private function compareFinalModifier()
{
$baseIsFinal = $this->base->isFinal();
$challengerIsFinal = $this->challenger->isFinal();
if ($baseIsFinal !== $challengerIsFinal) {
$message = $baseIsFinal ? 'unit is no longer final' : 'unit has become final';
$difference = new Difference($message);
$this->populateDifference($difference);
if ($challengerIsFinal) {
$difference->addTag(Difference::BC_BREAK);
}
$this->differences->add($difference);
}
}
