anchor.diff:    /// import 'dart:async';
     ///
     /// main() {
  -  ///   runZoned(() {
  +  ///   runZonedGuarded(() {
     ///     // The following asynchronous error is *not* caught by the `catchError`
     ///     // in the nested zone, since errors are not to cross zone boundaries
     ///     // with different error handlers.
     ///     // Instead the error is handled by the current error handler,
     ///     // printing "Caught by outer zone: asynchronous error".
     ///     var future = Future.error("asynchronous error");
  -  ///     runZoned(() {
  +  ///     runZonedGuarded(() {
     ///       future.catchError((e) { throw "is never reached"; });
  -  ///     }, onError: (e) { throw "is never reached"; });
  -  ///   }, onError: (e) { print("Caught by outer zone: $e"); });
  +  ///     }, (error, stack) { throw "is never reached"; });
  +  ///   }, (error, stack) { print("Caught by outer zone: $error"); });
     /// }
     /// ```
     Zone get errorZone;
  
positive.code: /// The function must only access zone-related functionality through
  /// [self], [parent] or [zone].
  /// It should not depend on the current zone ([Zone.current]).
  typedef AsyncError? ErrorCallbackHandler(Zone self, ZoneDelegate parent,
      Zone zone, Object error, StackTrace? stackTrace);
  
  /// The type of a custom [Zone.scheduleMicrotask] implementation function.
  ///
  
negative.code: 
    static ZoneDelegate? _rootDelegate;
  
    ZoneDelegate get _delegate => _rootDelegate ??= _ZoneDelegate(this);
    // It's a lie, but the root zone never uses the parent delegate.
    ZoneDelegate get _parentDelegate => _delegate;
  
  