Const represents a value known at build time.
+//
+// Consts include true constants of boolean, numeric, and string types, as
+// defined by the Go spec; these are represented by a non-nil Value field.
+//
+// Consts also include the "zero" value of any type, of which the nil values
+// of various pointer-like types are a special case; these are represented
+// by a nil Value field.
+//
+// Pos() returns token.NoPos.
+//
+// Example printed forms:
+//
+//		42:int
+//		"hello":untyped string
+//		3+4i:MyComplex
+//		nil:*int
+//		nil:[]string
+//		[3]int{}:[3]int
+//		struct{x string}{}:struct{x string}
+//	    0:interface{int|int64}
+//	    nil:interface{bool|int} // no go/constant representation
+type Const struct {
+	typ   types.Type
+	Value constant.Value
+}
+
+// A Global is a named Value holding the address of a package-level
+// variable.
+//
+// Pos() returns the position of the ast.ValueSpec.Names[*]
+// identifier.
+type Global struct {
+	name   string
+	object types.Object // a *types.Var; may be nil for synthetics e.g. init$guard
+	typ    types.Type
+	pos    token.Pos
+
+	Pkg *Package
+}
+
+// A Builtin represents a specific use of a built-in function, e.g. len.
+//
+// Builtins are immutable values.  Builtins do not have addresses.
+// Builtins can only appear in CallCommon.Value.
+//
+// Name() indicates the function: one of the built-in functions from the
+// Go spec (excluding "make" and "new") or one of these ssa-defined
+// intrinsics:
+//
+//	// wrapnilchk returns ptr if non-nil, panics otherwise.
+//	// (For use in indirection wrappers.)
+//	func ssa:wrapnilchk(ptr *T, recvType, methodName string) *T
+//
+// Object() returns a *types.Builtin for built-ins defined by the spec,
+// nil for others.
+//
+// Type() returns a *types.Signature representing the effective
+// signature of the built-in for this call.
+type Builtin struct {
+	name string
+	sig  *types.Signature
+}
+
+// Value-defining instructions  ----------------------------------------
+
+// The Alloc instruction reserves space for a variable of the given type,
+// zero-initializes it, and yields its address.
+//
+// Alloc values are always addresses, and have pointer types, so the
+// type of the allocated variable is actually
+// Type().Underlying().(*types.Pointer).Elem().
+//
+// If Heap is false, Alloc zero-initializes the same local variable in
+// the call frame and returns its address; in this case the Alloc must
+// be present in Function.Locals. We call this a "local" alloc.
+//
+// If Heap is true, Alloc allocates a new zero-initialized variable
+// each time the instruction is executed. We call this a "new" alloc.
+//
+// When Alloc is applied to a channel, map or slice type, it returns
+// the address of an uninitialized (nil) reference of that kind; store
+// the result of MakeSlice, MakeMap or MakeChan in that location to
+// instantiate these types.
+//
+// Pos() returns the ast.CompositeLit.Lbrace for a composite literal,
+// or the ast.CallExpr.Rparen for a call to new() or for a call that
+// allocates a varargs slice.
+//
+// Example printed form:
+//
+//	t0 = local int
+//	t1 = new int
+type Alloc struct {
+	register
+	Comment string
+	Heap    bool
+	index   int // dense numbering; for lifting
+}
+
+// The Phi instruction represents an SSA φ-node, which combines values
+// that differ across incoming control-flow edges and yields a new
+// value.  Within a block, all φ-nodes must appear before all non-φ
+// nodes.
+//
+// Pos() returns the position of the && or || for short-circuit
+// control-flow joins, or that of the *Alloc for φ-nodes inserted
+// during SSA renaming.
+//
+// Example printed form:
+//
+//	t2 = phi [0: t0, 1: t1]
+type Phi struct {
+	register
+	Comment string  // a hint as to its purpose
+	Edges   []Value // Edges[i] is value for Block().Preds[i]
+}
+
+// The Call instruction represents a function or method call.
+//
+// The Call instruction yields the function result if there is exactly
+// one.  Otherwise it returns a tuple, the components of which are
+// accessed via Extract.
+//
+// See CallCommon for generic function call documentation.
+//
+// Pos() returns the ast.CallExpr.Lparen, if explicit in the source.
+//
+// Example printed form:
+//
+//	t2 = println(t0, t1)
+//	t4 = t3()
+//	t7 = invoke t5.Println(...t6)
+type Call struct {
+	register
+	Call CallCommon
+}
+
+// The BinOp instruction yields the result of binary operation X Op Y.
+//
+// Pos() returns the ast.BinaryExpr.OpPos, if explicit in the source.
+//
+// Example printed form:
+//
+//	t1 = t0 + 1:int
+type BinOp struct {
+	register
+	// One of:
+	// ADD SUB MUL QUO REM          + - * / %
+	// AND OR XOR SHL SHR AND_NOT   & | ^ << >> &^
+	// EQL NEQ LSS LEQ GTR GEQ      == != < <= < >=
+	Op   token.Token
+	X, Y Value
+}
+
+// The UnOp instruction yields the result of Op X.
+// ARROW is channel receive.
+// MUL is pointer indirection (load).
+// XOR is bitwise complement.
+// SUB is negation.
+// NOT is logical negation.
+//
+// If CommaOk and Op=ARROW, the result is a 2-tuple of the value above
+// and a boolean indicating the success of the receive.  The
+// components of the tuple are accessed using Extract.
+//
+// Pos() returns the ast.UnaryExpr.OpPos, if explicit in the source.
+// For receive operations (ARROW) implicit in ranging over a channel,
+// Pos() returns the ast.RangeStmt.For.
+// For implicit memory loads (STAR), Pos() returns the position of the
+// most closely associated source-level construct; the details are not
+// specified.
+//
+// Example printed form:
+//
+//	t0 = *x
+//	t2 = <-t1,ok
+type UnOp struct {
+	register
+	Op      token.Token // One of: NOT SUB ARROW MUL XOR ! - <- * ^
+	X       Value
+	CommaOk bool
+}
+
+// The ChangeType instruction applies to X a value-preserving type
+// change to Type().
+//
+// Type changes are permitted:
+//   - between a named type and its underlying type.
+//   - between two named types of the same underlying type.
+//   - between (possibly named) pointers to identical base types.
+//   - from a bidirectional channel to a read- or write-channel,
+//     optionally adding/removing a name.
+//   - between a type (t) and an instance of the type (tσ), i.e.
+//     Type() == σ(X.Type()) (or X.Type()== σ(Type())) where
+//     σ is the type substitution of Parent().TypeParams by
+//     Parent().TypeArgs.
+//
+// This operation cannot fail dynamically.
+//
+// Type changes may to be to or from a type parameter (or both). All
+// types in the type set of X.Type() have a value-preserving type
+// change to all types in the type set of Type().
+//
+// Pos() returns the ast.CallExpr.Lparen, if the instruction arose
+// from an explicit conversion in the source.
+//
+// Example printed form:
+//
+//	t1 = changetype *int <- IntPtr (t0)
+type ChangeType struct {
+	register
+	X Value
+}
+
+// The Convert instruction yields the conversion of value X to type
+// Type().  One or both of those types is basic (but possibly named).
+//
+// A conversion may change the value and representation of its operand.
+// Conversions are permitted:
+//   - between real numeric types.
+//   - between complex numeric types.
+//   - between string and []byte or []rune.
+//   - between pointers and unsafe.Pointer.
+//   - between unsafe.Pointer and uintptr.
+//   - from (Unicode) integer to (UTF-8) string.
+//
+// A conversion may imply a type name change also.
+//
+// Conversions may to be to or from a type parameter. All types in
+// the type set of X.Type() can be converted to all types in the type
+// set of Type().
+//
+// This operation cannot fail dynamically.
+//
+// Conversions of untyped string/number/bool constants to a specific
+// representation are eliminated during SSA construction.
+//
+// Pos() returns the ast.CallExpr.Lparen, if the instruction arose
+// from an explicit conversion in the source.
+//
+// Example printed form:
+//
+//	t1 = convert []byte <- string (t0)
+type Convert struct {
+	register
+	X Value
+}
+
+// The MultiConvert instruction yields the conversion of value X to type
+// Type(). Either X.Type() or Type() must be a type parameter. Each
+// type in the type set of X.Type() can be converted to each type in the
+// type set of Type().
+//
+// See the documentation for Convert, ChangeType, and SliceToArrayPointer
+// for the conversions that are permitted. Additionally conversions of
+// slices to arrays are permitted.
+//
+// This operation can fail dynamically (see SliceToArrayPointer).
+//
+// Pos() returns the ast.CallExpr.Lparen, if the instruction arose
+// from an explicit conversion in the source.
+//
+// Example printed form:
+//
+//	t1 = multiconvert D <- S (t0) [*[2]rune <- []rune | string <- []rune]
+type MultiConvert struct {
+	register
+	X    Value
+	from []*types.Term
+	to   []*types.Term
+}
+
+// ChangeInterface constructs a value of one interface type from a
+// value of another interface type known to be assignable to it.
+// This operation cannot fail.
+//
+// Pos() returns the ast.CallExpr.Lparen if the instruction arose from
+// an explicit T(e) conversion; the ast.TypeAssertExpr.Lparen if the
+// instruction arose from an explicit e.(T) operation; or token.NoPos
+// otherwise.
+//
+// Example printed form:
+//
+//	t1 = change interface interface{} <- I (t0)
+type ChangeInterface struct {
+	register
+	X Value
+}
+
+// The SliceToArrayPointer instruction yields the conversion of slice X to
+// array pointer.
+//
+// Pos() returns the ast.CallExpr.Lparen, if the instruction arose
+// from an explicit conversion in the source.
+//
+// Conversion may to be to or from a type parameter. All types in
+// the type set of X.Type() must be a slice types that can be converted to
+// all types in the type set of Type() which must all be pointer to array
+// types.
+//
+// This operation can fail dynamically if the length of the slice is less
+// than the length of the array.
+//
+// Example printed form:
+//
+//	t1 = slice to array pointer *[4]byte <- []byte (t0)
+type SliceToArrayPointer struct {
+	register
+	X Value
+}
+
+// MakeInterface constructs an instance of an interface type from a
+// value of a concrete type.
+//
+// Use Program.MethodSets.MethodSet(X.Type()) to find the method-set
+// of X, and Program.MethodValue(m) to find the implementation of a method.
+//
+// To construct the zero value of an interface type T, use:
+//
+//	NewConst(constant.MakeNil(), T, pos)
+//
+// Pos() returns the ast.CallExpr.Lparen, if the instruction arose
+// from an explicit conversion in the source.
+//
+// Example printed form:
+//
+//	t1 = make interface{} <- int (42:int)
+//	t2 = make Stringer <- t0
+type MakeInterface struct {
+	register
+	X Value
+}
+
+// The MakeClosure instruction yields a closure value whose code is
+// Fn and whose free variables' values are supplied by Bindings.
+//
+// Type() returns a (possibly named) *types.Signature.
+//
+// Pos() returns the ast.FuncLit.Type.Func for a function literal
+// closure or the ast.SelectorExpr.Sel for a bound method closure.
+//
+// Example printed form:
+//
+//	t0 = make closure anon@1.2 [x y z]
+//	t1 = make closure bound$(main.I).add [i]
+type MakeClosure struct {
+	register
+	Fn       Value   // always a *Function
+	Bindings []Value // values for each free variable in Fn.FreeVars
+}
+
+// The MakeMap instruction creates a new hash-table-based map object
+// and yields a value of kind map.
+//
+// Type() returns a (possibly named) *types.Map.
+//
+// Pos() returns the ast.CallExpr.Lparen, if created by make(map), or
+// the ast.CompositeLit.Lbrack if created by a literal.
+//
+// Example printed form:
+//
+//	t1 = make map[string]int t0
+//	t1 = make StringIntMap t0
+type MakeMap struct {
+	register
+	Reserve Value // initial space reservation; nil => default
+}
+
+// The MakeChan instruction creates a new channel object and yields a
+// value of kind chan.
+//
+// Type() returns a (possibly named) *types.Chan.
+//
+// Pos() returns the ast.CallExpr.Lparen for the make(chan) that
+// created it.
+//
+// Example printed form:
+//
+//	t0 = make chan int 0
+//	t0 = make IntChan 0
+type MakeChan struct {
+	register
+	Size Value // int; size of buffer; zero => synchronous.
+}
+
+// The MakeSlice instruction yields a slice of length Len backed by a
+// newly allocated array of length Cap.
+//
+// Both Len and Cap must be non-nil Values of integer type.
+//
+// (Alloc(types.Array) followed by Slice will not suffice because
+// Alloc can only create arrays of constant length.)
+//
+// Type() returns a (possibly named) *types.Slice.
+//
+// Pos() returns the ast.CallExpr.Lparen for the make([]T) that
+// created it.
+//
+// Example printed form:
+//
+//	t1 = make []string 1:int t0
+//	t1 = make StringSlice 1:int t0
+type MakeSlice struct {
+	register
+	Len Value
+	Cap Value
+}
+
+// The Slice instruction yields a slice of an existing string, slice
+// or *array X between optional integer bounds Low and High.
+//
+// Dynamically, this instruction panics if X evaluates to a nil *array
+// pointer.
+//
+// Type() returns string if the type of X was string, otherwise a
+// *types.Slice with the same element type as X.
+//
+// Pos() returns the ast.SliceExpr.Lbrack if created by a x[:] slice
+// operation, the ast.CompositeLit.Lbrace if created by a literal, or
+// NoPos if not explicit in the source (e.g. a variadic argument slice).
+//
+// Example printed form:
+//
+//	t1 = slice t0[1:]
+type Slice struct {
+	register
+	X              Value // slice, string, or *array
+	Low, High, Max Value // each may be nil
+}
+
+// The FieldAddr instruction yields the address of Field of *struct X.
+//
+// The field is identified by its index within the field list of the
+// struct type of X.
+//
+// Dynamically, this instruction panics if X evaluates to a nil
+// pointer.
+//
+// Type() returns a (possibly named) *types.Pointer.
+//
+// Pos() returns the position of the ast.SelectorExpr.Sel for the
+// field, if explicit in the source. For implicit selections, returns
+// the position of the inducing explicit selection. If produced for a
+// struct literal S{f: e}, it returns the position of the colon; for
+// S{e} it returns the start of expression e.
+//
+// Example printed form:
+//
+//	t1 = &t0.name [#1]
+type FieldAddr struct {
+	register
+	X     Value // *struct
+	Field int   // index into CoreType(CoreType(X.Type()).(*types.Pointer).Elem()).(*types.Struct).Fields
+}
+
+// The Field instruction yields the Field of struct X.
+//
+// The field is identified by its index within the field list of the
+// struct type of X; by using numeric indices we avoid ambiguity of
+// package-local identifiers and permit compact representations.
+//
+// Pos() returns the position of the ast.SelectorExpr.Sel for the
+// field, if explicit in the source. For implicit selections, returns
+// the position of the inducing explicit selection.
+
+// Example printed form:
+//
+//	t1 = t0.name [#1]
+type Field struct {
+	register
+	X     Value // struct
+	Field int   // index into CoreType(X.Type()).(*types.Struct).Fields
+}
+
+// The IndexAddr instruction yields the address of the element at
+// index Index of collection X.  Index is an integer expression.
+//
+// The elements of maps and strings are not addressable; use Lookup (map),
+// Index (string), or MapUpdate instead.
+//
+// Dynamically, this instruction panics if X evaluates to a nil *array
+// pointer.
+//
+// Type() returns a (possibly named) *types.Pointer.
+//
+// Pos() returns the ast.IndexExpr.Lbrack for the index operation, if
+// explicit in the source.
+//
+// Example printed form:
+//
+//	t2 = &t0[t1]
+type IndexAddr struct {
+	register
+	X     Value // *array, slice or type parameter with types array, *array, or slice.
+	Index Value // numeric index
+}
+
+// The Index instruction yields element Index of collection X, an array,
+// string or type parameter containing an array, a string, a pointer to an,
+// array or a slice.
+//
+// Pos() returns the ast.IndexExpr.Lbrack for the index operation, if
+// explicit in the source.
+//
+// Example printed form:
+//
+//	t2 = t0[t1]
+type Index struct {
+	register
+	X     Value // array, string or type parameter with types array, *array, slice, or string.
+	Index Value // integer index
+}
+
+// The Lookup instruction yields element Index of collection map X.
+// Index is the appropriate key type.
+//
+// If CommaOk, the result is a 2-tuple of the value above and a
+// boolean indicating the result of a map membership test for the key.
+// The components of the tuple are accessed using Extract.
+//
+// Pos() returns the ast.IndexExpr.Lbrack, if explicit in the source.
+//
+// Example printed form:
+//
+//	t2 = t0[t1]
+//	t5 = t3[t4],ok
+type Lookup struct {
+	register
+	X       Value // map
+	Index   Value // key-typed index
+	CommaOk bool  // return a value,ok pair
+}
+
+// SelectState is a helper for Select.
+// It represents one goal state and its corresponding communication.
+type SelectState struct {
+	Dir       types.ChanDir // direction of case (SendOnly or RecvOnly)
+	Chan      Value         // channel to use (for send or receive)
+	Send      Value         // value to send (for send)
+	Pos       token.Pos     // position of token.ARROW
+	DebugNode ast.Node      // ast.SendStmt or ast.UnaryExpr(<-) [debug mode]
+}
+
+// The Select instruction tests whether (or blocks until) one
+// of the specified sent or received states is entered.
+//
+// Let n be the number of States for which Dir==RECV and T_i (0<=i<n)
+// be the element type of each such state's Chan.
+// Select returns an n+2-tuple
+//
+//	(index int, recvOk bool, r_0 T_0, ... r_n-1 T_n-1)
+//
+// The tuple's components, described below, must be accessed via the
+// Extract instruction.
+//
+// If Blocking, select waits until exactly one state holds, i.e. a
+// channel becomes ready for the designated operation of sending or
+// receiving; select chooses one among the ready states
+// pseudorandomly, performs the send or receive operation, and sets
+// 'index' to the index of the chosen channel.
+//
+// If !Blocking, select doesn't block if no states hold; instead it
+// returns immediately with index equal to -1.
+//
+// If the chosen channel was used for a receive, the r_i component is
+// set to the received value, where i is the index of that state among
+// all n receive states; otherwise r_i has the zero value of type T_i.
+// Note that the receive index i is not the same as the state
+// index index.
+//
+// The second component of the triple, recvOk, is a boolean whose value
+// is true iff the selected operation was a receive and the receive
+// successfully yielded a value.
+//
+// Pos() returns the ast.SelectStmt.Select.
+//
+// Example printed form:
+//
+//	t3 = select nonblocking [<-t0, t1<-t2]
+//	t4 = select blocking []
+type Select struct {
+	register
+	States   []*SelectState
+	Blocking bool
+}
+
+// The Range instruction yields an iterator over the domain and range
+// of X, which must be a string or map.
+//
+// Elements are accessed via Next.
+//
+// Type() returns an opaque and degenerate "rangeIter" type.
+//
+// Pos() returns the ast.RangeStmt.For.
+//
+// Example printed form:
+//
+//	t0 = range "hello":string
+type Range struct {
+	register
+	X Value // string or map
+}
+
+// The Next instruction reads and advances the (map or string)
+// iterator Iter and returns a 3-tuple value (ok, k, v).  If the
+// iterator is not exhausted, ok is true and k and v are the next
+// elements of the domain and range, respectively.  Otherwise ok is
+// false and k and v are undefined.
+//
+// Components of the tuple are accessed using Extract.
+//
+// The IsString field distinguishes iterators over strings from those
+// over maps, as the Type() alone is insufficient: consider
+// map[int]rune.
+//
+// Type() returns a *types.Tuple for the triple (ok, k, v).
+// The types of k and/or v may be types.Invalid.
+//
+// Example printed form:
+//
+//	t1 = next t0
+type Next struct {
+	register
+	Iter     Value
+	IsString bool // true => string iterator; false => map iterator.
+}
+
+// The TypeAssert instruction tests whether interface value X has type
+// AssertedType.
+//
+// If !CommaOk, on success it returns v, the result of the conversion
+// (defined below); on failure it panics.
+//
+// If CommaOk: on success it returns a pair (v, true) where v is the
+// result of the conversion; on failure it returns (z, false) where z
+// is AssertedType's zero value.  The components of the pair must be
+// accessed using the Extract instruction.
+//
+// If Underlying: tests whether interface value X has the underlying
+// type AssertedType.
+//
+// If AssertedType is a concrete type, TypeAssert checks whether the
+// dynamic type in interface X is equal to it, and if so, the result
+// of the conversion is a copy of the value in the interface.
+//
+// If AssertedType is an interface, TypeAssert checks whether the
+// dynamic type of the interface is assignable to it, and if so, the
+// result of the conversion is a copy of the interface value X.
+// If AssertedType is a superinterface of X.Type(), the operation will
+// fail iff the operand is nil.  (Contrast with ChangeInterface, which
+// performs no nil-check.)
+//
+// Type() reflects the actual type of the result, possibly a
+// 2-types.Tuple; AssertedType is the asserted type.
+//
+// Depending on the TypeAssert's purpose, Pos may return:
+//   - the ast.CallExpr.Lparen of an explicit T(e) conversion;
+//   - the ast.TypeAssertExpr.Lparen of an explicit e.(T) operation;
+//   - the ast.CaseClause.Case of a case of a type-switch statement;
+//   - the Ident(m).NamePos of an interface method value i.m
+//     (for which TypeAssert may be used to effect the nil check).
