Regression test for #20225

Closes #20225.

Author: tamird

src/test/compile-fail/issue-20225.rs

@@ -0,0 +1,22 @@
+// 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.
+
+#![feature(unboxed_closures)]
+
+struct Foo;
+
+impl<'a, T> Fn<(&'a T,)> for Foo {
+  type Output = ();
+
+  extern "rust-call" fn call(&self, (_,): (T,)) {}
+  //~^ ERROR: has an incompatible type for trait: expected &-ptr
+}
+
+fn main() {}