library/std/src/sync/oneshot.rs - rust-lang/rust - Git at Google

 //! A single-producer, single-consumer (oneshot) channel.
 //!
 //! This is an experimental module, so the API will likely change.

 use crate::sync::mpmc;
 use crate::sync::mpsc::{RecvError, SendError};
 use crate::time::{Duration, Instant};
 use crate::{error, fmt};

 /// Creates a new oneshot channel, returning the sender/receiver halves.
 ///
 /// # Examples
 ///
 /// ```
 /// #![feature(oneshot_channel)]
 /// use std::sync::oneshot;
 /// use std::thread;
 ///
 /// let (sender, receiver) = oneshot::channel();
 ///
 /// // Spawn off an expensive computation.
 /// thread::spawn(move || {
 /// #   fn expensive_computation() -> i32 { 42 }
 ///     sender.send(expensive_computation()).unwrap();
 ///     // `sender` is consumed by `send`, so we cannot use it anymore.
 /// });
 ///
 /// # fn do_other_work() -> i32 { 42 }
 /// do_other_work();
 ///
 /// // Let's see what that answer was...
 /// println!("{:?}", receiver.recv().unwrap());
 /// // `receiver` is consumed by `recv`, so we cannot use it anymore.
 /// ```
 #[must_use]
 #[unstable(feature = "oneshot_channel", issue = "143674")]
 pub fn channel<T>() -> (Sender<T>, Receiver<T>) {
     // Using a `sync_channel` with capacity 1 means that the internal implementation will use the
     // `Array`-flavored channel implementation.
     let (sender, receiver) = mpmc::sync_channel(1);
     (Sender { inner: sender }, Receiver { inner: receiver })
 }

 ////////////////////////////////////////////////////////////////////////////////////////////////////
 // Sender
 ////////////////////////////////////////////////////////////////////////////////////////////////////

 /// The sending half of a oneshot channel.
 ///
 /// # Examples
 ///
 /// ```
 /// #![feature(oneshot_channel)]
 /// use std::sync::oneshot;
 /// use std::thread;
 ///
 /// let (sender, receiver) = oneshot::channel();
 ///
 /// thread::spawn(move || {
 ///     sender.send("Hello from thread!").unwrap();
 /// });
 ///
 /// assert_eq!(receiver.recv().unwrap(), "Hello from thread!");
 /// ```
 ///
 /// `Sender` cannot be sent between threads if it is sending non-`Send` types.
 ///
 /// ```compile_fail
 /// #![feature(oneshot_channel)]
 /// use std::sync::oneshot;
 /// use std::thread;
 /// use std::ptr;
 ///
 /// let (sender, receiver) = oneshot::channel();
 ///
 /// struct NotSend(*mut ());
 /// thread::spawn(move || {
 ///     sender.send(NotSend(ptr::null_mut()));
 /// });
 ///
 /// let reply = receiver.try_recv().unwrap();
 /// ```
 #[unstable(feature = "oneshot_channel", issue = "143674")]
 pub struct Sender<T> {
     /// The `oneshot` channel is simply a wrapper around a `mpmc` channel.
     inner: mpmc::Sender<T>,
 }

 // SAFETY: Since the only methods in which synchronization must occur take full ownership of the
 // [`Sender`], it is perfectly safe to share a `&Sender` between threads (as it is effectively
 // useless without ownership).
 #[unstable(feature = "oneshot_channel", issue = "143674")]
 unsafe impl<T> Sync for Sender<T> {}

 impl<T> Sender<T> {
     /// Attempts to send a value through this channel. This can only fail if the corresponding
     /// [`Receiver<T>`] has been dropped.
     ///
     /// This method is non-blocking (wait-free).
     ///
     /// # Examples
     ///
     /// ```
     /// #![feature(oneshot_channel)]
     /// use std::sync::oneshot;
     /// use std::thread;
     ///
     /// let (tx, rx) = oneshot::channel();
     ///
     /// thread::spawn(move || {
     ///     // Perform some computation.
     ///     let result = 2 + 2;
     ///     tx.send(result).unwrap();
     /// });
     ///
     /// assert_eq!(rx.recv().unwrap(), 4);
     /// ```
     #[unstable(feature = "oneshot_channel", issue = "143674")]
     pub fn send(self, t: T) -> Result<(), SendError<T>> {
         self.inner.send(t)
     }
 }

