+%************************************************************************
+%* *
+\subsection{Export list processing}
+%* *
+%************************************************************************
+
+Processing the export list.
+
+You might think that we should record things that appear in the export
+list as ``occurrences'' (using @addOccurrenceName@), but you'd be
+wrong. We do check (here) that they are in scope, but there is no
+need to slurp in their actual declaration (which is what
+@addOccurrenceName@ forces).
+
+Indeed, doing so would big trouble when compiling @PrelBase@, because
+it re-exports @GHC@, which includes @takeMVar#@, whose type includes
+@ConcBase.StateAndSynchVar#@, and so on...
+
+\begin{code}
+type ExportAccum -- The type of the accumulating parameter of
+ -- the main worker function in exportsFromAvail
+ = ([ModuleName], -- 'module M's seen so far
+ ExportOccMap, -- Tracks exported occurrence names
+ NameSet) -- The accumulated exported stuff
+emptyExportAccum = ([], emptyOccEnv, emptyNameSet)
+
+type ExportOccMap = OccEnv (Name, IE RdrName)
+ -- Tracks what a particular exported OccName
+ -- in an export list refers to, and which item
+ -- it came from. It's illegal to export two distinct things
+ -- that have the same occurrence name
+
+
+exportsFromAvail :: Bool -- False => no 'module M(..) where' header at all
+ -> Maybe [Located (IE RdrName)] -- Nothing => no explicit export list
+ -> RnM NameSet
+ -- Complains if two distinct exports have same OccName
+ -- Warns about identical exports.
+ -- Complains about exports items not in scope
+
+exportsFromAvail explicit_mod exports
+ = do { TcGblEnv { tcg_rdr_env = rdr_env,
+ tcg_imports = imports } <- getGblEnv ;
+
+ -- If the module header is omitted altogether, then behave
+ -- as if the user had written "module Main(main) where..."
+ -- EXCEPT in interactive mode, when we behave as if he had
+ -- written "module Main where ..."
+ -- Reason: don't want to complain about 'main' not in scope
+ -- in interactive mode
+ ghci_mode <- getGhciMode ;
+ let { real_exports
+ | explicit_mod = exports
+ | ghci_mode == Interactive = Nothing
+ | otherwise = Just [noLoc (IEVar main_RDR_Unqual)] } ;
+ exports_from_avail real_exports rdr_env imports }
+
+
+exports_from_avail Nothing rdr_env imports
+ = -- Export all locally-defined things
+ -- We do this by filtering the global RdrEnv,
+ -- keeping only things that are locally-defined
+ return (mkNameSet [ gre_name gre
+ | gre <- globalRdrEnvElts rdr_env,
+ isLocalGRE gre ])
+
+exports_from_avail (Just export_items) rdr_env
+ (ImportAvails { imp_qual = mod_avail_env,
+ imp_env = entity_avail_env })
+ = foldlM (exports_from_litem) emptyExportAccum
+ export_items `thenM` \ (_, _, exports) ->
+ returnM exports
+
+ where
+ exports_from_litem :: ExportAccum -> Located (IE RdrName) -> RnM ExportAccum
+ exports_from_litem acc = addLocM (exports_from_item acc)
+
+ exports_from_item :: ExportAccum -> IE RdrName -> RnM ExportAccum
+ exports_from_item acc@(mods, occs, exports) ie@(IEModuleContents mod)
+ | mod `elem` mods -- Duplicate export of M
+ = do { warn_dup_exports <- doptM Opt_WarnDuplicateExports ;
+ warnIf warn_dup_exports (dupModuleExport mod) ;
+ returnM acc }
+
+ | otherwise
+ = case lookupModuleEnvByName mod_avail_env mod of
+ Nothing -> addErr (modExportErr mod) `thenM_`
+ returnM acc
+
+ Just avail_env
+ -> let
+ new_exports = [ name | avail <- availEnvElts avail_env,
+ name <- availNames avail,
+ inScopeUnqual rdr_env name ]
+ in
+
+ -- This check_occs not only finds conflicts between this item
+ -- and others, but also internally within this item. That is,
+ -- if 'M.x' is in scope in several ways, we'll have several
+ -- members of mod_avails with the same OccName.
+ check_occs ie occs new_exports `thenM` \ occs' ->
+ returnM (mod:mods, occs', addListToNameSet exports new_exports)
+
+ exports_from_item acc@(mods, occs, exports) ie
+ = lookupGlobalOccRn (ieName ie) `thenM` \ name ->
+ if isUnboundName name then
+ returnM acc -- Avoid error cascade
+ else
+ -- Get the AvailInfo for the parent of the specified name
+ let
+ parent = nameParent name
+ avail = lookupAvailEnv entity_avail_env parent
+ in
+ -- Filter out the bits we want
+ case filterAvail ie avail of {
+ Nothing -> -- Not enough availability
+ addErr (exportItemErr ie) `thenM_`
+ returnM acc ;
+
+ Just export_avail ->
+
+ -- Phew! It's OK! Now to check the occurrence stuff!
+
+ let
+ new_exports = availNames export_avail
+ in
+ checkForDodgyExport ie new_exports `thenM_`
+ check_occs ie occs new_exports `thenM` \ occs' ->
+ returnM (mods, occs', addListToNameSet exports new_exports)
+ }
+
+
+-------------------------------
+inScopeUnqual :: GlobalRdrEnv -> Name -> Bool
+-- Checks whether the Name is in scope unqualified,
+-- regardless of whether it's ambiguous or not
+inScopeUnqual env n = any unQualOK (lookupGRE_Name env n)
+
+-------------------------------
+checkForDodgyExport :: IE RdrName -> [Name] -> RnM ()
+checkForDodgyExport (IEThingAll tc) [n] = addWarn (dodgyExportWarn tc)
+ -- This occurs when you import T(..), but
+ -- only export T abstractly. The single [n]
+ -- in the AvailTC is the type or class itself
+checkForDodgyExport _ _ = return ()
+
+-------------------------------
+check_occs :: IE RdrName -> ExportOccMap -> [Name] -> RnM ExportOccMap
+check_occs ie occs names
+ = foldlM check occs names
+ where
+ check occs name
+ = case lookupOccEnv occs name_occ of
+ Nothing -> returnM (extendOccEnv occs name_occ (name, ie))
+
+ Just (name', ie')
+ | name == name' -- Duplicate export
+ -> do { warn_dup_exports <- doptM Opt_WarnDuplicateExports ;
+ warnIf warn_dup_exports (dupExportWarn name_occ ie ie') ;
+ returnM occs }
+
+ | otherwise -- Same occ name but different names: an error
+ -> do { global_env <- getGlobalRdrEnv ;
+ addErr (exportClashErr global_env name name' ie ie') ;
+ returnM occs }
+ where
+ name_occ = nameOccName name