Also, you can totally write (with a bit of unsafe) a LendingIterator with runtime checks instead of this compile time check, with the cost of 1 byte per item (a

Also, you can totally write (with a bit of unsafe) a LendingIterator with runtime checks instead of this compile time check, with the cost of 1 byte per item (and of course the possibility of a runtime panic). So this is really only relevant for library authors and those who want to wring the last bit of performance out of their program.