Mir typeck Cast for Unsize value

src/test/compile-fail/mir_check_cast_unsize.rs

@@ -0,0 +1,24 @@
+// Copyright 2017 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.
+
+// compile-flags: -Z borrowck=mir -Z nll
+
+#![allow(dead_code)]
+#![feature(dyn_trait)]
+
+use std::fmt::Debug;
+
+fn bar<'a>(x: &'a u32) -> &'static dyn Debug {
+    //~^ ERROR free region `'_#1r` does not outlive free region `'static`
+    x
+    //~^ WARNING not reporting region error due to -Znll
+}
+
+fn main() {}