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    <h3>Editing: NodeTraverser.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php declare(strict_types=1);

namespace PhpParser;

class NodeTraverser implements NodeTraverserInterface {
    /**
     * @deprecated Use NodeVisitor::DONT_TRAVERSE_CHILDREN instead.
     */
    public const DONT_TRAVERSE_CHILDREN = NodeVisitor::DONT_TRAVERSE_CHILDREN;

    /**
     * @deprecated Use NodeVisitor::STOP_TRAVERSAL instead.
     */
    public const STOP_TRAVERSAL = NodeVisitor::STOP_TRAVERSAL;

    /**
     * @deprecated Use NodeVisitor::REMOVE_NODE instead.
     */
    public const REMOVE_NODE = NodeVisitor::REMOVE_NODE;

    /**
     * @deprecated Use NodeVisitor::DONT_TRAVERSE_CURRENT_AND_CHILDREN instead.
     */
    public const DONT_TRAVERSE_CURRENT_AND_CHILDREN = NodeVisitor::DONT_TRAVERSE_CURRENT_AND_CHILDREN;

    /** @var list&lt;NodeVisitor&gt; Visitors */
    protected array $visitors = [];

    /** @var bool Whether traversal should be stopped */
    protected bool $stopTraversal;

    /**
     * Create a traverser with the given visitors.
     *
     * @param NodeVisitor ...$visitors Node visitors
     */
    public function __construct(NodeVisitor ...$visitors) {
        $this-&gt;visitors = $visitors;
    }

    /**
     * Adds a visitor.
     *
     * @param NodeVisitor $visitor Visitor to add
     */
    public function addVisitor(NodeVisitor $visitor): void {
        $this-&gt;visitors[] = $visitor;
    }

    /**
     * Removes an added visitor.
     */
    public function removeVisitor(NodeVisitor $visitor): void {
        $index = array_search($visitor, $this-&gt;visitors);
        if ($index !== false) {
            array_splice($this-&gt;visitors, $index, 1, []);
        }
    }

    /**
     * Traverses an array of nodes using the registered visitors.
     *
     * @param Node[] $nodes Array of nodes
     *
     * @return Node[] Traversed array of nodes
     */
    public function traverse(array $nodes): array {
        $this-&gt;stopTraversal = false;

        foreach ($this-&gt;visitors as $visitor) {
            if (null !== $return = $visitor-&gt;beforeTraverse($nodes)) {
                $nodes = $return;
            }
        }

        $nodes = $this-&gt;traverseArray($nodes);

        for ($i = \count($this-&gt;visitors) - 1; $i &gt;= 0; --$i) {
            $visitor = $this-&gt;visitors[$i];
            if (null !== $return = $visitor-&gt;afterTraverse($nodes)) {
                $nodes = $return;
            }
        }

        return $nodes;
    }

    /**
     * Recursively traverse a node.
     *
     * @param Node $node Node to traverse.
     */
    protected function traverseNode(Node $node): void {
        foreach ($node-&gt;getSubNodeNames() as $name) {
            $subNode = $node-&gt;$name;

            if (\is_array($subNode)) {
                $node-&gt;$name = $this-&gt;traverseArray($subNode);
                if ($this-&gt;stopTraversal) {
                    break;
                }
            } elseif ($subNode instanceof Node) {
                $traverseChildren = true;
                $visitorIndex = -1;

                foreach ($this-&gt;visitors as $visitorIndex =&gt; $visitor) {
                    $return = $visitor-&gt;enterNode($subNode);
                    if (null !== $return) {
                        if ($return instanceof Node) {
                            $this-&gt;ensureReplacementReasonable($subNode, $return);
                            $subNode = $node-&gt;$name = $return;
                        } elseif (NodeVisitor::DONT_TRAVERSE_CHILDREN === $return) {
                            $traverseChildren = false;
                        } elseif (NodeVisitor::DONT_TRAVERSE_CURRENT_AND_CHILDREN === $return) {
                            $traverseChildren = false;
                            break;
                        } elseif (NodeVisitor::STOP_TRAVERSAL === $return) {
                            $this-&gt;stopTraversal = true;
                            break 2;
                        } elseif (NodeVisitor::REPLACE_WITH_NULL === $return) {
                            $node-&gt;$name = null;
                            continue 2;
                        } else {
                            throw new \LogicException(
                                'enterNode() returned invalid value of type ' . gettype($return)
                            );
                        }
                    }
                }

                if ($traverseChildren) {
                    $this-&gt;traverseNode($subNode);
                    if ($this-&gt;stopTraversal) {
                        break;
                    }
                }

                for (; $visitorIndex &gt;= 0; --$visitorIndex) {
                    $visitor = $this-&gt;visitors[$visitorIndex];
                    $return = $visitor-&gt;leaveNode($subNode);

