I am sorry. I made an incorrect resume about the error. Nevertheless the questions about implicit constructor are actual.
 
 
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>Пятница, 26 марта 2021, 21:33 +03:00 от Vladimir Grigoriev via Std-Discussion <std-discussion_at_[hidden]>:
>
>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?
>
>You can meet me at http://cpp.forum24.ru/ or www.stackoverflow.com or http://ru.stackoverflow.com
>
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