You are right, and thank you for pointing this out. I've opened an issue:

https://github.com/ivov/lisette/issues/12

I have a few approaches in mind and will be addressing this soon.

To be fair, I feel like the language is widely criticized for this particular choice and it's not a pattern you tend to see with newer APIs.

It's a really valid FFI concern though! And I feel like superset languages like this live or die on their ability to be integrated smoothly side-by-side with the core language (F#, Scala, Kotlin, Typescript, Rescript)

To be honest you could easily mark this as an additional (adt) type if that suits you better. Its a halting situation no matter how you twist it.