code: @GwtIncompatible // SmallCharMatcher
    private static CharMatcher precomputedPositive(
        int totalCharacters, BitSet table, String description) {
      switch (totalCharacters) {
        case 0:
          return none();
        case 1:
          return is((char) table.nextSetBit(0));
        case 2:
          char c1 = (char) table.nextSetBit(0);
          char c2 = (char) table.nextSetBit(c1 + 1);
          return isEither(c1, c2);
        default:
          return isSmall(totalCharacters, table.length())
              ? SmallCharMatcher.from(table, description)
              : new BitSetMatcher(table, description);
      }
    }
docs: Helper method for {@link #precomputedInternal} that doesn't test if the negation is cheaper.