} else {
      return ~index;
    }
  }

  @Override
  ImmutableSortedSet<E> subSetImpl(
      E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
    return tailSetImpl(fromElement, fromInclusive).headSetImpl(toElement, toInclusive);
  }

  @Override
  ImmutableSortedSet<E> tailSetImpl(E fromElement, boolean inclusive) {

            ContiguousSet.create(Range.open(0, 4), NOT_EQUAL_TO_INTEGERS),
            ImmutableSortedSet.of(1, 2, 3))
        .addEqualityGroup(
            ContiguousSet.create(Range.closedOpen(1, 1), integers()),
            ContiguousSet.closedOpen(1, 1),
            ContiguousSet.closedOpen(Integer.MIN_VALUE, Integer.MIN_VALUE),
            ImmutableSortedSet.of(),
            ImmutableSet.of())
        .testEquals();

            .build();

    assertThat(RANGE_SET_ONE.difference(RANGE_SET_TWO)).isEqualTo(expected);
  }

  public void testAsSet() {
    ImmutableSortedSet<Integer> expectedSet = ImmutableSortedSet.of(2, 3, 4, 8, 9, 16, 17);
    ImmutableSortedSet<Integer> asSet = RANGE_SET_ONE.asSet(DiscreteDomain.integers());
    assertEquals(expectedSet, asSet);
    assertThat(asSet).containsExactlyElementsIn(expectedSet).inOrder();

            ContiguousSet.create(Range.open(0, 4), NOT_EQUAL_TO_INTEGERS),
            ImmutableSortedSet.of(1, 2, 3))
        .addEqualityGroup(
            ContiguousSet.create(Range.closedOpen(1, 1), integers()),
            ContiguousSet.closedOpen(1, 1),
            ContiguousSet.closedOpen(Integer.MIN_VALUE, Integer.MIN_VALUE),
            ImmutableSortedSet.of(),
            ImmutableSet.of())
        .testEquals();

        }
      };
    }

    ImmutableSortedSet<C> subSet(Range<C> range) {
      return subRangeSet(range).asSet(domain);
    }

    @Override
    ImmutableSortedSet<C> headSetImpl(C toElement, boolean inclusive) {
      return subSet(Range.upTo(toElement, BoundType.forBoolean(inclusive)));
    }

    @Override
    ImmutableSortedSet<C> subSetImpl(

 * Collections#singleton(Object)} and {@link java.util.LinkedHashSet} for empty, singleton and
 * regular sets respectively. For the sorted sets, it's a thin wrapper around {@link
 * java.util.TreeSet}.
 *
 * @see ImmutableSortedSet
 * @author Hayward Chan
 */
@SuppressWarnings("serial") // Serialization only done in GWT.
public abstract class ImmutableSet<E> extends ImmutableCollection<E> implements Set<E> {
  ImmutableSet() {}

        }
      };
    }

    ImmutableSortedSet<C> subSet(Range<C> range) {
      return subRangeSet(range).asSet(domain);
    }

    @Override
    ImmutableSortedSet<C> headSetImpl(C toElement, boolean inclusive) {
      return subSet(Range.upTo(toElement, BoundType.forBoolean(inclusive)));
    }

    @Override
    ImmutableSortedSet<C> subSetImpl(

      return ImmutableSortedSet.copyOf(elements);
    }
  }

  public static class ImmutableSortedSetHeadsetGenerator extends TestStringSortedSetGenerator {
    @Override
    protected SortedSet<String> create(String[] elements) {
      List<String> list = Lists.newArrayList(elements);
      list.add("zzz");
      return ImmutableSortedSet.copyOf(list).headSet("zzy");
    }
  }

    return (valueComparator == null)
        ? ImmutableSet.copyOf(values)
        : ImmutableSortedSet.copyOf(valueComparator, values);
  }

  private static <V> ImmutableSet<V> emptySet(@Nullable Comparator<? super V> valueComparator) {
    return (valueComparator == null)
        ? ImmutableSet.of()
        : ImmutableSortedSet.emptySet(valueComparator);
  }

  private static <V> ImmutableSet.Builder<V> valuesBuilder(

package com.google.common.collect;

import java.util.SortedSet;

/**
 * GWT emulation of {@link RegularImmutableSortedSet}.
 *
 * @author Hayward Chan
 */
final class RegularImmutableSortedSet<E> extends ImmutableSortedSet<E> {
  /** true if this set is a subset of another immutable sorted set. */
  final boolean isSubset;

  RegularImmutableSortedSet(SortedSet<E> delegate, boolean isSubset) {
    super(delegate);