+lookupSigOccRn is used for type signatures and pragmas
+Is this valid?
+ module A
+ import M( f )
+ f :: Int -> Int
+ f x = x
+It's clear that the 'f' in the signature must refer to A.f
+The Haskell98 report does not stipulate this, but it will!
+So we must treat the 'f' in the signature in the same way
+as the binding occurrence of 'f', using lookupBndrRn
+
+However, consider this case:
+ import M( f )
+ f :: Int -> Int
+ g x = x
+We don't want to say 'f' is out of scope; instead, we want to
+return the imported 'f', so that later on the reanamer will
+correctly report "misplaced type sig".
+
+\begin{code}
+lookupSigOccRn :: Maybe NameSet -- Just ns => source file; these are the binders
+ -- in the same group
+ -- Nothing => hs-boot file; signatures without
+ -- binders are expected
+ -> Sig RdrName
+ -> Located RdrName -> RnM (Located Name)
+lookupSigOccRn mb_bound_names sig
+ = wrapLocM $ \ rdr_name ->
+ do { mb_name <- lookupBindGroupOcc mb_bound_names (hsSigDoc sig) rdr_name
+ ; case mb_name of
+ Left err -> do { addErr err; return (mkUnboundName rdr_name) }
+ Right name -> return name }
+
+lookupBindGroupOcc :: Maybe NameSet -- Just ns => source file; these are the binders
+ -- in the same group
+ -- Nothing => hs-boot file; signatures without
+ -- binders are expected
+ -> SDoc
+ -> RdrName -> RnM (Either Message Name)
+-- Looks up the RdrName, expecting it to resolve to one of the
+-- bound names passed in. If not, return an appropriate error message
+lookupBindGroupOcc mb_bound_names what rdr_name
+ = do { local_env <- getLocalRdrEnv
+ ; case lookupLocalRdrEnv local_env rdr_name of
+ Just n -> check_local_name n
+ Nothing -> do -- Not defined in a nested scope
+
+ { env <- getGlobalRdrEnv
+ ; let gres = lookupGlobalRdrEnv env (rdrNameOcc rdr_name)
+ ; case (filter isLocalGRE gres) of
+ (gre:_) -> check_local_name (gre_name gre)
+ -- If there is more than one local GRE for the
+ -- same OccName, that will be reported separately
+ [] | null gres -> bale_out_with empty
+ | otherwise -> bale_out_with import_msg
+ }}
+ where
+ check_local_name name -- The name is in scope, and not imported
+ = case mb_bound_names of
+ Just bound_names | not (name `elemNameSet` bound_names)
+ -> bale_out_with local_msg
+ _other -> return (Right name)
+
+ bale_out_with msg
+ = return (Left (sep [ ptext (sLit "The") <+> what
+ <+> ptext (sLit "for") <+> quotes (ppr rdr_name)
+ , nest 2 $ ptext (sLit "lacks an accompanying binding")]
+ $$ nest 2 msg))
+
+ local_msg = parens $ ptext (sLit "The") <+> what <+> ptext (sLit "must be given where")
+ <+> quotes (ppr rdr_name) <+> ptext (sLit "is declared")
+
+ import_msg = parens $ ptext (sLit "You cannot give a") <+> what
+ <+> ptext (sLit "for an imported value")
+
+---------------
+lookupLocalDataTcNames :: NameSet -> SDoc -> RdrName -> RnM [Name]
+-- GHC extension: look up both the tycon and data con
+-- for con-like things
+-- Complain if neither is in scope
+lookupLocalDataTcNames bound_names what rdr_name
+ | Just n <- isExact_maybe rdr_name
+ -- Special case for (:), which doesn't get into the GlobalRdrEnv
+ = return [n] -- For this we don't need to try the tycon too
+ | otherwise
+ = do { mb_gres <- mapM (lookupBindGroupOcc (Just bound_names) what)
+ (dataTcOccs rdr_name)
+ ; let (errs, names) = splitEithers mb_gres
+ ; when (null names) (addErr (head errs)) -- Bleat about one only
+ ; return names }
+
+dataTcOccs :: RdrName -> [RdrName]
+-- If the input is a data constructor, return both it and a type
+-- constructor. This is useful when we aren't sure which we are
+-- looking at.
+dataTcOccs rdr_name
+ | Just n <- isExact_maybe rdr_name -- Ghastly special case
+ , n `hasKey` consDataConKey = [rdr_name] -- see note below
+ | isDataOcc occ = [rdr_name, rdr_name_tc]
+ | otherwise = [rdr_name]
+ where
+ occ = rdrNameOcc rdr_name
+ rdr_name_tc = setRdrNameSpace rdr_name tcName
+
+-- If the user typed "[]" or "(,,)", we'll generate an Exact RdrName,
+-- and setRdrNameSpace generates an Orig, which is fine
+-- But it's not fine for (:), because there *is* no corresponding type
+-- constructor. If we generate an Orig tycon for GHC.Base.(:), it'll
+-- appear to be in scope (because Orig's simply allocate a new name-cache
+-- entry) and then we get an error when we use dataTcOccs in
+-- TcRnDriver.tcRnGetInfo. Large sigh.
+\end{code}
+
+