You cannot refactor C++ to Rust at the individual function level without good Rust<->C++ interop. The Carbon docs go into this at a sufficient level of detail;

You cannot refactor C++ to Rust at the individual function level without good Rust<->C++ interop. The Carbon docs go into this at a sufficient level of detail; TLDR, interop paths exist but are insufficient and are actively being researched (and Chrome devs are heavily involved in said research). And as to your initial comment, of course safety is important, but if you don't understand why things like maintainability and performance are _also_ critically important, then your opinion is not sufficiently well-informed.