--------------------------------
-- Creating new mutable type variables
- newTyVar, newHoleTyVarTy,
- newTyVarTy, -- Kind -> NF_TcM TcType
- newTyVarTys, -- Int -> Kind -> NF_TcM [TcType]
- newKindVar, newKindVars, newBoxityVar,
- putTcTyVar, getTcTyVar,
+ newFlexiTyVar,
+ newTyFlexiVarTy, -- Kind -> TcM TcType
+ newTyFlexiVarTys, -- Int -> Kind -> TcM [TcType]
+ newKindVar, newKindVars,
+ lookupTcTyVar, condLookupTcTyVar, LookupTyVarResult(..),
+ newMetaTyVar, readMetaTyVar, writeMetaTyVar, putMetaTyVar,
--------------------------------
-- Instantiation
- tcInstTyVar, tcInstTyVars,
- tcInstSigTyVars, tcInstType,
- tcSplitRhoTyM,
+ tcInstTyVar, tcInstTyVars, tcInstType,
+ tcSkolType, tcSkolTyVars, tcInstSigType,
+ tcSkolSigType, tcSkolSigTyVars,
--------------------------------
-- Checking type validity
- Rank, UserTypeCtxt(..), checkValidType, pprUserTypeCtxt,
- SourceTyCtxt(..), checkValidTheta,
- checkValidInstHead, instTypeErr,
+ Rank, UserTypeCtxt(..), checkValidType, pprHsSigCtxt,
+ SourceTyCtxt(..), checkValidTheta, checkFreeness,
+ checkValidInstHead, instTypeErr, checkAmbiguity,
+ arityErr,
--------------------------------
-- Zonking
- zonkTcTyVar, zonkTcTyVars, zonkTcTyVarsAndFV, zonkTcSigTyVars,
+ zonkType, zonkTcPredType,
+ zonkTcTyVar, zonkTcTyVars, zonkTcTyVarsAndFV, zonkQuantifiedTyVar,
zonkTcType, zonkTcTypes, zonkTcClassConstraints, zonkTcThetaType,
- zonkTcPredType, zonkTcTypeToType, zonkTcTyVarToTyVar, zonkKindEnv,
+ zonkTcKindToKind, zonkTcKind,
+
+ readKindVar, writeKindVar
) where
-- friends:
-import TypeRep ( Type(..), SourceType(..), TyNote(..), -- Friend; can see representation
- Kind, ThetaType
+import HsSyn ( LHsType )
+import TypeRep ( Type(..), PredType(..), TyNote(..), -- Friend; can see representation
+ ThetaType
)
import TcType ( TcType, TcThetaType, TcTauType, TcPredType,
- TcTyVarSet, TcKind, TcTyVar, TyVarDetails(..),
- tcEqType, tcCmpPred,
- tcSplitRhoTy, tcSplitPredTy_maybe, tcSplitAppTy_maybe,
+ TcTyVarSet, TcKind, TcTyVar, TcTyVarDetails(..),
+ MetaDetails(..), SkolemInfo(..), isMetaTyVar, metaTvRef,
+ tcCmpPred, isClassPred,
+ tcSplitPhiTy, tcSplitPredTy_maybe, tcSplitAppTy_maybe,
tcSplitTyConApp_maybe, tcSplitForAllTys,
- tcGetTyVar, tcIsTyVarTy, tcSplitSigmaTy,
- isUnLiftedType, isIPPred,
-
+ tcIsTyVarTy, tcSplitSigmaTy,
+ isUnLiftedType, isIPPred, isImmutableTyVar,
+ typeKind, isFlexi, isSkolemTyVar,
mkAppTy, mkTyVarTy, mkTyVarTys,
tyVarsOfPred, getClassPredTys_maybe,
-
- liftedTypeKind, openTypeKind, defaultKind, superKind,
- superBoxity, liftedBoxity, typeKind,
tyVarsOfType, tyVarsOfTypes,
- eqKind, isTypeKind,
-
- isFFIArgumentTy, isFFIImportResultTy
+ pprPred, pprTheta, pprClassPred )
+import Kind ( Kind(..), KindVar(..), mkKindVar, isSubKind,
+ isLiftedTypeKind, isArgTypeKind, isOpenTypeKind,
+ liftedTypeKind, defaultKind
)
-import Subst ( Subst, mkTopTyVarSubst, substTy )
-import Class ( classArity, className )
-import TyCon ( TyCon, mkPrimTyCon, isSynTyCon, isUnboxedTupleTyCon,
+import Type ( TvSubst, zipTopTvSubst, substTy )
+import Class ( Class, classArity, className )
+import TyCon ( TyCon, isSynTyCon, isUnboxedTupleTyCon,
tyConArity, tyConName )
-import PrimRep ( PrimRep(VoidRep) )
-import Var ( TyVar, tyVarKind, tyVarName, isTyVar, mkTyVar, isMutTyVar )
+import Var ( TyVar, tyVarKind, tyVarName,
+ mkTyVar, mkTcTyVar, tcTyVarDetails, isTcTyVar )
-- others:
-import TcMonad -- TcType, amongst others
-import TysWiredIn ( voidTy )
-import PrelNames ( cCallableClassKey, cReturnableClassKey, hasKey )
-import ForeignCall ( Safety(..) )
+import TcRnMonad -- TcType, amongst others
import FunDeps ( grow )
-import PprType ( pprPred, pprSourceType, pprTheta, pprClassPred )
-import Name ( Name, NamedThing(..), setNameUnique, mkSysLocalName,
- mkLocalName, mkDerivedTyConOcc
- )
+import Name ( Name, setNameUnique, mkSysTvName )
import VarSet
+import VarEnv
import CmdLineOpts ( dopt, DynFlag(..) )
-import Unique ( Uniquable(..) )
-import SrcLoc ( noSrcLoc )
-import Util ( nOfThem, isSingleton, equalLength )
+import UniqSupply ( uniqsFromSupply )
+import Util ( nOfThem, isSingleton, equalLength, notNull )
import ListSetOps ( removeDups )
+import SrcLoc ( unLoc )
import Outputable
\end{code}
%************************************************************************
\begin{code}
-newTyVar :: Kind -> NF_TcM TcTyVar
-newTyVar kind
- = tcGetUnique `thenNF_Tc` \ uniq ->
- tcNewMutTyVar (mkSysLocalName uniq SLIT("t")) kind VanillaTv
-
-newTyVarTy :: Kind -> NF_TcM TcType
-newTyVarTy kind
- = newTyVar kind `thenNF_Tc` \ tc_tyvar ->
- returnNF_Tc (TyVarTy tc_tyvar)
-
-newHoleTyVarTy :: NF_TcM TcType
- = tcGetUnique `thenNF_Tc` \ uniq ->
- tcNewMutTyVar (mkSysLocalName uniq SLIT("h")) openTypeKind HoleTv `thenNF_Tc` \ tv ->
- returnNF_Tc (TyVarTy tv)
-
-newTyVarTys :: Int -> Kind -> NF_TcM [TcType]
-newTyVarTys n kind = mapNF_Tc newTyVarTy (nOfThem n kind)
-
-newKindVar :: NF_TcM TcKind
-newKindVar
- = tcGetUnique `thenNF_Tc` \ uniq ->
- tcNewMutTyVar (mkSysLocalName uniq SLIT("k")) superKind VanillaTv `thenNF_Tc` \ kv ->
- returnNF_Tc (TyVarTy kv)
-
-newKindVars :: Int -> NF_TcM [TcKind]
-newKindVars n = mapNF_Tc (\ _ -> newKindVar) (nOfThem n ())
-
-newBoxityVar :: NF_TcM TcKind
-newBoxityVar
- = tcGetUnique `thenNF_Tc` \ uniq ->
- tcNewMutTyVar (mkSysLocalName uniq SLIT("bx")) superBoxity VanillaTv `thenNF_Tc` \ kv ->
- returnNF_Tc (TyVarTy kv)
+newMetaTyVar :: Name -> Kind -> MetaDetails -> TcM TyVar
+newMetaTyVar name kind details
+ = do { ref <- newMutVar details ;
+ return (mkTcTyVar name kind (MetaTv ref)) }
+
+readMetaTyVar :: TyVar -> TcM MetaDetails
+readMetaTyVar tyvar = ASSERT2( isMetaTyVar tyvar, ppr tyvar )
+ readMutVar (metaTvRef tyvar)
+
+writeMetaTyVar :: TyVar -> MetaDetails -> TcM ()
+writeMetaTyVar tyvar val = ASSERT2( isMetaTyVar tyvar, ppr tyvar )
+ writeMutVar (metaTvRef tyvar) val
+
+newFlexiTyVar :: Kind -> TcM TcTyVar
+newFlexiTyVar kind
+ = newUnique `thenM` \ uniq ->
+ newMetaTyVar (mkSysTvName uniq FSLIT("t")) kind Flexi
+
+newTyFlexiVarTy :: Kind -> TcM TcType
+newTyFlexiVarTy kind
+ = newFlexiTyVar kind `thenM` \ tc_tyvar ->
+ returnM (TyVarTy tc_tyvar)
+
+newTyFlexiVarTys :: Int -> Kind -> TcM [TcType]
+newTyFlexiVarTys n kind = mappM newTyFlexiVarTy (nOfThem n kind)
+
+newKindVar :: TcM TcKind
+newKindVar = do { uniq <- newUnique
+ ; ref <- newMutVar Nothing
+ ; return (KindVar (mkKindVar uniq ref)) }
+
+newKindVars :: Int -> TcM [TcKind]
+newKindVars n = mappM (\ _ -> newKindVar) (nOfThem n ())
\end{code}
%* *
%************************************************************************
-I don't understand why this is needed
-An old comments says "No need for tcSplitForAllTyM because a type
- variable can't be instantiated to a for-all type"
-But the same is true of rho types!
