assertEquals("b", consumingIterator.next());
    assertThat(list).isEmpty();

    assertFalse(consumingIterator.hasNext());
  }

  @GwtIncompatible // ?
  // TODO: Figure out why this is failing in GWT.
  public void testConsumingIterator_duelingIterators() {
    // Test data
    List<String> list = Lists.newArrayList("a", "b");

    // Test & Verify

    assertEquals("b", consumingIterator.next());
    assertThat(list).isEmpty();

    assertFalse(consumingIterator.hasNext());
  }

  @GwtIncompatible // ?
  // TODO: Figure out why this is failing in GWT.
  public void testConsumingIterator_duelingIterators() {
    // Test data
    List<String> list = Lists.newArrayList("a", "b");

    // Test & Verify

 * environment if possible) before spending a lot of effort on tweaking a particular element.
 *
 * <h3>Other types of preconditions</h3>
 *
 * <p>Not every type of precondition failure is supported by these methods. Continue to throw
 * standard JDK exceptions such as {@link java.util.NoSuchElementException} or {@link
 * UnsupportedOperationException} in the situations they are intended for.
 *

      Type subtypeParam = getCovariantTypeResolver().resolveType(typeVars[i]);
      // If 'supertype' is "List<? extends CharSequence>"
      // and 'this' is StringArrayList,
      // First step is to figure out StringArrayList "is-a" List<E> where <E> = String.
      // String is then matched against <? extends CharSequence>, the supertypeArgs[0].
      if (!of(subtypeParam).is(supertypeArgs[i], typeVars[i])) {
        return false;

                  ImmutableList.<K>asImmutableList(sortedKeys), comparator),
              ImmutableList.<V>asImmutableList(sortedValues));
      }
    }

    /**
     * Throws UnsupportedOperationException. A future version may support this operation. Then the
     * value for any given key will be the one that was last supplied in a {@code put} operation for
     * that key.
     *
     * @throws UnsupportedOperationException always

  }

  public void testReloadAfterFailure() throws ExecutionException {
    final AtomicInteger count = new AtomicInteger();
    final Exception e = new IllegalStateException("exception to trigger failure on first load()");
    CacheLoader<Integer, String> failOnceFunction =
        new CacheLoader<Integer, String>() {

          @Override
          public String load(Integer key) throws Exception {

          // misconfigured mock. Try to switch to Failure.
          Failure failure;
          try {
            failure = new Failure(t);
          } catch (Exception | Error oomMostLikely) { // sneaky checked exception
            failure = Failure.FALLBACK_INSTANCE;
          }

    return (UnmodifiableListIterator<T>) ArrayItr.EMPTY;
  }

  /**
   * This is an enum singleton rather than an anonymous class so ProGuard can figure out it's only
   * referenced by emptyModifiableIterator().
   */
  private enum EmptyModifiableIterator implements Iterator<Object> {
    INSTANCE;

    @Override
    public boolean hasNext() {

 * Kotlin code. In this class, nothing is publicly visible (nor exposed indirectly through a
 * publicly visible subclass), and I doubt any of our current or future Kotlin extensions for the
 * package will refer to the class. Plus, @ParametricNullness is only a temporary workaround,
 * anyway, so we just need to get by without the annotations here until Kotlin better understands

        default:
          return fromEntries(comparator, false, entries, size);
      }
    }

    /**
     * Throws UnsupportedOperationException. A future version may support this operation. Then the
     * value for any given key will be the one that was last supplied in a {@code put} operation for
     * that key.
     *
     * @throws UnsupportedOperationException always