ContractReturnValue toReturnValue() {
    return switch (this) {
      case False -> ContractReturnValue.returnFalse();
      case True -> ContractReturnValue.returnTrue();
      case NotNull -> ContractReturnValue.returnNotNull();
      case Null -> ContractReturnValue.returnNull();
      case Fail -> ContractReturnValue.fail();
      default -> ContractReturnValue.returnAny();
    };
  }
ContractReturnValue toReturnValue()