Protected visibility in interface

Hello everyone, I would like to finish https://github.com/php/php-src/pull/5708 and the next step is RFC. Protected visibility in an interface should be supported to support non-public interfaces to be used together with instanceof operator in traits - example: https://github.com/php/php-src/pull/5708#issuecomment-644616936 I would like to hear your feedback if this feature is wanted and if there are any questions I should clarify. Michael