Some PHPStan fixes

app/Mage.php

@@ -526,7 +526,7 @@ public static function getModel($modelClass = '', $arguments = [])
      *
      * @param   string $modelClass
      * @param   array $arguments
-     * @return  Mage_Core_Model_Abstract
+     * @return  Mage_Core_Model_Abstract|false
      */
     public static function getSingleton($modelClass = '', array $arguments = [])
     {

app/code/core/Mage/Adminhtml/Block/System/Config/Form.php

@@ -229,6 +229,7 @@ protected function _getDependence()
      * @param Varien_Simplexml_Element $section
      * @param string $fieldPrefix
      * @param string $labelPrefix
+     * @throw Mage_Core_Exception
      * @return $this
      */
     public function initFields($fieldset, $group, $section, $fieldPrefix = '', $labelPrefix = '')
@@ -425,21 +426,30 @@ public function initFields($fieldset, $group, $section, $fieldPrefix = '', $labe
                     }
 
                     $sourceModel = Mage::getSingleton($factoryName);
+                    if (!$sourceModel) {
+                        Mage::throwException("Source model '{$factoryName}' is not found");
+                    }
                     if ($sourceModel instanceof Varien_Object) {
                         $sourceModel->setPath($path);
                     }
+
+                    $optionArray = [];
                     if ($method) {
                         if ($fieldType == 'multiselect') {
                             $optionArray = $sourceModel->$method();
                         } else {
-                            $optionArray = [];
                             foreach ($sourceModel->$method() as $value => $label) {
                                 $optionArray[] = ['label' => $label, 'value' => $value];
                             }
                         }
                     } else {
-                        $optionArray = $sourceModel->toOptionArray($fieldType == 'multiselect');
+                        if (method_exists($sourceModel, 'toOptionArray')) {
+                            $optionArray = $sourceModel->toOptionArray($fieldType == 'multiselect');
+                        } else {
+                            Mage::throwException("Missing method 'toOptionArray()' in source model '{$factoryName}'");
+                        }
                     }
+
                     $field->setValues($optionArray);
                 }
             }
@@ -637,9 +647,9 @@ public function getScope()
      */
     public function getScopeLabel($element)
     {
-        if ($element->show_in_store == 1) {
+        if ((int)$element->show_in_store === 1) {
             return $this->_scopeLabels[self::SCOPE_STORES];
-        } elseif ($element->show_in_website == 1) {
+        } elseif ((int)$element->show_in_website === 1) {
             return $this->_scopeLabels[self::SCOPE_WEBSITES];
         }
         return $this->_scopeLabels[self::SCOPE_DEFAULT];

app/code/core/Mage/Catalog/Helper/Product/Flat.php

@@ -89,21 +89,24 @@ class Mage_Catalog_Helper_Product_Flat extends Mage_Catalog_Helper_Flat_Abstract
     /**
      * Old Catalog Product Flat forced status
      *
-     * @var bool
+     * @var bool|null
      */
     protected $_forceFlatStatusOld;
 
     /**
      * Retrieve Catalog Product Flat Flag object
      *
      * @return Mage_Catalog_Model_Product_Flat_Flag
+     * @throws Mage_Core_Exception
      */
     public function getFlag()
     {
         if (is_null($this->_flagObject)) {
             $className = (string)Mage::getConfig()->getNode(self::XML_PATH_FLAT_FLAG);
-            $this->_flagObject = Mage::getSingleton($className)
-                ->loadSelf();
+            /** @var Mage_Catalog_Model_Product_Flat_Flag $classInstance */
+            $classInstance = Mage::getSingleton($className);
+            $this->_flagObject = $classInstance;
+            $this->_flagObject->loadSelf();
         }
         return $this->_flagObject;
     }

app/code/core/Mage/CatalogIndex/Model/Retreiver.php

@@ -87,7 +87,8 @@ protected function _construct()
      * Returns data retriever model by specified product type
      *
      * @param string $type
-     * @return Mage_CatalogIndex_Model_Data_Abstract
+     * @return Mage_CatalogIndex_Model_Data_Abstract|false
+     * @throws Mage_Core_Exception
      */
     public function getRetreiver($type)
     {

app/code/core/Mage/Oauth/controllers/Customer/TokenController.php

@@ -40,7 +40,7 @@ class Mage_Oauth_Customer_TokenController extends Mage_Core_Controller_Front_Act
     /**
      * Customer session model
      *
-     * @var Mage_Customer_Model_Session
+     * @var string
      */
     protected $_sessionName = 'customer/session';
 
@@ -52,7 +52,9 @@ class Mage_Oauth_Customer_TokenController extends Mage_Core_Controller_Front_Act
     public function preDispatch()
     {
         parent::preDispatch();
-        $this->_session = Mage::getSingleton($this->_sessionName);
+        /** @var Mage_Customer_Model_Session $classInstance */
+        $classInstance = Mage::getSingleton($this->_sessionName);
+        $this->_session = $classInstance;
         if (!$this->_session->authenticate($this)) {
             $this->setFlag('', self::FLAG_NO_DISPATCH, true);
         }

app/code/core/Mage/Paypal/Controller/Express/Abstract.php

@@ -39,7 +39,7 @@ abstract class Mage_Paypal_Controller_Express_Abstract extends Mage_Core_Control
     protected $_config = null;
 
     /**
-     * @var Mage_Sales_Model_Quote
+     * @var Mage_Sales_Model_Quote|false
      */
     protected $_quote = false;
 
