auto merge of #20527 : nikomatsakis/rust/japaric-boxed-uc-ice-fix, r=aturon

This fixes an ICE that japaric was encountering in the wf checker.

r? @aturon

src/test/run-pass/wf-bound-region-in-object-type.rs

@@ -0,0 +1,26 @@
+// 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 the `wf` checker properly handles bound regions in object
+// types. Compiling this code used to trigger an ICE.
+
+pub struct Context<'tcx> {
+    vec: &'tcx Vec<int>
+}
+
+pub type Cmd<'a> = &'a int;
+
+pub type DecodeInlinedItem<'a> =
+    Box<for<'tcx> FnMut(Cmd, &Context<'tcx>) -> Result<&'tcx int, ()> + 'a>;
+
+fn foo(d: DecodeInlinedItem) {
+}
+
+fn main() { }