First there's no "code". There are many different variations. Doing basic UI in React is way different from doing low-level embedded code with locking and mutexes, etc.

AI is quite good at what I call "code in-painting": you give the outlines, and it fills the boring stuff (writing out UI, writing out the test content, etc)

It's still VERY bad at maths. For technical reasons (you can't differentiate a SAT solver, so for now LLMs are mostly "hallucinating" plausible-sounding reasonings, but not doing any "solid math") And when you start reasoning about locks / mutexes, etc, what you're really doing is (some primitive form of) maths and logic.

For now, there's no easy-to-use framework (eg a streamlined way to encode the constraints in Lean / Coq etc) or AI capacities that allow to bridge something like this to make it safe for very "math-like" code. And it's easy to shoot yourself in the foot.