Regression test for #20396

Closes #20396.

src/test/run-pass/issue-20396.rs

@@ -0,0 +1,23 @@
+// 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.
+
+#![allow(dead_code)]
+
+trait Foo<T> {
+    fn noop(&self, _: T);
+}
+
+enum Bar<T> { Bla(T) }
+
+struct Baz<'a> {
+    inner: for<'b> Foo<Bar<&'b ()>> + 'a,
+}
+
+fn main() {}