[php-src] Issue #7821: Can't use inherited constant value via 'self' in enum case value

Issue: https://github.com/php/php-src/issues/7821 Comment Author: nikic The problem here is that we compute a value to case table during compilation and all values must be known at that time. This happens pre-inheritance, so self::DEFAULT_VALUE is unknown at the time. This is unfortunate from a language design perspective, because what exactly can be evaluated during compilation and what can't is essentially an implementation detail (and may depend on whether opcache is used or not). I think it should be possible to make this part of inheritance instead, which should allow us to evaluate all expressions. It would also delay some error reporting (about duplicate case values) to that point.