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    use core::pin::Pin;
    use core::usize;
    use futures_core::ready;
    use futures_core::stream::{FusedStream, Stream};
    use futures_core::task::{Context, Poll};
    use pin_project_lite::pin_project;

    pin_project! {
        /// Stream for the [`cycle`](super::StreamExt::cycle) method.
        #[derive(Debug)]
        #[must_use = "streams do nothing unless polled"]
        pub struct Cycle<St> {
            orig: St,
            #[pin]
            stream: St,
        }
    }

    impl<St> Cycle<St>
    where
        St: Clone + Stream,
    {
        pub(super) fn new(stream: St) -> Self {
            Self {
                orig: stream.clone(),
                stream,
            }
        }
    }

    impl<St> Stream for Cycle<St>
    where
        St: Clone + Stream,
    {
        type Item = St::Item;

        fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
            let mut this = self.project();

            match ready!(this.stream.as_mut().poll_next(cx)) {
                None => {
                    this.stream.set(this.orig.clone());
                    this.stream.poll_next(cx)
                }
                item => Poll::Ready(item),
            }
        }

        fn size_hint(&self) -> (usize, Option<usize>) {
            // the cycle stream is either empty or infinite
            match self.orig.size_hint() {
                size @ (0, Some(0)) => size,
                (0, _) => (0, None),
                _ => (usize::max_value(), None),
            }
        }
    }

    impl<St> FusedStream for Cycle<St>
    where
        St: Clone + Stream,
    {
        fn is_terminated(&self) -> bool {
            // the cycle stream is either empty or infinite
            if let (0, Some(0)) = self.size_hint() {
                true
            } else {
                false
            }
        }
    }