RnNames.lhs

%
% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[RnNames]{Extracting imported and top-level names in scope}

\begin{code}
module RnNames (
	rnImports, getLocalNonValBinders,
	rnExports, extendGlobalRdrEnvRn,
	reportUnusedNames, finishWarnings,
    ) where

#include "HsVersions.h"

import DynFlags
import HsSyn
import RnEnv
import RnHsDoc          ( rnHsDoc )
import IfaceEnv		( ifaceExportNames )
import LoadIface	( loadSrcInterface, loadSysInterface )
import TcRnMonad hiding (LIE)

import PrelNames
import Module
import Name
import NameEnv
import NameSet
import OccName
import HscTypes
import RdrName
import Outputable
import Maybes
import SrcLoc
import FiniteMap
import ErrUtils
import BasicTypes	( WarningTxt(..) )
import DriverPhases	( isHsBoot )
import Util
import FastString
import ListSetOps
import Data.List        ( partition, concatMap, (\\), delete )
import IO		( openFile, IOMode(..) )
import Monad		( when, mplus )
\end{code}



%************************************************************************
%*									*
		rnImports
%*									*
%************************************************************************

\begin{code}
rnImports :: [LImportDecl RdrName]
           -> RnM ([LImportDecl Name], GlobalRdrEnv, ImportAvails,AnyHpcUsage)

rnImports imports
         -- PROCESS IMPORT DECLS
         -- Do the non {- SOURCE -} ones first, so that we get a helpful
         -- warning for {- SOURCE -} ones that are unnecessary
    = do this_mod <- getModule
         implicit_prelude <- doptM Opt_ImplicitPrelude
         let prel_imports	= mkPrelImports this_mod implicit_prelude imports
             (source, ordinary) = partition is_source_import imports
             is_source_import (L _ (ImportDecl _ is_boot _ _ _)) = is_boot

         ifOptM Opt_WarnImplicitPrelude (
            when (notNull prel_imports) $ addWarn (implicitPreludeWarn)
          )

         stuff1 <- mapM (rnImportDecl this_mod) (prel_imports ++ ordinary)
         stuff2 <- mapM (rnImportDecl this_mod) source
         let (decls, rdr_env, imp_avails,hpc_usage) = combine (stuff1 ++ stuff2)
         return (decls, rdr_env, imp_avails,hpc_usage) 

    where
   combine :: [(LImportDecl Name,  GlobalRdrEnv, ImportAvails,AnyHpcUsage)]
           -> ([LImportDecl Name], GlobalRdrEnv, ImportAvails,AnyHpcUsage)
   combine = foldr plus ([], emptyGlobalRdrEnv, emptyImportAvails,False)
        where plus (decl,  gbl_env1, imp_avails1,hpc_usage1)
                   (decls, gbl_env2, imp_avails2,hpc_usage2)
                = (decl:decls, 
                   gbl_env1 `plusGlobalRdrEnv` gbl_env2,
                   imp_avails1 `plusImportAvails` imp_avails2,
		   hpc_usage1 || hpc_usage2)

mkPrelImports :: Module -> Bool -> [LImportDecl RdrName] -> [LImportDecl RdrName]
-- Consruct the implicit declaration "import Prelude" (or not)
--
-- NB: opt_NoImplicitPrelude is slightly different to import Prelude ();
-- because the former doesn't even look at Prelude.hi for instance 
-- declarations, whereas the latter does.
mkPrelImports this_mod implicit_prelude import_decls
  | this_mod == pRELUDE
   || explicit_prelude_import
   || not implicit_prelude
  = []
  | otherwise = [preludeImportDecl]
  where
      explicit_prelude_import
       = notNull [ () | L _ (ImportDecl mod _ _ _ _) <- import_decls, 
	           unLoc mod == pRELUDE_NAME ]

      preludeImportDecl :: LImportDecl RdrName
      preludeImportDecl
        = L loc $
	  ImportDecl (L loc pRELUDE_NAME)
	       False {- Not a boot interface -}
	       False	{- Not qualified -}
	       Nothing	{- No "as" -}
	       Nothing	{- No import list -}

      loc = mkGeneralSrcSpan (fsLit "Implicit import declaration")         


rnImportDecl  :: Module
	      -> LImportDecl RdrName
	      -> RnM (LImportDecl Name, GlobalRdrEnv, ImportAvails,AnyHpcUsage)

rnImportDecl this_mod (L loc (ImportDecl loc_imp_mod_name want_boot
                                         qual_only as_mod imp_details))
  = 
    setSrcSpan loc $ do

	-- If there's an error in loadInterface, (e.g. interface
	-- file not found) we get lots of spurious errors from 'filterImports'
    let
	imp_mod_name = unLoc loc_imp_mod_name
	doc = ppr imp_mod_name <+> ptext (sLit "is directly imported")

    iface <- loadSrcInterface doc imp_mod_name want_boot

	-- Compiler sanity check: if the import didn't say
	-- {-# SOURCE #-} we should not get a hi-boot file
    WARN( not want_boot && mi_boot iface, ppr imp_mod_name ) (do

