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Date: Tue, 23 Feb 2016 09:48:38 +0000
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To: PHP Internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=047d7b33dc5092057b052c6cda8c
Subject: Re: [PHP-DEV] Re: [RFC] Traits with interfaces
From: t.carnage@gmail.com (Chris Riley)

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On 23 February 2016 at 00:37, Alex Bowers <bowersbros@gmail.com> wrote:

> Would a fair solution to this be having the using class define whether to
> inherit the implementations? Perhaps a new keyword akin to 'propagated', so
> the code will read
>
> Class Foo {
>    Use propagated TraitName;
> }
>
> Only then will the implementations from that trait bubble through. If it
> isn't declared then the implementations are not visible. This should keep
> all backwards compatibility and keep code readable since now we can
> immediately tell which traits being used do we want the implementations for
> in the main class.
> On 22 Feb 2016 20:19, "Kevin Gessner" <kgessner@etsy.com> wrote:
>
> > On Thu, Feb 18, 2016 at 4:13 PM, Kevin Gessner <kgessner@etsy.com>
> wrote:
> >
> > > On Wed, Feb 17, 2016 at 2:05 PM, Kevin Gessner <kgessner@etsy.com>
> > wrote:
> > >
> > >> I've created a proper RFC wiki page here with the draft:
> > >> https://wiki.php.net/rfc/traits-with-interfaces
> > >>
> > >> It includes more detail and several example code snippets.  Thanks all
> > >> for your feedback so far.
> > >>
> > >
> > > I've just updated the RFC to v0.2, presenting two proposals to be voted
> > > separately: one to allow traits to declare and implement interfaces,
> and
> > a
> > > second (dependent on the first) to propagate interface declarations
> from
> > > traits to classes.
> > >
> >
> > I've created a php-src pull request for Proposal 1 of the RFC, allowing
> > traits to declare and implement interfaces:
> > https://github.com/php/php-src/pull/1773
> >
> > Reviews and feedback welcome!
> >
> > I haven't yet started on an implementation for Proposal 2.
> >
> > Cheers
> > -- Kevin
> >
>

This isn't such a great idea as it will cause some of traits functionality
to be broken: I can currently use a trait and alias its methods and change
their visibility. If a trait implements an interface which is copied onto
my class I can no longer do this as the compiler will throw a fatal error
for the class not correctly implementing the interface that got copied from
the trait.

If you decide to continue pursuing this RFC, I'd like to see some thought
given to the above; perhaps it could be as simple as not copying the
interface if aliases/visibility changes are made in the use or perhaps
something more complex which allows specifying which interfaces should be
copied into the class from the trait.

~C

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