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 [`next`](super::StreamExt::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 Next<'a, St: ?Sized> { stream: &'a mut St, // Make this future `!Unpin` for compatibility with async trait methods. #[pin] _pin: PhantomPinned, } } impl<'a, St: ?Sized> Next<'a, St> { pub(super) fn new(stream: &'a mut St) -> Self { Next { stream, _pin: PhantomPinned, } } } impl Future for Next<'_, St> { type Output = Option; fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll { let me = self.project(); Pin::new(me.stream).poll_next(cx) } }