diff options
| -rw-r--r-- | library/core/src/task/wake.rs | 17 |
1 files changed, 12 insertions, 5 deletions
diff --git a/library/core/src/task/wake.rs b/library/core/src/task/wake.rs index 9c41b8b4f46..077852b0120 100644 --- a/library/core/src/task/wake.rs +++ b/library/core/src/task/wake.rs @@ -329,12 +329,14 @@ impl Waker { Waker { waker } } - /// Creates a new `Waker` that does nothing when `wake` is called. + /// Returns a reference to a `Waker` that does nothing when used. /// /// This is mostly useful for writing tests that need a [`Context`] to poll /// some futures, but are not expecting those futures to wake the waker or /// do not need to do anything specific if it happens. /// + /// If an owned `Waker` is needed, `clone()` this one. + /// /// # Examples /// /// ``` @@ -343,8 +345,7 @@ impl Waker { /// use std::future::Future; /// use std::task; /// - /// let waker = task::Waker::noop(); - /// let mut cx = task::Context::from_waker(&waker); + /// let mut cx = task::Context::from_waker(task::Waker::noop()); /// /// let mut future = Box::pin(async { 10 }); /// assert_eq!(future.as_mut().poll(&mut cx), task::Poll::Ready(10)); @@ -352,7 +353,12 @@ impl Waker { #[inline] #[must_use] #[unstable(feature = "noop_waker", issue = "98286")] - pub const fn noop() -> Waker { + pub const fn noop() -> &'static Waker { + // Ideally all this data would be explicitly `static` because it is used by reference and + // only ever needs one copy. But `const fn`s (and `const` items) cannot refer to statics, + // even though their values can be promoted to static. (That might change; see #119618.) + // An alternative would be a `pub static NOOP: &Waker`, but associated static items are not + // currently allowed either, and making it non-associated would be unergonomic. const VTABLE: RawWakerVTable = RawWakerVTable::new( // Cloning just returns a new no-op raw waker |_| RAW, @@ -364,8 +370,9 @@ impl Waker { |_| {}, ); const RAW: RawWaker = RawWaker::new(ptr::null(), &VTABLE); + const WAKER_REF: &Waker = &Waker { waker: RAW }; - Waker { waker: RAW } + WAKER_REF } /// Get a reference to the underlying [`RawWaker`]. |