Add test for #5783

src/test/run-pass/issue-5783.rs

+// 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.
+
+// Issue #5783
+// Nondeterministic behavior when referencing a closure more than once
+
+fn main() {
+    let a: &fn(int) -> @fn(int) -> int = |x:int| |y:int| -> int x + y;
+    let b = a(2);
+    assert!(a(2)(3) == 5);
+    assert!(b(6) == 8);
+}