%
% (c) The University of Glasgow 2006
% (c) The AQUA Project, Glasgow University, 1996-1998
%

TcHsSyn: Specialisations of the @HsSyn@ syntax for the typechecker

This module is an extension of @HsSyn@ syntax, for use in the type
checker.

\begin{code}
module TcHsSyn (
	mkHsConApp, mkHsDictLet, mkHsApp,
	hsLitType, hsLPatType, hsPatType, 
	mkHsAppTy, mkSimpleHsAlt,
	nlHsIntLit, 
	shortCutLit, hsOverLitName,
	
	mkArbitraryType,	-- Put this elsewhere?

	-- re-exported from TcMonad
	TcId, TcIdSet, TcDictBinds,

	zonkTopDecls, zonkTopExpr, zonkTopLExpr,
	zonkId, zonkTopBndrs
  ) where

#include "HsVersions.h"

-- friends:
import HsSyn	-- oodles of it

-- others:
import Id

import TcRnMonad
import PrelNames
import TcType
import TcMType
import TysPrim
import TysWiredIn
import TyCon
import DataCon
import Name
import Var
import VarSet
import VarEnv
import Literal
import BasicTypes
import Maybes
import SrcLoc
import Util
import Bag
import Outputable
import FastString
\end{code}

\begin{code}
-- XXX
thenM :: Monad a => a b -> (b -> a c) -> a c
thenM = (>>=)

thenM_ :: Monad a => a b -> a c -> a c
thenM_ = (>>)

returnM :: Monad m => a -> m a
returnM = return

mappM :: (Monad m) => (a -> m b) -> [a] -> m [b]
mappM = mapM
\end{code}


%************************************************************************
%*									*
\subsection[mkFailurePair]{Code for pattern-matching and other failures}
%*									*
%************************************************************************

Note: If @hsLPatType@ doesn't bear a strong resemblance to @exprType@,
then something is wrong.
\begin{code}
hsLPatType :: OutPat Id -> Type
hsLPatType (L _ pat) = hsPatType pat

hsPatType :: Pat Id -> Type
hsPatType (ParPat pat)                = hsLPatType pat
hsPatType (WildPat ty)                = ty
hsPatType (VarPat var)                = idType var
hsPatType (VarPatOut var _)           = idType var
hsPatType (BangPat pat)               = hsLPatType pat
hsPatType (LazyPat pat)               = hsLPatType pat
hsPatType (LitPat lit)                = hsLitType lit
hsPatType (AsPat var _)               = idType (unLoc var)
hsPatType (ViewPat _ _ ty)            = ty
hsPatType (ListPat _ ty)              = mkListTy ty
hsPatType (PArrPat _ ty)              = mkPArrTy ty
hsPatType (TuplePat _ _ ty)           = ty
hsPatType (ConPatOut { pat_ty = ty }) = ty
hsPatType (SigPatOut _ ty)            = ty
hsPatType (NPat lit _ _)              = overLitType lit
hsPatType (NPlusKPat id _ _ _)        = idType (unLoc id)
hsPatType (CoPat _ _ ty)              = ty
hsPatType p                           = pprPanic "hsPatType" (ppr p)

hsLitType :: HsLit -> TcType
hsLitType (HsChar _)       = charTy
hsLitType (HsCharPrim _)   = charPrimTy
hsLitType (HsString _)     = stringTy
hsLitType (HsStringPrim _) = addrPrimTy
hsLitType (HsInt _)        = intTy
hsLitType (HsIntPrim _)    = intPrimTy
hsLitType (HsWordPrim _)   = wordPrimTy
hsLitType (HsInteger _ ty) = ty
hsLitType (HsRat _ ty)     = ty
hsLitType (HsFloatPrim _)  = floatPrimTy
hsLitType (HsDoublePrim _) = doublePrimTy
\end{code}

Overloaded literals. Here mainly becuase it uses isIntTy etc

\begin{code}
shortCutLit :: OverLitVal -> TcType -> Maybe (HsExpr TcId)
shortCutLit (HsIntegral i) ty
  | isIntTy ty && inIntRange i   = Just (HsLit (HsInt i))
  | isWordTy ty && inWordRange i = Just (mkLit wordDataCon (HsWordPrim i))
  | isIntegerTy ty 	       	 = Just (HsLit (HsInteger i ty))
  | otherwise		       	 = shortCutLit (HsFractional (fromInteger i)) ty
	-- The 'otherwise' case is important
	-- Consider (3 :: Float).  Syntactically it looks like an IntLit,
	-- so we'll call shortCutIntLit, but of course it's a float
	-- This can make a big difference for programs with a lot of
	-- literals, compiled without -O

shortCutLit (HsFractional f) ty
  | isFloatTy ty  = Just (mkLit floatDataCon  (HsFloatPrim f))
  | isDoubleTy ty = Just (mkLit doubleDataCon (HsDoublePrim f))
  | otherwise     = Nothing

shortCutLit (HsIsString s) ty
  | isStringTy ty = Just (HsLit (HsString s))
  | otherwise     = Nothing

mkLit :: DataCon -> HsLit -> HsExpr Id
mkLit con lit = HsApp (nlHsVar (dataConWrapId con)) (nlHsLit lit)

------------------------------
hsOverLitName :: OverLitVal -> Name
-- Get the canonical 'fromX' name for a particular OverLitVal
hsOverLitName (HsIntegral {})   = fromIntegerName
hsOverLitName (HsFractional {}) = fromRationalName
hsOverLitName (HsIsString {})   = fromStringName
\end{code}

%************************************************************************
%*									*
\subsection[BackSubst-HsBinds]{Running a substitution over @HsBinds@}
%*									*
%************************************************************************

\begin{code}
-- zonkId is used *during* typechecking just to zonk the Id's type
zonkId :: TcId -> TcM TcId
zonkId id
  = zonkTcType (idType id) `thenM` \ ty' ->
    returnM (Id.setIdType id ty')
\end{code}

The rest of the zonking is done *after* typechecking.
The main zonking pass runs over the bindings

 a) to convert TcTyVars to TyVars etc, dereferencing any bindings etc
 b) convert unbound TcTyVar to Void
 c) convert each TcId to an Id by zonking its type

The type variables are converted by binding mutable tyvars to immutable ones
and then zonking as normal.

