Add concrete type hints for product and category resources

Author: rogyar

app/code/Magento/Catalog/Model/Category.php

@@ -112,6 +112,11 @@ class Category extends \Magento\Catalog\Model\AbstractModel implements
      */
     protected $_url;
 
+    /**
+     * @var ResourceModel\Category
+     */
+    protected $_resource;
+
     /**
      * URL rewrite model
      *
@@ -332,6 +337,16 @@ protected function getCustomAttributesCodes()
         return $this->customAttributesCodes;
     }
 
+    /**
+     * @throws \Magento\Framework\Exception\LocalizedException
+     * @return \Magento\Catalog\Model\ResourceModel\Category
+     * @deprecated because resource models should be used directly
+     */
+    protected function _getResource()
+    {
+        return parent::_getResource();
+    }
+
     /**
      * Get flat resource model flag
      *

app/code/Magento/Catalog/Model/Product.php

@@ -118,6 +118,11 @@ class Product extends \Magento\Catalog\Model\AbstractModel implements
      */
     protected $_urlModel = null;
 
+    /**
+     * @var ResourceModel\Product
+     */
+    protected $_resource;
+
     /**
      * @var string
      */
@@ -482,6 +487,18 @@ protected function _construct()
         $this->_init(\Magento\Catalog\Model\ResourceModel\Product::class);
     }
 
+    /**
+     * Get resource instance
+     *
+     * @throws \Magento\Framework\Exception\LocalizedException
+     * @return \Magento\Catalog\Model\ResourceModel\Product
+     * @deprecated because resource models should be used directly
+     */
+    protected function _getResource()
+    {
+        return parent::_getResource();
+    }
+
     /**
      * Get a list of custom attribute codes that belongs to product attribute set. If attribute set not specified for
      * product will return all attribute codes