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/// Extracts the successful type of a [`Poll<T>`].
///
/// This macro bakes in propagation of [`Pending`] signals by returning early.
///
/// [`Poll<T>`]: crate::task::Poll
/// [`Pending`]: crate::task::Poll::Pending
///
/// # Examples
///
/// ```
/// use std::task::{ready, 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 = ready!(fut.poll(cx));
/// # let _ = num;
/// // ... use num
///
/// Poll::Ready(())
/// }
/// ```
///
/// The `ready!` call expands to:
///
/// ```
/// # 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 = match fut.poll(cx) {
/// Poll::Ready(t) => t,
/// Poll::Pending => return Poll::Pending,
/// };
/// # let _ = num; // to silence unused warning
/// # // ... use num
/// #
/// # Poll::Ready(())
/// # }
/// ```
#[stable(feature = "ready_macro", since = "1.64.0")]
#[rustc_macro_transparency = "semitransparent"]
pub macro ready($e:expr) {
match $e {
$crate::task::Poll::Ready(t) => t,
$crate::task::Poll::Pending => {
return $crate::task::Poll::Pending;
}
}
}