No payment necessary, but I'd be happy to do a videocall with you. I've implemented tagged unions once, albeit with a very different syntax: https://akkartik.github.io/mu1/html/033exclusive_container.c... (this is a Literate format that eventually tangles into C. The `scenario` blocks show what code in the language would look like. Though none of these is a good example. They all sidestep the type checker to some extent since they're creating raw objects in memory.)

Anyways, I'd be happy to chat with you :) I suspect it'll be a short call. There's a likely a single sentence somewhere that will get you unstuck.