How to express an Enum that renders as Int in JSON?

[bfloch]

I would love to have the strong type guarantee of an Union, but render as an Int into JSON.

What is good way to achieve this?

[bioball]

I think the best thing to do here is to add a type constraint, rather than a union.

num: Int(this == 1 || this == 2 || this == 3)

One other idea is to use a string literal union, and plus a converter. But this feels like a little bit of unnecessary indirection.

num: "1"|"2"|"3"

output {
  renderer = new JsonRenderer {
    converters {
      ["num"] = (it) -> it.toInt()
    }
  }
}