If we are gonna go down that rabbit hole, then the natural conclusion is Haskell.

How good are LLMs at understanding Haskell errors and then dealing with them?

The last time I had a go with Haskell, the errors reminded me so much of hellish terminal compilers from the 80s and 90s that I quickly gave up. Been there, not doing that again.

Which seems pretty reasonable tbh. Claude Code is amazing with Elm in my experience.