It works == it's correct?

Thus all software that can be used is correct?

You know what I meant: How can we have confidence that this implementation of RAR is functionally identical to what it's based on? What would give me the confidence to use it in a critical piece of infrastructure?

I could be correct but way too slow in edge cases (unlikely with Rust but you never know), leaking temporary files, having security holes, etc.

There's much more about correctness of a piece of software than: "produces the same output as the original on x test cases".

I'm not saying it's a bad implementation and, if anything, LLMs are much better at translating/porting existing code (and finding bugs) than at writing things unheard of.

You're basically saying, if I may make a pun: "rust me bro, it's correct".