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use crate::stream_ext::Next;
use crate::Stream;
use core::future::Future;
use core::marker::PhantomPinned;
use core::pin::Pin;
use core::task::{Context, Poll};
use pin_project_lite::pin_project;
pin_project! {
/// Future for the [`try_next`](super::StreamExt::try_next) method.
///
/// # Cancel safety
///
/// This method is cancel safe. It only
/// holds onto a reference to the underlying stream,
/// so dropping it will never lose a value.
#[derive(Debug)]
#[must_use = "futures do nothing unless you `.await` or poll them"]
pub struct TryNext<'a, St: ?Sized> {
#[pin]
inner: Next<'a, St>,
// Make this future `!Unpin` for compatibility with async trait methods.
#[pin]
_pin: PhantomPinned,
}
}
impl<'a, St: ?Sized> TryNext<'a, St> {
pub(super) fn new(stream: &'a mut St) -> Self {
Self {
inner: Next::new(stream),
_pin: PhantomPinned,
}
}
}
impl<T, E, St: ?Sized + Stream<Item = Result<T, E>> + Unpin> Future for TryNext<'_, St> {
type Output = Result<Option<T>, E>;
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
let me = self.project();
me.inner.poll(cx).map(Option::transpose)
}
}