Remove the sync::spsc module for now

It no longer has as much functionality as the `mpsc` module and it's not clear
that the perf is all that different to buy two separate queue implementations.
The `spsc` queues have been moved to a `futures-spsc` crate for now and if they
prove themselves in the long run we can move them back into this crate.

Author: alexcrichton

src/stream/channel.rs

@@ -1,5 +1,5 @@
 #![cfg(feature = "with-deprecated")]
-#![deprecated(since = "0.1.4", note = "use sync::spsc::channel instead")]
+#![deprecated(since = "0.1.4", note = "use sync::mpsc::channel instead")]
 #![allow(deprecated)]
 
 use std::any::Any;
@@ -8,7 +8,7 @@ use std::fmt;
 
 use {Poll, Async, Stream, Future, Sink};
 use sink::Send;
-use sync::spsc;
+use sync::mpsc;
 
 /// Creates an in-memory channel implementation of the `Stream` trait.
 ///
@@ -22,15 +22,15 @@ use sync::spsc;
 /// 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) = spsc::channel();
+    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.
 pub struct Sender<T, E> {
-    inner: spsc::Sender<Result<T, E>>,
+    inner: mpsc::Sender<Result<T, E>>,
 }
 
 /// The receiving end of a channel which implements the `Stream` trait.
@@ -40,15 +40,15 @@ pub struct Sender<T, E> {
 /// `channel` method in the `stream` module.
 #[must_use = "streams do nothing unless polled"]
 pub struct Receiver<T, E> {
-    inner: spsc::Receiver<Result<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`.
 pub struct FutureSender<T, E> {
-    inner: Send<spsc::Sender<Result<T, E>>>,
+    inner: Send<mpsc::Sender<Result<T, E>>>,
 }
 
 impl<T, E> fmt::Debug for SendError<T, E> {

src/stream/mod.rs

@@ -196,9 +196,9 @@ pub trait Stream {
     ///
     /// ```
     /// use futures::stream::*;
-    /// use futures::sync::spsc;
+    /// use futures::sync::mpsc;
     ///
-    /// let (_tx, rx) = spsc::channel();
+    /// let (_tx, rx) = mpsc::channel(1);
     /// let a: BoxStream<i32, ()> = rx.boxed();
     /// ```
     #[cfg(feature = "use_std")]
@@ -237,9 +237,9 @@ pub trait Stream {
     ///
     /// ```
     /// use futures::Stream;
-    /// use futures::sync::spsc;
+    /// use futures::sync::mpsc;
     ///
-    /// let (_tx, rx) = spsc::channel::<i32>();
+    /// let (_tx, rx) = mpsc::channel::<i32>(1);
     /// let rx = rx.map(|x| x + 3);
     /// ```
     fn map<U, F>(self, f: F) -> Map<Self, F>
@@ -263,9 +263,9 @@ pub trait Stream {
     ///
     /// ```
     /// use futures::Stream;
-    /// use futures::sync::spsc;
+    /// use futures::sync::mpsc;
     ///
-    /// let (_tx, rx) = spsc::channel::<i32>();
+    /// let (_tx, rx) = mpsc::channel::<i32>(1);
     /// let rx = rx.map_err(|()| 3);
     /// ```
     fn map_err<U, F>(self, f: F) -> MapErr<Self, F>
@@ -293,9 +293,9 @@ pub trait Stream {
     ///
     /// ```
     /// use futures::Stream;
-    /// use futures::sync::spsc;
+    /// use futures::sync::mpsc;
     ///
-    /// let (_tx, rx) = spsc::channel::<i32>();
+    /// let (_tx, rx) = mpsc::channel::<i32>(1);
     /// let evens = rx.filter(|x| x % 0 == 2);
     /// ```
     fn filter<F>(self, f: F) -> Filter<Self, F>
@@ -323,9 +323,9 @@ pub trait Stream {
     ///
     /// ```
     /// use futures::Stream;
-    /// use futures::sync::spsc;
+    /// use futures::sync::mpsc;
     ///
-    /// let (_tx, rx) = spsc::channel::<i32>();
+    /// let (_tx, rx) = mpsc::channel::<i32>(1);
     /// let evens_plus_one = rx.filter_map(|x| {
     ///     if x % 0 == 2 {
     ///         Some(x + 1)
@@ -362,9 +362,9 @@ pub trait Stream {
     ///
     /// ```
     /// use futures::Stream;
-    /// use futures::sync::spsc;
+    /// use futures::sync::mpsc;
     ///
-    /// let (_tx, rx) = spsc::channel::<i32>();
+    /// let (_tx, rx) = mpsc::channel::<i32>(1);
     ///
     /// let rx = rx.then(|result| {
     ///     match result {
@@ -405,9 +405,9 @@ pub trait Stream {
     ///
     /// ```
     /// use futures::stream::*;
-    /// use futures::sync::spsc;
+    /// use futures::sync::mpsc;
     ///
-    /// let (_tx, rx) = spsc::channel::<i32>();
+    /// let (_tx, rx) = mpsc::channel::<i32>(1);
     ///
     /// let rx = rx.and_then(|result| {
     ///     if result % 2 == 0 {
@@ -468,9 +468,9 @@ pub trait Stream {
     /// use std::thread;
     ///
     /// use futures::{Stream, Future, Sink};
-    /// use futures::sync::spsc;
+    /// use futures::sync::mpsc;
     ///
-    /// let (mut tx, rx) = spsc::channel();
+    /// let (mut tx, rx) = mpsc::channel(1);
     ///
     /// thread::spawn(|| {
     ///     for i in (0..5).rev() {
@@ -530,11 +530,11 @@ pub trait Stream {
     /// use std::thread;
     ///
     /// use futures::{Future, Stream, Poll, Sink};
-    /// use futures::sync::spsc;
+    /// use futures::sync::mpsc;
     ///
-    /// let (tx1, rx1) = spsc::channel::<i32>();
-    /// let (tx2, rx2) = spsc::channel::<i32>();
-    /// let (tx3, rx3) = spsc::channel();
+    /// let (tx1, rx1) = mpsc::channel::<i32>(1);
+    /// let (tx2, rx2) = mpsc::channel::<i32>(1);
+    /// let (tx3, rx3) = mpsc::channel(1);
     ///
     /// thread::spawn(|| {
     ///     tx1.send(1).wait().unwrap()

