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    use crate::io::{AsyncBufRead, AsyncRead, ReadBuf};

    use std::fmt;
    use std::io;
    use std::pin::Pin;
    use std::task::{Context, Poll};

    cfg_io_util! {
        /// An async reader which is always at EOF.
        ///
        /// This struct is generally created by calling [`empty`]. Please see
        /// the documentation of [`empty()`][`empty`] for more details.
        ///
        /// This is an asynchronous version of [`std::io::empty`][std].
        ///
        /// [`empty`]: fn@empty
        /// [std]: std::io::empty
        pub struct Empty {
            _p: (),
        }

        /// Creates a new empty async reader.
        ///
        /// All reads from the returned reader will return `Poll::Ready(Ok(0))`.
        ///
        /// This is an asynchronous version of [`std::io::empty`][std].
        ///
        /// [std]: std::io::empty
        ///
        /// # Examples
        ///
        /// A slightly sad example of not reading anything into a buffer:
        ///
        /// ```
        /// use tokio::io::{self, AsyncReadExt};
        ///
        /// #[tokio::main]
        /// async fn main() {
        ///     let mut buffer = String::new();
        ///     io::empty().read_to_string(&mut buffer).await.unwrap();
        ///     assert!(buffer.is_empty());
        /// }
        /// ```
        pub fn empty() -> Empty {
            Empty { _p: () }
        }
    }

    impl AsyncRead for Empty {
        #[inline]
        fn poll_read(
            self: Pin<&mut Self>,
            _: &mut Context<'_>,
            _: &mut ReadBuf<'_>,
        ) -> Poll<io::Result<()>> {
            Poll::Ready(Ok(()))
        }
    }

    impl AsyncBufRead for Empty {
        #[inline]
        fn poll_fill_buf(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<io::Result<&[u8]>> {
            Poll::Ready(Ok(&[]))
        }

        #[inline]
        fn consume(self: Pin<&mut Self>, _: usize) {}
    }

    impl fmt::Debug for Empty {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            f.pad("Empty { .. }")
        }
    }

    #[cfg(test)]
    mod tests {
        use super::*;

        #[test]
        fn assert_unpin() {
            crate::is_unpin::<Empty>();
        }
    }