It remains to be seen whether you can have a useful borrow checker on top of a simpler type system (at least, a type system that's significantly simpler so as to meaningfully reduce compile times). I have my doubts, personally.

Relax runs the borrow checker 'lazily' so it already starts your app whilst the borrow checker runs asynchronous. It's jokingly called 'gandalf' because I think It halts the JIT if it finds a problem.

The Goose Programming Language demonstrates an alternative approach that is super simple while being as safe as Rust, or even more if you believe the claim that it doesn’t need unsafe in the language to do anything, unlike Rust.