Method on_key

include/boost/json/detail/parse_into.hpp:112–112

    bool on_object_end( system::error_code& ) { BOOST_ASSERT( false ); return false; }
    bool on_key_part( system::error_code& ec, string_view ) { BOOST_JSON_FAIL( ec, E ); return false; }
    bool on_key( system::error_code& ec, string_view ) { BOOST_JSON_FAIL( ec, E ); return false; }
    // LCOV_EXCL_STOP
};