I started to look at this, and one of the first complaints from rust about removing Clone is the number of RefOrMut::swap calls we have. These are potentially an antipattern with containers, in that we'll likely be expecting to read a bunch of references out rather than owned contents, and cloning the container (and contents) while close to mandatory for Ref variants normally, probably isn't what we want with containers.

Probably not a big deal at the moment in that I think most Ref variants are e.g. abomonation related, and that's a different antipattern. But we might want to have a think about the right way to encourage good behavior here, and whether we are even doing the right thing ourselves.