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Date: Tue, 04 Jan 2022 19:17:01 -0600
To: "php internals" <internals@lists.php.net>
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Subject: Re: [PHP-DEV] RFC: Trait expects interface
From: larry@garfieldtech.com ("Larry Garfield")

On Tue, Jan 4, 2022, at 4:35 PM, Kirill Nesmeyanov wrote:
> Hello internals!
>
> Since =C2=ABtraits=C2=BB are often an indicator of not very good code =
and many=20
> may not use them quite correctly, for example, as helpers, I suggest=20
> adding support for the `expects`=C2=A0keyword to indicate that the tra=
it is=20
> part of the code decomposition taking into account ISP.
>
> For example:
> ```
> // Definition
>
> trait LoggerTrait expects LoggerInterface
> {
> =C2=A0 =C2=A0 // ...
> }
>
> // Usage
>
> class MyService
> {
> =C2=A0 =C2=A0 use LoggerTrait; // Fatal Error: Class=C2=A0MyService=20
> expects=C2=A0LoggerInterface to be implemented
> }
>
> class MyService2 implements=C2=A0LoggerInterface
> {
> =C2=A0 =C2=A0=C2=A0use LoggerTrait; // OK
> }
> ```
>
> How relevant do you think this idea/proposal is? And what possible=20
> problems or solutions will this entail in the future?

I can't say this has ever been an issue for me when using traits.  I've =
never had a trait that needed to be used by a class with a given interfa=
ce.  What I usually have is a trait that is a full or mostly implementat=
ion of an interface. So this would be much more useful to me:

trait LoggerTrait implements LoggerInterface { ... }

(Perhaps some way to indicate that it mostly implements, and the rest ar=
e abstract methods?  Or require the other methods to be explicitly abstr=
act?)

I think it's subtly different, as it approaches the question from the ot=
her direction.

--Larry Garfield