\begin{code}
module TcMType (
- TcTyVar, TcKind, TcType, TcTauType, TcThetaType, TcRhoType, TcTyVarSet,
+ TcTyVar, TcKind, TcType, TcTauType, TcThetaType, TcTyVarSet,
--------------------------------
-- Creating new mutable type variables
- newTyVar,
- newTyVarTy, -- Kind -> NF_TcM TcType
- newTyVarTys, -- Int -> Kind -> NF_TcM [TcType]
- newKindVar, newKindVars, newBoxityVar,
+ newTyVar, newSigTyVar,
+ newTyVarTy, -- Kind -> TcM TcType
+ newTyVarTys, -- Int -> Kind -> TcM [TcType]
+ newKindVar, newKindVars, newOpenTypeKind,
+ putTcTyVar, getTcTyVar,
+ newMutTyVar, readMutTyVar, writeMutTyVar,
--------------------------------
-- Instantiation
- tcInstTyVar, tcInstTyVars,
- tcInstSigVars, tcInstType,
- tcSplitRhoTyM,
+ tcInstTyVar, tcInstTyVars, tcInstType,
--------------------------------
-- Checking type validity
Rank, UserTypeCtxt(..), checkValidType, pprUserTypeCtxt,
SourceTyCtxt(..), checkValidTheta,
- checkValidInstHead, instTypeErr,
-
- --------------------------------
- -- Unification
- unifyTauTy, unifyTauTyList, unifyTauTyLists,
- unifyFunTy, unifyListTy, unifyTupleTy,
- unifyKind, unifyKinds, unifyOpenTypeKind,
+ checkValidTyCon, checkValidClass,
+ checkValidInstHead, instTypeErr, checkAmbiguity,
+ arityErr,
--------------------------------
-- Zonking
- zonkTcTyVar, zonkTcTyVars, zonkTcTyVarsAndFV, zonkTcSigTyVars,
+ zonkType,
+ zonkTcTyVar, zonkTcTyVars, zonkTcTyVarsAndFV,
zonkTcType, zonkTcTypes, zonkTcClassConstraints, zonkTcThetaType,
- zonkTcPredType, zonkTcTypeToType, zonkTcTyVarToTyVar, zonkKindEnv,
+ zonkTcPredType, zonkTcTyVarToTyVar, zonkKindEnv,
) where
-- friends:
import TypeRep ( Type(..), SourceType(..), TyNote(..), -- Friend; can see representation
- Kind, TauType, ThetaType,
- openKindCon, typeCon
+ Kind, ThetaType, typeCon
)
-import TcType ( tcEqType, tcCmpPred,
- tcSplitRhoTy, tcSplitPredTy_maybe, tcSplitAppTy_maybe,
- tcSplitTyConApp_maybe, tcSplitFunTy_maybe, tcSplitForAllTys,
- tcGetTyVar, tcIsTyVarTy, tcSplitSigmaTy, isUnLiftedType, isIPPred,
-
- mkAppTy, mkTyVarTy, mkTyVarTys, mkFunTy, mkTyConApp,
+import TcType ( TcType, TcThetaType, TcTauType, TcPredType,
+ TcTyVarSet, TcKind, TcTyVar, TyVarDetails(..),
+ tcEqType, tcCmpPred, isClassPred,
+ tcSplitPhiTy, tcSplitPredTy_maybe, tcSplitAppTy_maybe,
+ tcSplitTyConApp_maybe, tcSplitForAllTys,
+ tcIsTyVarTy, tcSplitSigmaTy, mkTyConApp,
+ isUnLiftedType, isIPPred, isTyVarTy,
+
+ mkAppTy, mkTyVarTy, mkTyVarTys,
tyVarsOfPred, getClassPredTys_maybe,
- liftedTypeKind, unliftedTypeKind, openTypeKind, defaultKind, superKind,
- superBoxity, liftedBoxity, hasMoreBoxityInfo, typeKind,
- tyVarsOfType, tyVarsOfTypes, tidyOpenType, tidyOpenTypes, tidyOpenTyVar,
- eqKind, isTypeKind,
-
+ liftedTypeKind, openTypeKind, defaultKind, superKind,
+ superBoxity, liftedBoxity, typeKind,
+ tyVarsOfType, tyVarsOfTypes,
+ eqKind, isTypeKind,
isFFIArgumentTy, isFFIImportResultTy
)
import Subst ( Subst, mkTopTyVarSubst, substTy )
-import Class ( classArity, className )
-import TyCon ( TyCon, mkPrimTyCon, isSynTyCon, isUnboxedTupleTyCon,
- isTupleTyCon, tyConArity, tupleTyConBoxity, tyConName )
-import PrimRep ( PrimRep(VoidRep) )
-import Var ( TyVar, varName, tyVarKind, tyVarName, isTyVar, mkTyVar,
