Corrections constructor

[sv-91]

2 correction:

1. std::forward
2. make_safe instead constructor

[AlexeyAB]

A few words why is it better to use make_safe instead constructor?

[sv-91]

Template parameter in the constructor sometimes causes a compilation error. Since the compiler cannot distinguish 2 constructors.

template<class B> A(B &&)

and

A(const A&)

https://mpark.github.io/programming/2014/06/07/beware-of-perfect-forwarding-constructors/

Instead of this method, you can try sfinae