|  | 
            Move-assign a basic_stream_file from a file
            of another executor type.
          
template< typename Executor1> constraint_t< is_convertible< Executor1, Executor >::value, basic_stream_file & > operator=( basic_stream_file< Executor1 > && other);
This assignment operator moves a stream file from one object to another.
                  The other basic_stream_file object
                  from which the move will occur.
                
            Following the move, the moved-from object is in the same state as if
            constructed using the basic_stream_file(const executor_type&)
            constructor.