Deprecation errors are inconsistently triggered for underscore class aliases

Description

The following code:

<?php

namespace Foo {
    class __ {}
}

namespace Bar {
    class _ {} // Deprecated
}

namespace {
    class __ {}
    
    class_alias('Foo\__', 'Foo\_'); // Is this meant to be deprecated?
    class_alias('__', '_'); // Deprecated
}

namespace Baz {
    use Foo\_;
}

namespace Qux {
    use Foo\__ as _; // Is this meant to be deprecated?
}

Resulted in this output:

Deprecated: Using "_" as a class name is deprecated since 8.4 in /in/ZZMJs on line 8

Deprecated: Using "_" as a class alias is deprecated since 8.4 in /in/ZZMJs on line 15

But I expected this output instead:

Deprecated: Using "_" as a class name is deprecated since 8.4 in /in/ZZMJs on line 8

Deprecated: Using "_" as a class alias is deprecated since 8.4 in /in/ZZMJs on line 14

Deprecated: Using "_" as a class alias is deprecated since 8.4 in /in/ZZMJs on line 15

Deprecated: Using "_" as a class alias is deprecated since 8.4 in /in/ZZMJs on line 23

I encountered this issue while trying to migrate a large closed source project to PHP 8.4. The namespaced _ class was used as a wrapper for the gettext _ function (eg new _("string")), to delay performing the translation of cached content until the http response is stringified. The class had ~35k instantiations in source control and more instances in compressed + serialized database records. This made class aliases a potentially appealing solution, but I understand from @Girgias that these not emitting deprecation errors is an oversight.

PHP Version

8.4.1 - 8.4.6 on 3v4l

Operating System

No response

Commencez par exécuter la reproduction PHP 8.4 fournie et comparez le comportement de deprecation pour les déclarations de classes, les appels à class_alias() et l’alias namespaced use. Suivez les chemins de l’interpréteur qui gèrent les alias de classes et les imports de namespaces, puis ajoutez une couverture de régression montrant que les quatre cas attendus avec des underscores émettent des deprecations.