From 99aa0d3a35a86d00c488554ff712c922f7133005 Mon Sep 17 00:00:00 2001
From: Laytan Laats <laytanlaats@hotmail.com>
Date: Mon, 12 Aug 2024 00:02:05 +0200
Subject: [PATCH] fix type switching over internal pointer union

Fixes #3947
---
 src/llvm_backend_stmt.cpp             |  2 +-
 tests/internal/test_union_switch.odin | 24 ++++++++++++++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)
 create mode 100644 tests/internal/test_union_switch.odin

diff --git a/src/llvm_backend_stmt.cpp b/src/llvm_backend_stmt.cpp
index e70cc503e..8f1c3a123 100644
--- a/src/llvm_backend_stmt.cpp
+++ b/src/llvm_backend_stmt.cpp
@@ -1646,7 +1646,7 @@ gb_internal void lb_build_type_switch_stmt(lbProcedure *p, AstTypeSwitchStmt *ss
 		union_data = lb_emit_conv(p, parent_ptr, t_rawptr);
 		Type *union_type = type_deref(parent_ptr.type);
 		if (is_type_union_maybe_pointer(union_type)) {
-			tag = lb_emit_conv(p, lb_emit_comp_against_nil(p, Token_NotEq, union_data), t_int);
+			tag = lb_emit_conv(p, lb_emit_comp_against_nil(p, Token_NotEq, parent_value), t_int);
 		} else if (union_tag_size(union_type) == 0) {
 			tag = {}; // there is no tag for a zero sized union
 		} else {
diff --git a/tests/internal/test_union_switch.odin b/tests/internal/test_union_switch.odin
new file mode 100644
index 000000000..f96c0e55e
--- /dev/null
+++ b/tests/internal/test_union_switch.odin
@@ -0,0 +1,24 @@
+package test_internal
+
+import "core:log"
+import "core:testing"
+
+@(test)
+test_internal_pointer_union_switch :: proc(t: ^testing.T) {
+	foo: Maybe(^int)
+
+	switch _ in foo {
+	case ^int:
+		log.error("incorrect case")
+	case nil:
+	}
+
+	v := 1
+	foo = &v
+
+	switch _ in foo {
+	case ^int:
+	case nil:
+		log.error("incorrect case")
+	}
+}