Add regression test for rust-lang#53249.

src/test/ui/issue-53249.rs

@@ -0,0 +1,47 @@
+// compile-pass
+// edition:2018
+
+#![feature(arbitrary_self_types, async_await, await_macro)]
+
+use std::task::{self, Poll};
+use std::future::Future;
+use std::marker::Unpin;
+use std::pin::Pin;
+
+// This is a regression test for a ICE/unbounded recursion issue relating to async-await.
+
+#[derive(Debug)]
+#[must_use = "futures do nothing unless polled"]
+pub struct Lazy<F> {
+    f: Option<F>
+}
+
+impl<F> Unpin for Lazy<F> {}
+
+pub fn lazy<F, R>(f: F) -> Lazy<F>
+    where F: FnOnce(&mut task::Context) -> R,
+{
+    Lazy { f: Some(f) }
+}
+
+impl<R, F> Future for Lazy<F>
+    where F: FnOnce(&mut task::Context) -> R,
+{
+    type Output = R;
+
+    fn poll(mut self: Pin<&mut Self>, cx: &mut task::Context) -> Poll<R> {
+        Poll::Ready((self.f.take().unwrap())(cx))
+    }
+}
+
+async fn __receive<WantFn, Fut>(want: WantFn) -> ()
+    where Fut: Future<Output = ()>, WantFn: Fn(&Box<Send + 'static>) -> Fut,
+{
+    await!(lazy(|_| ()));
+}
+
+pub fn basic_spawn_receive() {
+    async { await!(__receive(|_| async { () })) };
+}
+
+fn main() {}