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Date: Tue, 22 Apr 2025 19:30:00 +0200
To: "Levi Morrison" <levi.morrison@datadoghq.com>
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Subject: Re: [PHP-DEV] Re: RFC: Nested Classes (was: short and inner classes)
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From: rob@bottled.codes ("Rob Landers")

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On Tue, Apr 22, 2025, at 19:22, Levi Morrison wrote:
> On Sun, Apr 20, 2025 at 7:46=E2=80=AFAM Rob Landers <rob@bottled.codes=
> wrote:
> >
> > On Mon, Mar 31, 2025, at 21:45, Rob Landers wrote:
> >
> > Hello internals,
> >
> > I have significantly revamped the RFC (again). Key changes to the RF=
C:
> >
> > 1. More (realistic) examples,
> > 2. Since enums are basically specialized classes, they are allowed t=
o be nested as well (hat tip to Reddit),
> > 3. Using backslash as the class separator,
> > 4. Proper scoping (and shadowing),
> > 5. Nesting is allowed in interfaces and enums as well as classes; bu=
t not traits,
> > 6. (Hopefully) Clearer wording,
> > 7. Nesting in traits, or nested traits, are future scope,
> > 8. Nested interfaces are future scope too.
> >
> > Some benefits of using \ as a separator:
> >
> > - a simple name can refer to nested classes:
> >
> > Scope resolution was expanded to treat inner classes within the same=
 class as =E2=80=9Cin scope.=E2=80=9D This provides a more natural usage:
> >
> > class Outer {
> >   class Inner {}
> >   public function foo(Inner $inner) {}
> > }
> >
> > - Standard =E2=80=9Cuse=E2=80=9D statements can alias them:
> >
> > use Outer\Inner as Inner;
> >
> > But it also has some draw backs:
> >
> > - The engine doesn=E2=80=99t know that Outer\Inner is a nested class=
 and autoloaders will have to account for that. It will only ask for Out=
er\Inner.
> >
> > - You cannot simply refer to parent:>Inner, you have to explicitly a=
sk for the parent by name: SomeParentClass\Inner.
> >
> > A draft implementation (which is more of a proof-of-concept) is avai=
lable on GitHub.
> >
> >
> > Hello internals,
> >
> > As it seems that discussion has mostly died down, I'd like to put th=
is towards a vote starting on May 1, 2025.
> >
> > =E2=80=94 Rob
>=20
> I intend to vote no. Fundamentally, this proposal adds a form of
> "packaging" which only affects classes. There's no packaging for
> constants or functions, unless you put them onto a class to make them
> class constants and static methods. This is weird to me. I would
> prefer that we work out something more general.

Thank you for your feedback! It very much isn't packaging, this is close=
r to "friend" classes in C++ or nested classes in other languages (C#, K=
otlin, Swift, Java, etc). I do intend to focus on packaging (in-general)=
 in the near future though.

>=20
> I am also worried that naming collisions are possible. Something like =
this:
>=20
> ```php
> namespace A {
>      class B {}
> }
>=20
> namespace {
>     class A {
>         class B {}
>     }
> }
> ```
>=20
> Where `A\B` refers to two possible things. I don't like this, and to
> my knowledge, this type of confusion has not been possible in the
> past. Of course, feel free to point it out if so. Note that methods
> and properties of the same name are disambiguated by syntax, where
> here the syntax is the same.
>=20

I should update the RFC to include this case, thanks for pointing this o=
ut. This would cause the ole' "Cannot redeclare class A\B" error. There =
is not any ambiguity here.

