-- |
-- #name_types#
-- GHC uses several kinds of name internally:
--
-- * 'OccName.OccName' represents names as strings with just a little more information:
--   the \"namespace\" that the name came from, e.g. the namespace of value, type constructors or
--   data constructors
--
-- * 'RdrName.RdrName': see "RdrName#name_types"
--
-- * 'Name.Name': see "Name#name_types"
--
-- * 'Id.Id': see "Id#name_types"
--
-- * 'Var.Var': see "Var#name_types"
module OccName (
	-- * The 'NameSpace' type
	NameSpace, -- Abstract
	
	-- ** Construction
	-- $real_vs_source_data_constructors
	tcName, clsName, tcClsName, dataName, varName, 
	tvName, srcDataName,

	-- ** Pretty Printing
	pprNameSpace, pprNonVarNameSpace, pprNameSpaceBrief,

	-- * The 'OccName' type
	OccName, 	-- Abstract, instance of Outputable
	pprOccName, 

	-- ** Construction	
	mkOccName, mkOccNameFS, 
	mkVarOcc, mkVarOccFS,
	mkDataOcc, mkDataOccFS,
	mkTyVarOcc, mkTyVarOccFS,
	mkTcOcc, mkTcOccFS,
	mkClsOcc, mkClsOccFS,
        mkDFunOcc,
	mkTupleOcc, 
	setOccNameSpace,

	-- ** Derived 'OccName's
        isDerivedOccName,
	mkDataConWrapperOcc, mkWorkerOcc, mkDefaultMethodOcc, mkGenDefMethodOcc,
	mkDerivedTyConOcc, mkNewTyCoOcc, mkClassOpAuxOcc,
        mkCon2TagOcc, mkTag2ConOcc, mkMaxTagOcc,
  	mkClassTyConOcc, mkClassDataConOcc, mkDictOcc, mkIPOcc, 
 	mkSpecOcc, mkForeignExportOcc, mkGenOcc1, mkGenOcc2,
 	mkGenD, mkGenR, mkGenRCo, mkGenC, mkGenS,
	mkDataTOcc, mkDataCOcc, mkDataConWorkerOcc,
	mkSuperDictSelOcc, mkLocalOcc, mkMethodOcc, mkInstTyTcOcc,
	mkInstTyCoOcc, mkEqPredCoOcc,
        mkVectOcc, mkVectTyConOcc, mkVectDataConOcc, mkVectIsoOcc,
        mkPDataTyConOcc, mkPDataDataConOcc,
        mkPReprTyConOcc, 
        mkPADFunOcc,

	-- ** Deconstruction
	occNameFS, occNameString, occNameSpace, 

	isVarOcc, isTvOcc, isTcOcc, isDataOcc, isDataSymOcc, isSymOcc, isValOcc,
	parenSymOcc, startsWithUnderscore, 
	
	isTcClsNameSpace, isTvNameSpace, isDataConNameSpace, isVarNameSpace, isValNameSpace,

	isTupleOcc_maybe,

	-- * The 'OccEnv' type
	OccEnv, emptyOccEnv, unitOccEnv, extendOccEnv, mapOccEnv,
	lookupOccEnv, mkOccEnv, mkOccEnv_C, extendOccEnvList, elemOccEnv,
	occEnvElts, foldOccEnv, plusOccEnv, plusOccEnv_C, extendOccEnv_C,
        extendOccEnv_Acc, filterOccEnv, delListFromOccEnv, delFromOccEnv,

	-- * The 'OccSet' type
	OccSet, emptyOccSet, unitOccSet, mkOccSet, extendOccSet, 
	extendOccSetList,
	unionOccSets, unionManyOccSets, minusOccSet, elemOccSet, occSetElts, 
	foldOccSet, isEmptyOccSet, intersectOccSet, intersectsOccSet,
                  
	-- * Tidying up
	TidyOccEnv, emptyTidyOccEnv, tidyOccName, initTidyOccEnv,

	-- * Lexical characteristics of Haskell names
	isLexCon, isLexVar, isLexId, isLexSym,
	isLexConId, isLexConSym, isLexVarId, isLexVarSym,
	startsVarSym, startsVarId, startsConSym, startsConId
    ) where

