| // { dg-do compile { target c++17_only } } |
| // { dg-options "-fconcepts" } |
| |
| template <class T> concept bool Copyable = requires (T t) { T(t); }; |
| template <class T> concept bool Constructable = requires { T(); }; |
| template <class T> concept bool Both = Copyable<T> && Constructable<T>; |
| |
| template <Copyable... Ts> // requires (Copyable<Ts> && ...) |
| constexpr int f(Ts...) { return 0; } // #1 |
| |
| template <Both... Ts> // requires (Both<Ts> && ...) |
| constexpr int f(Ts...) { return 1; } // #2 |
| |
| int main() |
| { |
| static_assert(f(42) == 1); // { dg-error "ambiguous" } |
| // The associated constraints of the two functions are incomparable. |
| } |