-
-\begin{code}
-tcSplitRhoTyM :: TcType -> NF_TcM (TcThetaType, TcType)
-tcSplitRhoTyM t
- = go t t []
- where
- -- A type variable is never instantiated to a dictionary type,
- -- so we don't need to do a tcReadVar on the "arg".
- go syn_t (FunTy arg res) ts = case tcSplitPredTy_maybe arg of
- Just pair -> go res res (pair:ts)
- Nothing -> returnNF_Tc (reverse ts, syn_t)
- go syn_t (NoteTy n t) ts = go syn_t t ts
- go syn_t (TyVarTy tv) ts = getTcTyVar tv `thenNF_Tc` \ maybe_ty ->
- case maybe_ty of
- Just ty | not (tcIsTyVarTy ty) -> go syn_t ty ts
- other -> returnNF_Tc (reverse ts, syn_t)
- go syn_t (UsageTy _ t) ts = go syn_t t ts
- go syn_t t ts = returnNF_Tc (reverse ts, syn_t)
-\end{code}
-
+Instantiating a bunch of type variables
-%************************************************************************
-%* *
-\subsection{Type instantiation}
-%* *
-%************************************************************************
+Note [TyVarName]
+~~~~~~~~~~~~~~~~
+Note that we don't change the print-name
+This won't confuse the type checker but there's a chance
+that two different tyvars will print the same way
+in an error message. -dppr-debug will show up the difference
+Better watch out for this. If worst comes to worst, just
+use mkSystemName.
-Instantiating a bunch of type variables
\begin{code}
-tcInstTyVars :: [TyVar]
- -> NF_TcM ([TcTyVar], [TcType], Subst)
-
+-----------------------
+tcInstTyVars :: [TyVar] -> TcM ([TcTyVar], [TcType], TvSubst)
tcInstTyVars tyvars
- = mapNF_Tc tcInstTyVar tyvars `thenNF_Tc` \ tc_tyvars ->
- let
- tys = mkTyVarTys tc_tyvars
- in
- returnNF_Tc (tc_tyvars, tys, mkTopTyVarSubst tyvars tys)
+ = do { tc_tvs <- mappM tcInstTyVar tyvars
+ ; let tys = mkTyVarTys tc_tvs
+ ; returnM (tc_tvs, tys, zipTopTvSubst tyvars tys) }
-- Since the tyvars are freshly made,
-- they cannot possibly be captured by
- -- any existing for-alls. Hence mkTopTyVarSubst
-
-tcInstTyVar tyvar
- = tcGetUnique `thenNF_Tc` \ uniq ->
- let
- name = setNameUnique (tyVarName tyvar) uniq
- -- Note that we don't change the print-name
- -- This won't confuse the type checker but there's a chance
- -- that two different tyvars will print the same way
- -- in an error message. -dppr-debug will show up the difference
- -- Better watch out for this. If worst comes to worst, just
- -- use mkSysLocalName.
- in
- tcNewMutTyVar name (tyVarKind tyvar) VanillaTv
-
-tcInstSigTyVars :: TyVarDetails -> [TyVar] -> NF_TcM [TcTyVar]
-tcInstSigTyVars details tyvars -- Very similar to tcInstTyVar
- = tcGetUniques `thenNF_Tc` \ uniqs ->
- listTc [ ASSERT( not (kind `eqKind` openTypeKind) ) -- Shouldn't happen
- tcNewMutTyVar name kind details
- | (tyvar, uniq) <- tyvars `zip` uniqs,
- let name = setNameUnique (tyVarName tyvar) uniq,
- let kind = tyVarKind tyvar
- ]
-\end{code}
+ -- any existing for-alls. Hence zipTopTvSubst
-@tcInstType@ instantiates the outer-level for-alls of a TcType with
-fresh type variables, splits off the dictionary part, and returns the results.
+tcInstTyVar tyvar -- Freshen the Name of the tyvar
+ = do { uniq <- newUnique
+ ; newMetaTyVar (setNameUnique (tyVarName tyvar) uniq)
+ (tyVarKind tyvar) Flexi }
-\begin{code}
-tcInstType :: TcType -> NF_TcM ([TcTyVar], TcThetaType, TcType)
-tcInstType ty
+tcInstType :: TcType -> TcM ([TcTyVar], TcThetaType, TcType)
+-- tcInstType instantiates the outer-level for-alls of a TcType with
+-- fresh (mutable) type variables, splits off the dictionary part,
+-- and returns the pieces.
+tcInstType ty = tc_inst_type (mappM tcInstTyVar) ty
+
+
+---------------------------------------------
+tcInstSigType :: Name -> [Name] -> TcType -> TcM ([TcTyVar], TcThetaType, TcType)
+-- Instantiate a type with fresh SigSkol variables
+-- See Note [Signature skolems] in TcType.
+--
+-- Tne new type variables have the sane Name as the original *iff* they are scoped.
+-- For scoped tyvars, we don't need a fresh unique, because the renamer has made them
+-- unique, and it's better not to do so because we extend the envt
+-- with them as scoped type variables, and we'd like to avoid spurious
+-- 's = s' bindings in error messages
+--
+-- For non-scoped ones, we *must* instantiate fresh ones:
+--
+-- type T = forall a. [a] -> [a]
+-- f :: T;
+-- f = g where { g :: T; g = <rhs> }
+--
+-- We must not use the same 'a' from the defn of T at both places!!
+
+tcInstSigType id_name scoped_names ty = tc_inst_type (tcInstSigTyVars id_name scoped_names) ty
+
+tcInstSigTyVars :: Name -> [Name] -> [TyVar] -> TcM [TcTyVar]
+tcInstSigTyVars id_name scoped_names tyvars
+ = mapM new_tv tyvars
+ where
+ new_tv tv
+ = do { let name = tyVarName tv
+ ; ref <- newMutVar Flexi
+ ; name' <- if name `elem` scoped_names
+ then return name
+ else do { uniq <- newUnique; return (setNameUnique name uniq) }
+ ; return (mkTcTyVar name' (tyVarKind tv)
+ (SigSkolTv id_name ref)) }
+
+
+---------------------------------------------
+tcSkolType :: SkolemInfo -> TcType -> TcM ([TcTyVar], TcThetaType, TcType)
+-- Instantiate a type with fresh skolem constants
+tcSkolType info ty = tc_inst_type (tcSkolTyVars info) ty
+
+tcSkolTyVars :: SkolemInfo -> [TyVar] -> TcM [TcTyVar]
+tcSkolTyVars info tyvars
+ = do { us <- newUniqueSupply
+ ; return (zipWith skol_tv tyvars (uniqsFromSupply us)) }
+ where
+ skol_tv tv uniq = mkTcTyVar (setNameUnique (tyVarName tv) uniq)
+ (tyVarKind tv) (SkolemTv info)
+ -- See Note [TyVarName]
+
+
+---------------------------------------------
+tcSkolSigType :: SkolemInfo -> Type -> TcM ([TcTyVar], TcThetaType, TcType)
+-- Instantiate a type signature with skolem constants, but
+-- do *not* give them fresh names, because we want the name to
+-- be in the type environment -- it is lexically scoped.
