PreviousConnectingVisitor: Utilize WeakReference (#730)

Author: staabm

src/Ast/ExpressionFinder.php

@@ -134,6 +134,10 @@ private function findFirstPreviousOfNode(Node $node, callable $filter): ?Node
  // move to previous expression
  $previousStatement = $node->getAttribute(PreviousConnectingVisitor::ATTRIBUTE_PREVIOUS);
  if (null !== $previousStatement) {
+ if ($previousStatement instanceof \WeakReference) {
+ $previousStatement = $previousStatement->get();
+ }
+
  if (! $previousStatement instanceof Node) {
  throw new ShouldNotHappenException();
  }

src/Ast/PreviousConnectingVisitor.php

@@ -39,7 +39,7 @@ public function enterNode(Node $node)
  && ! $this->previous instanceof Node\Stmt\ClassLike
  && ! $this->previous instanceof VirtualNode
  ) {
- $node->setAttribute(self::ATTRIBUTE_PREVIOUS, $this->previous);
+ $node->setAttribute(self::ATTRIBUTE_PREVIOUS, \WeakReference::create($this->previous));
  }
 
  return null;