Rollup merge of #128882 - RalfJung:local-waker-will-wake, r=cuviper

matthiaskrgr · web-flow · commit 2c88eb9805c1 · 2024-08-11T07:51:52.000+02:00
make LocalWaker::will_wake consistent with Waker::will_wake This mirrors #119863 for `LocalWaker`. Looks like that got missed in the initial `LocalWaker` PR (#118960).
diff --git a/library/core/src/task/wake.rs b/library/core/src/task/wake.rs
@@ -502,6 +502,8 @@ impl Waker {
     #[must_use]
     #[stable(feature = "futures_api", since = "1.36.0")]
     pub fn will_wake(&self, other: &Waker) -> bool {
+        // We optimize this by comparing vtable addresses instead of vtable contents.
+        // This is permitted since the function is documented as best-effort.
         let RawWaker { data: a_data, vtable: a_vtable } = self.waker;
         let RawWaker { data: b_data, vtable: b_vtable } = other.waker;
         a_data == b_data && ptr::eq(a_vtable, b_vtable)
@@ -761,7 +763,11 @@ impl LocalWaker {
     #[must_use]
     #[unstable(feature = "local_waker", issue = "118959")]
     pub fn will_wake(&self, other: &LocalWaker) -> bool {
-        self.waker == other.waker
+        // We optimize this by comparing vtable addresses instead of vtable contents.
+        // This is permitted since the function is documented as best-effort.
+        let RawWaker { data: a_data, vtable: a_vtable } = self.waker;
+        let RawWaker { data: b_data, vtable: b_vtable } = other.waker;
+        a_data == b_data && ptr::eq(a_vtable, b_vtable)
     }
 
     /// Creates a new `LocalWaker` from [`RawWaker`].
