I think Go isn't bad choice. It is widely popular, so I'd assume there's plenty of it in training sets and has stable APIs, so even "outdated code" would work. There's also rich ecosystem of static analyzers to keep generated code in check.

On the other hand I think Rust is better by some margin. Type system is obviously a big gain but Rust is very fast moving. When API changes LLMs can't follow and it takes many tries to get it right so it kinda levels out. Code might compile but only on some god-forgotten crate version everybody (but LLM) forgot about.

From personal experience Haskell benefits the most. Not only it has more type system usage than Rust, but its APIs are moving on snail-like pace, which means it doesn't suffer from outdated Rust and code compilable will work just fine. Also I think that Haskell code in training sets is guaranteed to be safe because of language extension system.

How are the generated Haskell programs? I imagine much shorter than Go and easier to eyeball for correctness, but can’t say as I’m not fluent in it. LLM-generated procedural Python scripts are very readable in my experience.