Re: [RFC] Interface Default Methods

On Fri, Jun 16, 2023 at 11:51 AM Deleu <deleugyn@gmail.com> wrote: > > > On Thu, Jun 15, 2023 at 12:48 AM Levi Morrison via internals <internals@lists.php.net> > wrote: >> >> 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 >> >> -- >> PHP Internals - PHP Runtime Development Mailing List >> To unsubscribe, visit: https://www.php.net/unsub.php >> > > A question just occurred to me. Building up on the example of the RFC, is the following snippet > valid and would it behave as expected? > > ``` > interface Interface1 { > function method1() { echo __METHOD__ . "\n"; } > } > > interface Interface2 { > function method1() { echo __METHOD__ . "\n"; } > } > > class Class1 implements Interface1, Interface2 { > function method1() { > $result = Interface1::method1(); > > Interface2::method1(); > > return $result; > } > } > > $result = (new Class1())->method1(); > ``` > > > -- > Marco Deleu I'm not sure why you are saving null from Interface1::method1()'s implicit return and then returning it from inside Class1::method1, but yes, this is valid.