Newsgroups: php.internals
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Xref: news.php.net php.internals:117354
Date: Thu, 17 Mar 2022 13:36:48 +0000
To: Nicolas Grekas <nicolas.grekas+php@gmail.com>
Cc: PHP Internals <internals@lists.php.net>
Reply-To: Saif Eddin Gmati <azjezz@protonmail.com>
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Subject: Re: [PHP-DEV] [RFC] [VOTE] Sealed Classes
From: azjezz@protonmail.com (Saif Eddin Gmati)

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On Thursday, March 17th, 2022 at 11:38 AM, Nicolas Grekas <nicolas.grekas+=
php@gmail.com> wrote:

> Le jeu. 17 mars 2022 =C3=A0 04:54, Saif Eddin Gmati azjezz@protonmail.co=
m a
> =


> =C3=A9crit :
> =


> > Hello Internals,
> > =


> > As per my last email in the previous thread, i have started the vote f=
or
> > =


> > sealed classes feature.
> > =


> > The vote will run for 2 weeks until March 31st 2022.
> > =


> > Discussion: https://externals.io/message/117173
> > =


> > Draft Discussion: https://externals.io/message/114116
> > =


> > RFC: https://wiki.php.net/rfc/sealed_classes
> =


> Hello Saif,
> =


> Thanks for the RFC.
> =


> I voted "no" because to me this closes extensibility in a hard way. If
> =


> users are fine ignoring an "@internal" annotation, or using reflection t=
o
> =


> access private symbols, then I think that's fine: their problem; they kn=
ow
> =


> why they need to do so - not authors. Allowing authors to forcibly remov=
e
> =


> that capability from users is going too deep into removing power from us=
ers.
> =


> Said another way, I don't think this solves any problem that authors fac=
e
> =


> in practice. As such I don't think this is worth the added language
> =


> complexity + removal of power.
> =


> Cheers,
> =


> Nicolas

Hello Nicolas,

> to me this closes extensibility in a hard way.

This is not necessarily true, we have `final` in PHP which does exactly th=
at, but `sealed` can still allow for extensibility, just from a different =
point, e.g:

```
sealed interface Option permits Some, None { }

interface Some extends Option {}
interface None extends Option {}
```

In this example, both `Some` and `None` are open for extension, but `Optio=
n` is closed for any type aside from `Some` and `None`.


> I don't think this solves any problem that authors face
in practice

It does!

Considering the `Option`/`Some`/`None` example above, given `Option`, now =
you are sure that it's either an instance of `Some` or `None`, where previ=
ously, a third type could exist.

Authors previously got around this issue by adding methods on `Option` suc=
h as `isSome()`/`isNone()`/`isSuccess()`/`isFailure()` .. etc

reference: https://github.com/azjezz/psl/tree/2.0.x/src/Psl/Result

Having sealed classes, ensures that there can't be a third type at runtime=
, and makes the `is*()` methods absolute, as now you can check the instanc=
e type.

Regards,

Saif.
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