Making the borrow checker know about the liveness of variables outside of scope is on the todo list. Like all of the borrow checker, it's fairly tricky to implement properly, but it should be doable. I don't think this issue leaves "a lot to be desired" though; it's a relatively minor tweak on the overall semantics.

Having a borrow check is important, because otherwise you're left with iterator invalidation and numerous other memory safety holes.