#include "Typeable.h"

import Util
import Unique
import BasicTypes
import UniqFM
import UniqSet
import FastString
import Outputable
import Binary
import StaticFlags( opt_SuppressUniques )
import Data.Char
import Data.Data

data NameSpace = VarName	-- Variables, including "real" data constructors
	       | DataName	-- "Source" data constructors 
	       | TvName		-- Type variables
	       | TcClsName	-- Type constructors and classes; Haskell has them
				-- in the same name space for now.
	       deriving( Eq, Ord )
   {-! derive: Binary !-}

-- Note [Data Constructors]  
-- see also: Note [Data Constructor Naming] in DataCon.lhs
--
-- $real_vs_source_data_constructors
-- There are two forms of data constructor:
--
--	[Source data constructors] The data constructors mentioned in Haskell source code
--
--	[Real data constructors] The data constructors of the representation type, which may not be the same as the source type
--
-- For example:
--
-- > data T = T !(Int, Int)
--
-- The source datacon has type @(Int, Int) -> T@
-- The real   datacon has type @Int -> Int -> T@
--
-- GHC chooses a representation based on the strictness etc.

tcName, clsName, tcClsName :: NameSpace
dataName, srcDataName      :: NameSpace
tvName, varName            :: NameSpace

-- Though type constructors and classes are in the same name space now,
-- the NameSpace type is abstract, so we can easily separate them later
tcName    = TcClsName		-- Type constructors
clsName   = TcClsName		-- Classes
tcClsName = TcClsName		-- Not sure which!

dataName    = DataName
srcDataName = DataName	-- Haskell-source data constructors should be
			-- in the Data name space

tvName      = TvName
varName     = VarName

isDataConNameSpace :: NameSpace -> Bool
isDataConNameSpace DataName = True
isDataConNameSpace _        = False

isTcClsNameSpace :: NameSpace -> Bool
isTcClsNameSpace TcClsName = True
isTcClsNameSpace _         = False

isTvNameSpace :: NameSpace -> Bool
isTvNameSpace TvName = True
isTvNameSpace _      = False

isVarNameSpace :: NameSpace -> Bool	-- Variables or type variables, but not constructors
isVarNameSpace TvName  = True
isVarNameSpace VarName = True
isVarNameSpace _       = False

isValNameSpace :: NameSpace -> Bool
isValNameSpace DataName = True
isValNameSpace VarName  = True
isValNameSpace _        = False

pprNameSpace :: NameSpace -> SDoc
pprNameSpace DataName  = ptext (sLit "data constructor")
pprNameSpace VarName   = ptext (sLit "variable")
pprNameSpace TvName    = ptext (sLit "type variable")
pprNameSpace TcClsName = ptext (sLit "type constructor or class")

pprNonVarNameSpace :: NameSpace -> SDoc
pprNonVarNameSpace VarName = empty
pprNonVarNameSpace ns = pprNameSpace ns

pprNameSpaceBrief :: NameSpace -> SDoc
pprNameSpaceBrief DataName  = char 'd'
pprNameSpaceBrief VarName   = char 'v'
pprNameSpaceBrief TvName    = ptext (sLit "tv")
pprNameSpaceBrief TcClsName = ptext (sLit "tc")

data OccName = OccName 
    { occNameSpace  :: !NameSpace
    , occNameFS     :: !FastString
    }
    deriving Typeable

instance Eq OccName where
    (OccName sp1 s1) == (OccName sp2 s2) = s1 == s2 && sp1 == sp2

instance Ord OccName where
	-- Compares lexicographically, *not* by Unique of the string
    compare (OccName sp1 s1) (OccName sp2 s2) 
	= (s1  `compare` s2) `thenCmp` (sp1 `compare` sp2)

instance Data OccName where
  -- don't traverse?
  toConstr _   = abstractConstr "OccName"
  gunfold _ _  = error "gunfold"
  dataTypeOf _ = mkNoRepType "OccName"

instance Outputable OccName where
    ppr = pprOccName

pprOccName :: OccName -> SDoc
pprOccName (OccName sp occ) 
  = getPprStyle $ \ sty ->
    if codeStyle sty 
    then ftext (zEncodeFS occ)
    else pp_occ <> pp_debug sty
  where
    pp_debug sty | debugStyle sty = braces (pprNameSpaceBrief sp)
	         | otherwise      = empty

    pp_occ | opt_SuppressUniques = text (strip_th_unique (unpackFS occ))
           | otherwise           = ftext occ

