Create Seeker utility to delegate AST finding

src/main/php/PHPMD/AbstractNode.php

@@ -76,11 +76,12 @@ public function __call($name, array $args)
      * Returns the parent of this node or <b>null</b> when no parent node
      * exists.
      *
-     * @return ASTNode
+     * @return ASTNode|null
      */
     public function getParent()
     {
         $node = $this->node->getParent();
+
         if ($node === null) {
             return null;
         }

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

@@ -17,7 +17,6 @@
 
 namespace PHPMD\Rule;
 
-use OutOfBoundsException;
 use PDepend\Source\AST\AbstractASTCombinationType;
 use PDepend\Source\AST\ASTClassOrInterfaceReference;
 use PDepend\Source\AST\ASTType;
@@ -27,6 +26,7 @@
 use PHPMD\Node\ClassNode;
 use PHPMD\Node\MethodNode;
 use PHPMD\Utility\LastVariableWriting;
+use PHPMD\Utility\Seeker;
 use SplObjectStorage;
 
 /**
@@ -244,11 +244,7 @@ protected function calculateInstanceOfTheCurrentClass(ClassNode $class, ASTNode
             return true;
         }
 
-        $scope = $variable->getParent();
-
-        while ($scope && !$scope->isInstanceOf('Scope')) {
-            $scope = $scope->getParent();
-        }
+        $scope = Seeker::fromNode($variable)->getParentOfType('Scope');
 
         if (!$scope) {
             return false;
@@ -269,30 +265,27 @@ protected function calculateInstanceOfTheCurrentClass(ClassNode $class, ASTNode
             return $this->canBeCurrentClassInstance($class, $lastWriting);
         }
 
-        return $this->isWritingOfSelfType($class, $name, $lastWriting);
+        return ($lastWriting instanceof ASTNode)
+            && $this->isWritingOfSelfType($class, $name, $lastWriting);
     }
 
     /**
      * @param string $name
      *
      * @return bool
      */
-    protected function isWritingOfSelfType(ClassNode $class, $name, $lastWriting)
+    protected function isWritingOfSelfType(ClassNode $class, $name, ASTNode $lastWriting)
     {
-        if (!($lastWriting instanceof ASTNode)) {
-            return false;
-        }
-
         if ($lastWriting->isInstanceOf('CloneExpression')) {
-            $cloned = $this->getChildIfExist($lastWriting, 0);
+            $cloned = Seeker::fromNode($lastWriting)->getChildIfExist(0);
 
             return $cloned
                 && $cloned->isInstanceOf('Variable')
                 && $this->isInstanceOfTheCurrentClass($class, $cloned);
         }
 
         if ($lastWriting->isInstanceOf('AllocationExpression')) {
-            $value = $this->getChildIfExist($lastWriting, 0);
+            $value = Seeker::fromNode($lastWriting)->getChildIfExist(0);
 
             return $value
                 && ($value->isInstanceOf('SelfReference') || $value->isInstanceOf('StaticReference'));
@@ -333,17 +326,4 @@ protected function representCurrentClassName(ClassNode $class, $name)
             $class->getFullQualifiedName(),
         ), true);
     }
-
-    private function getChildIfExist($parent, $index)
-    {
-        try {
-            if ($parent instanceof ASTNode) {
-                return $parent->getChild($index);
-            }
-        } catch (OutOfBoundsException $e) {
-            // fallback to null
-        }
-
-        return null;
-    }
 }

src/main/php/PHPMD/Utility/LastVariableWriting.php

@@ -17,15 +17,13 @@
 
 namespace PHPMD\Utility;
 
-use InvalidArgumentException;
-use OutOfBoundsException;
 use PDepend\Source\AST\ASTFormalParameter;
 use PDepend\Source\AST\ASTFormalParameters;
 use PDepend\Source\AST\ASTType;
 use PHPMD\Node\ASTNode;
 
 /**
- * Utility class to provide string checks and manipulations
+ * Utility class to find the last time a variable was written before an occurrence of it.
  */
 final class LastVariableWriting
 {
@@ -56,10 +54,10 @@ public function findInScope(ASTNode $scope)
             $parent = $occurrence->getParent();
 
             if ($parent->isInstanceOf('AssignmentExpression')) {
-                $assigned = $this->getChildIfExist($parent, 0);
+                $assigned = Seeker::fromNode($parent)->getChildIfExist(0);
 
                 if ($assigned && $assigned->getImage() === $name) {
-                    $lastWriting = $this->getChildIfExist($parent, 1);
+                    $lastWriting = Seeker::fromNode($parent)->getChildIfExist(1);
                 }
             }
         }
@@ -81,18 +79,4 @@ public function findInParameters(ASTFormalParameters $parameters)
 
         return null;
     }
-
-    /** @return ASTNode|null */
-    private function getChildIfExist($parent, $index)
-    {
-        try {
-            if ($parent instanceof ASTNode) {
-                return $parent->getChild($index);
-            }
-        } catch (OutOfBoundsException $e) {
-            // fallback to null
-        }
-
-        return null;
-    }
 }

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

@@ -0,0 +1,68 @@
+<?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 InvalidArgumentException;
+use OutOfBoundsException;
+use PDepend\Source\AST\ASTFormalParameter;
+use PDepend\Source\AST\ASTFormalParameters;
+use PDepend\Source\AST\ASTType;
+use PHPMD\Node\ASTNode;
+
+/**
+ * Utility class to do some more advanced searches from an ASTNode.
+ */
+final class Seeker
+{
+    private $node;
+
+    private function __construct(ASTNode $node)
+    {
+        $this->node = $node;
+    }
+
+    /** @return self */
+    public static function fromNode(ASTNode $node)
+    {
+        return new self($node);
+    }
+
+    /** @return ASTNode|null */
+    public function getParentOfType($type)
+    {
+        $scope = $this->node->getParent();
+
+        while ($scope && !$scope->isInstanceOf($type)) {
+            $scope = $scope->getParent();
+        }
+
+        return $scope;
+    }
+
+    /** @return ASTNode|null */
+    public function getChildIfExist($index)
+    {
+        try {
+            return $this->node->getChild($index);
+        } catch (OutOfBoundsException $e) {
+            // fallback to null
+        }
+
+        return null;
+    }
+}