http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60065
--- Comment #2 from Adam Butcher <abutcher at gcc dot gnu.org> --- Turns out the base template parameter index was not been initialized correctly so it was trying to convert the 'int' parameter to a pack as well as the invented template parameter generated for the 'auto'. See http://gcc.gnu.org/ml/gcc-patches/2014-02/msg01197.html