 #[unstable(feature = "oneshot_channel", issue = "143674")]
 impl<T> fmt::Debug for Sender<T> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_struct("Sender").finish_non_exhaustive()
     }
 }

 ////////////////////////////////////////////////////////////////////////////////////////////////////
 // Receiver
 ////////////////////////////////////////////////////////////////////////////////////////////////////

 /// The receiving half of a oneshot channel.
 ///
 /// # Examples
 ///
 /// ```
 /// #![feature(oneshot_channel)]
 /// use std::sync::oneshot;
 /// use std::thread;
 /// use std::time::Duration;
 ///
 /// let (sender, receiver) = oneshot::channel();
 ///
 /// thread::spawn(move || {
 ///     thread::sleep(Duration::from_millis(100));
 ///     sender.send("Hello after delay!").unwrap();
 /// });
 ///
 /// println!("Waiting for message...");
 /// println!("{}", receiver.recv().unwrap());
 /// ```
 ///
 /// `Receiver` cannot be sent between threads if it is receiving non-`Send` types.
 ///
 /// ```compile_fail
 /// # #![feature(oneshot_channel)]
 /// # use std::sync::oneshot;
 /// # use std::thread;
 /// # use std::ptr;
 /// #
 /// let (sender, receiver) = oneshot::channel();
 ///
 /// struct NotSend(*mut ());
 /// sender.send(NotSend(ptr::null_mut()));
 ///
 /// thread::spawn(move || {
 ///     let reply = receiver.try_recv().unwrap();
 /// });
 /// ```
 #[unstable(feature = "oneshot_channel", issue = "143674")]
 pub struct Receiver<T> {
     /// The `oneshot` channel is simply a wrapper around a `mpmc` channel.
     inner: mpmc::Receiver<T>,
 }

 // SAFETY: Since the only methods in which synchronization must occur take full ownership of the
 // [`Receiver`], it is perfectly safe to share a `&Receiver` between threads (as it is unable to
 // receive any values without ownership).
 #[unstable(feature = "oneshot_channel", issue = "143674")]
 unsafe impl<T> Sync for Receiver<T> {}

 impl<T> Receiver<T> {
     /// Receives the value from the sending end, blocking the calling thread until it gets it.
     ///
     /// Can only fail if the corresponding [`Sender<T>`] has been dropped.
     ///
     /// # Examples
     ///
     /// ```
     /// #![feature(oneshot_channel)]
     /// use std::sync::oneshot;
     /// use std::thread;
     /// use std::time::Duration;
     ///
     /// let (tx, rx) = oneshot::channel();
     ///
     /// thread::spawn(move || {
     ///     thread::sleep(Duration::from_millis(500));
     ///     tx.send("Done!").unwrap();
     /// });
     ///
     /// // This will block until the message arrives.
     /// println!("{}", rx.recv().unwrap());
     /// ```
     #[unstable(feature = "oneshot_channel", issue = "143674")]
     pub fn recv(self) -> Result<T, RecvError> {
         self.inner.recv()
     }

     // Fallible methods.

     /// Attempts to return a pending value on this receiver without blocking.
     ///
     /// # Examples
     ///
     /// ```
     /// #![feature(oneshot_channel)]
     /// use std::sync::oneshot;
     /// use std::thread;
     /// use std::time::Duration;
     ///
     /// let (sender, mut receiver) = oneshot::channel();
     ///
     /// thread::spawn(move || {
     ///     thread::sleep(Duration::from_millis(100));
     ///     sender.send(42).unwrap();
     /// });
     ///
     /// // Keep trying until we get the message, doing other work in the process.
     /// loop {
     ///     match receiver.try_recv() {
     ///         Ok(value) => {
     ///             assert_eq!(value, 42);
     ///             break;
     ///         }
     ///         Err(oneshot::TryRecvError::Empty(rx)) => {
     ///             // Retake ownership of the receiver.
     ///             receiver = rx;
     /// #           fn do_other_work() { thread::sleep(Duration::from_millis(25)); }
     ///             do_other_work();
     ///         }
     ///         Err(oneshot::TryRecvError::Disconnected) => panic!("Sender disconnected"),
     ///     }
     /// }
     /// ```
     #[unstable(feature = "oneshot_channel", issue = "143674")]
     pub fn try_recv(self) -> Result<T, TryRecvError<T>> {
         self.inner.try_recv().map_err(|err| match err {
             mpmc::TryRecvError::Empty => TryRecvError::Empty(self),
             mpmc::TryRecvError::Disconnected => TryRecvError::Disconnected,
         })
     }

