value-fixture/src/org/immutables/fixture/encoding/defs/OptionalList2.java
private static <T> List<T> createSafeList(Iterable<T> iterable) {
    List<T> list = StreamSupport.stream(iterable.spliterator(), false)
        .map(element -> Objects.requireNonNull(element, "element"))
        .collect(Collectors.toList());

    return Collections.unmodifiableList(list);
  }
private static <T> List<T> createSafeList(Iterable<T> iterable) {
    List<T> list = StreamSupport.stream(iterable.spliterator(), false)
        .map(element -> Objects.requireNonNull(element, "element"))
        .collect(Collectors.toList());

    return Collections.unmodifiableList(list);
  }
}