Add regression test for issue #16791

src/test/run-pass/unboxed-closures-monomorphization.rs

+// Copyright 2014 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.
+
+// Test that unboxed closures in contexts with free type parameters
+// monomorphize correctly (issue #16791)
+
+#![feature(unboxed_closures)]
+
+fn main(){
+    fn bar<'a, T:'a> (t: T) -> Box<FnOnce<(),T> + 'a> {
+        box move |:| t
+    }
+
+    let f = bar(42u);
+    assert_eq!(f.call_once(()), 42);
+
+    let f = bar("forty-two");
+    assert_eq!(f.call_once(()), "forty-two");
+
+    let x = 42u;
+    let f = bar(&x);
+    assert_eq!(f.call_once(()), &x);
+
+    #[deriving(Show, PartialEq)]
+    struct Foo(uint, &'static str);
+    let x = Foo(42, "forty-two");
+    let f = bar(x);
+    assert_eq!(f.call_once(()), x);
+}