Add regression test for #9837.

Fixes https://github.com/rust-lang/rust/issues/9837

src/test/run-pass/issue-9837.rs

@@ -0,0 +1,20 @@
+// Copyright 2016 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.
+
+const C1: i32 = 0x12345678;
+const C2: isize = C1 as i16 as isize;
+
+enum E {
+    V = C2
+}
+
+fn main() {
+    assert_eq!(C2 as u64, E::V as u64);
+}