Conversion from pointer to integer about subspace HOT 2 CLOSED

Done by #284

from subspace.

RangeFrom needs to return a lower bound for its size_hint which is normally T::MAX. But if you constructed a RangeFrom over uptr then that doesn't work cuz there's no MAX.

MAX_ADDR would do the wrong thing, cuz that just excludes capabilities from its value, but pointer values may be larger with the capabilities present on CHERI.

MAX_BIT_PATTERN is the closest thing to correct here. If you iterate so far that you are incrementing past MAX_ADDR in the address part of the integer then you've done bad things to your pointer, but that's where the iteration would technically go.

Here MAX being 2^N-1 (not matching uintptr_t on cheri) would be the most correct thing to use, and it's annoying in this case that it does not exist. There's nothing... better.

Edit: Well it turns out uptr is weird in lots of ways so it doesn't have like try_from(unsigned) cuz it needs to be constucted with provenance, so this use case evaporated.

Maybe uptr shouldn't be included in Integer concept though..

from subspace.