MAGETWO-32710: Code micro-optimizations

 - PHPCS sniff

Author: Ievgen Shakhsuvarov

dev/tests/static/framework/Magento/Sniffs/MicroOptimizations/IsNullSniff.php

@@ -0,0 +1,36 @@
+<?php
+/**
+ * Copyright © 2015 Magento. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+namespace Magento\Sniffs\MicroOptimizations;
+
+use PHP_CodeSniffer_File;
+use PHP_CodeSniffer_Sniff;
+
+class IsNullSniff implements PHP_CodeSniffer_Sniff
+{
+    /**
+     * @var string
+     */
+    protected $blacklist = 'is_null';
+
+    /**
+     * @inheritdoc
+     */
+    public function register()
+    {
+        return [T_STRING];
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function process(PHP_CodeSniffer_File $sourceFile, $stackPtr)
+    {
+        $tokens = $sourceFile->getTokens();
+        if ($tokens[$stackPtr]['content'] === $this->blacklist) {
+            $sourceFile->addError("is_null should be avoided. Use strict comparison instead.", $stackPtr);
+        }
+    }
+}