C++备忘录063：Overloading on Universal References gist of "Effective Modern C++"

Passing by value

Consider passing objects by value when you know you’ll copy them

struct S {
    S(std::string n) {   // replace T&& ctor
    : name(std::move(n)) {}

    std::string name;
};

Use Tag dispatch

struct S {
    template <typename T, typename std::enable_if_t<
            !std::is_same_v<S, std::decay_t<T>>>
    >
    S(T&& n);
};

Solving the derived class ctor problem, change it to

struct S {
    template <typename T, typename std::enable_if_t<
            !std::is_base_of<S, std::decay_t<T>>>
    >
    S(T&& n);
};

To distinguish it from other constructors

struct S {
    template <typename T, typename std::enable_if_t<
            !std::is_base_of<Person, std::decay_t<T>>
            &&
            !std::is_integral<std::remove_reference_t<T>>
    >>
    S(T&& n): name(std::forward<T>(n)) {
        static_cast(std::is_constructible<std::string, T>); // gives a better error message
    }

    S(int ind): name(foo(idx)) {}

    std::string name;
};