http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47436
--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-09-22 19:19:21 UTC --- I'd go for "error: variadic template A<T> is invalid because every valid specialization requires an empty template parameter pack" but I'm not sure that would be needed if the original error simply said "error: unions cannot have base classes" - I think that's clear enough
