async-watch2 0.1.0

Async watch channel
Documentation 
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//! `PollFn` extracted from unstable rust-std implementation.

use std::fmt;
use std::future::Future;
use std::pin::Pin;
use std::task::{Context, Poll};

/// Creates a future that wraps a function returning `Poll`.
///
/// Polling the future delegates to the wrapped function.
pub(crate) fn poll_fn<T, F>(f: F) -> PollFn<F>
where
    F: FnMut(&mut Context<'_>) -> Poll<T>,
{
    PollFn { f }
}

/// A Future that wraps a function returning `Poll`.
#[must_use = "futures do nothing unless you `.await` or poll them"]
pub(crate) struct PollFn<F> {
    f: F,
}

impl<F> Unpin for PollFn<F> {}

impl<F> fmt::Debug for PollFn<F> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("PollFn").finish()
    }
}

impl<T, F> Future for PollFn<F>
where
    F: FnMut(&mut Context<'_>) -> Poll<T>,
{
    type Output = T;

    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<T> {
        (&mut self.f)(cx)
    }
}