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

まず、提供された PHP 8.4 の再現コードを実行し、クラス宣言、class_alias() の呼び出し、namespaced use alias に対する deprecation の動作を比較します。次に、クラスエイリアスと namespace import を処理するインタープリターの経路を追跡し、想定される 4 つすべてのアンダースコアケースで deprecation が発生することを示すリグレッションテストのカバレッジを追加します。