https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80370
--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> --- Guess at least get should return int or int & rather than void: template <typename> struct tuple_size; template <long, typename> struct tuple_element; template <typename...> struct tuple {}; template <typename... T> struct tuple_size<tuple<T...>> { static constexpr int value = 1; }; template <typename T, typename... U> struct tuple_element<0, tuple<T, U...>> { typedef T type; }; template <int, typename... T> int get (tuple<T...>); int main () { [](auto) { [](tuple<int> b) { auto [c] = b; }; }(0); }