anchor.diff:    /// exceeds this constant, then WideConeType approximation is used.
     static const int maxAllocatedTypesInSetSpecializations = 128;
   
  +  final _TFClassImpl? superclass;
     final Set<_TFClassImpl> supertypes; // List of super-types including this.
     final Set<_TFClassImpl> _allocatedSubtypes = new Set<_TFClassImpl>();
  -  final Map<Selector, Member> _dispatchTargets = <Selector, Member>{};
  +  late final Map<Name, Member> _dispatchTargetsSetters =
  +      _initDispatchTargets(true);
  +  late final Map<Name, Member> _dispatchTargetsNonSetters =
  +      _initDispatchTargets(false);
     final _DependencyTracker dependencyTracker = new _DependencyTracker();
   
     /// Flag indicating if this class has a noSuchMethod() method not inherited
  
positive.code:     for (var sup in c.supers) {
        supertypes.addAll(getTFClass(sup.classNode).supertypes);
      }
      return new _TFClassImpl(++_classIdCounter, c, supertypes);
    }
  
    ConcreteType addAllocatedClass(Class cl) {
  
negative.code:     _specializedConeType = null; // Reset cached specialization.
    }
  
    Map<Name, Member> _initDispatchTargets(bool setters) {
      Map<Name, Member> targets;
      final superclass = this.superclass;
      if (superclass != null) {
        targets = Map.from(setters
            ? superclass._dispatchTargetsSetters
            : superclass._dispatchTargetsNonSetters);
      } else {
        targets = {};
      }
      for (Field f in classNode.fields) {
        if (!f.isStatic && !f.isAbstract) {
          if (!setters || f.hasSetter) {
            targets[f.name] = f;
          }
        }
      }
      for (Procedure p in classNode.procedures) {
        if (!p.isStatic && !p.isAbstract) {
          if (p.isSetter == setters) {
            targets[p.name] = p;
          }
        }
      }
      return targets;
    }
  
    Member? getDispatchTarget(Selector selector) {
      return (selector.isSetter
          ? _dispatchTargetsSetters
          : _dispatchTargetsNonSetters)[selector.name];
    }
  
    String dump() => "$this {supers: $supertypes}";
  