From c0895afd99c8befd0d89580bfaa71bb532ba9c7f Mon Sep 17 00:00:00 2001
From: Thomas Voss <mail@thomasvoss.com>
Date: Wed, 26 Jun 2024 23:50:37 +0200
Subject: Support unary plus and minus

---
 README         | 20 +++++++++++++++++---
 src/analyzer.c | 20 ++++++++++++++++++++
 src/codegen.c  | 24 +++++++++++++++++-------
 src/parser.c   | 15 +++++++++++++++
 src/parser.h   | 10 +++++++++-
 5 files changed, 78 insertions(+), 11 deletions(-)

diff --git a/README b/README
index a770ac8..8895385 100644
--- a/README
+++ b/README
@@ -117,7 +117,7 @@ The build script also accepts some subcommands.  They are as follows:
     different integer types which may have the same size (i.e. int and
     int64)
 
-        pub MyFunc :: () {
+        pub my_func :: () {
             x: int = 69;
             y: i64 = x;  /* Compile-time error */
         }
@@ -128,10 +128,24 @@ The build script also accepts some subcommands.  They are as follows:
         /* Recall that constants (including functions!) can be declared
            in any order.  This lets us define Inner *after* it gets
            called by the assignment to ‘x’. */
-        Outer :: () {
+        outer :: () {
             x := Inner(5);
 
-            Inner :: (x: int) int {
+            inner :: (x: int) int {
                 return x;
             }
         }
+
+8.  No increment/decrement operators.  The following functions both
+    return 42 as the return values are parsed as (+ (+ 42)) and
+    (- (- 42)) respectively.
+
+        x := 42;
+
+        returns_42 :: () int {
+            return ++x;
+        }
+
+        returns_42′ :: () int {
+            return --x;
+        }
diff --git a/src/analyzer.c b/src/analyzer.c
index 6e6df9d..c74e89f 100644
--- a/src/analyzer.c
+++ b/src/analyzer.c
@@ -309,6 +309,16 @@ analyzeexpr(struct azctx ctx, scope_t *scps, type_t *types, ast_t ast,
 
 		err("analyzer: Unknown symbol ‘%.*s’", SV_PRI_ARGS(sv));
 	}
+	case ASTUNNEG: {
+		idx_t ni, rhs;
+		rhs = ast.kids[i].rhs;
+		ni = analyzeexpr(ctx, scps, types, ast, aux, toks, rhs);
+		type_t t = types[rhs];
+		if (t.kind != TYPE_NUM || !t.issigned)
+			err("analyzer: Unary negation is reserved for signed numeric types");
+		types[i] = t;
+		return ni;
+	}
 	case ASTFN:
 		return analyzefn(ctx, scps, types, ast, aux, toks, i);
 	default:
@@ -476,6 +486,16 @@ constfoldexpr(struct cfctx ctx, mpq_t *folds, scope_t *scps, type_t *types,
 			}
 		}
 	}
+	case ASTUNNEG: {
+		idx_t rhs = ast.kids[i].rhs;
+		idx_t ni = constfoldexpr(ctx, folds, scps, types, ast, toks, rhs);
+		mpq_t *x = folds + rhs;
+		if (MPQ_IS_INIT(*x)) {
+			MPQCPY(folds[i], *x);
+			mpq_neg(folds[i], folds[i]);
+		}
+		return ni;
+	}
 	case ASTFN:
 		return constfoldblk(ctx, folds, scps, types, ast, toks,
 		                    ast.kids[i].rhs);
diff --git a/src/codegen.c b/src/codegen.c
index a9b1430..9e9e329 100644
--- a/src/codegen.c
+++ b/src/codegen.c
@@ -211,13 +211,23 @@ codegentypedexpr(struct cgctx ctx, idx_t i, type_t type, LLVMValueRef *outv)
 		return fwdnode(ctx.ast, i);
 	}
 
-	assert(ctx.ast.kinds[i] == ASTIDENT);
-
-	strview_t sv = ctx.toks.strs[ctx.ast.lexemes[i]];
-	LLVMTypeRef t = type2llvm(ctx, ctx.types[i]);
-	LLVMValueRef ptrval = symtab_insert(&ctx.scps[ctx.scpi].map, sv, NULL)->v;
-	*outv = LLVMBuildLoad2(ctx.bob, t, ptrval, "loadtmp");
-	return fwdnode(ctx.ast, i);
+	switch (ctx.ast.kinds[i]) {
+	case ASTIDENT: {
+		strview_t sv = ctx.toks.strs[ctx.ast.lexemes[i]];
+		LLVMTypeRef t = type2llvm(ctx, ctx.types[i]);
+		LLVMValueRef ptrval = symtab_insert(&ctx.scps[ctx.scpi].map, sv, NULL)->v;
+		*outv = LLVMBuildLoad2(ctx.bob, t, ptrval, "loadtmp");
+		return fwdnode(ctx.ast, i);
+	}
+	case ASTUNNEG: {
+		LLVMValueRef v;
+		idx_t ni = codegentypedexpr(ctx, ctx.ast.kids[i].rhs, ctx.types[i], &v);
+		*outv = LLVMBuildNeg(ctx.bob, v, "negtmp");
+		return ni;
+	}
+	default:
+		__builtin_unreachable();
+	}
 }
 
 idx_t
diff --git a/src/parser.c b/src/parser.c
index fa1c720..cb8aa8f 100644
--- a/src/parser.c
+++ b/src/parser.c
@@ -61,6 +61,7 @@ fwdnode(ast_t ast, idx_t i)
 		case ASTBINSUB:
 		case ASTCDECL:
 		case ASTFN:
+		case ASTUNNEG:
 			i = ast.kids[i].rhs;
 			break;
 		case ASTIDENT:
@@ -219,6 +220,13 @@ parseexpr(ast_t *ast, aux_t *aux, lexemes_t toks)
 {
 	(void)aux;
 	idx_t i = astalloc(ast);
+
+	/* Unary plus is kind of a fake syntactic construct.  We just pretend
+	   like it doesn’t exist, but allow it in the syntax to be consistent
+	   with unary negation. */
+	while (toks.kinds[toksidx] == LEXPLUS)
+		toksidx++;
+
 	ast->lexemes[i] = toksidx;
 
 	switch (toks.kinds[toksidx]) {
@@ -230,6 +238,13 @@ parseexpr(ast_t *ast, aux_t *aux, lexemes_t toks)
 		toksidx++;
 		ast->kinds[i] = ASTIDENT;
 		break;
+	case LEXMINUS: {
+		toksidx++;
+		ast->kinds[i] = ASTUNNEG;
+		idx_t rhs = parseexpr(ast, aux, toks);
+		ast->kids[i].rhs = rhs;
+		break;
+	}
 	default:
 		err("parser: Expected expression");
 	}
diff --git a/src/parser.h b/src/parser.h
index d8991c0..055350a 100644
--- a/src/parser.h
+++ b/src/parser.h
@@ -50,11 +50,19 @@ enum {
 	   ‘return rhs’ */
 	ASTRET,
 
+	/* Unary negation
+	   ‘-rhs’ */
+	ASTUNNEG,
+
+	/* NOTE: Ensure that the enumerations defined above this comment do
+	   not exceed 37 — the value of ‘%’ — or they will conflict with the
+	   definitions below. */
+
 	/* Binary add
 	   ‘lhs + rhs’ */
 	ASTBINADD = '+',
 
-	/* Binary sub
+	/* Binary subtraction
 	   ‘lhs - rhs’ */
 	ASTBINSUB = '-',
 
-- 
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