neonet += ErrUnexpectedMsg to propagate msg type

go/neo/neonet/connection.go

@@ -231,6 +231,15 @@ var ErrLinkNoListen = errors.New("node link is not listening for incoming connec
 var ErrLinkManyConn = errors.New("too many opened connections")
 var ErrClosedConn   = errors.New("connection is closed")
 
+type ErrUnexpectedMsg struct {
+    Msg  string
+    MsgType reflect.Type
+}
+
+func (e *ErrUnexpectedMsg) Error() string {
+    return fmt.Sprintf("%s %v", e.Msg, e.MsgType)
+}
+
 // LinkError is returned by NodeLink operations.
 type LinkError struct {
 	Link *NodeLink
@@ -1600,7 +1609,7 @@ func (c *Conn) Expect(msgv ...proto.Msg) (which int, err error) {
 	}
 
 	// XXX also add which messages were expected ?
-	return -1, c.err("recv", fmt.Errorf("unexpected message: %v", msgType))
+	return -1, c.err("recv", &ErrUnexpectedMsg{"unexpected message", msgType})
 }
 
 // Ask sends request and receives a response.