testsuite: Test for #6153, closes #6153

Author: catamorphism

src/test/run-pass/issue-6153.rs

@@ -0,0 +1,20 @@
+// Copyright 2013 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.
+
+fn swap(f: &fn(~[int]) -> ~[int]) -> ~[int] {
+    let x = ~[1, 2, 3];
+    f(x)
+}
+
+fn main() {
+    let v = swap(|mut x| { x.push(4); x });
+    let w = do swap |mut x| { x.push(4); x };
+    assert_eq!(v, w);
+}