src/sync/mod.rs

@@ -6,7 +6,6 @@
 //! instead work at the task level.
 
 pub mod oneshot;
-pub mod spsc;
 pub mod mpsc;
 mod bilock;
 

src/sync/mpsc/mod.rs

@@ -67,20 +67,19 @@
 // happens-before semantics required for the acquire / release semantics used
 // by the queue structure.
 
-mod queue;
-
-use self::queue::{Queue, PopResult};
+use std::any::Any;
+use std::error::Error;
+use std::fmt;
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::sync::{Arc, Mutex};
+use std::thread;
+use std::usize;
 
-use {Async, AsyncSink, Poll, StartSend};
+use sync::mpsc::queue::{Queue, PopResult};
 use task::{self, Task};
-use sink::{Sink};
-use stream::Stream;
-
-use std::{thread, usize};
-use std::sync::{Arc, Mutex};
-use std::sync::atomic::{AtomicUsize, Ordering};
+use {Async, AsyncSink, Poll, StartSend, Sink, Stream};
 
-pub use std::sync::mpsc::SendError;
+mod queue;
 
 /// The transmission end of a channel which is used to send values.
 ///
@@ -121,6 +120,39 @@ pub struct Receiver<T> {
 /// `unbounded` method.
 pub struct UnboundedReceiver<T>(Receiver<T>);
 
+/// Error type for sending, used when the receiving end of the channel is
+/// dropped
+pub struct SendError<T>(T);
+
+impl<T> fmt::Debug for SendError<T> {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        fmt.debug_tuple("SendError")
+            .field(&"...")
+            .finish()
+    }
+}
+
+impl<T> fmt::Display for SendError<T> {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        write!(fmt, "send failed because receiver is gone")
+    }
+}
+
+impl<T> Error for SendError<T>
+    where T: Any
+{
+    fn description(&self) -> &str {
+        "send failed because receiver is gone"
+    }
+}
+
+impl<T> SendError<T> {
+    /// Returns the message that was attempted to be sent but failed.
+    pub fn into_inner(self) -> T {
+        self.0
+    }
+}
+
 struct Inner<T> {
     // Max buffer size of the channel. If `None` then the channel is unbounded.
     buffer: Option<usize>,
@@ -677,6 +709,16 @@ impl<T> Stream for Receiver<T> {
     }
 }
 
+impl<T> Drop for Receiver<T> {
+    fn drop(&mut self) {
+        // Drain the channel of all pending messages
+        self.close();
+        while self.next_message().is_ready() {
+            // ...
+        }
+    }
+}
+
 impl<T> UnboundedReceiver<T> {
     /// Closes the receiving half
     ///