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Date: Fri, 19 Feb 2016 19:34:03 +0000
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To: Kevin Gessner <kgessner@etsy.com>
Cc: Nikita Popov <nikita.ppv@gmail.com>, PHP internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=047d7b2e75fe5b5f98052c2491a2
Subject: Re: [PHP-DEV] [RFC] Traits with interfaces
From: chasepeeler@gmail.com (Chase Peeler)

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On Fri, Feb 19, 2016 at 2:13 PM Kevin Gessner <kgessner@etsy.com> wrote:

> On Thu, Feb 18, 2016 at 2:16 PM, Chase Peeler <chasepeeler@gmail.com>
> wrote:
>
>> On Thu, Feb 18, 2016 at 1:29 PM Nikita Popov <nikita.ppv@gmail.com>
>> wrote:
>>
> HHVM already supports "trait Foo implements Iface" with the semantics that
>>> the interface is also implemented by the using class.
>>>
>>> Additionally HHVM supports a notion of "require implements Iface" which
>>> means that the using class must implement this interface.
>>>
>>
> This was mentioned in the original traits RFC, but never got voted or
> implemented:
> https://wiki.php.net/rfc/horizontalreuse#requiring_composing_class_to_implement_interface
>
> It's orthogonal to this RFC.
>
>
>>
>>> Why should it matter if the class using the trait actually implements
>> the interface? If the person just wants the functionality, but, for
>> whatever reason, doesn't want to actually implement the interface, why
>> should it matter?
>>
>> I think the trait should HELP the person implementing an interface. The
>> trait should be able to say (whether via comments or an engine enforceable
>> construct) "Hey, I've done everything needed for you to implement this
>> interface" but, at no time, should the trait force the class utilizing it
>> to interact (via extend or implement or use) a 3rd artifact.
>>
>> trait foo implements myinterface {}
>> class bar { use foo;}
>> class baz implements myinterface { use foo;}
>>
>> Both of the above should be legal, and $myBar instanceof myinterface
>> should return false;
>>
>
> This is Proposal 1 in the new draft of my RFC:
> https://wiki.php.net/rfc/traits-with-interfaces
>
> Does that proposal sound like what you'd want?
>
> I don't really have any objections to proposal 1. Part of me would still
like to see a different keyword used, but I don't think that's a huge deal.
I think the important part is not propagating the implementation (proposal
2).

My comments above, however, were more in relation to the HHVM notion of
"requires implement interface" which I don't think either proposal does.


> Cheers
> -- Kevin
>
>> --
-- Chase
chasepeeler@gmail.com

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