Union Type (singular) straw man proposal

Hello all, I'll start by saying I've been lurking for about six weeks and reading everything on the list since then although I was on the list for a short period many years ago. I recently took on a role as "WordPress Engineering Team Lead" and as such have gotten much more interested in revisiting PHP's feature set hence why I rejoined the list. I've been working with PHP for 12 years, programming professionally for 32 years and GoLang the last 1+ years. So while I specialize in WordPress and PHP/MySQL, my experience has been in other frameworks and languages for most of my professional programming career. I have been planning to write up an RFC regarding union types, but had not found the time. Seeing that Nikita has started a new RFC for Union Types v2 — how do you all keep up with that guy?!? — I realized that I better get these ideas at somewhat documented and presented or the train will have fully left the station. What I am proposing can be layered on top of Nikita's proposal, and was influenced by what I have learned using Go. It is not a Go feature, but inspired by the Go interface{} type (which is a very different concept compared to interfaces in PHP, btw.) It is a straw man proposal which means it is not a fully-fleshed out RFC, but if I waited until I had the time to write an RFC then PHP 8 might already be out: Without further ado: https://gist.github.com/mikeschinkel/50aec7094f5643223d28674639f9f117 <https://gist.github.com/mikeschinkel/50aec7094f5643223d28674639f9f117> Since I'm effectively new to the list this time please go easy on me? :-) Thanks in advance for all your consideration. -Mike Schinkel