Add regression test for #20413

Closes #20413.

src/test/compile-fail/issue-20413.rs

@@ -0,0 +1,25 @@
+// 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.
+
+trait Foo {
+  fn answer(self);
+}
+
+struct NoData<T>;
+//~^ ERROR: parameter `T` is never used
+
+impl<T> Foo for T where NoData<T>: Foo {
+//~^ ERROR: overflow evaluating the requirement
+  fn answer(self) {
+    let val: NoData<T> = NoData;
+  }
+}
+
+fn main() {}