It might still be tricky or even impossible to do that, that sounds very specific. If it is truly impossible we in the UCG would love to hear that. :) We don't want to rule out any legitimate use-case without reasonable alternatives (and yes those are deliberately fuzzy terms), but we do want to guarantee some baseline of optimizations that almost all code can benefit from, and it is okay for us if niche code then becomes harder to write. If we accidentally make it impossible to write though, that would be an issue we'd love to know about.
I have it on my todo list to revisit the Rust implementation at some point.
Now that const generics have landed at least some parts of the code should be easier to write.
I'll throw you folks an issue over the fence, should I run into the same problems again, pinky swear ;)
UCG and their Zulip are a good place for thorny "is this UB" questions, yeah. We're thin on documentation indeed. First need to figure out all the rules, then find enough people to write all the educational material to teach them to everyone else. ;)
