feat(options2): better test for layered_option

[lionel-rowe]

The existing test can be solved with the following:

while let Some(integer) = optional_integers.pop() {
    assert_eq!(integer.unwrap(), range);

Similarly with expect(...), unwrap_or(0), unwrap_or_default(), etc. However, none of these solutions use the learning point of stacking Option<T>s.

The updated test can only be solved by stacking Option<T>s:

while let Some(Some(integer)) = optional_integers.pop() {
    assert_eq!(integer, cursor);

With the updated test, using unwrap or expect will panic when it hits the None value, and using unwrap_or or unwrap_or_default will cause the final assert_eq!(cursor, 0) to panic.

[shadows-withal]

@all-contributors please add @lionel-rowe for content

[allcontributors]

@shadows-withal

I've put up a pull request to add @lionel-rowe! 🎉