#include <cstddef>
#include <type_traits>
#include <iostream>
#include <string>

template <size_t N>
struct priority_tag : priority_tag<N-1> {};

template <>
struct priority_tag<0> {};

template <typename T, typename = decltype(std::declval<T>().toString())>
void print(T&& value, const priority_tag<2> &) {
    std::cout << value.toString() << "\n";
}

template <typename T>
void print(T&& value, const priority_tag<1> &) {
    std::cout << value << "\n";
}

template <typename T>
void print(T&& value) {
    print(std::forward<T>(value), priority_tag<2>{});
}

struct Foo {
    std::string toString() { return "Foo"; }
};
struct Bar {
    /* Doesn't have tOString, but does have an operator<< we can use. */
    friend std::ostream &operator<<(std::ostream &os, const Bar &b) {
        os << "Bar";
        return os;
    }
};

int main() {
    Foo f;
    Bar b;

    print(f);
    print(b);
}