anchor.diff:    });
   
     const Screen.conditional({
  -    @required String id,
  -    String requiresLibrary,
  +    required String id,
  +    String? requiresLibrary,
       bool requiresDartVm = false,
       bool requiresDebugBuild = false,
       bool requiresVmDeveloperMode = false,
       bool worksOffline = false,
  -    bool Function(FlutterVersion currentVersion) shouldShowForFlutterVersion,
  +    bool Function(FlutterVersion? currentVersion)? shouldShowForFlutterVersion,
       bool showFloatingDebuggerControls = true,
  -    String title,
  -    IconData icon,
  -    Key tabKey,
  +    String title = '',
  +    IconData? icon,
  +    Key? tabKey,
     }) : this(
             id,
             requiresLibrary: requiresLibrary,
  
positive.code:   ///
    /// If the screen does not have a custom documentation page, this property
    /// should return `null`.
    String get docPageId => null;
  
    int get badgeCount => 0;
  
  
negative.code: // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  // ignore_for_file: import_of_legacy_library_into_null_safe
  
  import 'dart:async';
  import 'dart:math' as math;
  