Field::canChangeField

private function canChangeField($type)
{
	$objectFieldList = new CListFieldList($this->iblockId);
	$fieldObject = $objectFieldList->getByID($this->params["FIELD_ID"]);
	if ($fieldObject)
	{
		$oldType = $fieldObject->getTypeID();
		if ($oldType != $type)
		{
			$this->errorCollection->setError(new Error("Field type can not be changed", self::ERROR_UPDATE_FIELD));
			return false;
		}
	}
	return true;
}