	-- See Note [Suppressing uniques in OccNames]
    strip_th_unique ('[' : c : _) | isAlphaNum c = []
    strip_th_unique (c : cs) = c : strip_th_unique cs
    strip_th_unique []       = []

mkOccName :: NameSpace -> String -> OccName
mkOccName occ_sp str = OccName occ_sp (mkFastString str)

mkOccNameFS :: NameSpace -> FastString -> OccName
mkOccNameFS occ_sp fs = OccName occ_sp fs

mkVarOcc :: String -> OccName
mkVarOcc s = mkOccName varName s

mkVarOccFS :: FastString -> OccName
mkVarOccFS fs = mkOccNameFS varName fs

mkDataOcc :: String -> OccName
mkDataOcc = mkOccName dataName

mkDataOccFS :: FastString -> OccName
mkDataOccFS = mkOccNameFS dataName

mkTyVarOcc :: String -> OccName
mkTyVarOcc = mkOccName tvName

mkTyVarOccFS :: FastString -> OccName
mkTyVarOccFS fs = mkOccNameFS tvName fs

mkTcOcc :: String -> OccName
mkTcOcc = mkOccName tcName

mkTcOccFS :: FastString -> OccName
mkTcOccFS = mkOccNameFS tcName

mkClsOcc :: String -> OccName
mkClsOcc = mkOccName clsName

mkClsOccFS :: FastString -> OccName
mkClsOccFS = mkOccNameFS clsName

instance Uniquable OccName where
      -- See Note [The Unique of an OccName]
  getUnique (OccName VarName   fs) = mkVarOccUnique  fs
  getUnique (OccName DataName  fs) = mkDataOccUnique fs
  getUnique (OccName TvName    fs) = mkTvOccUnique   fs
  getUnique (OccName TcClsName fs) = mkTcOccUnique   fs

newtype OccEnv a = A (UniqFM a)

emptyOccEnv :: OccEnv a
unitOccEnv  :: OccName -> a -> OccEnv a
extendOccEnv :: OccEnv a -> OccName -> a -> OccEnv a
extendOccEnvList :: OccEnv a -> [(OccName, a)] -> OccEnv a
lookupOccEnv :: OccEnv a -> OccName -> Maybe a
mkOccEnv     :: [(OccName,a)] -> OccEnv a
mkOccEnv_C   :: (a -> a -> a) -> [(OccName,a)] -> OccEnv a
elemOccEnv   :: OccName -> OccEnv a -> Bool
foldOccEnv   :: (a -> b -> b) -> b -> OccEnv a -> b
occEnvElts   :: OccEnv a -> [a]
extendOccEnv_C :: (a->a->a) -> OccEnv a -> OccName -> a -> OccEnv a
extendOccEnv_Acc :: (a->b->b) -> (a->b) -> OccEnv b -> OccName -> a -> OccEnv b
plusOccEnv     :: OccEnv a -> OccEnv a -> OccEnv a
plusOccEnv_C   :: (a->a->a) -> OccEnv a -> OccEnv a -> OccEnv a
mapOccEnv      :: (a->b) -> OccEnv a -> OccEnv b
delFromOccEnv 	   :: OccEnv a -> OccName -> OccEnv a
delListFromOccEnv :: OccEnv a -> [OccName] -> OccEnv a
filterOccEnv	   :: (elt -> Bool) -> OccEnv elt -> OccEnv elt

emptyOccEnv  	 = A emptyUFM
unitOccEnv x y = A $ unitUFM x y 
extendOccEnv (A x) y z = A $ addToUFM x y z
extendOccEnvList (A x) l = A $ addListToUFM x l
lookupOccEnv (A x) y = lookupUFM x y
mkOccEnv     l    = A $ listToUFM l
elemOccEnv x (A y) 	 = elemUFM x y
foldOccEnv a b (A c)	 = foldUFM a b c 
occEnvElts (A x)	 = eltsUFM x
plusOccEnv (A x) (A y)	 = A $ plusUFM x y 
plusOccEnv_C f (A x) (A y)	 = A $ plusUFM_C f x y 
extendOccEnv_C f (A x) y z   = A $ addToUFM_C f x y z
extendOccEnv_Acc f g (A x) y z   = A $ addToUFM_Acc f g x y z
mapOccEnv f (A x)	 = A $ mapUFM f x
mkOccEnv_C comb l = A $ addListToUFM_C comb emptyUFM l
delFromOccEnv (A x) y    = A $ delFromUFM x y
delListFromOccEnv (A x) y  = A $ delListFromUFM x y
filterOccEnv x (A y)       = A $ filterUFM x y

