https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126653
--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> --- We don't detect [namespace.udir]/1: The splice-specifier (if any) shall designate a namespace that is not the global namespace. The nested-name-specifier, namespace-name, and splice-specifier shall not be dependent. So this also needs to test using namespace [: ^^:: :];
