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    #![cfg(feature = "with-deprecated")]
    #![deprecated(since = "0.1.4", note = "use sync::mpsc::channel instead")]
    #![allow(deprecated)]

    use std::any::Any;
    use std::error::Error;
    use std::fmt;

    use {Poll, Async, Stream, Future, Sink};
    use sink::Send;
    use sync::mpsc;

    /// Creates an in-memory channel implementation of the `Stream` trait.
    ///
    /// This method creates a concrete implementation of the `Stream` trait which
    /// can be used to send values across threads in a streaming fashion. This
    /// channel is unique in that it implements back pressure to ensure that the
    /// sender never outpaces the receiver. The `Sender::send` method will only
    /// allow sending one message and the next message can only be sent once the
    /// first was consumed.
    ///
    /// The `Receiver` returned implements the `Stream` trait and has access to any
    /// number of the associated combinators for transforming the result.
    pub fn channel<T, E>() -> (Sender<T, E>, Receiver<T, E>) {
        let (tx, rx) = mpsc::channel(0);
        (Sender { inner: tx }, Receiver { inner: rx })
    }

    /// The transmission end of a channel which is used to send values.
    ///
    /// This is created by the `channel` method in the `stream` module.
    #[derive(Debug)]
    pub struct Sender<T, E> {
        inner: mpsc::Sender<Result<T, E>>,
    }

    /// The receiving end of a channel which implements the `Stream` trait.
    ///
    /// This is a concrete implementation of a stream which can be used to represent
    /// a stream of values being computed elsewhere. This is created by the
    /// `channel` method in the `stream` module.
    #[must_use = "streams do nothing unless polled"]
    #[derive(Debug)]
    pub struct Receiver<T, E> {
        inner: mpsc::Receiver<Result<T, E>>,
    }

    /// Error type for sending, used when the receiving end of the channel is dropped
    pub struct SendError<T, E>(Result<T, E>);

    /// Future returned by `Sender::send`.
    #[derive(Debug)]
    pub struct FutureSender<T, E> {
        inner: Send<mpsc::Sender<Result<T, E>>>,
    }

    impl<T, E> fmt::Debug for SendError<T, E> {
        fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
            fmt.debug_tuple("SendError")
                .field(&"...")
                .finish()
        }
    }

    impl<T, E> fmt::Display for SendError<T, E> {
        fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
            write!(fmt, "send failed because receiver is gone")
        }
    }

    impl<T, E> Error for SendError<T, E>
        where T: Any, E: Any
    {
        fn description(&self) -> &str {
            "send failed because receiver is gone"
        }
    }

    impl<T, E> Stream for Receiver<T, E> {
        type Item = T;
        type Error = E;

        fn poll(&mut self) -> Poll<Option<T>, E> {
            match self.inner.poll().expect("cannot fail") {
                Async::Ready(Some(Ok(e))) => Ok(Async::Ready(Some(e))),
                Async::Ready(Some(Err(e))) => Err(e),
                Async::Ready(None) => Ok(Async::Ready(None)),
                Async::NotReady => Ok(Async::NotReady),
            }
        }
    }

    impl<T, E> Sender<T, E> {
        /// Sends a new value along this channel to the receiver.
        ///
        /// This method consumes the sender and returns a future which will resolve
        /// to the sender again when the value sent has been consumed.
        pub fn send(self, t: Result<T, E>) -> FutureSender<T, E> {
            FutureSender { inner: self.inner.send(t) }
        }
    }

    impl<T, E> Future for FutureSender<T, E> {
        type Item = Sender<T, E>;
        type Error = SendError<T, E>;

        fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
            match self.inner.poll() {
                Ok(a) => Ok(a.map(|a| Sender { inner: a })),
                Err(e) => Err(SendError(e.into_inner())),
            }
        }
    }

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