module RdrHsSyn (
	extractHsTyRdrTyVars, 
	extractHsRhoRdrTyVars, extractGenericPatTyVars,
 
	mkHsOpApp, 
	mkHsIntegral, mkHsFractional, mkHsIsString,
	mkHsDo, mkHsSplice, mkTopSpliceDecl,
        mkClassDecl, mkTyData, mkTyFamily, mkTySynonym,
        splitCon, mkInlinePragma,	
	mkRecConstrOrUpdate, -- HsExp -> [HsFieldUpdate] -> P HsExp

	cvBindGroup,
        cvBindsAndSigs,
	cvTopDecls,
        placeHolderPunRhs,

	-- Stuff to do with Foreign declarations
	mkImport,
        parseCImport,
	mkExport,
	mkExtName,           -- RdrName -> CLabelString
	mkGadtDecl,          -- [Located RdrName] -> LHsType RdrName -> ConDecl RdrName
	mkSimpleConDecl, 
	mkDeprecatedGadtRecordDecl,

	-- Bunch of functions in the parser monad for 
	-- checking and constructing values
	checkPrecP, 	      -- Int -> P Int
	checkContext,	      -- HsType -> P HsContext
	checkPred,	      -- HsType -> P HsPred
	checkTyVars,          -- [LHsType RdrName] -> P ()
	checkKindSigs,	      -- [LTyClDecl RdrName] -> P ()
	checkInstType,	      -- HsType -> P HsType
	checkPattern,	      -- HsExp -> P HsPat
	bang_RDR,
	checkPatterns,	      -- SrcLoc -> [HsExp] -> P [HsPat]
	checkDo,	      -- [Stmt] -> P [Stmt]
	checkMDo,	      -- [Stmt] -> P [Stmt]
	checkValDef,	      -- (SrcLoc, HsExp, HsRhs, [HsDecl]) -> P HsDecl
	checkValSig,	      -- (SrcLoc, HsExp, HsRhs, [HsDecl]) -> P HsDecl
	checkDoAndIfThenElse,
	parseError,	    
	parseErrorSDoc,	    
    ) where

import HsSyn		-- Lots of it
import Class            ( FunDep )
import TypeRep          ( Kind )
import RdrName		( RdrName, isRdrTyVar, isRdrTc, mkUnqual, rdrNameOcc, 
			  isRdrDataCon, isUnqual, getRdrName, setRdrNameSpace )
import BasicTypes	( maxPrecedence, Activation(..), RuleMatchInfo,
                          InlinePragma(..), InlineSpec(..) )
import Lexer
import TysWiredIn	( unitTyCon ) 
import ForeignCall
import OccName  	( srcDataName, varName, isDataOcc, isTcOcc, 
			  occNameString )
import PrelNames	( forall_tv_RDR )
import DynFlags
import SrcLoc
import OrdList		( OrdList, fromOL )
import Bag		( Bag, emptyBag, consBag, foldrBag )
import Outputable
import FastString
import Maybes

import Control.Applicative ((<$>))       
import Control.Monad
import Text.ParserCombinators.ReadP as ReadP
import Data.List        ( nubBy )
import Data.Char

#include "HsVersions.h"

extractHsTyRdrTyVars :: LHsType RdrName -> [Located RdrName]
extractHsTyRdrTyVars ty = nubBy eqLocated (extract_lty ty [])

extractHsTysRdrTyVars :: [LHsType RdrName] -> [Located RdrName]
extractHsTysRdrTyVars ty = nubBy eqLocated (extract_ltys ty [])

extractHsRhoRdrTyVars :: LHsContext RdrName -> LHsType RdrName -> [Located RdrName]
-- This one takes the context and tau-part of a 
-- sigma type and returns their free type variables
extractHsRhoRdrTyVars ctxt ty 
 = nubBy eqLocated $ extract_lctxt ctxt (extract_lty ty [])

extract_lctxt :: Located [LHsPred RdrName] -> [Located RdrName] -> [Located RdrName]
extract_lctxt ctxt acc = foldr (extract_pred . unLoc) acc (unLoc ctxt)

extract_pred :: HsPred RdrName -> [Located RdrName] -> [Located RdrName]
extract_pred (HsClassP _   tys) acc = extract_ltys tys acc
extract_pred (HsEqualP ty1 ty2) acc = extract_lty ty1 (extract_lty ty2 acc)
extract_pred (HsIParam _   ty ) acc = extract_lty ty acc

extract_ltys :: [LHsType RdrName] -> [Located RdrName] -> [Located RdrName]
extract_ltys tys acc = foldr extract_lty acc tys

extract_lty :: LHsType RdrName -> [Located RdrName] -> [Located RdrName]
extract_lty (L loc ty) acc 
  = case ty of
      HsTyVar tv 	        -> extract_tv loc tv acc
      HsBangTy _ ty            	-> extract_lty ty acc
      HsRecTy flds            	-> foldr (extract_lty . cd_fld_type) acc flds
      HsAppTy ty1 ty2          	-> extract_lty ty1 (extract_lty ty2 acc)
      HsListTy ty              	-> extract_lty ty acc
      HsPArrTy ty              	-> extract_lty ty acc
      HsTupleTy _ tys          	-> extract_ltys tys acc
      HsFunTy ty1 ty2          	-> extract_lty ty1 (extract_lty ty2 acc)
      HsPredTy p		-> extract_pred p acc
      HsOpTy ty1 (L loc tv) ty2 -> extract_tv loc tv (extract_lty ty1 (extract_lty ty2 acc))
      HsParTy ty               	-> extract_lty ty acc
      HsNumTy {}                -> acc
      HsCoreTy {}               -> acc  -- The type is closed
      HsQuasiQuoteTy {}	        -> acc  -- Quasi quotes mention no type variables
      HsSpliceTy {}           	-> acc	-- Type splices mention no type variables
      HsKindSig ty _            -> extract_lty ty acc
      HsForAllTy _ [] cx ty     -> extract_lctxt cx (extract_lty ty acc)
      HsForAllTy _ tvs cx ty    -> acc ++ (filter ((`notElem` locals) . unLoc) $
					   extract_lctxt cx (extract_lty ty []))
				where
				   locals = hsLTyVarNames tvs
      HsDocTy ty _              -> extract_lty ty acc

