It's a great attempt, just like ReasonML. Maybe the 'data' could be called 'enum'? I believe Rust/Swift ADT definition use keyword 'enum' and it might make it

It's a great attempt, just like ReasonML. Maybe the 'data' could be called 'enum'? I believe Rust/Swift ADT definition use keyword 'enum' and it might make it more familiar to the mainstream. While the 'await' is pretty recognizable, the word itself seems to be too coupled with asynchronous operation too much.