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Subject: Re: [PHP-DEV] Traits "implements" support
From: pierre-php@processus.org ("Pierre R.")

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Le 30/11/2020 à 16:19, Nikita Popov a écrit :
> Common misconception: It's not possible to rename methods of traits, you
> can only create aliases. That said, there's still an issue in that you
> might resolve a conflict in favor of an identically named method that uses
> a different signature.
>
> Note that Hack uses a "require implements" syntax instead, which makes it
> clear that the interface needs to be implemented by the using class:
> https://docs.hhvm.com/hack/classes/trait-and-interface-requirements
>
> Regards,
> Nikita

Sorry for the misconception/confusion.

Probably what's missing is something that looks like Java's interface 
with default methods, or something like that.

Very often you use traits to partially implement an interface, and leave 
room for classes using this "partial implementation" for inheriting from 
another class. It looks like multiple inheritance without being it. What 
is really needed when doing this is:

  * Your class using this trait must implement the interface,
  * The trait methods must be validated against the interface contract.

If I understand it well, when compiling PHP kinda copy-pastes the trait 
methods onto the class (trait doesn't exist as a type by itself, am I 
wrong?) then it validates the class, which solves the second point, 
trait methods are in the end, validated against the interface contract. 
What's missing here is the automatic interface usage, but more 
importantly, IDE support for the trait, and the information in the code 
that the trait does implement partially the interface (people who read 
the code cannot guess if it's mis-documented).

Regards,

Pierre


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