1/// Extracts the successful type of a [`Poll<T>`].
2///
3/// This macro bakes in propagation of [`Pending`] signals by returning early.
4///
5/// [`Poll<T>`]: crate::task::Poll
6/// [`Pending`]: crate::task::Poll::Pending
7///
8/// # Examples
9///
10/// ```
11/// use std::task::{ready, Context, Poll};
12/// use std::future::{self, Future};
13/// use std::pin::Pin;
14///
15/// pub fn do_poll(cx: &mut Context<'_>) -> Poll<()> {
16/// let mut fut = future::ready(42);
17/// let fut = Pin::new(&mut fut);
18///
19/// let num = ready!(fut.poll(cx));
20/// # let _ = num;
21/// // ... use num
22///
23/// Poll::Ready(())
24/// }
25/// ```
26///
27/// The `ready!` call expands to:
28///
29/// ```
30/// # use std::task::{Context, Poll};
31/// # use std::future::{self, Future};
32/// # use std::pin::Pin;
33/// #
34/// # pub fn do_poll(cx: &mut Context<'_>) -> Poll<()> {
35/// # let mut fut = future::ready(42);
36/// # let fut = Pin::new(&mut fut);
37/// #
38/// let num = match fut.poll(cx) {
39/// Poll::Ready(t) => t,
40/// Poll::Pending => return Poll::Pending,
41/// };
42/// # let _ = num; // to silence unused warning
43/// # // ... use num
44/// #
45/// # Poll::Ready(())
46/// # }
47/// ```
48#[stable(feature = "ready_macro", since = "1.64.0")]
49#[rustc_macro_transparency = "semitransparent"]
50pub macro ready($e:expr) {
51 match $e {
52 $crate::task::Poll::Ready(t) => t,
53 $crate::task::Poll::Pending => {
54 return $crate::task::Poll::Pending;
55 }
56 }
57}
58