Add `maybe!` macro equivalent to `try!`

[hauleth]

Rendered

[cassiersg]

For reference, there also exists a try_opt crate that does the same thing as soma.

[hauleth]

@cassiersg I wasn't aware that this already exist. 👍

[ticki]

See also #243

[4xrsJCr9]

Please consider renaming this macro to 'maybe'.

[reem]

Some alternatives: Option::and_then or try! with Option::ok_or/Option::ok_or_else depending on what's appropriate.

[alexcrichton]

🔔 This RFC is now entering its week-long final comment period 🔔

The libs team feels that we are likely to not merge this for now in light of trait-based exception handling having recently landed. We're likely to change try! to simply become ? in which case this may mesh more nicely with catch { ... } as proposed there.

[daboross]

I feel like this doesn't really need to be a part of the standard library, as it has a lot smaller use case than try! does. I mean it wouldn't be too bad to add it, but it might just be extra bloat.

[skade]

I would strongly avoid naming the macro maybe! for similarity with the type of the same name in other programming languages. Rust uses Option instead of Maybe, maybe! sounds like diverging from that.

[k3d3]

Having something that deals with Options being called maybe! is confusing IMO - it should be called some!, option!, or opt!.

[nrc]

I strongly want a facility for doing this and in the past I've argued for a macro (so many projects have their own for doing this!), however, it seems the best way forward now is to make ? work with Option, so I think we should not accept this RFC (I also don't like maybe as a name, fwiw) and push on getting ? to support Option asap.

[alexcrichton]

The libs team discussed this RFC during triage yesterday and the conclusion was to close (in the face of trait-based exception handling). Thanks again though for the RFC @hauleth!