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Date: Thu, 24 Apr 2025 21:26:14 +0200
To: =?UTF-8?Q?Tim_D=C3=BCsterhus?= <tim@bastelstu.be>, internals@lists.php.net
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Subject: Re: [PHP-DEV] Re: RFC: Nested Classes
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From: rob@bottled.codes ("Rob Landers")

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On Thu, Apr 24, 2025, at 17:20, Tim D=C3=BCsterhus wrote:
> Hi
>=20
> On 4/24/25 17:09, Rob Landers wrote:
> > Thank you for your feedback! I think you would then have the problem=
 that was pointed out by Levi the other day; where you would then have a=
mbiguity. If you could have both private and public names in the same na=
mespace, then you would end up not knowing which one was being referred =
to.
>=20
> That is a design error in the RFC then.

This was very deliberate after much feedback and careful design. People =
were quite clear (including yourself, if I recall) that they didn't want=
 a new syntax. Since there is no new syntax, there is no way to tell (fr=
om the outside) whether A\B\C refers to a nested class or an outer class=
. That's by design and mirrors other languages and how they handle neste=
d classes.

>=20
> > Also, it is worth pointing out that private symbols are *not* "invis=
ible" or "non-existent" from outside classes. They emit their own errors=
: https://3v4l.org/PEGeA that indicate you tried to access something you=
 shouldn't be able to. This is different than when you try to access som=
ething that actually doesn't exist: https://3v4l.org/nWVPV
>=20
> Fair enough about the error message. You can also access them with=20
> Reflection or the Closure hack. They are nevertheless =E2=80=9Dnon-exi=
stent=E2=80=9D=20
> from the public API PoV: https://3v4l.org/Us6VV
>=20
>      <?php
>=20
>      class Foo {
> private string $bar =3D "foo";
> private function foo(): array {}
>      }
>=20
>      class Bar extends Foo {
>          private array $bar =3D [];
>=20
>          private function foo($foo): int {}
>      }
>=20
>      class Baz extends Bar {
>          public self $bar;
>      }
>=20
>      $baz =3D new Baz();
>      $baz->bar =3D $baz;
>=20
>      var_dump($baz);
>=20
> In subclasses I can =E2=80=9Credefine=E2=80=9D private properties or m=
ethods and they do=20
> not interact at all. Properties have separate storage locations and ca=
n=20
> have differing types. Methods do not need to have compatible signature=
s=20
> either.
>=20
> Best regards
> Tim D=C3=BCsterhus
>=20

I'm not sure what you are saying here. I mean, what you are saying is se=
lf-evident but I don't understand how it applies to nested classes. You =
can write the following without any issues:

class Foo {
  private class Bar {}
}

class Bar extends Foo {
  private class Bar extends Foo {}
}

And it will work just fine. You could even make the nested classes publi=
c if you want to, or one of them private and one of them public. As ment=
ioned in the RFC, the nested class is bound to the lexical scope of the =
class it is written in. So Foo\Bar and Bar\Bar are different classes alt=
ogether in the example above.