	-- Issue a user warning for a redundant {- SOURCE -} import
	-- NB that we arrange to read all the ordinary imports before 
	-- any of the {- SOURCE -} imports
    warnIf (want_boot && not (mi_boot iface))
	   (warnRedundantSourceImport imp_mod_name)

    let
	imp_mod	   = mi_module iface
	warns	   = mi_warns iface
	orph_iface = mi_orphan iface 
	has_finsts = mi_finsts iface 
	deps 	   = mi_deps iface

	filtered_exports = filter not_this_mod (mi_exports iface)
	not_this_mod (mod,_) = mod /= this_mod
	-- If the module exports anything defined in this module, just
	-- ignore it.  Reason: otherwise it looks as if there are two
	-- local definition sites for the thing, and an error gets
	-- reported.  Easiest thing is just to filter them out up
	-- front. This situation only arises if a module imports
	-- itself, or another module that imported it.  (Necessarily,
	-- this invoves a loop.)
	--
	-- Tiresome consequence: if you say
	--	module A where
	--	   import B( AType )
	--	   type AType = ...
	--
	--	module B( AType ) where
	--	   import {-# SOURCE #-} A( AType )
	--
	-- then you'll get a 'B does not export AType' message.  Oh well.

	qual_mod_name = case as_mod of
			  Nothing  	    -> imp_mod_name
			  Just another_name -> another_name
	imp_spec  = ImpDeclSpec { is_mod = imp_mod_name, is_qual = qual_only,  
		  		  is_dloc = loc, is_as = qual_mod_name }
    -- in

	-- Get the total exports from this module
    total_avails <- ifaceExportNames filtered_exports

        -- filter the imports according to the import declaration
    (new_imp_details, gbl_env) <- 
        filterImports iface imp_spec imp_details total_avails

    dflags <- getDOpts

    let
	-- Compute new transitive dependencies

 	orphans | orph_iface = ASSERT( not (imp_mod `elem` dep_orphs deps) )
			       imp_mod : dep_orphs deps
		| otherwise  = dep_orphs deps

 	finsts | has_finsts = ASSERT( not (imp_mod `elem` dep_finsts deps) )
			      imp_mod : dep_finsts deps
		| otherwise = dep_finsts deps

	pkg = modulePackageId (mi_module iface)

	(dependent_mods, dependent_pkgs) 
	   | pkg == thisPackage dflags =
	    	-- Imported module is from the home package
		-- Take its dependent modules and add imp_mod itself
		-- Take its dependent packages unchanged
		--
		-- NB: (dep_mods deps) might include a hi-boot file
		-- for the module being compiled, CM. Do *not* filter
		-- this out (as we used to), because when we've
		-- finished dealing with the direct imports we want to
		-- know if any of them depended on CM.hi-boot, in
		-- which case we should do the hi-boot consistency
		-- check.  See LoadIface.loadHiBootInterface
		  ((imp_mod_name, want_boot) : dep_mods deps, dep_pkgs deps)

	   | otherwise =
 	   	-- Imported module is from another package
		-- Dump the dependent modules
		-- Add the package imp_mod comes from to the dependent packages
	         ASSERT2( not (pkg `elem` dep_pkgs deps), ppr pkg <+> ppr (dep_pkgs deps) )
	         ([], pkg : dep_pkgs deps)

	-- True <=> import M ()
	import_all = case imp_details of
			Just (is_hiding, ls) -> not is_hiding && null ls	
			_ 		     -> False

	imports   = ImportAvails { 
			imp_mods     = unitModuleEnv imp_mod [(qual_mod_name, import_all, loc)],
			imp_orphs    = orphans,
			imp_finsts   = finsts,
			imp_dep_mods = mkModDeps dependent_mods,
			imp_dep_pkgs = dependent_pkgs
                   }

	-- Complain if we import a deprecated module
    ifOptM Opt_WarnWarningsDeprecations	(
       case warns of	
	  WarnAll txt -> addWarn (moduleWarn imp_mod_name txt)
	  _    	      -> return ()
     )

    let new_imp_decl = L loc (ImportDecl loc_imp_mod_name want_boot
                                         qual_only as_mod new_imp_details)

    return (new_imp_decl, gbl_env, imports, mi_hpc iface)
    )

warnRedundantSourceImport :: ModuleName -> SDoc
warnRedundantSourceImport mod_name
  = ptext (sLit "Unnecessary {-# SOURCE #-} in the import of module")
          <+> quotes (ppr mod_name)
\end{code}


%************************************************************************
%*									*
		importsFromLocalDecls
%*									*
%************************************************************************

From the top-level declarations of this module produce
  	* the lexical environment
	* the ImportAvails
created by its bindings.  
	
