type ExportAccum -- The type of the accumulating parameter of
-- the main worker function in rnExports
= ([LIE Name], -- Export items with Names
- ExportOccMap, -- Tracks exported occurrence names
+ ExportOccMap, -- Tracks exported occurrence names
[AvailInfo]) -- The accumulated exported stuff
-- Not nub'd!
exports_from_item :: ExportAccum -> LIE RdrName -> RnM ExportAccum
exports_from_item acc@(ie_names, occs, exports)
- (L loc ie@(IEModuleContents mod))
+ (L loc (IEModuleContents mod))
| let earlier_mods = [ mod | (L _ (IEModuleContents mod)) <- ie_names ]
, mod `elem` earlier_mods -- Duplicate export of M
= do { warn_dup_exports <- doptM Opt_WarnDuplicateExports ;
-- The qualified and unqualified version of all of
-- these names are, in effect, used by this export
- ; occs' <- check_occs ie occs names
+ ; occs' <- check_occs (IEModuleContents mod) occs names
-- This check_occs not only finds conflicts
-- between this item and others, but also
-- internally within this item. That is, if
-------------------------------
check_occs :: IE RdrName -> ExportOccMap -> [Name] -> RnM ExportOccMap
-check_occs ie occs names
+check_occs ie occs names -- 'names' are the entities specifed by 'ie'
= foldlM check occs names
where
check occs name
| name == name' -- Duplicate export
-- But we don't want to warn if the same thing is exported
-- by two different module exports. See ticket #4478.
- -> do unless (diffModules ie ie') $ do
+ -> do unless (dupExport_ok name ie ie') $ do
warn_dup_exports <- doptM Opt_WarnDuplicateExports
warnIf warn_dup_exports (dupExportWarn name_occ ie ie')
return occs
return occs }
where
name_occ = nameOccName name
- -- True if the two IE RdrName are different module exports.
- diffModules (IEModuleContents n1) (IEModuleContents n2) = n1 /= n2
- diffModules _ _ = False
+
+
+dupExport_ok :: Name -> IE RdrName -> IE RdrName -> Bool
+-- The Name is exported by both IEs. Is that ok?
+-- "No" iff the name is mentioned explicitly in both IEs
+-- or one of the IEs mentions the name *alone*
+-- "Yes" otherwise
+--
+-- Examples of "no": module M( f, f )
+-- module M( fmap, Functor(..) )
+-- module M( module Data.List, head )
+--
+-- Example of "yes"
+-- module M( module A, module B ) where
+-- import A( f )
+-- import B( f )
+--
+-- Example of "yes" (Trac #2436)
+-- module M( C(..), T(..) ) where
+-- class C a where { data T a }
+-- instace C Int where { data T Int = TInt }
+--
+-- Example of "yes" (Trac #2436)
+-- module Foo ( T ) where
+-- data family T a
+-- module Bar ( T(..), module Foo ) where
+-- import Foo
+-- data instance T Int = TInt
+
+dupExport_ok n ie1 ie2
+ = not ( single ie1 || single ie2
+ || (explicit_in ie1 && explicit_in ie2) )
+ where
+ explicit_in (IEModuleContents _) = False -- module M
+ explicit_in (IEThingAll r) = nameOccName n == rdrNameOcc r -- T(..)
+ explicit_in _ = True
+
+ single (IEVar {}) = True
+ single (IEThingAbs {}) = True
+ single _ = False
\end{code}
%*********************************************************
; let usage :: [ImportDeclUsage]
usage = findImportUsage imports rdr_env (Set.elems uses)
+ ; traceRn (ptext (sLit "Import usage") <+> ppr usage)
; ifDOptM Opt_WarnUnusedImports $
mapM_ warnUnusedImport usage
; ifDOptM Opt_D_dump_minimal_imports $
printMinimalImports usage }
where
- explicit_import (L loc _) = isGoodSrcSpan loc
+ explicit_import (L loc _) = case loc of
+ UnhelpfulSpan _ -> False
+ RealSrcSpan _ -> True
-- Filter out the implicit Prelude import
-- which we do not want to bleat about
\end{code}