     /// Attempts to wait for a value on this receiver, returning an error if the corresponding
     /// [`Sender`] half of this channel has been dropped, or if it waits more than `timeout`.
     ///
     /// # Examples
     ///
     /// ```
     /// #![feature(oneshot_channel)]
     /// use std::sync::oneshot;
     /// use std::thread;
     /// use std::time::Duration;
     ///
     /// let (sender, receiver) = oneshot::channel();
     ///
     /// thread::spawn(move || {
     ///     thread::sleep(Duration::from_millis(500));
     ///     sender.send("Success!").unwrap();
     /// });
     ///
     /// // Wait up to 1 second for the message
     /// match receiver.recv_timeout(Duration::from_secs(1)) {
     ///     Ok(msg) => println!("Received: {}", msg),
     ///     Err(oneshot::RecvTimeoutError::Timeout(_)) => println!("Timed out!"),
     ///     Err(oneshot::RecvTimeoutError::Disconnected) => println!("Sender dropped!"),
     /// }
     /// ```
     #[unstable(feature = "oneshot_channel", issue = "143674")]
     pub fn recv_timeout(self, timeout: Duration) -> Result<T, RecvTimeoutError<T>> {
         self.inner.recv_timeout(timeout).map_err(|err| match err {
             mpmc::RecvTimeoutError::Timeout => RecvTimeoutError::Timeout(self),
             mpmc::RecvTimeoutError::Disconnected => RecvTimeoutError::Disconnected,
         })
     }

     /// Attempts to wait for a value on this receiver, returning an error if the corresponding
     /// [`Sender`] half of this channel has been dropped, or if `deadline` is reached.
     ///
     /// # Examples
     ///
     /// ```
     /// #![feature(oneshot_channel)]
     /// use std::sync::oneshot;
     /// use std::thread;
     /// use std::time::{Duration, Instant};
     ///
     /// let (sender, receiver) = oneshot::channel();
     ///
     /// thread::spawn(move || {
     ///     thread::sleep(Duration::from_millis(100));
     ///     sender.send("Just in time!").unwrap();
     /// });
     ///
     /// let deadline = Instant::now() + Duration::from_millis(500);
     /// match receiver.recv_deadline(deadline) {
     ///     Ok(msg) => println!("Received: {}", msg),
     ///     Err(oneshot::RecvTimeoutError::Timeout(_)) => println!("Missed deadline!"),
     ///     Err(oneshot::RecvTimeoutError::Disconnected) => println!("Sender dropped!"),
     /// }
     /// ```
     #[unstable(feature = "oneshot_channel", issue = "143674")]
     pub fn recv_deadline(self, deadline: Instant) -> Result<T, RecvTimeoutError<T>> {
         self.inner.recv_deadline(deadline).map_err(|err| match err {
             mpmc::RecvTimeoutError::Timeout => RecvTimeoutError::Timeout(self),
             mpmc::RecvTimeoutError::Disconnected => RecvTimeoutError::Disconnected,
         })
     }
 }

 #[unstable(feature = "oneshot_channel", issue = "143674")]
 impl<T> fmt::Debug for Receiver<T> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_struct("Receiver").finish_non_exhaustive()
     }
 }

 ////////////////////////////////////////////////////////////////////////////////////////////////////
 // Receiver Errors
 ////////////////////////////////////////////////////////////////////////////////////////////////////

 /// An error returned from the [`try_recv`](Receiver::try_recv) method.
 ///
 /// See the documentation for [`try_recv`] for more information on how to use this error.
 ///
 /// [`try_recv`]: Receiver::try_recv
 #[unstable(feature = "oneshot_channel", issue = "143674")]
 pub enum TryRecvError<T> {
     /// The [`Sender`] has not sent a message yet, but it might in the future (as it has not yet
     /// disconnected). This variant contains the [`Receiver`] that [`try_recv`](Receiver::try_recv)
     /// took ownership over.
     Empty(Receiver<T>),
     /// The corresponding [`Sender`] half of this channel has become disconnected, and there will
     /// never be any more data sent over the channel.
     Disconnected,
 }

