Consider the following code snippet.

 

    int x = 10;
    std::reference_wrapper<int> rx( x );
    std::swap( rx, x );
 

The compiler will issue an error because either rx can be implicitly converted to the type int or x can be implicitly converted to the type std::reference_wrapper<int>.

 

So a pair of questions are arising.

 

Should the constructor of the class template std::reference_wrapper be explicit?

What is the reason that the constructor is implicit? Is that so necessary?