Note [Shadowing in extendGlobalRdrEnvRn]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Usually when etending the GlobalRdrEnv we complain if a new binding
duplicates an existing one.  By adding the bindings one at a time, 
this check also complains if we add two new bindings for the same name.
(Remember that in Template Haskell the duplicates might *already be* 
in the GlobalRdrEnv from higher up the module.)

But with a Template Haskell quotation we want to *shadow*:
	f x = h [d| f = 3 |]
Here the inner binding for 'f' simply shadows the outer one.
And that applies even if the binding for 'f' is in a where-clause,
and hence is in the *local* RdrEnv not the *global* RdrEnv.

Hence the shadowP boolean passed in. 

\begin{code}
extendGlobalRdrEnvRn :: Bool	-- Note [Shadowing in extendGlobalRdrEnvRn]
               	     -> [AvailInfo]
	       	     -> MiniFixityEnv
	       	     -> RnM (TcGblEnv, TcLclEnv)
  -- Updates both the GlobalRdrEnv and the FixityEnv
  -- We return a new TcLclEnv only becuase we might have to
  -- delete some bindings from it; see Note [Shadowing in extendGlobalRdrEnvRn]

extendGlobalRdrEnvRn shadowP avails new_fixities
  = do	{ (gbl_env, lcl_env) <- getEnvs
	; let rdr_env = tcg_rdr_env gbl_env
	      fix_env = tcg_fix_env gbl_env

		-- Delete new_occs from global and local envs
		-- We are going to shadow them
		-- See Note [Shadowing in extendGlobalRdrEnvRn]
	      new_occs = map (nameOccName . gre_name) gres
	      rdr_env1 = hideSomeUnquals rdr_env new_occs
	      lcl_env1 = lcl_env { tcl_rdr = delListFromOccEnv (tcl_rdr lcl_env) new_occs }
	
 		-- Note [Shadowing in extendGlobalRdrEnvRn]
	      (rdr_env2, lcl_env2) | shadowP   = (rdr_env1, lcl_env1)
				   | otherwise = (rdr_env,  lcl_env)

	      rdr_env3 = foldl extendGlobalRdrEnv rdr_env2 gres
	      fix_env' = foldl extend_fix_env     fix_env  gres
	      (rdr_env', dups) = findLocalDupsRdrEnv rdr_env3 new_occs

	      gbl_env' = gbl_env { tcg_rdr_env = rdr_env', tcg_fix_env = fix_env' }
	      
	; mapM_ addDupDeclErr dups
	
	; traceRn (text "extendGlobalRdrEnvRn" <+> (ppr new_fixities $$ ppr fix_env $$ ppr fix_env'))
	; return (gbl_env', lcl_env2) }
  where
    gres = gresFromAvails LocalDef avails

     	--  If there is a fixity decl for the gre, add it to the fixity env
    extend_fix_env fix_env gre 
      | Just (L _ fi) <- lookupFsEnv new_fixities (occNameFS occ)
      = extendNameEnv fix_env name (FixItem occ fi)
      | otherwise
      = fix_env
      where
	name = gre_name gre
        occ  = nameOccName name
\end{code}

@getLocalDeclBinders@ returns the names for an @HsDecl@.  It's
used for source code.

