anchor.diff:  
     List<List<DartType>> fillTypes2({bool isFfi = false}) {
       List<List<DartType>> list = new List<List<DartType>>();
  -    for (int i = 0, n = 1 + rand.nextInt(4); i < n; i++) {
  +    for (int i = 0, n = 1 + rand.nextInt(8); i < n; i++) {
         list.add(fillTypes1(isFfi: isFfi));
       }
       return list;
  
positive.code:   void emitClasses() {
      assert(classFields.length == classMethods.length);
      for (int i = 0; i < classFields.length; i++) {
        emitLn('class X$i ${i == 0 ? "" : "extends X${i - 1}"} {');
        indent += 2;
        emitVarDecls('$fieldName${i}_', classFields[i]);
        currentClass = i;
  
negative.code:     globalMethods = fillTypes2();
      classFields = fillTypes2();
      classMethods = fillTypes3(classFields.length);
      classParents = new List<int>();
      // Setup optional ffi methods and types.
      List<bool> ffiStatus = new List<bool>();
      for (var m in globalMethods) {
  