The Ids are converted by binding them in the normal Tc envt; that
way we maintain sharing; eg an Id is zonked at its binding site and they
all occurrences of that Id point to the common zonked copy

It's all pretty boring stuff, because HsSyn is such a large type, and 
the environment manipulation is tiresome.

\begin{code}
data ZonkEnv = ZonkEnv	(TcType -> TcM Type) 	-- How to zonk a type
			(IdEnv Id)		-- What variables are in scope
	-- Maps an Id to its zonked version; both have the same Name
	-- Is only consulted lazily; hence knot-tying

emptyZonkEnv :: ZonkEnv
emptyZonkEnv = ZonkEnv zonkTypeZapping emptyVarEnv

extendZonkEnv :: ZonkEnv -> [Id] -> ZonkEnv
extendZonkEnv (ZonkEnv zonk_ty env) ids 
  = ZonkEnv zonk_ty (extendVarEnvList env [(id,id) | id <- ids])

extendZonkEnv1 :: ZonkEnv -> Id -> ZonkEnv
extendZonkEnv1 (ZonkEnv zonk_ty env) id 
  = ZonkEnv zonk_ty (extendVarEnv env id id)

setZonkType :: ZonkEnv -> (TcType -> TcM Type) -> ZonkEnv
setZonkType (ZonkEnv _ env) zonk_ty = ZonkEnv zonk_ty env

zonkEnvIds :: ZonkEnv -> [Id]
zonkEnvIds (ZonkEnv _ env) = varEnvElts env

zonkIdOcc :: ZonkEnv -> TcId -> Id
-- Ids defined in this module should be in the envt; 
-- ignore others.  (Actually, data constructors are also
-- not LocalVars, even when locally defined, but that is fine.)
-- (Also foreign-imported things aren't currently in the ZonkEnv;
--  that's ok because they don't need zonking.)
--
-- Actually, Template Haskell works in 'chunks' of declarations, and
-- an earlier chunk won't be in the 'env' that the zonking phase 
-- carries around.  Instead it'll be in the tcg_gbl_env, already fully
-- zonked.  There's no point in looking it up there (except for error 
-- checking), and it's not conveniently to hand; hence the simple
-- 'orElse' case in the LocalVar branch.
--
-- Even without template splices, in module Main, the checking of
-- 'main' is done as a separate chunk.
zonkIdOcc (ZonkEnv _zonk_ty env) id 
  | isLocalVar id = lookupVarEnv env id `orElse` id
  | otherwise	  = id

zonkIdOccs :: ZonkEnv -> [TcId] -> [Id]
zonkIdOccs env ids = map (zonkIdOcc env) ids

-- zonkIdBndr is used *after* typechecking to get the Id's type
-- to its final form.  The TyVarEnv give 
zonkIdBndr :: ZonkEnv -> TcId -> TcM Id
zonkIdBndr env id
  = zonkTcTypeToType env (idType id)	`thenM` \ ty' ->
    returnM (Id.setIdType id ty')

zonkIdBndrs :: ZonkEnv -> [TcId] -> TcM [Id]
zonkIdBndrs env ids = mappM (zonkIdBndr env) ids

zonkDictBndrs :: ZonkEnv -> [Var] -> TcM [Var]
-- "Dictionary" binders can be coercion variables or dictionary variables
zonkDictBndrs env ids = mappM (zonkDictBndr env) ids

zonkDictBndr :: ZonkEnv -> Var -> TcM Var
zonkDictBndr env var | isTyVar var = zonkTyVarBndr env var
		     | otherwise   = zonkIdBndr env var

zonkTopBndrs :: [TcId] -> TcM [Id]
zonkTopBndrs ids = zonkIdBndrs emptyZonkEnv ids

-- Zonk the kind of a non-TC tyvar in case it is a coercion variable (their
-- kind contains types).
--
zonkTyVarBndr :: ZonkEnv -> TyVar -> TcM TyVar
zonkTyVarBndr env tv
  | isCoVar tv
  = do { kind <- zonkTcTypeToType env (tyVarKind tv)
       ; return $ setTyVarKind tv kind
       }
  | otherwise = return tv
\end{code}


\begin{code}
zonkTopExpr :: HsExpr TcId -> TcM (HsExpr Id)
zonkTopExpr e = zonkExpr emptyZonkEnv e

zonkTopLExpr :: LHsExpr TcId -> TcM (LHsExpr Id)
zonkTopLExpr e = zonkLExpr emptyZonkEnv e

zonkTopDecls :: LHsBinds TcId -> [LRuleDecl TcId] -> [LForeignDecl TcId]
	     -> TcM ([Id], 
		     Bag (LHsBind  Id),
		     [LForeignDecl Id],
		     [LRuleDecl    Id])
zonkTopDecls binds rules fords
  = do	{ (env, binds') <- zonkRecMonoBinds emptyZonkEnv binds
			-- Top level is implicitly recursive
	; rules' <- zonkRules env rules
	; fords' <- zonkForeignExports env fords
	; return (zonkEnvIds env, binds', fords', rules') }

---------------------------------------------
zonkLocalBinds :: ZonkEnv -> HsLocalBinds TcId -> TcM (ZonkEnv, HsLocalBinds Id)
zonkLocalBinds env EmptyLocalBinds
  = return (env, EmptyLocalBinds)

zonkLocalBinds env (HsValBinds binds)
  = do	{ (env1, new_binds) <- zonkValBinds env binds
	; return (env1, HsValBinds new_binds) }

zonkLocalBinds env (HsIPBinds (IPBinds binds dict_binds))
  = mappM (wrapLocM zonk_ip_bind) binds	`thenM` \ new_binds ->
    let
	env1 = extendZonkEnv env [ipNameName n | L _ (IPBind n _) <- new_binds]
    in
    zonkRecMonoBinds env1 dict_binds 	`thenM` \ (env2, new_dict_binds) -> 
    returnM (env2, HsIPBinds (IPBinds new_binds new_dict_binds))
  where
    zonk_ip_bind (IPBind n e)
	= mapIPNameTc (zonkIdBndr env) n	`thenM` \ n' ->
	  zonkLExpr env e			`thenM` \ e' ->
	  returnM (IPBind n' e')


---------------------------------------------
zonkValBinds :: ZonkEnv -> HsValBinds TcId -> TcM (ZonkEnv, HsValBinds Id)
zonkValBinds _ (ValBindsIn _ _) 
  = panic "zonkValBinds" -- Not in typechecker output
zonkValBinds env (ValBindsOut binds sigs) 
  = do 	{ (env1, new_binds) <- go env binds
	; return (env1, ValBindsOut new_binds sigs) }
  where
    go env []         = return (env, [])
    go env ((r,b):bs) = do { (env1, b')  <- zonkRecMonoBinds env b
			   ; (env2, bs') <- go env1 bs
			   ; return (env2, (r,b'):bs') }

