FlattenUnordered: check waker panic

futures/tests/stream.rs

@@ -1,10 +1,13 @@
+use std::sync::Arc;
+
 use futures::channel::mpsc;
 use futures::executor::block_on;
 use futures::future::{self, Future};
+use futures::lock::Mutex;
 use futures::sink::SinkExt;
 use futures::stream::{self, StreamExt};
 use futures::task::Poll;
-use futures::FutureExt;
+use futures::{ready, FutureExt};
 use futures_test::task::noop_context;
 
 #[test]
@@ -243,6 +246,49 @@ fn flatten_unordered() {
         assert_eq!(fm_unordered, fl_unordered);
         assert_eq!(fm_unordered, (0..60).collect::<Vec<u8>>());
     });
+
+    // waker panics
+    {
+        let stream = Arc::new(Mutex::new(
+            Interchanger { polled: false, base: 0, wake_immediately: false }
+                .take(10)
+                .flat_map_unordered(10, |s| s.map(identity)),
+        ));
+
+        struct PanicWaker;
+
+        impl ArcWake for PanicWaker {
+            fn wake_by_ref(_arc_self: &Arc<Self>) {
+                panic!("WAKE UP");
+            }
+        }
+
+        std::thread::spawn({
+            let stream = stream.clone();
+            move || {
+                let mut st = poll_fn(|cx| {
+                    let mut lock = ready!(stream.lock().poll_unpin(cx));
+
+                    let panic_waker = waker(Arc::new(PanicWaker));
+                    let mut panic_cx = Context::from_waker(&panic_waker);
+                    let data = ready!(lock.poll_next_unpin(&mut panic_cx));
+
+                    Poll::Ready(data)
+                });
+
+                block_on(st.next())
+            }
+        })
+        .join()
+        .unwrap_err();
+
+        block_on(async move {
+            let mut values: Vec<_> = stream.lock().await.by_ref().collect().await;
+            values.sort();
+
+            assert_eq!(values, (0..60).collect::<Vec<u8>>());
+        });
+    }
 }
 
 #[cfg(feature = "executor")] // executor::