instance Outputable a => Outputable (OccEnv a) where
    ppr (A x) = ppr x

type OccSet = UniqSet OccName

emptyOccSet	  :: OccSet
unitOccSet	  :: OccName -> OccSet
mkOccSet          :: [OccName] -> OccSet
extendOccSet      :: OccSet -> OccName -> OccSet
extendOccSetList  :: OccSet -> [OccName] -> OccSet
unionOccSets	  :: OccSet -> OccSet -> OccSet
unionManyOccSets  :: [OccSet] -> OccSet
minusOccSet 	  :: OccSet -> OccSet -> OccSet
elemOccSet	  :: OccName -> OccSet -> Bool
occSetElts	  :: OccSet -> [OccName]
foldOccSet	  :: (OccName -> b -> b) -> b -> OccSet -> b
isEmptyOccSet	  :: OccSet -> Bool
intersectOccSet   :: OccSet -> OccSet -> OccSet
intersectsOccSet  :: OccSet -> OccSet -> Bool

emptyOccSet	  = emptyUniqSet
unitOccSet	  = unitUniqSet
mkOccSet          = mkUniqSet
extendOccSet	  = addOneToUniqSet
extendOccSetList  = addListToUniqSet
unionOccSets      = unionUniqSets
unionManyOccSets  = unionManyUniqSets
minusOccSet	  = minusUniqSet
elemOccSet        = elementOfUniqSet
occSetElts        = uniqSetToList
foldOccSet	  = foldUniqSet
isEmptyOccSet     = isEmptyUniqSet
intersectOccSet   = intersectUniqSets
intersectsOccSet s1 s2 = not (isEmptyOccSet (s1 `intersectOccSet` s2))

occNameString :: OccName -> String
occNameString (OccName _ s) = unpackFS s

setOccNameSpace :: NameSpace -> OccName -> OccName
setOccNameSpace sp (OccName _ occ) = OccName sp occ

isVarOcc, isTvOcc, isTcOcc, isDataOcc :: OccName -> Bool

isVarOcc (OccName VarName _) = True
isVarOcc _                   = False

isTvOcc (OccName TvName _) = True
isTvOcc _                  = False

isTcOcc (OccName TcClsName _) = True
isTcOcc _                     = False

-- | /Value/ 'OccNames's are those that are either in 
-- the variable or data constructor namespaces
isValOcc :: OccName -> Bool
isValOcc (OccName VarName  _) = True
isValOcc (OccName DataName _) = True
isValOcc _                    = False

isDataOcc (OccName DataName _) = True
isDataOcc (OccName VarName s)  
  | isLexCon s = pprPanic "isDataOcc: check me" (ppr s)
		-- Jan06: I don't think this should happen
isDataOcc _                    = False

-- | Test if the 'OccName' is a data constructor that starts with
-- a symbol (e.g. @:@, or @[]@)
isDataSymOcc :: OccName -> Bool
isDataSymOcc (OccName DataName s) = isLexConSym s
isDataSymOcc (OccName VarName s)  
  | isLexConSym s = pprPanic "isDataSymOcc: check me" (ppr s)
		-- Jan06: I don't think this should happen
isDataSymOcc _                    = False
-- Pretty inefficient!