 /// An error returned from the [`recv_timeout`](Receiver::recv_timeout) or
 /// [`recv_deadline`](Receiver::recv_deadline) methods.
 ///
 /// # Examples
 ///
 /// Usage of this error is similar to [`TryRecvError`].
 ///
 /// ```
 /// #![feature(oneshot_channel)]
 /// use std::sync::oneshot::{self, RecvTimeoutError};
 /// use std::thread;
 /// use std::time::Duration;
 ///
 /// let (sender, receiver) = oneshot::channel();
 ///
 /// let send_failure = thread::spawn(move || {
 ///     // Simulate a long computation that takes longer than our timeout.
 ///     thread::sleep(Duration::from_millis(250));
 ///
 ///     // This will likely fail to send because we drop the receiver in the main thread.
 ///     sender.send("Goodbye!".to_string()).unwrap();
 /// });
 ///
 /// // Try to receive the message with a short timeout.
 /// match receiver.recv_timeout(Duration::from_millis(10)) {
 ///     Ok(msg) => println!("Received: {}", msg),
 ///     Err(RecvTimeoutError::Timeout(rx)) => {
 ///         println!("Timed out waiting for message!");
 ///
 ///         // Note that you can reuse the receiver without dropping it.
 ///         drop(rx);
 ///     },
 ///     Err(RecvTimeoutError::Disconnected) => println!("Sender dropped!"),
 /// }
 ///
 /// send_failure.join().unwrap_err();
 /// ```
 #[unstable(feature = "oneshot_channel", issue = "143674")]
 pub enum RecvTimeoutError<T> {
     /// The [`Sender`] has not sent a message yet, but it might in the future (as it has not yet
     /// disconnected). This variant contains the [`Receiver`] that either
     /// [`recv_timeout`](Receiver::recv_timeout) or [`recv_deadline`](Receiver::recv_deadline) took
     /// ownership over.
     Timeout(Receiver<T>),
     /// The corresponding [`Sender`] half of this channel has become disconnected, and there will
     /// never be any more data sent over the channel.
     Disconnected,
 }

 #[unstable(feature = "oneshot_channel", issue = "143674")]
 impl<T> fmt::Debug for TryRecvError<T> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_tuple("TryRecvError").finish_non_exhaustive()
     }
 }

 #[unstable(feature = "oneshot_channel", issue = "143674")]
 impl<T> fmt::Display for TryRecvError<T> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match *self {
             TryRecvError::Empty(..) => "receiving on an empty oneshot channel".fmt(f),
             TryRecvError::Disconnected => "receiving on a closed oneshot channel".fmt(f),
         }
     }
 }

 #[unstable(feature = "oneshot_channel", issue = "143674")]
 impl<T> error::Error for TryRecvError<T> {}

 #[unstable(feature = "oneshot_channel", issue = "143674")]
 impl<T> From<RecvError> for TryRecvError<T> {
     /// Converts a `RecvError` into a `TryRecvError`.
     ///
     /// This conversion always returns `TryRecvError::Disconnected`.
     ///
     /// No data is allocated on the heap.
     fn from(err: RecvError) -> TryRecvError<T> {
         match err {
             RecvError => TryRecvError::Disconnected,
         }
     }
 }

 #[unstable(feature = "oneshot_channel", issue = "143674")]
 impl<T> fmt::Debug for RecvTimeoutError<T> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_tuple("RecvTimeoutError").finish_non_exhaustive()
     }
 }

 #[unstable(feature = "oneshot_channel", issue = "143674")]
 impl<T> fmt::Display for RecvTimeoutError<T> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match *self {
             RecvTimeoutError::Timeout(..) => "timed out waiting on oneshot channel".fmt(f),
             RecvTimeoutError::Disconnected => "receiving on a closed oneshot channel".fmt(f),
         }
     }
 }

 #[unstable(feature = "oneshot_channel", issue = "143674")]
 impl<T> error::Error for RecvTimeoutError<T> {}

 #[unstable(feature = "oneshot_channel", issue = "143674")]
 impl<T> From<RecvError> for RecvTimeoutError<T> {
     /// Converts a `RecvError` into a `RecvTimeoutError`.
     ///
     /// This conversion always returns `RecvTimeoutError::Disconnected`.
     ///
     /// No data is allocated on the heap.
     fn from(err: RecvError) -> RecvTimeoutError<T> {
         match err {
             RecvError => RecvTimeoutError::Disconnected,
         }
     }
 }
	//! A single-producer, single-consumer (oneshot) channel.
	//!
	//! This is an experimental module, so the API will likely change.

