From 5a36f0bc166634dfca5fa26ad92648df821b9cdd Mon Sep 17 00:00:00 2001
From: Christoffer Lerno <christoffer@aegik.com>
Date: Sat, 18 Jan 2025 22:40:58 +0100
Subject: [PATCH] Fix issue with `@const` where the statement `$foo = 1;` was
 not considered constant.

---
 releasenotes.md                              |  1 +
 src/compiler/sema_const.c                    |  2 +-
 src/compiler/sema_decls.c                    | 18 +++++++++++++++-
 test/test_suite/compile_time/concat_const.c3 | 22 ++++++++++++++++++++
 4 files changed, 41 insertions(+), 2 deletions(-)
 create mode 100644 test/test_suite/compile_time/concat_const.c3

diff --git a/releasenotes.md b/releasenotes.md
index 6c9076577..dddf9c7f4 100644
--- a/releasenotes.md
+++ b/releasenotes.md
@@ -10,6 +10,7 @@
 - Fix bug in SHA1 for longer blocks #1854.
 - Fix lack of location for reporting lambdas with missing return statement #1857.
 - Compiler allows a generic module to be declared with different parameters #1856.
+- Fix issue with `@const` where the statement `$foo = 1;` was not considered constant.
 
 ### Stdlib changes
 - Added '%h' and '%H' for printing out binary data in hexadecimal using the formatter.
diff --git a/src/compiler/sema_const.c b/src/compiler/sema_const.c
index b2cd1faec..4a455b402 100644
--- a/src/compiler/sema_const.c
+++ b/src/compiler/sema_const.c
@@ -319,7 +319,7 @@ bool sema_expr_analyse_ct_concat(SemaContext *context, Expr *concat_expr, Expr *
 	if (!sema_analyse_expr(context, left)) return false;
 	if (!sema_cast_const(left)) RETURN_SEMA_ERROR(left, "Expected this to evaluate to a constant value.");
 	if (!sema_analyse_expr(context, right)) return false;
-	if (!sema_cast_const(right)) RETURN_SEMA_ERROR(left, "Expected this to evaluate to a constant value.");
+	if (!sema_cast_const(right)) RETURN_SEMA_ERROR(right, "Expected this to evaluate to a constant value.");
 	Type *element_type = left->type->canonical;
 	Type *right_type = right->type->canonical;
 	switch (left->const_expr.const_kind)
diff --git a/src/compiler/sema_decls.c b/src/compiler/sema_decls.c
index edeadd8ef..08e0f6212 100755
--- a/src/compiler/sema_decls.c
+++ b/src/compiler/sema_decls.c
@@ -3829,6 +3829,23 @@ static inline bool sema_analyse_macro(SemaContext *context, Decl *decl, bool *er
 					if (body->next) RETURN_SEMA_ERROR(body, "There should not be any statements after 'return'.");
 					body = NULL;
 					continue;
+				case AST_EXPR_STMT:
+					// For some cases we KNOW it's not correct.
+					switch (body->expr_stmt->expr_kind)
+					{
+						case EXPR_IDENTIFIER:
+						case EXPR_LAMBDA:
+						case EXPR_FORCE_UNWRAP:
+						case EXPR_ASM:
+						case EXPR_EXPR_BLOCK:
+						case EXPR_TERNARY:
+						case EXPR_RETHROW:
+							break;
+						default:
+							body = astptrzero(body->next);
+							continue;
+					}
+					FALLTHROUGH;
 				case AST_POISONED:
 				case AST_ASM_STMT:
 				case AST_ASM_LABEL:
@@ -3840,7 +3857,6 @@ static inline bool sema_analyse_macro(SemaContext *context, Decl *decl, bool *er
 				case AST_CONTINUE_STMT:
 				case AST_DEFAULT_STMT:
 				case AST_DEFER_STMT:
-				case AST_EXPR_STMT:
 				case AST_FOR_STMT:
 				case AST_FOREACH_STMT:
 				case AST_IF_CATCH_SWITCH_STMT:
diff --git a/test/test_suite/compile_time/concat_const.c3 b/test/test_suite/compile_time/concat_const.c3
new file mode 100644
index 000000000..88766eeb0
--- /dev/null
+++ b/test/test_suite/compile_time/concat_const.c3
@@ -0,0 +1,22 @@
+module wi3enrich;
+import std::io;
+import std::os::env;
+
+macro String to_string(uint $num) @const
+{
+    char[] $res;
+    int $i = 0;
+    $for (;$num != 0;)
+        $res = $res +++ (char) ('0' + $num % 10);
+        $num = $num / 10;
+        $i++;
+    $endfor
+    $res = $res +++ '\0';
+    return (String) $res;
+}
+
+fn int main(String[] args)
+{
+	io::printn(to_string(4));
+    return 0;
+}