* populated.
           */
          return of(requireNonNull(dedupedElements[0]));
        default:
          return new JdkBackedImmutableSet<>(delegate, asImmutableList(dedupedElements, distinct));
      }
    }
  }

  private static int estimatedSizeForUnknownDuplication(int inputElementsIncludingAnyDuplicates) {