From c7f0d54328c4836f7e492da8cf9ca67f6b99926a Mon Sep 17 00:00:00 2001
From: Christoffer Lerno <christoffer@aegik.com>
Date: Sun, 18 May 2025 23:40:52 +0200
Subject: [PATCH] Designated const initializers with `{}` would overwrite the
 parent field.

---
 releasenotes.md                               |  1 +
 src/compiler/sema_initializers.c              | 12 +++----
 .../bitstruct/designated_initializer_bug.c3t  | 31 +++++++++++++++++++
 3 files changed, 37 insertions(+), 7 deletions(-)
 create mode 100644 test/test_suite/bitstruct/designated_initializer_bug.c3t

diff --git a/releasenotes.md b/releasenotes.md
index 417a77956..8a1bdd170 100644
--- a/releasenotes.md
+++ b/releasenotes.md
@@ -32,6 +32,7 @@
 - $define did not correctly handle generic types #2140.
 - Incorrect parsing of call attributes #2144.
 - Error when using named argument on trailing macro body expansion #2139.
+- Designated const initializers with `{}` would overwrite the parent field.
 
 ### Stdlib changes
 - Added `String.quick_ztr` and `String.is_zstr`
diff --git a/src/compiler/sema_initializers.c b/src/compiler/sema_initializers.c
index d18bbe3e6..52993c7e4 100644
--- a/src/compiler/sema_initializers.c
+++ b/src/compiler/sema_initializers.c
@@ -939,18 +939,16 @@ static inline void sema_update_const_initializer_with_designator_struct(ConstIni
 	DesignatorElement **next_element = curr + 1;
 	bool is_last_path_element = next_element == end;
 
-	// Optimize in case this is a zero, e.g. [12].b = {}
-	if (is_last_path_element && sema_initializer_list_is_empty(value))
-	{
-		const_init->kind = CONST_INIT_ZERO;
-		ASSERT(type_flatten(value->type)->type_kind != TYPE_SLICE);
-		return;
-	}
 	Decl **elements = const_init->type->decl->strukt.members;
 
 	// Convert a zero struct and expand it into all its parts.
 	if (const_init->kind == CONST_INIT_ZERO)
 	{
+		if (is_last_path_element && sema_initializer_list_is_empty(value))
+		{
+			// In this case we can ignore it.
+			return;
+		}
 		const_init->init_struct = NULL;
 		// Allocate array containing all elements { a, b, c ... }
 		FOREACH_IDX(i, Decl *, el, elements)
diff --git a/test/test_suite/bitstruct/designated_initializer_bug.c3t b/test/test_suite/bitstruct/designated_initializer_bug.c3t
new file mode 100644
index 000000000..bacf09961
--- /dev/null
+++ b/test/test_suite/bitstruct/designated_initializer_bug.c3t
@@ -0,0 +1,31 @@
+// #target: macos-x64
+
+module test;
+typedef Kind = int;
+const Kind KIND_0 = 0;
+const Kind KIND_1 = 1;
+
+struct Foo
+{
+	int a;
+}
+struct Descriptor2
+{
+    Kind kind;
+    Foo flags;
+}
+
+Descriptor2 descriptor1 = {
+    .kind = KIND_1,
+    .flags = {},
+};
+
+fn int main()
+{
+	Descriptor2 d = descriptor1;
+	return 0;
+}
+
+/* #expect: test.ll
+
+@test.descriptor1 = local_unnamed_addr global %Descriptor2 { i32 1, %Foo zeroinitializer }, align 4