On Sat, Jul 12, 2008 at 10:44 AM, Max Bolingbroke
I had some free time this afternoon so I put together an (experimental) patch for GHC that implements helpful errors messages. Have a look at this GHCi session to see what I mean:
"" $ stage2/ghc-inplace --interactive -fhelpful-errors GHCi, version 6.9.20080711: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer ... linking ... done. Loading package base ... linking ... done. Prelude> let foo = 10 Prelude> foa
<interactive>:1:0: Not in scope: `foa' Maybe you meant one of: `foo' `fst' `not' -- Maybe the matching threshold could stand to be tweaked
That's pretty cool. Unfortunately in my early Haskell days the 'not in scope' errors were the only ones I _did_ understand. It would be nice to human-friendlify the other types of errors. I'm not judging your work though, this is helpful, and the other types of errors are of course much harder to friendlify. On the topic of things that aren't stupid complaints by me, a typo is the most likely cause for not in scope errors. As Evan points out, I think it would be more helpful to search for matching names in imported modules to see if the name was accidentally not qualified or exported. I don't know about this fuzzy matching business, since when I go to the line of the error message, I'm going to see my typo and what I meant. I don't think I'd ever use the suggestions... Luke