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Date: Mon, 31 Mar 2025 21:45:13 +0200
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Subject: [PHP-DEV] RFC: Nested Classes (was: short and inner classes)
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From: rob@bottled.codes ("Rob Landers")

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Hello internals,

I have significantly revamped the RFC (again). Key changes to the RFC:

1. More (realistic) examples,
2. Since enums are basically specialized classes, they are allowed to 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; but no=
t 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 cla=
ss 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 Outer\I=
nner.

- You cannot simply refer to parent:>Inner, you have to explicitly ask f=
or the parent by name: SomeParentClass\Inner.=20

A draft implementation (which is more of a proof-of-concept) is availabl=
e on GitHub.
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<!DOCTYPE html><html><head><title></title><style type=3D"text/css">p.Mso=
Normal,p.MsoNoSpacing{margin:0}=0Ap.MsoNormal,p.MsoNoSpacing{margin:0}=0A=
p.MsoNormal,p.MsoNoSpacing{margin:0}</style></head><body><div>Hello inte=
rnals,<br></div><div><br></div><div>I have significantly revamped the RF=
C (again). Key changes to the RFC:<br></div><div><br></div><div>1. More =
(realistic) examples,<br></div><div>2. Since enums are basically special=
ized classes, they are allowed to be nested as well (hat tip to Reddit),=
<br></div><div>3. Using backslash as the class separator,<br></div><div>=
4. Proper scoping (and shadowing),<br></div><div>5. Nesting is allowed i=
n interfaces and enums as well as classes; but not traits,<br></div><div=
>6. (Hopefully) Clearer wording,</div><div>7. Nesting in traits, or nest=
ed traits, are future scope,<br></div><div>8. Nested interfaces are futu=
re scope too.</div><div><br></div><div>Some benefits of using \ as a sep=
arator:<br></div><div><br></div><div>- a simple name can refer to nested=
 classes:<br></div><div><br></div><div>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:<br></div><div><br></div><div>class =
Outer {<br></div><div>&nbsp; class Inner {}<br></div><div>&nbsp; public =
function foo(Inner $inner) {}<br></div><div>}<br></div><div><br></div><d=
iv>- Standard =E2=80=9Cuse=E2=80=9D statements can alias them:<br></div>=
<div><br></div><div>use Outer\Inner as Inner;<br></div><div><br></div><d=
iv>But it also has some draw backs:<br></div><div><br></div><div>- The e=
ngine doesn=E2=80=99t know that Outer\Inner is a nested class and autolo=
aders will have to account for that. It will only ask for Outer\Inner.<b=
r></div><div><br></div><div>- You cannot simply refer to parent:&gt;Inne=
r, you have to explicitly ask for the parent by name: SomeParentClass\In=
ner.&nbsp;<br></div><div><br></div><div>A draft implementation (which is=
 more of a proof-of-concept) is available on GitHub.</div></body></html>
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