sealed.internalClass

Code example

<?php declare(strict_types = 1);

namespace Vendor {
	/** @internal */
	class InternalChild {}
}

namespace App {
	/** @phpstan-sealed \Vendor\InternalChild */
	class MyBase {}
}

Why is it reported?

The @phpstan-sealed PHPDoc tag references a class that is marked as @internal. Internal classes are not part of the public API of their package and may change or be removed at any time. Referencing them in a @phpstan-sealed tag creates a dependency on an implementation detail that could break without notice.

How to fix it

Reference only public (non-internal) classes in @phpstan-sealed tags:

-/** @phpstan-sealed \Vendor\InternalChild */
+/** @phpstan-sealed \Vendor\PublicChild */
 class MyBase {}

If the class is internal to the same package, the error will not be reported. The @internal restriction only applies to cross-package usage.