Sema: fix access of inactive union field when enum and union fields are in different order

Closes #12667

1 files changed, 23 insertions, 0 deletions

diff --git a/test/cases/compile_errors/access_inactive_union_field_comptime.zig b/test/cases/compile_errors/access_inactive_union_field_comptime.zig
new file mode 100644
index 0000000000..d990a85f9e
--- /dev/null
+++ b/test/cases/compile_errors/access_inactive_union_field_comptime.zig
@@ -0,0 +1,23 @@
+const Enum = enum(u32) { a, b };
+const TaggedUnion = union(Enum) {
+    b: []const u8,
+    a: []const u8,
+};
+pub export fn entry() void {
+    const result = TaggedUnion{ .b = "b" };
+    _ = result.b;
+    _ = result.a;
+}
+pub export fn entry1() void {
+    const result = TaggedUnion{ .b = "b" };
+    _ = &result.b;
+    _ = &result.a;
+}
+
+// error
+// backend=stage2
+// target=native
+//
+// :9:15: error: access of union field 'a' while field 'b' is active
+// :2:21: note: union declared here
+// :14:16: error: access of union field 'a' while field 'b' is active