- isMutTyVar, isSigTyVar )
+import Class ( Class, DefMeth(..), classArity, className, classBigSig )
+import TyCon ( TyCon, isSynTyCon, isUnboxedTupleTyCon,
+ tyConArity, tyConName, tyConTheta,
+ getSynTyConDefn, tyConDataCons )
+import DataCon ( DataCon, dataConWrapId, dataConName, dataConSig, dataConFieldLabels )
+import FieldLabel ( fieldLabelName, fieldLabelType )
+import Var ( TyVar, idType, idName, tyVarKind, tyVarName, isTyVar,
+ mkTyVar, mkMutTyVar, isMutTyVar, mutTyVarRef )
-- others:
-import TcMonad -- TcType, amongst others
-import TysWiredIn ( voidTy, listTyCon, mkListTy, mkTupleTy )
+import Generics ( validGenericMethodType )
+import TcRnMonad -- TcType, amongst others
import PrelNames ( cCallableClassKey, cReturnableClassKey, hasKey )
import ForeignCall ( Safety(..) )
import FunDeps ( grow )
import PprType ( pprPred, pprSourceType, pprTheta, pprClassPred )
-import Name ( Name, NamedThing(..), setNameUnique, mkSysLocalName,
- mkLocalName, mkDerivedTyConOcc, isSystemName
- )
+import Name ( Name, setNameUnique, mkSystemTvNameEncoded )
import VarSet
-import BasicTypes ( Boxity, Arity, isBoxed )
import CmdLineOpts ( dopt, DynFlag(..) )
-import Unique ( Uniquable(..) )
-import SrcLoc ( noSrcLoc )
-import Util ( nOfThem )
-import ListSetOps ( removeDups )
+import Util ( nOfThem, isSingleton, equalLength, notNull, lengthExceeds )
+import ListSetOps ( equivClasses, removeDups )
import Outputable
\end{code}
%************************************************************************
\begin{code}
-newTyVar :: Kind -> NF_TcM TcTyVar
-newTyVar kind
- = tcGetUnique `thenNF_Tc` \ uniq ->
- tcNewMutTyVar (mkSysLocalName uniq SLIT("t")) kind
+newMutTyVar :: Name -> Kind -> TyVarDetails -> TcM TyVar
+newMutTyVar name kind details
+ = do { ref <- newMutVar Nothing ;
+ return (mkMutTyVar name kind details ref) }
-newTyVarTy :: Kind -> NF_TcM TcType
-newTyVarTy kind
- = newTyVar kind `thenNF_Tc` \ tc_tyvar ->
- returnNF_Tc (TyVarTy tc_tyvar)
+readMutTyVar :: TyVar -> TcM (Maybe Type)
+readMutTyVar tyvar = readMutVar (mutTyVarRef tyvar)
-newTyVarTys :: Int -> Kind -> NF_TcM [TcType]
-newTyVarTys n kind = mapNF_Tc newTyVarTy (nOfThem n kind)
+writeMutTyVar :: TyVar -> Maybe Type -> TcM ()
+writeMutTyVar tyvar val = writeMutVar (mutTyVarRef tyvar) val
-newKindVar :: NF_TcM TcKind
-newKindVar
- = tcGetUnique `thenNF_Tc` \ uniq ->
- tcNewMutTyVar (mkSysLocalName uniq SLIT("k")) superKind `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 `thenNF_Tc` \ kv ->
- returnNF_Tc (TyVarTy kv)
-\end{code}
+newTyVar :: Kind -> TcM TcTyVar
+newTyVar kind
+ = newUnique `thenM` \ uniq ->
+ newMutTyVar (mkSystemTvNameEncoded uniq FSLIT("t")) kind VanillaTv
+newSigTyVar :: Kind -> TcM TcTyVar
+newSigTyVar kind
+ = newUnique `thenM` \ uniq ->
+ newMutTyVar (mkSystemTvNameEncoded uniq FSLIT("s")) kind SigTv
-%************************************************************************
-%* *
-\subsection{Type instantiation}
-%* *
-%************************************************************************
+newTyVarTy :: Kind -> TcM TcType
+newTyVarTy kind
+ = newTyVar kind `thenM` \ tc_tyvar ->
+ returnM (TyVarTy tc_tyvar)
-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!
