docs: private String buildMessage(Set<String> unhandled) {
      StringBuilder message =
          new StringBuilder(
              "Non-exhaustive switch; either add a default or handle the remaining cases: ");
      int numberToShow =
          unhandled.size() > MAX_CASES_TO_PRINT
              ? 3 // if there are too many to print, only show three examples.
              : unhandled.size();
      message.append(unhandled.stream().limit(numberToShow).collect(Collectors.joining(", ")));
      if (numberToShow < unhandled.size()) {
        message.append(String.format(", and %d others", unhandled.size() - numberToShow));
      }
      return message.toString();
    }