https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99967
Bug ID: 99967 Summary: gcc accepts declaration type contains unexpanded parameter pack Product: gcc Version: 11.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: hewillk at gmail dot com Target Milestone: --- https://godbolt.org/z/cdqq3ocTG template <class...> concept C = true; template <typename... Ts> void f() { C<Ts> auto x = 0; }; int main() { f(); } gcc accepts it.