	*** See "THE NAMING STORY" in HsDecls ****

Instances of type families
~~~~~~~~~~~~~~~~~~~~~~~~~~
Indexed data/newtype instances contain data constructors that we need to
collect, too.  Moreover, we need to descend into the data/newtypes instances
of associated families.

We need to be careful with the handling of the type constructor of each type
instance as the family constructor is already defined, and we want to avoid
raising a duplicate declaration error.  So, we make a new name for it, but
don't return it in the 'AvailInfo'.

\begin{code}
getLocalNonValBinders :: HsGroup RdrName -> RnM [AvailInfo]
-- Get all the top-level binders bound the group *except* 
-- for value bindings, which are treated separately
-- Specificaly we return AvailInfo for
--	type decls
--	class decls
--	associated types
--	foreign imports
--	(in hs-boot files) value signatures

getLocalNonValBinders group
  = do 	{ gbl_env <- getGblEnv
	; get_local_binders gbl_env group }

get_local_binders :: TcGblEnv -> HsGroup RdrName -> RnM [GenAvailInfo Name]
get_local_binders gbl_env (HsGroup {hs_valds  = ValBindsIn _ val_sigs,
				    hs_tyclds = tycl_decls, 
				    hs_instds = inst_decls,
				    hs_fords  = foreign_decls })
  = do	{ tc_names_s <- mapM new_tc tycl_decls
	; at_names_s <- mapM inst_ats inst_decls
	; val_names  <- mapM new_simple val_bndrs
	; return (val_names ++ tc_names_s ++ concat at_names_s) }
  where
    mod        = tcg_mod gbl_env
    is_hs_boot = isHsBoot (tcg_src gbl_env) ;

    for_hs_bndrs :: [Located RdrName]
    for_hs_bndrs = [nm | L _ (ForeignImport nm _ _) <- foreign_decls]

    -- In a hs-boot file, the value binders come from the
    --  *signatures*, and there should be no foreign binders 
    val_bndrs :: [Located RdrName]
    val_bndrs | is_hs_boot = [nm | L _ (TypeSig nm _) <- val_sigs]
              | otherwise  = for_hs_bndrs

    new_simple :: Located RdrName -> RnM (GenAvailInfo Name)
    new_simple rdr_name = do
        nm <- newTopSrcBinder mod rdr_name
        return (Avail nm)

    new_tc tc_decl 
      | isFamInstDecl (unLoc tc_decl)
	= do { main_name <- lookupFamInstDeclBndr mod main_rdr
	     ; sub_names <- mapM (newTopSrcBinder mod) sub_rdrs
	     ; return (AvailTC main_name sub_names) }
                	-- main_name is not bound here!
      | otherwise
	= do { main_name <- newTopSrcBinder mod main_rdr
	     ; sub_names <- mapM (newTopSrcBinder mod) sub_rdrs
	     ; return (AvailTC main_name (main_name : sub_names)) }
      where
	(main_rdr : sub_rdrs) = tyClDeclNames (unLoc tc_decl)

    inst_ats inst_decl 
	= mapM new_tc (instDeclATs (unLoc inst_decl))

get_local_binders _ g = pprPanic "get_local_binders" (ppr g)
\end{code}


%************************************************************************
%*									*
\subsection{Filtering imports}
%*									*
%************************************************************************

@filterImports@ takes the @ExportEnv@ telling what the imported module makes
available, and filters it through the import spec (if any).

\begin{code}
filterImports :: ModIface
	      -> ImpDeclSpec			-- The span for the entire import decl
	      -> Maybe (Bool, [LIE RdrName])	-- Import spec; True => hiding
	      -> [AvailInfo]    		-- What's available
	      -> RnM (Maybe (Bool, [LIE Name]), -- Import spec w/ Names
		      GlobalRdrEnv)		-- Same again, but in GRE form
filterImports _ decl_spec Nothing all_avails
  = return (Nothing, mkGlobalRdrEnv (gresFromAvails prov all_avails))
  where
    prov = Imported [ImpSpec { is_decl = decl_spec, is_item = ImpAll }]


filterImports iface decl_spec (Just (want_hiding, import_items)) all_avails
  = do   -- check for errors, convert RdrNames to Names
        opt_typeFamilies <- doptM Opt_TypeFamilies
        items1 <- mapM (lookup_lie opt_typeFamilies) import_items

        let items2 :: [(LIE Name, AvailInfo)]
            items2 = concat items1
		-- NB the AvailInfo may have duplicates, and several items
		--    for the same parent; e.g N(x) and N(y)

            names  = availsToNameSet (map snd items2)
	    keep n = not (n `elemNameSet` names)
	    pruned_avails = filterAvails keep all_avails
	    hiding_prov = Imported [ImpSpec { is_decl = decl_spec, is_item = ImpAll }]

	    gres | want_hiding = gresFromAvails hiding_prov pruned_avails
		 | otherwise   = concatMap (gresFromIE decl_spec) items2

        return (Just (want_hiding, map fst items2), mkGlobalRdrEnv gres)
  where
	-- This environment is how we map names mentioned in the import
        -- list to the actual Name they correspond to, and the name family
        -- that the Name belongs to (the AvailInfo).  The situation is
        -- complicated by associated families, which introduce a three-level
        -- hierachy, where class = grand parent, assoc family = parent, and
        -- data constructors = children.  The occ_env entries for associated
        -- families needs to capture all this information; hence, we have the
