There are languages like Dafny that permit you to declare pre- and post-conditions for functions. Dafny in particular tries to automatically verify or disprove these claims with an SMT solver. It would be neat if LLMs could read a human-written contract and iterate on the implementation until it's provably correct. I imagine you'd have much higher confidence in the results using this technique, but I doubt that available models are trained appropriately for this use case.