extract_tv :: SrcSpan -> RdrName -> [Located RdrName] -> [Located RdrName]
extract_tv loc tv acc | isRdrTyVar tv = L loc tv : acc
		      | otherwise     = acc

extractGenericPatTyVars :: LHsBinds RdrName -> [Located RdrName]
-- Get the type variables out of the type patterns in a bunch of
-- possibly-generic bindings in a class declaration
extractGenericPatTyVars binds
  = nubBy eqLocated (foldrBag get [] binds)
  where
    get (L _ (FunBind { fun_matches = MatchGroup ms _ })) acc = foldr (get_m.unLoc) acc ms
    get _                                                 acc = acc

    get_m (Match (L _ (TypePat ty) : _) _ _) acc = extract_lty ty acc
    get_m _                                        acc = acc

mkClassDecl :: SrcSpan
            -> Located (Maybe (LHsContext RdrName), LHsType RdrName)
            -> Located [Located (FunDep RdrName)]
            -> Located (OrdList (LHsDecl RdrName))
	    -> P (LTyClDecl RdrName)

mkClassDecl loc (L _ (mcxt, tycl_hdr)) fds where_cls
  = do { let (binds, sigs, ats, docs) = cvBindsAndSigs (unLoc where_cls)
       ; let cxt = fromMaybe (noLoc []) mcxt
       ; (cls, tparams) <- checkTyClHdr tycl_hdr
       ; tyvars <- checkTyVars tparams      -- Only type vars allowed
       ; checkKindSigs ats
       ; return (L loc (ClassDecl { tcdCtxt = cxt, tcdLName = cls, tcdTyVars = tyvars,
		             	    tcdFDs = unLoc fds, tcdSigs = sigs, tcdMeths = binds,
			     	    tcdATs   = ats, tcdDocs  = docs })) }

mkTyData :: SrcSpan
         -> NewOrData
	 -> Bool		-- True <=> data family instance
         -> Located (Maybe (LHsContext RdrName), LHsType RdrName)
         -> Maybe Kind
         -> [LConDecl RdrName]
         -> Maybe [LHsType RdrName]
         -> P (LTyClDecl RdrName)
mkTyData loc new_or_data is_family (L _ (mcxt, tycl_hdr)) ksig data_cons maybe_deriv
  = do { (tc, tparams) <- checkTyClHdr tycl_hdr

       ; checkDatatypeContext mcxt
       ; let cxt = fromMaybe (noLoc []) mcxt
       ; (tyvars, typats) <- checkTParams is_family tparams
       ; return (L loc (TyData { tcdND = new_or_data, tcdCtxt = cxt, tcdLName = tc,
	                  	 tcdTyVars = tyvars, tcdTyPats = typats, 
                                 tcdCons = data_cons, 
	                  	 tcdKindSig = ksig, tcdDerivs = maybe_deriv })) }

mkTySynonym :: SrcSpan 
            -> Bool	        -- True <=> type family instances
            -> LHsType RdrName  -- LHS
            -> LHsType RdrName	-- RHS
            -> P (LTyClDecl RdrName)
mkTySynonym loc is_family lhs rhs
  = do { (tc, tparams) <- checkTyClHdr lhs
       ; (tyvars, typats) <- checkTParams is_family tparams
       ; return (L loc (TySynonym tc tyvars typats rhs)) }

mkTyFamily :: SrcSpan
           -> FamilyFlavour
	   -> LHsType RdrName   -- LHS
	   -> Maybe Kind        -- Optional kind signature
           -> P (LTyClDecl RdrName)
mkTyFamily loc flavour lhs ksig
  = do { (tc, tparams) <- checkTyClHdr lhs
       ; tyvars <- checkTyVars tparams
       ; return (L loc (TyFamily flavour tc tyvars ksig)) }

mkTopSpliceDecl :: LHsExpr RdrName -> HsDecl RdrName
-- If the user wrote
--      [pads| ... ]   then return a QuasiQuoteD
--	$(e)           then return a SpliceD
-- but if she wrote, say,
--      f x            then behave as if she'd written $(f x)
--		       ie a SpliceD
mkTopSpliceDecl (L _ (HsQuasiQuoteE qq))            = QuasiQuoteD qq
mkTopSpliceDecl (L _ (HsSpliceE (HsSplice _ expr))) = SpliceD (SpliceDecl expr       Explicit)
mkTopSpliceDecl other_expr                          = SpliceD (SpliceDecl other_expr Implicit)

--  | Groups together bindings for a single function
cvTopDecls :: OrdList (LHsDecl RdrName) -> [LHsDecl RdrName]
cvTopDecls decls = go (fromOL decls)
  where
    go :: [LHsDecl RdrName] -> [LHsDecl RdrName]
    go [] 		    = []
    go (L l (ValD b) : ds)  = L l' (ValD b') : go ds'
			    where (L l' b', ds') = getMonoBind (L l b) ds
    go (d : ds)   	    = d : go ds

