anchor.diff:    /// after a delay of 1 second. This can be achieved through [restoreSystemUIOverlays]
     /// or calling this again. Otherwise, the original UI overlay settings will be
     /// automatically restored only when the application loses and regains focus.
  -  static Future<Null> setEnabledSystemUIOverlays(List<SystemUiOverlay> overlays) async {
  +  static Future<void> setEnabledSystemUIOverlays(List<SystemUiOverlay> overlays) async {
       await SystemChannels.platform.invokeMethod(
         'SystemChrome.setEnabledSystemUIOverlays',
         _stringify(overlays),
  
positive.code:   /// The `orientation` argument is a list of [DeviceOrientation] enum values.
    /// The empty list causes the application to defer to the operating system
    /// default.
    static Future<Null> setPreferredOrientations(List<DeviceOrientation> orientations) async {
      await SystemChannels.platform.invokeMethod(
        'SystemChrome.setPreferredOrientations',
        _stringify(orientations),
  
negative.code:   ///
    /// Any part of the description that is unsupported on the current platform
    /// will be ignored.
    static Future<void> setApplicationSwitcherDescription(ApplicationSwitcherDescription description) async {
      await SystemChannels.platform.invokeMethod(
        'SystemChrome.setApplicationSwitcherDescription',
        <String, dynamic>{
  