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    use crate::io::AsyncSeek;

    use pin_project_lite::pin_project;
    use std::future::Future;
    use std::io::{self, SeekFrom};
    use std::marker::PhantomPinned;
    use std::pin::Pin;
    use std::task::{Context, Poll};

    pin_project! {
        /// Future for the [`seek`](crate::io::AsyncSeekExt::seek) method.
        #[derive(Debug)]
        #[must_use = "futures do nothing unless you `.await` or poll them"]
        pub struct Seek<'a, S: ?Sized> {
            seek: &'a mut S,
            pos: Option<SeekFrom>,
            // Make this future `!Unpin` for compatibility with async trait methods.
            #[pin]
            _pin: PhantomPinned,
        }
    }

    pub(crate) fn seek<S>(seek: &mut S, pos: SeekFrom) -> Seek<'_, S>
    where
        S: AsyncSeek + ?Sized + Unpin,
    {
        Seek {
            seek,
            pos: Some(pos),
            _pin: PhantomPinned,
        }
    }

    impl<S> Future for Seek<'_, S>
    where
        S: AsyncSeek + ?Sized + Unpin,
    {
        type Output = io::Result<u64>;

        fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
            let me = self.project();
            match me.pos {
                Some(pos) => {
                    // ensure no seek in progress
                    ready!(Pin::new(&mut *me.seek).poll_complete(cx))?;
                    match Pin::new(&mut *me.seek).start_seek(*pos) {
                        Ok(()) => {
                            *me.pos = None;
                            Pin::new(&mut *me.seek).poll_complete(cx)
                        }
                        Err(e) => Poll::Ready(Err(e)),
                    }
                }
                None => Pin::new(&mut *me.seek).poll_complete(cx),
            }
        }
    }