[ydah]

Returning REMOVE_NODE, an array, or REPLACE_WITH_NULL from enterNode() skips leaveNode() for visitors that already entered the node. This can leave ParentConnectingVisitor's stack unbalanced:

$nodes = $parser->parse('<?php function a() { foo(); } function b() {}');
$traverser = new NodeTraverser(
    new ParentConnectingVisitor(),
    new class extends NodeVisitorAbstract {
        public function enterNode(Node $node) {
            if ($node instanceof Node\Stmt\Expression) {
                return NodeVisitor::REMOVE_NODE;
            }
        }
    }
);
$nodes = $traverser->traverse($nodes);
$nodes[1]->getAttribute('parent'); // Before: function a; after: null.

The same missing callback occurs with each return value:

Return from enterNode()	Example input → result
NodeVisitor::REMOVE_NODE	foo(); → removed
[new Node\Stmt\Nop()]	foo(); → ; ([] removes it)
NodeVisitor::REPLACE_WITH_NULL on Else_	if ($x) {} else {} → if ($x) {}

Call leaveNode() in reverse order for visitors that entered the node, while skipping children and later visitors. Ignore replacement return values during these calls to preserve the removal, while honoring STOP_TRAVERSAL.