1 // Testcase from P0512R0 for C++17 NB comment US 19 2 // { dg-do compile { target c++17 } } 3 4 template<typename> struct remove_ref; 5 template<typename _Tp> struct remove_ref { typedef _Tp type; }; 6 template<typename _Tp> struct remove_ref<_Tp&> { typedef _Tp type; }; 7 template<typename _Tp> struct remove_ref<_Tp&&> { typedef _Tp type; }; 8 template<typename _Tp> using remove_ref_t = typename remove_ref<_Tp>::type; 9 10 template<class T> struct A { 11 A(T, int*); // #1 12 A(A<T>&, int*); // #2 13 enum { value }; 14 }; 15 template<class T, int N = remove_ref_t<T>::value> A(T&&, int*) -> A<T>; //#3 16 17 A a{1,0}; // uses #1 to deduce A<int> and initializes with #1 18 A b{a,0}; // uses #2 to deduce A<int> and initializes with #2 19 20 template <class,class> struct same; 21 template <class T> struct same<T,T> {}; 22 23 same<decltype(a),A<int>> s1; 24 same<decltype(b),A<int>> s2; 25