[RFC] Interface Default Methods

Hello, PHP Internals, I am moving my RFC for interface default methods to discussion: https://wiki.php.net/rfc/interface-default-methods. This can be a useful tool for a few reasons: 1. It can make implementing an interface easier when certain methods can be implemented by other methods in the interface. For example, if Countable had an isEmpty(): bool method, it could be implemented by doing $this->count() > 0. Of course, if an implementation can be more efficient, they are still free to implement it how they want. 2. It can mitigate BC breaks in some cases. It's somewhat common for authors to want to expand new methods onto existing interfaces over time. Although this would still be a BC break, it moves it from a massive change (every single implementor must add something, even if it's a stub, or it will fail to compile) to a naming collision issue only (only classes which already had a method of the same name will fail to compile). There is prior art for this feature in both Java and C#. There may be other languages, but I was aware of at least these. Note that the RFC links to a partial implementation. If there are two or more interfaces with default methods of the same shape (name, args, etc) and a class implements both interfaces and doesn't provide a concrete implementation, which default implementation should be chosen? There is a proposal for resolving this in some cases which is modelled after Java's implementation, but it isn't implemented. Thank you for your time. I look forward to productive feedback. Levi Morrison