+newTyVarTys :: Int -> Kind -> TcM [TcType]
+newTyVarTys n kind = mappM newTyVarTy (nOfThem n kind)
-\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)
+newKindVar :: TcM TcKind
+newKindVar
+ = newUnique `thenM` \ uniq ->
+ newMutTyVar (mkSystemTvNameEncoded uniq FSLIT("k")) superKind VanillaTv `thenM` \ kv ->
+ returnM (TyVarTy kv)
+
+newKindVars :: Int -> TcM [TcKind]
+newKindVars n = mappM (\ _ -> newKindVar) (nOfThem n ())
+
+newOpenTypeKind :: TcM TcKind -- Returns the kind (Type bx), where bx is fresh
+newOpenTypeKind
+ = newUnique `thenM` \ uniq ->
+ newMutTyVar (mkSystemTvNameEncoded uniq FSLIT("bx")) superBoxity VanillaTv `thenM` \ kv ->
+ returnM (mkTyConApp typeCon [TyVarTy kv])
\end{code}
Instantiating a bunch of type variables
\begin{code}
-tcInstTyVars :: [TyVar]
- -> NF_TcM ([TcTyVar], [TcType], Subst)
+tcInstTyVars :: TyVarDetails -> [TyVar]
+ -> TcM ([TcTyVar], [TcType], Subst)
-tcInstTyVars tyvars
- = mapNF_Tc tcInstTyVar tyvars `thenNF_Tc` \ tc_tyvars ->
+tcInstTyVars tv_details tyvars
+ = mappM (tcInstTyVar tv_details) tyvars `thenM` \ tc_tyvars ->
let
tys = mkTyVarTys tc_tyvars
in
- returnNF_Tc (tc_tyvars, tys, mkTopTyVarSubst tyvars tys)
+ returnM (tc_tyvars, tys, mkTopTyVarSubst 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 ->
+tcInstTyVar tv_details tyvar
+ = newUnique `thenM` \ uniq ->
let
name = setNameUnique (tyVarName tyvar) uniq
-- Note that we don't change the print-name
-- 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.
+ -- use mkSystemName.
in
- tcNewMutTyVar name (tyVarKind tyvar)
-
-tcInstSigVars tyvars -- Very similar to tcInstTyVar
- = tcGetUniques `thenNF_Tc` \ uniqs ->
- listTc [ ASSERT( not (kind `eqKind` openTypeKind) ) -- Shouldn't happen
- tcNewSigTyVar name kind
- | (tyvar, uniq) <- tyvars `zip` uniqs,
- let name = setNameUnique (tyVarName tyvar) uniq,
- let kind = tyVarKind tyvar
- ]
-\end{code}
+ newMutTyVar name (tyVarKind tyvar) tv_details
-@tcInstType@ instantiates the outer-level for-alls of a TcType with
-fresh type variables, splits off the dictionary part, and returns the results.
-
-\begin{code}
-tcInstType :: TcType -> NF_TcM ([TcTyVar], TcThetaType, TcType)
-tcInstType ty
+tcInstType :: TyVarDetails -> 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 tv_details ty
= case tcSplitForAllTys ty of
- ([], rho) -> -- There may be overloading but no type variables;
+ ([], rho) -> -- 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)
+ returnM ([], theta, tau)
- (tyvars, rho) -> tcInstTyVars tyvars `thenNF_Tc` \ (tyvars', _, tenv) ->
+ (tyvars, rho) -> tcInstTyVars tv_details tyvars `thenM` \ (tyvars', _, tenv) ->
let
- (theta, tau) = tcSplitRhoTy (substTy tenv rho) -- Used to be tcSplitRhoTyM
+ (theta, tau) = tcSplitPhiTy (substTy tenv rho)
in
- returnNF_Tc (tyvars', theta, tau)
+ returnM (tyvars', theta, tau)
\end{code}
-
%************************************************************************
%* *
\subsection{Putting and getting mutable type variables}
%************************************************************************
\begin{code}
-putTcTyVar :: TcTyVar -> TcType -> NF_TcM TcType
-getTcTyVar :: TcTyVar -> NF_TcM (Maybe TcType)
+putTcTyVar :: TcTyVar -> TcType -> TcM TcType
+getTcTyVar :: TcTyVar -> TcM (Maybe TcType)
\end{code}
Putting is easy:
putTcTyVar tyvar ty
| not (isMutTyVar tyvar)
= pprTrace "putTcTyVar" (ppr tyvar) $
- returnNF_Tc ty
+ returnM ty
| otherwise
= ASSERT( isMutTyVar tyvar )
- UASSERT2( not (isUTy ty), ppr tyvar <+> ppr ty )
- tcWriteMutTyVar tyvar (Just ty) `thenNF_Tc_`
- returnNF_Tc ty
+ writeMutTyVar tyvar (Just ty) `thenM_`
+ returnM ty
\end{code}
