ch09-02: ? may be used with Result or Option

[BooleanCat]

ch09-02 makes (what seems to me, I'm still learning!) to be a false claim that ? may only be used with Result.

Yet when I tried this it compiled just fine:

fn hello() -> Option<String> {
    Some(String::from("hello"))?;
    Some(String::from("bye"))
}

I'm a little uncomfortable with the change I'm suggesting here since it seems strange to claim that ? works with Option without demonstrating it as such - however this section of the book doesn't seem like the right place for that. Any advice?

[carols10cents]

to be a false claim that ? may only be used with Result.

Yes, it used to be the case that ? could only be used with Result-- the ability to use it with Option was only recently added and we haven't gotten around to documenting it yet :)

Thank you for the suggested fix -- I think we're going to fix it a different way though, because the rest of this paragraph only talks about Result and doesn't really explain what using ? on Option does, exactly.

This already has a bug to track it: #1679 so thank you for the reminder, and we'll fix this soon!

[UnHumbleBen]

Seeing as how the other pull request for this issue (#1713) was rejected for being too large, this pull request should be merge as a temporary fix instead, to at least let the reader know that ? can be used on Option, even if the explanation doesn't exist yet.

[UnHumbleBen]

Alternatively I made my own pull request with a more subtle change which may be easier to incorporate as a temporary fix.
#2047