Was that an open question or did you have a solution in mind?

More open. I saw it land in stable some time back and haven’t gotten around to playing with it. I honestly haven’t done it much, because usually enums are plentywhen there are a finite set of options.

And yeah, I was thinking of runtime checks with const bounds, like this:

pub struct BoundedI32<const MIN: i32, const MAX: i32>(i32);

impl<const MIN: i32, const MAX: i32> BoundedI32<{ MIN }, { MAX }> {
    pub const MIN: i32 = MAX;
    pub const MAX: i32 = MAX;

    pub fn new(n: i32) -> Self {
        // or an assert
        BoundedI32(n.min(Self::MAX).max(Self::MIN))
    }
}

I’m not sure how magic Ada gets with things, so maybe it’s a lot nicer there, but I honestly can’t see how it could really improve on handling runtime checks.