Add regression tests for #23304

Closes #23304

src/test/run-pass/issue-23304-1.rs

@@ -0,0 +1,34 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![allow(dead_code)]
+
+#[repr(u8)]
+#[allow(dead_code)]
+enum ValueType {
+    DOUBLE              = 0x00,
+    INT32               = 0x01,
+}
+
+#[repr(u32)]
+enum ValueTag {
+    INT32                = 0x1FFF0u32 | (ValueType::INT32 as u32),
+    X,
+}
+
+#[repr(u64)]
+enum ValueShiftedTag {
+    INT32        = ValueTag::INT32 as u64,
+    X,
+}
+
+fn main() {
+    println!("{}", ValueTag::INT32 as u32);
+}

src/test/run-pass/issue-23304-2.rs

@@ -0,0 +1,17 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![allow(dead_code)]
+
+enum X { A = 0 as isize }
+
+enum Y { A = X::A as isize }
+
+fn main() { }