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use super::assert_stream;
use core::fmt;
use core::pin::Pin;
use futures_core::stream::Stream;
use futures_core::task::{Context, Poll};
#[must_use = "streams do nothing unless polled"]
pub 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()
}
}
pub fn poll_fn<T, F>(f: F) -> PollFn<F>
where
F: FnMut(&mut Context<'_>) -> Poll<Option<T>>,
{
assert_stream::<T, _>(PollFn { f })
}
impl<T, F> Stream for PollFn<F>
where
F: FnMut(&mut Context<'_>) -> Poll<Option<T>>,
{
type Item = T;
fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<T>> {
(&mut self.f)(cx)
}
}