A string enumeration has a limited number of values. E.g. type A ("Yes" | "No" | "Maybe") has three values and is a superset of type B ("Yes" | "No"). A function that accepts type A can also accept type B as valid input.

If the value space is defined by a regular expression, as is often the case, the mentioned library could be used to check, at compile-time, which type are subsets of others.