[silisili]

I'm not sure how your snippet above exemplifies memory unsafety.

Concurrent access does let you hit some 'fun' behavior, but you have to be doing pretty dumb things to hit them. And while the implementation may be able to save you from something like that, such things would likely bubble up elsewhere(disk i/o, network i/o, etc) if doing that kind of thing.

[DangitBobby]

I would also consider this to be memory unsafe. If you have an "array", you should not be able to index (or slice) beyond its bounds. If you are allowed to do so, you may have unpredictable junk in your array.

[morelisp]

This is not any usual definition of memory-unsafety; the contents may be useless to your task at hand but it's well-defined.