Interesting article: https://izbicki.me/blog/error-messages-in-ghc-vs-g++.html I do hope some of these changes make it into a future ghc. I'd particularly like to highlight this one: No instance for (Show ([a0] -> Int)) arising from a use of `show' Possible fix: add an instance declaration for (Show ([a0] -> Int)) The second line looks like it was added by someone who'd read an article about making error messages helpful: "suggest a possible way to fix the error". Like creating a Show instance for a function type!?! I must have seen that "possible fix" 1000 times, and 999 of them it was nothing like the right fix. Now I know just to ignore it. Simply removing the second line would be an improvement: it doesn't add anything to the first line. Toby.