anchor.diff:        unresolvedNodes = new Set<Identifier>(),
         elementNodes = new Map<Element, Set<Node>>(),
         localPlaceholders = new Map<FunctionElement, Set<LocalPlaceholder>>(),
  -      privateNodes = new Map<LibraryElement, Set<Node>>();
  +      privateNodes = new Map<LibraryElement, Set<Identifier>>();
   
     void collectFunctionDeclarationPlaceholders(
         FunctionElement element, FunctionExpression node) {
  
positive.code:   void makePrivateIdentifier(Identifier node) {
      assert(node !== null);
      privateNodes.putIfAbsent(
          currentElement.getLibrary(), () => new Set<Node>()).add(node);
    }
  
    void makeUnresolvedPlaceholder(Node node) {
  
negative.code:   final Set<Identifier> unresolvedNodes;
    final Map<Element, Set<Node>> elementNodes;
    final Map<FunctionElement, Set<LocalPlaceholder>> localPlaceholders;
    final Map<LibraryElement, Set<Identifier>> privateNodes;
    Map<String, LocalPlaceholder> currentLocalPlaceholders;
    Element currentElement;
    TreeElements treeElements;
  