I dislike this general mode of defining an ADT by first having to create multiple separate nominal types and then combining them using another free-floating sta

I dislike this general mode of defining an ADT by first having to create multiple separate nominal types and then combining them using another free-floating statement (e.g. 3 dataclasses and then a Union in Python). An ADT is conceptually one thought, so its definition should syntactically be able to be one statement too.