It depends on what effort you're using etc. As an example [1] of what codex is capable of, here's hugo (written in golang) ported to TypeScript - and then a TypeScript to Rust transpiler which converts arbitrary TypeScript into Rust.

The TypeScript code which was transpiled into Rust (and is compatible with most hugo templates) runs faster than the original hugo.

[1]: https://github.com/tsoniclang/tsonic-examples/tree/main/rust...

The transpiler is still WIP, but the fact that it can do this says a lot of about how far LLMs have come.