Improve error message when encountering recursively defined structs. #2146

releasenotes.md

@@ -13,6 +13,7 @@
 - Improve error message when using keywords as functions/macros/variables #2133.
 - Deprecate `MyEnum.elements`.
 - Deprecate `SomeFn.params`.
+- Improve error message when encountering recursively defined structs. #2146
 
 ### Fixes
 - Assert triggered when casting from `int[2]` to `uint[2]` #2115

src/compiler/sema_decls.c

@@ -546,6 +546,11 @@ static bool sema_analyse_struct_members(SemaContext *context, Decl *decl)
 
 		// Grab the alignment of the member type
 		AlignSize member_type_alignment;
+		if (type_is_user_defined(member_type) && member_type->decl->resolve_status == RESOLVE_RUNNING)
+		{
+			SEMA_ERROR(member, "Recursive defintion of %s.", type_quoted_error_string(member_type));
+			return decl_poison(decl);
+		}
 		if (!sema_set_abi_alignment(context, member->type, &member_type_alignment)) return decl_poison(decl);
 		// And get the natural alignment
 		AlignSize member_natural_alignment = sema_get_max_natural_alignment(member->type);

test/test_suite/struct/struct_recursive.c3

@@ -0,0 +1,9 @@
+struct GlobalNode
+{
+	Ast node;
+}
+
+struct Ast
+{
+	GlobalNode global; // #error: Recursive defintion of 'GlobalNode'
+}