Can't see methods of inherited class in code completion when working in other namespace

Code completion doesn't include methods of inherited class if you are working in different namespace. See attachment. In my example I use Google Protocol Buffers library. There are two classes: MessageLite and Message. Class Message inherits MessageLite. If I do not include "using namespace google::protobuf" I can't see methods from class MessageLite in code completion of variable of type Message.