https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70862
--- Comment #1 from ryan.burn at gmail dot com --- Simpler reproduction: template <class... Tx> concept bool C = true; template <class... Tx> constexpr bool a = false; template <class... Tx> requires C<Tx...> constexpr bool a<Tx...> = true; template <class... Tx> requires a<Tx...> void f(Tx...) { } int main() { f(); f(3); return 0; }