Re: [Discussion] Implementing interfaces via traits

Hi Folks Thanks for the replies. If interface default methods are not entirely off the table, then I agree that's a far better option, for sure! I'll hold off on writing my arguments for them until a thread pops up, I think it makes a lot of sense though. So consider the idea of traits + interfaces on hold until there's clarity about interface default methods. Kind regards Brent On Tue, Sep 10, 2024 at 11:03 PM Gina P. Banyard <internals@gpb.moe> wrote: > On Tuesday, 27 August 2024 at 09:25, Brent Roose < > brent.roose@jetbrains.com> wrote: > > > Back to PHP, using traits as types seems impossible, since traits are a > compile-time copy/paste mechanism, which means there’s no type information > available about them at runtime. > > However, allowing traits to implement interfaces would solve this problem: > these interfaces would be copied over to classes during compile-time, and > the interface’s type information is available at runtime. On top of that, > traits already have well-defined rules for conflict resolution, so we > wouldn’t need any additional syntax to handle edge cases. > > > Traits are very ill-suited for this because everything from a trait can be > overwritten: > > > trait T { > public function foo(string $v): int {} > } > > class C { > use T; > > public function foo(array $v): string {} > } > > > This is valid code, now imagine T implements interface I: > > interface I { > > public foo(string $v): int; > > } > > C cannot implement I, moreover the conflict resolution mechanism just > exposes more problems as you can rename a method from a trait, or change > its visibility. > > > > - > > Even though it was not accepted, the interface default methods RFC > approached the problem from a different angle [4]. > - > > While a majority disagreed that interfaces should implement their own > methods directly, I remember it was a heavily debated topic, and believe > that approaching it from the other side might be easier to accept. > > > One part of the contention came that this feature was proposed in June of > 2023, weeks before feature freeze, and that no attempt at restricting the > implementation of the default implementation was made. > I still think default methods for interfaces make more sense then trying > to fix traits, but also default implementations only really make sense for > interfaces with multiple methods where one is a "core" method that remains > abstract and the default implementations rely on it to be implemented. > > > As such I am not really convinced of the utility of adding interface > support for traits considering all the issues I can foresee happenning. > > > Best regards, > > Gina P. Banyard > > > > > >