-- Declaration list may only contain value bindings and signatures.
cvBindGroup :: OrdList (LHsDecl RdrName) -> HsValBinds RdrName
cvBindGroup binding
  = case cvBindsAndSigs binding of
      (mbs, sigs, tydecls, _) -> ASSERT( null tydecls )
      	    	  	         ValBindsIn mbs sigs

cvBindsAndSigs :: OrdList (LHsDecl RdrName)
  -> (Bag (LHsBind RdrName), [LSig RdrName], [LTyClDecl RdrName], [LDocDecl])
-- Input decls contain just value bindings and signatures
-- and in case of class or instance declarations also
-- associated type declarations. They might also contain Haddock comments.
cvBindsAndSigs  fb = go (fromOL fb)
  where
    go [] 		   = (emptyBag, [], [], [])
    go (L l (SigD s) : ds) = (bs, L l s : ss, ts, docs)
			   where (bs, ss, ts, docs) = go ds
    go (L l (ValD b) : ds) = (b' `consBag` bs, ss, ts, docs)
			   where (b', ds')    = getMonoBind (L l b) ds
				 (bs, ss, ts, docs) = go ds'
    go (L l (TyClD t): ds) = (bs, ss, L l t : ts, docs)
			   where (bs, ss, ts, docs) = go ds
    go (L l (DocD d) : ds) =  (bs, ss, ts, (L l d) : docs)
			   where (bs, ss, ts, docs) = go ds
    go (L _ d : _)        = pprPanic "cvBindsAndSigs" (ppr d)

-----------------------------------------------------------------------------
-- Group function bindings into equation groups

getMonoBind :: LHsBind RdrName -> [LHsDecl RdrName]
  -> (LHsBind RdrName, [LHsDecl RdrName])
-- Suppose 	(b',ds') = getMonoBind b ds
-- 	ds is a list of parsed bindings
--	b is a MonoBinds that has just been read off the front

-- Then b' is the result of grouping more equations from ds that
-- belong with b into a single MonoBinds, and ds' is the depleted
-- list of parsed bindings.
--
-- All Haddock comments between equations inside the group are 
-- discarded.
--
-- No AndMonoBinds or EmptyMonoBinds here; just single equations

getMonoBind (L loc1 (FunBind { fun_id = fun_id1@(L _ f1), fun_infix = is_infix1,
                               fun_matches = MatchGroup mtchs1 _ })) binds
  | has_args mtchs1
  = go is_infix1 mtchs1 loc1 binds []
  where
    go is_infix mtchs loc 
       (L loc2 (ValD (FunBind { fun_id = L _ f2, fun_infix = is_infix2,
			        fun_matches = MatchGroup mtchs2 _ })) : binds) _
	| f1 == f2 = go (is_infix || is_infix2) (mtchs2 ++ mtchs) 
		        (combineSrcSpans loc loc2) binds []
    go is_infix mtchs loc (doc_decl@(L loc2 (DocD _)) : binds) doc_decls 
	= let doc_decls' = doc_decl : doc_decls  
          in go is_infix mtchs (combineSrcSpans loc loc2) binds doc_decls'
    go is_infix mtchs loc binds doc_decls
	= (L loc (makeFunBind fun_id1 is_infix (reverse mtchs)), (reverse doc_decls) ++ binds)
	-- Reverse the final matches, to get it back in the right order
        -- Do the same thing with the trailing doc comments

getMonoBind bind binds = (bind, binds)

has_args :: [LMatch RdrName] -> Bool
has_args [] 	    	     	      = panic "RdrHsSyn:has_args"
has_args ((L _ (Match args _ _)) : _) = not (null args)
	-- Don't group together FunBinds if they have
	-- no arguments.  This is necessary now that variable bindings
	-- with no arguments are now treated as FunBinds rather
	-- than pattern bindings (tests/rename/should_fail/rnfail002).

-----------------------------------------------------------------------------
-- splitCon

-- When parsing data declarations, we sometimes inadvertently parse
-- a constructor application as a type (eg. in data T a b = C a b `D` E a b)
-- This function splits up the type application, adds any pending
-- arguments, and converts the type constructor back into a data constructor.

splitCon :: LHsType RdrName
      -> P (Located RdrName, HsConDeclDetails RdrName)
-- This gets given a "type" that should look like
--      C Int Bool
-- or   C { x::Int, y::Bool }
-- and returns the pieces
splitCon ty
 = split ty []
 where
   split (L _ (HsAppTy t u)) ts = split t (u : ts)
   split (L l (HsTyVar tc))  ts = do data_con <- tyConToDataCon l tc
 				     return (data_con, mk_rest ts)
   split (L l _) _ 	        = parseErrorSDoc l (text "parse error in constructor in data/newtype declaration:" <+> ppr ty)

   mk_rest [L _ (HsRecTy flds)] = RecCon flds
   mk_rest ts                   = PrefixCon ts

mkDeprecatedGadtRecordDecl :: SrcSpan 
		     	   -> Located RdrName
		     	   -> [ConDeclField RdrName]
			   -> LHsType RdrName
		     	   ->  P (LConDecl  RdrName)
-- This one uses the deprecated syntax
--    C { x,y ::Int } :: T a b
-- We give it a RecCon details right away
mkDeprecatedGadtRecordDecl loc (L con_loc con) flds res_ty
  = do { data_con <- tyConToDataCon con_loc con
       ; return (L loc (ConDecl { con_old_rec  = True
                                , con_name     = data_con
	    	 		, con_explicit = Implicit
	    	 		, con_qvars    = []
	    	 		, con_cxt      = noLoc []
	    	 		, con_details  = RecCon flds
	    	 		, con_res      = ResTyGADT res_ty
            	 		, con_doc      = Nothing })) }