+//
+// Example printed form:
+//
+//	t1 = typeassert t0.(int)
+//	t3 = typeassert,ok t2.(T)
+type TypeAssert struct {
+	register
+	X            Value
+	AssertedType types.Type
+	CommaOk      bool
+}
+
+// The Extract instruction yields component Index of Tuple.
+//
+// This is used to access the results of instructions with multiple
+// return values, such as Call, TypeAssert, Next, UnOp(ARROW) and
+// IndexExpr(Map).
+//
+// Example printed form:
+//
+//	t1 = extract t0 #1
+type Extract struct {
+	register
+	Tuple Value
+	Index int
+}
+
+// Instructions executed for effect.  They do not yield a value. --------------------
+
+// The Jump instruction transfers control to the sole successor of its
+// owning block.
+//
+// A Jump must be the last instruction of its containing BasicBlock.
+//
+// Pos() returns NoPos.
+//
+// Example printed form:
+//
+//	jump done
+type Jump struct {
+	anInstruction
+}
+
+// The If instruction transfers control to one of the two successors
+// of its owning block, depending on the boolean Cond: the first if
+// true, the second if false.
+//
+// An If instruction must be the last instruction of its containing
+// BasicBlock.
+//
+// Pos() returns NoPos.
+//
+// Example printed form:
+//
+//	if t0 goto done else body
+type If struct {
+	anInstruction
+	Cond Value
+}
+
+// The Return instruction returns values and control back to the calling
+// function.
+//
+// len(Results) is always equal to the number of results in the
+// function's signature.
+//
+// If len(Results) > 1, Return returns a tuple value with the specified
+// components which the caller must access using Extract instructions.
+//
+// There is no instruction to return a ready-made tuple like those
+// returned by a "value,ok"-mode TypeAssert, Lookup or UnOp(ARROW) or
+// a tail-call to a function with multiple result parameters.
+//
+// Return must be the last instruction of its containing BasicBlock.
+// Such a block has no successors.
+//
+// Pos() returns the ast.ReturnStmt.Return, if explicit in the source.
+//
+// Example printed form:
+//
+//	return
+//	return nil:I, 2:int
+type Return struct {
+	anInstruction
+	Results []Value
+	pos     token.Pos
+}
+
+// The RunDefers instruction pops and invokes the entire stack of
+// procedure calls pushed by Defer instructions in this function.
+//
+// It is legal to encounter multiple 'rundefers' instructions in a
+// single control-flow path through a function; this is useful in
+// the combined init() function, for example.
+//
+// Pos() returns NoPos.
+//
+// Example printed form:
+//
+//	rundefers
+type RunDefers struct {
+	anInstruction
+}
+
+// The Panic instruction initiates a panic with value X.
+//
+// A Panic instruction must be the last instruction of its containing
+// BasicBlock, which must have no successors.
+//
+// NB: 'go panic(x)' and 'defer panic(x)' do not use this instruction;
+// they are treated as calls to a built-in function.
+//
+// Pos() returns the ast.CallExpr.Lparen if this panic was explicit
+// in the source.
+//
+// Example printed form:
+//
+//	panic t0
+type Panic struct {
+	anInstruction
+	X   Value // an interface{}
+	pos token.Pos
+}
+
+// The Go instruction creates a new goroutine and calls the specified
+// function within it.
+//
+// See CallCommon for generic function call documentation.
+//
+// Pos() returns the ast.GoStmt.Go.
+//
+// Example printed form:
+//
+//	go println(t0, t1)
+//	go t3()
+//	go invoke t5.Println(...t6)
+type Go struct {
+	anInstruction
+	Call CallCommon
+	pos  token.Pos
+}
+
+// The Defer instruction pushes the specified call onto a stack of
+// functions to be called by a RunDefers instruction or by a panic.
+//
+// If DeferStack != nil, it indicates the defer list that the defer is
+// added to. Defer list values come from the Builtin function
+// ssa:deferstack. Calls to ssa:deferstack() produces the defer stack
+// of the current function frame. DeferStack allows for deferring into an
+// alternative function stack than the current function.
+//
+// See CallCommon for generic function call documentation.
+//
+// Pos() returns the ast.DeferStmt.Defer.
+//
+// Example printed form:
+//
+//	defer println(t0, t1)
+//	defer t3()
+//	defer invoke t5.Println(...t6)
+type Defer struct {
+	anInstruction
+	Call       CallCommon
+	DeferStack Value // stack of deferred functions (from ssa:deferstack() intrinsic) onto which this function is pushed
+	pos        token.Pos
+}
+
+// The Send instruction sends X on channel Chan.
+//
+// Pos() returns the ast.SendStmt.Arrow, if explicit in the source.
+//
+// Example printed form:
+//
+//	send t0 <- t1
+type Send struct {
+	anInstruction
+	Chan, X Value
+	pos     token.Pos
+}
+
+// The Store instruction stores Val at address Addr.
+// Stores can be of arbitrary types.
+//
+// Pos() returns the position of the source-level construct most closely
+// associated with the memory store operation.
+// Since implicit memory stores are numerous and varied and depend upon
+// implementation choices, the details are not specified.
+//
+// Example printed form:
+//
+//	*x = y
+type Store struct {
+	anInstruction
+	Addr Value
+	Val  Value
+	pos  token.Pos
+}
+
+// The MapUpdate instruction updates the association of Map[Key] to
+// Value.
+//
+// Pos() returns the ast.KeyValueExpr.Colon or ast.IndexExpr.Lbrack,
+// if explicit in the source.
+//
+// Example printed form:
+//
+//	t0[t1] = t2
+type MapUpdate struct {
+	anInstruction
+	Map   Value
+	Key   Value
+	Value Value
+	pos   token.Pos
+}
+
+// A DebugRef instruction maps a source-level expression Expr to the
+// SSA value X that represents the value (!IsAddr) or address (IsAddr)
+// of that expression.
+//
+// DebugRef is a pseudo-instruction: it has no dynamic effect.
+//
+// Pos() returns Expr.Pos(), the start position of the source-level
+// expression.  This is not the same as the "designated" token as
+// documented at Value.Pos(). e.g. CallExpr.Pos() does not return the
+// position of the ("designated") Lparen token.
+//
+// If Expr is an *ast.Ident denoting a var or func, Object() returns
+// the object; though this information can be obtained from the type
+// checker, including it here greatly facilitates debugging.
+// For non-Ident expressions, Object() returns nil.
+//
+// DebugRefs are generated only for functions built with debugging
+// enabled; see Package.SetDebugMode() and the GlobalDebug builder
+// mode flag.
+//
+// DebugRefs are not emitted for ast.Idents referring to constants or
+// predeclared identifiers, since they are trivial and numerous.
+// Nor are they emitted for ast.ParenExprs.
+//
+// (By representing these as instructions, rather than out-of-band,
+// consistency is maintained during transformation passes by the
+// ordinary SSA renaming machinery.)
+//
+// Example printed form:
+//
+//	; *ast.CallExpr @ 102:9 is t5
+//	; var x float64 @ 109:72 is x
+//	; address of *ast.CompositeLit @ 216:10 is t0
+type DebugRef struct {
+	// TODO(generics): Reconsider what DebugRefs are for generics.
+	anInstruction
+	Expr   ast.Expr     // the referring expression (never *ast.ParenExpr)
+	object types.Object // the identity of the source var/func
+	IsAddr bool         // Expr is addressable and X is the address it denotes
+	X      Value        // the value or address of Expr
+}
+
+// Embeddable mix-ins and helpers for common parts of other structs. -----------
+
+// register is a mix-in embedded by all SSA values that are also
+// instructions, i.e. virtual registers, and provides a uniform
+// implementation of most of the Value interface: Value.Name() is a
+// numbered register (e.g. "t0"); the other methods are field accessors.
+//
+// Temporary names are automatically assigned to each register on
+// completion of building a function in SSA form.
+//
+// Clients must not assume that the 'id' value (and the Name() derived
+// from it) is unique within a function.  As always in this API,
+// semantics are determined only by identity; names exist only to
+// facilitate debugging.
+type register struct {
+	anInstruction
+	num       int        // "name" of virtual register, e.g. "t0".  Not guaranteed unique.
+	typ       types.Type // type of virtual register
+	pos       token.Pos  // position of source expression, or NoPos
+	referrers []Instruction
+}
+
+// anInstruction is a mix-in embedded by all Instructions.
+// It provides the implementations of the Block and setBlock methods.
+type anInstruction struct {
+	block *BasicBlock // the basic block of this instruction
+}
+
+// CallCommon is contained by Go, Defer and Call to hold the
+// common parts of a function or method call.
+//
+// Each CallCommon exists in one of two modes, function call and
+// interface method invocation, or "call" and "invoke" for short.
+//
+// 1. "call" mode: when Method is nil (!IsInvoke), a CallCommon
+// represents an ordinary function call of the value in Value,
+// which may be a *Builtin, a *Function or any other value of kind
+// 'func'.
+//
+// Value may be one of:
+//
+//	(a) a *Function, indicating a statically dispatched call
+//	    to a package-level function, an anonymous function, or
+//	    a method of a named type.
+//	(b) a *MakeClosure, indicating an immediately applied
+//	    function literal with free variables.
+//	(c) a *Builtin, indicating a statically dispatched call
+//	    to a built-in function.
+//	(d) any other value, indicating a dynamically dispatched
+//	    function call.
+//
+// StaticCallee returns the identity of the callee in cases
+// (a) and (b), nil otherwise.
+//
+// Args contains the arguments to the call.  If Value is a method,
+// Args[0] contains the receiver parameter.
+//
+// Example printed form:
+//
+//	t2 = println(t0, t1)
+//	go t3()
+//	defer t5(...t6)
+//
+// 2. "invoke" mode: when Method is non-nil (IsInvoke), a CallCommon
+// represents a dynamically dispatched call to an interface method.
+// In this mode, Value is the interface value and Method is the
+// interface's abstract method. The interface value may be a type
+// parameter. Note: an interface method may be shared by multiple
+// interfaces due to embedding; Value.Type() provides the specific
+// interface used for this call.
+//
+// Value is implicitly supplied to the concrete method implementation
+// as the receiver parameter; in other words, Args[0] holds not the
+// receiver but the first true argument.
+//
+// Example printed form:
+//
+//	t1 = invoke t0.String()
+//	go invoke t3.Run(t2)
+//	defer invoke t4.Handle(...t5)
+//
+// For all calls to variadic functions (Signature().Variadic()),
+// the last element of Args is a slice.
+type CallCommon struct {
+	Value  Value       // receiver (invoke mode) or func value (call mode)
+	Method *types.Func // interface method (invoke mode)
+	Args   []Value     // actual parameters (in static method call, includes receiver)
+	pos    token.Pos   // position of CallExpr.Lparen, iff explicit in source
+}
+
+// IsInvoke returns true if this call has "invoke" (not "call") mode.
+func (c *CallCommon) IsInvoke() bool {
+	return c.Method != nil
+}
+
+func (c *CallCommon) Pos() token.Pos { return c.pos }
+
+// Signature returns the signature of the called function.
+//
+// For an "invoke"-mode call, the signature of the interface method is
+// returned.
+//
+// In either "call" or "invoke" mode, if the callee is a method, its
+// receiver is represented by sig.Recv, not sig.Params().At(0).
+func (c *CallCommon) Signature() *types.Signature {
+	if c.Method != nil {
+		return c.Method.Type().(*types.Signature)
+	}
+	return typeparams.CoreType(c.Value.Type()).(*types.Signature)
+}
+
+// StaticCallee returns the callee if this is a trivially static
+// "call"-mode call to a function.
+func (c *CallCommon) StaticCallee() *Function {
+	switch fn := c.Value.(type) {
+	case *Function:
+		return fn
+	case *MakeClosure:
+		return fn.Fn.(*Function)
+	}
+	return nil
+}
+
+// Description returns a description of the mode of this call suitable
+// for a user interface, e.g., "static method call".
+func (c *CallCommon) Description() string {
+	switch fn := c.Value.(type) {
+	case *Builtin:
+		return "built-in function call"
+	case *MakeClosure:
+		return "static function closure call"
+	case *Function:
+		if fn.Signature.Recv() != nil {
+			return "static method call"
+		}
+		return "static function call"
+	}
+	if c.IsInvoke() {
+		return "dynamic method call" // ("invoke" mode)
+	}
+	return "dynamic function call"
+}
+
+// The CallInstruction interface, implemented by *Go, *Defer and *Call,
+// exposes the common parts of function-calling instructions,
+// yet provides a way back to the Value defined by *Call alone.
+type CallInstruction interface {
+	Instruction
+	Common() *CallCommon // returns the common parts of the call
+	Value() *Call        // returns the result value of the call (*Call) or nil (*Go, *Defer)
+}
+
+func (s *Call) Common() *CallCommon  { return &s.Call }
+func (s *Defer) Common() *CallCommon { return &s.Call }
+func (s *Go) Common() *CallCommon    { return &s.Call }
+
+func (s *Call) Value() *Call  { return s }
+func (s *Defer) Value() *Call { return nil }
+func (s *Go) Value() *Call    { return nil }
+
+func (v *Builtin) Type() types.Type        { return v.sig }
+func (v *Builtin) Name() string            { return v.name }
+func (*Builtin) Referrers() *[]Instruction { return nil }
+func (v *Builtin) Pos() token.Pos          { return token.NoPos }
+func (v *Builtin) Object() types.Object    { return types.Universe.Lookup(v.name) }
+func (v *Builtin) Parent() *Function       { return nil }
+
+func (v *FreeVar) Type() types.Type          { return v.typ }
+func (v *FreeVar) Name() string              { return v.name }
+func (v *FreeVar) Referrers() *[]Instruction { return &v.referrers }
+func (v *FreeVar) Pos() token.Pos            { return v.pos }
+func (v *FreeVar) Parent() *Function         { return v.parent }
+
+func (v *Global) Type() types.Type                     { return v.typ }
+func (v *Global) Name() string                         { return v.name }
+func (v *Global) Parent() *Function                    { return nil }
+func (v *Global) Pos() token.Pos                       { return v.pos }
+func (v *Global) Referrers() *[]Instruction            { return nil }
+func (v *Global) Token() token.Token                   { return token.VAR }
+func (v *Global) Object() types.Object                 { return v.object }
+func (v *Global) String() string                       { return v.RelString(nil) }
+func (v *Global) Package() *Package                    { return v.Pkg }
+func (v *Global) RelString(from *types.Package) string { return relString(v, from) }
+
+func (v *Function) Name() string       { return v.name }
+func (v *Function) Type() types.Type   { return v.Signature }
+func (v *Function) Pos() token.Pos     { return v.pos }
+func (v *Function) Token() token.Token { return token.FUNC }
+func (v *Function) Object() types.Object {
+	if v.object != nil {
+		return types.Object(v.object)
+	}
+	return nil
+}
+func (v *Function) String() string    { return v.RelString(nil) }
+func (v *Function) Package() *Package { return v.Pkg }
+func (v *Function) Parent() *Function { return v.parent }
+func (v *Function) Referrers() *[]Instruction {
+	if v.parent != nil {
+		return &v.referrers
+	}
+	return nil
+}
+
+// TypeParams are the function's type parameters if generic or the
+// type parameters that were instantiated if fn is an instantiation.
+func (fn *Function) TypeParams() *types.TypeParamList {
+	return fn.typeparams
+}
+
+// TypeArgs are the types that TypeParams() were instantiated by to create fn
+// from fn.Origin().
+func (fn *Function) TypeArgs() []types.Type { return fn.typeargs }
+
+// Origin returns the generic function from which fn was instantiated,
+// or nil if fn is not an instantiation.
+func (fn *Function) Origin() *Function {
+	if fn.parent != nil && len(fn.typeargs) > 0 {
+		// Nested functions are BUILT at a different time than their instances.
+		// Build declared package if not yet BUILT. This is not an expected use
+		// case, but is simple and robust.
+		fn.declaredPackage().Build()
+	}
+	return origin(fn)
+}
+
+// origin is the function that fn is an instantiation of. Returns nil if fn is
+// not an instantiation.
+//
+// Precondition: fn and the origin function are done building.
+func origin(fn *Function) *Function {
+	if fn.parent != nil && len(fn.typeargs) > 0 {
+		return origin(fn.parent).AnonFuncs[fn.anonIdx]
+	}
+	return fn.topLevelOrigin
+}
+
+func (v *Parameter) Type() types.Type          { return v.typ }
+func (v *Parameter) Name() string              { return v.name }
+func (v *Parameter) Object() types.Object      { return v.object }
+func (v *Parameter) Referrers() *[]Instruction { return &v.referrers }
+func (v *Parameter) Pos() token.Pos            { return v.object.Pos() }
+func (v *Parameter) Parent() *Function         { return v.parent }
+
+func (v *Alloc) Type() types.Type          { return v.typ }
+func (v *Alloc) Referrers() *[]Instruction { return &v.referrers }
+func (v *Alloc) Pos() token.Pos            { return v.pos }
+
+func (v *register) Type() types.Type          { return v.typ }
+func (v *register) setType(typ types.Type)    { v.typ = typ }
+func (v *register) Name() string              { return fmt.Sprintf("t%d", v.num) }
+func (v *register) setNum(num int)            { v.num = num }
+func (v *register) Referrers() *[]Instruction { return &v.referrers }
+func (v *register) Pos() token.Pos            { return v.pos }
+func (v *register) setPos(pos token.Pos)      { v.pos = pos }
+
+func (v *anInstruction) Parent() *Function          { return v.block.parent }
+func (v *anInstruction) Block() *BasicBlock         { return v.block }
+func (v *anInstruction) setBlock(block *BasicBlock) { v.block = block }
+func (v *anInstruction) Referrers() *[]Instruction  { return nil }
+
+func (t *Type) Name() string                         { return t.object.Name() }
+func (t *Type) Pos() token.Pos                       { return t.object.Pos() }
+func (t *Type) Type() types.Type                     { return t.object.Type() }
+func (t *Type) Token() token.Token                   { return token.TYPE }
+func (t *Type) Object() types.Object                 { return t.object }
+func (t *Type) String() string                       { return t.RelString(nil) }
+func (t *Type) Package() *Package                    { return t.pkg }
+func (t *Type) RelString(from *types.Package) string { return relString(t, from) }
+
+func (c *NamedConst) Name() string                         { return c.object.Name() }
+func (c *NamedConst) Pos() token.Pos                       { return c.object.Pos() }
+func (c *NamedConst) String() string                       { return c.RelString(nil) }
+func (c *NamedConst) Type() types.Type                     { return c.object.Type() }
+func (c *NamedConst) Token() token.Token                   { return token.CONST }
+func (c *NamedConst) Object() types.Object                 { return c.object }
+func (c *NamedConst) Package() *Package                    { return c.pkg }
+func (c *NamedConst) RelString(from *types.Package) string { return relString(c, from) }
+
+func (d *DebugRef) Object() types.Object { return d.object }
+
+// Func returns the package-level function of the specified name,
+// or nil if not found.
+func (p *Package) Func(name string) (f *Function) {
+	f, _ = p.Members[name].(*Function)
+	return
+}
+
+// Var returns the package-level variable of the specified name,
+// or nil if not found.
+func (p *Package) Var(name string) (g *Global) {
+	g, _ = p.Members[name].(*Global)
+	return
+}
+
+// Const returns the package-level constant of the specified name,
+// or nil if not found.
+func (p *Package) Const(name string) (c *NamedConst) {
+	c, _ = p.Members[name].(*NamedConst)
+	return
+}
+
+// Type returns the package-level type of the specified name,
+// or nil if not found.
+func (p *Package) Type(name string) (t *Type) {
+	t, _ = p.Members[name].(*Type)
+	return
+}
+
+func (v *Call) Pos() token.Pos      { return v.Call.pos }
+func (s *Defer) Pos() token.Pos     { return s.pos }
+func (s *Go) Pos() token.Pos        { return s.pos }
+func (s *MapUpdate) Pos() token.Pos { return s.pos }
+func (s *Panic) Pos() token.Pos     { return s.pos }
+func (s *Return) Pos() token.Pos    { return s.pos }
+func (s *Send) Pos() token.Pos      { return s.pos }
+func (s *Store) Pos() token.Pos     { return s.pos }
+func (s *If) Pos() token.Pos        { return token.NoPos }
+func (s *Jump) Pos() token.Pos      { return token.NoPos }
+func (s *RunDefers) Pos() token.Pos { return token.NoPos }
+func (s *DebugRef) Pos() token.Pos  { return s.Expr.Pos() }
+
+// Operands.
