Almost useless in my opinion (because not a lot of practical invariants can be expressed with simple ranges) and will only create confusion when using non-0, no

Almost useless in my opinion (because not a lot of practical invariants can be expressed with simple ranges) and will only create confusion when using non-0, non-1 based indexing and also create confusion about the representation/the space required for representation. The examples shown there are similar to the Animal-Cat-Dog examples that are popular to "prove" that classes and inheritance are useful. That, plus the type incompatibility that arises from mixing such types with other integer types.