On Thu, Sep 18, 2014 at 8:13 AM, 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!?!
That's a bit unfair. The second line does add a valuable tip in many cases, because often you might indeed just have forgotten to give an instance. That being said, the error reporting mechanism could use a bit of tweaking when it comes to the Show class and the function type, because: 1) Show is used all the time (namely in ghci), and 2) Functions are very often involved in newbie errors (such as forgetting to supply an argument to a function, or doing things like |map(succ [1,2,3])|. Cheers, Pedro
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. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe