Erlang X Union

This is the second type system they tried to add to Erlang, right? Or am I remembering wrong? The second, there is motion going on the technically a good tape. But yeah, maybe to do that, can I go full circle now? So given that we talked about all of this, like with two builds sometimes, but with a boilerplate that's necessary to write a bunch of stacks,. for example, I'm a fitness library to tackle exactly this problem. And I call it X union. It has been born out of my own kind of itch, because I'm just, I'm working on this little project of mine where I want to model those things.