        -- third component of the environment that gives the class name (=
        -- grand parent) in case of associated families.
        --
	-- This env will have entries for data constructors too,
	-- they won't make any difference because naked entities like T
	-- in an import list map to TcOccs, not VarOccs.
    occ_env :: OccEnv (Name,	    -- the name
		       AvailInfo,   -- the export item providing the name
		       Maybe Name)  -- the parent of associated types
    occ_env = mkOccEnv_C combine [ (nameOccName n, (n, a, Nothing)) 
			         | a <- all_avails, n <- availNames a]
      where
        -- we know that (1) there are at most entries for one name, (2) their
        -- first component is identical, (3) they are for tys/cls, and (4) one
        -- entry has the name in its parent position (the other doesn't)
        combine (name, AvailTC p1 subs1, Nothing)
		(_   , AvailTC p2 subs2, Nothing)
          = let
	      (parent, subs) = if p1 == name then (p2, subs1) else (p1, subs2)
	    in
	    (name, AvailTC name subs, Just parent)
        combine x y = pprPanic "filterImports/combine" (ppr x $$ ppr y)

    lookup_lie :: Bool -> LIE RdrName -> TcRn [(LIE Name, AvailInfo)]
    lookup_lie opt_typeFamilies (L loc ieRdr)
        = do 
             stuff <- setSrcSpan loc $ 
                      case lookup_ie opt_typeFamilies ieRdr of
                            Failed err  -> addErr err >> return []
                            Succeeded a -> return a
             checkDodgyImport stuff
             return [ (L loc ie, avail) | (ie,avail) <- stuff ]
        where
                -- Warn when importing T(..) if T was exported abstractly
            checkDodgyImport stuff
                | IEThingAll n <- ieRdr, (_, AvailTC _ [_]):_ <- stuff
                = ifOptM Opt_WarnDodgyImports (addWarn (dodgyImportWarn n))
                -- NB. use the RdrName for reporting the warning
            checkDodgyImport _
                = return ()

        -- For each import item, we convert its RdrNames to Names,
        -- and at the same time construct an AvailInfo corresponding
        -- to what is actually imported by this item.
        -- Returns Nothing on error.
        -- We return a list here, because in the case of an import
        -- item like C, if we are hiding, then C refers to *both* a
        -- type/class and a data constructor.  Moreover, when we import
	-- data constructors of an associated family, we need separate
	-- AvailInfos for the data constructors and the family (as they have
	-- different parents).  See the discussion at occ_env.
    lookup_ie :: Bool -> IE RdrName -> MaybeErr Message [(IE Name,AvailInfo)]
    lookup_ie opt_typeFamilies ie 
      = let bad_ie = Failed (badImportItemErr iface decl_spec ie)

            lookup_name rdrName = 
                case lookupOccEnv occ_env (rdrNameOcc rdrName) of
                   Nothing -> bad_ie
                   Just n  -> return n
        in
        case ie of
         IEVar n -> do
             (name, avail, _) <- lookup_name n
             return [(IEVar name, trimAvail avail name)]

         IEThingAll tc -> do
             (name, avail@(AvailTC name2 subs), mb_parent) <- lookup_name tc
             case mb_parent of
	       -- non-associated ty/cls
	       Nothing     -> return [(IEThingAll name, avail)]
	       -- associated ty
	       Just parent -> return [(IEThingAll name, 
				       AvailTC name2 (subs \\ [name])),
				      (IEThingAll name, AvailTC parent [name])]

         IEThingAbs tc
             | want_hiding   -- hiding ( C )
                        -- Here the 'C' can be a data constructor 
                        --  *or* a type/class, or even both
             -> let tc_name = lookup_name tc
                    dc_name = lookup_name (setRdrNameSpace tc srcDataName)
                in
                case catMaybeErr [ tc_name, dc_name ] of
                  []    -> bad_ie
                  names -> return [mkIEThingAbs name | name <- names]
             | otherwise
             -> do nameAvail <- lookup_name tc
                   return [mkIEThingAbs nameAvail]

         IEThingWith tc ns -> do
            (name, AvailTC _ subnames, mb_parent) <- lookup_name tc
	    let 
	      env         = mkOccEnv [(nameOccName s, s) | s <- subnames]
	      mb_children = map (lookupOccEnv env . rdrNameOcc) ns
	    children <- if any isNothing mb_children
                        then bad_ie
                        else return (catMaybes mb_children)
              -- check for proper import of type families
	    when (not opt_typeFamilies && any isTyConName children) $
              Failed (typeItemErr (head . filter isTyConName $ children)
				  (text "in import list"))
            case mb_parent of
	       -- non-associated ty/cls
	      Nothing     -> return [(IEThingWith name children, 
				      AvailTC name (name:children))]
	       -- associated ty
	      Just parent -> return [(IEThingWith name children, 
