What's the point of LengthAtMost32?

I was reading the PR of adding proper into_iter on arrays (see https://github.com/rust-lang/rust/pull/62959/files ), but then I found that for some reason they implement it only for arrays <= 32.

My question is why? What would break if we implement it for any arrays? I don't see any harm here.

Is there any hardcoded limit in the compiler which will break in this case?

Before the compiler had const generics at all, array implementations were all duplicated for [T; 0], [T; 1], ... [T; 32] using macros.

Now that we do have const generics, those have been consolidated with const type parameters for the length. However, as that feature is still unstable, we want to have an easy way to go back, so we keep the former limit using LengthAtMost32. If we need to rip out const generics for some reason, we still can.

Eventually, this should be opened up to all array lengths.


Cool. I actually thought something similar but didn't touch the truth anyway.

Thanks for quick reply.

The PR that added it links the the tracking issue discussing why it's done this way: