Delegate callable array handler to a utility class

src/main/php/PHPMD/Rule/UnusedPrivateMethod.php

@@ -25,6 +25,7 @@
 use PHPMD\Node\ASTNode;
 use PHPMD\Node\ClassNode;
 use PHPMD\Node\MethodNode;
+use PHPMD\Utility\CallableArray;
 use PHPMD\Utility\LastVariableWriting;
 use PHPMD\Utility\Seeker;
 use SplObjectStorage;
@@ -162,7 +163,8 @@ protected function removeCallableArrayRepresentations(ClassNode $class, array $m
     {
         foreach ($class->findChildrenOfTypeVariable() as $variable) {
             if ($this->isInstanceOfTheCurrentClass($class, $variable)) {
-                $method = $this->getMethodNameFromArraySecondElement($variable->getParent());
+                $method = CallableArray::fromFirstArrayElement($variable->getParent())
+                    ->getMethodNameFromArraySecondElement();
 
                 if ($method) {
                     unset($methods[strtolower($method)]);
@@ -173,33 +175,6 @@ protected function removeCallableArrayRepresentations(ClassNode $class, array $m
         return $methods;
     }
 
-    /**
-     * Return represented method name if the given element is a 2-items array
-     * and that the second one is a literal static string.
-     *
-     * @param ASTNode|null $parent
-     * @return string|null
-     */
-    protected function getMethodNameFromArraySecondElement($parent)
-    {
-        if ($parent instanceof ASTNode && $parent->isInstanceOf('ArrayElement')) {
-            $array = $parent->getParent();
-
-            if ($array instanceof ASTNode
-                && $array->isInstanceOf('Array')
-                && count($array->getChildren()) === 2
-            ) {
-                $secondElement = $array->getChild(1)->getChild(0);
-
-                if ($secondElement->isInstanceOf('Literal')) {
-                    return substr($secondElement->getImage(), 1, -1);
-                }
-            }
-        }
-
-        return null;
-    }
-
     /**
      * This method checks that the given method postfix is accessed on an
      * instance or static reference to the given class.

src/main/php/PHPMD/Utility/CallableArray.php

@@ -0,0 +1,79 @@
+<?php
+/**
+ * This file is part of PHP Mess Detector.
+ *
+ * Copyright (c) Manuel Pichler <mapi@phpmd.org>.
+ * All rights reserved.
+ *
+ * Licensed under BSD License
+ * For full copyright and license information, please see the LICENSE file.
+ * Redistributions of files must retain the above copyright notice.
+ *
+ * @author Manuel Pichler <mapi@phpmd.org>
+ * @copyright Manuel Pichler. All rights reserved.
+ * @license https://opensource.org/licenses/bsd-license.php BSD License
+ * @link http://phpmd.org/
+ */
+
+namespace PHPMD\Utility;
+
+use PHPMD\Node\ASTNode;
+
+/**
+ * Utility class to check and read array possibly representing callable method.
+ */
+final class CallableArray
+{
+    /** @var ASTNode|null */
+    private $array;
+
+    // TODO: should be (?ASTNode $array) when dropping PHP < 7.1
+    private function __construct(ASTNode $array = null)
+    {
+        $this->array = $array;
+    }
+
+    /** @return self */
+    public static function fromArray($array)
+    {
+        if ($array instanceof ASTNode
+            && $array->isInstanceOf('Array')
+            && count($array->getChildren()) === 2
+        ) {
+            return new self($array);
+        }
+
+        return new self(null);
+    }
+
+    /** @return self */
+    public static function fromFirstArrayElement($firstArrayElement)
+    {
+        if ($firstArrayElement instanceof ASTNode && $firstArrayElement->isInstanceOf('ArrayElement')) {
+            return self::fromArray($firstArrayElement->getParent());
+        }
+
+        return new self(null);
+    }
+
+    /**
+     * Return represented method name if the given element is a 2-items array
+     * and that the second one is a literal static string.
+     *
+     * @return string|null
+     */
+    public function getMethodNameFromArraySecondElement()
+    {
+        if ($this->array === null) {
+            return null;
+        }
+
+        $secondElement = $this->array->getChild(1)->getChild(0);
+
+        if ($secondElement->isInstanceOf('Literal')) {
+            return substr($secondElement->getImage(), 1, -1);
+        }
+
+        return null;
+    }
+}

src/main/php/PHPMD/Utility/Seeker.php

@@ -29,6 +29,7 @@
  */
 final class Seeker
 {
+    /** @var ASTNode */
     private $node;
 
     private function __construct(ASTNode $node)