+tcSkolSigType info ty
+ = tc_inst_type (\tvs -> return (tcSkolSigTyVars info tvs)) ty
+
+tcSkolSigTyVars :: SkolemInfo -> [TyVar] -> [TcTyVar]
+tcSkolSigTyVars info tyvars = [ mkTcTyVar (tyVarName tv) (tyVarKind tv) (SkolemTv info)
+ | tv <- tyvars ]
+
+-----------------------
+tc_inst_type :: ([TyVar] -> TcM [TcTyVar]) -- How to instantiate the type variables
+ -> TcType -- Type to instantiate
+ -> TcM ([TcTyVar], TcThetaType, TcType) -- Result
+tc_inst_type inst_tyvars ty
= case tcSplitForAllTys ty of
- ([], rho) -> -- There may be overloading but no type variables;
+ ([], rho) -> let -- There may be overloading despite no type variables;
-- (?x :: Int) => Int -> Int
- let
- (theta, tau) = tcSplitRhoTy rho -- Used to be tcSplitRhoTyM
+ (theta, tau) = tcSplitPhiTy rho
in
- returnNF_Tc ([], theta, tau)
+ return ([], theta, tau)
- (tyvars, rho) -> tcInstTyVars tyvars `thenNF_Tc` \ (tyvars', _, tenv) ->
- let
- (theta, tau) = tcSplitRhoTy (substTy tenv rho) -- Used to be tcSplitRhoTyM
- in
- returnNF_Tc (tyvars', theta, tau)
-\end{code}
+ (tyvars, rho) -> do { tyvars' <- inst_tyvars tyvars
+ ; let tenv = zipTopTvSubst tyvars (mkTyVarTys tyvars')
+ -- Either the tyvars are freshly made, by inst_tyvars,
+ -- or (in the call from tcSkolSigType) any nested foralls
+ -- have different binders. Either way, zipTopTvSubst is ok
+
+ ; let (theta, tau) = tcSplitPhiTy (substTy tenv rho)
+ ; return (tyvars', theta, tau) }
+\end{code}
%************************************************************************
%************************************************************************
\begin{code}
-putTcTyVar :: TcTyVar -> TcType -> NF_TcM TcType
-getTcTyVar :: TcTyVar -> NF_TcM (Maybe TcType)
-\end{code}
-
-Putting is easy:
-
-\begin{code}
-putTcTyVar tyvar ty
- | not (isMutTyVar tyvar)
+putMetaTyVar :: TcTyVar -> TcType -> TcM ()
+#ifndef DEBUG
+putMetaTyVar tyvar ty = writeMetaTyVar tyvar (Indirect ty)
+#else
+putMetaTyVar tyvar ty
+ | not (isMetaTyVar tyvar)
= pprTrace "putTcTyVar" (ppr tyvar) $
- returnNF_Tc ty
+ returnM ()
| otherwise
- = ASSERT( isMutTyVar tyvar )
- UASSERT2( not (isUTy ty), ppr tyvar <+> ppr ty )
- tcWriteMutTyVar tyvar (Just ty) `thenNF_Tc_`
- returnNF_Tc ty
+ = ASSERT( isMetaTyVar tyvar )
+ ASSERT2( k2 `isSubKind` k1, (ppr tyvar <+> ppr k1) $$ (ppr ty <+> ppr k2) )
+ do { ASSERTM( do { details <- readMetaTyVar tyvar; return (isFlexi details) } )
+ ; writeMetaTyVar tyvar (Indirect ty) }
+ where
+ k1 = tyVarKind tyvar
+ k2 = typeKind ty
+#endif
\end{code}
-Getting is more interesting. The easy thing to do is just to read, thus:
-
-\begin{verbatim}
-getTcTyVar tyvar = tcReadMutTyVar tyvar
-\end{verbatim}
-
But it's more fun to short out indirections on the way: If this
version returns a TyVar, then that TyVar is unbound. If it returns
any other type, then there might be bound TyVars embedded inside it.
We return Nothing iff the original box was unbound.
\begin{code}
+data LookupTyVarResult -- The result of a lookupTcTyVar call
+ = DoneTv TcTyVarDetails
+ | IndirectTv Bool TcType
+ -- True => This is a non-wobbly type refinement,
+ -- gotten from GADT match unification
+ -- False => This is a wobbly type,
+ -- gotten from inference unification
+
+lookupTcTyVar :: TcTyVar -> TcM LookupTyVarResult
+-- This function is the ONLY PLACE that we consult the
+-- type refinement carried by the monad
+lookupTcTyVar tyvar
+ = let
+ details = tcTyVarDetails tyvar
+ in
+ case details of
+ MetaTv ref -> lookup_wobbly details ref
+
+ SkolemTv _ -> do { type_reft <- getTypeRefinement
+ ; case lookupVarEnv type_reft tyvar of
+ Just ty -> return (IndirectTv True ty)
+ Nothing -> return (DoneTv details)
+ }
+
+ -- For SigSkolTvs try the refinement, and, failing that
+ -- see if it's been unified to anything. It's a combination
+ -- of SkolemTv and MetaTv
+ SigSkolTv _ ref -> do { type_reft <- getTypeRefinement
+ ; case lookupVarEnv type_reft tyvar of
+ Just ty -> return (IndirectTv True ty)
+ Nothing -> lookup_wobbly details ref
+ }
+
+-- Look up a meta type variable, conditionally consulting
+-- the current type refinement
+condLookupTcTyVar :: Bool -> TcTyVar -> TcM LookupTyVarResult
+condLookupTcTyVar use_refinement tyvar
+ | use_refinement = lookupTcTyVar tyvar
+ | otherwise
+ = case details of
+ MetaTv ref -> lookup_wobbly details ref
+ SkolemTv _ -> return (DoneTv details)
+ SigSkolTv _ ref -> lookup_wobbly details ref
+ where
+ details = tcTyVarDetails tyvar
+
+lookup_wobbly :: TcTyVarDetails -> IORef MetaDetails -> TcM LookupTyVarResult
+lookup_wobbly details ref
+ = do { meta_details <- readMutVar ref
+ ; case meta_details of
+ Indirect ty -> return (IndirectTv False ty)
+ Flexi -> return (DoneTv details)
+ }
+
+{-
+-- gaw 2004 We aren't shorting anything out anymore, at least for now
getTcTyVar tyvar
- | not (isMutTyVar tyvar)
+ | not (isTcTyVar tyvar)
= pprTrace "getTcTyVar" (ppr tyvar) $
- returnNF_Tc (Just (mkTyVarTy tyvar))
+ returnM (Just (mkTyVarTy tyvar))
| otherwise
- = ASSERT2( isMutTyVar tyvar, ppr tyvar )
- tcReadMutTyVar tyvar `thenNF_Tc` \ maybe_ty ->
+ = ASSERT2( isTcTyVar tyvar, ppr tyvar )
+ readMetaTyVar tyvar `thenM` \ maybe_ty ->
case maybe_ty of
- Just ty -> short_out ty `thenNF_Tc` \ ty' ->
- tcWriteMutTyVar tyvar (Just ty') `thenNF_Tc_`
- returnNF_Tc (Just ty')
+ Just ty -> short_out ty `thenM` \ ty' ->
+ writeMetaTyVar tyvar (Just ty') `thenM_`
+ returnM (Just ty')
- Nothing -> returnNF_Tc Nothing
+ Nothing -> returnM Nothing
-short_out :: TcType -> NF_TcM TcType
+short_out :: TcType -> TcM TcType
short_out ty@(TyVarTy tyvar)
- | not (isMutTyVar tyvar)
- = returnNF_Tc ty
+ | not (isTcTyVar tyvar)
+ = returnM ty
| otherwise
- = tcReadMutTyVar tyvar `thenNF_Tc` \ maybe_ty ->
+ = readMetaTyVar tyvar `thenM` \ maybe_ty ->
case maybe_ty of
- Just ty' -> short_out ty' `thenNF_Tc` \ ty' ->
- tcWriteMutTyVar tyvar (Just ty') `thenNF_Tc_`
- returnNF_Tc ty'
+ Just ty' -> short_out ty' `thenM` \ ty' ->
+ writeMetaTyVar tyvar (Just ty') `thenM_`
+ returnM ty'
- other -> returnNF_Tc ty
+ other -> returnM ty
-short_out other_ty = returnNF_Tc other_ty
+short_out other_ty = returnM other_ty
+-}
\end{code}
----------------- Type variables
\begin{code}
-zonkTcTyVars :: [TcTyVar] -> NF_TcM [TcType]
-zonkTcTyVars tyvars = mapNF_Tc zonkTcTyVar tyvars
-
-zonkTcTyVarsAndFV :: [TcTyVar] -> NF_TcM TcTyVarSet
-zonkTcTyVarsAndFV tyvars = mapNF_Tc zonkTcTyVar tyvars `thenNF_Tc` \ tys ->
- returnNF_Tc (tyVarsOfTypes tys)
-
-zonkTcTyVar :: TcTyVar -> NF_TcM TcType
-zonkTcTyVar tyvar = zonkTyVar (\ tv -> returnNF_Tc (TyVarTy tv)) tyvar
-
-zonkTcSigTyVars :: [TcTyVar] -> NF_TcM [TcTyVar]
--- This guy is to zonk the tyvars we're about to feed into tcSimplify
--- Usually this job is done by checkSigTyVars, but in a couple of places
--- that is overkill, so we use this simpler chap
-zonkTcSigTyVars tyvars
- = zonkTcTyVars tyvars `thenNF_Tc` \ tys ->
- returnNF_Tc (map (tcGetTyVar "zonkTcSigTyVars") tys)
+zonkTcTyVars :: [TcTyVar] -> TcM [TcType]
+zonkTcTyVars tyvars = mappM zonkTcTyVar tyvars
+
+zonkTcTyVarsAndFV :: [TcTyVar] -> TcM TcTyVarSet