	use crate::sync::mpmc;
	use crate::sync::mpsc::{RecvError, SendError};
	use crate::time::{Duration, Instant};
	use crate::{error, fmt};

	/// Creates a new oneshot channel, returning the sender/receiver halves.
	///
	/// # Examples
	///
	/// ```
	/// #![feature(oneshot_channel)]
	/// use std::sync::oneshot;
	/// use std::thread;
	///
	/// let (sender, receiver) = oneshot::channel();
	///
	/// // Spawn off an expensive computation.
	/// thread::spawn(move \|\| {
	/// # fn expensive_computation() -> i32 { 42 }
	/// sender.send(expensive_computation()).unwrap();
	/// // `sender` is consumed by `send`, so we cannot use it anymore.
	/// });
	///
	/// # fn do_other_work() -> i32 { 42 }
	/// do_other_work();
	///
	/// // Let's see what that answer was...
	/// println!("{:?}", receiver.recv().unwrap());
	/// // `receiver` is consumed by `recv`, so we cannot use it anymore.
	/// ```
	#[must_use]
	#[unstable(feature = "oneshot_channel", issue = "143674")]
	pub fn channel<T>() -> (Sender<T>, Receiver<T>) {
	// Using a `sync_channel` with capacity 1 means that the internal implementation will use the
	// `Array`-flavored channel implementation.
	let (sender, receiver) = mpmc::sync_channel(1);
	(Sender { inner: sender }, Receiver { inner: receiver })
	}

	////////////////////////////////////////////////////////////////////////////////////////////////////
	// Sender
	////////////////////////////////////////////////////////////////////////////////////////////////////

	/// The sending half of a oneshot channel.
	///
	/// # Examples
	///
	/// ```
	/// #![feature(oneshot_channel)]
	/// use std::sync::oneshot;
	/// use std::thread;
	///
	/// let (sender, receiver) = oneshot::channel();
	///
	/// thread::spawn(move \|\| {
	/// sender.send("Hello from thread!").unwrap();
	/// });
	///
	/// assert_eq!(receiver.recv().unwrap(), "Hello from thread!");
	/// ```
	///
	/// `Sender` cannot be sent between threads if it is sending non-`Send` types.
	///
	/// ```compile_fail
	/// #![feature(oneshot_channel)]
	/// use std::sync::oneshot;
	/// use std::thread;
	/// use std::ptr;
	///
	/// let (sender, receiver) = oneshot::channel();
	///
	/// struct NotSend(*mut ());
	/// thread::spawn(move \|\| {
	/// sender.send(NotSend(ptr::null_mut()));
	/// });
	///
	/// let reply = receiver.try_recv().unwrap();
	/// ```
	#[unstable(feature = "oneshot_channel", issue = "143674")]
	pub struct Sender<T> {
	/// The `oneshot` channel is simply a wrapper around a `mpmc` channel.
	inner: mpmc::Sender<T>,
	}

	// SAFETY: Since the only methods in which synchronization must occur take full ownership of the
	// [`Sender`], it is perfectly safe to share a `&Sender` between threads (as it is effectively
	// useless without ownership).
	#[unstable(feature = "oneshot_channel", issue = "143674")]
	unsafe impl<T> Sync for Sender<T> {}

	impl<T> Sender<T> {
	/// Attempts to send a value through this channel. This can only fail if the corresponding
	/// [`Receiver<T>`] has been dropped.
	///
	/// This method is non-blocking (wait-free).
	///
	/// # Examples
	///
	/// ```
	/// #![feature(oneshot_channel)]
	/// use std::sync::oneshot;
	/// use std::thread;
	///
	/// let (tx, rx) = oneshot::channel();
	///
	/// thread::spawn(move \|\| {
	/// // Perform some computation.
	/// let result = 2 + 2;
	/// tx.send(result).unwrap();
	/// });
	///
	/// assert_eq!(rx.recv().unwrap(), 4);
	/// ```
	#[unstable(feature = "oneshot_channel", issue = "143674")]
	pub fn send(self, t: T) -> Result<(), SendError<T>> {
	self.inner.send(t)
	}
	}

