Fixed, C++ (vc++) - rextester

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#include <iostream>
#include <tuple>

template <typename F, typename... T1s, typename T2>
auto detect(F&& f, std::tuple<T1s...>&&, T2&&) -> decltype(f(std::declval<T1s>()...));
template <typename F, typename T1, typename... T2s>
auto detect(F&& f, T1&&, std::tuple<T2s...>&&) -> decltype(f(std::declval<T2s>()...));

template<typename T>
struct Printer
{
    T fn;
 
    explicit Printer(T _fn)
        : fn(std::move(_fn))
    {
    }
 
   //das print, falls fn 1 Parameter nimmt
    template <typename U>
    auto print_(U& fn) -> decltype(fn(1))
    {
        return fn(1);
    }
 
    //das print, falls fn 2 Parameter nimmt
    template <typename U, int = 0>
    auto print_(U& fn) -> decltype(fn(1, 2))
    {
        return fn(1, 2);
    }
    
    auto print() {return print_(fn);}
    
    static int get_source();
    static T get_function();
              
    using value_type = decltype(detect(get_function(), std::make_tuple(get_source()),
                                                       std::make_tuple(get_source(), 0)));

};
int main()
{
    auto fn = [](auto&& x) { std::cout << x; return 1; };
    Printer<decltype(fn)>(fn).print();
 
    auto fn2 = [](auto&& x, auto&& y) { std::cout << x << y; return 2; };
    Printer<decltype(fn2)>(fn2).print();

Printer<decltype(fn2)>::value_type x = 4;
    (void)x;
}

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Compilation time: 2,36 sec, absolute running time: 0,33 sec, absolute service time: 2,71 sec