[samus]

Yes, the programmer has to apply the safe workarounds. They always work, but improvements to the borrow checker's heuristics can make them redundant. Removing these workarounds increases performance. A certain minimum set of heuristics are part of the documented language spec by now, and this set is going to become larger with time. If a significant fraction of the ecosystem is affected by a split in heuristics coverage, then Gccrs will have to catch up.

In the PR dug out by a sibling commenter, the improvement to the compiler was indeed to apply the workaround that the programmer had to do. I believe that the churn of new heuristics is going to become smaller, as presumably most of the low-hanging fruits have been harvested by now.