Comment by tialaramex

Unsurprisingly Rust can target Morello already but it comes at a performance penalty. Whereas C has myriad integer types for special purposes, Rust only has a pair - a signed and unsigned integer of the same size as pointers. Since on CHERI a pointer is a different size from an address, Rust pays the price of using a 128-bit integer (to store pointers) as its array index.

The potential change would make these types address-sized, so you can't fit a whole pointer in them on Morello where the pointer isn't just an address. On other platforms this change makes no practical difference.