---------------------------------------------
zonkRecMonoBinds :: ZonkEnv -> LHsBinds TcId -> TcM (ZonkEnv, LHsBinds Id)
zonkRecMonoBinds env binds 
 = fixM (\ ~(_, new_binds) -> do 
	{ let env1 = extendZonkEnv env (collectHsBindBinders new_binds)
        ; binds' <- zonkMonoBinds env1 binds
        ; return (env1, binds') })

---------------------------------------------
zonkMonoBinds :: ZonkEnv -> LHsBinds TcId -> TcM (LHsBinds Id)
zonkMonoBinds env binds = mapBagM (wrapLocM (zonk_bind env)) binds

zonk_bind :: ZonkEnv -> HsBind TcId -> TcM (HsBind Id)
zonk_bind env bind@(PatBind { pat_lhs = pat, pat_rhs = grhss, pat_rhs_ty = ty})
  = do	{ (_env, new_pat) <- zonkPat env pat		-- Env already extended
	; new_grhss <- zonkGRHSs env grhss
	; new_ty    <- zonkTcTypeToType env ty
	; return (bind { pat_lhs = new_pat, pat_rhs = new_grhss, pat_rhs_ty = new_ty }) }

zonk_bind env (VarBind { var_id = var, var_rhs = expr })
  = zonkIdBndr env var 			`thenM` \ new_var ->
    zonkLExpr env expr			`thenM` \ new_expr ->
    returnM (VarBind { var_id = new_var, var_rhs = new_expr })

zonk_bind env bind@(FunBind { fun_id = var, fun_matches = ms, fun_co_fn = co_fn })
  = wrapLocM (zonkIdBndr env) var	`thenM` \ new_var ->
    zonkCoFn env co_fn			`thenM` \ (env1, new_co_fn) ->
    zonkMatchGroup env1 ms		`thenM` \ new_ms ->
    returnM (bind { fun_id = new_var, fun_matches = new_ms, fun_co_fn = new_co_fn })

zonk_bind env (AbsBinds { abs_tvs = tyvars, abs_dicts = dicts, 
			  abs_exports = exports, abs_binds = val_binds })
  = ASSERT( all isImmutableTyVar tyvars )
    zonkDictBndrs env dicts			`thenM` \ new_dicts ->
    fixM (\ ~(new_val_binds, _) ->
	let
	  env1 = extendZonkEnv env new_dicts
	  env2 = extendZonkEnv env1 (collectHsBindBinders new_val_binds)
	in
	zonkMonoBinds env2 val_binds 		`thenM` \ new_val_binds ->
        mappM (zonkExport env2) exports		`thenM` \ new_exports ->
	returnM (new_val_binds, new_exports)
    )						`thenM` \ (new_val_bind, new_exports) ->
    returnM (AbsBinds { abs_tvs = tyvars, abs_dicts = new_dicts, 
			abs_exports = new_exports, abs_binds = new_val_bind })
  where
    zonkExport env (tyvars, global, local, prags)
	-- The tyvars are already zonked
	= zonkIdBndr env global			`thenM` \ new_global ->
	  mapM zonk_prag prags			`thenM` \ new_prags -> 
	  returnM (tyvars, new_global, zonkIdOcc env local, new_prags)
    zonk_prag prag@(L _ (InlinePrag {}))  = return prag
    zonk_prag (L loc (SpecPrag expr ty inl))
	= do { expr' <- zonkExpr env expr 
	     ; ty'   <- zonkTcTypeToType env ty
	     ; return (L loc (SpecPrag expr' ty' inl)) }
\end{code}

%************************************************************************
%*									*
\subsection[BackSubst-Match-GRHSs]{Match and GRHSs}
%*									*
%************************************************************************

\begin{code}
zonkMatchGroup :: ZonkEnv -> MatchGroup TcId-> TcM (MatchGroup Id)
zonkMatchGroup env (MatchGroup ms ty) 
  = do	{ ms' <- mapM (zonkMatch env) ms
	; ty' <- zonkTcTypeToType env ty
	; return (MatchGroup ms' ty') }

zonkMatch :: ZonkEnv -> LMatch TcId-> TcM (LMatch Id)
zonkMatch env (L loc (Match pats _ grhss))
  = do	{ (env1, new_pats) <- zonkPats env pats
	; new_grhss <- zonkGRHSs env1 grhss
	; return (L loc (Match new_pats Nothing new_grhss)) }

-------------------------------------------------------------------------
zonkGRHSs :: ZonkEnv -> GRHSs TcId -> TcM (GRHSs Id)

zonkGRHSs env (GRHSs grhss binds)
  = zonkLocalBinds env binds   	`thenM` \ (new_env, new_binds) ->
    let
	zonk_grhs (GRHS guarded rhs)
	  = zonkStmts new_env guarded	`thenM` \ (env2, new_guarded) ->
	    zonkLExpr env2 rhs		`thenM` \ new_rhs ->
	    returnM (GRHS new_guarded new_rhs)
    in
    mappM (wrapLocM zonk_grhs) grhss 	`thenM` \ new_grhss ->
    returnM (GRHSs new_grhss new_binds)
\end{code}

%************************************************************************
%*									*
\subsection[BackSubst-HsExpr]{Running a zonkitution over a TypeCheckedExpr}
%*									*
%************************************************************************

\begin{code}
zonkLExprs :: ZonkEnv -> [LHsExpr TcId] -> TcM [LHsExpr Id]
zonkLExpr  :: ZonkEnv -> LHsExpr TcId   -> TcM (LHsExpr Id)
zonkExpr   :: ZonkEnv -> HsExpr TcId    -> TcM (HsExpr Id)

zonkLExprs env exprs = mappM (zonkLExpr env) exprs
zonkLExpr  env expr  = wrapLocM (zonkExpr env) expr

zonkExpr env (HsVar id)
  = returnM (HsVar (zonkIdOcc env id))

zonkExpr env (HsIPVar id)
  = returnM (HsIPVar (mapIPName (zonkIdOcc env) id))

zonkExpr env (HsLit (HsRat f ty))
  = zonkTcTypeToType env ty	   `thenM` \ new_ty  ->
    returnM (HsLit (HsRat f new_ty))

zonkExpr _ (HsLit lit)
  = returnM (HsLit lit)

