The basic example of crate imap as of v2.4.1 shows a function fetch_inbox_top that logs in to a mail server, fetches a message, logs out and returns a Result<_>.

I don’t understand why the call to logout is made explicitely because logout is skipped if e.g. a message cannot be found and the function exits early, right?

1. Why does Session not implement the Drop trait?
2. What would be the idiomatic/easiest/best way to ensure logout is called? Assuming that the function doesn’t panic (though the sample can) and always uses Err in case of any error.