sync: impl `Error` for oneshot and watch error types (#967)

Refs: #937

1 files changed, 32 insertions, 0 deletions

diff --git a/tokio-sync/src/watch.rs b/tokio-sync/src/watch.rs
index 4c2b2972..b3303bdc 100644
--- a/tokio-sync/src/watch.rs
+++ b/tokio-sync/src/watch.rs
@@ -104,6 +104,8 @@ pub struct Ref<'a, T: 'a> {
 pub mod error {
     //! Watch error types
 
+    use std::fmt;
+
     /// Error produced when receiving a value fails.
     #[derive(Debug)]
     pub struct RecvError {
@@ -115,6 +117,36 @@ pub mod error {
     pub struct SendError<T> {
         pub(crate) inner: T,
     }
+
+    // ===== impl RecvError =====
+
+    impl fmt::Display for RecvError {
+        fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+            use std::error::Error;
+            write!(fmt, "{}", self.description())
+        }
+    }
+
+    impl ::std::error::Error for RecvError {
+        fn description(&self) -> &str {
+            "channel closed"
+        }
+    }
+
+    // ===== impl SendError =====
+
+    impl<T: fmt::Debug> fmt::Display for SendError<T> {
+        fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+            use std::error::Error;
+            write!(fmt, "{}", self.description())
+        }
+    }
+
+    impl<T: fmt::Debug> ::std::error::Error for SendError<T> {
+        fn description(&self) -> &str {
+            "channel closed"
+        }
+    }
 }
 
 #[derive(Debug)]