+
+func (v *Alloc) Operands(rands []*Value) []*Value {
+	return rands
+}
+
+func (v *BinOp) Operands(rands []*Value) []*Value {
+	return append(rands, &v.X, &v.Y)
+}
+
+func (c *CallCommon) Operands(rands []*Value) []*Value {
+	rands = append(rands, &c.Value)
+	for i := range c.Args {
+		rands = append(rands, &c.Args[i])
+	}
+	return rands
+}
+
+func (s *Go) Operands(rands []*Value) []*Value {
+	return s.Call.Operands(rands)
+}
+
+func (s *Call) Operands(rands []*Value) []*Value {
+	return s.Call.Operands(rands)
+}
+
+func (s *Defer) Operands(rands []*Value) []*Value {
+	return append(s.Call.Operands(rands), &s.DeferStack)
+}
+
+func (v *ChangeInterface) Operands(rands []*Value) []*Value {
+	return append(rands, &v.X)
+}
+
+func (v *ChangeType) Operands(rands []*Value) []*Value {
+	return append(rands, &v.X)
+}
+
+func (v *Convert) Operands(rands []*Value) []*Value {
+	return append(rands, &v.X)
+}
+
+func (v *MultiConvert) Operands(rands []*Value) []*Value {
+	return append(rands, &v.X)
+}
+
+func (v *SliceToArrayPointer) Operands(rands []*Value) []*Value {
+	return append(rands, &v.X)
+}
+
+func (s *DebugRef) Operands(rands []*Value) []*Value {
+	return append(rands, &s.X)
+}
+
+func (v *Extract) Operands(rands []*Value) []*Value {
+	return append(rands, &v.Tuple)
+}
+
+func (v *Field) Operands(rands []*Value) []*Value {
+	return append(rands, &v.X)
+}
+
+func (v *FieldAddr) Operands(rands []*Value) []*Value {
+	return append(rands, &v.X)
+}
+
+func (s *If) Operands(rands []*Value) []*Value {
+	return append(rands, &s.Cond)
+}
+
+func (v *Index) Operands(rands []*Value) []*Value {
+	return append(rands, &v.X, &v.Index)
+}
+
+func (v *IndexAddr) Operands(rands []*Value) []*Value {
+	return append(rands, &v.X, &v.Index)
+}
+
+func (*Jump) Operands(rands []*Value) []*Value {
+	return rands
+}
+
+func (v *Lookup) Operands(rands []*Value) []*Value {
+	return append(rands, &v.X, &v.Index)
+}
+
+func (v *MakeChan) Operands(rands []*Value) []*Value {
+	return append(rands, &v.Size)
+}
+
+func (v *MakeClosure) Operands(rands []*Value) []*Value {
+	rands = append(rands, &v.Fn)
+	for i := range v.Bindings {
+		rands = append(rands, &v.Bindings[i])
+	}
+	return rands
+}
+
+func (v *MakeInterface) Operands(rands []*Value) []*Value {
+	return append(rands, &v.X)
+}
+
+func (v *MakeMap) Operands(rands []*Value) []*Value {
+	return append(rands, &v.Reserve)
+}
+
+func (v *MakeSlice) Operands(rands []*Value) []*Value {
+	return append(rands, &v.Len, &v.Cap)
+}
+
+func (v *MapUpdate) Operands(rands []*Value) []*Value {
+	return append(rands, &v.Map, &v.Key, &v.Value)
+}
+
+func (v *Next) Operands(rands []*Value) []*Value {
+	return append(rands, &v.Iter)
+}
+
+func (s *Panic) Operands(rands []*Value) []*Value {
+	return append(rands, &s.X)
+}
+
+func (v *Phi) Operands(rands []*Value) []*Value {
+	for i := range v.Edges {
+		rands = append(rands, &v.Edges[i])
+	}
+	return rands
+}
+
+func (v *Range) Operands(rands []*Value) []*Value {
+	return append(rands, &v.X)
+}
+
+func (s *Return) Operands(rands []*Value) []*Value {
+	for i := range s.Results {
+		rands = append(rands, &s.Results[i])
+	}
+	return rands
+}
+
+func (*RunDefers) Operands(rands []*Value) []*Value {
+	return rands
+}
+
+func (v *Select) Operands(rands []*Value) []*Value {
+	for i := range v.States {
+		rands = append(rands, &v.States[i].Chan, &v.States[i].Send)
+	}
+	return rands
+}
+
+func (s *Send) Operands(rands []*Value) []*Value {
+	return append(rands, &s.Chan, &s.X)
+}
+
+func (v *Slice) Operands(rands []*Value) []*Value {
+	return append(rands, &v.X, &v.Low, &v.High, &v.Max)
+}
+
+func (s *Store) Operands(rands []*Value) []*Value {
+	return append(rands, &s.Addr, &s.Val)
+}
+
+func (v *TypeAssert) Operands(rands []*Value) []*Value {
+	return append(rands, &v.X)
+}
+
+func (v *UnOp) Operands(rands []*Value) []*Value {
+	return append(rands, &v.X)
+}
+
+// Non-Instruction Values:
+func (v *Builtin) Operands(rands []*Value) []*Value   { return rands }
+func (v *FreeVar) Operands(rands []*Value) []*Value   { return rands }
+func (v *Const) Operands(rands []*Value) []*Value     { return rands }
+func (v *Function) Operands(rands []*Value) []*Value  { return rands }
+func (v *Global) Operands(rands []*Value) []*Value    { return rands }
+func (v *Parameter) Operands(rands []*Value) []*Value { return rands }
diff --git a/vendor/golang.org/x/tools/go/ssa/ssautil/load.go b/vendor/golang.org/x/tools/go/ssa/ssautil/load.go
new file mode 100644
index 0000000..3daa67a
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ssa/ssautil/load.go
@@ -0,0 +1,214 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssautil
+
+// This file defines utility functions for constructing programs in SSA form.
+
+import (
+	"go/ast"
+	"go/token"
+	"go/types"
+
+	"golang.org/x/tools/go/loader"
+	"golang.org/x/tools/go/packages"
+	"golang.org/x/tools/go/ssa"
+	"golang.org/x/tools/internal/versions"
+)
+
+// Packages creates an SSA program for a set of packages.
+//
+// The packages must have been loaded from source syntax using the
+// [packages.Load] function in [packages.LoadSyntax] or
+// [packages.LoadAllSyntax] mode.
+//
+// Packages creates an SSA package for each well-typed package in the
+// initial list, plus all their dependencies. The resulting list of
+// packages corresponds to the list of initial packages, and may contain
+// a nil if SSA code could not be constructed for the corresponding initial
+// package due to type errors.
+//
+// Code for bodies of functions is not built until [Program.Build] is
+// called on the resulting Program. SSA code is constructed only for
+// the initial packages with well-typed syntax trees.
+//
+// The mode parameter controls diagnostics and checking during SSA construction.
+func Packages(initial []*packages.Package, mode ssa.BuilderMode) (*ssa.Program, []*ssa.Package) {
+	// TODO(adonovan): opt: this calls CreatePackage far more than
+	// necessary: for all dependencies, not just the (non-initial)
+	// direct dependencies of the initial packages.
+	//
+	// But can it reasonably be changed without breaking the
+	// spirit and/or letter of the law above? Clients may notice
+	// if we call CreatePackage less, as methods like
+	// Program.FuncValue will return nil. Or must we provide a new
+	// function (and perhaps deprecate this one)? Is it worth it?
+	//
+	// Tim King makes the interesting point that it would be
+	// possible to entirely alleviate the client from the burden
+	// of calling CreatePackage for non-syntax packages, if we
+	// were to treat vars and funcs lazily in the same way we now
+	// treat methods. (In essence, try to move away from the
+	// notion of ssa.Packages, and make the Program answer
+	// all reasonable questions about any types.Object.)
+
+	return doPackages(initial, mode, false)
+}
+
+// AllPackages creates an SSA program for a set of packages plus all
+// their dependencies.
+//
+// The packages must have been loaded from source syntax using the
+// [packages.Load] function in [packages.LoadAllSyntax] mode.
+//
+// AllPackages creates an SSA package for each well-typed package in the
+// initial list, plus all their dependencies. The resulting list of
+// packages corresponds to the list of initial packages, and may contain
+// a nil if SSA code could not be constructed for the corresponding
+// initial package due to type errors.
+//
+// Code for bodies of functions is not built until Build is called on
+// the resulting Program. SSA code is constructed for all packages with
+// well-typed syntax trees.
+//
+// The mode parameter controls diagnostics and checking during SSA construction.
+func AllPackages(initial []*packages.Package, mode ssa.BuilderMode) (*ssa.Program, []*ssa.Package) {
+	return doPackages(initial, mode, true)
+}
+
+func doPackages(initial []*packages.Package, mode ssa.BuilderMode, deps bool) (*ssa.Program, []*ssa.Package) {
+
+	var fset *token.FileSet
+	if len(initial) > 0 {
+		fset = initial[0].Fset
+	}
+
+	prog := ssa.NewProgram(fset, mode)
+
+	isInitial := make(map[*packages.Package]bool, len(initial))
+	for _, p := range initial {
+		isInitial[p] = true
+	}
+
+	ssamap := make(map[*packages.Package]*ssa.Package)
+	packages.Visit(initial, nil, func(p *packages.Package) {
+		if p.Types != nil && !p.IllTyped {
+			var files []*ast.File
+			var info *types.Info
+			if deps || isInitial[p] {
+				files = p.Syntax
+				info = p.TypesInfo
+			}
+			ssamap[p] = prog.CreatePackage(p.Types, files, info, true)
+		}
+	})
+
+	var ssapkgs []*ssa.Package
+	for _, p := range initial {
+		ssapkgs = append(ssapkgs, ssamap[p]) // may be nil
+	}
+	return prog, ssapkgs
+}
+
+// CreateProgram returns a new program in SSA form, given a program
+// loaded from source.  An SSA package is created for each transitively
+// error-free package of lprog.
+//
+// Code for bodies of functions is not built until Build is called
+// on the result.
+//
+// The mode parameter controls diagnostics and checking during SSA construction.
+//
+// Deprecated: Use [golang.org/x/tools/go/packages] and the [Packages]
+// function instead; see ssa.Example_loadPackages.
+func CreateProgram(lprog *loader.Program, mode ssa.BuilderMode) *ssa.Program {
+	prog := ssa.NewProgram(lprog.Fset, mode)
+
+	for _, info := range lprog.AllPackages {
+		if info.TransitivelyErrorFree {
+			prog.CreatePackage(info.Pkg, info.Files, &info.Info, info.Importable)
+		}
+	}
+
+	return prog
+}
+
+// BuildPackage builds an SSA program with SSA intermediate
+// representation (IR) for all functions of a single package.
+//
+// It populates pkg by type-checking the specified file syntax trees.  All
+// dependencies are loaded using the importer specified by tc, which
+// typically loads compiler export data; SSA code cannot be built for
+// those packages.  BuildPackage then constructs an [ssa.Program] with all
+// dependency packages created, and builds and returns the SSA package
+// corresponding to pkg.
+//
+// The caller must have set pkg.Path to the import path.
+//
+// The operation fails if there were any type-checking or import errors.
+//
+// See ../example_test.go for an example.
+func BuildPackage(tc *types.Config, fset *token.FileSet, pkg *types.Package, files []*ast.File, mode ssa.BuilderMode) (*ssa.Package, *types.Info, error) {
+	if fset == nil {
+		panic("no token.FileSet")
+	}
+	if pkg.Path() == "" {
+		panic("package has no import path")
+	}
+
+	info := &types.Info{
+		Types:      make(map[ast.Expr]types.TypeAndValue),
+		Defs:       make(map[*ast.Ident]types.Object),
+		Uses:       make(map[*ast.Ident]types.Object),
+		Implicits:  make(map[ast.Node]types.Object),
+		Instances:  make(map[*ast.Ident]types.Instance),
+		Scopes:     make(map[ast.Node]*types.Scope),
+		Selections: make(map[*ast.SelectorExpr]*types.Selection),
+	}
+	versions.InitFileVersions(info)
+	if err := types.NewChecker(tc, fset, pkg, info).Files(files); err != nil {
+		return nil, nil, err
+	}
+
+	prog := ssa.NewProgram(fset, mode)
+
+	// Create SSA packages for all imports.
+	// Order is not significant.
+	created := make(map[*types.Package]bool)
+	var createAll func(pkgs []*types.Package)
+	createAll = func(pkgs []*types.Package) {
+		for _, p := range pkgs {
+			if !created[p] {
+				created[p] = true
+				prog.CreatePackage(p, nil, nil, true)
+				createAll(p.Imports())
+			}
+		}
+	}
+	createAll(pkg.Imports())
+
+	// TODO(adonovan): we could replace createAll with just:
+	//
+	// // Create SSA packages for all imports.
+	// for _, p := range pkg.Imports() {
+	// 	prog.CreatePackage(p, nil, nil, true)
+	// }
+	//
+	// (with minor changes to changes to ../builder_test.go as
+	// shown in CL 511715 PS 10.) But this would strictly violate
+	// the letter of the doc comment above, which says "all
+	// dependencies created".
+	//
+	// Tim makes the good point with some extra work we could
+	// remove the need for any CreatePackage calls except the
+	// ones with syntax (i.e. primary packages). Of course
+	// You wouldn't have ssa.Packages and Members for as
+	// many things but no-one really uses that anyway.
+	// I wish I had done this from the outset.
+
+	// Create and build the primary package.
+	ssapkg := prog.CreatePackage(pkg, files, info, false)
+	ssapkg.Build()
+	return ssapkg, info, nil
+}
diff --git a/vendor/golang.org/x/tools/go/ssa/ssautil/switch.go b/vendor/golang.org/x/tools/go/ssa/ssautil/switch.go
new file mode 100644
index 0000000..dd4b04e
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ssa/ssautil/switch.go
@@ -0,0 +1,230 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssautil
+
+// This file implements discovery of switch and type-switch constructs
+// from low-level control flow.
+//
+// Many techniques exist for compiling a high-level switch with
+// constant cases to efficient machine code.  The optimal choice will
+// depend on the data type, the specific case values, the code in the
+// body of each case, and the hardware.
+// Some examples:
+// - a lookup table (for a switch that maps constants to constants)
+// - a computed goto
+// - a binary tree
+// - a perfect hash
+// - a two-level switch (to partition constant strings by their first byte).
+
+import (
+	"bytes"
+	"fmt"
+	"go/token"
+	"go/types"
+
+	"golang.org/x/tools/go/ssa"
+)
+
+// A ConstCase represents a single constant comparison.
+// It is part of a Switch.
+type ConstCase struct {
+	Block *ssa.BasicBlock // block performing the comparison
+	Body  *ssa.BasicBlock // body of the case
+	Value *ssa.Const      // case comparand
+}
+
+// A TypeCase represents a single type assertion.
+// It is part of a Switch.
+type TypeCase struct {
+	Block   *ssa.BasicBlock // block performing the type assert
+	Body    *ssa.BasicBlock // body of the case
+	Type    types.Type      // case type
+	Binding ssa.Value       // value bound by this case
+}
+
+// A Switch is a logical high-level control flow operation
+// (a multiway branch) discovered by analysis of a CFG containing
+// only if/else chains.  It is not part of the ssa.Instruction set.
+//
+// One of ConstCases and TypeCases has length >= 2;
+// the other is nil.
+//
+// In a value switch, the list of cases may contain duplicate constants.
+// A type switch may contain duplicate types, or types assignable
+// to an interface type also in the list.
+// TODO(adonovan): eliminate such duplicates.
+type Switch struct {
+	Start      *ssa.BasicBlock // block containing start of if/else chain
+	X          ssa.Value       // the switch operand
+	ConstCases []ConstCase     // ordered list of constant comparisons
+	TypeCases  []TypeCase      // ordered list of type assertions
+	Default    *ssa.BasicBlock // successor if all comparisons fail
+}
+
+func (sw *Switch) String() string {
+	// We represent each block by the String() of its
+	// first Instruction, e.g. "print(42:int)".
+	var buf bytes.Buffer
+	if sw.ConstCases != nil {
+		fmt.Fprintf(&buf, "switch %s {\n", sw.X.Name())
+		for _, c := range sw.ConstCases {
+			fmt.Fprintf(&buf, "case %s: %s\n", c.Value, c.Body.Instrs[0])
+		}
+	} else {
+		fmt.Fprintf(&buf, "switch %s.(type) {\n", sw.X.Name())
+		for _, c := range sw.TypeCases {
+			fmt.Fprintf(&buf, "case %s %s: %s\n",
+				c.Binding.Name(), c.Type, c.Body.Instrs[0])
+		}
+	}
+	if sw.Default != nil {
+		fmt.Fprintf(&buf, "default: %s\n", sw.Default.Instrs[0])
+	}
+	fmt.Fprintf(&buf, "}")
+	return buf.String()
+}
+
+// Switches examines the control-flow graph of fn and returns the
+// set of inferred value and type switches.  A value switch tests an
+// ssa.Value for equality against two or more compile-time constant
+// values.  Switches involving link-time constants (addresses) are
+// ignored.  A type switch type-asserts an ssa.Value against two or
+// more types.
+//
+// The switches are returned in dominance order.
+//
+// The resulting switches do not necessarily correspond to uses of the
+// 'switch' keyword in the source: for example, a single source-level
+// switch statement with non-constant cases may result in zero, one or
+// many Switches, one per plural sequence of constant cases.
+// Switches may even be inferred from if/else- or goto-based control flow.
+// (In general, the control flow constructs of the source program
+// cannot be faithfully reproduced from the SSA representation.)
+func Switches(fn *ssa.Function) []Switch {
+	// Traverse the CFG in dominance order, so we don't
+	// enter an if/else-chain in the middle.
+	var switches []Switch
+	seen := make(map[*ssa.BasicBlock]bool) // TODO(adonovan): opt: use ssa.blockSet
+	for _, b := range fn.DomPreorder() {
+		if x, k := isComparisonBlock(b); x != nil {
+			// Block b starts a switch.
+			sw := Switch{Start: b, X: x}
+			valueSwitch(&sw, k, seen)
+			if len(sw.ConstCases) > 1 {
+				switches = append(switches, sw)
+			}
+		}
+
+		if y, x, T := isTypeAssertBlock(b); y != nil {
+			// Block b starts a type switch.
+			sw := Switch{Start: b, X: x}
+			typeSwitch(&sw, y, T, seen)
+			if len(sw.TypeCases) > 1 {
+				switches = append(switches, sw)
+			}
+		}
+	}
+	return switches
+}
+
+func valueSwitch(sw *Switch, k *ssa.Const, seen map[*ssa.BasicBlock]bool) {
+	b := sw.Start
+	x := sw.X
+	for x == sw.X {
+		if seen[b] {
+			break
+		}
+		seen[b] = true
+
+		sw.ConstCases = append(sw.ConstCases, ConstCase{
+			Block: b,
+			Body:  b.Succs[0],
+			Value: k,
+		})
+		b = b.Succs[1]
+		if len(b.Instrs) > 2 {
+			// Block b contains not just 'if x == k',
+			// so it may have side effects that
+			// make it unsafe to elide.
+			break
+		}
+		if len(b.Preds) != 1 {
+			// Block b has multiple predecessors,
+			// so it cannot be treated as a case.
+			break
+		}
+		x, k = isComparisonBlock(b)
+	}
+	sw.Default = b
+}
+
+func typeSwitch(sw *Switch, y ssa.Value, T types.Type, seen map[*ssa.BasicBlock]bool) {
+	b := sw.Start
+	x := sw.X
+	for x == sw.X {
+		if seen[b] {
+			break
+		}
+		seen[b] = true
+
+		sw.TypeCases = append(sw.TypeCases, TypeCase{
+			Block:   b,
+			Body:    b.Succs[0],
+			Type:    T,
+			Binding: y,
+		})
+		b = b.Succs[1]
+		if len(b.Instrs) > 4 {
+			// Block b contains not just
+			//  {TypeAssert; Extract #0; Extract #1; If}
+			// so it may have side effects that
+			// make it unsafe to elide.
+			break
+		}
+		if len(b.Preds) != 1 {
+			// Block b has multiple predecessors,
+			// so it cannot be treated as a case.
+			break
+		}
+		y, x, T = isTypeAssertBlock(b)
+	}
+	sw.Default = b
+}
+
+// isComparisonBlock returns the operands (v, k) if a block ends with
+// a comparison v==k, where k is a compile-time constant.
+func isComparisonBlock(b *ssa.BasicBlock) (v ssa.Value, k *ssa.Const) {
+	if n := len(b.Instrs); n >= 2 {
+		if i, ok := b.Instrs[n-1].(*ssa.If); ok {
+			if binop, ok := i.Cond.(*ssa.BinOp); ok && binop.Block() == b && binop.Op == token.EQL {
+				if k, ok := binop.Y.(*ssa.Const); ok {
+					return binop.X, k
+				}
+				if k, ok := binop.X.(*ssa.Const); ok {
+					return binop.Y, k
+				}
+			}
+		}
+	}
+	return
+}
+
+// isTypeAssertBlock returns the operands (y, x, T) if a block ends with
+// a type assertion "if y, ok := x.(T); ok {".
+func isTypeAssertBlock(b *ssa.BasicBlock) (y, x ssa.Value, T types.Type) {
+	if n := len(b.Instrs); n >= 4 {
+		if i, ok := b.Instrs[n-1].(*ssa.If); ok {
+			if ext1, ok := i.Cond.(*ssa.Extract); ok && ext1.Block() == b && ext1.Index == 1 {
+				if ta, ok := ext1.Tuple.(*ssa.TypeAssert); ok && ta.Block() == b {
+					// hack: relies upon instruction ordering.
+					if ext0, ok := b.Instrs[n-3].(*ssa.Extract); ok {
+						return ext0, ta.X, ta.AssertedType
+					}
+				}
+			}
+		}
+	}
+	return
+}
diff --git a/vendor/golang.org/x/tools/go/ssa/ssautil/visit.go b/vendor/golang.org/x/tools/go/ssa/ssautil/visit.go
new file mode 100644
index 0000000..b4feb42
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ssa/ssautil/visit.go
@@ -0,0 +1,157 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssautil // import "golang.org/x/tools/go/ssa/ssautil"
+
+import (
+	"go/ast"
+	"go/types"
+
+	"golang.org/x/tools/go/ssa"
+
+	_ "unsafe" // for linkname hack
+)
+
+// This file defines utilities for visiting the SSA representation of
+// a Program.
+//
+// TODO(adonovan): test coverage.
+
+// AllFunctions finds and returns the set of functions potentially
+// needed by program prog, as determined by a simple linker-style
+// reachability algorithm starting from the members and method-sets of
+// each package.  The result may include anonymous functions and
+// synthetic wrappers.
+//
+// Precondition: all packages are built.