+zonkTcTyVarsAndFV tyvars = mappM zonkTcTyVar tyvars `thenM` \ tys ->
+ returnM (tyVarsOfTypes tys)
+
+zonkTcTyVar :: TcTyVar -> TcM TcType
+zonkTcTyVar tyvar = zonkTyVar (\ tv -> returnM (TyVarTy tv)) True tyvar
\end{code}
----------------- Types
\begin{code}
-zonkTcType :: TcType -> NF_TcM TcType
-zonkTcType ty = zonkType (\ tv -> returnNF_Tc (TyVarTy tv)) ty
+zonkTcType :: TcType -> TcM TcType
+zonkTcType ty = zonkType (\ tv -> returnM (TyVarTy tv)) True ty
-zonkTcTypes :: [TcType] -> NF_TcM [TcType]
-zonkTcTypes tys = mapNF_Tc zonkTcType tys
+zonkTcTypes :: [TcType] -> TcM [TcType]
+zonkTcTypes tys = mappM zonkTcType tys
-zonkTcClassConstraints cts = mapNF_Tc zonk cts
+zonkTcClassConstraints cts = mappM zonk cts
where zonk (clas, tys)
- = zonkTcTypes tys `thenNF_Tc` \ new_tys ->
- returnNF_Tc (clas, new_tys)
+ = zonkTcTypes tys `thenM` \ new_tys ->
+ returnM (clas, new_tys)
-zonkTcThetaType :: TcThetaType -> NF_TcM TcThetaType
-zonkTcThetaType theta = mapNF_Tc zonkTcPredType theta
+zonkTcThetaType :: TcThetaType -> TcM TcThetaType
+zonkTcThetaType theta = mappM zonkTcPredType theta
-zonkTcPredType :: TcPredType -> NF_TcM TcPredType
+zonkTcPredType :: TcPredType -> TcM TcPredType
zonkTcPredType (ClassP c ts)
- = zonkTcTypes ts `thenNF_Tc` \ new_ts ->
- returnNF_Tc (ClassP c new_ts)
+ = zonkTcTypes ts `thenM` \ new_ts ->
+ returnM (ClassP c new_ts)
zonkTcPredType (IParam n t)
- = zonkTcType t `thenNF_Tc` \ new_t ->
- returnNF_Tc (IParam n new_t)
+ = zonkTcType t `thenM` \ new_t ->
+ returnM (IParam n new_t)
\end{code}
------------------- These ...ToType, ...ToKind versions
are used at the end of type checking
\begin{code}
-zonkKindEnv :: [(Name, TcKind)] -> NF_TcM [(Name, Kind)]
-zonkKindEnv pairs
- = mapNF_Tc zonk_it pairs
- where
- zonk_it (name, tc_kind) = zonkType zonk_unbound_kind_var tc_kind `thenNF_Tc` \ kind ->
- returnNF_Tc (name, kind)
-
- -- When zonking a kind, we want to
- -- zonk a *kind* variable to (Type *)
- -- zonk a *boxity* variable to *
- zonk_unbound_kind_var kv | tyVarKind kv `eqKind` superKind = putTcTyVar kv liftedTypeKind
- | tyVarKind kv `eqKind` superBoxity = putTcTyVar kv liftedBoxity
- | otherwise = pprPanic "zonkKindEnv" (ppr kv)
-
-zonkTcTypeToType :: TcType -> NF_TcM Type
-zonkTcTypeToType ty = zonkType zonk_unbound_tyvar ty
- where
- -- Zonk a mutable but unbound type variable to
- -- Void if it has kind Lifted
- -- :Void otherwise
- -- 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
- | kind `eqKind` liftedTypeKind || kind `eqKind` openTypeKind
- = putTcTyVar tv voidTy -- Just to avoid creating a new tycon in
- -- this vastly common case
- | otherwise
- = putTcTyVar tv (TyConApp (mk_void_tycon tv kind) [])
- where
- kind = tyVarKind tv
-
- mk_void_tycon tv kind -- Make a new TyCon with the same kind as the
- -- type variable tv. Same name too, 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.
- = pprTrace "Urk! Inventing strangely-kinded void TyCon" (ppr tc_name) $
- mkPrimTyCon tc_name kind 0 [] VoidRep
- where
- tc_name = mkLocalName (getUnique tv) (mkDerivedTyConOcc (getOccName tv)) noSrcLoc
-
--- zonkTcTyVarToTyVar is applied to the *binding* occurrence
--- of a type variable, at the *end* of type checking. It changes
--- the *mutable* type variable into an *immutable* one.
---
--- It does this by making an immutable version of tv and binds tv to it.
--- Now any bound occurences of the original type variable will get
--- zonked to the immutable version.
+zonkQuantifiedTyVar :: TcTyVar -> TcM TyVar
+-- zonkQuantifiedTyVar is applied to the a TcTyVar when quantifying over it.
+-- It might be a meta TyVar, in which case we freeze it into an ordinary TyVar.
+-- When we do this, we also default the kind -- see notes with Kind.defaultKind
+-- The meta tyvar is updated to point to the new regular TyVar. Now any
+-- bound occurences of the original type variable will get zonked to
+-- the immutable version.
+--
+-- We leave skolem TyVars alone; they are immutable.
+zonkQuantifiedTyVar tv
+ | isSkolemTyVar tv = return tv
+ -- It might be a skolem type variable,
+ -- for example from a user type signature
+
+ | otherwise -- It's a meta-type-variable
+ = do { details <- readMetaTyVar tv
+
+ -- Create the new, frozen, regular type variable
+ ; let final_kind = defaultKind (tyVarKind tv)
+ final_tv = mkTyVar (tyVarName tv) final_kind
+
+ -- Bind the meta tyvar to the new tyvar
+ ; case details of
+ Indirect ty -> WARN( True, ppr tv $$ ppr ty )
+ return ()
+ -- [Sept 04] I don't think this should happen
+ -- See note [Silly Type Synonym]
+
+ other -> writeMetaTyVar tv (Indirect (mkTyVarTy final_tv))
+
+ -- Return the new tyvar
+ ; return final_tv }
+\end{code}
-zonkTcTyVarToTyVar :: TcTyVar -> NF_TcM TyVar
-zonkTcTyVarToTyVar tv
- = let
- -- Make an immutable version, defaulting
- -- the kind to lifted if necessary
- immut_tv = mkTyVar (tyVarName tv) (defaultKind (tyVarKind tv))
- immut_tv_ty = mkTyVarTy immut_tv
+[Silly Type Synonyms]
- zap tv = putTcTyVar tv immut_tv_ty
- -- Bind the mutable version to the immutable one
- in
- -- If the type variable is mutable, then bind it to immut_tv_ty
- -- so that all other occurrences of the tyvar will get zapped too
- zonkTyVar zap tv `thenNF_Tc` \ ty2 ->
+Consider this:
+ type C u a = u -- Note 'a' unused
- WARN( not (immut_tv_ty `tcEqType` ty2), ppr tv $$ ppr immut_tv $$ ppr ty2 )
+ foo :: (forall a. C u a -> C u a) -> u
+ foo x = ...
- returnNF_Tc immut_tv
-\end{code}
+ bar :: Num u => u
+ bar = foo (\t -> t + t)
+
+* From the (\t -> t+t) we get type {Num d} => d -> d
+ where d is fresh.
+
+* Now unify with type of foo's arg, and we get:
+ {Num (C d a)} => C d a -> C d a
+ where a is fresh.
+
+* Now abstract over the 'a', but float out the Num (C d a) constraint
+ because it does not 'really' mention a. (see Type.tyVarsOfType)
+ The arg to foo becomes
+ /\a -> \t -> t+t
+
+* So we get a dict binding for Num (C d a), which is zonked to give
+ a = ()
+ [Note Sept 04: now that we are zonking quantified type variables
+ on construction, the 'a' will be frozen as a regular tyvar on
+ quantification, so the floated dict will still have type (C d a).
+ Which renders this whole note moot; happily!]
+
+* Then the /\a abstraction has a zonked 'a' in it.
+
+All very silly. I think its harmless to ignore the problem. We'll end up with
+a /\a in the final result but all the occurrences of a will be zonked to ()
%************************************************************************
%************************************************************************
\begin{code}
--- zonkType is used for Kinds as well
-
-- For unbound, mutable tyvars, zonkType uses the function given to it
-- For tyvars bound at a for-all, zonkType zonks them to an immutable
-- type variable and zonks the kind too
-zonkType :: (TcTyVar -> NF_TcM Type) -- What to do with unbound mutable type variables
+zonkType :: (TcTyVar -> TcM Type) -- What to do with unbound mutable type variables
-- see zonkTcType, and zonkTcTypeToType
- -> TcType
- -> NF_TcM Type
-zonkType unbound_var_fn ty
+ -> Bool -- Should we consult the current type refinement?
