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    use core::fmt;
    use core::pin::Pin;
    use futures_core::future::{TryFuture};
    use futures_core::ready;
    use futures_core::stream::{Stream, TryStream, FusedStream};
    use futures_core::task::{Context, Poll};
    #[cfg(feature = "sink")]
    use futures_sink::Sink;
    use pin_project_lite::pin_project;

    pin_project! {
        /// Stream for the [`try_filter_map`](super::TryStreamExt::try_filter_map)
        /// method.
        #[must_use = "streams do nothing unless polled"]
        pub struct TryFilterMap<St, Fut, F> {
            #[pin]
            stream: St,
            f: F,
            #[pin]
            pending: Option<Fut>,
        }
    }

    impl<St, Fut, F> fmt::Debug for TryFilterMap<St, Fut, F>
    where
        St: fmt::Debug,
        Fut: fmt::Debug,
    {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            f.debug_struct("TryFilterMap")
                .field("stream", &self.stream)
                .field("pending", &self.pending)
                .finish()
        }
    }

    impl<St, Fut, F> TryFilterMap<St, Fut, F> {
        pub(super) fn new(stream: St, f: F) -> Self {
            Self { stream, f, pending: None }
        }

        delegate_access_inner!(stream, St, ());
    }

    impl<St, Fut, F, T> FusedStream for TryFilterMap<St, Fut, F>
        where St: TryStream + FusedStream,
              Fut: TryFuture<Ok = Option<T>, Error = St::Error>,
              F: FnMut(St::Ok) -> Fut,
    {
        fn is_terminated(&self) -> bool {
            self.pending.is_none() && self.stream.is_terminated()
        }
    }

    impl<St, Fut, F, T> Stream for TryFilterMap<St, Fut, F>
        where St: TryStream,
              Fut: TryFuture<Ok = Option<T>, Error = St::Error>,
              F: FnMut(St::Ok) -> Fut,
    {
        type Item = Result<T, St::Error>;

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

            Poll::Ready(loop {
                if let Some(p) = this.pending.as_mut().as_pin_mut() {
                    // We have an item in progress, poll that until it's done
                    let res = ready!(p.try_poll(cx));
                    this.pending.set(None);
                    let item = res?;
                    if item.is_some() {
                        break item.map(Ok);
                    }
                } else if let Some(item) = ready!(this.stream.as_mut().try_poll_next(cx)?) {
                    // No item in progress, but the stream is still going
                    this.pending.set(Some((this.f)(item)));
                } else {
                    // The stream is done
                    break None;
                }
            })
        }

        fn size_hint(&self) -> (usize, Option<usize>) {
            let pending_len = if self.pending.is_some() { 1 } else { 0 };
            let (_, upper) = self.stream.size_hint();
            let upper = match upper {
                Some(x) => x.checked_add(pending_len),
                None => None,
            };
            (0, upper) // can't know a lower bound, due to the predicate
        }
    }

    // Forwarding impl of Sink from the underlying stream
    #[cfg(feature = "sink")]
    impl<S, Fut, F, Item> Sink<Item> for TryFilterMap<S, Fut, F>
        where S: Sink<Item>,
    {
        type Error = S::Error;

        delegate_sink!(stream, Item);
    }