See https://ghc.haskell.org/trac/ghc/ticket/9973, my original file did not in fact exhibit the bug.
On Fri, Jan 9, 2015 at 2:18 PM, Simon Peyton Jones <simo...@microsoft.com> wrote: > Now I get > > Foo1.hs:39:8: Not in scope: ‘SYB.everythingStaged’ > > Foo1.hs:39:29: Not in scope: data constructor ‘SYB.Renamer’ > > > > Do you think you could open a ticket with a reproducible test case? That > would be helpful > > > Simon > > > > *From:* Alan & Kim Zimmerman [mailto:alan.z...@gmail.com] > *Sent:* 09 January 2015 11:54 > > *To:* Simon Peyton Jones > *Cc:* ghc-devs@haskell.org > *Subject:* Re: warn-redundant-constraints present as errors > > > > In the original definingSigsNames requires the constraint, I left that out > to simplify the example, as the movement of the warning to an error still > happens. > > Original definingSigsNames > > ------------------ > -- |Find those type signatures for the specified GHC.Names. > definingSigsNames :: (SYB.Data t) => > [GHC.Name] -- ^ The specified identifiers. > ->t -- ^ A collection of declarations. > ->[GHC.LSig GHC.Name] -- ^ The result. > definingSigsNames pns ds = def ds > where > def decl > = SYB.everythingStaged SYB.Renamer (++) [] ([] `SYB.mkQ` inSig) decl > where > inSig :: (GHC.LSig GHC.Name) -> [GHC.LSig GHC.Name] > inSig (GHC.L l (GHC.TypeSig ns t p)) > | defines' ns /= [] = [(GHC.L l (GHC.TypeSig (defines' ns) t p))] > inSig _ = [] > > defines' (p::[GHC.Located GHC.Name]) > = filter (\(GHC.L _ n) -> n `elem` pns) p > ---------------------- > > > > On Fri, Jan 9, 2015 at 1:48 PM, Simon Peyton Jones <simo...@microsoft.com> > wrote: > > If you remove the constraint from duplicateDecl, then I get > > > > Redundant constraint: SYB.Data t > > In the type signature for: > > definingSigsNames :: SYB.Data t => > > [GHC.Name] -> t -> [GHC.LSig GHC.Name] > > > > which is 100% correct: defininingSigssNames doesn’t use its SYB.Data t > constraint > > > > Simon > > > > *From:* Alan & Kim Zimmerman [mailto:alan.z...@gmail.com] > *Sent:* 09 January 2015 11:22 > *To:* Simon Peyton Jones > *Cc:* ghc-devs@haskell.org > *Subject:* Re: warn-redundant-constraints present as errors > > > > Thanks. > > I've found a case where it warns of a redundant constraint, but if I > remove the constraint I get an error saying the constraint is required > > -------------------------------------------- > import qualified GHC as GHC > > import qualified Data.Generics as SYB > > duplicateDecl :: (SYB.Data t) => -- **** The constraint being warned > against ******* > [GHC.LHsBind GHC.Name] -- ^ The declaration list > ->t -- ^ Any signatures are in here > ->GHC.Name -- ^ The identifier whose definition is to be > duplicated > ->GHC.Name -- ^ The new name (possibly qualified) > ->IO [GHC.LHsBind GHC.Name] -- ^ The result > duplicateDecl decls sigs n newFunName > = do > let sspan = undefined > newSpan <- case typeSig of > [] -> return sspan > _ -> do > let Just sspanSig = getSrcSpan typeSig > toksSig <- getToksForSpan sspanSig > > let [(GHC.L sspanSig' _)] = typeSig > > return sspanSig' > > undefined > where > typeSig = definingSigsNames [n] sigs > > -- |Find those type signatures for the specified GHC.Names. > definingSigsNames :: (SYB.Data t) => > [GHC.Name] -- ^ The specified identifiers. > ->t -- ^ A collection of declarations. > ->[GHC.LSig GHC.Name] -- ^ The result. > definingSigsNames pns ds = def ds > where def = undefined > > getSrcSpan = undefined > getToksForSpan = undefined > > -------------------------------------------- > > > > On Fri, Jan 9, 2015 at 1:08 PM, Simon Peyton Jones <simo...@microsoft.com> > wrote: > > I’ve fixed this > > > > *From:* Alan & Kim Zimmerman [mailto:alan.z...@gmail.com] > *Sent:* 08 January 2015 21:46 > *To:* ghc-devs@haskell.org; Simon Peyton Jones > *Subject:* warn-redundant-constraints present as errors > > > > This is a great feature, here is some feedback > > My syntax highlighter in emacs expects warnings to have the word "warning" > in them. > > So for the two warnings reported below, the first is highlighted as an > error, and the second as a warning > > > Language/Haskell/Refact/Utils/TypeUtils.hs:3036:17: > Redundant constraint: SYB.Data t > In the type signature for: > duplicateDecl :: SYB.Data t => > [GHC.LHsBind GHC.Name] > -> t -> GHC.Name -> GHC.Name -> RefactGhc > [GHC.LHsBind GHC.Name] > > Language/Haskell/Refact/Utils/TypeUtils.hs:3045:7: Warning: > Defined but not used: ‘toks > > This is in a ghci session, and the file loads without problems, so it is > indeed a warning. > > Can we perhaps add the word "Warning" to the output for Redundant > constraints? > > I also had a situation where it asked me to remove a whole lot of > constraints from different functions, I did them in batches, so did not > remove them all from the file at once, and at some point I had to add at > least one of them back, albeit based on an error message. > > > > Regards > > Alan > > > > >
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