+ -> TcType
+ -> TcM Type
+zonkType unbound_var_fn rflag ty
= go ty
where
- go (TyConApp tycon tys) = mapNF_Tc go tys `thenNF_Tc` \ tys' ->
- returnNF_Tc (TyConApp tycon tys')
+ go (TyConApp tycon tys) = mappM go tys `thenM` \ tys' ->
+ returnM (TyConApp tycon tys')
- go (NoteTy (SynNote ty1) ty2) = go ty1 `thenNF_Tc` \ ty1' ->
- go ty2 `thenNF_Tc` \ ty2' ->
- returnNF_Tc (NoteTy (SynNote ty1') ty2')
+ go (NoteTy (SynNote ty1) ty2) = go ty1 `thenM` \ ty1' ->
+ go ty2 `thenM` \ ty2' ->
+ returnM (NoteTy (SynNote ty1') ty2')
go (NoteTy (FTVNote _) ty2) = go ty2 -- Discard free-tyvar annotations
- go (SourceTy p) = go_pred p `thenNF_Tc` \ p' ->
- returnNF_Tc (SourceTy p')
+ go (PredTy p) = go_pred p `thenM` \ p' ->
+ returnM (PredTy p')
- go (FunTy arg res) = go arg `thenNF_Tc` \ arg' ->
- go res `thenNF_Tc` \ res' ->
- returnNF_Tc (FunTy arg' res')
+ go (FunTy arg res) = go arg `thenM` \ arg' ->
+ go res `thenM` \ res' ->
+ returnM (FunTy arg' res')
- go (AppTy fun arg) = go fun `thenNF_Tc` \ fun' ->
- go arg `thenNF_Tc` \ arg' ->
- returnNF_Tc (mkAppTy fun' arg')
-
- go (UsageTy u ty) = go u `thenNF_Tc` \ u' ->
- go ty `thenNF_Tc` \ ty' ->
- returnNF_Tc (UsageTy u' ty')
+ go (AppTy fun arg) = go fun `thenM` \ fun' ->
+ go arg `thenM` \ arg' ->
+ returnM (mkAppTy fun' arg')
+ -- NB the mkAppTy; we might have instantiated a
+ -- type variable to a type constructor, so we need
+ -- to pull the TyConApp to the top.
-- The two interesting cases!
- go (TyVarTy tyvar) = zonkTyVar unbound_var_fn tyvar
-
- go (ForAllTy tyvar ty) = zonkTcTyVarToTyVar tyvar `thenNF_Tc` \ tyvar' ->
- go ty `thenNF_Tc` \ ty' ->
- returnNF_Tc (ForAllTy tyvar' ty')
-
- go_pred (ClassP c tys) = mapNF_Tc go tys `thenNF_Tc` \ tys' ->
- returnNF_Tc (ClassP c tys')
- go_pred (NType tc tys) = mapNF_Tc go tys `thenNF_Tc` \ tys' ->
- returnNF_Tc (NType tc tys')
- go_pred (IParam n ty) = go ty `thenNF_Tc` \ ty' ->
- returnNF_Tc (IParam n ty')
-
-zonkTyVar :: (TcTyVar -> NF_TcM Type) -- What to do for an unbound mutable variable
- -> TcTyVar -> NF_TcM TcType
-zonkTyVar unbound_var_fn tyvar
- | not (isMutTyVar tyvar) -- Not a mutable tyvar. This can happen when
- -- zonking a forall type, when the bound type variable
- -- needn't be mutable
- = ASSERT( isTyVar tyvar ) -- Should not be any immutable kind vars
- returnNF_Tc (TyVarTy tyvar)
+ go (TyVarTy tyvar) = zonkTyVar unbound_var_fn rflag tyvar
+
+ go (ForAllTy tyvar ty) = ASSERT( isImmutableTyVar tyvar )
+ go ty `thenM` \ ty' ->
+ returnM (ForAllTy tyvar ty')
+
+ go_pred (ClassP c tys) = mappM go tys `thenM` \ tys' ->
+ returnM (ClassP c tys')
+ go_pred (IParam n ty) = go ty `thenM` \ ty' ->
+ returnM (IParam n ty')
+
+zonkTyVar :: (TcTyVar -> TcM Type) -- What to do for an unbound mutable variable
+ -> Bool -- Consult the type refinement?
+ -> TcTyVar -> TcM TcType
+zonkTyVar unbound_var_fn rflag tyvar
+ | not (isTcTyVar tyvar) -- When zonking (forall a. ...a...), the occurrences of
+ -- the quantified variable 'a' are TyVars not TcTyVars
+ = returnM (TyVarTy tyvar)
| otherwise
- = getTcTyVar tyvar `thenNF_Tc` \ maybe_ty ->
- case maybe_ty of
- Nothing -> unbound_var_fn tyvar -- Mutable and unbound
- Just other_ty -> zonkType unbound_var_fn other_ty -- Bound
+ = condLookupTcTyVar rflag tyvar `thenM` \ details ->
+ case details of
+ -- If b is true, the variable was refined, and therefore it is okay
+ -- to continue refining inside. Otherwise it was wobbly and we should
+ -- not refine further inside.
+ IndirectTv b ty -> zonkType unbound_var_fn b ty -- Bound flexi/refined rigid
+ DoneTv (MetaTv _) -> unbound_var_fn tyvar -- Unbound meta type variable
+ DoneTv other -> return (TyVarTy tyvar) -- Rigid, no zonking necessary
\end{code}
%************************************************************************
%* *
+ Zonking kinds
+%* *
+%************************************************************************
+
+\begin{code}
+readKindVar :: KindVar -> TcM (Maybe TcKind)
+writeKindVar :: KindVar -> TcKind -> TcM ()
+readKindVar (KVar _ ref) = readMutVar ref
+writeKindVar (KVar _ ref) val = writeMutVar ref (Just val)
+
+-------------
+zonkTcKind :: TcKind -> TcM TcKind
+zonkTcKind (FunKind k1 k2) = do { k1' <- zonkTcKind k1
+ ; k2' <- zonkTcKind k2
+ ; returnM (FunKind k1' k2') }
+zonkTcKind k@(KindVar kv) = do { mb_kind <- readKindVar kv
+ ; case mb_kind of
+ Nothing -> returnM k
+ Just k -> zonkTcKind k }
+zonkTcKind other_kind = returnM other_kind
+
+-------------
+zonkTcKindToKind :: TcKind -> TcM Kind
+zonkTcKindToKind (FunKind k1 k2) = do { k1' <- zonkTcKindToKind k1
+ ; k2' <- zonkTcKindToKind k2
+ ; returnM (FunKind k1' k2') }
+
+zonkTcKindToKind (KindVar kv) = do { mb_kind <- readKindVar kv
+ ; case mb_kind of
+ Nothing -> return liftedTypeKind
+ Just k -> zonkTcKindToKind k }
+
+zonkTcKindToKind OpenTypeKind = returnM liftedTypeKind -- An "Open" kind defaults to *
+zonkTcKindToKind other_kind = returnM other_kind
+\end{code}
+
+%************************************************************************
+%* *
\subsection{Checking a user type}
%* *
%************************************************************************
-- f x :: t = ....
| ForSigCtxt Name -- Foreign inport or export signature
| RuleSigCtxt Name -- Signature on a forall'd variable in a RULE
+ | DefaultDeclCtxt -- Types in a default declaration
-- Notes re TySynCtxt
-- We allow type synonyms that aren't types; e.g. type List = []
-- With gla-exts that's right, but for H98 we should complain.
