Ugh. They didn't compile any C to Rust. They modified the F*-to-C compiler to emit Rust instead. So they compiled F* to safe Rust. And they couldn't even do that 100% reliably; some valid F* constructs couldn't be translated into Rust properly. They could either translate it into Rust code that wouldn't compile, or translate it into similar-looking Rust code that would compile, but would produce incorrect results.

Flagged, this is just a lie of a title.