Auto merge of rust-lang#107060 - ibraheemdev:poll-ready, r=joshtriplett

Remove unstable `Poll::ready`

Based on the discussion in rust-lang#89780, this API is problematic and would likely require changes over an edition. Now that `task::ready!` is stabilized, this seems unlikely to happen, so I think we should just go ahead and remove it.

ACP: rust-lang/libs-team#214

Author: bors

library/core/src/future/join.rs

@@ -4,7 +4,7 @@ use crate::cell::UnsafeCell;
 use crate::future::{poll_fn, Future};
 use crate::mem;
 use crate::pin::Pin;
-use crate::task::{Context, Poll};
+use crate::task::{ready, Context, Poll};
 
 /// Polls multiple futures simultaneously, returning a tuple
 /// of all results once complete.
@@ -118,7 +118,7 @@ macro join_internal {
                             fut
                         })
                     };
-                    // Despite how tempting it may be to `let () = fut.poll(cx).ready()?;`
+                    // Despite how tempting it may be to `let () = ready!(fut.poll(cx));`
                     // doing so would defeat the point of `join!`: to start polling eagerly all
                     // of the futures, to allow parallelizing the waits.
                     done &= fut.poll(cx).is_ready();
@@ -180,7 +180,7 @@ impl<F: Future> Future for MaybeDone<F> {
             // Do not mix match ergonomics with unsafe.
             match *self.as_mut().get_unchecked_mut() {
                 MaybeDone::Future(ref mut f) => {
-                    let val = Pin::new_unchecked(f).poll(cx).ready()?;
+                    let val = ready!(Pin::new_unchecked(f).poll(cx));
                     self.set(Self::Done(val));
                 }
                 MaybeDone::Done(_) => {}

library/core/src/task/mod.rs

@@ -13,5 +13,3 @@ pub use self::wake::{Context, RawWaker, RawWakerVTable, Waker};
 mod ready;
 #[stable(feature = "ready_macro", since = "1.64.0")]
 pub use ready::ready;
-#[unstable(feature = "poll_ready", issue = "89780")]
-pub use ready::Ready;

library/core/src/task/poll.rs

@@ -3,7 +3,6 @@
 use crate::convert;
 use crate::ops::{self, ControlFlow};
 use crate::result::Result;
-use crate::task::Ready;
 
 /// Indicates whether a value is available or if the current task has been
 /// scheduled to receive a wakeup instead.
@@ -95,38 +94,6 @@ impl<T> Poll<T> {
     pub const fn is_pending(&self) -> bool {
         !self.is_ready()
     }
-
-    /// Extracts the successful type of a [`Poll<T>`].
-    ///
-    /// When combined with the `?` operator, this function will
-    /// propagate any [`Poll::Pending`] values to the caller, and
-    /// extract the `T` from [`Poll::Ready`].
-    ///
-    /// # Examples
-    ///
-    /// ```rust
-    /// #![feature(poll_ready)]
-    ///
-    /// use std::task::{Context, Poll};
-    /// use std::future::{self, Future};
-    /// use std::pin::Pin;
-    ///
-    /// pub fn do_poll(cx: &mut Context<'_>) -> Poll<()> {
-    ///     let mut fut = future::ready(42);
-    ///     let fut = Pin::new(&mut fut);
-    ///
-    ///     let num = fut.poll(cx).ready()?;
-    ///     # let _ = num; // to silence unused warning
-    ///     // ... use num
-    ///
-    ///     Poll::Ready(())
-    /// }
-    /// ```
-    #[inline]
-    #[unstable(feature = "poll_ready", issue = "89780")]
-    pub fn ready(self) -> Ready<T> {
-        Ready(self)
-    }
 }
 
 impl<T, E> Poll<Result<T, E>> {

library/core/src/task/ready.rs

@@ -1,8 +1,3 @@
-use core::convert;
-use core::fmt;
-use core::ops::{ControlFlow, FromResidual, Try};
-use core::task::Poll;
-
 /// Extracts the successful type of a [`Poll<T>`].
 ///
 /// This macro bakes in propagation of [`Pending`] signals by returning early.
@@ -60,55 +55,3 @@ pub macro ready($e:expr) {
         }
     }
 }
-
-/// Extracts the successful type of a [`Poll<T>`].
-///
-/// See [`Poll::ready`] for details.
-#[unstable(feature = "poll_ready", issue = "89780")]
-pub struct Ready<T>(pub(crate) Poll<T>);
-
-#[unstable(feature = "poll_ready", issue = "89780")]
-impl<T> Try for Ready<T> {
-    type Output = T;
-    type Residual = Ready<convert::Infallible>;
-
-    #[inline]
-    fn from_output(output: Self::Output) -> Self {
-        Ready(Poll::Ready(output))
-    }
-
-    #[inline]
-    fn branch(self) -> ControlFlow<Self::Residual, Self::Output> {
-        match self.0 {
-            Poll::Ready(v) => ControlFlow::Continue(v),
-            Poll::Pending => ControlFlow::Break(Ready(Poll::Pending)),
-        }
-    }
-}
-
-#[unstable(feature = "poll_ready", issue = "89780")]
-impl<T> FromResidual for Ready<T> {
-    #[inline]
-    fn from_residual(residual: Ready<convert::Infallible>) -> Self {
-        match residual.0 {
-            Poll::Pending => Ready(Poll::Pending),
-        }
-    }
-}
-
-#[unstable(feature = "poll_ready", issue = "89780")]
-impl<T> FromResidual<Ready<convert::Infallible>> for Poll<T> {
-    #[inline]
-    fn from_residual(residual: Ready<convert::Infallible>) -> Self {
-        match residual.0 {
-            Poll::Pending => Poll::Pending,
-        }
-    }
-}
-
-#[unstable(feature = "poll_ready", issue = "89780")]
-impl<T> fmt::Debug for Ready<T> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.debug_tuple("Ready").finish()
-    }
-}