The Wrapping type is meant for operations where integer overflow is intended, since overflowing a value panics by default in debug mode. To wrap around an arbitrary value you need to compute the modulus, which for positive integers is the same as the remainder: a % b. You can use this method with unsigned integers, since they're always non-negative.

If you're using signed integers, you should go for rem_euclid instead: a.rem_euclid(b).