Should we have a saturating shift function?

[larseggert]

This seems good. Should we have a saturating shift function? This isn't the first time we've needed this sort of thing.

Originally posted by @martinthomson in #2294 (comment)

[mxinden]

Until https://doc.rust-lang.org/beta/std/num/struct.Saturating.html#method.rotate_left is stable, we might as well just copy the implementation.

[martinthomson]

Rotation isn't what we want. The code we'd need is here: https://doc.rust-lang.org/beta/src/core/num/saturating.rs.html#82 (commented out with a big question about what it means). Perhaps we can provide some useful input to that discussion.

[martinthomson]

I've commented on rust-lang/rust#103440, which covers the language enhancements.