how to make a template function like R f

now i want to create a function looked like f<void(int)>(args...),my code is:

template<typename T>
struct A{};

template<typename F>
A<F> f4();

template<typename R,typename... Args>
A<R(Args...)> f4<R(Args...)>() {
    return A<R(Args...)>();
}

but it does not work and vs gives error C2768

how can i do that?