anchor.diff:    @override
     void registerDynamicUse(DynamicUse dynamicUse) {
       _dynamicUses ??= Setlet.of(worldImpact.dynamicUses);
  -    _dynamicUses.add(dynamicUse);
  +    _dynamicUses!.add(dynamicUse);
     }
   
     @override
     void registerTypeUse(TypeUse typeUse) {
       _typeUses ??= Setlet.of(worldImpact.typeUses);
  -    _typeUses.add(typeUse);
  +    _typeUses!.add(typeUse);
     }
   
     @override
  
positive.code: 
    Iterable<ConstantUse> get constantUses => const [];
  
    void _forEach<U>(Iterable<U> uses, void Function(MemberEntity, U) visitUse) =>
        uses.forEach((use) => visitUse(member, use));
  
    void forEachDynamicUse(void Function(MemberEntity, DynamicUse) visitUse) =>
        _forEach(dynamicUses, visitUse);
    void forEachStaticUse(void Function(MemberEntity, StaticUse) visitUse) =>
        _forEach(staticUses, visitUse);
    void forEachTypeUse(void Function(MemberEntity, TypeUse) visitUse) =>
        _forEach(typeUses, visitUse);
    void forEachConstantUse(void Function(MemberEntity, ConstantUse) visitUse) =>
        _forEach(constantUses, visitUse);
  
    bool get isEmpty => true;
  
negative.code:   @override
    void registerConstantUse(ConstantUse constantUse) {
      _constantUses ??= Setlet.of(worldImpact.constantUses);
      _constantUses!.add(constantUse);
    }
  
    @override
  