anchor.diff:      if (supernode == null) {
         // This should be Object.
         superclasses = new List<Supertype>.filled(0, dummySupertype);
  -      interfaces = new List<Supertype>.filled(0, dummySupertype);
  +      interfacesList = new List<Supertype>.filled(0, dummySupertype);
         maxInheritancePath = 0;
       } else {
         maxInheritancePath = supernode.maxInheritancePath + 1;
  
positive.code:             }
            }
          }
          // ignore: unnecessary_null_comparison
        } else if (superclassInterfaces != null &&
            !classBuilder.library.isNonNullableByDefault &&
            supernode.classBuilder.library.isNonNullableByDefault) {
          interfaces = <Supertype>[];
          for (int i = 0; i < superclassInterfaces.length; i++) {
            addInterface(interfaces, superclasses, superclassInterfaces[i]);
          }
        } else {
          interfaces = superclassInterfaces;
        }
      }
  
  
negative.code:     }
  
      List<Supertype> superclasses;
      List<Supertype> interfacesList;
      int maxInheritancePath;
  
      List<TypeBuilder>? directInterfaceBuilders;
  