@@ -64,7 +64,9 @@ abstract class Mage_Paypal_Controller_Express_Abstract extends Mage_Core_Control
     protected function _construct()
     {
         parent::_construct();
-        $this->_config = Mage::getModel($this->_configType, [$this->_configMethod]);
+        /** @var Mage_Paypal_Model_Config $classInstance */
+        $classInstance = Mage::getModel($this->_configType, [$this->_configMethod]);
+        $this->_config = $classInstance;
     }
 
     /**
@@ -457,11 +459,13 @@ protected function _initCheckout()
             $this->getResponse()->setHeader('HTTP/1.1', '403 Forbidden');
             Mage::throwException(Mage::helper('paypal')->__('Unable to initialize Express Checkout.'));
         }
-        $this->_checkout = Mage::getSingleton($this->_checkoutType, [
+
+        /** @var Mage_Paypal_Model_Express_Checkout $classInstance */
+        $classInstance = Mage::getSingleton($this->_checkoutType, [
             'config' => $this->_config,
             'quote'  => $quote,
         ]);
-
+        $this->_checkout = $classInstance;
         return $this->_checkout;
     }
 
@@ -470,7 +474,7 @@ protected function _initCheckout()
      * Combined getter/setter
      *
      * @param string $setToken
-     * @return Mage_Paypal_ExpressController|string
+     * @return $this|string
      */
     protected function _initToken($setToken = null)
     {

app/code/core/Mage/Paypal/Model/Api/Abstract.php

@@ -382,12 +382,12 @@ protected function _importFromResponse(array $privateResponseMap, array $respons
      *
      * @param array &$request
      * @param int $i
-     * @return true|bool
+     * @return bool
      */
     protected function _exportLineItems(array &$request, $i = 0)
     {
         if (!$this->_cart) {
-            return;
+            return false;
         }
 
         // always add cart totals, even if line items are not requested
@@ -403,9 +403,9 @@ protected function _exportLineItems(array &$request, $i = 0)
         // add cart line items
         $items = $this->_cart->getItems();
         if (empty($items) || !$this->getIsLineItemsEnabled()) {
-            return;
+            return false;
         }
-        $result = null;
+        $result = false;
         foreach ($items as $item) {
             foreach ($this->_lineItemExportItemsFormat as $publicKey => $privateFormat) {
                 $result = true;

app/code/core/Mage/Paypal/Model/Api/Standard.php

@@ -187,12 +187,12 @@ public function debugRequest($request)
      *
      * @param array $request
      * @param int $i
-     * @return true|null
+     * @return bool
      */
     protected function _exportLineItems(array &$request, $i = 1)
     {
         if (!$this->_cart) {
-            return;
+            return false;
         }
         if ($this->getIsLineItemsEnabled()) {
             $this->_cart->isShippingAsItem(true);

lib/Varien/Image/Adapter/Gd2.php

@@ -109,7 +109,7 @@ protected function _convertToByte($memoryValue)
         }
         if (preg_match('~^([1-9][0-9]*)[\s]*(k|m|g)b?$~i', $memoryValue, $matches)) {
             $option = strtolower($matches[2]);
-            $memoryValue = $matches[1];
+            $memoryValue = (int)$matches[1];
             switch ($option) {
                 case 'g':
                     $memoryValue *= 1024;

lib/Varien/Io/File.php

@@ -70,7 +70,7 @@ class Varien_Io_File extends Varien_Io_Abstract
     /**
      * Stream open file pointer
      *
-     * @var resource
+     * @var resource|null
      */
     protected $_streamHandler;
 

lib/Varien/Object/Cache.php

@@ -31,7 +31,7 @@ class Varien_Object_Cache
     /**
      * Singleton instance
      *
-     * @var Varien_Object_Cache
+     * @var Varien_Object_Cache|null
      */
     protected static $_instance;
 
@@ -91,6 +91,11 @@ class Varien_Object_Cache
      */
     protected $_objectReferences = [];
 
+    /**
+     * @var array
+     */
+    protected $_referencesByObject = [];
+
     /**
      * Debug data such as backtrace per class
      *
@@ -196,7 +201,7 @@ public function reference($refName, $idx)
             foreach ($refName as $ref) {
                 $this->reference($ref, $idx);
             }
-            return;
+            return false;
         }
 
         if (isset($this->_references[$refName])) {
@@ -243,7 +248,7 @@ public function delete($idx)
         }
 
         if (isset($this->_objectReferences[$idx])) {
-            foreach ($references as $r => $dummy) {
+            foreach ($this->_references as $r => $dummy) {
                 unset($this->_references[$r]);
             }
             unset($this->_objectReferences[$idx]);
@@ -345,7 +350,7 @@ public function findByTags($tags)
                 if (isset($objects[$idx])) {
                     continue;
                 }
-                $objects[$ids] = $this->load($idx);
+                $objects[$idx] = $this->load($idx);
             }
         }
         return $objects;
@@ -375,7 +380,7 @@ public function debug($idx, $object = null)
             $debug[$i] = [
                 'file'     => isset($step['file']) ? $step['file'] : null,
                 'line'     => isset($step['line']) ? $step['line'] : null,
-                'function' => isset($step['function']) ? $step['function'] : null,
+                'function' => $step['function'],
             ];
         }
         $this->_debug[$idx] = $debug;

lib/Varien/Object/Mapper.php

@@ -105,6 +105,7 @@ public static function &accumulateByMap($from, $to, array $map, array $defaults
                     $to[$keyTo] = $value;
                 }
             } elseif ($toIsVO) {
+                /** @var Varien_Object $to */
                 if (!$to->hasData($keyTo)) {
                     $to->$set($keyTo, $value);
                 }