| // { dg-do compile { target c++17 } } |
| |
| #include <variant> |
| |
| // P2062R2 Inheriting from std::variant (resolving LWG 3052) |
| |
| #if __cpp_lib_variant < 202102L |
| #error __cpp_lib_variant has the wrong value in <variant> |
| #endif |
| |
| struct V : std::variant<int> { |
| using std::variant<int>::variant; |
| }; |
| |
| constexpr int |
| test01() |
| { |
| V v = 42; |
| return std::visit([](int&){ return 17; }, v); |
| } |
| static_assert( test01() == 17 ); |
| |
| constexpr int |
| test02() |
| { |
| const V c = 77; |
| std::variant<char*, long> x = 88L; |
| return std::visit([](auto&& a, auto&& b) { |
| if constexpr (std::is_same_v<decltype(a), const int&&>) |
| if constexpr (std::is_same_v<decltype(b), long&&>) |
| return 99; |
| return 0; |
| }, |
| std::move(c), std::move(x)); |
| } |
| static_assert( test02() == 99 ); |