Unsafe code is a really hot subject in the Rust project already and there's tons of research work around that done by Ralf: https://www.ralfj.de/blog/categories/research.html.

He's also building Rust tooling for finding bugs in this space, see for example miri.

https://play.rust-lang.org/?version=stable&mode=debug&editio...

(click "Tools" -> "Miri")

This will figure out that you do produce an illegal borrow in that unsafe code.