http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55664
--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-12-12 15:41:21 UTC --- The template is never instantiated so no diagnostic is required. Even if you instantiate it I'm not sure the code is necessarily ill-formed, unles you use the name in a way that requires it to be known to be a type. 7.3.3p19 says: If a using-declaration uses the keyword typename and specifies a dependent name (14.6.2), the name introduced by the using-declaration is treated as a typedef-name (7.1.3). But it doesn't say the keyword typename *must* be used is the using-declaration specifies a dependent name.