-pprUserTypeCtxt (FunSigCtxt n) = ptext SLIT("the type signature for") <+> quotes (ppr n)
-pprUserTypeCtxt ExprSigCtxt = ptext SLIT("an expression type signature")
-pprUserTypeCtxt (ConArgCtxt c) = ptext SLIT("the type of constructor") <+> quotes (ppr c)
-pprUserTypeCtxt (TySynCtxt c) = ptext SLIT("the RHS of a type synonym declaration") <+> quotes (ppr c)
-pprUserTypeCtxt GenPatCtxt = ptext SLIT("the type pattern of a generic definition")
-pprUserTypeCtxt PatSigCtxt = ptext SLIT("a pattern type signature")
-pprUserTypeCtxt ResSigCtxt = ptext SLIT("a result type signature")
-pprUserTypeCtxt (ForSigCtxt n) = ptext SLIT("the foreign signature for") <+> quotes (ppr n)
-pprUserTypeCtxt (RuleSigCtxt n) = ptext SLIT("the type signature on") <+> quotes (ppr n)
+pprHsSigCtxt :: UserTypeCtxt -> LHsType Name -> SDoc
+pprHsSigCtxt ctxt hs_ty = pprUserTypeCtxt (unLoc hs_ty) ctxt
+
+pprUserTypeCtxt ty (FunSigCtxt n) = sep [ptext SLIT("In the type signature:"), pp_sig n ty]
+pprUserTypeCtxt ty ExprSigCtxt = sep [ptext SLIT("In an expression type signature:"), nest 2 (ppr ty)]
+pprUserTypeCtxt ty (ConArgCtxt c) = sep [ptext SLIT("In the type of the constructor"), pp_sig c ty]
+pprUserTypeCtxt ty (TySynCtxt c) = sep [ptext SLIT("In the RHS of the type synonym") <+> quotes (ppr c) <> comma,
+ nest 2 (ptext SLIT(", namely") <+> ppr ty)]
+pprUserTypeCtxt ty GenPatCtxt = sep [ptext SLIT("In the type pattern of a generic definition:"), nest 2 (ppr ty)]
+pprUserTypeCtxt ty PatSigCtxt = sep [ptext SLIT("In a pattern type signature:"), nest 2 (ppr ty)]
+pprUserTypeCtxt ty ResSigCtxt = sep [ptext SLIT("In a result type signature:"), nest 2 (ppr ty)]
+pprUserTypeCtxt ty (ForSigCtxt n) = sep [ptext SLIT("In the foreign declaration:"), pp_sig n ty]
+pprUserTypeCtxt ty (RuleSigCtxt n) = sep [ptext SLIT("In the type signature:"), pp_sig n ty]
+pprUserTypeCtxt ty DefaultDeclCtxt = sep [ptext SLIT("In a type in a `default' declaration:"), nest 2 (ppr ty)]
+
+pp_sig n ty = nest 2 (ppr n <+> dcolon <+> ppr ty)
\end{code}
\begin{code}
checkValidType :: UserTypeCtxt -> Type -> TcM ()
-- Checks that the type is valid for the given context
checkValidType ctxt ty
- = doptsTc Opt_GlasgowExts `thenNF_Tc` \ gla_exts ->
+ = traceTc (text "checkValidType" <+> ppr ty) `thenM_`
+ doptM Opt_GlasgowExts `thenM` \ gla_exts ->
let
rank | gla_exts = Arbitrary
| otherwise
= case ctxt of -- Haskell 98
GenPatCtxt -> Rank 0
PatSigCtxt -> Rank 0
+ DefaultDeclCtxt-> Rank 0
ResSigCtxt -> Rank 0
TySynCtxt _ -> Rank 0
ExprSigCtxt -> Rank 1
actual_kind = typeKind ty
- actual_kind_is_lifted = actual_kind `eqKind` liftedTypeKind
-
kind_ok = case ctxt of
TySynCtxt _ -> True -- Any kind will do
- GenPatCtxt -> actual_kind_is_lifted
- ForSigCtxt _ -> actual_kind_is_lifted
- other -> isTypeKind actual_kind
+ ResSigCtxt -> isOpenTypeKind actual_kind
+ ExprSigCtxt -> isOpenTypeKind actual_kind
+ GenPatCtxt -> isLiftedTypeKind actual_kind
+ ForSigCtxt _ -> isLiftedTypeKind actual_kind
+ other -> isArgTypeKind actual_kind
+
+ ubx_tup | not gla_exts = UT_NotOk
+ | otherwise = case ctxt of
+ TySynCtxt _ -> UT_Ok
+ ExprSigCtxt -> UT_Ok
+ other -> UT_NotOk
+ -- Unboxed tuples ok in function results,
+ -- but for type synonyms we allow them even at
+ -- top level
in
- tcAddErrCtxt (checkTypeCtxt ctxt ty) $
-
-- Check that the thing has kind Type, and is lifted if necessary
- checkTc kind_ok (kindErr actual_kind) `thenTc_`
+ checkTc kind_ok (kindErr actual_kind) `thenM_`
-- Check the internal validity of the type itself
- check_poly_type rank ty
-
-
-checkTypeCtxt ctxt ty
- = vcat [ptext SLIT("In the type:") <+> ppr_ty ty,
- ptext SLIT("While checking") <+> pprUserTypeCtxt ctxt ]
-
- -- Hack alert. If there are no tyvars, (ppr sigma_ty) will print
- -- something strange like {Eq k} -> k -> k, because there is no
- -- ForAll at the top of the type. Since this is going to the user
- -- we want it to look like a proper Haskell type even then; hence the hack
- --
- -- This shows up in the complaint about
- -- case C a where
- -- op :: Eq a => a -> a
-ppr_ty ty | null forall_tvs && not (null theta) = pprTheta theta <+> ptext SLIT("=>") <+> ppr tau
- | otherwise = ppr ty
- where
- (forall_tvs, theta, tau) = tcSplitSigmaTy ty
+ check_poly_type rank ubx_tup ty `thenM_`
+
+ traceTc (text "checkValidType done" <+> ppr ty)
\end{code}
decRank Arbitrary = Arbitrary
decRank (Rank n) = Rank (n-1)
-check_poly_type :: Rank -> Type -> TcM ()
-check_poly_type (Rank 0) ty
- = check_tau_type (Rank 0) False ty
+----------------------------------------
+data UbxTupFlag = UT_Ok | UT_NotOk
+ -- The "Ok" version means "ok if -fglasgow-exts is on"
+
+----------------------------------------
+check_poly_type :: Rank -> UbxTupFlag -> Type -> TcM ()
+check_poly_type (Rank 0) ubx_tup ty
+ = check_tau_type (Rank 0) ubx_tup ty
-check_poly_type rank ty
+check_poly_type rank ubx_tup ty
= let
(tvs, theta, tau) = tcSplitSigmaTy ty
in
- check_valid_theta SigmaCtxt theta `thenTc_`
- check_tau_type (decRank rank) False tau `thenTc_`
- checkAmbiguity tvs theta tau
+ check_valid_theta SigmaCtxt theta `thenM_`
+ check_tau_type (decRank rank) ubx_tup tau `thenM_`
+ checkFreeness tvs theta `thenM_`
+ checkAmbiguity tvs theta (tyVarsOfType tau)
----------------------------------------
check_arg_type :: Type -> TcM ()
-- NB: unboxed tuples can have polymorphic or unboxed args.
-- This happens in the workers for functions returning
-- product types with polymorphic components.
--- But not in user code
---
--- Question: what about nested unboxed tuples?
--- Currently rejected.
+-- But not in user code.
+-- Anyway, they are dealt with by a special case in check_tau_type
+
check_arg_type ty
- = check_tau_type (Rank 0) False ty `thenTc_`
+ = check_tau_type (Rank 0) UT_NotOk ty `thenM_`
checkTc (not (isUnLiftedType ty)) (unliftedArgErr ty)
----------------------------------------
-check_tau_type :: Rank -> Bool -> Type -> TcM ()
+check_tau_type :: Rank -> UbxTupFlag -> Type -> TcM ()
-- Rank is allowed rank for function args
-- No foralls otherwise
--- Bool is True iff unboxed tuple are allowed here
-
-check_tau_type rank ubx_tup_ok ty@(UsageTy _ _) = failWithTc (usageTyErr ty)
-check_tau_type rank ubx_tup_ok ty@(ForAllTy _ _) = failWithTc (forAllTyErr ty)
-check_tau_type rank ubx_tup_ok (SourceTy sty) = getDOptsTc `thenNF_Tc` \ dflags ->
- check_source_ty dflags TypeCtxt sty
-check_tau_type rank ubx_tup_ok (TyVarTy _) = returnTc ()
-check_tau_type rank ubx_tup_ok ty@(FunTy arg_ty res_ty)
- = check_poly_type rank arg_ty `thenTc_`
- check_tau_type rank True res_ty
-
-check_tau_type rank ubx_tup_ok (AppTy ty1 ty2)
- = check_arg_type ty1 `thenTc_` check_arg_type ty2
-
-check_tau_type rank ubx_tup_ok (NoteTy note ty)
- = check_note note `thenTc_` check_tau_type rank ubx_tup_ok ty
-
-check_tau_type rank ubx_tup_ok ty@(TyConApp tc tys)
- | isSynTyCon tc
- = checkTc syn_arity_ok arity_msg `thenTc_`
- mapTc_ check_arg_type tys
+
+check_tau_type rank ubx_tup ty@(ForAllTy _ _) = failWithTc (forAllTyErr ty)
+check_tau_type rank ubx_tup ty@(FunTy (PredTy _) _) = failWithTc (forAllTyErr ty)
+ -- Reject e.g. (Maybe (?x::Int => Int)), with a decent error message
+
+-- Naked PredTys don't usually show up, but they can as a result of
+-- {-# SPECIALISE instance Ord Char #-}
+-- The Right Thing would be to fix the way that SPECIALISE instance pragmas
+-- are handled, but the quick thing is just to permit PredTys here.
+check_tau_type rank ubx_tup (PredTy sty) = getDOpts `thenM` \ dflags ->
+ check_source_ty dflags TypeCtxt sty
+
+check_tau_type rank ubx_tup (TyVarTy _) = returnM ()
+check_tau_type rank ubx_tup ty@(FunTy arg_ty res_ty)
+ = check_poly_type rank UT_NotOk arg_ty `thenM_`
+ check_tau_type rank UT_Ok res_ty
+
+check_tau_type rank ubx_tup (AppTy ty1 ty2)
+ = check_arg_type ty1 `thenM_` check_arg_type ty2
+
+check_tau_type rank ubx_tup (NoteTy (SynNote syn) ty)
+ -- Synonym notes are built only when the synonym is
+ -- saturated (see Type.mkSynTy)
+ = doptM Opt_GlasgowExts `thenM` \ gla_exts ->
+ (if gla_exts then
+ -- If -fglasgow-exts then don't check the 'note' part.
+ -- This allows us to instantiate a synonym defn with a
+ -- for-all type, or with a partially-applied type synonym.
+ -- e.g. type T a b = a
+ -- type S m = m ()
+ -- f :: S (T Int)
+ -- Here, T is partially applied, so it's illegal in H98.