zonkExpr env (HsOverLit lit)
  = do	{ lit' <- zonkOverLit env lit
	; return (HsOverLit lit') }

zonkExpr env (HsLam matches)
  = zonkMatchGroup env matches	`thenM` \ new_matches ->
    returnM (HsLam new_matches)

zonkExpr env (HsApp e1 e2)
  = zonkLExpr env e1	`thenM` \ new_e1 ->
    zonkLExpr env e2	`thenM` \ new_e2 ->
    returnM (HsApp new_e1 new_e2)

zonkExpr env (HsBracketOut body bs) 
  = mappM zonk_b bs	`thenM` \ bs' ->
    returnM (HsBracketOut body bs')
  where
    zonk_b (n,e) = zonkLExpr env e	`thenM` \ e' ->
		   returnM (n,e')

zonkExpr _ (HsSpliceE s) = WARN( True, ppr s ) -- Should not happen
			     returnM (HsSpliceE s)

zonkExpr env (OpApp e1 op fixity e2)
  = zonkLExpr env e1	`thenM` \ new_e1 ->
    zonkLExpr env op	`thenM` \ new_op ->
    zonkLExpr env e2	`thenM` \ new_e2 ->
    returnM (OpApp new_e1 new_op fixity new_e2)

zonkExpr env (NegApp expr op)
  = zonkLExpr env expr	`thenM` \ new_expr ->
    zonkExpr env op	`thenM` \ new_op ->
    returnM (NegApp new_expr new_op)

zonkExpr env (HsPar e)    
  = zonkLExpr env e	`thenM` \new_e ->
    returnM (HsPar new_e)

zonkExpr env (SectionL expr op)
  = zonkLExpr env expr	`thenM` \ new_expr ->
    zonkLExpr env op		`thenM` \ new_op ->
    returnM (SectionL new_expr new_op)

zonkExpr env (SectionR op expr)
  = zonkLExpr env op		`thenM` \ new_op ->
    zonkLExpr env expr		`thenM` \ new_expr ->
    returnM (SectionR new_op new_expr)

zonkExpr env (ExplicitTuple tup_args boxed)
  = do { new_tup_args <- mapM zonk_tup_arg tup_args
       ; return (ExplicitTuple new_tup_args boxed) }
  where
    zonk_tup_arg (Present e) = do { e' <- zonkLExpr env e; return (Present e') }
    zonk_tup_arg (Missing t) = do { t' <- zonkTcTypeToType env t; return (Missing t') }

zonkExpr env (HsCase expr ms)
  = zonkLExpr env expr    	`thenM` \ new_expr ->
    zonkMatchGroup env ms	`thenM` \ new_ms ->
    returnM (HsCase new_expr new_ms)

zonkExpr env (HsIf e1 e2 e3)
  = zonkLExpr env e1	`thenM` \ new_e1 ->
    zonkLExpr env e2	`thenM` \ new_e2 ->
    zonkLExpr env e3	`thenM` \ new_e3 ->
    returnM (HsIf new_e1 new_e2 new_e3)

zonkExpr env (HsLet binds expr)
  = zonkLocalBinds env binds	`thenM` \ (new_env, new_binds) ->
    zonkLExpr new_env expr	`thenM` \ new_expr ->
    returnM (HsLet new_binds new_expr)

zonkExpr env (HsDo do_or_lc stmts body ty)
  = zonkStmts env stmts 	`thenM` \ (new_env, new_stmts) ->
    zonkLExpr new_env body	`thenM` \ new_body ->
    zonkTcTypeToType env ty	`thenM` \ new_ty   ->
    returnM (HsDo (zonkDo env do_or_lc) 
		  new_stmts new_body new_ty)

zonkExpr env (ExplicitList ty exprs)
  = zonkTcTypeToType env ty	`thenM` \ new_ty ->
    zonkLExprs env exprs	`thenM` \ new_exprs ->
    returnM (ExplicitList new_ty new_exprs)

zonkExpr env (ExplicitPArr ty exprs)
  = zonkTcTypeToType env ty	`thenM` \ new_ty ->
    zonkLExprs env exprs	`thenM` \ new_exprs ->
    returnM (ExplicitPArr new_ty new_exprs)

zonkExpr env (RecordCon data_con con_expr rbinds)
  = do	{ new_con_expr <- zonkExpr env con_expr
	; new_rbinds   <- zonkRecFields env rbinds
	; return (RecordCon data_con new_con_expr new_rbinds) }

zonkExpr env (RecordUpd expr rbinds cons in_tys out_tys)
  = do	{ new_expr    <- zonkLExpr env expr
	; new_in_tys  <- mapM (zonkTcTypeToType env) in_tys
	; new_out_tys <- mapM (zonkTcTypeToType env) out_tys
	; new_rbinds  <- zonkRecFields env rbinds
	; return (RecordUpd new_expr new_rbinds cons new_in_tys new_out_tys) }

zonkExpr env (ExprWithTySigOut e ty) 
  = do { e' <- zonkLExpr env e
       ; return (ExprWithTySigOut e' ty) }

zonkExpr _ (ExprWithTySig _ _) = panic "zonkExpr env:ExprWithTySig"

zonkExpr env (ArithSeq expr info)
  = zonkExpr env expr		`thenM` \ new_expr ->
    zonkArithSeq env info	`thenM` \ new_info ->
    returnM (ArithSeq new_expr new_info)

zonkExpr env (PArrSeq expr info)
  = zonkExpr env expr		`thenM` \ new_expr ->
    zonkArithSeq env info	`thenM` \ new_info ->
    returnM (PArrSeq new_expr new_info)

zonkExpr env (HsSCC lbl expr)
  = zonkLExpr env expr	`thenM` \ new_expr ->
    returnM (HsSCC lbl new_expr)

zonkExpr env (HsTickPragma info expr)
  = zonkLExpr env expr	`thenM` \ new_expr ->
    returnM (HsTickPragma info new_expr)

-- hdaume: core annotations
zonkExpr env (HsCoreAnn lbl expr)
  = zonkLExpr env expr   `thenM` \ new_expr ->
    returnM (HsCoreAnn lbl new_expr)

