https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89875
--- Comment #2 from Paolo Carlini <paolo.carlini at oracle dot com> --- If we compare the testcase to a modified version using __decltype, for the latter by the time we reach the place in cp_parser_init_declarator which I changed in r213952 we have already issued an "expected primary-expression before" error. I think that is the way to go.