MAGETWO-33664: Refactor Sales module to use mutable data object interfaces

 - fixes per code review

Author: Mike Weis

app/code/Magento/Sales/Api/Data/OrderItemInterface.php

@@ -857,7 +857,7 @@ public function getProductOptions();
      * @param string[] $productOptions
      * @return $this
      */
-    public function setProductOptions($productOptions);
+    public function setProductOptions(array $productOptions = null);
 
     /**
      * Gets the product type for the order item.
@@ -1068,7 +1068,7 @@ public function getParentItem();
      * @param \Magento\Sales\Api\Data\OrderItemInterface $parentItem
      * @return $this
      */
-    public function setParentItem($parentItem);
+    public function setParentItem(\Magento\Sales\Api\Data\OrderItemInterface $parentItem);
 
     /**
      * Sets the updated-at timestamp for the order item.

app/code/Magento/Sales/Model/Order/Item.php

@@ -150,10 +150,10 @@ protected function _construct()
     /**
      * Set parent item
      *
-     * @param Item $item
+     * @param \Magento\Sales\Api\Data\OrderItemInterface $item
      * @return $this
      */
-    public function setParentItem($item)
+    public function setParentItem(\Magento\Sales\Api\Data\OrderItemInterface $item)
     {
         if ($item) {
             $this->setData(OrderItemInterface::PARENT_ITEM, $item);
@@ -453,7 +453,7 @@ public function getOriginalPrice()
      * @param array $options
      * @return $this
      */
-    public function setProductOptions($options)
+    public function setProductOptions(array $options = null)
     {
         $this->setData('product_options', $options);
         return $this;