-- | Test if the 'OccName' is that for any operator (whether 
-- it is a data constructor or variable or whatever)
isSymOcc :: OccName -> Bool
isSymOcc (OccName DataName s)  = isLexConSym s
isSymOcc (OccName TcClsName s) = isLexConSym s
isSymOcc (OccName VarName s)   = isLexSym s
isSymOcc (OccName TvName s)    = isLexSym s
-- Pretty inefficient!

parenSymOcc :: OccName -> SDoc -> SDoc
-- ^ Wrap parens around an operator
parenSymOcc occ doc | isSymOcc occ = parens doc
		    | otherwise    = doc

startsWithUnderscore :: OccName -> Bool
-- ^ Haskell 98 encourages compilers to suppress warnings about unsed
-- names in a pattern if they start with @_@: this implements that test
startsWithUnderscore occ = case occNameString occ of
			     ('_' : _) -> True
			     _other    -> False

mk_deriv :: NameSpace 
	 -> String		-- Distinguishes one sort of derived name from another
	 -> String
	 -> OccName

mk_deriv occ_sp sys_prefix str = mkOccName occ_sp (sys_prefix ++ str)

isDerivedOccName :: OccName -> Bool
isDerivedOccName occ = 
   case occNameString occ of
     '$':c:_ | isAlphaNum c -> True
     ':':c:_ | isAlphaNum c -> True
     _other                 -> False

mkDataConWrapperOcc, mkWorkerOcc, mkDefaultMethodOcc, mkGenDefMethodOcc,
  	mkDerivedTyConOcc, mkClassTyConOcc, mkClassDataConOcc, mkDictOcc,
 	mkIPOcc, mkSpecOcc, mkForeignExportOcc, mkGenOcc1, mkGenOcc2,
 	mkGenD, mkGenR, mkGenRCo,
	mkDataTOcc, mkDataCOcc, mkDataConWorkerOcc, mkNewTyCoOcc,
	mkInstTyCoOcc, mkEqPredCoOcc, mkClassOpAuxOcc,
        mkCon2TagOcc, mkTag2ConOcc, mkMaxTagOcc,
	mkVectOcc, mkVectTyConOcc, mkVectDataConOcc, mkVectIsoOcc,
	mkPDataTyConOcc, mkPDataDataConOcc, mkPReprTyConOcc, mkPADFunOcc
   :: OccName -> OccName

-- These derived variables have a prefix that no Haskell value could have
mkDataConWrapperOcc = mk_simple_deriv varName  "$W"
mkWorkerOcc         = mk_simple_deriv varName  "$w"
mkDefaultMethodOcc  = mk_simple_deriv varName  "$dm"
mkGenDefMethodOcc   = mk_simple_deriv varName  "$gdm"
mkClassOpAuxOcc     = mk_simple_deriv varName  "$c"
mkDerivedTyConOcc   = mk_simple_deriv tcName   ":"	-- The : prefix makes sure it classifies
mkClassTyConOcc     = mk_simple_deriv tcName   "T:"	-- as a tycon/datacon
mkClassDataConOcc   = mk_simple_deriv dataName "D:"	-- We go straight to the "real" data con
							-- for datacons from classes
mkDictOcc	    = mk_simple_deriv varName  "$d"
mkIPOcc		    = mk_simple_deriv varName  "$i"
mkSpecOcc	    = mk_simple_deriv varName  "$s"
mkForeignExportOcc  = mk_simple_deriv varName  "$f"
mkNewTyCoOcc        = mk_simple_deriv tcName   "NTCo:"	-- Coercion for newtypes
mkInstTyCoOcc       = mk_simple_deriv tcName   "TFCo:"   -- Coercion for type functions
mkEqPredCoOcc	    = mk_simple_deriv tcName   "$co"

-- used in derived instances
mkCon2TagOcc        = mk_simple_deriv varName  "$con2tag_"
mkTag2ConOcc        = mk_simple_deriv varName  "$tag2con_"
mkMaxTagOcc         = mk_simple_deriv varName  "$maxtag_"

-- Generic derivable classes (old)
mkGenOcc1           = mk_simple_deriv varName  "$gfrom"
mkGenOcc2           = mk_simple_deriv varName  "$gto" 

-- Generic deriving mechanism (new)
mkGenD         = mk_simple_deriv tcName "D1"

mkGenC :: OccName -> Int -> OccName
mkGenC occ m   = mk_deriv tcName ("C1_" ++ show m) (occNameString occ)

mkGenS :: OccName -> Int -> Int -> OccName
mkGenS occ m n = mk_deriv tcName ("S1_" ++ show m ++ "_" ++ show n)
                   (occNameString occ)

mkGenR   = mk_simple_deriv tcName "Rep_"
mkGenRCo = mk_simple_deriv tcName "CoRep_"