+//
+// TODO(adonovan): this function is underspecified. It doesn't
+// actually work like a linker, which computes reachability from main
+// using something like go/callgraph/cha (without materializing the
+// call graph). In fact, it treats all public functions and all
+// methods of public non-parameterized types as roots, even though
+// they may be unreachable--but only in packages created from syntax.
+//
+// I think we should deprecate AllFunctions function in favor of two
+// clearly defined ones:
+//
+//  1. The first would efficiently compute CHA reachability from a set
+//     of main packages, making it suitable for a whole-program
+//     analysis context with InstantiateGenerics, in conjunction with
+//     Program.Build.
+//
+//  2. The second would return only the set of functions corresponding
+//     to source Func{Decl,Lit} syntax, like SrcFunctions in
+//     go/analysis/passes/buildssa; this is suitable for
+//     package-at-a-time (or handful of packages) context.
+//     ssa.Package could easily expose it as a field.
+//
+// We could add them unexported for now and use them via the linkname hack.
+func AllFunctions(prog *ssa.Program) map[*ssa.Function]bool {
+	seen := make(map[*ssa.Function]bool)
+
+	var function func(fn *ssa.Function)
+	function = func(fn *ssa.Function) {
+		if !seen[fn] {
+			seen[fn] = true
+			var buf [10]*ssa.Value // avoid alloc in common case
+			for _, b := range fn.Blocks {
+				for _, instr := range b.Instrs {
+					for _, op := range instr.Operands(buf[:0]) {
+						if fn, ok := (*op).(*ssa.Function); ok {
+							function(fn)
+						}
+					}
+				}
+			}
+		}
+	}
+
+	// TODO(adonovan): opt: provide a way to share a builder
+	// across a sequence of MethodValue calls.
+
+	methodsOf := func(T types.Type) {
+		if !types.IsInterface(T) {
+			mset := prog.MethodSets.MethodSet(T)
+			for i := 0; i < mset.Len(); i++ {
+				function(prog.MethodValue(mset.At(i)))
+			}
+		}
+	}
+
+	// Historically, Program.RuntimeTypes used to include the type
+	// of any exported member of a package loaded from syntax that
+	// has a non-parameterized type, plus all types
+	// reachable from that type using reflection, even though
+	// these runtime types may not be required for them.
+	//
+	// Rather than break existing programs that rely on
+	// AllFunctions visiting extra methods that are unreferenced
+	// by IR and unreachable via reflection, we moved the logic
+	// here, unprincipled though it is.
+	// (See doc comment for better ideas.)
+	//
+	// Nonetheless, after the move, we no longer visit every
+	// method of any type recursively reachable from T, only the
+	// methods of T and *T themselves, and we only apply this to
+	// named types T, and not to the type of every exported
+	// package member.
+	exportedTypeHack := func(t *ssa.Type) {
+		if isSyntactic(t.Package()) &&
+			ast.IsExported(t.Name()) &&
+			!types.IsInterface(t.Type()) {
+			// Consider only named types.
+			// (Ignore aliases and unsafe.Pointer.)
+			if named, ok := t.Type().(*types.Named); ok {
+				if named.TypeParams() == nil {
+					methodsOf(named)                   //  T
+					methodsOf(types.NewPointer(named)) // *T
+				}
+			}
+		}
+	}
+
+	for _, pkg := range prog.AllPackages() {
+		for _, mem := range pkg.Members {
+			switch mem := mem.(type) {
+			case *ssa.Function:
+				// Visit all package-level declared functions.
+				function(mem)
+
+			case *ssa.Type:
+				exportedTypeHack(mem)
+			}
+		}
+	}
+
+	// Visit all methods of types for which runtime types were
+	// materialized, as they are reachable through reflection.
+	for _, T := range prog.RuntimeTypes() {
+		methodsOf(T)
+	}
+
+	return seen
+}
+
+// MainPackages returns the subset of the specified packages
+// named "main" that define a main function.
+// The result may include synthetic "testmain" packages.
+func MainPackages(pkgs []*ssa.Package) []*ssa.Package {
+	var mains []*ssa.Package
+	for _, pkg := range pkgs {
+		if pkg.Pkg.Name() == "main" && pkg.Func("main") != nil {
+			mains = append(mains, pkg)
+		}
+	}
+	return mains
+}
+
+// TODO(adonovan): propose a principled API for this. One possibility
+// is a new field, Package.SrcFunctions []*Function, which would
+// contain the list of SrcFunctions described in point 2 of the
+// AllFunctions doc comment, or nil if the package is not from syntax.
+// But perhaps overloading nil vs empty slice is too subtle.
+//
+//go:linkname isSyntactic golang.org/x/tools/go/ssa.isSyntactic
+func isSyntactic(pkg *ssa.Package) bool
diff --git a/vendor/golang.org/x/tools/go/ssa/subst.go b/vendor/golang.org/x/tools/go/ssa/subst.go
new file mode 100644
index 0000000..4dcb871
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ssa/subst.go
@@ -0,0 +1,642 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+import (
+	"go/types"
+
+	"golang.org/x/tools/go/types/typeutil"
+	"golang.org/x/tools/internal/aliases"
+)
+
+// subster defines a type substitution operation of a set of type parameters
+// to type parameter free replacement types. Substitution is done within
+// the context of a package-level function instantiation. *Named types
+// declared in the function are unique to the instantiation.
+//
+// For example, given a parameterized function F
+//
+//	  func F[S, T any]() any {
+//	    type X struct{ s S; next *X }
+//		var p *X
+//	    return p
+//	  }
+//
+// calling the instantiation F[string, int]() returns an interface
+// value (*X[string,int], nil) where the underlying value of
+// X[string,int] is a struct{s string; next *X[string,int]}.
+//
+// A nil *subster is a valid, empty substitution map. It always acts as
+// the identity function. This allows for treating parameterized and
+// non-parameterized functions identically while compiling to ssa.
+//
+// Not concurrency-safe.
+//
+// Note: Some may find it helpful to think through some of the most
+// complex substitution cases using lambda calculus inspired notation.
+// subst.typ() solves evaluating a type expression E
+// within the body of a function Fn[m] with the type parameters m
+// once we have applied the type arguments N.
+// We can succinctly write this as a function application:
+//
+//	((λm. E) N)
+//
+// go/types does not provide this interface directly.
+// So what subster provides is a type substitution operation
+//
+//	E[m:=N]
+type subster struct {
+	replacements map[*types.TypeParam]types.Type // values should contain no type params
+	cache        map[types.Type]types.Type       // cache of subst results
+	origin       *types.Func                     // types.Objects declared within this origin function are unique within this context
+	ctxt         *types.Context                  // speeds up repeated instantiations
+	uniqueness   typeutil.Map                    // determines the uniqueness of the instantiations within the function
+	// TODO(taking): consider adding Pos
+}
+
+// Returns a subster that replaces tparams[i] with targs[i]. Uses ctxt as a cache.
+// targs should not contain any types in tparams.
+// fn is the generic function for which we are substituting.
+func makeSubster(ctxt *types.Context, fn *types.Func, tparams *types.TypeParamList, targs []types.Type, debug bool) *subster {
+	assert(tparams.Len() == len(targs), "makeSubster argument count must match")
+
+	subst := &subster{
+		replacements: make(map[*types.TypeParam]types.Type, tparams.Len()),
+		cache:        make(map[types.Type]types.Type),
+		origin:       fn.Origin(),
+		ctxt:         ctxt,
+	}
+	for i := 0; i < tparams.Len(); i++ {
+		subst.replacements[tparams.At(i)] = targs[i]
+	}
+	return subst
+}
+
+// typ returns the type of t with the type parameter tparams[i] substituted
+// for the type targs[i] where subst was created using tparams and targs.
+func (subst *subster) typ(t types.Type) (res types.Type) {
+	if subst == nil {
+		return t // A nil subst is type preserving.
+	}
+	if r, ok := subst.cache[t]; ok {
+		return r
+	}
+	defer func() {
+		subst.cache[t] = res
+	}()
+
+	switch t := t.(type) {
+	case *types.TypeParam:
+		if r := subst.replacements[t]; r != nil {
+			return r
+		}
+		return t
+
+	case *types.Basic:
+		return t
+
+	case *types.Array:
+		if r := subst.typ(t.Elem()); r != t.Elem() {
+			return types.NewArray(r, t.Len())
+		}
+		return t
+
+	case *types.Slice:
+		if r := subst.typ(t.Elem()); r != t.Elem() {
+			return types.NewSlice(r)
+		}
+		return t
+
+	case *types.Pointer:
+		if r := subst.typ(t.Elem()); r != t.Elem() {
+			return types.NewPointer(r)
+		}
+		return t
+
+	case *types.Tuple:
+		return subst.tuple(t)
+
+	case *types.Struct:
+		return subst.struct_(t)
+
+	case *types.Map:
+		key := subst.typ(t.Key())
+		elem := subst.typ(t.Elem())
+		if key != t.Key() || elem != t.Elem() {
+			return types.NewMap(key, elem)
+		}
+		return t
+
+	case *types.Chan:
+		if elem := subst.typ(t.Elem()); elem != t.Elem() {
+			return types.NewChan(t.Dir(), elem)
+		}
+		return t
+
+	case *types.Signature:
+		return subst.signature(t)
+
+	case *types.Union:
+		return subst.union(t)
+
+	case *types.Interface:
+		return subst.interface_(t)
+
+	case *aliases.Alias:
+		return subst.alias(t)
+
+	case *types.Named:
+		return subst.named(t)
+
+	case *opaqueType:
+		return t // opaque types are never substituted
+
+	default:
+		panic("unreachable")
+	}
+}
+
+// types returns the result of {subst.typ(ts[i])}.
+func (subst *subster) types(ts []types.Type) []types.Type {
+	res := make([]types.Type, len(ts))
+	for i := range ts {
+		res[i] = subst.typ(ts[i])
+	}
+	return res
+}
+
+func (subst *subster) tuple(t *types.Tuple) *types.Tuple {
+	if t != nil {
+		if vars := subst.varlist(t); vars != nil {
+			return types.NewTuple(vars...)
+		}
+	}
+	return t
+}
+
+type varlist interface {
+	At(i int) *types.Var
+	Len() int
+}
+
+// fieldlist is an adapter for structs for the varlist interface.
+type fieldlist struct {
+	str *types.Struct
+}
+
+func (fl fieldlist) At(i int) *types.Var { return fl.str.Field(i) }
+func (fl fieldlist) Len() int            { return fl.str.NumFields() }
+
+func (subst *subster) struct_(t *types.Struct) *types.Struct {
+	if t != nil {
+		if fields := subst.varlist(fieldlist{t}); fields != nil {
+			tags := make([]string, t.NumFields())
+			for i, n := 0, t.NumFields(); i < n; i++ {
+				tags[i] = t.Tag(i)
+			}
+			return types.NewStruct(fields, tags)
+		}
+	}
+	return t
+}
+
+// varlist returns subst(in[i]) or return nils if subst(v[i]) == v[i] for all i.
+func (subst *subster) varlist(in varlist) []*types.Var {
+	var out []*types.Var // nil => no updates
+	for i, n := 0, in.Len(); i < n; i++ {
+		v := in.At(i)
+		w := subst.var_(v)
+		if v != w && out == nil {
+			out = make([]*types.Var, n)
+			for j := 0; j < i; j++ {
+				out[j] = in.At(j)
+			}
+		}
+		if out != nil {
+			out[i] = w
+		}
+	}
+	return out
+}
+
+func (subst *subster) var_(v *types.Var) *types.Var {
+	if v != nil {
+		if typ := subst.typ(v.Type()); typ != v.Type() {
+			if v.IsField() {
+				return types.NewField(v.Pos(), v.Pkg(), v.Name(), typ, v.Embedded())
+			}
+			return types.NewVar(v.Pos(), v.Pkg(), v.Name(), typ)
+		}
+	}
+	return v
+}
+
+func (subst *subster) union(u *types.Union) *types.Union {
+	var out []*types.Term // nil => no updates
+
+	for i, n := 0, u.Len(); i < n; i++ {
+		t := u.Term(i)
+		r := subst.typ(t.Type())
+		if r != t.Type() && out == nil {
+			out = make([]*types.Term, n)
+			for j := 0; j < i; j++ {
+				out[j] = u.Term(j)
+			}
+		}
+		if out != nil {
+			out[i] = types.NewTerm(t.Tilde(), r)
+		}
+	}
+
+	if out != nil {
+		return types.NewUnion(out)
+	}
+	return u
+}
+
+func (subst *subster) interface_(iface *types.Interface) *types.Interface {
+	if iface == nil {
+		return nil
+	}
+
+	// methods for the interface. Initially nil if there is no known change needed.
+	// Signatures for the method where recv is nil. NewInterfaceType fills in the receivers.
+	var methods []*types.Func
+	initMethods := func(n int) { // copy first n explicit methods
+		methods = make([]*types.Func, iface.NumExplicitMethods())
+		for i := 0; i < n; i++ {
+			f := iface.ExplicitMethod(i)
+			norecv := changeRecv(f.Type().(*types.Signature), nil)
+			methods[i] = types.NewFunc(f.Pos(), f.Pkg(), f.Name(), norecv)
+		}
+	}
+	for i := 0; i < iface.NumExplicitMethods(); i++ {
+		f := iface.ExplicitMethod(i)
+		// On interfaces, we need to cycle break on anonymous interface types
+		// being in a cycle with their signatures being in cycles with their receivers
+		// that do not go through a Named.
+		norecv := changeRecv(f.Type().(*types.Signature), nil)
+		sig := subst.typ(norecv)
+		if sig != norecv && methods == nil {
+			initMethods(i)
+		}
+		if methods != nil {
+			methods[i] = types.NewFunc(f.Pos(), f.Pkg(), f.Name(), sig.(*types.Signature))
+		}
+	}
+
+	var embeds []types.Type
+	initEmbeds := func(n int) { // copy first n embedded types
+		embeds = make([]types.Type, iface.NumEmbeddeds())
+		for i := 0; i < n; i++ {
+			embeds[i] = iface.EmbeddedType(i)
+		}
+	}
+	for i := 0; i < iface.NumEmbeddeds(); i++ {
+		e := iface.EmbeddedType(i)
+		r := subst.typ(e)
+		if e != r && embeds == nil {
+			initEmbeds(i)
+		}
+		if embeds != nil {
+			embeds[i] = r
+		}
+	}
+
+	if methods == nil && embeds == nil {
+		return iface
+	}
+	if methods == nil {
+		initMethods(iface.NumExplicitMethods())
+	}
+	if embeds == nil {
+		initEmbeds(iface.NumEmbeddeds())
+	}
+	return types.NewInterfaceType(methods, embeds).Complete()
+}
+
+func (subst *subster) alias(t *aliases.Alias) types.Type {
+	// See subster.named. This follows the same strategy.
+	tparams := aliases.TypeParams(t)
+	targs := aliases.TypeArgs(t)
+	tname := t.Obj()
+	torigin := aliases.Origin(t)
+
+	if !declaredWithin(tname, subst.origin) {
+		// t is declared outside of the function origin. So t is a package level type alias.
+		if targs.Len() == 0 {
+			// No type arguments so no instantiation needed.
+			return t
+		}
+
+		// Instantiate with the substituted type arguments.
+		newTArgs := subst.typelist(targs)
+		return subst.instantiate(torigin, newTArgs)
+	}
+
+	if targs.Len() == 0 {
+		// t is declared within the function origin and has no type arguments.
+		//
+		// Example: This corresponds to A or B in F, but not A[int]:
+		//
+		//     func F[T any]() {
+		//       type A[S any] = struct{t T, s S}
+		//       type B = T
+		//       var x A[int]
+		//       ...
+		//     }
+		//
+		// This is somewhat different than *Named as *Alias cannot be created recursively.
+
+		// Copy and substitute type params.
+		var newTParams []*types.TypeParam
+		for i := 0; i < tparams.Len(); i++ {
+			cur := tparams.At(i)
+			cobj := cur.Obj()
+			cname := types.NewTypeName(cobj.Pos(), cobj.Pkg(), cobj.Name(), nil)
+			ntp := types.NewTypeParam(cname, nil)
+			subst.cache[cur] = ntp // See the comment "Note: Subtle" in subster.named.
+			newTParams = append(newTParams, ntp)
+		}
+
+		// Substitute rhs.
+		rhs := subst.typ(aliases.Rhs(t))
+
+		// Create the fresh alias.
+		obj := aliases.NewAlias(true, tname.Pos(), tname.Pkg(), tname.Name(), rhs)
+		fresh := obj.Type()
+		if fresh, ok := fresh.(*aliases.Alias); ok {
+			// TODO: assume ok when aliases are always materialized (go1.27).
+			aliases.SetTypeParams(fresh, newTParams)
+		}
+
+		// Substitute into all of the constraints after they are created.
+		for i, ntp := range newTParams {
+			bound := tparams.At(i).Constraint()
+			ntp.SetConstraint(subst.typ(bound))
+		}
+		return fresh
+	}
+
+	// t is declared within the function origin and has type arguments.
+	//
+	// Example: This corresponds to A[int] in F. Cases A and B are handled above.
+	//     func F[T any]() {
+	//       type A[S any] = struct{t T, s S}
+	//       type B = T
+	//       var x A[int]
+	//       ...
+	//     }
+	subOrigin := subst.typ(torigin)
+	subTArgs := subst.typelist(targs)
+	return subst.instantiate(subOrigin, subTArgs)
+}
+
+func (subst *subster) named(t *types.Named) types.Type {
+	// A Named type is a user defined type.
+	// Ignoring generics, Named types are canonical: they are identical if
+	// and only if they have the same defining symbol.
+	// Generics complicate things, both if the type definition itself is
+	// parameterized, and if the type is defined within the scope of a
+	// parameterized function. In this case, two named types are identical if
+	// and only if their identifying symbols are identical, and all type
+	// arguments bindings in scope of the named type definition (including the
+	// type parameters of the definition itself) are equivalent.
+	//
+	// Notably:
+	// 1. For type definition type T[P1 any] struct{}, T[A] and T[B] are identical
+	//    only if A and B are identical.
+	// 2. Inside the generic func Fn[m any]() any { type T struct{}; return T{} },
+	//    the result of Fn[A] and Fn[B] have identical type if and only if A and
+	//    B are identical.
+	// 3. Both 1 and 2 could apply, such as in
+	//    func F[m any]() any { type T[x any] struct{}; return T{} }
+	//
+	// A subster replaces type parameters within a function scope, and therefore must
+	// also replace free type parameters in the definitions of local types.
+	//
+	// Note: There are some detailed notes sprinkled throughout that borrow from
+	// lambda calculus notation. These contain some over simplifying math.
+	//
+	// LC: One way to think about subster is that it is  a way of evaluating
+	//   ((λm. E) N) as E[m:=N].
+	// Each Named type t has an object *TypeName within a scope S that binds an
+	// underlying type expression U. U can refer to symbols within S (+ S's ancestors).
+	// Let x = t.TypeParams() and A = t.TypeArgs().
+	// Each Named type t is then either:
+	//   U              where len(x) == 0 && len(A) == 0
+	//   λx. U          where len(x) != 0 && len(A) == 0
+	//   ((λx. U) A)    where len(x) == len(A)
+	// In each case, we will evaluate t[m:=N].
+	tparams := t.TypeParams() // x
+	targs := t.TypeArgs()     // A
+
+	if !declaredWithin(t.Obj(), subst.origin) {
+		// t is declared outside of Fn[m].
+		//
+		// In this case, we can skip substituting t.Underlying().
+		// The underlying type cannot refer to the type parameters.
+		//
+		// LC: Let free(E) be the set of free type parameters in an expression E.
+		// Then whenever m ∉ free(E), then E = E[m:=N].
+		// t ∉ Scope(fn) so therefore m ∉ free(U) and m ∩ x = ∅.
+		if targs.Len() == 0 {
+			// t has no type arguments. So it does not need to be instantiated.
+			//
+			// This is the normal case in real Go code, where t is not parameterized,
+			// declared at some package scope, and m is a TypeParam from a parameterized
+			// function F[m] or method.
+			//
+			// LC: m ∉ free(A) lets us conclude m ∉ free(t). So t=t[m:=N].
+			return t
+		}
+
+		// t is declared outside of Fn[m] and has type arguments.
+		// The type arguments may contain type parameters m so
+		// substitute the type arguments, and instantiate the substituted
+		// type arguments.
+		//
+		// LC: Evaluate this as ((λx. U) A') where A' = A[m := N].
+		newTArgs := subst.typelist(targs)
+		return subst.instantiate(t.Origin(), newTArgs)
+	}
+
+	// t is declared within Fn[m].
+
+	if targs.Len() == 0 { // no type arguments?
+		assert(t == t.Origin(), "local parameterized type abstraction must be an origin type")
+
+		// t has no type arguments.
+		// The underlying type of t may contain the function's type parameters,
+		// replace these, and create a new type.
+		//
+		// Subtle: We short circuit substitution and use a newly created type in
+		// subst, i.e. cache[t]=fresh, to preemptively replace t with fresh
+		// in recursive types during traversal. This both breaks infinite cycles
+		// and allows for constructing types with the replacement applied in
+		// subst.typ(U).
+		//
+		// A new copy of the Named and Typename (and constraints) per function
+		// instantiation matches the semantics of Go, which treats all function
+		// instantiations F[N] as having distinct local types.
+		//
+		// LC: x.Len()=0 can be thought of as a special case of λx. U.
+		// LC: Evaluate (λx. U)[m:=N] as (λx'. U') where U'=U[x:=x',m:=N].
