#include <iostream>
 
template <typename fT>
struct return_type;
 
template <typename R, typename ...Args>
struct return_type<R(*)(Args...)>
{
    using type = R;
};
 
struct A
{
    template <class T>
    using X = void();    
 
    template <class T>
    X<T> x;
};
 
template <typename T>
auto A::x() -> typename return_type< typename std::add_pointer<X<T>>::type >::type
{ 
    std::cout << __PRETTY_FUNCTION__ << std::endl;
}
 
int main()
{
    A a;
 
    a.x<void>();
    a.x<int>();
}

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