-- data T = MkT ... deriving( Data ) needs defintions for 
--	$tT   :: Data.Generics.Basics.DataType
--	$cMkT :: Data.Generics.Basics.Constr
mkDataTOcc = mk_simple_deriv varName  "$t"
mkDataCOcc = mk_simple_deriv varName  "$c"

-- Vectorisation
mkVectOcc          = mk_simple_deriv varName  "$v_"
mkVectTyConOcc     = mk_simple_deriv tcName   ":V_"
mkVectDataConOcc   = mk_simple_deriv dataName ":VD_"
mkVectIsoOcc       = mk_simple_deriv varName  "$VI_"
mkPDataTyConOcc    = mk_simple_deriv tcName   ":VP_"
mkPDataDataConOcc  = mk_simple_deriv dataName ":VPD_"
mkPReprTyConOcc    = mk_simple_deriv tcName   ":VR_"
mkPADFunOcc        = mk_simple_deriv varName  "$PA_"

mk_simple_deriv :: NameSpace -> String -> OccName -> OccName
mk_simple_deriv sp px occ = mk_deriv sp px (occNameString occ)

-- Data constructor workers are made by setting the name space
-- of the data constructor OccName (which should be a DataName)
-- to VarName
mkDataConWorkerOcc datacon_occ = setOccNameSpace varName datacon_occ 

mkSuperDictSelOcc :: Int 	-- ^ Index of superclass, e.g. 3
		  -> OccName 	-- ^ Class, e.g. @Ord@
		  -> OccName	-- ^ Derived 'Occname', e.g. @$p3Ord@
mkSuperDictSelOcc index cls_occ
  = mk_deriv varName "$p" (show index ++ occNameString cls_occ)

mkLocalOcc :: Unique 		-- ^ Unique to combine with the 'OccName'
	   -> OccName		-- ^ Local name, e.g. @sat@
	   -> OccName		-- ^ Nice unique version, e.g. @$L23sat@
mkLocalOcc uniq occ
   = mk_deriv varName ("$L" ++ show uniq) (occNameString occ)
	-- The Unique might print with characters 
	-- that need encoding (e.g. 'z'!)

-- | Derive a name for the representation type constructor of a
-- @data@\/@newtype@ instance.
mkInstTyTcOcc :: String 		-- ^ Family name, e.g. @Map@
              -> OccSet                 -- ^ avoid these Occs
	      -> OccName		-- ^ @R:Map@
mkInstTyTcOcc str set =
  chooseUniqueOcc tcName ('R' : ':' : str) set

mkDFunOcc :: String		-- ^ Typically the class and type glommed together e.g. @OrdMaybe@.
				-- Only used in debug mode, for extra clarity
	  -> Bool		-- ^ Is this a hs-boot instance DFun?
          -> OccSet             -- ^ avoid these Occs
	  -> OccName		-- ^ E.g. @$f3OrdMaybe@

-- In hs-boot files we make dict funs like $fx7ClsTy, which get bound to the real
-- thing when we compile the mother module. Reason: we don't know exactly
-- what the  mother module will call it.

mkDFunOcc info_str is_boot set
  = chooseUniqueOcc VarName (prefix ++ info_str) set
  where
    prefix | is_boot   = "$fx"
	   | otherwise = "$f"

chooseUniqueOcc :: NameSpace -> String -> OccSet -> OccName
chooseUniqueOcc ns str set = loop (mkOccName ns str) (0::Int)
  where
  loop occ n
   | occ `elemOccSet` set = loop (mkOccName ns (str ++ show n)) (n+1)
   | otherwise            = occ

mkMethodOcc :: OccName -> OccName
mkMethodOcc occ@(OccName VarName _) = occ
mkMethodOcc occ                     = mk_simple_deriv varName "$m" occ

type TidyOccEnv = OccEnv Int	-- The in-scope OccNames
	-- Range gives a plausible starting point for new guesses

emptyTidyOccEnv :: TidyOccEnv
emptyTidyOccEnv = emptyOccEnv

initTidyOccEnv :: [OccName] -> TidyOccEnv	-- Initialise with names to avoid!
initTidyOccEnv = foldl (\env occ -> extendOccEnv env occ 1) emptyTidyOccEnv

tidyOccName :: TidyOccEnv -> OccName -> (TidyOccEnv, OccName)

tidyOccName in_scope occ@(OccName occ_sp fs)
  = case lookupOccEnv in_scope occ of
	Nothing -> 	-- Not already used: make it used
		   (extendOccEnv in_scope occ 1, occ)

