sync: derive PartialEq for error enums (#2137)

tokio/src/sync/mpsc/error.rs

@@ -69,7 +69,7 @@ impl Error for RecvError {}
 
 /// This enumeration is the list of the possible reasons that try_recv
 /// could not return data when called.
-#[derive(Debug)]
+#[derive(Debug, PartialEq)]
 pub enum TryRecvError {
     /// This channel is currently empty, but the Sender(s) have not yet
     /// disconnected, so data may yet become available.

tokio/src/sync/oneshot.rs

@@ -40,7 +40,7 @@ pub mod error {
     pub struct RecvError(pub(super) ());
 
     /// Error returned by the `try_recv` function on `Receiver`.
-    #[derive(Debug)]
+    #[derive(Debug, PartialEq)]
     pub enum TryRecvError {
         /// The send half of the channel has not yet sent a value.
         Empty,