-- arrow notation extensions
zonkExpr env (HsProc pat body)
  = do	{ (env1, new_pat) <- zonkPat env pat
	; new_body <- zonkCmdTop env1 body
	; return (HsProc new_pat new_body) }

zonkExpr env (HsArrApp e1 e2 ty ho rl)
  = zonkLExpr env e1	    	    	`thenM` \ new_e1 ->
    zonkLExpr env e2	    	    	`thenM` \ new_e2 ->
    zonkTcTypeToType env ty 		`thenM` \ new_ty ->
    returnM (HsArrApp new_e1 new_e2 new_ty ho rl)

zonkExpr env (HsArrForm op fixity args)
  = zonkLExpr env op	    	    	`thenM` \ new_op ->
    mappM (zonkCmdTop env) args		`thenM` \ new_args ->
    returnM (HsArrForm new_op fixity new_args)

zonkExpr env (HsWrap co_fn expr)
  = zonkCoFn env co_fn	`thenM` \ (env1, new_co_fn) ->
    zonkExpr env1 expr	`thenM` \ new_expr ->
    return (HsWrap new_co_fn new_expr)

zonkExpr _ expr = pprPanic "zonkExpr" (ppr expr)

zonkCmdTop :: ZonkEnv -> LHsCmdTop TcId -> TcM (LHsCmdTop Id)
zonkCmdTop env cmd = wrapLocM (zonk_cmd_top env) cmd

zonk_cmd_top :: ZonkEnv -> HsCmdTop TcId -> TcM (HsCmdTop Id)
zonk_cmd_top env (HsCmdTop cmd stack_tys ty ids)
  = zonkLExpr env cmd	    		`thenM` \ new_cmd ->
    zonkTcTypeToTypes env stack_tys	`thenM` \ new_stack_tys ->
    zonkTcTypeToType env ty 		`thenM` \ new_ty ->
    mapSndM (zonkExpr env) ids		`thenM` \ new_ids ->
    returnM (HsCmdTop new_cmd new_stack_tys new_ty new_ids)

-------------------------------------------------------------------------
zonkCoFn :: ZonkEnv -> HsWrapper -> TcM (ZonkEnv, HsWrapper)
zonkCoFn env WpHole   = return (env, WpHole)
zonkCoFn env WpInline = return (env, WpInline)
zonkCoFn env (WpCompose c1 c2) = do { (env1, c1') <- zonkCoFn env c1
				    ; (env2, c2') <- zonkCoFn env1 c2
				    ; return (env2, WpCompose c1' c2') }
zonkCoFn env (WpCast co)    = do { co' <- zonkTcTypeToType env co
				 ; return (env, WpCast co') }
zonkCoFn env (WpLam id)     = do { id' <- zonkDictBndr env id
				 ; let env1 = extendZonkEnv1 env id'
				 ; return (env1, WpLam id') }
zonkCoFn env (WpTyLam tv)   = ASSERT( isImmutableTyVar tv )
                              do { tv' <- zonkTyVarBndr env tv
			         ; return (env, WpTyLam tv') }
zonkCoFn env (WpApp v)
	| isTcTyVar v  	    = do { co <- zonkTcTyVar v
				 ; return (env, WpTyApp co) }
		-- Yuk!  A mutable coercion variable is a TcTyVar 
		--	 not a CoVar, so don't use isCoVar!
		-- Yuk!  A WpApp can't hold the zonked type,
		--	 so we switch to WpTyApp
	| otherwise	    = return (env, WpApp (zonkIdOcc env v))
zonkCoFn env (WpTyApp ty)   = do { ty' <- zonkTcTypeToType env ty
				 ; return (env, WpTyApp ty') }
zonkCoFn env (WpLet bs)     = do { (env1, bs') <- zonkRecMonoBinds env bs
				 ; return (env1, WpLet bs') }


-------------------------------------------------------------------------
zonkDo :: ZonkEnv -> HsStmtContext Name -> HsStmtContext Name
-- Only used for 'do', so the only Ids are in a MDoExpr table
zonkDo env (MDoExpr tbl) = MDoExpr (mapSnd (zonkIdOcc env) tbl)
zonkDo _   do_or_lc      = do_or_lc

-------------------------------------------------------------------------
zonkOverLit :: ZonkEnv -> HsOverLit TcId -> TcM (HsOverLit Id)
zonkOverLit env lit@(OverLit { ol_witness = e, ol_type = ty })
  = do	{ ty' <- zonkTcTypeToType env ty
	; e' <- zonkExpr env e
 	; return (lit { ol_witness = e', ol_type = ty' }) }

-------------------------------------------------------------------------
zonkArithSeq :: ZonkEnv -> ArithSeqInfo TcId -> TcM (ArithSeqInfo Id)

zonkArithSeq env (From e)
  = zonkLExpr env e		`thenM` \ new_e ->
    returnM (From new_e)

zonkArithSeq env (FromThen e1 e2)
  = zonkLExpr env e1	`thenM` \ new_e1 ->
    zonkLExpr env e2	`thenM` \ new_e2 ->
    returnM (FromThen new_e1 new_e2)

zonkArithSeq env (FromTo e1 e2)
  = zonkLExpr env e1	`thenM` \ new_e1 ->
    zonkLExpr env e2	`thenM` \ new_e2 ->
    returnM (FromTo new_e1 new_e2)

zonkArithSeq env (FromThenTo e1 e2 e3)
  = zonkLExpr env e1	`thenM` \ new_e1 ->
    zonkLExpr env e2	`thenM` \ new_e2 ->
    zonkLExpr env e3	`thenM` \ new_e3 ->
    returnM (FromThenTo new_e1 new_e2 new_e3)


-------------------------------------------------------------------------
zonkStmts :: ZonkEnv -> [LStmt TcId] -> TcM (ZonkEnv, [LStmt Id])
zonkStmts env []     = return (env, [])
zonkStmts env (s:ss) = do { (env1, s')  <- wrapLocSndM (zonkStmt env) s
			  ; (env2, ss') <- zonkStmts env1 ss
			  ; return (env2, s' : ss') }

zonkStmt :: ZonkEnv -> Stmt TcId -> TcM (ZonkEnv, Stmt Id)
zonkStmt env (ParStmt stmts_w_bndrs)
  = mappM zonk_branch stmts_w_bndrs	`thenM` \ new_stmts_w_bndrs ->
    let 
	new_binders = concat (map snd new_stmts_w_bndrs)
	env1 = extendZonkEnv env new_binders
    in
    return (env1, ParStmt new_stmts_w_bndrs)
  where
    zonk_branch (stmts, bndrs) = zonkStmts env stmts	`thenM` \ (env1, new_stmts) ->
				 returnM (new_stmts, zonkIdOccs env1 bndrs)