+		tname := t.Obj()
+		obj := types.NewTypeName(tname.Pos(), tname.Pkg(), tname.Name(), nil)
+		fresh := types.NewNamed(obj, nil, nil)
+		var newTParams []*types.TypeParam
+		for i := 0; i < tparams.Len(); i++ {
+			cur := tparams.At(i)
+			cobj := cur.Obj()
+			cname := types.NewTypeName(cobj.Pos(), cobj.Pkg(), cobj.Name(), nil)
+			ntp := types.NewTypeParam(cname, nil)
+			subst.cache[cur] = ntp
+			newTParams = append(newTParams, ntp)
+		}
+		fresh.SetTypeParams(newTParams)
+		subst.cache[t] = fresh
+		subst.cache[fresh] = fresh
+		fresh.SetUnderlying(subst.typ(t.Underlying()))
+		// Substitute into all of the constraints after they are created.
+		for i, ntp := range newTParams {
+			bound := tparams.At(i).Constraint()
+			ntp.SetConstraint(subst.typ(bound))
+		}
+		return fresh
+	}
+
+	// t is defined within Fn[m] and t has type arguments (an instantiation).
+	// We reduce this to the two cases above:
+	// (1) substitute the function's type parameters into t.Origin().
+	// (2) substitute t's type arguments A and instantiate the updated t.Origin() with these.
+	//
+	// LC: Evaluate ((λx. U) A)[m:=N] as (t' A') where t' = (λx. U)[m:=N] and A'=A [m:=N]
+	subOrigin := subst.typ(t.Origin())
+	subTArgs := subst.typelist(targs)
+	return subst.instantiate(subOrigin, subTArgs)
+}
+
+func (subst *subster) instantiate(orig types.Type, targs []types.Type) types.Type {
+	i, err := types.Instantiate(subst.ctxt, orig, targs, false)
+	assert(err == nil, "failed to Instantiate named (Named or Alias) type")
+	if c, _ := subst.uniqueness.At(i).(types.Type); c != nil {
+		return c.(types.Type)
+	}
+	subst.uniqueness.Set(i, i)
+	return i
+}
+
+func (subst *subster) typelist(l *types.TypeList) []types.Type {
+	res := make([]types.Type, l.Len())
+	for i := 0; i < l.Len(); i++ {
+		res[i] = subst.typ(l.At(i))
+	}
+	return res
+}
+
+func (subst *subster) signature(t *types.Signature) types.Type {
+	tparams := t.TypeParams()
+
+	// We are choosing not to support tparams.Len() > 0 until a need has been observed in practice.
+	//
+	// There are some known usages for types.Types coming from types.{Eval,CheckExpr}.
+	// To support tparams.Len() > 0, we just need to do the following [psuedocode]:
+	//   targs := {subst.replacements[tparams[i]]]}; Instantiate(ctxt, t, targs, false)
+
+	assert(tparams.Len() == 0, "Substituting types.Signatures with generic functions are currently unsupported.")
+
+	// Either:
+	// (1)non-generic function.
+	//    no type params to substitute
+	// (2)generic method and recv needs to be substituted.
+
+	// Receivers can be either:
+	// named
+	// pointer to named
+	// interface
+	// nil
+	// interface is the problematic case. We need to cycle break there!
+	recv := subst.var_(t.Recv())
+	params := subst.tuple(t.Params())
+	results := subst.tuple(t.Results())
+	if recv != t.Recv() || params != t.Params() || results != t.Results() {
+		return types.NewSignatureType(recv, nil, nil, params, results, t.Variadic())
+	}
+	return t
+}
+
+// reaches returns true if a type t reaches any type t' s.t. c[t'] == true.
+// It updates c to cache results.
+//
+// reaches is currently only part of the wellFormed debug logic, and
+// in practice c is initially only type parameters. It is not currently
+// relied on in production.
+func reaches(t types.Type, c map[types.Type]bool) (res bool) {
+	if c, ok := c[t]; ok {
+		return c
+	}
+
+	// c is populated with temporary false entries as types are visited.
+	// This avoids repeat visits and break cycles.
+	c[t] = false
+	defer func() {
+		c[t] = res
+	}()
+
+	switch t := t.(type) {
+	case *types.TypeParam, *types.Basic:
+		return false
+	case *types.Array:
+		return reaches(t.Elem(), c)
+	case *types.Slice:
+		return reaches(t.Elem(), c)
+	case *types.Pointer:
+		return reaches(t.Elem(), c)
+	case *types.Tuple:
+		for i := 0; i < t.Len(); i++ {
+			if reaches(t.At(i).Type(), c) {
+				return true
+			}
+		}
+	case *types.Struct:
+		for i := 0; i < t.NumFields(); i++ {
+			if reaches(t.Field(i).Type(), c) {
+				return true
+			}
+		}
+	case *types.Map:
+		return reaches(t.Key(), c) || reaches(t.Elem(), c)
+	case *types.Chan:
+		return reaches(t.Elem(), c)
+	case *types.Signature:
+		if t.Recv() != nil && reaches(t.Recv().Type(), c) {
+			return true
+		}
+		return reaches(t.Params(), c) || reaches(t.Results(), c)
+	case *types.Union:
+		for i := 0; i < t.Len(); i++ {
+			if reaches(t.Term(i).Type(), c) {
+				return true
+			}
+		}
+	case *types.Interface:
+		for i := 0; i < t.NumEmbeddeds(); i++ {
+			if reaches(t.Embedded(i), c) {
+				return true
+			}
+		}
+		for i := 0; i < t.NumExplicitMethods(); i++ {
+			if reaches(t.ExplicitMethod(i).Type(), c) {
+				return true
+			}
+		}
+	case *types.Named, *aliases.Alias:
+		return reaches(t.Underlying(), c)
+	default:
+		panic("unreachable")
+	}
+	return false
+}
diff --git a/vendor/golang.org/x/tools/go/ssa/task.go b/vendor/golang.org/x/tools/go/ssa/task.go
new file mode 100644
index 0000000..5024985
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ssa/task.go
@@ -0,0 +1,103 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+import (
+	"sync/atomic"
+)
+
+// Each task has two states: it is initially "active",
+// and transitions to "done".
+//
+// tasks form a directed graph. An edge from x to y (with y in x.edges)
+// indicates that the task x waits on the task y to be done.
+// Cycles are permitted.
+//
+// Calling x.wait() blocks the calling goroutine until task x,
+// and all the tasks transitively reachable from x are done.
+//
+// The nil *task is always considered done.
+type task struct {
+	done       chan unit      // close when the task is done.
+	edges      map[*task]unit // set of predecessors of this task.
+	transitive atomic.Bool    // true once it is known all predecessors are done.
+}
+
+func (x *task) isTransitivelyDone() bool { return x == nil || x.transitive.Load() }
+
+// addEdge creates an edge from x to y, indicating that
+// x.wait() will not return before y is done.
+// All calls to x.addEdge(...) should happen before x.markDone().
+func (x *task) addEdge(y *task) {
+	if x == y || y.isTransitivelyDone() {
+		return // no work remaining
+	}
+
+	// heuristic done check
+	select {
+	case <-x.done:
+		panic("cannot add an edge to a done task")
+	default:
+	}
+
+	if x.edges == nil {
+		x.edges = make(map[*task]unit)
+	}
+	x.edges[y] = unit{}
+}
+
+// markDone changes the task's state to markDone.
+func (x *task) markDone() {
+	if x != nil {
+		close(x.done)
+	}
+}
+
+// wait blocks until x and all the tasks it can reach through edges are done.
+func (x *task) wait() {
+	if x.isTransitivelyDone() {
+		return // already known to be done. Skip allocations.
+	}
+
+	// Use BFS to wait on u.done to be closed, for all u transitively
+	// reachable from x via edges.
+	//
+	// This work can be repeated by multiple workers doing wait().
+	//
+	// Note: Tarjan's SCC algorithm is able to mark SCCs as transitively done
+	// as soon as the SCC has been visited. This is theoretically faster, but is
+	// a more complex algorithm. Until we have evidence, we need the more complex
+	// algorithm, the simpler algorithm BFS is implemented.
+	//
+	// In Go 1.23, ssa/TestStdlib reaches <=3 *tasks per wait() in most schedules
+	// On some schedules, there is a cycle building net/http and internal/trace/testtrace
+	// due to slices functions.
+	work := []*task{x}
+	enqueued := map[*task]unit{x: {}}
+	for i := 0; i < len(work); i++ {
+		u := work[i]
+		if u.isTransitivelyDone() { // already transitively done
+			work[i] = nil
+			continue
+		}
+		<-u.done // wait for u to be marked done.
+
+		for v := range u.edges {
+			if _, ok := enqueued[v]; !ok {
+				enqueued[v] = unit{}
+				work = append(work, v)
+			}
+		}
+	}
+
+	// work is transitively closed over dependencies.
+	// u in work is done (or transitively done and skipped).
+	// u is transitively done.
+	for _, u := range work {
+		if u != nil {
+			x.transitive.Store(true)
+		}
+	}
+}
diff --git a/vendor/golang.org/x/tools/go/ssa/util.go b/vendor/golang.org/x/tools/go/ssa/util.go
new file mode 100644
index 0000000..549c9c8
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ssa/util.go
@@ -0,0 +1,430 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// This file defines a number of miscellaneous utility functions.
+
+import (
+	"fmt"
+	"go/ast"
+	"go/token"
+	"go/types"
+	"io"
+	"os"
+	"sync"
+
+	"golang.org/x/tools/go/ast/astutil"
+	"golang.org/x/tools/go/types/typeutil"
+	"golang.org/x/tools/internal/aliases"
+	"golang.org/x/tools/internal/typeparams"
+	"golang.org/x/tools/internal/typesinternal"
+)
+
+type unit struct{}
+
+//// Sanity checking utilities
+
+// assert panics with the mesage msg if p is false.
+// Avoid combining with expensive string formatting.
+func assert(p bool, msg string) {
+	if !p {
+		panic(msg)
+	}
+}
+
+//// AST utilities
+
+func unparen(e ast.Expr) ast.Expr { return astutil.Unparen(e) }
+
+// isBlankIdent returns true iff e is an Ident with name "_".
+// They have no associated types.Object, and thus no type.
+func isBlankIdent(e ast.Expr) bool {
+	id, ok := e.(*ast.Ident)
+	return ok && id.Name == "_"
+}
+
+// rangePosition is the position to give for the `range` token in a RangeStmt.
+var rangePosition = func(rng *ast.RangeStmt) token.Pos {
+	// Before 1.20, this is unreachable.
+	// rng.For is a close, but incorrect position.
+	return rng.For
+}
+
+//// Type utilities.  Some of these belong in go/types.
+
+// isNonTypeParamInterface reports whether t is an interface type but not a type parameter.
+func isNonTypeParamInterface(t types.Type) bool {
+	return !typeparams.IsTypeParam(t) && types.IsInterface(t)
+}
+
+// isBasic reports whether t is a basic type.
+// t is assumed to be an Underlying type (not Named or Alias).
+func isBasic(t types.Type) bool {
+	_, ok := t.(*types.Basic)
+	return ok
+}
+
+// isString reports whether t is exactly a string type.
+// t is assumed to be an Underlying type (not Named or Alias).
+func isString(t types.Type) bool {
+	basic, ok := t.(*types.Basic)
+	return ok && basic.Info()&types.IsString != 0
+}
+
+// isByteSlice reports whether t is of the form []~bytes.
+// t is assumed to be an Underlying type (not Named or Alias).
+func isByteSlice(t types.Type) bool {
+	if b, ok := t.(*types.Slice); ok {
+		e, _ := b.Elem().Underlying().(*types.Basic)
+		return e != nil && e.Kind() == types.Byte
+	}
+	return false
+}
+
+// isRuneSlice reports whether t is of the form []~runes.
+// t is assumed to be an Underlying type (not Named or Alias).
+func isRuneSlice(t types.Type) bool {
+	if b, ok := t.(*types.Slice); ok {
+		e, _ := b.Elem().Underlying().(*types.Basic)
+		return e != nil && e.Kind() == types.Rune
+	}
+	return false
+}
+
+// isBasicConvTypes returns true when a type set can be
+// one side of a Convert operation. This is when:
+// - All are basic, []byte, or []rune.
+// - At least 1 is basic.
+// - At most 1 is []byte or []rune.
+func isBasicConvTypes(tset termList) bool {
+	basics := 0
+	all := underIs(tset, func(t types.Type) bool {
+		if isBasic(t) {
+			basics++
+			return true
+		}
+		return isByteSlice(t) || isRuneSlice(t)
+	})
+	return all && basics >= 1 && tset.Len()-basics <= 1
+}
+
+// isPointer reports whether t's underlying type is a pointer.
+func isPointer(t types.Type) bool {
+	return is[*types.Pointer](t.Underlying())
+}
+
+// isPointerCore reports whether t's core type is a pointer.
+//
+// (Most pointer manipulation is related to receivers, in which case
+// isPointer is appropriate. tecallers can use isPointer(t).
+func isPointerCore(t types.Type) bool {
+	return is[*types.Pointer](typeparams.CoreType(t))
+}
+
+func is[T any](x any) bool {
+	_, ok := x.(T)
+	return ok
+}
+
+// recvType returns the receiver type of method obj.
+func recvType(obj *types.Func) types.Type {
+	return obj.Type().(*types.Signature).Recv().Type()
+}
+
+// fieldOf returns the index'th field of the (core type of) a struct type;
+// otherwise returns nil.
+func fieldOf(typ types.Type, index int) *types.Var {
+	if st, ok := typeparams.CoreType(typ).(*types.Struct); ok {
+		if 0 <= index && index < st.NumFields() {
+			return st.Field(index)
+		}
+	}
+	return nil
+}
+
+// isUntyped reports whether typ is the type of an untyped constant.
+func isUntyped(typ types.Type) bool {
+	// No Underlying/Unalias: untyped constant types cannot be Named or Alias.
+	b, ok := typ.(*types.Basic)
+	return ok && b.Info()&types.IsUntyped != 0
+}
+
+// declaredWithin reports whether an object is declared within a function.
+//
+// obj must not be a method or a field.
+func declaredWithin(obj types.Object, fn *types.Func) bool {
+	if obj.Pos() != token.NoPos {
+		return fn.Scope().Contains(obj.Pos()) // trust the positions if they exist.
+	}
+	if fn.Pkg() != obj.Pkg() {
+		return false // fast path for different packages
+	}
+
+	// Traverse Parent() scopes for fn.Scope().
+	for p := obj.Parent(); p != nil; p = p.Parent() {
+		if p == fn.Scope() {
+			return true
+		}
+	}
+	return false
+}
+
+// logStack prints the formatted "start" message to stderr and
+// returns a closure that prints the corresponding "end" message.
+// Call using 'defer logStack(...)()' to show builder stack on panic.
+// Don't forget trailing parens!
+func logStack(format string, args ...interface{}) func() {
+	msg := fmt.Sprintf(format, args...)
+	io.WriteString(os.Stderr, msg)
+	io.WriteString(os.Stderr, "\n")
+	return func() {
+		io.WriteString(os.Stderr, msg)
+		io.WriteString(os.Stderr, " end\n")
+	}
+}
+
+// newVar creates a 'var' for use in a types.Tuple.
+func newVar(name string, typ types.Type) *types.Var {
+	return types.NewParam(token.NoPos, nil, name, typ)
+}
+
+// anonVar creates an anonymous 'var' for use in a types.Tuple.
+func anonVar(typ types.Type) *types.Var {
+	return newVar("", typ)
+}
+
+var lenResults = types.NewTuple(anonVar(tInt))
+
+// makeLen returns the len builtin specialized to type func(T)int.
+func makeLen(T types.Type) *Builtin {
+	lenParams := types.NewTuple(anonVar(T))
+	return &Builtin{
+		name: "len",
+		sig:  types.NewSignature(nil, lenParams, lenResults, false),
+	}
+}
+
+// receiverTypeArgs returns the type arguments to a method's receiver.
+// Returns an empty list if the receiver does not have type arguments.
+func receiverTypeArgs(method *types.Func) []types.Type {
+	recv := method.Type().(*types.Signature).Recv()
+	_, named := typesinternal.ReceiverNamed(recv)
+	if named == nil {
+		return nil // recv is anonymous struct/interface
+	}
+	ts := named.TypeArgs()
+	if ts.Len() == 0 {
+		return nil
+	}
+	targs := make([]types.Type, ts.Len())
+	for i := 0; i < ts.Len(); i++ {
+		targs[i] = ts.At(i)
+	}
+	return targs
+}
+
+// recvAsFirstArg takes a method signature and returns a function
+// signature with receiver as the first parameter.
+func recvAsFirstArg(sig *types.Signature) *types.Signature {
+	params := make([]*types.Var, 0, 1+sig.Params().Len())
+	params = append(params, sig.Recv())
+	for i := 0; i < sig.Params().Len(); i++ {
+		params = append(params, sig.Params().At(i))
+	}
+	return types.NewSignatureType(nil, nil, nil, types.NewTuple(params...), sig.Results(), sig.Variadic())
+}
+
+// instance returns whether an expression is a simple or qualified identifier
+// that is a generic instantiation.
+func instance(info *types.Info, expr ast.Expr) bool {
+	// Compare the logic here against go/types.instantiatedIdent,
+	// which also handles  *IndexExpr and *IndexListExpr.
+	var id *ast.Ident
+	switch x := expr.(type) {
+	case *ast.Ident:
+		id = x
+	case *ast.SelectorExpr:
+		id = x.Sel
+	default:
+		return false
+	}
+	_, ok := info.Instances[id]
+	return ok
+}
+
+// instanceArgs returns the Instance[id].TypeArgs as a slice.
+func instanceArgs(info *types.Info, id *ast.Ident) []types.Type {
+	targList := info.Instances[id].TypeArgs
+	if targList == nil {
+		return nil
+	}
+
+	targs := make([]types.Type, targList.Len())
+	for i, n := 0, targList.Len(); i < n; i++ {
+		targs[i] = targList.At(i)
+	}
+	return targs
+}
+
+// Mapping of a type T to a canonical instance C s.t. types.Indentical(T, C).
+// Thread-safe.
+type canonizer struct {
+	mu    sync.Mutex
+	types typeutil.Map // map from type to a canonical instance
+	lists typeListMap  // map from a list of types to a canonical instance
+}
+
+func newCanonizer() *canonizer {
+	c := &canonizer{}
+	h := typeutil.MakeHasher()
+	c.types.SetHasher(h)
+	c.lists.hasher = h
+	return c
+}
+
+// List returns a canonical representative of a list of types.
+// Representative of the empty list is nil.
+func (c *canonizer) List(ts []types.Type) *typeList {
+	if len(ts) == 0 {
+		return nil
+	}
+
+	unaliasAll := func(ts []types.Type) []types.Type {
+		// Is there some top level alias?
+		var found bool
+		for _, t := range ts {
+			if _, ok := t.(*aliases.Alias); ok {
+				found = true
+				break
+			}
+		}
+		if !found {
+			return ts // no top level alias
+		}
+
+		cp := make([]types.Type, len(ts)) // copy with top level aliases removed.
+		for i, t := range ts {
+			cp[i] = aliases.Unalias(t)
+		}
+		return cp
+	}
+	l := unaliasAll(ts)
+
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	return c.lists.rep(l)
+}
+
+// Type returns a canonical representative of type T.
+// Removes top-level aliases.
+//
+// For performance, reasons the canonical instance is order-dependent,
+// and may contain deeply nested aliases.
+func (c *canonizer) Type(T types.Type) types.Type {
+	T = aliases.Unalias(T) // remove the top level alias.
+
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	if r := c.types.At(T); r != nil {
+		return r.(types.Type)
+	}
+	c.types.Set(T, T)
+	return T
+}
+
+// A type for representing a canonized list of types.
+type typeList []types.Type
+
+func (l *typeList) identical(ts []types.Type) bool {
+	if l == nil {
+		return len(ts) == 0
+	}
+	n := len(*l)
+	if len(ts) != n {
+		return false
+	}
+	for i, left := range *l {
+		right := ts[i]
+		if !types.Identical(left, right) {
+			return false
+		}
+	}
+	return true
+}
+
+type typeListMap struct {
+	hasher  typeutil.Hasher
+	buckets map[uint32][]*typeList
+}
+
+// rep returns a canonical representative of a slice of types.
+func (m *typeListMap) rep(ts []types.Type) *typeList {
+	if m == nil || len(ts) == 0 {
+		return nil
+	}
+
+	if m.buckets == nil {
+		m.buckets = make(map[uint32][]*typeList)
+	}
+
+	h := m.hash(ts)
+	bucket := m.buckets[h]
+	for _, l := range bucket {
+		if l.identical(ts) {
+			return l
+		}
+	}
+
+	// not present. create a representative.
+	cp := make(typeList, len(ts))
+	copy(cp, ts)
+	rep := &cp
+
+	m.buckets[h] = append(bucket, rep)
+	return rep
+}
+
+func (m *typeListMap) hash(ts []types.Type) uint32 {
+	if m == nil {
+		return 0
+	}
+	// Some smallish prime far away from typeutil.Hash.
+	n := len(ts)
+	h := uint32(13619) + 2*uint32(n)
+	for i := 0; i < n; i++ {
+		h += 3 * m.hasher.Hash(ts[i])
+	}
+	return h
+}
+
+// instantiateMethod instantiates m with targs and returns a canonical representative for this method.
+func (canon *canonizer) instantiateMethod(m *types.Func, targs []types.Type, ctxt *types.Context) *types.Func {
+	recv := recvType(m)
+	if p, ok := aliases.Unalias(recv).(*types.Pointer); ok {
+		recv = p.Elem()
+	}
+	named := aliases.Unalias(recv).(*types.Named)
+	inst, err := types.Instantiate(ctxt, named.Origin(), targs, false)
+	if err != nil {
+		panic(err)
+	}
+	rep := canon.Type(inst)
+	obj, _, _ := types.LookupFieldOrMethod(rep, true, m.Pkg(), m.Name())
+	return obj.(*types.Func)
+}
+
+// Exposed to ssautil using the linkname hack.
