| // { dg-do compile { target c++20 } } |
| |
| // Bug libstdc++/120625 |
| // std::formatter<__disabled> specializations cause errors in user code |
| |
| #include <format> |
| |
| enum X { }; |
| |
| // A concept that cannot be used with incomplete types: |
| template<typename T> |
| concept is_X = !std::is_empty_v<T> && std::is_same_v<X, T>; |
| |
| // A valid program-defined specialization: |
| template<typename T, typename C> requires is_X<T> |
| struct std::formatter<T, C> : std::formatter<int, C> { }; |
| |
| // Instantiate the program-defined formatter specialization: |
| auto s = sizeof(std::formatter<X, char>); |
