*     is not precisely representable as a {@code double}
   * @since 30.0
   */
  public static double roundToDouble(BigDecimal x, RoundingMode mode) {
    return BigDecimalToDoubleRounder.INSTANCE.roundToDouble(x, mode);
  }

  private static final class BigDecimalToDoubleRounder extends ToDoubleRounder<BigDecimal> {

   *     is not precisely representable as a {@code double}
   * @since 30.0
   */
  public static double roundToDouble(BigDecimal x, RoundingMode mode) {
    return BigDecimalToDoubleRounder.INSTANCE.roundToDouble(x, mode);
  }

  private static final class BigDecimalToDoubleRounder extends ToDoubleRounder<BigDecimal> {

        RoundingMode mode = entry.getKey();
        Double expectation = entry.getValue();
        assertWithMessage("roundToDouble(%s, %s)", input, mode)
            .that(BigDecimalMath.roundToDouble(input, mode))
            .isEqualTo(expectation);
      }

      if (!expectedValues.containsKey(UNNECESSARY)) {
        assertWithMessage("Expected roundUnnecessaryShouldThrow call")

        RoundingMode mode = entry.getKey();
        Double expectation = entry.getValue();
        assertWithMessage("roundToDouble(%s, %s)", input, mode)
            .that(BigIntegerMath.roundToDouble(input, mode))
            .isEqualTo(expectation);
      }

      if (!expectedValues.containsKey(UNNECESSARY)) {

   *     is not precisely representable as a {@code double}
   * @since 30.0
   */
  @GwtIncompatible
  public static double roundToDouble(BigInteger x, RoundingMode mode) {
    return BigIntegerToDoubleRounder.INSTANCE.roundToDouble(x, mode);
  }

  @GwtIncompatible
  private static final class BigIntegerToDoubleRounder extends ToDoubleRounder<BigInteger> {

   *     is not precisely representable as a {@code double}
   * @since 30.0
   */
  @GwtIncompatible
  public static double roundToDouble(long x, RoundingMode mode) {
    // Logic adapted from ToDoubleRounder.
    double roundArbitrarily = (double) x;
    long roundArbitrarilyAsLong = (long) roundArbitrarily;
    int cmpXToRoundArbitrarily;