anchor.diff:  
     @override
     EnumSet<MemberUse> constantInit(ConstantValue constant) {
  -    _initialConstants ??= [];
  -    _initialConstants.add(constant);
  +    (_initialConstants ??= []).add(constant);
       return init();
     }
   
  
positive.code: // for details. All rights reserved. Use of this source code is governed by a
  // BSD-style license that can be found in the LICENSE file.
  
  // @dart = 2.10
  
  import 'dart:math' as Math;
  
  import '../common.dart';
  import '../constants/values.dart';
  import '../elements/entities.dart';
  import '../js_model/closure.dart' show JRecordField;
  import '../serialization/serialization_interfaces.dart';
  import '../util/enumset.dart';
  import 'call_structure.dart';
  
negative.code:       return createPotentialAccessSet(potentialAccess?.invokes);
      }
  
      if (member is FieldEntity) {
        if (member.isAssignable) {
          return FieldUsage(member,
              potentialReads: createPotentialReads(),
  