1 // PR c++/71105
2 // { dg-do compile { target c++14 } }
3 
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; };
9 
10 template <class F>
11 struct indirected : F {
12   indirected(F f) : F(f) {}
13   template <class I>
14   auto operator()(I i) -> decltype(declval<F&>()(*i)) {
15     return static_cast<F&>(*this)(*i);
16   }
17 };
18 
19 int main() {
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, "");
23 }
24