mkSimpleConDecl :: Located RdrName -> [LHsTyVarBndr RdrName]
		-> LHsContext RdrName -> HsConDeclDetails RdrName
		-> ConDecl RdrName

mkSimpleConDecl name qvars cxt details
  = ConDecl { con_old_rec  = False
            , con_name     = name
	    , con_explicit = Explicit
	    , con_qvars    = qvars
	    , con_cxt      = cxt
	    , con_details  = details
	    , con_res      = ResTyH98
            , con_doc      = Nothing }

mkGadtDecl :: [Located RdrName]
           -> LHsType RdrName     -- Always a HsForAllTy
           -> [ConDecl RdrName]
-- We allow C,D :: ty
-- and expand it as if it had been 
--    C :: ty; D :: ty
-- (Just like type signatures in general.)
mkGadtDecl names (L _ (HsForAllTy imp qvars cxt tau))
  = [mk_gadt_con name | name <- names]
  where
    (details, res_ty)		-- See Note [Sorting out the result type]
      = case tau of
    	  L _ (HsFunTy (L _ (HsRecTy flds)) res_ty) -> (RecCon flds,  res_ty)
	  _other                                    -> (PrefixCon [], tau)

    mk_gadt_con name
       = ConDecl { con_old_rec  = False
                 , con_name     = name
	    	 , con_explicit = imp
	    	 , con_qvars    = qvars
	    	 , con_cxt      = cxt
	    	 , con_details  = details
	    	 , con_res      = ResTyGADT res_ty
            	 , con_doc      = Nothing }
mkGadtDecl _ other_ty = pprPanic "mkGadtDecl" (ppr other_ty)

tyConToDataCon :: SrcSpan -> RdrName -> P (Located RdrName)
tyConToDataCon loc tc
  | isTcOcc (rdrNameOcc tc)
  = return (L loc (setRdrNameSpace tc srcDataName))
  | otherwise
  = parseErrorSDoc loc (msg $$ extra)
  where
    msg = text "Not a data constructor:" <+> quotes (ppr tc)
    extra | tc == forall_tv_RDR
	  = text "Perhaps you intended to use -XExistentialQuantification"
	  | otherwise = empty

----------------------------------------------------------------------------
-- Various Syntactic Checks

checkInstType :: LHsType RdrName -> P (LHsType RdrName)
checkInstType (L l t)
  = case t of
	HsForAllTy exp tvs ctxt ty -> do
		dict_ty <- checkDictTy ty
	      	return (L l (HsForAllTy exp tvs ctxt dict_ty))

        HsParTy ty -> checkInstType ty

	ty ->   do dict_ty <- checkDictTy (L l ty)
	      	   return (L l (HsForAllTy Implicit [] (noLoc []) dict_ty))

checkDictTy :: LHsType RdrName -> P (LHsType RdrName)
checkDictTy (L spn ty) = check ty []
  where
  check (HsTyVar tc)            args | isRdrTc tc = done tc args
  check (HsOpTy t1 (L _ tc) t2) args | isRdrTc tc = done tc (t1:t2:args)
  check (HsAppTy l r) args = check (unLoc l) (r:args)
  check (HsParTy t)   args = check (unLoc t) args
  check _ _ = parseErrorSDoc spn (text "Malformed instance header:" <+> ppr ty)

  done tc args = return (L spn (HsPredTy (HsClassP tc args)))

checkTParams :: Bool	  -- Type/data family
	     -> [LHsType RdrName]
	     -> P ([LHsTyVarBndr RdrName], Maybe [LHsType RdrName])
-- checkTParams checks the type parameters of a data/newtype declaration
-- There are two cases:
--
--  a) Vanilla data/newtype decl. In that case 
--        - the type parameters should all be type variables
--        - they may have a kind annotation
--
--  b) Family data/newtype decl.  In that case
--        - The type parameters may be arbitrary types
--        - We find the type-varaible binders by find the 
--          free type vars of those types
--        - We make them all kind-sig-free binders (UserTyVar)
--          If there are kind sigs in the type parameters, they
--          will fix the binder's kind when we kind-check the 
--          type parameters
checkTParams is_family tparams
  | not is_family        -- Vanilla case (a)
  = do { tyvars <- checkTyVars tparams
       ; return (tyvars, Nothing) }
  | otherwise		 -- Family case (b)
  = do { let tyvars = userHsTyVarBndrs (extractHsTysRdrTyVars tparams)
       ; return (tyvars, Just tparams) }

checkTyVars :: [LHsType RdrName] -> P [LHsTyVarBndr RdrName]
-- Check whether the given list of type parameters are all type variables
-- (possibly with a kind signature).  If the second argument is `False',
-- only type variables are allowed and we raise an error on encountering a
-- non-variable; otherwise, we allow non-variable arguments and return the
-- entire list of parameters.
checkTyVars tparms = mapM chk tparms
  where
	-- Check that the name space is correct!
    chk (L l (HsKindSig (L _ (HsTyVar tv)) k))
	| isRdrTyVar tv    = return (L l (KindedTyVar tv k))
    chk (L l (HsTyVar tv))
        | isRdrTyVar tv    = return (L l (UserTyVar tv placeHolderKind))
    chk t@(L l _)            =
	  parseErrorSDoc l (text "Type found:" <+> ppr t
                     $$ text "where type variable expected, in:" <+>
                        sep (map (pprParendHsType . unLoc) tparms))

checkDatatypeContext :: Maybe (LHsContext RdrName) -> P ()
checkDatatypeContext Nothing = return ()
checkDatatypeContext (Just (L loc c))
    = do allowed <- extension datatypeContextsEnabled
         unless allowed $
             parseErrorSDoc loc
                 (text "Illegal datatype context (use -XDatatypeContexts):" <+>
                  pprHsContext c)