                    if (null !== $return) {
                        if ($return instanceof Node) {
                            $this-&gt;ensureReplacementReasonable($subNode, $return);
                            $subNode = $node-&gt;$name = $return;
                        } elseif (NodeVisitor::STOP_TRAVERSAL === $return) {
                            $this-&gt;stopTraversal = true;
                            break 2;
                        } elseif (NodeVisitor::REPLACE_WITH_NULL === $return) {
                            $node-&gt;$name = null;
                            break;
                        } elseif (\is_array($return)) {
                            throw new \LogicException(
                                'leaveNode() may only return an array ' .
                                'if the parent structure is an array'
                            );
                        } else {
                            throw new \LogicException(
                                'leaveNode() returned invalid value of type ' . gettype($return)
                            );
                        }
                    }
                }
            }
        }
    }

    /**
     * Recursively traverse array (usually of nodes).
     *
     * @param array $nodes Array to traverse
     *
     * @return array Result of traversal (may be original array or changed one)
     */
    protected function traverseArray(array $nodes): array {
        $doNodes = [];

        foreach ($nodes as $i =&gt; $node) {
            if ($node instanceof Node) {
                $traverseChildren = true;
                $visitorIndex = -1;

                foreach ($this-&gt;visitors as $visitorIndex =&gt; $visitor) {
                    $return = $visitor-&gt;enterNode($node);
                    if (null !== $return) {
                        if ($return instanceof Node) {
                            $this-&gt;ensureReplacementReasonable($node, $return);
                            $nodes[$i] = $node = $return;
                        } elseif (\is_array($return)) {
                            $doNodes[] = [$i, $return];
                            continue 2;
                        } elseif (NodeVisitor::REMOVE_NODE === $return) {
                            $doNodes[] = [$i, []];
                            continue 2;
                        } elseif (NodeVisitor::DONT_TRAVERSE_CHILDREN === $return) {
                            $traverseChildren = false;
                        } elseif (NodeVisitor::DONT_TRAVERSE_CURRENT_AND_CHILDREN === $return) {
                            $traverseChildren = false;
                            break;
                        } elseif (NodeVisitor::STOP_TRAVERSAL === $return) {
                            $this-&gt;stopTraversal = true;
                            break 2;
                        } elseif (NodeVisitor::REPLACE_WITH_NULL === $return) {
                            throw new \LogicException(
                                'REPLACE_WITH_NULL can not be used if the parent structure is an array');
                        } else {
                            throw new \LogicException(
                                'enterNode() returned invalid value of type ' . gettype($return)
                            );
                        }
                    }
                }

                if ($traverseChildren) {
                    $this-&gt;traverseNode($node);
                    if ($this-&gt;stopTraversal) {
                        break;
                    }
                }

                for (; $visitorIndex &gt;= 0; --$visitorIndex) {
                    $visitor = $this-&gt;visitors[$visitorIndex];
                    $return = $visitor-&gt;leaveNode($node);

                    if (null !== $return) {
                        if ($return instanceof Node) {
                            $this-&gt;ensureReplacementReasonable($node, $return);
                            $nodes[$i] = $node = $return;
                        } elseif (\is_array($return)) {
                            $doNodes[] = [$i, $return];
                            break;
                        } elseif (NodeVisitor::REMOVE_NODE === $return) {
                            $doNodes[] = [$i, []];
                            break;
                        } elseif (NodeVisitor::STOP_TRAVERSAL === $return) {
                            $this-&gt;stopTraversal = true;
                            break 2;
                        } elseif (NodeVisitor::REPLACE_WITH_NULL === $return) {
                            throw new \LogicException(
                                'REPLACE_WITH_NULL can not be used if the parent structure is an array');
                        } else {
                            throw new \LogicException(
                                'leaveNode() returned invalid value of type ' . gettype($return)
                            );
                        }
                    }
                }
            } elseif (\is_array($node)) {
                throw new \LogicException('Invalid node structure: Contains nested arrays');
            }
        }

        if (!empty($doNodes)) {
            while (list($i, $replace) = array_pop($doNodes)) {
                array_splice($nodes, $i, 1, $replace);
            }
        }

        return $nodes;
    }

    private function ensureReplacementReasonable(Node $old, Node $new): void {
        if ($old instanceof Node\Stmt &amp;&amp; $new instanceof Node\Expr) {
            throw new \LogicException(
                &quot;Trying to replace statement ({$old-&gt;getType()}) &quot; .
                &quot;with expression ({$new-&gt;getType()}). Are you missing a &quot; .
                &quot;Stmt_Expression wrapper?&quot;
            );
        }

        if ($old instanceof Node\Expr &amp;&amp; $new instanceof Node\Stmt) {
            throw new \LogicException(
                &quot;Trying to replace expression ({$old-&gt;getType()}) &quot; .
                &quot;with statement ({$new-&gt;getType()})&quot;
            );
        }
    }
}
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