This is where my knowledge gets weak; but, isn't this the type of programming that Ada and various languages that have a matching system are built around? You

This is where my knowledge gets weak; but, isn't this the type of programming that Ada and various languages that have a matching system are built around? You have a function that returns an enum and you have to match all the different states of the enum in your handling code. The ones that call your given function have to do the same and so on and so on. You can still have bugs in this model if I recall, they're just harder to have, I think. Admittedly, this is getting outside of my area of recent experience and expertise, I just swear I've read about something like this before.