Anyway, I think I figured it out: Hint is using the Show instance of ErrMsg. But it is defined only in term of errMsgShortString:
https://www.haskell.org/ghc/docs/7.6.3/html/libraries/ghc-7.6.3/src/ErrUtils.html#ErrMsg So we are missing the context infos. On Tue, Sep 9, 2014 at 12:01 AM, Corentin Dupont <corentin.dup...@gmail.com> wrote: > Hi everybody, > I am working with Hint, after some discussion with Daniel Gorin, I decided > to post here, I hope it's the right place. > My problem with Hint is that I cannot get context in error messages while > interpreting a string. If you run the attached file example.hs, you get: > > GhcError {errMsg = "No instance for (GHC.Num.Num GHC.Base.String)\n > arising from a use of `GHC.Num.+'\nPossible fix:\n add an instance > declaration for (GHC.Num.Num GHC.Base.String)"} > > There is no context (line number, code snippets...), plus the error > message uses fully qualified names, which is not very readable. > It's very hard to figure out where the problem is when interpreting a long > string. > But the same error in a file that is loaded with Hint gives the correct > message (uncomment the putStrLn in SomeModule.hs to get it): > > GhcError {errMsg = "<no location info>:\n [1 of 1] Compiling > SomeModule ( SomeModule.hs, interpreted )"},GhcError {errMsg = > "SomeModule.hs:5:22:\n No instance for (Num String) arising from a use > of `+'\n Possible fix: add an instance declaration for (Num String)\n > In the second argument of `($)', namely `\"bar\" + 1'\n In a stmt of a > 'do' block: putStrLn $ \"bar\" + 1\n In the expression:\n do { > putStrLn \"bar\";\n putStrLn $ \"bar\" + 1 }"} > > This error is much better: it gives line number plus some code snippets > ("In the second argument of..."). > > There might be a flag that is not correctly set in GHC? After a quick look > I'm thinking of GHC.DynFlags (I'm no expert). Now it is configured with: > configureDynFlags :: GHC.DynFlags -> GHC.DynFlags > configureDynFlags dflags = dflags{GHC.ghcMode = GHC.CompManager, > GHC.hscTarget = GHC.HscInterpreted, > GHC.ghcLink = GHC.LinkInMemory, > GHC.verbosity = 0} > > Thanks, > Corentin > >
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