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