anchor.diff:    final _Zone zone;
     final T function;
     const _ZoneFunction(this.zone, this.function);
  -}
  -
  -class _RunNullaryZoneFunction {
  -  final _Zone zone;
  -  final RunHandler function;
  -  const _RunNullaryZoneFunction(this.zone, this.function);
  -}
  -
  -class _RunUnaryZoneFunction {
  -  final _Zone zone;
  -  final RunUnaryHandler function;
  -  const _RunUnaryZoneFunction(this.zone, this.function);
  -}
  -
  -class _RunBinaryZoneFunction {
  -  final _Zone zone;
  -  final RunBinaryHandler function;
  -  const _RunBinaryZoneFunction(this.zone, this.function);
  -}
  -
  -class _RegisterNullaryZoneFunction {
  -  final _Zone zone;
  -  final RegisterCallbackHandler function;
  -  const _RegisterNullaryZoneFunction(this.zone, this.function);
  -}
  -
  -class _RegisterUnaryZoneFunction {
  -  final _Zone zone;
  -  final RegisterUnaryCallbackHandler function;
  -  const _RegisterUnaryZoneFunction(this.zone, this.function);
  -}
  -
  -class _RegisterBinaryZoneFunction {
  -  final _Zone zone;
  -  final RegisterBinaryCallbackHandler function;
  -  const _RegisterBinaryZoneFunction(this.zone, this.function);
   }
   
   /// A parameter object with custom zone function handlers for [Zone.fork].
  
positive.code: class _RootZone extends _Zone {
    const _RootZone();
  
    _RunNullaryZoneFunction get _run =>
        const _RunNullaryZoneFunction(_rootZone, _rootRun);
    _RunUnaryZoneFunction get _runUnary =>
        const _RunUnaryZoneFunction(_rootZone, _rootRunUnary);
    _RunBinaryZoneFunction get _runBinary =>
        const _RunBinaryZoneFunction(_rootZone, _rootRunBinary);
    _RegisterNullaryZoneFunction get _registerCallback =>
        const _RegisterNullaryZoneFunction(_rootZone, _rootRegisterCallback);
    _RegisterUnaryZoneFunction get _registerUnaryCallback =>
        const _RegisterUnaryZoneFunction(_rootZone, _rootRegisterUnaryCallback);
    _RegisterBinaryZoneFunction get _registerBinaryCallback =>
        const _RegisterBinaryZoneFunction(_rootZone, _rootRegisterBinaryCallback);
    _ZoneFunction<ErrorCallbackHandler> get _errorCallback =>
        const _ZoneFunction<ErrorCallbackHandler>(_rootZone, _rootErrorCallback);
    _ZoneFunction<ScheduleMicrotaskHandler> get _scheduleMicrotask =>
  
negative.code: 
    // TODO(floitsch): the types of the `_ZoneFunction`s should have a type for
    // all fields.
    _ZoneFunction<RunHandler> get _run;
    _ZoneFunction<RunUnaryHandler> get _runUnary;
    _ZoneFunction<RunBinaryHandler> get _runBinary;
    _ZoneFunction<RegisterCallbackHandler> get _registerCallback;
    _ZoneFunction<RegisterUnaryCallbackHandler> get _registerUnaryCallback;
    _ZoneFunction<RegisterBinaryCallbackHandler> get _registerBinaryCallback;
    _ZoneFunction<ErrorCallbackHandler> get _errorCallback;
    _ZoneFunction<ScheduleMicrotaskHandler> get _scheduleMicrotask;
    _ZoneFunction<CreateTimerHandler> get _createTimer;
  