1 // RUN: %clang_cc1 -std=c++2a -x c++ %s -verify 2 3 template<typename T, int a> 4 concept C1 = true; 5 6 template<C1 T> 7 // expected-error@-1 {{'C1' requires more than 1 template argument; provide the remaining arguments explicitly to use it here}} 8 using badA = T[10]; 9 10 template<C1<0> T> 11 using A = T[10]; 12 13 using a = A<int>; 14 15 namespace ns { 16 template<typename T, typename U, typename... X> 17 concept C2 = true; 18 } 19 20 template<ns::C2 T1, ::ns::C2 T2> 21 // expected-error@-1 2{{'C2' requires more than 1 template argument; provide the remaining arguments explicitly to use it here}} 22 requires (sizeof(T1) <= sizeof(T2)) 23 struct badB { }; 24 25 template<ns::C2<int> T1, ::ns::C2<char, T1> T2> 26 requires (sizeof(T1) <= sizeof(T2)) 27 struct B { }; 28 29 using b = B<int, int>; 30 31 template<ns::C2... T1> 32 // expected-error@-1 {{'C2' requires more than 1 template argument; provide the remaining arguments explicitly to use it here}} 33 struct badC { }; 34 35 template<ns::C2<int>... T1> 36 struct C { }; 37 38 using c1 = C<char, char, char>; 39 using c2 = C<char, char, char, char>;