Fix Sync impl of BiLockGuard

futures-executor/src/thread_pool.rs

@@ -346,9 +346,8 @@ impl fmt::Debug for Task {
 
 impl ArcWake for WakeHandle {
     fn wake_by_ref(arc_self: &Arc<Self>) {
-        match arc_self.mutex.notify() {
-            Ok(task) => arc_self.exec.state.send(Message::Run(task)),
-            Err(()) => {}
+        if let Ok(task) = arc_self.mutex.notify() {
+            arc_self.exec.state.send(Message::Run(task))
         }
     }
 }

futures-util/src/lock/bilock.rs

@@ -224,6 +224,9 @@ pub struct BiLockGuard<'a, T> {
     bilock: &'a BiLock<T>,
 }
 
+// We allow parallel access to T via Deref, so Sync bound is also needed here.
+unsafe impl<T: Send + Sync> Sync for BiLockGuard<'_, T> {}
+
 impl<T> Deref for BiLockGuard<'_, T> {
     type Target = T;
     fn deref(&self) -> &T {

futures/tests/no-std/src/lib.rs

@@ -1,6 +1,5 @@
 #![cfg(nightly)]
 #![no_std]
-#![feature(cfg_target_has_atomic)]
 
 #[cfg(feature = "futures-core-alloc")]
 #[cfg(target_has_atomic = "ptr")]