anchor.diff:    VoidType get voidType => VoidTypeImpl.instance;
   
     NullabilitySuffix get _nullabilitySuffix {
  -    if (_isNonNullableByDefault) {
  +    if (isNonNullableByDefault) {
         return NullabilitySuffix.none;
       } else {
         return NullabilitySuffix.star;
  
positive.code:     return _nullElement ??= _getClassElement(_coreLibrary, 'Null');
    }
  
    InterfaceTypeImpl get nullStar {
      return _nullStar ??= nullElement.instantiate(
        typeArguments: const [],
  
negative.code:   }
  
    NullabilitySuffix get _questionOrStarSuffix {
      return isNonNullableByDefault
          ? NullabilitySuffix.question
          : NullabilitySuffix.star;
    }
  