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Speaking bluntly: Almost everyone using the language at present is getting by just fine without this. As a normal Rust developer, I don’t particularly care about a formal language specification existing. It’s a long way down my list of nice-to-haves—yeah, it would be nice to have, but there are quite a few other things that would be more nice to have. The core team are compiler and language developers. I’d much rathe…
I think the argument is that if you said that about C++ everyone would be "yeah: this is just a useful tool, so why do I care?"... but Rust is about safety, and if you don't have a formal model of the language by what reasoning could you possibly have to know it is safe? (And, in fact, every now and then--much less often these days, but still--someone finds a soundness issue in Rust itself, something you would hope t…
Having said that, I'm totally happy if there can be formal verification of these things. However, I certainly don't consider it to be job 1.