=E2=80=94 Rob
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<!DOCTYPE html><html><head><title></title></head><body><div><br></div><d=
iv><br></div><div>On Thu, Apr 24, 2025, at 17:20, Tim D=C3=BCsterhus wro=
te:</div><blockquote type=3D"cite" id=3D"qt" style=3D""><div>Hi</div><di=
v><br></div><div>On 4/24/25 17:09, Rob Landers wrote:</div><div>&gt; Tha=
nk you for your feedback! I think you would then have the problem that w=
as pointed out by Levi the other day; where you would then have ambiguit=
y. If you could have both private and public names in the same namespace=
, then you would end up not knowing which one was being referred to.</di=
v><div><br></div><div>That is a design error in the RFC then.</div></blo=
ckquote><div><br></div><div>This was very deliberate after much feedback=
 and careful design. People were quite clear (including yourself, if I r=
ecall) that they didn't want a new syntax. Since there is no new syntax,=
 there is no way to tell (from the outside) whether A\B\C refers to a ne=
sted class or an outer class. That's by design and mirrors other languag=
es and how they handle nested classes.<br></div><div><br></div><blockquo=
te type=3D"cite" id=3D"qt" style=3D""><div><br></div><div>&gt; Also, it =
is worth pointing out that private symbols are *not* "invisible" or "non=
-existent" from outside classes. They emit their own errors:&nbsp;<a hre=
f=3D"https://3v4l.org/PEGeA">https://3v4l.org/PEGeA</a> that indicate yo=
u tried to access something you shouldn't be able to. This is different =
than when you try to access something that actually doesn't exist:&nbsp;=
<a href=3D"https://3v4l.org/nWVPV">https://3v4l.org/nWVPV</a></div><div>=
<br></div><div>Fair enough about the error message. You can also access =
them with&nbsp;</div><div>Reflection or the Closure hack. They are never=
theless =E2=80=9Dnon-existent=E2=80=9D&nbsp;</div><div>from the public A=
PI PoV:&nbsp;<a href=3D"https://3v4l.org/Us6VV">https://3v4l.org/Us6VV</=
a></div><div><br></div><div>&nbsp;&nbsp;&nbsp;&nbsp; &lt;?php</div><div>=
<br></div><div>&nbsp;&nbsp;&nbsp;&nbsp; class Foo {</div><div>private st=
ring $bar =3D "foo";</div><div>private function foo(): array {}</div><di=
v>&nbsp;&nbsp;&nbsp;&nbsp; }</div><div><br></div><div>&nbsp;&nbsp;&nbsp;=
&nbsp; class Bar extends Foo {</div><div>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&=
nbsp;&nbsp;&nbsp; private array $bar =3D [];</div><div><br></div><div>&n=
bsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; private function foo($foo=
): int {}</div><div>&nbsp;&nbsp;&nbsp;&nbsp; }</div><div><br></div><div>=
&nbsp;&nbsp;&nbsp;&nbsp; class Baz extends Bar {</div><div>&nbsp;&nbsp;&=
nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; public self $bar;</div><div>&nbsp;&n=
bsp;&nbsp;&nbsp; }</div><div><br></div><div>&nbsp;&nbsp;&nbsp;&nbsp; $ba=
z =3D new Baz();</div><div>&nbsp;&nbsp;&nbsp;&nbsp; $baz-&gt;bar =3D $ba=
z;</div><div><br></div><div>&nbsp;&nbsp;&nbsp;&nbsp; var_dump($baz);</di=
v><div><br></div><div>In subclasses I can =E2=80=9Credefine=E2=80=9D pri=
vate properties or methods and they do&nbsp;</div><div>not interact at a=
ll. Properties have separate storage locations and can&nbsp;</div><div>h=
ave differing types. Methods do not need to have compatible signatures&n=
bsp;</div><div>either.</div><div><br></div><div>Best regards</div><div>T=
im D=C3=BCsterhus</div><div><br></div></blockquote><div><br></div><div>I=
'm not sure what you are saying here. I mean, what you are saying is sel=
f-evident but I don't understand how it applies to nested classes. You c=
an write the following without any issues:</div><div><br></div><div>clas=
s Foo {</div><div>&nbsp; private class Bar {}</div><div>}</div><div><br>=
</div><div>class Bar extends Foo {</div><div>&nbsp; private class Bar ex=
tends Foo {}</div><div>}</div><div><br></div><div>And it will work just =
fine. You could even make the nested classes public if you want to, or o=
ne of them private and one of them public. As mentioned in the RFC, the =
nested class is bound to the lexical scope of the class it is written in=
. So Foo\Bar and Bar\Bar are different classes altogether in the example=
 above.</div><div><br></div><div id=3D"sig121229152">=E2=80=94 Rob</div>=
</body></html>
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