[jhc] allowing unqualified method names in instance declarations

Henning Thielemann jhc at henning-thielemann.de
Sat Nov 14 12:58:11 EST 2009

The attached patch shall help accepting an instance declaration like

> import qualified Custom
> instance Custom.Class T where
>    methodA = ...
>    methodB = ...

by translating it to

> instance Custom.Class T where
>    Custom.methodA = ...
>    Custom.methodB = ...

I don't know, whether this also works if you do

> import qualified Custom hiding (methodA, methodB, )

John recently sent two patches to jhc at haskell.org, that are not present in 
the darcs repository. Do they need some confirmation? They work for me, as 
far as I can judge.
-------------- next part --------------
Sat Nov 14 18:57:51 CET 2009  jhc at henning-thielemann.de
  * FrontEnd.Rename: add qualification to unqualified method names in instance declarations

New patches:

[FrontEnd.Rename: add qualification to unqualified method names in instance declarations
jhc at henning-thielemann.de**20091114175751
 Ignore-this: 26d46fa52c4640cd2fe8d529cdb26a07
] hunk ./src/FrontEnd/Rename.hs 192
     f (HsTypeSig sl ns qt) =  [ HsTypeSig sl [n] qt | n <- ns]
     f d = return d
+getTypeClassModule :: HsQualType -> Maybe Module
+getTypeClassModule typ =
+   case hsQualTypeType typ of
+      HsTyApp cls arg ->
+         case hsTypeName cls of
+            Qual moduleName _ -> Just moduleName
+            UnQual _ -> Nothing
+      _ -> error "instance must consist of a type class application"
+qualifyMethodName :: Maybe Module -> HsName -> HsName
+qualifyMethodName moduleName name =
+   case name of
+      Qual _ _ -> name
+      UnQual token ->
+         maybe name (flip Qual token) moduleName
+{- |
+This renaming shall help accepting an instance declaration like
+> import qualified Custom
+> instance Custom.Class T where
+>    methodA = ...
+>    methodB = ...
+by translating it to
+> instance Custom.Class T where
+>    Custom.methodA = ...
+>    Custom.methodB = ...
+I don't know, whether this also works if you do
+> import qualified Custom hiding (methodA, methodB, )
+qualifyInstMethod :: Maybe Module -> HsDecl -> HsDecl
+qualifyInstMethod moduleName decl =
+   case decl of
+      HsPatBind srcLoc (HsPVar {hsPatName = name}) rhs decls ->
+         HsPatBind srcLoc
+            (HsPVar {hsPatName = qualifyMethodName moduleName name})
+            rhs decls
+      HsFunBind matches ->
+         HsFunBind $ map
+            (\(HsMatch matchSrcLoc matchName pats rhs matchDecls) ->
+               HsMatch matchSrcLoc (qualifyMethodName moduleName matchName) pats rhs matchDecls)
+            matches
+      _ -> decl
 instance Rename HsDecl where
     rename (HsPatBind srcLoc hsPat hsRhs {-where-} hsDecls) = do
         withSrcLoc srcLoc $ do
hunk ./src/FrontEnd/Rename.hs 320
         withSrcLoc srcLoc $ do
         updateWith hsQualType $ do
         hsQualType' <- rename hsQualType
-        hsDecls' <- rename hsDecls
+        hsDecls' <- rename $
+           map (qualifyInstMethod (getTypeClassModule hsQualType)) hsDecls
         return (HsInstDecl srcLoc hsQualType' hsDecls')
     rename (HsInfixDecl srcLoc assoc int hsNames) = do
         withSrcLoc srcLoc $ do


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Patch bundle hash:

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