+ -- But if you expand S first, then T we get just
+ -- f :: Int
+ -- which is fine.
+ returnM ()
+ else
+ -- For H98, do check the un-expanded part
+ check_tau_type rank ubx_tup syn
+ ) `thenM_`
+
+ check_tau_type rank ubx_tup ty
+
+check_tau_type rank ubx_tup (NoteTy other_note ty)
+ = check_tau_type rank ubx_tup ty
+
+check_tau_type rank ubx_tup ty@(TyConApp tc tys)
+ | isSynTyCon tc
+ = -- NB: Type.mkSynTy builds a TyConApp (not a NoteTy) for an unsaturated
+ -- synonym application, leaving it to checkValidType (i.e. right here)
+ -- to find the error
+ checkTc syn_arity_ok arity_msg `thenM_`
+ mappM_ check_arg_type tys
| isUnboxedTupleTyCon tc
- = checkTc ubx_tup_ok ubx_tup_msg `thenTc_`
- mapTc_ (check_tau_type (Rank 0) True) tys -- Args are allowed to be unlifted, or
- -- more unboxed tuples, so can't use check_arg_ty
+ = doptM Opt_GlasgowExts `thenM` \ gla_exts ->
+ checkTc (ubx_tup_ok gla_exts) ubx_tup_msg `thenM_`
+ mappM_ (check_tau_type (Rank 0) UT_Ok) tys
+ -- Args are allowed to be unlifted, or
+ -- more unboxed tuples, so can't use check_arg_ty
| otherwise
- = mapTc_ check_arg_type tys
+ = mappM_ check_arg_type tys
where
+ ubx_tup_ok gla_exts = case ubx_tup of { UT_Ok -> gla_exts; other -> False }
+
syn_arity_ok = tc_arity <= n_args
-- It's OK to have an *over-applied* type synonym
-- data Tree a b = ...
ubx_tup_msg = ubxArgTyErr ty
----------------------------------------
-check_note (FTVNote _) = returnTc ()
-check_note (SynNote ty) = check_tau_type (Rank 0) False ty
-\end{code}
-
-Check for ambiguity
-~~~~~~~~~~~~~~~~~~~
- forall V. P => tau
-is ambiguous if P contains generic variables
-(i.e. one of the Vs) that are not mentioned in tau
-
-However, we need to take account of functional dependencies
-when we speak of 'mentioned in tau'. Example:
- class C a b | a -> b where ...
-Then the type
- forall x y. (C x y) => x
-is not ambiguous because x is mentioned and x determines y
-
-NOTE: In addition, GHC insists that at least one type variable
-in each constraint is in V. So we disallow a type like
- forall a. Eq b => b -> b
-even in a scope where b is in scope.
-This is the is_free test below.
-
-NB; the ambiguity check is only used for *user* types, not for types
-coming from inteface files. The latter can legitimately have
-ambiguous types. Example
-
- class S a where s :: a -> (Int,Int)
- instance S Char where s _ = (1,1)
- f:: S a => [a] -> Int -> (Int,Int)
- f (_::[a]) x = (a*x,b)
- where (a,b) = s (undefined::a)
-
-Here the worker for f gets the type
- fw :: forall a. S a => Int -> (# Int, Int #)
-
-If the list of tv_names is empty, we have a monotype, and then we
-don't need to check for ambiguity either, because the test can't fail
-(see is_ambig).
-
-\begin{code}
-checkAmbiguity :: [TyVar] -> ThetaType -> Type -> TcM ()
-checkAmbiguity forall_tyvars theta tau
- = mapTc_ check_pred theta `thenTc_`
- returnTc ()
- where
- tau_vars = tyVarsOfType tau
- extended_tau_vars = grow theta tau_vars
-
- is_ambig ct_var = (ct_var `elem` forall_tyvars) &&
- not (ct_var `elemVarSet` extended_tau_vars)
- is_free ct_var = not (ct_var `elem` forall_tyvars)
-
- check_pred pred = checkTc (not any_ambig) (ambigErr pred) `thenTc_`
- checkTc (isIPPred pred || not all_free) (freeErr pred)
- where
- ct_vars = varSetElems (tyVarsOfPred pred)
- all_free = all is_free ct_vars
- any_ambig = any is_ambig ct_vars
+forAllTyErr ty = ptext SLIT("Illegal polymorphic or qualified type:") <+> ppr ty
+unliftedArgErr ty = ptext SLIT("Illegal unlifted type argument:") <+> ppr ty
+ubxArgTyErr ty = ptext SLIT("Illegal unboxed tuple type as function argument:") <+> ppr ty
+kindErr kind = ptext SLIT("Expecting an ordinary type, but found a type of kind") <+> ppr kind
\end{code}
-\begin{code}
-ambigErr pred
- = sep [ptext SLIT("Ambiguous constraint") <+> quotes (pprPred pred),
- nest 4 (ptext SLIT("At least one of the forall'd type variables mentioned by the constraint") $$
- ptext SLIT("must be reachable from the type after the '=>'"))]
-
-freeErr pred
- = sep [ptext SLIT("All of the type variables in the constraint") <+> quotes (pprPred pred) <+>
- ptext SLIT("are already in scope"),
- nest 4 (ptext SLIT("At least one must be universally quantified here"))
- ]
-
-forAllTyErr ty = ptext SLIT("Illegal polymorphic type:") <+> ppr_ty ty
-usageTyErr ty = ptext SLIT("Illegal usage type:") <+> ppr_ty ty
-unliftedArgErr ty = ptext SLIT("Illegal unlifted type argument:") <+> ppr_ty ty
-ubxArgTyErr ty = ptext SLIT("Illegal unboxed tuple type as function argument:") <+> ppr_ty ty
-kindErr kind = ptext SLIT("Expecting an ordinary type, but found a type of kind") <+> ppr kind
-\end{code}
%************************************************************************
%* *
%************************************************************************
\begin{code}
+-- Enumerate the contexts in which a "source type", <S>, can occur
+-- Eq a
+-- or ?x::Int
+-- or r <: {x::Int}
+-- or (N a) where N is a newtype
+
data SourceTyCtxt
= ClassSCCtxt Name -- Superclasses of clas
- | SigmaCtxt -- Context of a normal for-all type
- | DataTyCtxt Name -- Context of a data decl
+ -- class <S> => C a where ...
+ | SigmaCtxt -- Theta part of a normal for-all type
+ -- f :: <S> => a -> a
+ | DataTyCtxt Name -- Theta part of a data decl
+ -- data <S> => T a = MkT a
| TypeCtxt -- Source type in an ordinary type
+ -- f :: N a -> N a
| InstThetaCtxt -- Context of an instance decl
+ -- instance <S> => C [a] where ...
| InstHeadCtxt -- Head of an instance decl
+ -- instance ... => Eq a where ...
pprSourceTyCtxt (ClassSCCtxt c) = ptext SLIT("the super-classes of class") <+> quotes (ppr c)
pprSourceTyCtxt SigmaCtxt = ptext SLIT("the context of a polymorphic type")
\begin{code}
checkValidTheta :: SourceTyCtxt -> ThetaType -> TcM ()
checkValidTheta ctxt theta
- = tcAddErrCtxt (checkThetaCtxt ctxt theta) (check_valid_theta ctxt theta)
+ = addErrCtxt (checkThetaCtxt ctxt theta) (check_valid_theta ctxt theta)
-------------------------
check_valid_theta ctxt []
- = returnTc ()
+ = returnM ()
check_valid_theta ctxt theta
- = getDOptsTc `thenNF_Tc` \ dflags ->
- warnTc (not (null dups)) (dupPredWarn dups) `thenNF_Tc_`
- mapTc_ (check_source_ty dflags ctxt) theta
+ = getDOpts `thenM` \ dflags ->
+ warnTc (notNull dups) (dupPredWarn dups) `thenM_`
+ -- Actually, in instance decls and type signatures,
+ -- duplicate constraints are eliminated by TcHsType.hoistForAllTys,
+ -- so this error can only fire for the context of a class or
+ -- data type decl.
+ mappM_ (check_source_ty dflags ctxt) theta
where
(_,dups) = removeDups tcCmpPred theta
-------------------------
check_source_ty dflags ctxt pred@(ClassP cls tys)
= -- Class predicates are valid in all contexts
- mapTc_ check_arg_type tys `thenTc_`
- checkTc (arity == n_tys) arity_err `thenTc_`
- checkTc (all tyvar_head tys || arby_preds_ok) (predTyVarErr pred)
+ checkTc (arity == n_tys) arity_err `thenM_`
+
+ -- Check the form of the argument types
+ mappM_ check_arg_type tys `thenM_`
+ checkTc (check_class_pred_tys dflags ctxt tys)
+ (predTyVarErr pred $$ how_to_allow)
where
class_name = className cls
n_tys = length tys
arity_err = arityErr "Class" class_name arity n_tys
- arby_preds_ok = case ctxt of
- InstHeadCtxt -> True -- We check for instance-head formation
- -- in checkValidInstHead
- InstThetaCtxt -> dopt Opt_AllowUndecidableInstances dflags
- other -> dopt Opt_GlasgowExts dflags
+ how_to_allow = case ctxt of
+ InstHeadCtxt -> empty -- Should not happen
+ InstThetaCtxt -> parens undecidableMsg
+ other -> parens (ptext SLIT("Use -fglasgow-exts to permit this"))
check_source_ty dflags SigmaCtxt (IParam _ ty) = check_arg_type ty
-- Implicit parameters only allows in type
-- constraint Foo [Int] might come out of e,and applying the
-- instance decl would show up two uses of ?x.
