return ImmutableSet.of();
      } else {
        return ImmutableEnumSet.asImmutable(EnumSet.copyOf(collection));
      }
    } else {
      Iterator<E> itr = elements.iterator();
      if (itr.hasNext()) {
        EnumSet<E> enumSet = EnumSet.of(itr.next());
        Iterators.addAll(enumSet, itr);
        return ImmutableEnumSet.asImmutable(enumSet);
      } else {
        return ImmutableSet.of();
      }
    }

        return set;
      }
    } else if (elements instanceof EnumSet) {
      EnumSet<?> clone = ((EnumSet<?>) elements).clone();
      ImmutableSet<?> untypedResult = ImmutableEnumSet.asImmutable(clone);
      /*
       * The result has the same type argument we started with. We just couldn't express EnumSet<E>
       * or ImmutableEnumSet<E> along the way because our own <E> isn't <E extends Enum<E>>.
       *

      for (Entry<?, ?> entry : clone.entrySet()) {
        checkEntryNotNull(entry.getKey(), entry.getValue());
      }
      ImmutableMap<?, ? extends V> untypedResult = ImmutableEnumMap.asImmutable(clone);
      /*
       * The result has the same type argument we started with. We just couldn't express EnumMap<K,
       * ...> or ImmutableEnumMap<K, ...> along the way because our own <K> isn't <K extends

      K key = entry.getKey();
      V value = entry.getValue();
      checkEntryNotNull(key, value);
      enumMap.put(key, value);
    }
    return ImmutableEnumMap.asImmutable(enumMap);
  }

  /**
   * Returns a {@link Collector} that accumulates elements into an {@code ImmutableMap} whose keys

      K key = entry.getKey();
      V value = entry.getValue();
      checkEntryNotNull(key, value);
      enumMap.put(key, value);
    }
    return ImmutableEnumMap.asImmutable(enumMap);
  }

  /**
   * Returns a {@link Collector} that accumulates elements into an {@code ImmutableMap} whose keys