unsafe fn rotate_left_inner(&mut self, mid: usize) {
        debug_assert!(mid * 2 <= self.len());
        unsafe {
            self.wrap_copy(self.head, self.tail, mid);
        }
        self.head = self.wrap_add(self.head, mid);
        self.tail = self.wrap_add(self.tail, mid);
    }
Binary searches this sorted `VecDeque` with
benchmarks/haystacks/code/rust-library.rs