	#[unstable(feature = "oneshot_channel", issue = "143674")]
	impl<T> fmt::Debug for Sender<T> {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
	f.debug_struct("Sender").finish_non_exhaustive()
	}
	}

	////////////////////////////////////////////////////////////////////////////////////////////////////
	// Receiver
	////////////////////////////////////////////////////////////////////////////////////////////////////

	/// The receiving half of a oneshot channel.
	///
	/// # Examples
	///
	/// ```
	/// #![feature(oneshot_channel)]
	/// use std::sync::oneshot;
	/// use std::thread;
	/// use std::time::Duration;
	///
	/// let (sender, receiver) = oneshot::channel();
	///
	/// thread::spawn(move \|\| {
	/// thread::sleep(Duration::from_millis(100));
	/// sender.send("Hello after delay!").unwrap();
	/// });
	///
	/// println!("Waiting for message...");
	/// println!("{}", receiver.recv().unwrap());
	/// ```
	///
	/// `Receiver` cannot be sent between threads if it is receiving non-`Send` types.
	///
	/// ```compile_fail
	/// # #![feature(oneshot_channel)]
	/// # use std::sync::oneshot;
	/// # use std::thread;
	/// # use std::ptr;
	/// #
	/// let (sender, receiver) = oneshot::channel();
	///
	/// struct NotSend(*mut ());
	/// sender.send(NotSend(ptr::null_mut()));
	///
	/// thread::spawn(move \|\| {
	/// let reply = receiver.try_recv().unwrap();
	/// });
	/// ```
	#[unstable(feature = "oneshot_channel", issue = "143674")]
	pub struct Receiver<T> {
	/// The `oneshot` channel is simply a wrapper around a `mpmc` channel.
	inner: mpmc::Receiver<T>,
	}

	// SAFETY: Since the only methods in which synchronization must occur take full ownership of the
	// [`Receiver`], it is perfectly safe to share a `&Receiver` between threads (as it is unable to
	// receive any values without ownership).
	#[unstable(feature = "oneshot_channel", issue = "143674")]
	unsafe impl<T> Sync for Receiver<T> {}

	impl<T> Receiver<T> {
	/// Receives the value from the sending end, blocking the calling thread until it gets it.
	///
	/// Can only fail if the corresponding [`Sender<T>`] has been dropped.
	///
	/// # Examples
	///
	/// ```
	/// #![feature(oneshot_channel)]
	/// use std::sync::oneshot;
	/// use std::thread;
	/// use std::time::Duration;
	///
	/// let (tx, rx) = oneshot::channel();
	///
	/// thread::spawn(move \|\| {
	/// thread::sleep(Duration::from_millis(500));
	/// tx.send("Done!").unwrap();
	/// });
	///
	/// // This will block until the message arrives.
	/// println!("{}", rx.recv().unwrap());
	/// ```
	#[unstable(feature = "oneshot_channel", issue = "143674")]
	pub fn recv(self) -> Result<T, RecvError> {
	self.inner.recv()
	}

	// Fallible methods.

	/// Attempts to return a pending value on this receiver without blocking.
	///
	/// # Examples
	///
	/// ```
	/// #![feature(oneshot_channel)]
	/// use std::sync::oneshot;
	/// use std::thread;
	/// use std::time::Duration;
	///
	/// let (sender, mut receiver) = oneshot::channel();
	///
	/// thread::spawn(move \|\| {
	/// thread::sleep(Duration::from_millis(100));
	/// sender.send(42).unwrap();
	/// });
	///
	/// // Keep trying until we get the message, doing other work in the process.
	/// loop {
	/// match receiver.try_recv() {
	/// Ok(value) => {
	/// assert_eq!(value, 42);
	/// break;
	/// }
	/// Err(oneshot::TryRecvError::Empty(rx)) => {
	/// // Retake ownership of the receiver.
	/// receiver = rx;
	/// # fn do_other_work() { thread::sleep(Duration::from_millis(25)); }
	/// do_other_work();
	/// }
	/// Err(oneshot::TryRecvError::Disconnected) => panic!("Sender disconnected"),
	/// }
	/// }
	/// ```
	#[unstable(feature = "oneshot_channel", issue = "143674")]
	pub fn try_recv(self) -> Result<T, TryRecvError<T>> {
	self.inner.try_recv().map_err(\|err\| match err {
	mpmc::TryRecvError::Empty => TryRecvError::Empty(self),
	mpmc::TryRecvError::Disconnected => TryRecvError::Disconnected,
	})
	}

