Steelman their example. Given that they named the member "MaybeHasCat", it's pretty clearly meant to analogue an Option<Cat>; if you correct the small typo then

Steelman their example. Given that they named the member "MaybeHasCat", it's pretty clearly meant to analogue an Option<Cat>; if you correct the small typo then (make the type of "MaybeHasCat" a pointer, so that it can store nil for the other half of the Maybe), the example behaves exactly as they describe.