1 // { dg-do compile { target c++17 } } 2 // { dg-options "-fconcepts" } 3 4 template<typename ... T> 5 concept bool C1 = true; 6 7 template<int ... N> 8 concept bool C2 = true; 9 10 template<typename T> 11 concept bool C3 = __is_class(T); 12 13 template<typename ... T> C4()14 concept bool C4() { return true; } 15 template<int N> C4()16 concept bool C4() { return true; } 17 18 template<typename T, typename U = int> C5()19 concept bool C5() { return __is_class(U); } 20 f1()21C1{...A, B} void f1() {}; // { dg-error "no matching|wrong number" } f2()22C1{A} void f2() {} // { dg-error "cannot match pack|no matching concept" } f3()23C2{A, B} void f3() {}; // { dg-error "cannot match pack|no matching concept" } f4()24C3{...A} void f4() {}; // { dg-error "cannot match pack|no matching concept" } f5()25C4{A} void f5() {}; // { dg-error "no matching concept" } f6()26C5{A, B} void f6() {}; 27 main()28int main() 29 { 30 // Defaults should not transfer 31 f6<int>(); // { dg-error "no matching" } 32 return 0; 33 } 34