WooCommerce order types

class-wc-order-factory.php

<?php

            switch ( $item_type ) {
                case 'line_item':
                case 'product':
                    $classname = 'WC_Order_Item_Product';
                    break;
                case 'coupon':
                    $classname = 'WC_Order_Item_Coupon';
                    break;
                case 'fee':
                    $classname = 'WC_Order_Item_Fee';
                    break;
                case 'shipping':
                    $classname = 'WC_Order_Item_Shipping';
                    break;
                case 'tax':
                    $classname = 'WC_Order_Item_Tax';
                    break;
            }