}
      T result = result(entryIndex);
      toRemove = entryIndex;
      entryIndex = backingMap.nextIndex(entryIndex);
      return result;
    }

    @Override
    public void remove() {
      checkForConcurrentModification();
      CollectPreconditions.checkRemove(toRemove != -1);
      size -= backingMap.removeEntry(toRemove);
      entryIndex = backingMap.nextIndexAfterRemove(entryIndex, toRemove);

      } catch (UnsupportedOperationException e) {
        Set<K> toRemove = new HashSet<>();
        for (Entry<K, V> entry : map().entrySet()) {
          if (c.contains(entry.getValue())) {
            toRemove.add(entry.getKey());
          }
        }
        return map().keySet().removeAll(toRemove);
      }
    }

    @Override
    public boolean retainAll(Collection<?> c) {