checkTyClHdr :: LHsType RdrName
             -> P (Located RdrName,	     -- the head symbol (type or class name)
	           [LHsType RdrName])        -- parameters of head symbol
-- Well-formedness check and decomposition of type and class heads.
-- Decomposes   T ty1 .. tyn   into    (T, [ty1, ..., tyn])
-- 		Int :*: Bool   into    (:*:, [Int, Bool])
-- returning the pieces
checkTyClHdr ty
  = goL ty []
  where
    goL (L l ty) acc = go l ty acc

    go l (HsTyVar tc) acc 
	| isRdrTc tc 	     = return (L l tc, acc)
				     
    go _ (HsOpTy t1 ltc@(L _ tc) t2) acc
	| isRdrTc tc	     = return (ltc, t1:t2:acc)
    go _ (HsParTy ty)    acc = goL ty acc
    go _ (HsAppTy t1 t2) acc = goL t1 (t2:acc)
    go l _               _   = parseErrorSDoc l (text "Malformed head of type or class declaration:" <+> ppr ty)

-- Check that associated type declarations of a class are all kind signatures.
--
checkKindSigs :: [LTyClDecl RdrName] -> P ()
checkKindSigs = mapM_ check
  where
    check (L l tydecl) 
      | isFamilyDecl tydecl
        || isSynDecl tydecl  = return ()
      | otherwise	     = 
	parseErrorSDoc l (text "Type declaration in a class must be a kind signature or synonym default:" $$ ppr tydecl)

checkContext :: LHsType RdrName -> P (LHsContext RdrName)
checkContext (L l t)
  = check t
 where
  check (HsTupleTy _ ts) 	-- (Eq a, Ord b) shows up as a tuple type
    = do ctx <- mapM checkPred ts
	 return (L l ctx)

  check (HsParTy ty)	-- to be sure HsParTy doesn't get into the way
    = check (unLoc ty)

  check (HsTyVar t)	-- Empty context shows up as a unit type ()
    | t == getRdrName unitTyCon = return (L l [])

  check t 
    = do p <- checkPred (L l t)
         return (L l [p])


checkPred :: LHsType RdrName -> P (LHsPred RdrName)
-- Watch out.. in ...deriving( Show )... we use checkPred on 
-- the list of partially applied predicates in the deriving,
-- so there can be zero args.
checkPred (L spn (HsPredTy (HsIParam n ty)))
  = return (L spn (HsIParam n ty))
checkPred (L spn ty)
  = check spn ty []
  where
    checkl (L l ty) args = check l ty args

    check _loc (HsPredTy pred@(HsEqualP _ _)) 
                                       args | null args
					    = return $ L spn pred
    check _loc (HsTyVar t)             args | not (isRdrTyVar t) 
		 		  	    = return (L spn (HsClassP t args))
    check _loc (HsAppTy l r)           args = checkl l (r:args)
    check _loc (HsOpTy l (L loc tc) r) args = check loc (HsTyVar tc) (l:r:args)
    check _loc (HsParTy t)  	       args = checkl t args
    check loc _                        _    = parseErrorSDoc loc
                                (text "malformed class assertion:" <+> ppr ty)

---------------------------------------------------------------------------
-- Checking statements in a do-expression
-- 	We parse   do { e1 ; e2 ; }
-- 	as [ExprStmt e1, ExprStmt e2]
-- checkDo (a) checks that the last thing is an ExprStmt
--	   (b) returns it separately
-- same comments apply for mdo as well

checkDo, checkMDo :: SrcSpan -> [LStmt RdrName] -> P ([LStmt RdrName], LHsExpr RdrName)

checkDo	 = checkDoMDo "a " "'do'"
checkMDo = checkDoMDo "an " "'mdo'"

checkDoMDo :: String -> String -> SrcSpan -> [LStmt RdrName] -> P ([LStmt RdrName], LHsExpr RdrName)
checkDoMDo _   nm loc []   = parseErrorSDoc loc (text ("Empty " ++ nm ++ " construct"))
checkDoMDo pre nm _   ss   = do
  check ss
  where 
	check  []                     = panic "RdrHsSyn:checkDoMDo"
	check  [L _ (ExprStmt e _ _)] = return ([], e)
	check  [L l e] = parseErrorSDoc l
                         (text ("The last statement in " ++ pre ++ nm ++
					            " construct must be an expression:")
                       $$ ppr e)
	check (s:ss) = do
	  (ss',e') <-  check ss
	  return ((s:ss'),e')

-- -------------------------------------------------------------------------
-- Checking Patterns.

-- We parse patterns as expressions and check for valid patterns below,
-- converting the expression into a pattern at the same time.

checkPattern :: LHsExpr RdrName -> P (LPat RdrName)
checkPattern e = checkLPat e

checkPatterns :: [LHsExpr RdrName] -> P [LPat RdrName]
checkPatterns es = mapM checkPattern es

checkLPat :: LHsExpr RdrName -> P (LPat RdrName)
checkLPat e@(L l _) = checkPat l e []

checkPat :: SrcSpan -> LHsExpr RdrName -> [LPat RdrName] -> P (LPat RdrName)
checkPat loc (L l (HsVar c)) args
  | isRdrDataCon c = return (L loc (ConPatIn (L l c) (PrefixCon args)))
checkPat loc e args 	-- OK to let this happen even if bang-patterns
			-- are not enabled, because there is no valid
			-- non-bang-pattern parse of (C ! e)
  | Just (e', args') <- splitBang e
  = do	{ args'' <- checkPatterns args'
	; checkPat loc e' (args'' ++ args) }
checkPat loc (L _ (HsApp f x)) args
  = do { x <- checkLPat x; checkPat loc f (x:args) }
checkPat loc (L _ e) []
  = do { pState <- getPState
       ; p <- checkAPat (dflags pState) loc e
       ; return (L loc p) }
checkPat loc e _
  = patFail loc (unLoc e)

checkAPat :: DynFlags -> SrcSpan -> HsExpr RdrName -> P (Pat RdrName)
checkAPat dynflags loc e0 = case e0 of
   EWildPat -> return (WildPat placeHolderType)
   HsVar x  -> return (VarPat x)
   HsLit l  -> return (LitPat l)

