abstract class TypeVisitor {

  private final Set<Type> visited = Sets.newHashSet();

  /**
   * Visits the given types. Null types are ignored. This allows subclasses to call {@code
   * visit(parameterizedType.getOwnerType())} safely without having to check nulls.
   */
  public final void visit(@Nullable Type... types) {
    for (Type type : types) {
      if (type == null || !visited.add(type)) {
        // null owner type, or already visited;

            return ancestorStack.pop();
          }
          return endOfData();
        }
      };
    }

    /**
     * Visits the next node from the top iterator of {@code horizon} and returns the visited node.
     * Null is returned to indicate reaching the end of the top iterator.
     *
     * <p>For example, if horizon is {@code [[a, b], [c, d], [e]]}, {@code visitNext()} will return

        map(new TypeVariableKey(vars[i]), typeArgs[i]);
      }
      visit(rawClass);
      visit(parameterizedType.getOwnerType());
    }

    @Override
    void visitTypeVariable(TypeVariable<?> t) {
      visit(t.getBounds());
    }

    @Override
    void visitWildcardType(WildcardType t) {
      visit(t.getUpperBounds());
    }

    private void map(TypeVariableKey var, Type arg) {

    try {
      multimap().putAll(k3(), Lists.newArrayList(v3(), null));
      fail();
    } catch (NullPointerException expected) {
    }

    Collection<V> values = multimap().get(k3());
    if (values.size() == 0) {
      expectUnchanged();
      // Be extra thorough in case internal state was corrupted by the expected null.
      assertEquals(Lists.newArrayList(), Lists.newArrayList(values));

    final List<Object> annotatedIn1Events = Lists.newArrayList();
    final List<Object> annotatedIn1And2Events = Lists.newArrayList();
    final List<Object> annotatedIn1And2AndClassEvents = Lists.newArrayList();
    final List<Object> declaredIn1AnnotatedIn2Events = Lists.newArrayList();
    final List<Object> declaredIn1AnnotatedInClassEvents = Lists.newArrayList();

    assertThat(Lists.hashCodeImpl(base)).isEqualTo(Lists.hashCodeImpl(copy));

    assertThat(Lists.hashCodeImpl(base)).isNotEqualTo(Lists.hashCodeImpl(outOfOrder));
    assertThat(Lists.hashCodeImpl(base)).isNotEqualTo(Lists.hashCodeImpl(diffValue));
    assertThat(Lists.hashCodeImpl(base)).isNotEqualTo(Lists.hashCodeImpl(diffLength));
    assertThat(Lists.hashCodeImpl(base)).isNotEqualTo(Lists.hashCodeImpl(empty));

    Iterator<String> filtered = Iterators.filter(unfiltered, Predicates.alwaysFalse());
    List<String> expected = Collections.emptyList();
    List<String> actual = Lists.newArrayList(filtered);
    assertEquals(expected, actual);
  }

  public void testFilterMatchAll() {
    Iterator<String> unfiltered = Lists.newArrayList("foo", "bar").iterator();

    bus.register(hater);

    bus.post(FIRST);

    assertEquals(
        "ReentrantEventHater expected 2 events",
        Lists.<Object>newArrayList(FIRST, SECOND),
        hater.eventsReceived);
  }

  public class ReentrantEventsHater {
    boolean ready = true;
    List<Object> eventsReceived = Lists.newArrayList();

    @Subscribe
    public void listenForStrings(String event) {
      eventsReceived.add(event);

    SerializableTester.reserializeAndAssert(map.entrySet());
    SerializableTester.reserializeAndAssert(map.keySet());
    assertEquals(
        Lists.newArrayList(map.values()),
        Lists.newArrayList(SerializableTester.reserialize(map.values())));
  }

  @GwtIncompatible // SerializableTester
  public void testEmpty_serialization() {
    SortedSet<String> set = new SafeTreeSet<>();

    SerializableTester.reserializeAndAssert(map.entrySet());
    SerializableTester.reserializeAndAssert(map.keySet());
    assertEquals(
        Lists.newArrayList(map.values()),
        Lists.newArrayList(SerializableTester.reserialize(map.values())));
  }

  @GwtIncompatible // SerializableTester
  public void testEmpty_serialization() {
    SortedSet<String> set = new SafeTreeSet<>();