				      AvailTC name children),
				     (IEThingWith name children, 
				      AvailTC parent [name])]

         _other -> Failed illegalImportItemErr
         -- could be IEModuleContents, IEGroup, IEDoc, IEDocNamed
         -- all errors.

      where
        mkIEThingAbs (n, av, Nothing    ) = (IEThingAbs n, trimAvail av n) 
        mkIEThingAbs (n, _,  Just parent) = (IEThingAbs n, AvailTC parent [n]) 


catMaybeErr :: [MaybeErr err a] -> [a]
catMaybeErr ms =  [ a | Succeeded a <- ms ]
\end{code}

%************************************************************************
%*									*
        Import/Export Utils
%*									*
%************************************************************************

\begin{code}
-- | make a 'GlobalRdrEnv' where all the elements point to the same
-- import declaration (useful for "hiding" imports, or imports with
-- no details).
gresFromAvails :: Provenance -> [AvailInfo] -> [GlobalRdrElt]
gresFromAvails prov avails
  = concatMap (gresFromAvail (const prov)) avails

gresFromAvail :: (Name -> Provenance) -> AvailInfo -> [GlobalRdrElt]
gresFromAvail prov_fn avail
  = [ GRE {gre_name = n, 
	   gre_par = availParent n avail, 
	   gre_prov = prov_fn n}
    | n <- availNames avail ]
  
greAvail :: GlobalRdrElt -> AvailInfo
greAvail gre = mkUnitAvail (gre_name gre) (gre_par gre)

mkUnitAvail :: Name -> Parent -> AvailInfo
mkUnitAvail me (ParentIs p) 		 = AvailTC p  [me]
mkUnitAvail me NoParent | isTyConName me = AvailTC me [me]
			| otherwise	 = Avail me

plusAvail :: GenAvailInfo Name -> GenAvailInfo Name -> GenAvailInfo Name
plusAvail (Avail n1)      (Avail _)        = Avail n1
plusAvail (AvailTC _ ns1) (AvailTC n2 ns2) = AvailTC n2 (ns1 `unionLists` ns2)
plusAvail a1 a2 = pprPanic "RnEnv.plusAvail" (hsep [ppr a1,ppr a2])

availParent :: Name -> AvailInfo -> Parent
availParent _ (Avail _)                 = NoParent
availParent n (AvailTC m _) | n == m    = NoParent
                            | otherwise = ParentIs m

trimAvail :: AvailInfo -> Name -> AvailInfo
trimAvail (Avail n)      _ = Avail n
trimAvail (AvailTC n ns) m = ASSERT( m `elem` ns) AvailTC n [m]

-- | filters 'AvailInfo's by the given predicate
filterAvails  :: (Name -> Bool) -> [AvailInfo] -> [AvailInfo]
filterAvails keep avails = foldr (filterAvail keep) [] avails

-- | filters an 'AvailInfo' by the given predicate
filterAvail :: (Name -> Bool) -> AvailInfo -> [AvailInfo] -> [AvailInfo]
filterAvail keep ie rest =
  case ie of
    Avail n | keep n    -> ie : rest
            | otherwise -> rest
    AvailTC tc ns ->
        let left = filter keep ns in
        if null left then rest else AvailTC tc left : rest

-- | Given an import\/export spec, construct the appropriate 'GlobalRdrElt's.
gresFromIE :: ImpDeclSpec -> (LIE Name, AvailInfo) -> [GlobalRdrElt]
gresFromIE decl_spec (L loc ie, avail)
  = gresFromAvail prov_fn avail
  where
    is_explicit = case ie of
		    IEThingAll name -> \n -> n == name
		    _    	    -> \_ -> True
    prov_fn name = Imported [imp_spec]
	where
	  imp_spec  = ImpSpec { is_decl = decl_spec, is_item = item_spec }
	  item_spec = ImpSome { is_explicit = is_explicit name, is_iloc = loc }

mkChildEnv :: [GlobalRdrElt] -> NameEnv [Name]
mkChildEnv gres = foldr add emptyNameEnv gres
    where
	add (GRE { gre_name = n, gre_par = ParentIs p }) env = extendNameEnv_C (++) env p [n]
	add _                                            env = env

findChildren :: NameEnv [Name] -> Name -> [Name]
findChildren env n = lookupNameEnv env n `orElse` []
\end{code}

---------------------------------------
	AvailEnv and friends

All this AvailEnv stuff is hardly used; only in a very small
part of RnNames.  Todo: remove?
---------------------------------------

\begin{code}
type AvailEnv = NameEnv AvailInfo	-- Maps a Name to the AvailInfo that contains it

emptyAvailEnv :: AvailEnv
emptyAvailEnv = emptyNameEnv

unitAvailEnv :: AvailInfo -> AvailEnv
unitAvailEnv a = unitNameEnv (availName a) a

plusAvailEnv :: AvailEnv -> AvailEnv -> AvailEnv
plusAvailEnv = plusNameEnv_C plusAvail

availEnvElts :: AvailEnv -> [AvailInfo]
availEnvElts = nameEnvElts

addAvail :: AvailEnv -> AvailInfo -> AvailEnv
addAvail avails avail = extendNameEnv_C plusAvail avails (availName avail) avail

mkAvailEnv :: [AvailInfo] -> AvailEnv
	-- 'avails' may have several items with the same availName
	-- E.g  import Ix( Ix(..), index )
	-- will give Ix(Ix,index,range) and Ix(index)
	-- We want to combine these; addAvail does that
mkAvailEnv avails = foldl addAvail emptyAvailEnv avails

-- After combining the avails, we need to ensure that the parent name is the
-- first entry in the list of subnames, if it is included at all.  (Subsequent
-- functions rely on that.)
normaliseAvail :: AvailInfo -> AvailInfo
normaliseAvail avail@(Avail _)     = avail
normaliseAvail (AvailTC name subs) = AvailTC name subs'
  where
    subs' = if name `elem` subs then name : (delete name subs) else subs

-- | combines 'AvailInfo's from the same family