   -- Overloaded numeric patterns (e.g. f 0 x = x)
   -- Negation is recorded separately, so that the literal is zero or +ve
   -- NB. Negative *primitive* literals are already handled by the lexer
   HsOverLit pos_lit          -> return (mkNPat pos_lit Nothing)
   NegApp (L _ (HsOverLit pos_lit)) _ 
			-> return (mkNPat pos_lit (Just noSyntaxExpr))
   
   SectionR (L _ (HsVar bang)) e 	-- (! x)
 	| bang == bang_RDR 
	-> do { bang_on <- extension bangPatEnabled
	      ; if bang_on then checkLPat e >>= (return . BangPat)
		else parseErrorSDoc loc (text "Illegal bang-pattern (use -XBangPatterns):" $$ ppr e0) }

   ELazyPat e	      -> checkLPat e >>= (return . LazyPat)
   EAsPat n e	      -> checkLPat e >>= (return . AsPat n)
   -- view pattern is well-formed if the pattern is
   EViewPat expr patE -> checkLPat patE >>= (return . (\p -> ViewPat expr p placeHolderType))
   ExprWithTySig e t  -> do e <- checkLPat e
                            -- Pattern signatures are parsed as sigtypes,
                            -- but they aren't explicit forall points.  Hence
                            -- we have to remove the implicit forall here.
                            let t' = case t of 
                                       L _ (HsForAllTy Implicit _ (L _ []) ty) -> ty
                                       other -> other
                            return (SigPatIn e t')
   
   -- n+k patterns
   OpApp (L nloc (HsVar n)) (L _ (HsVar plus)) _ 
	 (L _ (HsOverLit lit@(OverLit {ol_val = HsIntegral {}})))
   		      | xopt Opt_NPlusKPatterns dynflags && (plus == plus_RDR)
   		      -> return (mkNPlusKPat (L nloc n) lit)
   
   OpApp l op _fix r  -> do l <- checkLPat l
                            r <- checkLPat r
                            case op of
                               L cl (HsVar c) | isDataOcc (rdrNameOcc c)
                                      -> return (ConPatIn (L cl c) (InfixCon l r))
                               _ -> patFail loc e0
   
   HsPar e	      -> checkLPat e >>= (return . ParPat)
   ExplicitList _ es  -> do ps <- mapM checkLPat es
                            return (ListPat ps placeHolderType)
   ExplicitPArr _ es  -> do ps <- mapM checkLPat es
                            return (PArrPat ps placeHolderType)
   
   ExplicitTuple es b 
     | all tupArgPresent es  -> do ps <- mapM checkLPat [e | Present e <- es]
                                   return (TuplePat ps b placeHolderType)
     | otherwise -> parseErrorSDoc loc (text "Illegal tuple section in pattern:" $$ ppr e0)
   
   RecordCon c _ (HsRecFields fs dd)
                      -> do fs <- mapM checkPatField fs
                            return (ConPatIn c (RecCon (HsRecFields fs dd)))
   HsQuasiQuoteE q    -> return (QuasiQuotePat q)
-- Generics 
   HsType ty          -> return (TypePat ty) 
   _                  -> patFail loc e0

placeHolderPunRhs :: LHsExpr RdrName
-- The RHS of a punned record field will be filled in by the renamer
-- It's better not to make it an error, in case we want to print it when debugging
placeHolderPunRhs = noLoc (HsVar pun_RDR)

plus_RDR, bang_RDR, pun_RDR :: RdrName
plus_RDR = mkUnqual varName (fsLit "+")	-- Hack
bang_RDR = mkUnqual varName (fsLit "!")	-- Hack
pun_RDR  = mkUnqual varName (fsLit "pun-right-hand-side")

checkPatField :: HsRecField RdrName (LHsExpr RdrName) -> P (HsRecField RdrName (LPat RdrName))
checkPatField fld = do	{ p <- checkLPat (hsRecFieldArg fld)
			; return (fld { hsRecFieldArg = p }) }

patFail :: SrcSpan -> HsExpr RdrName -> P a
patFail loc e = parseErrorSDoc loc (text "Parse error in pattern:" <+> ppr e)


---------------------------------------------------------------------------
-- Check Equation Syntax

checkValDef :: LHsExpr RdrName
	    -> Maybe (LHsType RdrName)
	    -> Located (GRHSs RdrName)
	    -> P (HsBind RdrName)

checkValDef lhs (Just sig) grhss
   	-- x :: ty = rhs  parses as a *pattern* binding
  = checkPatBind (L (combineLocs lhs sig) (ExprWithTySig lhs sig)) grhss

checkValDef lhs opt_sig grhss
  = do	{ mb_fun <- isFunLhs lhs
	; case mb_fun of
	    Just (fun, is_infix, pats) -> checkFunBind (getLoc lhs)
						fun is_infix pats opt_sig grhss
	    Nothing -> checkPatBind lhs grhss }

checkFunBind :: SrcSpan
             -> Located RdrName
             -> Bool
             -> [LHsExpr RdrName]
             -> Maybe (LHsType RdrName)
             -> Located (GRHSs RdrName)
             -> P (HsBind RdrName)
checkFunBind lhs_loc fun is_infix pats opt_sig (L rhs_span grhss)
  = do	ps <- checkPatterns pats
	let match_span = combineSrcSpans lhs_loc rhs_span
	return (makeFunBind fun is_infix [L match_span (Match ps opt_sig grhss)])
	-- The span of the match covers the entire equation.  
	-- That isn't quite right, but it'll do for now.

