[RFC] Allow object keys in arrays

Hi internals, I would like to present a draft RFC for allowing object keys in arrays: https://wiki.php.net/rfc/object_keys_in_arrays The specification in the RFC is incomplete, and primarily focussed on what impact this has from an internal perspective. https://github.com/php/php-src/pull/6588 is a draft implementation that illustrates the necessary changes. The primary motivation, and reason why I am looking into this now, is that the current enum proposal is based on objects, and I consider it somewhat important that enum values can also work as array keys. From a technical perspective, this also lays the groundwork for supporting other key types in the future, e.g. if we wish to switch PHP to use arbitrary-precision integers. Regards, Nikita