Implement From<RecvError> for TryRecvError and RecvTimeoutError

Author: ia0

src/libstd/sync/mpsc/mod.rs

@@ -1677,6 +1677,15 @@ impl error::Error for TryRecvError {
     }
 }
 
+#[stable(feature = "mpsc_recv_error_from", since = "1.23.0")]
+impl From<RecvError> for TryRecvError {
+    fn from(err: RecvError) -> TryRecvError {
+        match err {
+            RecvError => TryRecvError::Disconnected,
+        }
+    }
+}
+
 #[stable(feature = "mpsc_recv_timeout_error", since = "1.15.0")]
 impl fmt::Display for RecvTimeoutError {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
@@ -1709,6 +1718,15 @@ impl error::Error for RecvTimeoutError {
     }
 }
 
+#[stable(feature = "mpsc_recv_error_from", since = "1.23.0")]
+impl From<RecvError> for RecvTimeoutError {
+    fn from(err: RecvError) -> RecvTimeoutError {
+        match err {
+            RecvError => RecvTimeoutError::Disconnected,
+        }
+    }
+}
+
 #[cfg(all(test, not(target_os = "emscripten")))]
 mod tests {
     use env;