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Date: Sat, 24 Apr 2021 16:59:02 +0100
To: =?UTF-8?Q?=22Olle_H=C3=A4rstedt=22?= <olleharstedt@gmail.com>
Cc: "Pierre" <pierre-php@processus.org>,
	"Saif Eddin Gmati" <azjezz@protonmail.com>,
	"PHP Internals" <internals@lists.php.net>
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Subject: Re: [PHP-DEV] [RFC][Draft] Sealed Classes
From: azjezz@void.tn (Saif Eddin Gmati)

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> Doesn't this violate the principle: It should be possible to add new feat=
ures without touching old code?=20



This depends on which syntax is picked, both `for` and attribute syntax wil=
l be completely BC.



using `sealed`+`permits` or `permits` only will result in these keywords be=
ing reserved, so classes named `Sealed` or `Permits` will not work in PHP 8=
.1.

=20

> Isn't namespace-internal access a better feature for the same purpose? Th=
at is, only allows a class to be extended within the same namespace.=20



No, this is a different feature, sealed classes can permit classes in a com=
pletely different namespace, and restrict inheritance to a per-defined list=
 of classes.



If we would allow inheritance in the same namespace, it's extremely easy to=
 get around it:



```

namespace Lib {

=C2=A0 abstract class MyProxy implements PrivateFooInterface {}

}



namespace App {

=C2=A0 class MyFooImplementation extends \Lib\MyProxy {

=C2=A0=C2=A0=C2=A0 // ...

=C2=A0 }

}

```



while it is possible to get around sealed, or even final keywords ( https:/=
/github.com/dg/bypass-finals/blob/master/src/BypassFinals.php ), bypassing =
private classes/interface is much easier, and doesn't require any hacks.











---- On Sat, 24 Apr 2021 16:52:20 +0100 Olle H=C3=A4rstedt <olleharstedt@gm=
ail.com> wrote ----



2021-04-24 12:56 GMT, Pierre <mailto:pierre-php@processus.org>:=20
> Le 24/04/2021 =C3=A0 12:55, Saif Eddin Gmati a =C3=A9crit :=20
>> Hello Internals,=20
>>=20
>> I'm sending this email to open discussion about sealed classes,=20
>> interfaces, and traits feature for PHP 8.1.=20
>>=20
>> I have create a Draft RFC here:=20
>> https://wiki.php.net/rfc/sealed_classes=20
>> <https://wiki.php.net/rfc/sealed_classes>=20
>>=20
>> A major concern for few people have been the syntax, in which it=20
>> introduces 2 new keywords into the languages, therefor, i have added a=
=20
>> section about alternative syntax which could be used to avoid this=20
>> problem.=20
>>=20
>> Regards,=20
>>=20
>> Saif.=20
=20
1) Doesn't this violate the principle: It should be possible to add=20
new features without touching old code?=20
=20
2) Isn't namespace-internal access a better feature for the same=20
purpose? That is, only allows a class to be extended within the same=20
namespace.=20
=20
Olle=20
=20
--=20
PHP Internals - PHP Runtime Development Mailing List=20
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