Rust is great for some many practical purposes in modern software development. But who needs any of that? What are the oldest things we can target with standard Rustc?
ARM is a pretty well supported architecture, right? ARM is older than you might...
UPDATE : I would probably talk about this different now that I know a bit more about how something like this would actually be formalized, but this post is an analogy more than an actual formal model, even if a variation can be formalized.