class CommentTypeDeleteForm

class CommentTypeDeleteForm extends EntityDeleteForm {
    
    /**
     * The comment manager service.
     *
     * @var \Drupal\comment\CommentManagerInterface
     */
    protected $commentManager;
    
    /**
     * A logger instance.
     *
     * @var \Psr\Log\LoggerInterface
     */
    protected $logger;
    
    /**
     * The entity being used by this form.
     *
     * @var \Drupal\comment\CommentTypeInterface
     */
    protected $entity;
    
    /**
     * Constructs a query factory object.
     *
     * @param \Drupal\comment\CommentManagerInterface $comment_manager
     *   The comment manager service.
     * @param \Psr\Log\LoggerInterface $logger
     *   A logger instance.
     */
    public function __construct(CommentManagerInterface $comment_manager, LoggerInterface $logger) {
        $this->commentManager = $comment_manager;
        $this->logger = $logger;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container) {
        return new static($container->get('comment.manager'), $container->get('logger.factory')
            ->get('comment'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildForm(array $form, FormStateInterface $form_state) {
        $comment_count = $this->entityTypeManager
            ->getStorage('comment')
            ->getQuery()
            ->accessCheck(FALSE)
            ->condition('comment_type', $this->entity
            ->id())
            ->count()
            ->execute();
        $entity_type = $this->entity
            ->getTargetEntityTypeId();
        $caption = '';
        foreach (array_keys($this->commentManager
            ->getFields($entity_type)) as $field_name) {
            
            /** @var \Drupal\field\FieldStorageConfigInterface $field_storage */
            if (($field_storage = FieldStorageConfig::loadByName($entity_type, $field_name)) && $field_storage->getSetting('comment_type') == $this->entity
                ->id() && !$field_storage->isDeleted()) {
                $caption .= '<p>' . $this->t('%label is used by the %field field on your site. You can not remove this comment type until you have removed the field.', [
                    '%label' => $this->entity
                        ->label(),
                    '%field' => $field_storage->label(),
                ]) . '</p>';
            }
        }
        if ($comment_count) {
            $caption .= '<p>' . $this->formatPlural($comment_count, '%label is used by 1 comment on your site. You can not remove this comment type until you have removed all of the %label comments.', '%label is used by @count comments on your site. You may not remove %label until you have removed all of the %label comments.', [
                '%label' => $this->entity
                    ->label(),
            ]) . '</p>';
        }
        if ($caption) {
            $form['description'] = [
                '#markup' => $caption,
            ];
            return $form;
        }
        else {
            return parent::buildForm($form, $form_state);
        }
    }

}