+func isSyntactic(pkg *Package) bool { return pkg.syntax }
+
+// mapValues returns a new unordered array of map values.
+func mapValues[K comparable, V any](m map[K]V) []V {
+	vals := make([]V, 0, len(m))
+	for _, fn := range m {
+		vals = append(vals, fn)
+	}
+	return vals
+
+}
diff --git a/vendor/golang.org/x/tools/go/ssa/util_go120.go b/vendor/golang.org/x/tools/go/ssa/util_go120.go
new file mode 100644
index 0000000..9e8ea87
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ssa/util_go120.go
@@ -0,0 +1,17 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build go1.20
+// +build go1.20
+
+package ssa
+
+import (
+	"go/ast"
+	"go/token"
+)
+
+func init() {
+	rangePosition = func(rng *ast.RangeStmt) token.Pos { return rng.Range }
+}
diff --git a/vendor/golang.org/x/tools/go/ssa/wrappers.go b/vendor/golang.org/x/tools/go/ssa/wrappers.go
new file mode 100644
index 0000000..d09b4f2
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/ssa/wrappers.go
@@ -0,0 +1,348 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// This file defines synthesis of Functions that delegate to declared
+// methods; they come in three kinds:
+//
+// (1) wrappers: methods that wrap declared methods, performing
+//     implicit pointer indirections and embedded field selections.
+//
+// (2) thunks: funcs that wrap declared methods.  Like wrappers,
+//     thunks perform indirections and field selections. The thunk's
+//     first parameter is used as the receiver for the method call.
+//
+// (3) bounds: funcs that wrap declared methods.  The bound's sole
+//     free variable, supplied by a closure, is used as the receiver
+//     for the method call.  No indirections or field selections are
+//     performed since they can be done before the call.
+
+import (
+	"fmt"
+
+	"go/token"
+	"go/types"
+
+	"golang.org/x/tools/internal/typeparams"
+)
+
+// -- wrappers -----------------------------------------------------------
+
+// createWrapper returns a synthetic method that delegates to the
+// declared method denoted by meth.Obj(), first performing any
+// necessary pointer indirections or field selections implied by meth.
+//
+// The resulting method's receiver type is meth.Recv().
+//
+// This function is versatile but quite subtle!  Consider the
+// following axes of variation when making changes:
+//   - optional receiver indirection
+//   - optional implicit field selections
+//   - meth.Obj() may denote a concrete or an interface method
+//   - the result may be a thunk or a wrapper.
+func createWrapper(prog *Program, sel *selection) *Function {
+	obj := sel.obj.(*types.Func)      // the declared function
+	sig := sel.typ.(*types.Signature) // type of this wrapper
+
+	var recv *types.Var // wrapper's receiver or thunk's params[0]
+	name := obj.Name()
+	var description string
+	if sel.kind == types.MethodExpr {
+		name += "$thunk"
+		description = "thunk"
+		recv = sig.Params().At(0)
+	} else {
+		description = "wrapper"
+		recv = sig.Recv()
+	}
+
+	description = fmt.Sprintf("%s for %s", description, sel.obj)
+	if prog.mode&LogSource != 0 {
+		defer logStack("create %s to (%s)", description, recv.Type())()
+	}
+	/* method wrapper */
+	return &Function{
+		name:      name,
+		method:    sel,
+		object:    obj,
+		Signature: sig,
+		Synthetic: description,
+		Prog:      prog,
+		pos:       obj.Pos(),
+		// wrappers have no syntax
+		build:     (*builder).buildWrapper,
+		syntax:    nil,
+		info:      nil,
+		goversion: "",
+	}
+}
+
+// buildWrapper builds fn.Body for a method wrapper.
+func (b *builder) buildWrapper(fn *Function) {
+	var recv *types.Var // wrapper's receiver or thunk's params[0]
+	var start int       // first regular param
+	if fn.method.kind == types.MethodExpr {
+		recv = fn.Signature.Params().At(0)
+		start = 1
+	} else {
+		recv = fn.Signature.Recv()
+	}
+
+	fn.startBody()
+	fn.addSpilledParam(recv)
+	createParams(fn, start)
+
+	indices := fn.method.index
+
+	var v Value = fn.Locals[0] // spilled receiver
+	if isPointer(fn.method.recv) {
+		v = emitLoad(fn, v)
+
+		// For simple indirection wrappers, perform an informative nil-check:
+		// "value method (T).f called using nil *T pointer"
+		if len(indices) == 1 && !isPointer(recvType(fn.object)) {
+			var c Call
+			c.Call.Value = &Builtin{
+				name: "ssa:wrapnilchk",
+				sig: types.NewSignature(nil,
+					types.NewTuple(anonVar(fn.method.recv), anonVar(tString), anonVar(tString)),
+					types.NewTuple(anonVar(fn.method.recv)), false),
+			}
+			c.Call.Args = []Value{
+				v,
+				stringConst(typeparams.MustDeref(fn.method.recv).String()),
+				stringConst(fn.method.obj.Name()),
+			}
+			c.setType(v.Type())
+			v = fn.emit(&c)
+		}
+	}
+
+	// Invariant: v is a pointer, either
+	//   value of *A receiver param, or
+	// address of  A spilled receiver.
+
+	// We use pointer arithmetic (FieldAddr possibly followed by
+	// Load) in preference to value extraction (Field possibly
+	// preceded by Load).
+
+	v = emitImplicitSelections(fn, v, indices[:len(indices)-1], token.NoPos)
+
+	// Invariant: v is a pointer, either
+	//   value of implicit *C field, or
+	// address of implicit  C field.
+
+	var c Call
+	if r := recvType(fn.object); !types.IsInterface(r) { // concrete method
+		if !isPointer(r) {
+			v = emitLoad(fn, v)
+		}
+		c.Call.Value = fn.Prog.objectMethod(fn.object, b)
+		c.Call.Args = append(c.Call.Args, v)
+	} else {
+		c.Call.Method = fn.object
+		c.Call.Value = emitLoad(fn, v) // interface (possibly a typeparam)
+	}
+	for _, arg := range fn.Params[1:] {
+		c.Call.Args = append(c.Call.Args, arg)
+	}
+	emitTailCall(fn, &c)
+	fn.finishBody()
+}
+
+// createParams creates parameters for wrapper method fn based on its
+// Signature.Params, which do not include the receiver.
+// start is the index of the first regular parameter to use.
+func createParams(fn *Function, start int) {
+	tparams := fn.Signature.Params()
+	for i, n := start, tparams.Len(); i < n; i++ {
+		fn.addParamVar(tparams.At(i))
+	}
+}
+
+// -- bounds -----------------------------------------------------------
+
+// createBound returns a bound method wrapper (or "bound"), a synthetic
+// function that delegates to a concrete or interface method denoted
+// by obj.  The resulting function has no receiver, but has one free
+// variable which will be used as the method's receiver in the
+// tail-call.
+//
+// Use MakeClosure with such a wrapper to construct a bound method
+// closure.  e.g.:
+//
+//	type T int          or:  type T interface { meth() }
+//	func (t T) meth()
+//	var t T
+//	f := t.meth
+//	f() // calls t.meth()
+//
+// f is a closure of a synthetic wrapper defined as if by:
+//
+//	f := func() { return t.meth() }
+//
+// Unlike createWrapper, createBound need perform no indirection or field
+// selections because that can be done before the closure is
+// constructed.
+func createBound(prog *Program, obj *types.Func) *Function {
+	description := fmt.Sprintf("bound method wrapper for %s", obj)
+	if prog.mode&LogSource != 0 {
+		defer logStack("%s", description)()
+	}
+	/* bound method wrapper */
+	fn := &Function{
+		name:      obj.Name() + "$bound",
+		object:    obj,
+		Signature: changeRecv(obj.Type().(*types.Signature), nil), // drop receiver
+		Synthetic: description,
+		Prog:      prog,
+		pos:       obj.Pos(),
+		// wrappers have no syntax
+		build:     (*builder).buildBound,
+		syntax:    nil,
+		info:      nil,
+		goversion: "",
+	}
+	fn.FreeVars = []*FreeVar{{name: "recv", typ: recvType(obj), parent: fn}} // (cyclic)
+	return fn
+}
+
+// buildBound builds fn.Body for a bound method closure.
+func (b *builder) buildBound(fn *Function) {
+	fn.startBody()
+	createParams(fn, 0)
+	var c Call
+
+	recv := fn.FreeVars[0]
+	if !types.IsInterface(recvType(fn.object)) { // concrete
+		c.Call.Value = fn.Prog.objectMethod(fn.object, b)
+		c.Call.Args = []Value{recv}
+	} else {
+		c.Call.Method = fn.object
+		c.Call.Value = recv // interface (possibly a typeparam)
+	}
+	for _, arg := range fn.Params {
+		c.Call.Args = append(c.Call.Args, arg)
+	}
+	emitTailCall(fn, &c)
+	fn.finishBody()
+}
+
+// -- thunks -----------------------------------------------------------
+
+// createThunk returns a thunk, a synthetic function that delegates to a
+// concrete or interface method denoted by sel.obj.  The resulting
+// function has no receiver, but has an additional (first) regular
+// parameter.
+//
+// Precondition: sel.kind == types.MethodExpr.
+//
+//	type T int          or:  type T interface { meth() }
+//	func (t T) meth()
+//	f := T.meth
+//	var t T
+//	f(t) // calls t.meth()
+//
+// f is a synthetic wrapper defined as if by:
+//
+//	f := func(t T) { return t.meth() }
+func createThunk(prog *Program, sel *selection) *Function {
+	if sel.kind != types.MethodExpr {
+		panic(sel)
+	}
+
+	fn := createWrapper(prog, sel)
+	if fn.Signature.Recv() != nil {
+		panic(fn) // unexpected receiver
+	}
+
+	return fn
+}
+
+func changeRecv(s *types.Signature, recv *types.Var) *types.Signature {
+	return types.NewSignature(recv, s.Params(), s.Results(), s.Variadic())
+}
+
+// A local version of *types.Selection.
+// Needed for some additional control, such as creating a MethodExpr for an instantiation.
+type selection struct {
+	kind     types.SelectionKind
+	recv     types.Type
+	typ      types.Type
+	obj      types.Object
+	index    []int
+	indirect bool
+}
+
+func toSelection(sel *types.Selection) *selection {
+	return &selection{
+		kind:     sel.Kind(),
+		recv:     sel.Recv(),
+		typ:      sel.Type(),
+		obj:      sel.Obj(),
+		index:    sel.Index(),
+		indirect: sel.Indirect(),
+	}
+}
+
+// -- instantiations --------------------------------------------------
+
+// buildInstantiationWrapper builds the body of an instantiation
+// wrapper fn. The body calls the original generic function,
+// bracketed by ChangeType conversions on its arguments and results.
+func (b *builder) buildInstantiationWrapper(fn *Function) {
+	orig := fn.topLevelOrigin
+	sig := fn.Signature
+
+	fn.startBody()
+	if sig.Recv() != nil {
+		fn.addParamVar(sig.Recv())
+	}
+	createParams(fn, 0)
+
+	// Create body. Add a call to origin generic function
+	// and make type changes between argument and parameters,
+	// as well as return values.
+	var c Call
+	c.Call.Value = orig
+	if res := orig.Signature.Results(); res.Len() == 1 {
+		c.typ = res.At(0).Type()
+	} else {
+		c.typ = res
+	}
+
+	// parameter of instance becomes an argument to the call
+	// to the original generic function.
+	argOffset := 0
+	for i, arg := range fn.Params {
+		var typ types.Type
+		if i == 0 && sig.Recv() != nil {
+			typ = orig.Signature.Recv().Type()
+			argOffset = 1
+		} else {
+			typ = orig.Signature.Params().At(i - argOffset).Type()
+		}
+		c.Call.Args = append(c.Call.Args, emitTypeCoercion(fn, arg, typ))
+	}
+
+	results := fn.emit(&c)
+	var ret Return
+	switch res := sig.Results(); res.Len() {
+	case 0:
+		// no results, do nothing.
+	case 1:
+		ret.Results = []Value{emitTypeCoercion(fn, results, res.At(0).Type())}
+	default:
+		for i := 0; i < sig.Results().Len(); i++ {
+			v := emitExtract(fn, results, i)
+			ret.Results = append(ret.Results, emitTypeCoercion(fn, v, res.At(i).Type()))
+		}
+	}
+
+	fn.emit(&ret)
+	fn.currentBlock = nil
+
+	fn.finishBody()
+}
diff --git a/vendor/golang.org/x/tools/go/types/objectpath/objectpath.go b/vendor/golang.org/x/tools/go/types/objectpath/objectpath.go
new file mode 100644
index 0000000..9ada177
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/types/objectpath/objectpath.go
@@ -0,0 +1,788 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package objectpath defines a naming scheme for types.Objects
+// (that is, named entities in Go programs) relative to their enclosing
+// package.
+//
+// Type-checker objects are canonical, so they are usually identified by
+// their address in memory (a pointer), but a pointer has meaning only
+// within one address space. By contrast, objectpath names allow the
+// identity of an object to be sent from one program to another,
+// establishing a correspondence between types.Object variables that are
+// distinct but logically equivalent.
+//
+// A single object may have multiple paths. In this example,
+//
+//	type A struct{ X int }
+//	type B A
+//
+// the field X has two paths due to its membership of both A and B.
+// The For(obj) function always returns one of these paths, arbitrarily
+// but consistently.
+package objectpath
+
+import (
+	"fmt"
+	"go/types"
+	"strconv"
+	"strings"
+
+	"golang.org/x/tools/internal/aliases"
+	"golang.org/x/tools/internal/typesinternal"
+)
+
+// TODO(adonovan): think about generic aliases.
+
+// A Path is an opaque name that identifies a types.Object
+// relative to its package. Conceptually, the name consists of a
+// sequence of destructuring operations applied to the package scope
+// to obtain the original object.
+// The name does not include the package itself.
+type Path string
+
+// Encoding
+//
+// An object path is a textual and (with training) human-readable encoding
+// of a sequence of destructuring operators, starting from a types.Package.
+// The sequences represent a path through the package/object/type graph.
+// We classify these operators by their type:
+//
+//	PO package->object	Package.Scope.Lookup
+//	OT  object->type 	Object.Type
+//	TT    type->type 	Type.{Elem,Key,{,{,Recv}Type}Params,Results,Underlying,Rhs} [EKPRUTrCa]
+//	TO   type->object	Type.{At,Field,Method,Obj} [AFMO]
+//
+// All valid paths start with a package and end at an object
+// and thus may be defined by the regular language:
+//
+//	objectpath = PO (OT TT* TO)*
+//
+// The concrete encoding follows directly:
+//   - The only PO operator is Package.Scope.Lookup, which requires an identifier.
+//   - The only OT operator is Object.Type,
+//     which we encode as '.' because dot cannot appear in an identifier.
+//   - The TT operators are encoded as [EKPRUTrCa];
+//     two of these ({,Recv}TypeParams) require an integer operand,
+//     which is encoded as a string of decimal digits.
+//   - The TO operators are encoded as [AFMO];
+//     three of these (At,Field,Method) require an integer operand,
+//     which is encoded as a string of decimal digits.
+//     These indices are stable across different representations
+//     of the same package, even source and export data.
+//     The indices used are implementation specific and may not correspond to
+//     the argument to the go/types function.
+//
+// In the example below,
+//
+//	package p
+//
+//	type T interface {
+//		f() (a string, b struct{ X int })
+//	}
+//
+// field X has the path "T.UM0.RA1.F0",
+// representing the following sequence of operations:
+//
+//	p.Lookup("T")					T
+//	.Type().Underlying().Method(0).			f
+//	.Type().Results().At(1)				b
+//	.Type().Field(0)					X
+//
+// The encoding is not maximally compact---every R or P is
+// followed by an A, for example---but this simplifies the
+// encoder and decoder.
+const (
+	// object->type operators
+	opType = '.' // .Type()		  (Object)
+
+	// type->type operators
+	opElem          = 'E' // .Elem()		(Pointer, Slice, Array, Chan, Map)
+	opKey           = 'K' // .Key()			(Map)
+	opParams        = 'P' // .Params()		(Signature)
+	opResults       = 'R' // .Results()		(Signature)
+	opUnderlying    = 'U' // .Underlying()		(Named)
+	opTypeParam     = 'T' // .TypeParams.At(i)	(Named, Signature)
+	opRecvTypeParam = 'r' // .RecvTypeParams.At(i)	(Signature)
+	opConstraint    = 'C' // .Constraint()		(TypeParam)
+	opRhs           = 'a' // .Rhs()			(Alias)
+
+	// type->object operators
+	opAt     = 'A' // .At(i)	(Tuple)
+	opField  = 'F' // .Field(i)	(Struct)
+	opMethod = 'M' // .Method(i)	(Named or Interface; not Struct: "promoted" names are ignored)
+	opObj    = 'O' // .Obj()	(Named, TypeParam)
+)
+
+// For is equivalent to new(Encoder).For(obj).
+//
+// It may be more efficient to reuse a single Encoder across several calls.
+func For(obj types.Object) (Path, error) {
+	return new(Encoder).For(obj)
+}
+
+// An Encoder amortizes the cost of encoding the paths of multiple objects.
+// The zero value of an Encoder is ready to use.
+type Encoder struct {
+	scopeMemo map[*types.Scope][]types.Object // memoization of scopeObjects
+}
+
+// For returns the path to an object relative to its package,
+// or an error if the object is not accessible from the package's Scope.
+//
+// The For function guarantees to return a path only for the following objects:
+// - package-level types
+// - exported package-level non-types
+// - methods
+// - parameter and result variables
+// - struct fields
+// These objects are sufficient to define the API of their package.
+// The objects described by a package's export data are drawn from this set.
+//
+// The set of objects accessible from a package's Scope depends on
+// whether the package was produced by type-checking syntax, or
+// reading export data; the latter may have a smaller Scope since
+// export data trims objects that are not reachable from an exported
+// declaration. For example, the For function will return a path for
+// an exported method of an unexported type that is not reachable
+// from any public declaration; this path will cause the Object
+// function to fail if called on a package loaded from export data.
+// TODO(adonovan): is this a bug or feature? Should this package
+// compute accessibility in the same way?
+//
+// For does not return a path for predeclared names, imported package
+// names, local names, and unexported package-level names (except
+// types).
+//
+// Example: given this definition,
+//
+//	package p
+//
+//	type T interface {
+//		f() (a string, b struct{ X int })
+//	}
+//
+// For(X) would return a path that denotes the following sequence of operations:
+//
+//	p.Scope().Lookup("T")				(TypeName T)
+//	.Type().Underlying().Method(0).			(method Func f)
+//	.Type().Results().At(1)				(field Var b)
+//	.Type().Field(0)					(field Var X)
+//
+// where p is the package (*types.Package) to which X belongs.
+func (enc *Encoder) For(obj types.Object) (Path, error) {
+	pkg := obj.Pkg()
+
+	// This table lists the cases of interest.
+	//
+	// Object				Action
+	// ------                               ------
+	// nil					reject
+	// builtin				reject
+	// pkgname				reject
+	// label				reject
+	// var
+	//    package-level			accept
+	//    func param/result			accept
+	//    local				reject
+	//    struct field			accept
+	// const
+	//    package-level			accept
+	//    local				reject
+	// func
+	//    package-level			accept
+	//    init functions			reject
+	//    concrete method			accept
+	//    interface method			accept
+	// type
+	//    package-level			accept
+	//    local				reject
+	//
+	// The only accessible package-level objects are members of pkg itself.
+	//
+	// The cases are handled in four steps:
+	//
+	// 1. reject nil and builtin
+	// 2. accept package-level objects
+	// 3. reject obviously invalid objects
+	// 4. search the API for the path to the param/result/field/method.
+
+	// 1. reference to nil or builtin?
+	if pkg == nil {
+		return "", fmt.Errorf("predeclared %s has no path", obj)
+	}
+	scope := pkg.Scope()
+
+	// 2. package-level object?
+	if scope.Lookup(obj.Name()) == obj {
+		// Only exported objects (and non-exported types) have a path.
+		// Non-exported types may be referenced by other objects.
+		if _, ok := obj.(*types.TypeName); !ok && !obj.Exported() {
+			return "", fmt.Errorf("no path for non-exported %v", obj)
+		}
+		return Path(obj.Name()), nil
+	}
+
+	// 3. Not a package-level object.
+	//    Reject obviously non-viable cases.
+	switch obj := obj.(type) {
+	case *types.TypeName:
+		if _, ok := aliases.Unalias(obj.Type()).(*types.TypeParam); !ok {
+			// With the exception of type parameters, only package-level type names
+			// have a path.
+			return "", fmt.Errorf("no path for %v", obj)
+		}
+	case *types.Const, // Only package-level constants have a path.
+		*types.Label,   // Labels are function-local.
+		*types.PkgName: // PkgNames are file-local.
+		return "", fmt.Errorf("no path for %v", obj)
+
+	case *types.Var:
+		// Could be:
+		// - a field (obj.IsField())
+		// - a func parameter or result
+		// - a local var.
+		// Sadly there is no way to distinguish
+		// a param/result from a local
+		// so we must proceed to the find.
+
+	case *types.Func:
+		// A func, if not package-level, must be a method.