=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 Tue, Apr 22, 2025, at 19:22, Levi Morrison wrote:</=
div><blockquote type=3D"cite" id=3D"qt" style=3D""><div>On Sun, Apr 20, =
2025 at 7:46=E2=80=AFAM Rob Landers &lt;<a href=3D"mailto:rob@bottled.co=
des">rob@bottled.codes</a>&gt; wrote:</div><div>&gt;</div><div>&gt; On M=
on, Mar 31, 2025, at 21:45, Rob Landers wrote:</div><div>&gt;</div><div>=
&gt; Hello internals,</div><div>&gt;</div><div>&gt; I have significantly=
 revamped the RFC (again). Key changes to the RFC:</div><div>&gt;</div><=
div>&gt; 1. More (realistic) examples,</div><div>&gt; 2. Since enums are=
 basically specialized classes, they are allowed to be nested as well (h=
at tip to Reddit),</div><div>&gt; 3. Using backslash as the class separa=
tor,</div><div>&gt; 4. Proper scoping (and shadowing),</div><div>&gt; 5.=
 Nesting is allowed in interfaces and enums as well as classes; but not =
traits,</div><div>&gt; 6. (Hopefully) Clearer wording,</div><div>&gt; 7.=
 Nesting in traits, or nested traits, are future scope,</div><div>&gt; 8=
. Nested interfaces are future scope too.</div><div>&gt;</div><div>&gt; =
Some benefits of using \ as a separator:</div><div>&gt;</div><div>&gt; -=
 a simple name can refer to nested classes:</div><div>&gt;</div><div>&gt=
; Scope resolution was expanded to treat inner classes within the same c=
lass as =E2=80=9Cin scope.=E2=80=9D This provides a more natural usage:<=
/div><div>&gt;</div><div>&gt; class Outer {</div><div>&gt;&nbsp;&nbsp; c=
lass Inner {}</div><div>&gt;&nbsp;&nbsp; public function foo(Inner $inne=
r) {}</div><div>&gt; }</div><div>&gt;</div><div>&gt; - Standard =E2=80=9C=
use=E2=80=9D statements can alias them:</div><div>&gt;</div><div>&gt; us=
e Outer\Inner as Inner;</div><div>&gt;</div><div>&gt; But it also has so=
me draw backs:</div><div>&gt;</div><div>&gt; - The engine doesn=E2=80=99=
t know that Outer\Inner is a nested class and autoloaders will have to a=
ccount for that. It will only ask for Outer\Inner.</div><div>&gt;</div><=
div>&gt; - You cannot simply refer to parent:&gt;Inner, you have to expl=
icitly ask for the parent by name: SomeParentClass\Inner.</div><div>&gt;=
</div><div>&gt; A draft implementation (which is more of a proof-of-conc=
ept) is available on GitHub.</div><div>&gt;</div><div>&gt;</div><div>&gt=
; Hello internals,</div><div>&gt;</div><div>&gt; As it seems that discus=
sion has mostly died down, I'd like to put this towards a vote starting =
on May 1, 2025.</div><div>&gt;</div><div>&gt; =E2=80=94 Rob</div><div><b=
r></div><div>I intend to vote no. Fundamentally, this proposal adds a fo=
rm of</div><div>"packaging" which only affects classes. There's no packa=
ging for</div><div>constants or functions, unless you put them onto a cl=
ass to make them</div><div>class constants and static methods. This is w=
eird to me. I would</div><div>prefer that we work out something more gen=
eral.</div></blockquote><div><br></div><div>Thank you for your feedback!=
 It very much isn't packaging, this is closer to "friend" classes in C++=
 or nested classes in other languages (C#, Kotlin, Swift, Java, etc). I =
do intend to focus on packaging (in-general) in the near future though.<=
/div><div><br></div><blockquote type=3D"cite" id=3D"qt" style=3D""><div>=
<br></div><div>I am also worried that naming collisions are possible. So=
mething like this:</div><div><br></div><div>```php</div><div>namespace A=
 {</div><div>&nbsp;&nbsp;&nbsp;&nbsp; class B {}</div><div>}</div><div><=
br></div><div>namespace {</div><div>&nbsp;&nbsp;&nbsp; class A {</div><d=
iv>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; class B {}</div><div>&nbsp=
;&nbsp;&nbsp; }</div><div>}</div><div>```</div><div><br></div><div>Where=
 `A\B` refers to two possible things. I don't like this, and to</div><di=
v>my knowledge, this type of confusion has not been possible in the</div=
><div>past. Of course, feel free to point it out if so. Note that method=
s</div><div>and properties of the same name are disambiguated by syntax,=
 where</div><div>here the syntax is the same.</div><div><br></div></bloc=
kquote><div><br></div><div>I should update the RFC to include this case,=
 thanks for pointing this out. This would cause the ole' "Cannot redecla=
re class A\B" error. There is not any ambiguity here.</div><div><br></di=
v><div id=3D"sig121229152">=E2=80=94 Rob</div></body></html>
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