zonkStmt env (RecStmt { recS_stmts = segStmts, recS_later_ids = lvs, recS_rec_ids = rvs
                      , recS_ret_fn = ret_id, recS_mfix_fn = mfix_id, recS_bind_fn = bind_id
                      , recS_rec_rets = rets, recS_dicts = binds })
  = do { new_rvs <- zonkIdBndrs env rvs
       ; new_lvs <- zonkIdBndrs env lvs
       ; new_ret_id  <- zonkExpr env ret_id
       ; new_mfix_id <- zonkExpr env mfix_id
       ; new_bind_id <- zonkExpr env bind_id
       ; let env1 = extendZonkEnv env new_rvs
       ; (env2, new_segStmts) <- zonkStmts env1 segStmts
	-- Zonk the ret-expressions in an envt that 
	-- has the polymorphic bindings in the envt
       ; new_rets <- mapM (zonkExpr env2) rets
       ; let env3 = extendZonkEnv env new_lvs	-- Only the lvs are needed
       ; (env4, new_binds) <- zonkRecMonoBinds env3 binds
       ; return (env4,
                 RecStmt { recS_stmts = new_segStmts, recS_later_ids = new_lvs
                         , recS_rec_ids = new_rvs, recS_ret_fn = new_ret_id
                         , recS_mfix_fn = new_mfix_id, recS_bind_fn = new_bind_id
                         , recS_rec_rets = new_rets, recS_dicts = new_binds }) }

zonkStmt env (ExprStmt expr then_op ty)
  = zonkLExpr env expr		`thenM` \ new_expr ->
    zonkExpr env then_op	`thenM` \ new_then ->
    zonkTcTypeToType env ty	`thenM` \ new_ty ->
    returnM (env, ExprStmt new_expr new_then new_ty)

zonkStmt env (TransformStmt (stmts, binders) usingExpr maybeByExpr)
  = do { (env', stmts') <- zonkStmts env stmts 
    ; let binders' = zonkIdOccs env' binders
    ; usingExpr' <- zonkLExpr env' usingExpr
    ; maybeByExpr' <- zonkMaybeLExpr env' maybeByExpr
    ; return (env', TransformStmt (stmts', binders') usingExpr' maybeByExpr') }
    
zonkStmt env (GroupStmt (stmts, binderMap) groupByClause)
  = do { (env', stmts') <- zonkStmts env stmts 
    ; binderMap' <- mappM (zonkBinderMapEntry env') binderMap
    ; groupByClause' <- 
        case groupByClause of
            GroupByNothing usingExpr -> (zonkLExpr env' usingExpr) >>= (return . GroupByNothing)
            GroupBySomething eitherUsingExpr byExpr -> do
                eitherUsingExpr' <- mapEitherM (zonkLExpr env') (zonkExpr env') eitherUsingExpr
                byExpr' <- zonkLExpr env' byExpr
                return $ GroupBySomething eitherUsingExpr' byExpr'
                
    ; let env'' = extendZonkEnv env' (map snd binderMap')
    ; return (env'', GroupStmt (stmts', binderMap') groupByClause') }
  where
    mapEitherM f g x = do
      case x of
        Left a -> f a >>= (return . Left)
        Right b -> g b >>= (return . Right)
  
    zonkBinderMapEntry env (oldBinder, newBinder) = do 
        let oldBinder' = zonkIdOcc env oldBinder
        newBinder' <- zonkIdBndr env newBinder
        return (oldBinder', newBinder') 

zonkStmt env (LetStmt binds)
  = zonkLocalBinds env binds	`thenM` \ (env1, new_binds) ->
    returnM (env1, LetStmt new_binds)

zonkStmt env (BindStmt pat expr bind_op fail_op)
  = do	{ new_expr <- zonkLExpr env expr
	; (env1, new_pat) <- zonkPat env pat
	; new_bind <- zonkExpr env bind_op
	; new_fail <- zonkExpr env fail_op
	; return (env1, BindStmt new_pat new_expr new_bind new_fail) }

zonkMaybeLExpr :: ZonkEnv -> Maybe (LHsExpr TcId) -> TcM (Maybe (LHsExpr Id))
zonkMaybeLExpr _   Nothing  = return Nothing
zonkMaybeLExpr env (Just e) = (zonkLExpr env e) >>= (return . Just)


-------------------------------------------------------------------------
zonkRecFields :: ZonkEnv -> HsRecordBinds TcId -> TcM (HsRecordBinds TcId)
zonkRecFields env (HsRecFields flds dd)
  = do	{ flds' <- mappM zonk_rbind flds
	; return (HsRecFields flds' dd) }
  where
    zonk_rbind fld
      = do { new_id   <- wrapLocM (zonkIdBndr env) (hsRecFieldId fld)
	   ; new_expr <- zonkLExpr env (hsRecFieldArg fld)
	   ; return (fld { hsRecFieldId = new_id, hsRecFieldArg = new_expr }) }

-------------------------------------------------------------------------
mapIPNameTc :: (a -> TcM b) -> IPName a -> TcM (IPName b)
mapIPNameTc f (IPName n) = f n  `thenM` \ r -> returnM (IPName r)
\end{code}


%************************************************************************
%*									*
\subsection[BackSubst-Pats]{Patterns}
%*									*
%************************************************************************

\begin{code}
zonkPat :: ZonkEnv -> OutPat TcId -> TcM (ZonkEnv, OutPat Id)
-- Extend the environment as we go, because it's possible for one
-- pattern to bind something that is used in another (inside or
-- to the right)
zonkPat env pat = wrapLocSndM (zonk_pat env) pat

zonk_pat :: ZonkEnv -> Pat TcId -> TcM (ZonkEnv, Pat Id)
zonk_pat env (ParPat p)
  = do	{ (env', p') <- zonkPat env p
  	; return (env', ParPat p') }

zonk_pat env (WildPat ty)
  = do	{ ty' <- zonkTcTypeToType env ty
	; return (env, WildPat ty') }

zonk_pat env (VarPat v)
  = do	{ v' <- zonkIdBndr env v
	; return (extendZonkEnv1 env v', VarPat v') }

zonk_pat env (VarPatOut v binds)
  = do	{ v' <- zonkIdBndr env v
	; (env', binds') <- zonkRecMonoBinds (extendZonkEnv1 env v') binds
  	; returnM (env', VarPatOut v' binds') }

zonk_pat env (LazyPat pat)
  = do	{ (env', pat') <- zonkPat env pat
	; return (env',  LazyPat pat') }

