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use futures_core::future::Future;
use futures_core::stream::TryStream;
use futures_core::task::{LocalWaker, Poll};
use core::marker::Unpin;
use core::pin::Pin;
#[derive(Debug)]
#[must_use = "streams do nothing unless polled"]
pub struct TryNext<'a, St: Unpin + 'a> {
stream: &'a mut St,
}
impl<St: Unpin> Unpin for TryNext<'_, St> {}
impl<'a, St: TryStream + Unpin> TryNext<'a, St> {
pub(super) fn new(stream: &'a mut St) -> Self {
TryNext { stream }
}
}
impl<St: TryStream + Unpin> Future for TryNext<'_, St> {
type Output = Result<Option<St::Ok>, St::Error>;
fn poll(
mut self: Pin<&mut Self>,
lw: &LocalWaker,
) -> Poll<Self::Output> {
match Pin::new(&mut *self.stream).try_poll_next(lw) {
Poll::Ready(Some(Ok(x))) => Poll::Ready(Ok(Some(x))),
Poll::Ready(Some(Err(e))) => Poll::Ready(Err(e)),
Poll::Ready(None) => Poll::Ready(Ok(None)),
Poll::Pending => Poll::Pending,
}
}
}