1 2 template<typename _Iterator, typename> 3 struct Trait; 4 5 template<typename _Iterator> 6 struct Trait<_Iterator, void> {}; 7 8 template<typename _Iterator> 9 requires true 10 struct Trait<_Iterator, void> 11 { 12 template<typename _Iter> struct __diff {}; 13 14 template<typename _Iter> requires true struct __diff<_Iter> {}; 15 }; 16