	/// Attempts to wait for a value on this receiver, returning an error if the corresponding
	/// [`Sender`] half of this channel has been dropped, or if it waits more than `timeout`.
	///
	/// # Examples
	///
	/// ```
	/// #![feature(oneshot_channel)]
	/// use std::sync::oneshot;
	/// use std::thread;
	/// use std::time::Duration;
	///
	/// let (sender, receiver) = oneshot::channel();
	///
	/// thread::spawn(move \|\| {
	/// thread::sleep(Duration::from_millis(500));
	/// sender.send("Success!").unwrap();
	/// });
	///
	/// // Wait up to 1 second for the message
	/// match receiver.recv_timeout(Duration::from_secs(1)) {
	/// Ok(msg) => println!("Received: {}", msg),
	/// Err(oneshot::RecvTimeoutError::Timeout(_)) => println!("Timed out!"),
	/// Err(oneshot::RecvTimeoutError::Disconnected) => println!("Sender dropped!"),
	/// }
	/// ```
	#[unstable(feature = "oneshot_channel", issue = "143674")]
	pub fn recv_timeout(self, timeout: Duration) -> Result<T, RecvTimeoutError<T>> {
	self.inner.recv_timeout(timeout).map_err(\|err\| match err {
	mpmc::RecvTimeoutError::Timeout => RecvTimeoutError::Timeout(self),
	mpmc::RecvTimeoutError::Disconnected => RecvTimeoutError::Disconnected,
	})
	}

	/// Attempts to wait for a value on this receiver, returning an error if the corresponding
	/// [`Sender`] half of this channel has been dropped, or if `deadline` is reached.
	///
	/// # Examples
	///
	/// ```
	/// #![feature(oneshot_channel)]
	/// use std::sync::oneshot;
	/// use std::thread;
	/// use std::time::{Duration, Instant};
	///
	/// let (sender, receiver) = oneshot::channel();
	///
	/// thread::spawn(move \|\| {
	/// thread::sleep(Duration::from_millis(100));
	/// sender.send("Just in time!").unwrap();
	/// });
	///
	/// let deadline = Instant::now() + Duration::from_millis(500);
	/// match receiver.recv_deadline(deadline) {
	/// Ok(msg) => println!("Received: {}", msg),
	/// Err(oneshot::RecvTimeoutError::Timeout(_)) => println!("Missed deadline!"),
	/// Err(oneshot::RecvTimeoutError::Disconnected) => println!("Sender dropped!"),
	/// }
	/// ```
	#[unstable(feature = "oneshot_channel", issue = "143674")]
	pub fn recv_deadline(self, deadline: Instant) -> Result<T, RecvTimeoutError<T>> {
	self.inner.recv_deadline(deadline).map_err(\|err\| match err {
	mpmc::RecvTimeoutError::Timeout => RecvTimeoutError::Timeout(self),
	mpmc::RecvTimeoutError::Disconnected => RecvTimeoutError::Disconnected,
	})
	}
	}

	#[unstable(feature = "oneshot_channel", issue = "143674")]
	impl<T> fmt::Debug for Receiver<T> {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
	f.debug_struct("Receiver").finish_non_exhaustive()
	}
	}

	////////////////////////////////////////////////////////////////////////////////////////////////////
	// Receiver Errors
	////////////////////////////////////////////////////////////////////////////////////////////////////

	/// An error returned from the [`try_recv`](Receiver::try_recv) method.
	///
	/// See the documentation for [`try_recv`] for more information on how to use this error.
	///
	/// [`try_recv`]: Receiver::try_recv
	#[unstable(feature = "oneshot_channel", issue = "143674")]
	pub enum TryRecvError<T> {
	/// The [`Sender`] has not sent a message yet, but it might in the future (as it has not yet
	/// disconnected). This variant contains the [`Receiver`] that [`try_recv`](Receiver::try_recv)
	/// took ownership over.
	Empty(Receiver<T>),
	/// The corresponding [`Sender`] half of this channel has become disconnected, and there will
	/// never be any more data sent over the channel.
	Disconnected,
	}

