1 files changed, 100 insertions, 0 deletions
diff --git a/src/test/ui/async-await/async-closure.rs b/src/test/ui/async-await/async-closure.rs
new file mode 100644
index 000000000..12d66b19e
--- /dev/null
+++ b/src/test/ui/async-await/async-closure.rs
@@ -0,0 +1,100 @@
+// run-pass
+
+// revisions: default nomiropt
+//[nomiropt]compile-flags: -Z mir-opt-level=0
+
+// edition:2018
+// aux-build:arc_wake.rs
+
+#![feature(async_closure)]
+
+extern crate arc_wake;
+
+use std::pin::Pin;
+use std::future::Future;
+use std::sync::{
+    Arc,
+    atomic::{self, AtomicUsize},
+};
+use std::task::{Context, Poll};
+use arc_wake::ArcWake;
+
+struct Counter {
+    wakes: AtomicUsize,
+}
+
+impl ArcWake for Counter {
+    fn wake(self: Arc<Self>) {
+        Self::wake_by_ref(&self)
+    }
+    fn wake_by_ref(arc_self: &Arc<Self>) {
+        arc_self.wakes.fetch_add(1, atomic::Ordering::SeqCst);
+    }
+}
+
+struct WakeOnceThenComplete(bool);
+
+fn wake_and_yield_once() -> WakeOnceThenComplete { WakeOnceThenComplete(false) }
+
+impl Future for WakeOnceThenComplete {
+    type Output = ();
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<()> {
+        if self.0 {
+            Poll::Ready(())
+        } else {
+            cx.waker().wake_by_ref();
+            self.0 = true;
+            Poll::Pending
+        }
+    }
+}
+
+fn async_closure(x: u8) -> impl Future<Output = u8> {
+    (async move |x: u8| -> u8 {
+        wake_and_yield_once().await;
+        x
+    })(x)
+}
+
+fn async_closure_in_unsafe_block(x: u8) -> impl Future<Output = u8> {
+    (unsafe {
+        async move |x: u8| unsafe_fn(unsafe_async_fn(x).await)
+    })(x)
+}
+
+async unsafe fn unsafe_async_fn(x: u8) -> u8 {
+    wake_and_yield_once().await;
+    x
+}
+
+unsafe fn unsafe_fn(x: u8) -> u8 {
+    x
+}
+
+fn test_future_yields_once_then_returns<F, Fut>(f: F)
+where
+    F: FnOnce(u8) -> Fut,
+    Fut: Future<Output = u8>,
+{
+    let mut fut = Box::pin(f(9));
+    let counter = Arc::new(Counter { wakes: AtomicUsize::new(0) });
+    let waker = ArcWake::into_waker(counter.clone());
+    let mut cx = Context::from_waker(&waker);
+    assert_eq!(0, counter.wakes.load(atomic::Ordering::SeqCst));
+    assert_eq!(Poll::Pending, fut.as_mut().poll(&mut cx));
+    assert_eq!(1, counter.wakes.load(atomic::Ordering::SeqCst));
+    assert_eq!(Poll::Ready(9), fut.as_mut().poll(&mut cx));
+}
+
+fn main() {
+    macro_rules! test {
+        ($($fn_name:expr,)*) => { $(
+            test_future_yields_once_then_returns($fn_name);
+        )* }
+    }
+
+    test! {
+        async_closure,
+        async_closure_in_unsafe_block,
+    }
+}