Yeah. You should be very explicit about it. Certainly not treat it like, “ooh, here are some free bits that I can use to tag things in ad hoc ways (like -1 for

Yeah. You should be very explicit about it. Certainly not treat it like, “ooh, here are some free bits that I can use to tag things in ad hoc ways (like -1 for missing index)”. https://internals.rust-lang.org/t/pre-rfc-nonnan-type/8418 https://internals.rust-lang.org/t/pre-rfc-nonnan-type/8418