Value: implement reinterpreting enum field index as integer

Closes #15019

1 files changed, 20 insertions, 0 deletions

diff --git a/test/behavior/union.zig b/test/behavior/union.zig
index ff3f0b7e54..010b4a1ffa 100644
--- a/test/behavior/union.zig
+++ b/test/behavior/union.zig
@@ -1513,3 +1513,23 @@ test "packed union with zero-bit field" {
     };
     try S.doTest(.{ .nested = .{ .zero = {} }, .bar = 42 });
 }
+
+test "reinterpreting enum value inside packed union" {
+    if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
+
+    const U = packed union {
+        tag: enum { a, b },
+        val: u8,
+
+        fn doTest() !void {
+            var u: @This() = .{ .tag = .a };
+            u.val += 1;
+            try expect(u.tag == .b);
+        }
+    };
+    try U.doTest();
+    comptime try U.doTest();
+}