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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