From 93640699be70d55411e1b0c8abfada7e48049920 Mon Sep 17 00:00:00 2001
From: Christoffer Lerno <christoffer@aegik.com>
Date: Tue, 17 Jun 2025 16:49:46 +0200
Subject: [PATCH] Support distrinct types as the base type of bitstructs. #2218

---
 releasenotes.md                               |  1 +
 src/compiler/sema_decls.c                     |  4 +-
 .../bitstruct/bitstruct_with_distinct.c3t     | 48 +++++++++++++++++++
 3 files changed, 51 insertions(+), 2 deletions(-)
 create mode 100644 test/test_suite/bitstruct/bitstruct_with_distinct.c3t

diff --git a/releasenotes.md b/releasenotes.md
index cffb42753..a74cc319e 100644
--- a/releasenotes.md
+++ b/releasenotes.md
@@ -22,6 +22,7 @@
 - The form-feed character '\f' is no longer valid white space.
 - Show code that caused unreachable code #2207
 - Allow generics over distinct types #2216.
+- Support distrinct types as the base type of bitstructs. #2218
 
 ### Fixes
 - `-2147483648`, MIN literals work correctly.
diff --git a/src/compiler/sema_decls.c b/src/compiler/sema_decls.c
index dab5074d6..89d6f777d 100755
--- a/src/compiler/sema_decls.c
+++ b/src/compiler/sema_decls.c
@@ -1061,8 +1061,8 @@ static bool sema_analyse_bitstruct(SemaContext *context, Decl *decl, bool *erase
 	if (*erase_decl) return true;
 	DEBUG_LOG("Beginning analysis of %s.", decl->name ? decl->name : ".anon");
 	if (!sema_resolve_type_info(context, decl->strukt.container_type, RESOLVE_TYPE_DEFAULT)) return false;
-	Type *type = decl->strukt.container_type->type->canonical;
-	Type *base_type = type->type_kind == TYPE_ARRAY ? type->array.base : type;
+	Type *type = type_flatten(decl->strukt.container_type->type->canonical);
+	Type *base_type = type->type_kind == TYPE_ARRAY ? type_flatten(type->array.base) : type;
 	if (!type_is_integer(base_type))
 	{
 		SEMA_ERROR(decl->strukt.container_type, "The type of the bitstruct cannot be %s but must be an integer or an array of integers.",
diff --git a/test/test_suite/bitstruct/bitstruct_with_distinct.c3t b/test/test_suite/bitstruct/bitstruct_with_distinct.c3t
new file mode 100644
index 000000000..f06f7f479
--- /dev/null
+++ b/test/test_suite/bitstruct/bitstruct_with_distinct.c3t
@@ -0,0 +1,48 @@
+// #target: macos-x64
+module test;
+typedef Foo = int;
+
+bitstruct Bar : Foo
+{
+	bool a : 0;
+	Foo x : 1..4;
+}
+
+typedef Baz = char;
+
+bitstruct Bar2 : Baz[3]
+{
+	bool x;
+}
+
+fn int main()
+{
+	Bar x;
+	Bar2 y;
+	x.a = true;
+	x.x = 100;
+	return 0;
+}
+
+/* #expect: test.ll
+
+define i32 @main() #0 {
+entry:
+  %x = alloca i32, align 4
+  %y = alloca [3 x i8], align 1
+  store i32 0, ptr %x, align 4
+  store i8 0, ptr %y, align 1
+  %ptradd = getelementptr inbounds i8, ptr %y, i64 1
+  store i8 0, ptr %ptradd, align 1
+  %ptradd1 = getelementptr inbounds i8, ptr %y, i64 2
+  store i8 0, ptr %ptradd1, align 1
+  %0 = load i32, ptr %x, align 4
+  %1 = and i32 %0, -2
+  %2 = or i32 %1, 1
+  store i32 %2, ptr %x, align 4
+  %3 = load i32, ptr %x, align 4
+  %4 = and i32 %3, -31
+  %5 = or i32 %4, 8
+  store i32 %5, ptr %x, align 4
+  ret i32 0
+}