} else {
        other.map.forEach(this::put);
        return this;
      }
    }

    ImmutableMap<K, V> toImmutableMap() {
      return (map == null) ? ImmutableMap.<K, V>of() : ImmutableEnumMap.asImmutable(map);
    }
  }

  @GwtIncompatible
  static <T extends @Nullable Object, K extends Comparable<? super K>, V>
      Collector<T, ?, ImmutableRangeMap<K, V>> toImmutableRangeMap(

  public void testCopyOfEnumMap() {
    EnumMap<AnEnum, String> map = new EnumMap<>(AnEnum.class);
    map.put(AnEnum.B, "foo");
    map.put(AnEnum.C, "bar");
    assertTrue(ImmutableMap.copyOf(map) instanceof ImmutableEnumMap);
  }

  @J2ktIncompatible
  @GwtIncompatible // SerializableTester
  public void testViewSerialization() {
    Map<String, Integer> map = ImmutableMap.of("one", 1, "two", 2, "three", 3);

    EnumMap<K, V> copy = new EnumMap<>((EnumMap<K, ? extends V>) original);
    for (Entry<K, V> entry : copy.entrySet()) {
      checkEntryNotNull(entry.getKey(), entry.getValue());
    }
    return ImmutableEnumMap.asImmutable(copy);
  }

  static final Entry<?, ?>[] EMPTY_ENTRY_ARRAY = new Entry<?, ?>[0];

  abstract static class IteratorBasedImmutableMap<K, V> extends ImmutableMap<K, V> {