makeFunBind :: Located id -> Bool -> [LMatch id] -> HsBind id
-- Like HsUtils.mkFunBind, but we need to be able to set the fixity too
makeFunBind fn is_infix ms 
  = FunBind { fun_id = fn, fun_infix = is_infix, fun_matches = mkMatchGroup ms,
	      fun_co_fn = idHsWrapper, bind_fvs = placeHolderNames, fun_tick = Nothing }

checkPatBind :: LHsExpr RdrName
             -> Located (GRHSs RdrName)
             -> P (HsBind RdrName)
checkPatBind lhs (L _ grhss)
  = do	{ lhs <- checkPattern lhs
	; return (PatBind lhs grhss placeHolderType placeHolderNames) }

checkValSig
	:: LHsExpr RdrName
	-> LHsType RdrName
	-> P (Sig RdrName)
checkValSig (L l (HsVar v)) ty 
  | isUnqual v && not (isDataOcc (rdrNameOcc v))
  = return (TypeSig (L l v) ty)
checkValSig lhs@(L l _) ty
  = parseErrorSDoc l ((text "Invalid type signature:" <+>
                       ppr lhs <+> text "::" <+> ppr ty)
                   $$ text hint)
  where
    hint = if looks_like_foreign lhs
           then "Perhaps you meant to use -XForeignFunctionInterface?"
           else "Should be of form <variable> :: <type>"
    -- A common error is to forget the ForeignFunctionInterface flag
    -- so check for that, and suggest.  cf Trac #3805
    -- Sadly 'foreign import' still barfs 'parse error' because 'import' is a keyword
    looks_like_foreign (L _ (HsVar v))     = v == foreign_RDR
    looks_like_foreign (L _ (HsApp lhs _)) = looks_like_foreign lhs
    looks_like_foreign _                   = False

    foreign_RDR = mkUnqual varName (fsLit "foreign")

checkDoAndIfThenElse :: LHsExpr RdrName
                     -> Bool
                     -> LHsExpr RdrName
                     -> Bool
                     -> LHsExpr RdrName
                     -> P ()
checkDoAndIfThenElse guardExpr semiThen thenExpr semiElse elseExpr
 | semiThen || semiElse
    = do pState <- getPState
         unless (xopt Opt_DoAndIfThenElse (dflags pState)) $ do
             parseErrorSDoc (combineLocs guardExpr elseExpr)
                            (text "Unexpected semi-colons in conditional:"
                          $$ nest 4 expr
                          $$ text "Perhaps you meant to use -XDoAndIfThenElse?")
 | otherwise            = return ()
    where pprOptSemi True  = semi
          pprOptSemi False = empty
          expr = text "if"   <+> ppr guardExpr <> pprOptSemi semiThen <+>
                 text "then" <+> ppr thenExpr  <> pprOptSemi semiElse <+>
                 text "else" <+> ppr elseExpr

	-- The parser left-associates, so there should 
	-- not be any OpApps inside the e's
splitBang :: LHsExpr RdrName -> Maybe (LHsExpr RdrName, [LHsExpr RdrName])
-- Splits (f ! g a b) into (f, [(! g), a, b])
splitBang (L loc (OpApp l_arg bang@(L _ (HsVar op)) _ r_arg))
  | op == bang_RDR = Just (l_arg, L loc (SectionR bang arg1) : argns)
  where
    (arg1,argns) = split_bang r_arg []
    split_bang (L _ (HsApp f e)) es = split_bang f (e:es)
    split_bang e	   	 es = (e,es)
splitBang _ = Nothing

isFunLhs :: LHsExpr RdrName 
	 -> P (Maybe (Located RdrName, Bool, [LHsExpr RdrName]))
-- A variable binding is parsed as a FunBind.
-- Just (fun, is_infix, arg_pats) if e is a function LHS
--
-- The whole LHS is parsed as a single expression.  
-- Any infix operators on the LHS will parse left-associatively
-- E.g. 	f !x y !z
-- 	will parse (rather strangely) as 
--		(f ! x y) ! z
-- 	It's up to isFunLhs to sort out the mess
--
-- a .!. !b 

isFunLhs e = go e []
 where
   go (L loc (HsVar f)) es 
	| not (isRdrDataCon f)	 = return (Just (L loc f, False, es))
   go (L _ (HsApp f e)) es 	 = go f (e:es)
   go (L _ (HsPar e))   es@(_:_) = go e es

	-- For infix function defns, there should be only one infix *function*
	-- (though there may be infix *datacons* involved too).  So we don't
	-- need fixity info to figure out which function is being defined.
	--	a `K1` b `op` c `K2` d
	-- must parse as
	--	(a `K1` b) `op` (c `K2` d)
	-- The renamer checks later that the precedences would yield such a parse.
	-- 
	-- There is a complication to deal with bang patterns.
	--
	-- ToDo: what about this?
	--		x + 1 `op` y = ...

