assertTrue(copy instanceof ImmutableEnumSet);
  }

  public void testImmutableEnumSet_fromIterable() {
    ImmutableSet<SomeEnum> none = Sets.immutableEnumSet(MinimalIterable.<SomeEnum>of());
    assertThat(none).isEmpty();

    ImmutableSet<SomeEnum> one = Sets.immutableEnumSet(MinimalIterable.of(SomeEnum.B));
    assertThat(one).contains(SomeEnum.B);

    }

    @Override
    public CharMatcher negate() {
      return none();
    }
  }

  /** Implementation of {@link #none()}. */
  private static final class None extends NamedFastMatcher {

    static final CharMatcher INSTANCE = new None();

    private None() {
      super("CharMatcher.none()");
    }

    @Override
    public boolean matches(char c) {

    }

    @Override
    public Object getValue() {
      throw new AssertionError();
    }
  }

  /**
   * A singleton {@link WeakValueReference} used to denote an unset value in an entry with weak
   * values.
   */
  static final WeakValueReference<Object, Object, DummyInternalEntry> UNSET_WEAK_VALUE_REFERENCE =

    }

    @Override
    public CharMatcher negate() {
      return none();
    }
  }

  /** Implementation of {@link #none()}. */
  private static final class None extends NamedFastMatcher {

    static final CharMatcher INSTANCE = new None();

    private None() {
      super("CharMatcher.none()");
    }

    @Override
    public boolean matches(char c) {

 *   <li>notification of evicted (or otherwise removed) entries
 *   <li>accumulation of cache access statistics
 * </ul>
 *
 * <p>These features are all optional; caches can be created using all or none of them. By default,
 * cache instances created by {@code CacheBuilder} will not perform any type of eviction.
 *
 * <p>Usage example:
 *
 * <pre>{@code
 * LoadingCache<Key, Graph> graphs = CacheBuilder.newBuilder()