The problem with .map().collect()? is that it does not short-circuit.

Consider:

  for item in iterable.iter() {
    item.foo()?;
  }

You will exit the loop as soon as there is an error. But with .map().collect(), you iterate over the whole list, and then exit if one of the items yield an error.

EDIT: Thank you for your answers, it seems I was wrong and it does short-cricuit!