Rollup merge of rust-lang#23125 - danburkert:master, r=brson

Author: Manishearth

src/libstd/sync/mpsc/mod.rs

@@ -318,6 +318,7 @@
 use prelude::v1::*;
 
 use sync::Arc;
+use error;
 use fmt;
 use mem;
 use cell::UnsafeCell;
@@ -975,6 +976,18 @@ impl<T> fmt::Display for SendError<T> {
     }
 }
 
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T> error::Error for SendError<T> {
+
+    fn description(&self) -> &str {
+        "sending on a closed channel"
+    }
+
+    fn cause(&self) -> Option<&error::Error> {
+        None
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T> fmt::Debug for TrySendError<T> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
@@ -999,13 +1012,44 @@ impl<T> fmt::Display for TrySendError<T> {
     }
 }
 
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T> error::Error for TrySendError<T> {
+
+    fn description(&self) -> &str {
+        match *self {
+            TrySendError::Full(..) => {
+                "sending on a full channel"
+            }
+            TrySendError::Disconnected(..) => {
+                "sending on a closed channel"
+            }
+        }
+    }
+
+    fn cause(&self) -> Option<&error::Error> {
+        None
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl fmt::Display for RecvError {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         "receiving on a closed channel".fmt(f)
     }
 }
 
+#[stable(feature = "rust1", since = "1.0.0")]
+impl error::Error for RecvError {
+
+    fn description(&self) -> &str {
+        "receiving on a closed channel"
+    }
+
+    fn cause(&self) -> Option<&error::Error> {
+        None
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl fmt::Display for TryRecvError {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
@@ -1020,6 +1064,25 @@ impl fmt::Display for TryRecvError {
     }
 }
 
+#[stable(feature = "rust1", since = "1.0.0")]
+impl error::Error for TryRecvError {
+
+    fn description(&self) -> &str {
+        match *self {
+            TryRecvError::Empty => {
+                "receiving on an empty channel"
+            }
+            TryRecvError::Disconnected => {
+                "receiving on a closed channel"
+            }
+        }
+    }
+
+    fn cause(&self) -> Option<&error::Error> {
+        None
+    }
+}
+
 #[cfg(test)]
 mod test {
     use prelude::v1::*;