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>;