-check_source_ty dflags TypeCtxt (NType tc tys) = mapTc_ check_arg_type tys
-
-- Catch-all
check_source_ty dflags ctxt sty = failWithTc (badSourceTyErr sty)
-------------------------
+check_class_pred_tys dflags ctxt tys
+ = case ctxt of
+ InstHeadCtxt -> True -- We check for instance-head
+ -- formation in checkValidInstHead
+ InstThetaCtxt -> undecidable_ok || all tcIsTyVarTy tys
+ other -> gla_exts || all tyvar_head tys
+ where
+ undecidable_ok = dopt Opt_AllowUndecidableInstances dflags
+ gla_exts = dopt Opt_GlasgowExts dflags
+
+-------------------------
tyvar_head ty -- Haskell 98 allows predicates of form
| tcIsTyVarTy ty = True -- C (a ty1 .. tyn)
| otherwise -- where a is a type variable
Nothing -> False
\end{code}
+Check for ambiguity
+~~~~~~~~~~~~~~~~~~~
+ forall V. P => tau
+is ambiguous if P contains generic variables
+(i.e. one of the Vs) that are not mentioned in tau
+
+However, we need to take account of functional dependencies
+when we speak of 'mentioned in tau'. Example:
+ class C a b | a -> b where ...
+Then the type
+ forall x y. (C x y) => x
+is not ambiguous because x is mentioned and x determines y
+
+NB; the ambiguity check is only used for *user* types, not for types
+coming from inteface files. The latter can legitimately have
+ambiguous types. Example
+
+ class S a where s :: a -> (Int,Int)
+ instance S Char where s _ = (1,1)
+ f:: S a => [a] -> Int -> (Int,Int)
+ f (_::[a]) x = (a*x,b)
+ where (a,b) = s (undefined::a)
+
+Here the worker for f gets the type
+ fw :: forall a. S a => Int -> (# Int, Int #)
+
+If the list of tv_names is empty, we have a monotype, and then we
+don't need to check for ambiguity either, because the test can't fail
+(see is_ambig).
+
+\begin{code}
+checkAmbiguity :: [TyVar] -> ThetaType -> TyVarSet -> TcM ()
+checkAmbiguity forall_tyvars theta tau_tyvars
+ = mappM_ complain (filter is_ambig theta)
+ where
+ complain pred = addErrTc (ambigErr pred)
+ extended_tau_vars = grow theta tau_tyvars
+
+ -- Only a *class* predicate can give rise to ambiguity
+ -- An *implicit parameter* cannot. For example:
+ -- foo :: (?x :: [a]) => Int
+ -- foo = length ?x
+ -- is fine. The call site will suppply a particular 'x'
+ is_ambig pred = isClassPred pred &&
+ any ambig_var (varSetElems (tyVarsOfPred pred))
+
+ ambig_var ct_var = (ct_var `elem` forall_tyvars) &&
+ not (ct_var `elemVarSet` extended_tau_vars)
+
+ambigErr pred
+ = sep [ptext SLIT("Ambiguous constraint") <+> quotes (pprPred pred),
+ nest 4 (ptext SLIT("At least one of the forall'd type variables mentioned by the constraint") $$
+ ptext SLIT("must be reachable from the type after the '=>'"))]
+\end{code}
+
+In addition, GHC insists that at least one type variable
+in each constraint is in V. So we disallow a type like
+ forall a. Eq b => b -> b
+even in a scope where b is in scope.
+
\begin{code}
-badSourceTyErr sty = ptext SLIT("Illegal constraint") <+> pprSourceType sty
-predTyVarErr pred = ptext SLIT("Non-type variables in constraint:") <+> pprPred pred
-dupPredWarn dups = ptext SLIT("Duplicate constraint(s):") <+> pprWithCommas pprPred (map head dups)
+checkFreeness forall_tyvars theta
+ = mappM_ complain (filter is_free theta)
+ where
+ is_free pred = not (isIPPred pred)
+ && not (any bound_var (varSetElems (tyVarsOfPred pred)))
+ bound_var ct_var = ct_var `elem` forall_tyvars
+ complain pred = addErrTc (freeErr pred)
+
+freeErr pred
+ = sep [ptext SLIT("All of the type variables in the constraint") <+> quotes (pprPred pred) <+>
+ ptext SLIT("are already in scope"),
+ nest 4 (ptext SLIT("(at least one must be universally quantified here)"))
+ ]
+\end{code}
+\begin{code}
checkThetaCtxt ctxt theta
= vcat [ptext SLIT("In the context:") <+> pprTheta theta,
ptext SLIT("While checking") <+> pprSourceTyCtxt ctxt ]
+
+badSourceTyErr sty = ptext SLIT("Illegal constraint") <+> pprPred sty
+predTyVarErr pred = ptext SLIT("Non-type variables in constraint:") <+> pprPred pred
+dupPredWarn dups = ptext SLIT("Duplicate constraint(s):") <+> pprWithCommas pprPred (map head dups)
+
+arityErr kind name n m
+ = hsep [ text kind, quotes (ppr name), ptext SLIT("should have"),
+ n_arguments <> comma, text "but has been given", int m]
+ where
+ n_arguments | n == 0 = ptext SLIT("no arguments")
+ | n == 1 = ptext SLIT("1 argument")
+ | True = hsep [int n, ptext SLIT("arguments")]
\end{code}
We can also have instances for functions: @instance Foo (a -> b) ...@.
\begin{code}
-checkValidInstHead :: Type -> TcM ()
+checkValidInstHead :: Type -> TcM (Class, [TcType])
checkValidInstHead ty -- Should be a source type
= case tcSplitPredTy_maybe ty of {
Nothing -> failWithTc (instTypeErr (pprPred pred) empty) ;
Just (clas,tys) ->
- getDOptsTc `thenNF_Tc` \ dflags ->
- mapTc_ check_arg_type tys `thenTc_`
- check_inst_head dflags clas tys
+ getDOpts `thenM` \ dflags ->
+ mappM_ check_arg_type tys `thenM_`
+ check_inst_head dflags clas tys `thenM_`
+ returnM (clas, tys)
}}
check_inst_head dflags clas tys
- | -- CCALL CHECK
- -- A user declaration of a CCallable/CReturnable instance
- -- must be for a "boxed primitive" type.
- (clas `hasKey` cCallableClassKey
- && not (ccallable_type first_ty))
- || (clas `hasKey` cReturnableClassKey
- && not (creturnable_type first_ty))
- = failWithTc (nonBoxedPrimCCallErr clas first_ty)
-
-- If GlasgowExts then check at least one isn't a type variable
| dopt Opt_GlasgowExts dflags
= check_tyvars dflags clas tys
all tcIsTyVarTy arg_tys, -- Applied to type variables
equalLength (varSetElems (tyVarsOfTypes arg_tys)) arg_tys
-- This last condition checks that all the type variables are distinct
- = returnTc ()
+ = returnM ()
| otherwise
= failWithTc (instTypeErr (pprClassPred clas tys) head_shape_msg)
where
(first_ty : _) = tys
- ccallable_type ty = isFFIArgumentTy dflags PlayRisky ty
- creturnable_type ty = isFFIImportResultTy dflags ty
-
head_shape_msg = parens (text "The instance type must be of form (T a b c)" $$
text "where T is not a synonym, and a,b,c are distinct type variables")
check_tyvars dflags clas tys
-- Check that at least one isn't a type variable
-- unless -fallow-undecideable-instances
- | dopt Opt_AllowUndecidableInstances dflags = returnTc ()
- | not (all tcIsTyVarTy tys) = returnTc ()
+ | dopt Opt_AllowUndecidableInstances dflags = returnM ()
+ | not (all tcIsTyVarTy tys) = returnM ()
| otherwise = failWithTc (instTypeErr (pprClassPred clas tys) msg)
where
msg = parens (ptext SLIT("There must be at least one non-type-variable in the instance head")
- $$ ptext SLIT("Use -fallow-undecidable-instances to lift this restriction"))
+ $$ undecidableMsg)
+
+undecidableMsg = ptext SLIT("Use -fallow-undecidable-instances to permit this")
\end{code}
\begin{code}
instTypeErr pp_ty msg
= sep [ptext SLIT("Illegal instance declaration for") <+> quotes pp_ty,
nest 4 msg]
-
-nonBoxedPrimCCallErr clas inst_ty
- = hang (ptext SLIT("Unacceptable instance type for ccall-ish class"))
- 4 (pprClassPred clas [inst_ty])
\end{code}
-
-
projects / ghc-hetmet.git / blobdiff