https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94057
--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> --- Not relate to parameter packs. Also happens with normal member functions: template <typename T> class A { template <typename U> class B { B(A<T>::B<U>&); void fn(A<T>::B<U> &); }; };