Attempting to fix Miri

Author: olegnn

futures/tests/stream.rs

@@ -299,13 +299,14 @@ fn flatten_unordered() {
 
     // stream panics
     {
-        let st = once(async { once(async { panic!("Polled") }).boxed() }.boxed()).chain(
-            Interchanger { polled: false, base: 0, wake_immediately: true }
-                .then(|val| async move { val.boxed() }.boxed())
-                .take(10),
-        );
+        let st = once(async { once(Box::pin(async { panic!("Polled") })).left_stream() }.boxed())
+            .chain(
+                Interchanger { polled: false, base: 0, wake_immediately: true }
+                    .then(|val| async move { val.right_stream() }.boxed())
+                    .take(10),
+            );
 
-        let stream = Arc::new(Mutex::new(st.boxed().flat_map_unordered(10, |s| s.map(identity))));
+        let stream = Arc::new(Mutex::new(st.flat_map_unordered(10, |s| s.map(identity))));
 
         std::thread::spawn({
             let stream = stream.clone();