1 // PR c++/80691 2 // { dg-do compile { target c++11 } } 3 4 struct true_type { static constexpr bool value = true; }; 5 struct false_type { static constexpr bool value = false; }; 6 template<typename...> using void_t = void; 7 template<typename T> T&& declval(); 8 9 template<typename T, typename U, typename = void> 10 struct is_nonnarrowing_conversion : false_type {}; 11 12 template<typename T, typename U> 13 struct is_nonnarrowing_conversion<T, U, 14 void_t<decltype(T{ declval<U>() })>> : true_type {}; 15 16 template<typename T> 17 class wrapper 18 { 19 public: 20 wrapper(T) {} 21 }; 22 23 static_assert(!is_nonnarrowing_conversion<int, float>::value, ""); 24 static_assert(!is_nonnarrowing_conversion<wrapper<int>, float>::value, ""); 25