except it isn't bit slice, it isn't indexing within a range - it's just integer type that only allows values up to 2^width, with same alignment rounding up as with the rest
It's a bit slice if you put it in a packed struct.
I like them, they're nicer than C's bitfields: The order isn't implementation-defined, and the types remember their range rather than being converted to a power-of-two size upon read. (Maybe that's possible with C23 _BitInt(n), I haven't tried if those work in bitfields)