   go e@(L loc (OpApp l (L loc' (HsVar op)) fix r)) es
	| Just (e',es') <- splitBang e
	= do { bang_on <- extension bangPatEnabled
	     ; if bang_on then go e' (es' ++ es)
	       else return (Just (L loc' op, True, (l:r:es))) }
		-- No bangs; behave just like the next case
	| not (isRdrDataCon op) 	-- We have found the function!
	= return (Just (L loc' op, True, (l:r:es)))
	| otherwise			-- Infix data con; keep going
	= do { mb_l <- go l es
	     ; case mb_l of
		 Just (op', True, j : k : es')
		    -> return (Just (op', True, j : op_app : es'))
		    where
		      op_app = L loc (OpApp k (L loc' (HsVar op)) fix r)
		 _ -> return Nothing }
   go _ _ = return Nothing

---------------------------------------------------------------------------
-- Miscellaneous utilities

checkPrecP :: Located Int -> P Int
checkPrecP (L l i)
 | 0 <= i && i <= maxPrecedence = return i
 | otherwise
    = parseErrorSDoc l (text ("Precedence out of range: " ++ show i))

mkRecConstrOrUpdate 
	:: LHsExpr RdrName 
	-> SrcSpan
	-> ([HsRecField RdrName (LHsExpr RdrName)], Bool)
	-> P (HsExpr RdrName)

mkRecConstrOrUpdate (L l (HsVar c)) _ (fs,dd) | isRdrDataCon c
  = return (RecordCon (L l c) noPostTcExpr (mk_rec_fields fs dd))
mkRecConstrOrUpdate exp loc (fs,dd)
  | null fs   = parseErrorSDoc loc (text "Empty record update of:" <+> ppr exp)
  | otherwise = return (RecordUpd exp (mk_rec_fields fs dd) [] [] [])

mk_rec_fields :: [HsRecField id arg] -> Bool -> HsRecFields id arg
mk_rec_fields fs False = HsRecFields { rec_flds = fs, rec_dotdot = Nothing }
mk_rec_fields fs True  = HsRecFields { rec_flds = fs, rec_dotdot = Just (length fs) }

mkInlinePragma :: (InlineSpec, RuleMatchInfo) -> Maybe Activation -> InlinePragma
-- The Maybe is because the user can omit the activation spec (and usually does)
mkInlinePragma (inl, match_info) mb_act
  = InlinePragma { inl_inline = inl
                 , inl_sat    = Nothing
                 , inl_act    = act
                 , inl_rule   = match_info }
  where
    act = case mb_act of
            Just act -> act
            Nothing  -> -- No phase specified
                        case inl of
                          NoInline -> NeverActive
                          _other   -> AlwaysActive

-----------------------------------------------------------------------------
-- utilities for foreign declarations

-- construct a foreign import declaration
--
mkImport :: CCallConv
	 -> Safety 
	 -> (Located FastString, Located RdrName, LHsType RdrName) 
	 -> P (HsDecl RdrName)
mkImport cconv safety (L loc entity, v, ty)
  | cconv == PrimCallConv                      = do
  let funcTarget = CFunction (StaticTarget entity Nothing)
      importSpec = CImport PrimCallConv safety nilFS funcTarget
  return (ForD (ForeignImport v ty importSpec))

  | otherwise = do
    case parseCImport cconv safety (mkExtName (unLoc v)) (unpackFS entity) of
      Nothing         -> parseErrorSDoc loc (text "Malformed entity string")
      Just importSpec -> return (ForD (ForeignImport v ty importSpec))

-- the string "foo" is ambigous: either a header or a C identifier.  The
-- C identifier case comes first in the alternatives below, so we pick
-- that one.
parseCImport :: CCallConv -> Safety -> FastString -> String
             -> Maybe ForeignImport
parseCImport cconv safety nm str =
 listToMaybe $ map fst $ filter (null.snd) $ 
     readP_to_S parse str
 where
   parse = do
       skipSpaces
       r <- choice [
          string "dynamic" >> return (mk nilFS (CFunction DynamicTarget)),
          string "wrapper" >> return (mk nilFS CWrapper),
          optional (string "static" >> skipSpaces) >> 
           (mk nilFS <$> cimp nm) +++
           (do h <- munch1 hdr_char; skipSpaces; mk (mkFastString h) <$> cimp nm)
         ]
       skipSpaces
       return r

   mk = CImport cconv safety

   hdr_char c = not (isSpace c) -- header files are filenames, which can contain
                                -- pretty much any char (depending on the platform),
                                -- so just accept any non-space character
   id_char  c = isAlphaNum c || c == '_'

   cimp nm = (ReadP.char '&' >> skipSpaces >> CLabel <$> cid)
             +++ ((\c -> CFunction (StaticTarget c Nothing)) <$> cid)
          where 
            cid = return nm +++
                  (do c  <- satisfy (\c -> isAlpha c || c == '_')
                      cs <-  many (satisfy id_char)
                      return (mkFastString (c:cs)))


-- construct a foreign export declaration
--
mkExport :: CCallConv
         -> (Located FastString, Located RdrName, LHsType RdrName) 
	 -> P (HsDecl RdrName)
mkExport cconv (L _ entity, v, ty) = return $
  ForD (ForeignExport v ty (CExport (CExportStatic entity' cconv)))
  where
    entity' | nullFS entity = mkExtName (unLoc v)
	    | otherwise     = entity

-- Supplying the ext_name in a foreign decl is optional; if it
-- isn't there, the Haskell name is assumed. Note that no transformation
-- of the Haskell name is then performed, so if you foreign export (++),
-- it's external name will be "++". Too bad; it's important because we don't
-- want z-encoding (e.g. names with z's in them shouldn't be doubled)
--
mkExtName :: RdrName -> CLabelString
mkExtName rdrNm = mkFastString (occNameString (rdrNameOcc rdrNm))

parseError :: SrcSpan -> String -> P a
parseError span s = parseErrorSDoc span (text s)

parseErrorSDoc :: SrcSpan -> SDoc -> P a
parseErrorSDoc span s = failSpanMsgP span s