+		if recv := obj.Type().(*types.Signature).Recv(); recv == nil {
+			return "", fmt.Errorf("func is not a method: %v", obj)
+		}
+
+		if path, ok := enc.concreteMethod(obj); ok {
+			// Fast path for concrete methods that avoids looping over scope.
+			return path, nil
+		}
+
+	default:
+		panic(obj)
+	}
+
+	// 4. Search the API for the path to the var (field/param/result) or method.
+
+	// First inspect package-level named types.
+	// In the presence of path aliases, these give
+	// the best paths because non-types may
+	// refer to types, but not the reverse.
+	empty := make([]byte, 0, 48) // initial space
+	objs := enc.scopeObjects(scope)
+	for _, o := range objs {
+		tname, ok := o.(*types.TypeName)
+		if !ok {
+			continue // handle non-types in second pass
+		}
+
+		path := append(empty, o.Name()...)
+		path = append(path, opType)
+
+		T := o.Type()
+		if alias, ok := T.(*aliases.Alias); ok {
+			if r := findTypeParam(obj, aliases.TypeParams(alias), path, opTypeParam, nil); r != nil {
+				return Path(r), nil
+			}
+			if r := find(obj, aliases.Rhs(alias), append(path, opRhs), nil); r != nil {
+				return Path(r), nil
+			}
+
+		} else if tname.IsAlias() {
+			// legacy alias
+			if r := find(obj, T, path, nil); r != nil {
+				return Path(r), nil
+			}
+
+		} else if named, ok := T.(*types.Named); ok {
+			// defined (named) type
+			if r := findTypeParam(obj, named.TypeParams(), path, opTypeParam, nil); r != nil {
+				return Path(r), nil
+			}
+			if r := find(obj, named.Underlying(), append(path, opUnderlying), nil); r != nil {
+				return Path(r), nil
+			}
+		}
+	}
+
+	// Then inspect everything else:
+	// non-types, and declared methods of defined types.
+	for _, o := range objs {
+		path := append(empty, o.Name()...)
+		if _, ok := o.(*types.TypeName); !ok {
+			if o.Exported() {
+				// exported non-type (const, var, func)
+				if r := find(obj, o.Type(), append(path, opType), nil); r != nil {
+					return Path(r), nil
+				}
+			}
+			continue
+		}
+
+		// Inspect declared methods of defined types.
+		if T, ok := aliases.Unalias(o.Type()).(*types.Named); ok {
+			path = append(path, opType)
+			// The method index here is always with respect
+			// to the underlying go/types data structures,
+			// which ultimately derives from source order
+			// and must be preserved by export data.
+			for i := 0; i < T.NumMethods(); i++ {
+				m := T.Method(i)
+				path2 := appendOpArg(path, opMethod, i)
+				if m == obj {
+					return Path(path2), nil // found declared method
+				}
+				if r := find(obj, m.Type(), append(path2, opType), nil); r != nil {
+					return Path(r), nil
+				}
+			}
+		}
+	}
+
+	return "", fmt.Errorf("can't find path for %v in %s", obj, pkg.Path())
+}
+
+func appendOpArg(path []byte, op byte, arg int) []byte {
+	path = append(path, op)
+	path = strconv.AppendInt(path, int64(arg), 10)
+	return path
+}
+
+// concreteMethod returns the path for meth, which must have a non-nil receiver.
+// The second return value indicates success and may be false if the method is
+// an interface method or if it is an instantiated method.
+//
+// This function is just an optimization that avoids the general scope walking
+// approach. You are expected to fall back to the general approach if this
+// function fails.
+func (enc *Encoder) concreteMethod(meth *types.Func) (Path, bool) {
+	// Concrete methods can only be declared on package-scoped named types. For
+	// that reason we can skip the expensive walk over the package scope: the
+	// path will always be package -> named type -> method. We can trivially get
+	// the type name from the receiver, and only have to look over the type's
+	// methods to find the method index.
+	//
+	// Methods on generic types require special consideration, however. Consider
+	// the following package:
+	//
+	// 	L1: type S[T any] struct{}
+	// 	L2: func (recv S[A]) Foo() { recv.Bar() }
+	// 	L3: func (recv S[B]) Bar() { }
+	// 	L4: type Alias = S[int]
+	// 	L5: func _[T any]() { var s S[int]; s.Foo() }
+	//
+	// The receivers of methods on generic types are instantiations. L2 and L3
+	// instantiate S with the type-parameters A and B, which are scoped to the
+	// respective methods. L4 and L5 each instantiate S with int. Each of these
+	// instantiations has its own method set, full of methods (and thus objects)
+	// with receivers whose types are the respective instantiations. In other
+	// words, we have
+	//
+	// S[A].Foo, S[A].Bar
+	// S[B].Foo, S[B].Bar
+	// S[int].Foo, S[int].Bar
+	//
+	// We may thus be trying to produce object paths for any of these objects.
+	//
+	// S[A].Foo and S[B].Bar are the origin methods, and their paths are S.Foo
+	// and S.Bar, which are the paths that this function naturally produces.
+	//
+	// S[A].Bar, S[B].Foo, and both methods on S[int] are instantiations that
+	// don't correspond to the origin methods. For S[int], this is significant.
+	// The most precise object path for S[int].Foo, for example, is Alias.Foo,
+	// not S.Foo. Our function, however, would produce S.Foo, which would
+	// resolve to a different object.
+	//
+	// For S[A].Bar and S[B].Foo it could be argued that S.Bar and S.Foo are
+	// still the correct paths, since only the origin methods have meaningful
+	// paths. But this is likely only true for trivial cases and has edge cases.
+	// Since this function is only an optimization, we err on the side of giving
+	// up, deferring to the slower but definitely correct algorithm. Most users
+	// of objectpath will only be giving us origin methods, anyway, as referring
+	// to instantiated methods is usually not useful.
+
+	if meth.Origin() != meth {
+		return "", false
+	}
+
+	_, named := typesinternal.ReceiverNamed(meth.Type().(*types.Signature).Recv())
+	if named == nil {
+		return "", false
+	}
+
+	if types.IsInterface(named) {
+		// Named interfaces don't have to be package-scoped
+		//
+		// TODO(dominikh): opt: if scope.Lookup(name) == named, then we can apply this optimization to interface
+		// methods, too, I think.
+		return "", false
+	}
+
+	// Preallocate space for the name, opType, opMethod, and some digits.
+	name := named.Obj().Name()
+	path := make([]byte, 0, len(name)+8)
+	path = append(path, name...)
+	path = append(path, opType)
+
+	// Method indices are w.r.t. the go/types data structures,
+	// ultimately deriving from source order,
+	// which is preserved by export data.
+	for i := 0; i < named.NumMethods(); i++ {
+		if named.Method(i) == meth {
+			path = appendOpArg(path, opMethod, i)
+			return Path(path), true
+		}
+	}
+
+	// Due to golang/go#59944, go/types fails to associate the receiver with
+	// certain methods on cgo types.
+	//
+	// TODO(rfindley): replace this panic once golang/go#59944 is fixed in all Go
+	// versions gopls supports.
+	return "", false
+	// panic(fmt.Sprintf("couldn't find method %s on type %s; methods: %#v", meth, named, enc.namedMethods(named)))
+}
+
+// find finds obj within type T, returning the path to it, or nil if not found.
+//
+// The seen map is used to short circuit cycles through type parameters. If
+// nil, it will be allocated as necessary.
+func find(obj types.Object, T types.Type, path []byte, seen map[*types.TypeName]bool) []byte {
+	switch T := T.(type) {
+	case *aliases.Alias:
+		return find(obj, aliases.Unalias(T), path, seen)
+	case *types.Basic, *types.Named:
+		// Named types belonging to pkg were handled already,
+		// so T must belong to another package. No path.
+		return nil
+	case *types.Pointer:
+		return find(obj, T.Elem(), append(path, opElem), seen)
+	case *types.Slice:
+		return find(obj, T.Elem(), append(path, opElem), seen)
+	case *types.Array:
+		return find(obj, T.Elem(), append(path, opElem), seen)
+	case *types.Chan:
+		return find(obj, T.Elem(), append(path, opElem), seen)
+	case *types.Map:
+		if r := find(obj, T.Key(), append(path, opKey), seen); r != nil {
+			return r
+		}
+		return find(obj, T.Elem(), append(path, opElem), seen)
+	case *types.Signature:
+		if r := findTypeParam(obj, T.RecvTypeParams(), path, opRecvTypeParam, nil); r != nil {
+			return r
+		}
+		if r := findTypeParam(obj, T.TypeParams(), path, opTypeParam, seen); r != nil {
+			return r
+		}
+		if r := find(obj, T.Params(), append(path, opParams), seen); r != nil {
+			return r
+		}
+		return find(obj, T.Results(), append(path, opResults), seen)
+	case *types.Struct:
+		for i := 0; i < T.NumFields(); i++ {
+			fld := T.Field(i)
+			path2 := appendOpArg(path, opField, i)
+			if fld == obj {
+				return path2 // found field var
+			}
+			if r := find(obj, fld.Type(), append(path2, opType), seen); r != nil {
+				return r
+			}
+		}
+		return nil
+	case *types.Tuple:
+		for i := 0; i < T.Len(); i++ {
+			v := T.At(i)
+			path2 := appendOpArg(path, opAt, i)
+			if v == obj {
+				return path2 // found param/result var
+			}
+			if r := find(obj, v.Type(), append(path2, opType), seen); r != nil {
+				return r
+			}
+		}
+		return nil
+	case *types.Interface:
+		for i := 0; i < T.NumMethods(); i++ {
+			m := T.Method(i)
+			path2 := appendOpArg(path, opMethod, i)
+			if m == obj {
+				return path2 // found interface method
+			}
+			if r := find(obj, m.Type(), append(path2, opType), seen); r != nil {
+				return r
+			}
+		}
+		return nil
+	case *types.TypeParam:
+		name := T.Obj()
+		if name == obj {
+			return append(path, opObj)
+		}
+		if seen[name] {
+			return nil
+		}
+		if seen == nil {
+			seen = make(map[*types.TypeName]bool)
+		}
+		seen[name] = true
+		if r := find(obj, T.Constraint(), append(path, opConstraint), seen); r != nil {
+			return r
+		}
+		return nil
+	}
+	panic(T)
+}
+
+func findTypeParam(obj types.Object, list *types.TypeParamList, path []byte, op byte, seen map[*types.TypeName]bool) []byte {
+	for i := 0; i < list.Len(); i++ {
+		tparam := list.At(i)
+		path2 := appendOpArg(path, op, i)
+		if r := find(obj, tparam, path2, seen); r != nil {
+			return r
+		}
+	}
+	return nil
+}
+
+// Object returns the object denoted by path p within the package pkg.
+func Object(pkg *types.Package, p Path) (types.Object, error) {
+	pathstr := string(p)
+	if pathstr == "" {
+		return nil, fmt.Errorf("empty path")
+	}
+
+	var pkgobj, suffix string
+	if dot := strings.IndexByte(pathstr, opType); dot < 0 {
+		pkgobj = pathstr
+	} else {
+		pkgobj = pathstr[:dot]
+		suffix = pathstr[dot:] // suffix starts with "."
+	}
+
+	obj := pkg.Scope().Lookup(pkgobj)
+	if obj == nil {
+		return nil, fmt.Errorf("package %s does not contain %q", pkg.Path(), pkgobj)
+	}
+
+	// abstraction of *types.{Pointer,Slice,Array,Chan,Map}
+	type hasElem interface {
+		Elem() types.Type
+	}
+	// abstraction of *types.{Named,Signature}
+	type hasTypeParams interface {
+		TypeParams() *types.TypeParamList
+	}
+	// abstraction of *types.{Named,TypeParam}
+	type hasObj interface {
+		Obj() *types.TypeName
+	}
+
+	// The loop state is the pair (t, obj),
+	// exactly one of which is non-nil, initially obj.
+	// All suffixes start with '.' (the only object->type operation),
+	// followed by optional type->type operations,
+	// then a type->object operation.
+	// The cycle then repeats.
+	var t types.Type
+	for suffix != "" {
+		code := suffix[0]
+		suffix = suffix[1:]
+
+		// Codes [AFMTr] have an integer operand.
+		var index int
+		switch code {
+		case opAt, opField, opMethod, opTypeParam, opRecvTypeParam:
+			rest := strings.TrimLeft(suffix, "0123456789")
+			numerals := suffix[:len(suffix)-len(rest)]
+			suffix = rest
+			i, err := strconv.Atoi(numerals)
+			if err != nil {
+				return nil, fmt.Errorf("invalid path: bad numeric operand %q for code %q", numerals, code)
+			}
+			index = int(i)
+		case opObj:
+			// no operand
+		default:
+			// The suffix must end with a type->object operation.
+			if suffix == "" {
+				return nil, fmt.Errorf("invalid path: ends with %q, want [AFMO]", code)
+			}
+		}
+
+		if code == opType {
+			if t != nil {
+				return nil, fmt.Errorf("invalid path: unexpected %q in type context", opType)
+			}
+			t = obj.Type()
+			obj = nil
+			continue
+		}
+
+		if t == nil {
+			return nil, fmt.Errorf("invalid path: code %q in object context", code)
+		}
+
+		// Inv: t != nil, obj == nil
+
+		t = aliases.Unalias(t)
+		switch code {
+		case opElem:
+			hasElem, ok := t.(hasElem) // Pointer, Slice, Array, Chan, Map
+			if !ok {
+				return nil, fmt.Errorf("cannot apply %q to %s (got %T, want pointer, slice, array, chan or map)", code, t, t)
+			}
+			t = hasElem.Elem()
+
+		case opKey:
+			mapType, ok := t.(*types.Map)
+			if !ok {
+				return nil, fmt.Errorf("cannot apply %q to %s (got %T, want map)", code, t, t)
+			}
+			t = mapType.Key()
+
+		case opParams:
+			sig, ok := t.(*types.Signature)
+			if !ok {
+				return nil, fmt.Errorf("cannot apply %q to %s (got %T, want signature)", code, t, t)
+			}
+			t = sig.Params()
+
+		case opResults:
+			sig, ok := t.(*types.Signature)
+			if !ok {
+				return nil, fmt.Errorf("cannot apply %q to %s (got %T, want signature)", code, t, t)
+			}
+			t = sig.Results()
+
+		case opUnderlying:
+			named, ok := t.(*types.Named)
+			if !ok {
+				return nil, fmt.Errorf("cannot apply %q to %s (got %T, want named)", code, t, t)
+			}
+			t = named.Underlying()
+
+		case opRhs:
+			if alias, ok := t.(*aliases.Alias); ok {
+				t = aliases.Rhs(alias)
+			} else if false && aliases.Enabled() {
+				// The Enabled check is too expensive, so for now we
+				// simply assume that aliases are not enabled.
+				// TODO(adonovan): replace with "if true {" when go1.24 is assured.
+				return nil, fmt.Errorf("cannot apply %q to %s (got %T, want alias)", code, t, t)
+			}
+
+		case opTypeParam:
+			hasTypeParams, ok := t.(hasTypeParams) // Named, Signature
+			if !ok {
+				return nil, fmt.Errorf("cannot apply %q to %s (got %T, want named or signature)", code, t, t)
+			}
+			tparams := hasTypeParams.TypeParams()
+			if n := tparams.Len(); index >= n {
+				return nil, fmt.Errorf("tuple index %d out of range [0-%d)", index, n)
+			}
+			t = tparams.At(index)
+
+		case opRecvTypeParam:
+			sig, ok := t.(*types.Signature) // Signature
+			if !ok {
+				return nil, fmt.Errorf("cannot apply %q to %s (got %T, want signature)", code, t, t)
+			}
+			rtparams := sig.RecvTypeParams()
+			if n := rtparams.Len(); index >= n {
+				return nil, fmt.Errorf("tuple index %d out of range [0-%d)", index, n)
+			}
+			t = rtparams.At(index)
+
+		case opConstraint:
+			tparam, ok := t.(*types.TypeParam)
+			if !ok {
+				return nil, fmt.Errorf("cannot apply %q to %s (got %T, want type parameter)", code, t, t)
+			}
+			t = tparam.Constraint()
+
+		case opAt:
+			tuple, ok := t.(*types.Tuple)
+			if !ok {
+				return nil, fmt.Errorf("cannot apply %q to %s (got %T, want tuple)", code, t, t)
+			}
+			if n := tuple.Len(); index >= n {
+				return nil, fmt.Errorf("tuple index %d out of range [0-%d)", index, n)
+			}
+			obj = tuple.At(index)
+			t = nil
+
+		case opField:
+			structType, ok := t.(*types.Struct)
+			if !ok {
+				return nil, fmt.Errorf("cannot apply %q to %s (got %T, want struct)", code, t, t)
+			}
+			if n := structType.NumFields(); index >= n {
+				return nil, fmt.Errorf("field index %d out of range [0-%d)", index, n)
+			}
+			obj = structType.Field(index)
+			t = nil
+
+		case opMethod:
+			switch t := t.(type) {
+			case *types.Interface:
+				if index >= t.NumMethods() {
+					return nil, fmt.Errorf("method index %d out of range [0-%d)", index, t.NumMethods())
+				}
+				obj = t.Method(index) // Id-ordered
+
+			case *types.Named:
+				if index >= t.NumMethods() {
+					return nil, fmt.Errorf("method index %d out of range [0-%d)", index, t.NumMethods())
+				}
+				obj = t.Method(index)
+
+			default:
+				return nil, fmt.Errorf("cannot apply %q to %s (got %T, want interface or named)", code, t, t)
+			}
+			t = nil
+
+		case opObj:
+			hasObj, ok := t.(hasObj)
+			if !ok {
+				return nil, fmt.Errorf("cannot apply %q to %s (got %T, want named or type param)", code, t, t)
+			}
+			obj = hasObj.Obj()
+			t = nil
+
+		default:
+			return nil, fmt.Errorf("invalid path: unknown code %q", code)
+		}
+	}
+
+	if obj == nil {
+		panic(p) // path does not end in an object-valued operator
+	}
+
+	if obj.Pkg() != pkg {
+		return nil, fmt.Errorf("path denotes %s, which belongs to a different package", obj)
+	}
+
+	return obj, nil // success
+}
+
+// scopeObjects is a memoization of scope objects.
+// Callers must not modify the result.
+func (enc *Encoder) scopeObjects(scope *types.Scope) []types.Object {
+	m := enc.scopeMemo
+	if m == nil {
+		m = make(map[*types.Scope][]types.Object)
+		enc.scopeMemo = m
+	}
+	objs, ok := m[scope]
+	if !ok {
+		names := scope.Names() // allocates and sorts
+		objs = make([]types.Object, len(names))
+		for i, name := range names {
+			objs[i] = scope.Lookup(name)
+		}
+		m[scope] = objs
+	}
+	return objs
+}
diff --git a/vendor/golang.org/x/tools/go/types/typeutil/callee.go b/vendor/golang.org/x/tools/go/types/typeutil/callee.go
new file mode 100644
index 0000000..90dc541
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/types/typeutil/callee.go
@@ -0,0 +1,69 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package typeutil
+
+import (
+	"go/ast"
+	"go/types"
+
+	"golang.org/x/tools/go/ast/astutil"
+	"golang.org/x/tools/internal/typeparams"
+)
+
+// Callee returns the named target of a function call, if any:
+// a function, method, builtin, or variable.
+//
+// Functions and methods may potentially have type parameters.
+func Callee(info *types.Info, call *ast.CallExpr) types.Object {
+	fun := astutil.Unparen(call.Fun)
+
+	// Look through type instantiation if necessary.
+	isInstance := false
+	switch fun.(type) {
+	case *ast.IndexExpr, *ast.IndexListExpr:
+		// When extracting the callee from an *IndexExpr, we need to check that
+		// it is a *types.Func and not a *types.Var.
+		// Example: Don't match a slice m within the expression `m[0]()`.
+		isInstance = true
+		fun, _, _, _ = typeparams.UnpackIndexExpr(fun)
+	}
+
+	var obj types.Object
+	switch fun := fun.(type) {
+	case *ast.Ident:
+		obj = info.Uses[fun] // type, var, builtin, or declared func
+	case *ast.SelectorExpr:
+		if sel, ok := info.Selections[fun]; ok {
+			obj = sel.Obj() // method or field
+		} else {
+			obj = info.Uses[fun.Sel] // qualified identifier?
+		}
+	}
+	if _, ok := obj.(*types.TypeName); ok {
+		return nil // T(x) is a conversion, not a call
+	}
+	// A Func is required to match instantiations.
+	if _, ok := obj.(*types.Func); isInstance && !ok {
+		return nil // Was not a Func.
+	}
+	return obj
+}
+
+// StaticCallee returns the target (function or method) of a static function
+// call, if any. It returns nil for calls to builtins.
+//
+// Note: for calls of instantiated functions and methods, StaticCallee returns
+// the corresponding generic function or method on the generic type.
+func StaticCallee(info *types.Info, call *ast.CallExpr) *types.Func {
+	if f, ok := Callee(info, call).(*types.Func); ok && !interfaceMethod(f) {
+		return f
+	}
+	return nil
+}
+
+func interfaceMethod(f *types.Func) bool {
+	recv := f.Type().(*types.Signature).Recv()
+	return recv != nil && types.IsInterface(recv.Type())
+}
diff --git a/vendor/golang.org/x/tools/go/types/typeutil/imports.go b/vendor/golang.org/x/tools/go/types/typeutil/imports.go
new file mode 100644
index 0000000..b81ce0c
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/types/typeutil/imports.go
@@ -0,0 +1,30 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package typeutil
+
+import "go/types"
+
+// Dependencies returns all dependencies of the specified packages.
+//
+// Dependent packages appear in topological order: if package P imports
+// package Q, Q appears earlier than P in the result.