zonk_pat env (BangPat pat)
  = do	{ (env', pat') <- zonkPat env pat
	; return (env',  BangPat pat') }

zonk_pat env (AsPat (L loc v) pat)
  = do	{ v' <- zonkIdBndr env v
	; (env', pat') <- zonkPat (extendZonkEnv1 env v') pat
 	; return (env', AsPat (L loc v') pat') }

zonk_pat env (ViewPat expr pat ty)
  = do	{ expr' <- zonkLExpr env expr
	; (env', pat') <- zonkPat env pat
 	; ty' <- zonkTcTypeToType env ty
	; return (env', ViewPat expr' pat' ty') }

zonk_pat env (ListPat pats ty)
  = do	{ ty' <- zonkTcTypeToType env ty
	; (env', pats') <- zonkPats env pats
	; return (env', ListPat pats' ty') }

zonk_pat env (PArrPat pats ty)
  = do	{ ty' <- zonkTcTypeToType env ty
	; (env', pats') <- zonkPats env pats
	; return (env', PArrPat pats' ty') }

zonk_pat env (TuplePat pats boxed ty)
  = do	{ ty' <- zonkTcTypeToType env ty
	; (env', pats') <- zonkPats env pats
	; return (env', TuplePat pats' boxed ty') }

zonk_pat env p@(ConPatOut { pat_ty = ty, pat_dicts = dicts, pat_binds = binds, pat_args = args })
  = ASSERT( all isImmutableTyVar (pat_tvs p) ) 
    do	{ new_ty <- zonkTcTypeToType env ty
	; new_dicts <- zonkDictBndrs env dicts
	; let env1 = extendZonkEnv env new_dicts
	; (env2, new_binds) <- zonkRecMonoBinds env1 binds
	; (env', new_args) <- zonkConStuff env2 args
	; returnM (env', p { pat_ty = new_ty, pat_dicts = new_dicts, 
			     pat_binds = new_binds, pat_args = new_args }) }

zonk_pat env (LitPat lit) = return (env, LitPat lit)

zonk_pat env (SigPatOut pat ty)
  = do	{ ty' <- zonkTcTypeToType env ty
	; (env', pat') <- zonkPat env pat
	; return (env', SigPatOut pat' ty') }

zonk_pat env (NPat lit mb_neg eq_expr)
  = do	{ lit' <- zonkOverLit env lit
 	; mb_neg' <- case mb_neg of
			Nothing  -> return Nothing
			Just neg -> do { neg' <- zonkExpr env neg
				       ; return (Just neg') }
 	; eq_expr' <- zonkExpr env eq_expr
	; return (env, NPat lit' mb_neg' eq_expr') }

zonk_pat env (NPlusKPat (L loc n) lit e1 e2)
  = do	{ n' <- zonkIdBndr env n
	; lit' <- zonkOverLit env lit
 	; e1' <- zonkExpr env e1
	; e2' <- zonkExpr env e2
	; return (extendZonkEnv1 env n', NPlusKPat (L loc n') lit' e1' e2') }

zonk_pat env (CoPat co_fn pat ty) 
  = do { (env', co_fn') <- zonkCoFn env co_fn
       ; (env'', pat') <- zonkPat env' (noLoc pat)
       ; ty' <- zonkTcTypeToType env'' ty
       ; return (env'', CoPat co_fn' (unLoc pat') ty') }

zonk_pat _ pat = pprPanic "zonk_pat" (ppr pat)

---------------------------
zonkConStuff :: ZonkEnv
             -> HsConDetails (OutPat TcId) (HsRecFields id (OutPat TcId))
             -> TcM (ZonkEnv,
                     HsConDetails (OutPat Id) (HsRecFields id (OutPat Id)))
zonkConStuff env (PrefixCon pats)
  = do	{ (env', pats') <- zonkPats env pats
	; return (env', PrefixCon pats') }

zonkConStuff env (InfixCon p1 p2)
  = do	{ (env1, p1') <- zonkPat env  p1
	; (env', p2') <- zonkPat env1 p2
	; return (env', InfixCon p1' p2') }

zonkConStuff env (RecCon (HsRecFields rpats dd))
  = do	{ (env', pats') <- zonkPats env (map hsRecFieldArg rpats)
	; let rpats' = zipWith (\rp p' -> rp { hsRecFieldArg = p' }) rpats pats'
	; returnM (env', RecCon (HsRecFields rpats' dd)) }
	-- Field selectors have declared types; hence no zonking

---------------------------
zonkPats :: ZonkEnv -> [OutPat TcId] -> TcM (ZonkEnv, [OutPat Id])
zonkPats env []		= return (env, [])
zonkPats env (pat:pats) = do { (env1, pat') <- zonkPat env pat
		     ; (env', pats') <- zonkPats env1 pats
		     ; return (env', pat':pats') }
\end{code}

%************************************************************************
%*									*
\subsection[BackSubst-Foreign]{Foreign exports}
%*									*
%************************************************************************


\begin{code}
zonkForeignExports :: ZonkEnv -> [LForeignDecl TcId] -> TcM [LForeignDecl Id]
zonkForeignExports env ls = mappM (wrapLocM (zonkForeignExport env)) ls

zonkForeignExport :: ZonkEnv -> ForeignDecl TcId -> TcM (ForeignDecl Id)
zonkForeignExport env (ForeignExport i _hs_ty spec) =
   returnM (ForeignExport (fmap (zonkIdOcc env) i) undefined spec)
zonkForeignExport _ for_imp 
  = returnM for_imp	-- Foreign imports don't need zonking
\end{code}

\begin{code}
zonkRules :: ZonkEnv -> [LRuleDecl TcId] -> TcM [LRuleDecl Id]
zonkRules env rs = mappM (wrapLocM (zonkRule env)) rs

zonkRule :: ZonkEnv -> RuleDecl TcId -> TcM (RuleDecl Id)
zonkRule env (HsRule name act (vars{-::[RuleBndr TcId]-}) lhs fv_lhs rhs fv_rhs)
  = mappM zonk_bndr vars		`thenM` \ new_bndrs ->
    newMutVar emptyVarSet		`thenM` \ unbound_tv_set ->
    let
	env_rhs = extendZonkEnv env [id | b <- new_bndrs, let id = unLoc b, isId id]
	-- Type variables don't need an envt
	-- They are bound through the mutable mechanism

