futures_util/async_await/
poll.rs

1use crate::future::FutureExt;
2use core::pin::Pin;
3use futures_core::future::Future;
4use futures_core::task::{Context, Poll};
5
6/// A macro which returns the result of polling a future once within the
7/// current `async` context.
8///
9/// This macro is only usable inside of `async` functions, closures, and blocks.
10/// It is also gated behind the `async-await` feature of this library, which is
11/// activated by default.
12///
13/// If you need the result of polling a [`Stream`](crate::stream::Stream),
14/// you can use this macro with the [`next`](crate::stream::StreamExt::next) method:
15/// `poll!(stream.next())`.
16#[macro_export]
17macro_rules! poll {
18    ($x:expr $(,)?) => {
19        $crate::__private::async_await::poll($x).await
20    };
21}
22
23#[doc(hidden)]
24pub fn poll<F: Future + Unpin>(future: F) -> PollOnce<F> {
25    PollOnce { future }
26}
27
28#[allow(missing_debug_implementations)]
29#[doc(hidden)]
30pub struct PollOnce<F: Future + Unpin> {
31    future: F,
32}
33
34impl<F: Future + Unpin> Future for PollOnce<F> {
35    type Output = Poll<F::Output>;
36    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
37        Poll::Ready(self.future.poll_unpin(cx))
38    }
39}
futures_util/async_await/poll.rs

futures_util/async_await/
poll.rs
