Rollup merge of #44276 - mattico:test-35376, r=alexcrichton

Add test for #35676

Closes #35676

src/test/run-pass/issue-35376.rs

@@ -0,0 +1,51 @@
+// Copyright 2016 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(specialization)]
+
+fn main() {}
+
+pub trait Alpha<T> { }
+
+pub trait Beta {
+    type Event;
+}
+
+pub trait Delta {
+    type Handle;
+    fn process(&self);
+}
+
+pub struct Parent<A, T>(A, T);
+
+impl<A, T> Delta for Parent<A, T>
+where A: Alpha<T::Handle>,
+      T: Delta,
+      T::Handle: Beta<Event = <Handle as Beta>::Event> {
+    type Handle = Handle;
+    default fn process(&self) {
+        unimplemented!()
+    }
+}
+
+impl<A, T> Delta for Parent<A, T>
+where A: Alpha<T::Handle> + Alpha<Handle>,
+      T: Delta,
+      T::Handle: Beta<Event = <Handle as Beta>::Event> {
+      fn process(&self) {
+        unimplemented!()
+      }
+}
+
+pub struct Handle;
+
+impl Beta for Handle {
+    type Event = ();
+}