Feature suggestion: ensure_some!() for unwrapping options

[SimonSapin]

I found it it pretty common to want to get at the value inside an Option, or propagate an error if it’s None. For example with Iterator::next, u32::checked_sub, etc. Do you think the macro below would make a good addition to the library?

macro_rules! ensure_some {
    ($option: expr, $($tt:tt)+) => {
        if let Some(value) = $option {
            value
        } else {
            anyhow::bail!($($tt)+)
        }
    };
}

[dtolnay]

I would prefer to leave it to downstream crates to define that macro for themself, and not build it into this crate.

[dtolnay]

For static string messages, anyhow::Context is pretty good for the same use case:
let jobs = NonZeroU32::new(args.jobs).context("number of jobs must be non-zero")?;

There is .with_context(|| format!("...", ...))? but it wouldn't really be less verbose than the if let.

[SimonSapin]

I didn’t realize Context was also implemented for Option, thanks