nubAvails :: [AvailInfo] -> [AvailInfo]
nubAvails avails = map normaliseAvail . nameEnvElts . mkAvailEnv $ avails
\end{code}


%************************************************************************
%*									*
\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 rnExports
     = ([LIE Name],             -- Export items with Names
	ExportOccMap,		-- Tracks exported occurrence names
	[AvailInfo])	        -- The accumulated exported stuff
				--   Not nub'd!

emptyExportAccum :: ExportAccum
emptyExportAccum = ([], emptyOccEnv, []) 

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

rnExports :: Bool	-- False => no 'module M(..) where' header at all
          -> Maybe [LIE RdrName]        -- Nothing => no explicit export list
	  -> TcGblEnv
          -> RnM TcGblEnv

	-- Complains if two distinct exports have same OccName
        -- Warns about identical exports.
	-- Complains about exports items not in scope

rnExports explicit_mod exports 
	  tcg_env@(TcGblEnv { tcg_mod     = this_mod,
          	      	      tcg_rdr_env = rdr_env, 
                     	      tcg_imports = imports })
 = do 	{  
	-- 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
        ; dflags <- getDOpts
	; let real_exports 
          	 | explicit_mod = exports
          	 | ghcLink dflags == LinkInMemory = Nothing
          	 | otherwise = Just ([noLoc (IEVar main_RDR_Unqual)])
	  		-- ToDo: the 'noLoc' here is unhelpful if 'main' 
	  		--       turns out to be out of scope

	; (rn_exports, avails) <- exports_from_avail real_exports rdr_env imports this_mod
	; let final_avails = nubAvails avails	     -- Combine families
	
	; return (tcg_env { tcg_exports    = final_avails,
                            tcg_rn_exports = case tcg_rn_exports tcg_env of
						Nothing -> Nothing
						Just _  -> rn_exports,
			    tcg_dus = tcg_dus tcg_env `plusDU` 
				      usesOnly (availsToNameSet final_avails) }) }


exports_from_avail :: Maybe [LIE RdrName]
                         -- Nothing => no explicit export list
                   -> GlobalRdrEnv
                   -> ImportAvails
                   -> Module
                   -> RnM (Maybe [LIE Name], [AvailInfo])

exports_from_avail Nothing rdr_env _imports _this_mod
 = -- The same as (module M) where M is the current module name,
   -- so that's how we handle it.
   let
       avails = [ greAvail gre | gre <- globalRdrEnvElts rdr_env,
                                 isLocalGRE gre ]
   in
   return (Nothing, avails)

exports_from_avail (Just rdr_items) rdr_env imports this_mod
  = do (ie_names, _, exports) <- foldlM do_litem emptyExportAccum rdr_items

       return (Just ie_names, exports)
  where
    do_litem :: ExportAccum -> LIE RdrName -> RnM ExportAccum
    do_litem acc lie = setSrcSpan (getLoc lie) (exports_from_item acc lie)

    kids_env :: NameEnv [Name]	-- Maps a parent to its in-scope children
    kids_env = mkChildEnv (globalRdrEnvElts rdr_env)

    imported_modules = [ qual_name
                       | xs <- moduleEnvElts $ imp_mods imports,
                         (qual_name, _, _) <- xs ]

    exports_from_item :: ExportAccum -> LIE RdrName -> RnM ExportAccum
    exports_from_item acc@(ie_names, occs, exports) 
                      (L loc ie@(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 ;
	       warnIf warn_dup_exports (dupModuleExport mod) ;
	       return acc }

	| otherwise
	= do { implicit_prelude <- doptM Opt_ImplicitPrelude
         ; let { exportValid = (mod `elem` imported_modules)
                            || (moduleName this_mod == mod)
               ; gres = filter (isModuleExported implicit_prelude mod)
                               (globalRdrEnvElts rdr_env)
               }

         ; checkErr exportValid (moduleNotImported mod)
	     ; warnIf (exportValid && null gres) (nullModuleExport mod)

	     ; occs' <- check_occs ie occs (map gre_name gres)
                      -- 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.
	     ; return (L loc (IEModuleContents mod) : ie_names,
                       occs', map greAvail gres ++ exports) }

    exports_from_item acc@(lie_names, occs, exports) (L loc ie)
	| isDoc ie
	= do new_ie <- lookup_doc_ie ie
	     return (L loc new_ie : lie_names, occs, exports)

	| otherwise
        = do (new_ie, avail) <- lookup_ie ie
             if isUnboundName (ieName new_ie)
                  then return acc 	-- Avoid error cascade
                  else do

             occs' <- check_occs ie occs (availNames avail)

             return (L loc new_ie : lie_names, occs', avail : exports)

    -------------
    lookup_ie :: IE RdrName -> RnM (IE Name, AvailInfo)
    lookup_ie (IEVar rdr) 
        = do gre <- lookupGreRn rdr
             return (IEVar (gre_name gre), greAvail gre)

    lookup_ie (IEThingAbs rdr) 
        = do gre <- lookupGreRn rdr
	     let name = gre_name gre
	     case gre_par gre of
		NoParent   -> return (IEThingAbs name, 
