Yeah, this has been discussed to death and the two main camps seem to be:
- It would be better named
uniqor some other name, but it's impossible to change now mutgives the right intuition most of the time and it's harder to explain uniqueness than mutation, so it's best the way it is.
This is a slight mischaracterization. You can access the data while iterating, you just have to do it through the exclusive borrow taken when you called chunks_mut. You can't do an end-run around an exclusive borrow by using a different reference to the original data; that would defeat the whole point. But you can access the chunk currently being iterated over, and you can access chunks from previous iterations, if you save them.
It's really a fundamental property of iterators: they only give you one thing at a time. In other languages, you may sometimes ignore this by accessing data without going through the iterator. The code you wrote would work translated into C++, for instance. But then C++ allows you to invalidate iterators, leading to data races and memory unsafety, precisely because it has nothing analogous to &mut that would stop you.