	env_lhs = setZonkType env_rhs (zonkTypeCollecting unbound_tv_set)
	-- We need to gather the type variables mentioned on the LHS so we can 
	-- quantify over them.  Example:
	--   data T a = C
	-- 
	--   foo :: T a -> Int
	--   foo C = 1
	--
	--   {-# RULES "myrule"  foo C = 1 #-}
	-- 
	-- After type checking the LHS becomes (foo a (C a))
	-- and we do not want to zap the unbound tyvar 'a' to (), because
	-- that limits the applicability of the rule.  Instead, we
	-- want to quantify over it!  
	--
	-- It's easiest to find the free tyvars here. Attempts to do so earlier
	-- are tiresome, because (a) the data type is big and (b) finding the 
	-- free type vars of an expression is necessarily monadic operation.
	--	(consider /\a -> f @ b, where b is side-effected to a)
    in
    zonkLExpr env_lhs lhs		`thenM` \ new_lhs ->
    zonkLExpr env_rhs rhs		`thenM` \ new_rhs ->

    readMutVar unbound_tv_set		`thenM` \ unbound_tvs ->
    let
	final_bndrs :: [Located Var]
	final_bndrs = map noLoc (varSetElems unbound_tvs) ++ new_bndrs
    in
    returnM (HsRule name act (map RuleBndr final_bndrs) new_lhs fv_lhs new_rhs fv_rhs)
		-- I hate this map RuleBndr stuff
  where
   zonk_bndr (RuleBndr v) 
	| isId (unLoc v) = wrapLocM (zonkIdBndr env)   v
	| otherwise      = ASSERT( isImmutableTyVar (unLoc v) )
			   return v
   zonk_bndr (RuleBndrSig {}) = panic "zonk_bndr RuleBndrSig"
\end{code}


%************************************************************************
%*									*
\subsection[BackSubst-Foreign]{Foreign exports}
%*									*
%************************************************************************

\begin{code}
zonkTcTypeToType :: ZonkEnv -> TcType -> TcM Type
zonkTcTypeToType (ZonkEnv zonk_ty _) ty = zonk_ty ty

zonkTcTypeToTypes :: ZonkEnv -> [TcType] -> TcM [Type]
zonkTcTypeToTypes env tys = mapM (zonkTcTypeToType env) tys

zonkTypeCollecting :: TcRef TyVarSet -> TcType -> TcM Type
-- This variant collects unbound type variables in a mutable variable
zonkTypeCollecting unbound_tv_set
  = zonkType zonk_unbound_tyvar
  where
    zonk_unbound_tyvar tv 
	= zonkQuantifiedTyVar tv				`thenM` \ tv' ->
	  readMutVar unbound_tv_set				`thenM` \ tv_set ->
	  writeMutVar unbound_tv_set (extendVarSet tv_set tv')	`thenM_`
	  return (mkTyVarTy tv')

zonkTypeZapping :: TcType -> TcM Type
-- This variant is used for everything except the LHS of rules
-- It zaps unbound type variables to (), or some other arbitrary type
zonkTypeZapping ty 
  = zonkType zonk_unbound_tyvar ty 
  where
	-- Zonk a mutable but unbound type variable to an arbitrary type
	-- We know it's unbound even though we don't carry an environment,
	-- because at the binding site for a type variable we bind the
	-- mutable tyvar to a fresh immutable one.  So the mutable store
	-- plays the role of an environment.  If we come across a mutable
	-- type variable that isn't so bound, it must be completely free.
    zonk_unbound_tyvar tv = do { ty <- mkArbitraryType warn tv
			       ; writeMetaTyVar tv ty
			       ; return ty }
	where
	    warn span msg = setSrcSpan span (addWarnTc msg)


{- 	Note [Strangely-kinded void TyCons]
	~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	See Trac #959 for more examples

When the type checker finds a type variable with no binding, which
means it can be instantiated with an arbitrary type, it usually
instantiates it to Void.  Eg.

	length []
===>
	length Void (Nil Void)

But in really obscure programs, the type variable might have a kind
other than *, so we need to invent a suitably-kinded type.

This commit uses
	Void for kind *
	List for kind *->*
	Tuple for kind *->...*->*

which deals with most cases.  (Previously, it only dealt with
kind *.)   

In the other cases, it just makes up a TyCon with a suitable kind.  If
this gets into an interface file, anyone reading that file won't
understand it.  This is fixable (by making the client of the interface
file make up a TyCon too) but it is tiresome and never happens, so I
am leaving it.

Meanwhile I have now fixed GHC to emit a civilized warning.
 -}

mkArbitraryType :: (SrcSpan -> SDoc -> TcRnIf g l a)	-- How to complain
		-> TcTyVar
		-> TcRnIf g l Type		-- Used by desugarer too
-- Make up an arbitrary type whose kind is the same as the tyvar.
-- We'll use this to instantiate the (unbound) tyvar.
--
-- Also used by the desugarer; hence the (tiresome) parameter
-- to use when generating a warning
mkArbitraryType warn tv 
  | liftedTypeKind `isSubKind` kind 		-- The vastly common case
  = return anyPrimTy
  | eqKind kind (tyConKind anyPrimTyCon1) 	-- @*->*@
  = return (mkTyConApp anyPrimTyCon1 [])	--     No tuples this size
  | all isLiftedTypeKind args 			-- @*-> ... ->*->*@
  , isLiftedTypeKind res			--    Horrible hack to make less use 
  = return (mkTyConApp tup_tc [])		--    of mkAnyPrimTyCon
  | otherwise
  = do	{ _ <- warn (getSrcSpan tv) msg
	; return (mkTyConApp (mkAnyPrimTyCon (getUnique tv) kind) []) }
		-- Same name as the tyvar, apart from making it start with a colon (sigh)
		-- I dread to think what will happen if this gets out into an 
		-- interface file.  Catastrophe likely.  Major sigh.
  where
    kind       = tyVarKind tv
    (args,res) = splitKindFunTys kind
    tup_tc     = tupleTyCon Boxed (length args)
		
    msg = vcat [ hang (ptext (sLit "Inventing strangely-kinded Any TyCon"))
		    2 (ptext (sLit "of kind") <+> quotes (ppr kind))
	       , nest 2 (ptext (sLit "from an instantiation of type variable") <+> quotes (ppr tv))
	       , ptext (sLit "This warning can be suppressed by a type signature fixing") <+> quotes (ppr tv)
	       , nest 2 (ptext (sLit "but is harmless without -O (and usually harmless anyway)."))
	       , ptext (sLit "See http://hackage.haskell.org/trac/ghc/ticket/959 for details")  ]
\end{code}