psalm/docs/running_psalm/issues/PrivateFinalMethod.md

PrivateFinalMethod

Emitted when a class defines private final method. PHP 8.0+ emits a warning when it sees private final method (except __construct where it's allowed), and allows redefinition in child classes (effectively ignoring final modifier). Before PHP 8.0, final was respected in this case.

<?php
class Foo {
    final private function baz(): void {}
}

Why this is bad

It causes a warning, and behavior differs between versions.