	/// An error returned from the [`recv_timeout`](Receiver::recv_timeout) or
	/// [`recv_deadline`](Receiver::recv_deadline) methods.
	///
	/// # Examples
	///
	/// Usage of this error is similar to [`TryRecvError`].
	///
	/// ```
	/// #![feature(oneshot_channel)]
	/// use std::sync::oneshot::{self, RecvTimeoutError};
	/// use std::thread;
	/// use std::time::Duration;
	///
	/// let (sender, receiver) = oneshot::channel();
	///
	/// let send_failure = thread::spawn(move \|\| {
	/// // Simulate a long computation that takes longer than our timeout.
	/// thread::sleep(Duration::from_millis(250));
	///
	/// // This will likely fail to send because we drop the receiver in the main thread.
	/// sender.send("Goodbye!".to_string()).unwrap();
	/// });
	///
	/// // Try to receive the message with a short timeout.
	/// match receiver.recv_timeout(Duration::from_millis(10)) {
	/// Ok(msg) => println!("Received: {}", msg),
	/// Err(RecvTimeoutError::Timeout(rx)) => {
	/// println!("Timed out waiting for message!");
	///
	/// // Note that you can reuse the receiver without dropping it.
	/// drop(rx);
	/// },
	/// Err(RecvTimeoutError::Disconnected) => println!("Sender dropped!"),
	/// }
	///
	/// send_failure.join().unwrap_err();
	/// ```
	#[unstable(feature = "oneshot_channel", issue = "143674")]
	pub enum RecvTimeoutError<T> {
	/// The [`Sender`] has not sent a message yet, but it might in the future (as it has not yet
	/// disconnected). This variant contains the [`Receiver`] that either
	/// [`recv_timeout`](Receiver::recv_timeout) or [`recv_deadline`](Receiver::recv_deadline) took
	/// ownership over.
	Timeout(Receiver<T>),
	/// The corresponding [`Sender`] half of this channel has become disconnected, and there will
	/// never be any more data sent over the channel.
	Disconnected,
	}

	#[unstable(feature = "oneshot_channel", issue = "143674")]
	impl<T> fmt::Debug for TryRecvError<T> {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
	f.debug_tuple("TryRecvError").finish_non_exhaustive()
	}
	}

	#[unstable(feature = "oneshot_channel", issue = "143674")]
	impl<T> fmt::Display for TryRecvError<T> {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
	match *self {
	TryRecvError::Empty(..) => "receiving on an empty oneshot channel".fmt(f),
	TryRecvError::Disconnected => "receiving on a closed oneshot channel".fmt(f),
	}
	}
	}

	#[unstable(feature = "oneshot_channel", issue = "143674")]
	impl<T> error::Error for TryRecvError<T> {}

	#[unstable(feature = "oneshot_channel", issue = "143674")]
	impl<T> From<RecvError> for TryRecvError<T> {
	/// Converts a `RecvError` into a `TryRecvError`.
	///
	/// This conversion always returns `TryRecvError::Disconnected`.
	///
	/// No data is allocated on the heap.
	fn from(err: RecvError) -> TryRecvError<T> {
	match err {
	RecvError => TryRecvError::Disconnected,
	}
	}
	}

	#[unstable(feature = "oneshot_channel", issue = "143674")]
	impl<T> fmt::Debug for RecvTimeoutError<T> {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
	f.debug_tuple("RecvTimeoutError").finish_non_exhaustive()
	}
	}

	#[unstable(feature = "oneshot_channel", issue = "143674")]
	impl<T> fmt::Display for RecvTimeoutError<T> {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
	match *self {
	RecvTimeoutError::Timeout(..) => "timed out waiting on oneshot channel".fmt(f),
	RecvTimeoutError::Disconnected => "receiving on a closed oneshot channel".fmt(f),
	}
	}
	}

	#[unstable(feature = "oneshot_channel", issue = "143674")]
	impl<T> error::Error for RecvTimeoutError<T> {}

	#[unstable(feature = "oneshot_channel", issue = "143674")]
	impl<T> From<RecvError> for RecvTimeoutError<T> {
	/// Converts a `RecvError` into a `RecvTimeoutError`.
	///
	/// This conversion always returns `RecvTimeoutError::Disconnected`.
	///
	/// No data is allocated on the heap.
	fn from(err: RecvError) -> RecvTimeoutError<T> {
	match err {
	RecvError => RecvTimeoutError::Disconnected,
	}
	}
	}