Number 3 is completely not what you want. I mean, you want that in certain cases, but you may also want the exhaustiveness checking. There needs to be two disti

Number 3 is completely not what you want. I mean, you want that in certain cases, but you may also want the exhaustiveness checking. There needs to be two distinct notions here. The notion of a type should convey totality -- this value has a particular 'shape'. The notion described here is not a type, but more like an interface or a trait. In either case, it falls under polymorphism. Person as described here is not a type. That being said, all these things are implemented in PureScript, I believe.