It’s useful for Option to be iterable so that it works with things like .flat_map(), and it’s useful to be able to count from an arbitrary iterable. .iter().co

It’s useful for Option to be iterable so that it works with things like .flat_map(), and it’s useful to be able to count from an arbitrary iterable. .iter().count() is a contrived way to find the length of a Vec though, since .len() is clearer and faster.