Rollup merge of rust-lang#76227 - CDirkx:const-poll, r=KodrAus

Stabilize `Poll::is_ready` and `is_pending` as const

Insta-stabilize the methods `is_ready` and `is_pending` of `std::task::Poll` as const, in the same way as [PR#76198](rust-lang#76198).

Possible because of the recent stabilization of const control flow.

Part of rust-lang#76225.

library/core/src/task/poll.rs

@@ -39,15 +39,17 @@ impl<T> Poll<T> {
 
     /// Returns `true` if this is `Poll::Ready`
     #[inline]
+    #[rustc_const_stable(feature = "const_poll", since = "1.49.0")]
     #[stable(feature = "futures_api", since = "1.36.0")]
-    pub fn is_ready(&self) -> bool {
+    pub const fn is_ready(&self) -> bool {
         matches!(*self, Poll::Ready(_))
     }
 
     /// Returns `true` if this is `Poll::Pending`
     #[inline]
+    #[rustc_const_stable(feature = "const_poll", since = "1.49.0")]
     #[stable(feature = "futures_api", since = "1.36.0")]
-    pub fn is_pending(&self) -> bool {
+    pub const fn is_pending(&self) -> bool {
         !self.is_ready()
     }
 }

library/core/tests/lib.rs

@@ -91,5 +91,6 @@ mod result;
 mod slice;
 mod str;
 mod str_lossy;
+mod task;
 mod time;
 mod tuple;

library/core/tests/task.rs

@@ -0,0 +1,14 @@
+use core::task::Poll;
+
+#[test]
+fn poll_const() {
+    // test that the methods of `Poll` are usable in a const context
+
+    const POLL: Poll<usize> = Poll::Pending;
+
+    const IS_READY: bool = POLL.is_ready();
+    assert!(!IS_READY);
+
+    const IS_PENDING: bool = POLL.is_pending();
+    assert!(IS_PENDING);
+}