Comment by davidhyde

It would also be nice to be able to use unsigned types (like u8, u16 and u32) to index into slices and arrays up until usize (usually a u32 or u64). Using a usize often seems wasteful for indexing into small arrays and slices and casting makes the code look ugly (also dangerous because the effect of casting is checked by the developer, not the compiler). Admittedly, this would have the downside of having code that compiles on one architecture but not another so it’s probably not worth it.