auto merge of #13610 : jsanders/rust/sender-try-send-docs, r=alexcrichton

I was getting a bit confused by these and (I think) managed to track it down to fallout from #13448 and #13465.

Author: bors

src/libstd/comm/mod.rs

@@ -479,7 +479,7 @@ impl<T: Send> Sender<T> {
     /// then the other end could immediately disconnect.
     ///
     /// The purpose of this functionality is to propagate failure among tasks.
-    /// If failure is not desired, then consider using the `try_send` method
+    /// If failure is not desired, then consider using the `send_opt` method
     pub fn send(&self, t: T) {
         if self.send_opt(t).is_err() {
             fail!("sending on a closed channel");
@@ -669,10 +669,10 @@ impl<T: Send> SyncSender<T> {
 
     /// Attempts to send a value on this channel without blocking.
     ///
-    /// This method semantically differs from `Sender::try_send` because it can
-    /// fail if the receiver has not disconnected yet. If the buffer on this
-    /// channel is full, this function will immediately return the data back to
-    /// the callee.
+    /// This method differs from `send_opt` by returning immediately if the
+    /// channel's buffer is full or no receiver is waiting to acquire some
+    /// data. Compared with `send_opt`, this function has two failure cases
+    /// instead of one (one for disconnection, one for a full buffer).
     ///
     /// See `SyncSender::send` for notes about guarantees of whether the
     /// receiver has received the data or not if this function is successful.