// Safety: the following two methods require that the rotation amount
// be less than half the length of the deque.
//
- // `wrap_copy` requres that `min(x, cap() - x) + copy_len <= cap()`,
+ // `wrap_copy` requires that `min(x, cap() - x) + copy_len <= cap()`,
// but than `min` is never more than half the capacity, regardless of x,
// so it's sound to call here because we're calling with something
// less than half the length, which is never above half the capacity.