http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53184
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> 2012-05-02 06:25:50 UTC --- >foo.cpp:5:16: warning: 'Bar' has a field 'Bar::foo' whose type uses the anonymous namespace [enabled by default] The warning just needs to be worded better but otherwise it is correct. It is using a type which is anonymous.