Add test

src/test/ui/async-with-closure.rs

@@ -0,0 +1,26 @@
+// compile-pass
+// edition:2018
+
+#![feature(async_await, await_macro)]
+
+trait MyClosure {
+    type Args;
+}
+
+impl<R> MyClosure for dyn FnMut() -> R
+where R: 'static {
+    type Args = ();
+}
+
+struct MyStream<C: ?Sized + MyClosure> {
+    x: C::Args,
+}
+
+async fn get_future<C: ?Sized + MyClosure>(_stream: MyStream<C>) {}
+
+async fn f() {
+    let messages: MyStream<FnMut()> = unimplemented!();
+    await!(get_future(messages));
+}
+
+fn main() {}