				      AvailTC name [name])
		ParentIs p -> return (IEThingAbs name, 
				      AvailTC p [name])

    lookup_ie ie@(IEThingAll rdr) 
        = do name <- lookupGlobalOccRn rdr
	     let kids = findChildren kids_env name
	     when (null kids)
		  (if (isTyConName name) then addWarn (dodgyExportWarn name)
				-- This occurs when you export T(..), but
				-- only import T abstractly, or T is a synonym.  
		   else addErr (exportItemErr ie))
			
             return (IEThingAll name, AvailTC name (name:kids))

    lookup_ie ie@(IEThingWith rdr sub_rdrs)
        = do name <- lookupGlobalOccRn rdr
             if isUnboundName name
                then return (IEThingWith name [], AvailTC name [name])
                else do
             let env = mkOccEnv [ (nameOccName s, s) 
                                | s <- findChildren kids_env name ]
                 mb_names = map (lookupOccEnv env . rdrNameOcc) sub_rdrs
             if any isNothing mb_names
                then do addErr (exportItemErr ie)
                        return (IEThingWith name [], AvailTC name [name])
                else do let names = catMaybes mb_names
                        optTyFam <- doptM Opt_TypeFamilies
                        when (not optTyFam && any isTyConName names) $
                          addErr (typeItemErr ( head
                                              . filter isTyConName 
                                              $ names )
                                              (text "in export list"))
                        return (IEThingWith name names, AvailTC name (name:names))

    lookup_ie _ = panic "lookup_ie"	-- Other cases covered earlier

    -------------
    lookup_doc_ie :: IE RdrName -> RnM (IE Name)
    lookup_doc_ie (IEGroup lev doc) = do rn_doc <- rnHsDoc doc
					 return (IEGroup lev rn_doc)
    lookup_doc_ie (IEDoc doc)       = do rn_doc <- rnHsDoc doc
				         return (IEDoc rn_doc)
    lookup_doc_ie (IEDocNamed str)  = return (IEDocNamed str)
    lookup_doc_ie _ = panic "lookup_doc_ie"	-- Other cases covered earlier


isDoc :: IE RdrName -> Bool
isDoc (IEDoc _)      = True
isDoc (IEDocNamed _) = True
isDoc (IEGroup _ _)  = True
isDoc _ = False

-------------------------------
isModuleExported :: Bool -> ModuleName -> GlobalRdrElt -> Bool
-- True if the thing is in scope *both* unqualified, *and* with qualifier M
isModuleExported implicit_prelude mod (GRE { gre_name = name, gre_prov = prov })
  | implicit_prelude && isBuiltInSyntax name = False
	-- Optimisation: filter out names for built-in syntax
	-- They just clutter up the environment (esp tuples), and the parser
	-- will generate Exact RdrNames for them, so the cluttered
	-- envt is no use.  To avoid doing this filter all the time,
	-- we use -XNoImplicitPrelude as a clue that the filter is
	-- worth while.  Really, it's only useful for GHC.Base and GHC.Tuple.
	--
	-- It's worth doing because it makes the environment smaller for
	-- every module that imports the Prelude
  | otherwise
  = case prov of
	LocalDef    -> moduleName (nameModule name) == mod
	Imported is -> any unQualSpecOK is && any (qualSpecOK mod) is

-------------------------------
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 -> return (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') ;
		     return occs }

	    | otherwise		-- Same occ name but different names: an error
	    ->	do { global_env <- getGlobalRdrEnv ;
  		     addErr (exportClashErr global_env name' name ie' ie) ;
		     return occs }
      where
	name_occ = nameOccName name
\end{code}

%*********************************************************
%*						 	 *
		Deprecations
%*							 *
%*********************************************************

\begin{code}
finishWarnings :: DynFlags -> Maybe WarningTxt 
               -> TcGblEnv -> RnM TcGblEnv
-- (a) Report usage of imports that are deprecated or have other warnings
-- (b) If the whole module is warned about or deprecated, update tcg_warns
--     All this happens only once per module
finishWarnings dflags mod_warn tcg_env
  = do	{ (eps,hpt) <- getEpsAndHpt
	; ifOptM Opt_WarnWarningsDeprecations $
	  mapM_ (check hpt (eps_PIT eps)) all_gres
		-- By this time, typechecking is complete, 
		-- so the PIT is fully populated

	-- Deal with a module deprecation; it overrides all existing warns
	; let new_warns = case mod_warn of
				Just txt -> WarnAll txt
				Nothing  -> tcg_warns tcg_env
	; return (tcg_env { tcg_warns = new_warns }) }
  where
    used_names = allUses (tcg_dus tcg_env) 
	-- Report on all deprecated uses; hence allUses
    all_gres   = globalRdrEnvElts (tcg_rdr_env tcg_env)

    check hpt pit gre@(GRE {gre_name = name, gre_prov = Imported (imp_spec:_)})
      | name `elemNameSet` used_names
      ,	Just deprec_txt <- lookupImpDeprec dflags hpt pit gre
      = addWarnAt (importSpecLoc imp_spec)
		  (sep [ptext (sLit "In the use of") <+> 
			pprNonVarNameSpace (occNameSpace (nameOccName name)) <+> 
		 	quotes (ppr name),