Solving prblem with emplace_back and private constructor

private_constructor_eb.cpp

#include <vector>
#include <iostream>

class A
{
private:
    struct private_key {};
    // private constructor
    A(int a) :
        a(a)
    {
        std::cout << "A("<< a <<")" << std::endl;
    }

public:
    // indirectly (by private_key) private constructor
    A(int x, private_key&&) : A(x) {}

    A(A&& rhs)
    {
        std::cout << "A(A&&)" << std::endl;
        a = rhs.a;
        rhs.a = 0;
    }


    static std::vector<A> make()
    {
        std::vector<A> result;
        result.emplace_back(1, private_key());
        result.emplace_back(2, private_key());
        return result;
    }

private:
        int a;

};

int main()
{
    auto a {A::make()};
    return 0;
}