+// The algorithm follows import statements in the order they
+// appear in the source code, so the result is a total order.
+func Dependencies(pkgs ...*types.Package) []*types.Package {
+	var result []*types.Package
+	seen := make(map[*types.Package]bool)
+	var visit func(pkgs []*types.Package)
+	visit = func(pkgs []*types.Package) {
+		for _, p := range pkgs {
+			if !seen[p] {
+				seen[p] = true
+				visit(p.Imports())
+				result = append(result, p)
+			}
+		}
+	}
+	visit(pkgs)
+	return result
+}
diff --git a/vendor/golang.org/x/tools/go/types/typeutil/map.go b/vendor/golang.org/x/tools/go/types/typeutil/map.go
new file mode 100644
index 0000000..a92f80d
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/types/typeutil/map.go
@@ -0,0 +1,518 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package typeutil defines various utilities for types, such as Map,
+// a mapping from types.Type to any values.
+package typeutil // import "golang.org/x/tools/go/types/typeutil"
+
+import (
+	"bytes"
+	"fmt"
+	"go/types"
+	"reflect"
+
+	"golang.org/x/tools/internal/aliases"
+	"golang.org/x/tools/internal/typeparams"
+)
+
+// Map is a hash-table-based mapping from types (types.Type) to
+// arbitrary any values.  The concrete types that implement
+// the Type interface are pointers.  Since they are not canonicalized,
+// == cannot be used to check for equivalence, and thus we cannot
+// simply use a Go map.
+//
+// Just as with map[K]V, a nil *Map is a valid empty map.
+//
+// Not thread-safe.
+type Map struct {
+	hasher Hasher             // shared by many Maps
+	table  map[uint32][]entry // maps hash to bucket; entry.key==nil means unused
+	length int                // number of map entries
+}
+
+// entry is an entry (key/value association) in a hash bucket.
+type entry struct {
+	key   types.Type
+	value any
+}
+
+// SetHasher sets the hasher used by Map.
+//
+// All Hashers are functionally equivalent but contain internal state
+// used to cache the results of hashing previously seen types.
+//
+// A single Hasher created by MakeHasher() may be shared among many
+// Maps.  This is recommended if the instances have many keys in
+// common, as it will amortize the cost of hash computation.
+//
+// A Hasher may grow without bound as new types are seen.  Even when a
+// type is deleted from the map, the Hasher never shrinks, since other
+// types in the map may reference the deleted type indirectly.
+//
+// Hashers are not thread-safe, and read-only operations such as
+// Map.Lookup require updates to the hasher, so a full Mutex lock (not a
+// read-lock) is require around all Map operations if a shared
+// hasher is accessed from multiple threads.
+//
+// If SetHasher is not called, the Map will create a private hasher at
+// the first call to Insert.
+func (m *Map) SetHasher(hasher Hasher) {
+	m.hasher = hasher
+}
+
+// Delete removes the entry with the given key, if any.
+// It returns true if the entry was found.
+func (m *Map) Delete(key types.Type) bool {
+	if m != nil && m.table != nil {
+		hash := m.hasher.Hash(key)
+		bucket := m.table[hash]
+		for i, e := range bucket {
+			if e.key != nil && types.Identical(key, e.key) {
+				// We can't compact the bucket as it
+				// would disturb iterators.
+				bucket[i] = entry{}
+				m.length--
+				return true
+			}
+		}
+	}
+	return false
+}
+
+// At returns the map entry for the given key.
+// The result is nil if the entry is not present.
+func (m *Map) At(key types.Type) any {
+	if m != nil && m.table != nil {
+		for _, e := range m.table[m.hasher.Hash(key)] {
+			if e.key != nil && types.Identical(key, e.key) {
+				return e.value
+			}
+		}
+	}
+	return nil
+}
+
+// Set sets the map entry for key to val,
+// and returns the previous entry, if any.
+func (m *Map) Set(key types.Type, value any) (prev any) {
+	if m.table != nil {
+		hash := m.hasher.Hash(key)
+		bucket := m.table[hash]
+		var hole *entry
+		for i, e := range bucket {
+			if e.key == nil {
+				hole = &bucket[i]
+			} else if types.Identical(key, e.key) {
+				prev = e.value
+				bucket[i].value = value
+				return
+			}
+		}
+
+		if hole != nil {
+			*hole = entry{key, value} // overwrite deleted entry
+		} else {
+			m.table[hash] = append(bucket, entry{key, value})
+		}
+	} else {
+		if m.hasher.memo == nil {
+			m.hasher = MakeHasher()
+		}
+		hash := m.hasher.Hash(key)
+		m.table = map[uint32][]entry{hash: {entry{key, value}}}
+	}
+
+	m.length++
+	return
+}
+
+// Len returns the number of map entries.
+func (m *Map) Len() int {
+	if m != nil {
+		return m.length
+	}
+	return 0
+}
+
+// Iterate calls function f on each entry in the map in unspecified order.
+//
+// If f should mutate the map, Iterate provides the same guarantees as
+// Go maps: if f deletes a map entry that Iterate has not yet reached,
+// f will not be invoked for it, but if f inserts a map entry that
+// Iterate has not yet reached, whether or not f will be invoked for
+// it is unspecified.
+func (m *Map) Iterate(f func(key types.Type, value any)) {
+	if m != nil {
+		for _, bucket := range m.table {
+			for _, e := range bucket {
+				if e.key != nil {
+					f(e.key, e.value)
+				}
+			}
+		}
+	}
+}
+
+// Keys returns a new slice containing the set of map keys.
+// The order is unspecified.
+func (m *Map) Keys() []types.Type {
+	keys := make([]types.Type, 0, m.Len())
+	m.Iterate(func(key types.Type, _ any) {
+		keys = append(keys, key)
+	})
+	return keys
+}
+
+func (m *Map) toString(values bool) string {
+	if m == nil {
+		return "{}"
+	}
+	var buf bytes.Buffer
+	fmt.Fprint(&buf, "{")
+	sep := ""
+	m.Iterate(func(key types.Type, value any) {
+		fmt.Fprint(&buf, sep)
+		sep = ", "
+		fmt.Fprint(&buf, key)
+		if values {
+			fmt.Fprintf(&buf, ": %q", value)
+		}
+	})
+	fmt.Fprint(&buf, "}")
+	return buf.String()
+}
+
+// String returns a string representation of the map's entries.
+// Values are printed using fmt.Sprintf("%v", v).
+// Order is unspecified.
+func (m *Map) String() string {
+	return m.toString(true)
+}
+
+// KeysString returns a string representation of the map's key set.
+// Order is unspecified.
+func (m *Map) KeysString() string {
+	return m.toString(false)
+}
+
+////////////////////////////////////////////////////////////////////////
+// Hasher
+
+// A Hasher maps each type to its hash value.
+// For efficiency, a hasher uses memoization; thus its memory
+// footprint grows monotonically over time.
+// Hashers are not thread-safe.
+// Hashers have reference semantics.
+// Call MakeHasher to create a Hasher.
+type Hasher struct {
+	memo map[types.Type]uint32
+
+	// ptrMap records pointer identity.
+	ptrMap map[any]uint32
+
+	// sigTParams holds type parameters from the signature being hashed.
+	// Signatures are considered identical modulo renaming of type parameters, so
+	// within the scope of a signature type the identity of the signature's type
+	// parameters is just their index.
+	//
+	// Since the language does not currently support referring to uninstantiated
+	// generic types or functions, and instantiated signatures do not have type
+	// parameter lists, we should never encounter a second non-empty type
+	// parameter list when hashing a generic signature.
+	sigTParams *types.TypeParamList
+}
+
+// MakeHasher returns a new Hasher instance.
+func MakeHasher() Hasher {
+	return Hasher{
+		memo:       make(map[types.Type]uint32),
+		ptrMap:     make(map[any]uint32),
+		sigTParams: nil,
+	}
+}
+
+// Hash computes a hash value for the given type t such that
+// Identical(t, t') => Hash(t) == Hash(t').
+func (h Hasher) Hash(t types.Type) uint32 {
+	hash, ok := h.memo[t]
+	if !ok {
+		hash = h.hashFor(t)
+		h.memo[t] = hash
+	}
+	return hash
+}
+
+// hashString computes the Fowler–Noll–Vo hash of s.
+func hashString(s string) uint32 {
+	var h uint32
+	for i := 0; i < len(s); i++ {
+		h ^= uint32(s[i])
+		h *= 16777619
+	}
+	return h
+}
+
+// hashFor computes the hash of t.
+func (h Hasher) hashFor(t types.Type) uint32 {
+	// See Identical for rationale.
+	switch t := t.(type) {
+	case *types.Basic:
+		return uint32(t.Kind())
+
+	case *aliases.Alias:
+		return h.Hash(aliases.Unalias(t))
+
+	case *types.Array:
+		return 9043 + 2*uint32(t.Len()) + 3*h.Hash(t.Elem())
+
+	case *types.Slice:
+		return 9049 + 2*h.Hash(t.Elem())
+
+	case *types.Struct:
+		var hash uint32 = 9059
+		for i, n := 0, t.NumFields(); i < n; i++ {
+			f := t.Field(i)
+			if f.Anonymous() {
+				hash += 8861
+			}
+			hash += hashString(t.Tag(i))
+			hash += hashString(f.Name()) // (ignore f.Pkg)
+			hash += h.Hash(f.Type())
+		}
+		return hash
+
+	case *types.Pointer:
+		return 9067 + 2*h.Hash(t.Elem())
+
+	case *types.Signature:
+		var hash uint32 = 9091
+		if t.Variadic() {
+			hash *= 8863
+		}
+
+		// Use a separate hasher for types inside of the signature, where type
+		// parameter identity is modified to be (index, constraint). We must use a
+		// new memo for this hasher as type identity may be affected by this
+		// masking. For example, in func[T any](*T), the identity of *T depends on
+		// whether we are mapping the argument in isolation, or recursively as part
+		// of hashing the signature.
+		//
+		// We should never encounter a generic signature while hashing another
+		// generic signature, but defensively set sigTParams only if h.mask is
+		// unset.
+		tparams := t.TypeParams()
+		if h.sigTParams == nil && tparams.Len() != 0 {
+			h = Hasher{
+				// There may be something more efficient than discarding the existing
+				// memo, but it would require detecting whether types are 'tainted' by
+				// references to type parameters.
+				memo: make(map[types.Type]uint32),
+				// Re-using ptrMap ensures that pointer identity is preserved in this
+				// hasher.
+				ptrMap:     h.ptrMap,
+				sigTParams: tparams,
+			}
+		}
+
+		for i := 0; i < tparams.Len(); i++ {
+			tparam := tparams.At(i)
+			hash += 7 * h.Hash(tparam.Constraint())
+		}
+
+		return hash + 3*h.hashTuple(t.Params()) + 5*h.hashTuple(t.Results())
+
+	case *types.Union:
+		return h.hashUnion(t)
+
+	case *types.Interface:
+		// Interfaces are identical if they have the same set of methods, with
+		// identical names and types, and they have the same set of type
+		// restrictions. See go/types.identical for more details.
+		var hash uint32 = 9103
+
+		// Hash methods.
+		for i, n := 0, t.NumMethods(); i < n; i++ {
+			// Method order is not significant.
+			// Ignore m.Pkg().
+			m := t.Method(i)
+			// Use shallow hash on method signature to
+			// avoid anonymous interface cycles.
+			hash += 3*hashString(m.Name()) + 5*h.shallowHash(m.Type())
+		}
+
+		// Hash type restrictions.
+		terms, err := typeparams.InterfaceTermSet(t)
+		// if err != nil t has invalid type restrictions.
+		if err == nil {
+			hash += h.hashTermSet(terms)
+		}
+
+		return hash
+
+	case *types.Map:
+		return 9109 + 2*h.Hash(t.Key()) + 3*h.Hash(t.Elem())
+
+	case *types.Chan:
+		return 9127 + 2*uint32(t.Dir()) + 3*h.Hash(t.Elem())
+
+	case *types.Named:
+		hash := h.hashPtr(t.Obj())
+		targs := t.TypeArgs()
+		for i := 0; i < targs.Len(); i++ {
+			targ := targs.At(i)
+			hash += 2 * h.Hash(targ)
+		}
+		return hash
+
+	case *types.TypeParam:
+		return h.hashTypeParam(t)
+
+	case *types.Tuple:
+		return h.hashTuple(t)
+	}
+
+	panic(fmt.Sprintf("%T: %v", t, t))
+}
+
+func (h Hasher) hashTuple(tuple *types.Tuple) uint32 {
+	// See go/types.identicalTypes for rationale.
+	n := tuple.Len()
+	hash := 9137 + 2*uint32(n)
+	for i := 0; i < n; i++ {
+		hash += 3 * h.Hash(tuple.At(i).Type())
+	}
+	return hash
+}
+
+func (h Hasher) hashUnion(t *types.Union) uint32 {
+	// Hash type restrictions.
+	terms, err := typeparams.UnionTermSet(t)
+	// if err != nil t has invalid type restrictions. Fall back on a non-zero
+	// hash.
+	if err != nil {
+		return 9151
+	}
+	return h.hashTermSet(terms)
+}
+
+func (h Hasher) hashTermSet(terms []*types.Term) uint32 {
+	hash := 9157 + 2*uint32(len(terms))
+	for _, term := range terms {
+		// term order is not significant.
+		termHash := h.Hash(term.Type())
+		if term.Tilde() {
+			termHash *= 9161
+		}
+		hash += 3 * termHash
+	}
+	return hash
+}
+
+// hashTypeParam returns a hash of the type parameter t, with a hash value
+// depending on whether t is contained in h.sigTParams.
+//
+// If h.sigTParams is set and contains t, then we are in the process of hashing
+// a signature, and the hash value of t must depend only on t's index and
+// constraint: signatures are considered identical modulo type parameter
+// renaming. To avoid infinite recursion, we only hash the type parameter
+// index, and rely on types.Identical to handle signatures where constraints
+// are not identical.
+//
+// Otherwise the hash of t depends only on t's pointer identity.
+func (h Hasher) hashTypeParam(t *types.TypeParam) uint32 {
+	if h.sigTParams != nil {
+		i := t.Index()
+		if i >= 0 && i < h.sigTParams.Len() && t == h.sigTParams.At(i) {
+			return 9173 + 3*uint32(i)
+		}
+	}
+	return h.hashPtr(t.Obj())
+}
+
+// hashPtr hashes the pointer identity of ptr. It uses h.ptrMap to ensure that
+// pointers values are not dependent on the GC.
+func (h Hasher) hashPtr(ptr any) uint32 {
+	if hash, ok := h.ptrMap[ptr]; ok {
+		return hash
+	}
+	hash := uint32(reflect.ValueOf(ptr).Pointer())
+	h.ptrMap[ptr] = hash
+	return hash
+}
+
+// shallowHash computes a hash of t without looking at any of its
+// element Types, to avoid potential anonymous cycles in the types of
+// interface methods.
+//
+// When an unnamed non-empty interface type appears anywhere among the
+// arguments or results of an interface method, there is a potential
+// for endless recursion. Consider:
+//
+//	type X interface { m() []*interface { X } }
+//
+// The problem is that the Methods of the interface in m's result type
+// include m itself; there is no mention of the named type X that
+// might help us break the cycle.
+// (See comment in go/types.identical, case *Interface, for more.)
+func (h Hasher) shallowHash(t types.Type) uint32 {
+	// t is the type of an interface method (Signature),
+	// its params or results (Tuples), or their immediate
+	// elements (mostly Slice, Pointer, Basic, Named),
+	// so there's no need to optimize anything else.
+	switch t := t.(type) {
+	case *aliases.Alias:
+		return h.shallowHash(aliases.Unalias(t))
+
+	case *types.Signature:
+		var hash uint32 = 604171
+		if t.Variadic() {
+			hash *= 971767
+		}
+		// The Signature/Tuple recursion is always finite
+		// and invariably shallow.
+		return hash + 1062599*h.shallowHash(t.Params()) + 1282529*h.shallowHash(t.Results())
+
+	case *types.Tuple:
+		n := t.Len()
+		hash := 9137 + 2*uint32(n)
+		for i := 0; i < n; i++ {
+			hash += 53471161 * h.shallowHash(t.At(i).Type())
+		}
+		return hash
+
+	case *types.Basic:
+		return 45212177 * uint32(t.Kind())
+
+	case *types.Array:
+		return 1524181 + 2*uint32(t.Len())
+
+	case *types.Slice:
+		return 2690201
+
+	case *types.Struct:
+		return 3326489
+
+	case *types.Pointer:
+		return 4393139
+
+	case *types.Union:
+		return 562448657
+
+	case *types.Interface:
+		return 2124679 // no recursion here
+
+	case *types.Map:
+		return 9109
+
+	case *types.Chan:
+		return 9127
+
+	case *types.Named:
+		return h.hashPtr(t.Obj())
+
+	case *types.TypeParam:
+		return h.hashPtr(t.Obj())
+	}
+	panic(fmt.Sprintf("shallowHash: %T: %v", t, t))
+}
diff --git a/vendor/golang.org/x/tools/go/types/typeutil/methodsetcache.go b/vendor/golang.org/x/tools/go/types/typeutil/methodsetcache.go
new file mode 100644
index 0000000..bd71aaf
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/types/typeutil/methodsetcache.go
@@ -0,0 +1,73 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements a cache of method sets.
+
+package typeutil
+
+import (
+	"go/types"
+	"sync"
+
+	"golang.org/x/tools/internal/aliases"
+)
+
+// A MethodSetCache records the method set of each type T for which
+// MethodSet(T) is called so that repeat queries are fast.
+// The zero value is a ready-to-use cache instance.
+type MethodSetCache struct {
+	mu     sync.Mutex
+	named  map[*types.Named]struct{ value, pointer *types.MethodSet } // method sets for named N and *N
+	others map[types.Type]*types.MethodSet                            // all other types
+}
+
+// MethodSet returns the method set of type T.  It is thread-safe.
+//
+// If cache is nil, this function is equivalent to types.NewMethodSet(T).
+// Utility functions can thus expose an optional *MethodSetCache
+// parameter to clients that care about performance.
+func (cache *MethodSetCache) MethodSet(T types.Type) *types.MethodSet {
+	if cache == nil {
+		return types.NewMethodSet(T)
+	}
+	cache.mu.Lock()
+	defer cache.mu.Unlock()
+
+	switch T := aliases.Unalias(T).(type) {
+	case *types.Named:
+		return cache.lookupNamed(T).value
+
+	case *types.Pointer:
+		if N, ok := aliases.Unalias(T.Elem()).(*types.Named); ok {
+			return cache.lookupNamed(N).pointer
+		}
+	}
+
+	// all other types
+	// (The map uses pointer equivalence, not type identity.)
+	mset := cache.others[T]
+	if mset == nil {
+		mset = types.NewMethodSet(T)
+		if cache.others == nil {
+			cache.others = make(map[types.Type]*types.MethodSet)
+		}
+		cache.others[T] = mset
+	}
+	return mset
+}
+
+func (cache *MethodSetCache) lookupNamed(named *types.Named) struct{ value, pointer *types.MethodSet } {
+	if cache.named == nil {
+		cache.named = make(map[*types.Named]struct{ value, pointer *types.MethodSet })
+	}
+	// Avoid recomputing mset(*T) for each distinct Pointer
+	// instance whose underlying type is a named type.
+	msets, ok := cache.named[named]
+	if !ok {
+		msets.value = types.NewMethodSet(named)
+		msets.pointer = types.NewMethodSet(types.NewPointer(named))
+		cache.named[named] = msets
+	}
+	return msets
+}
diff --git a/vendor/golang.org/x/tools/go/types/typeutil/ui.go b/vendor/golang.org/x/tools/go/types/typeutil/ui.go
new file mode 100644
index 0000000..a0c1a60
--- /dev/null
+++ b/vendor/golang.org/x/tools/go/types/typeutil/ui.go
@@ -0,0 +1,55 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package typeutil
+
+// This file defines utilities for user interfaces that display types.
+
+import (
+	"go/types"
+
+	"golang.org/x/tools/internal/aliases"
+)
+
+// IntuitiveMethodSet returns the intuitive method set of a type T,
+// which is the set of methods you can call on an addressable value of
+// that type.
+//
+// The result always contains MethodSet(T), and is exactly MethodSet(T)
+// for interface types and for pointer-to-concrete types.
+// For all other concrete types T, the result additionally
+// contains each method belonging to *T if there is no identically
+// named method on T itself.
+//
+// This corresponds to user intuition about method sets;
+// this function is intended only for user interfaces.
+//
+// The order of the result is as for types.MethodSet(T).
+func IntuitiveMethodSet(T types.Type, msets *MethodSetCache) []*types.Selection {
+	isPointerToConcrete := func(T types.Type) bool {
+		ptr, ok := aliases.Unalias(T).(*types.Pointer)
+		return ok && !types.IsInterface(ptr.Elem())
+	}
+
+	var result []*types.Selection
+	mset := msets.MethodSet(T)
+	if types.IsInterface(T) || isPointerToConcrete(T) {
+		for i, n := 0, mset.Len(); i < n; i++ {
+			result = append(result, mset.At(i))
+		}
+	} else {
+		// T is some other concrete type.
+		// Report methods of T and *T, preferring those of T.
+		pmset := msets.MethodSet(types.NewPointer(T))
+		for i, n := 0, pmset.Len(); i < n; i++ {
+			meth := pmset.At(i)
+			if m := mset.Lookup(meth.Obj().Pkg(), meth.Obj().Name()); m != nil {
+				meth = m
+			}
+			result = append(result, meth)
+		}
+
+	}
+	return result
+}