2 // { dg-do compile { target c++14 } }
4 template <typename T> T declval();
5 template <typename, typename> struct is_same
6 { static constexpr bool value = false; };
7 template <typename T> struct is_same<T, T>
8 { static constexpr bool value = true; };
11 struct indirected : F {
12 indirected(F f) : F(f) {}
14 auto operator()(I i) -> decltype(declval<F&>()(*i)) {
15 return static_cast<F&>(*this)(*i);
20 auto f = [=](auto i) { return i + i; };
21 auto i = indirected<decltype(f)>{f};
22 static_assert(is_same<decltype(i(declval<int*>())), int>::value, "");