[Haskell-cafe] Improving ghc error messages

[Toby Goodwin]

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.