	Just n  -> 	-- Already used: make a new guess, 
			-- change the guess base, and try again
		   tidyOccName  (extendOccEnv in_scope occ (n+1))
                                (mkOccName occ_sp (base_occ ++ show n))
  where
    base_occ = reverse (dropWhile isDigit (reverse (unpackFS fs)))

mkTupleOcc :: NameSpace -> Boxity -> Arity -> OccName
mkTupleOcc ns bx ar = OccName ns (mkFastString str)
  where
 	-- no need to cache these, the caching is done in the caller
	-- (TysWiredIn.mk_tuple)
    str = case bx of
		Boxed   -> '(' : commas ++ ")"
		Unboxed -> '(' : '#' : commas ++ "#)"

    commas = take (ar-1) (repeat ',')

isTupleOcc_maybe :: OccName -> Maybe (NameSpace, Boxity, Arity)
-- Tuples are special, because there are so many of them!
isTupleOcc_maybe (OccName ns fs)
  = case unpackFS fs of
	'(':'#':',':rest -> Just (ns, Unboxed, 2 + count_commas rest)
	'(':',':rest     -> Just (ns, Boxed,   2 + count_commas rest)
	_other           -> Nothing
  where
    count_commas (',':rest) = 1 + count_commas rest
    count_commas _          = 0

isLexCon,   isLexVar,    isLexId,    isLexSym    :: FastString -> Bool
isLexConId, isLexConSym, isLexVarId, isLexVarSym :: FastString -> Bool

isLexCon cs = isLexConId  cs || isLexConSym cs
isLexVar cs = isLexVarId  cs || isLexVarSym cs

isLexId  cs = isLexConId  cs || isLexVarId  cs
isLexSym cs = isLexConSym cs || isLexVarSym cs

-------------

isLexConId cs				-- Prefix type or data constructors
  | nullFS cs	       = False		-- 	e.g. "Foo", "[]", "(,)" 
  | cs == (fsLit "[]") = True
  | otherwise	       = startsConId (headFS cs)

isLexVarId cs				-- Ordinary prefix identifiers
  | nullFS cs	      = False		-- 	e.g. "x", "_x"
  | otherwise         = startsVarId (headFS cs)

isLexConSym cs				-- Infix type or data constructors
  | nullFS cs	       = False		--	e.g. ":-:", ":", "->"
  | cs == (fsLit "->") = True
  | otherwise	       = startsConSym (headFS cs)

isLexVarSym cs				-- Infix identifiers
  | nullFS cs	      = False		-- 	e.g. "+"
  | otherwise         = startsVarSym (headFS cs)

-------------
startsVarSym, startsVarId, startsConSym, startsConId :: Char -> Bool
startsVarSym c = isSymbolASCII c || (ord c > 0x7f && isSymbol c) -- Infix Ids
startsConSym c = c == ':'				-- Infix data constructors
startsVarId c  = isLower c || c == '_'	-- Ordinary Ids
startsConId c  = isUpper c || c == '('	-- Ordinary type constructors and data constructors

isSymbolASCII :: Char -> Bool
isSymbolASCII c = c `elem` "!#$%&*+./<=>?@\\^|~-"

instance Binary NameSpace where
    put_ bh VarName = do
	    putByte bh 0
    put_ bh DataName = do
	    putByte bh 1
    put_ bh TvName = do
	    putByte bh 2
    put_ bh TcClsName = do
	    putByte bh 3
    get bh = do
	    h <- getByte bh
	    case h of
	      0 -> do return VarName
	      1 -> do return DataName
	      2 -> do return TvName
	      _ -> do return TcClsName

instance Binary OccName where
    put_ bh (OccName aa ab) = do
	    put_ bh aa
	    put_ bh ab
    get bh = do
	  aa <- get bh
	  ab <- get bh
	  return (OccName aa ab)