std::experimental::future<T>:: operator=

From cppreference.com
std:: experimental :: future < T > & operator = ( std:: experimental :: future < T > && other ) noexcept ;
(1)
std:: experimental :: future < T > & operator = ( const std:: experimental :: future < T > & other ) = delete ;
(2)

Assigns the contents of another future object.

1) Releases any shared state and move-assigns the contents of other to * this . After the assignment, other. valid ( ) == false and this - > valid ( ) will yield the same value as other. valid ( ) before the assignment.
2) std::experimental::future is not CopyAssignable .

Parameters

other - a std::experimental::future that will transfer state to * this

Return value

* this