On Thursday, March 17th, 2022 at 11:38 AM, Nicolas Grekas <nicolas.grekas+php@gmail.com> wrote:
> Le jeu. 17 mars 2022 à 04:54, Saif Eddin Gmati azjezz@protonmail.com a
>
> écrit :
>
> > Hello Internals,
> >
> > As per my last email in the previous thread, i have started the vote for
> >
> > 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 to
>
> access private symbols, then I think that's fine: their problem; they know
>
> why they need to do so - not authors. Allowing authors to forcibly remove
>
> that capability from users is going too deep into removing power from users.
>
> Said another way, I don't think this solves any problem that authors face
>
> 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 that, 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 `Option` 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 previously, a third type could exist.
Authors previously got around this issue by adding methods on `Option` such 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 instance type.
Regards,
Saif.
