> This is different case than mutating a dict while iterate it. In this case the failure is caused by GC, and it is always hard to handle such issues. In case of a dict you can just copy it before iterating. But what to do with RuntimeError from slicing a list if copying a list is vulnerable to the same issue?

This issue was found by fuzzing with weird destructor. I don't think that anyone will hit the bug with "normal" code in the wild. Otherwise, we would have get a bug report before this one.