While in that specific case codegen does sound like the right approach, I think in most regular cases you would be able to get away without it. Honestly, a 64-variant type is not really that common.

I think codegen is OK as long as

- its designed in a way where it doesn't cause users to want or need to modify the generated code (this is the biggest downside of codegen)

- its against "relatively stable" API thing (protobuf / swagger descriptions, DB schema etc).