The odd one out is overflow, and that’s only because it’s well defined (a “program error”) and not UB to overflow in Rust. This gets checked in debug but not currently release, though the spec allows for it.
I assume it's already possible for a user to similarly implement `inbounds!` and `fastmath!` macros in Rust to substitute `[]` for `.get_unchecked()`, etc. (I haven't checked if there are already crates.) But it sounds like it should be easy enough for folks to check performance sensitive regions this way (in particular, loops that may need these flags to vectorize).
I think having the speedbump is worth it.
For example if we were dynamically linking a Rust crate into a Rust binary is it necessary to check boundaries in both or can some of that be deferred because we can assume the binary that will link has already done the boundary checks, etc?
I know it's a bit contrived since ideally we'd just compile statically, but I think it's still potentially valid. If both pieces of software have the guarantees then ideally you can factor out some of the overhead.