anchor.diff:  }
   
   class FunctionTypeInformation extends TypeInformation {
  -  Set<Element> callers = new Set<Element>();
  +  Map<Element, int> callers = new Map<Element, int>();
     TypeMask returnType;
     int analyzeCount = 0;
     bool canBeClosurized = false;
  
positive.code:     assert(caller.isImplementation);
      assert(callee.isImplementation);
      assert(isNotClosure(caller));
      Set<Element> callers = typeInformationOf(callee).callers;
      callers.add(caller);
    }
  
    bool addArguments(Node node,
  
negative.code:                                Selector selector,
                                 Element caller,
                                 Element callee) {
      typeInformationOf(callee).removeCall(caller);
      if (callee.isField()) {
        if (selector.isSetter()) {
          Map<Node, TypeMask> assignments = typeInformationOf(callee).assignments;
  