return; // give up if someone is calling complete
      }
      Waiter succ;
      while (curr != null) {
        succ = curr.next;
        if (curr.thread != null) { // we aren't unlinking this node, update pred.
          pred = curr;
        } else if (pred != null) { // We are unlinking this node and it has a predecessor.
          pred.next = succ;

    try {
      Maps.uniqueIndex((List<String>) listWithNull, Functions.constant(1));
      fail();
    } catch (NullPointerException expected) {
    }
  }

  /** Null keys aren't allowed either. */
  public void testUniqueIndexNullKey() {
    List<String> oneStringList = Lists.newArrayList("foo");
    try {
      Maps.uniqueIndex(oneStringList, Functions.constant(null));
      fail();

    try {
      Maps.uniqueIndex((List<String>) listWithNull, Functions.constant(1));
      fail();
    } catch (NullPointerException expected) {
    }
  }

  /** Null keys aren't allowed either. */
  public void testUniqueIndexNullKey() {
    List<String> oneStringList = Lists.newArrayList("foo");
    try {
      Maps.uniqueIndex(oneStringList, Functions.constant(null));
      fail();

   * relationship is arbitrary and not guaranteed.
   *
   * <p>If this type is a type variable or wildcard, upper bounds that are themselves type variables
   * aren't included (their super interfaces and superclasses are).
   */
  public final TypeSet getTypes() {
    return new TypeSet();
  }

  /**

   * <p>Failure to follow this advice may result in non-deterministic behavior.
   *
   * <p>Note that the generated multimap's {@link Multimap#removeAll} and {@link
   * Multimap#replaceValues} methods return collections that aren't synchronized.
   *
   * <p>The returned multimap will be serializable if the specified multimap is serializable.
   *
   * @param multimap the multimap to be wrapped in a synchronized view