Move-assign a basic_stream_file from another.

basic_stream_file & operator=(
    basic_stream_file && other);
  » more...

Move-assign a basic_stream_file from a file of another executor type.

template<
    typename Executor1>
constraint< is_convertible< Executor1, Executor >::value, basic_stream_file & >::type operator=(
    basic_stream_file< Executor1 > && other);
  » more...