Getting is more interesting. The easy thing to do is just to read, thus:
\begin{verbatim}
-getTcTyVar tyvar = tcReadMutTyVar tyvar
+getTcTyVar tyvar = readMutTyVar tyvar
\end{verbatim}
But it's more fun to short out indirections on the way: If this
getTcTyVar tyvar
| not (isMutTyVar 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 ->
+ readMutTyVar 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' ->
+ writeMutTyVar 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
+ = returnM ty
| otherwise
- = tcReadMutTyVar tyvar `thenNF_Tc` \ maybe_ty ->
+ = readMutTyVar 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' ->
+ writeMutTyVar 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)) 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)) 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)
-
-zonkTcThetaType :: TcThetaType -> NF_TcM TcThetaType
-zonkTcThetaType theta = mapNF_Tc zonkTcPredType theta
-
-zonkTcPredType :: TcPredType -> NF_TcM TcPredType
-zonkTcPredType (ClassP c ts) =
- zonkTcTypes ts `thenNF_Tc` \ new_ts ->
- returnNF_Tc (ClassP c new_ts)
-zonkTcPredType (IParam n t) =
- zonkTcType t `thenNF_Tc` \ new_t ->
- returnNF_Tc (IParam n new_t)
+ = zonkTcTypes tys `thenM` \ new_tys ->
+ returnM (clas, new_tys)
+
+zonkTcThetaType :: TcThetaType -> TcM TcThetaType
+zonkTcThetaType theta = mappM zonkTcPredType theta
+
+zonkTcPredType :: TcPredType -> TcM TcPredType
+zonkTcPredType (ClassP c ts)
+ = zonkTcTypes ts `thenM` \ new_ts ->
+ returnM (ClassP c new_ts)
+zonkTcPredType (IParam n 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 :: [(Name, TcKind)] -> TcM [(Name, Kind)]
zonkKindEnv pairs
- = mapNF_Tc zonk_it pairs
+ = mappM zonk_it pairs
where
- zonk_it (name, tc_kind) = zonkType zonk_unbound_kind_var tc_kind `thenNF_Tc` \ kind ->
- returnNF_Tc (name, kind)
+ zonk_it (name, tc_kind) = zonkType zonk_unbound_kind_var tc_kind `thenM` \ kind ->
+ returnM (name, kind)
-- When zonking a kind, we want to
-- zonk a *kind* variable to (Type *)
| 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.
-- Now any bound occurences of the original type variable will get
-- zonked to the immutable version.
-zonkTcTyVarToTyVar :: TcTyVar -> NF_TcM TyVar
+zonkTcTyVarToTyVar :: TcTyVar -> TcM TyVar
zonkTcTyVarToTyVar tv
= let
-- Make an immutable version, defaulting
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 ->
+ zonkTyVar zap tv `thenM` \ ty2 ->
+ -- This warning shows up if the allegedly-unbound tyvar is
+ -- already bound to something. It can actually happen, and
+ -- in a harmless way (see [Silly Type Synonyms] below) so
+ -- it's only a warning
WARN( not (immut_tv_ty `tcEqType` ty2), ppr tv $$ ppr immut_tv $$ ppr ty2 )
- returnNF_Tc immut_tv
+ returnM immut_tv
\end{code}
+[Silly Type Synonyms]
+
+Consider this:
+ type C u a = u -- Note 'a' unused
+
+ foo :: (forall a. C u a -> C u a) -> u
+ foo x = ...
+
+ 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 = ()
+
+* Then the /\a abstraction has a zonked 'a' in it.
+
+All very silly. I think its harmless to ignore the problem.
+
%************************************************************************
%* *
-- 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
+ -> TcM Type
zonkType unbound_var_fn 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 (SourceTy p) = go_pred p `thenM` \ p' ->
+ returnM (SourceTy 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 (ForAllTy tyvar ty) = zonkTcTyVarToTyVar tyvar `thenM` \ tyvar' ->
+ go ty `thenM` \ ty' ->
+ returnM (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')
+ go_pred (ClassP c tys) = mappM go tys `thenM` \ tys' ->
+ returnM (ClassP c tys')
+ go_pred (NType tc tys) = mappM go tys `thenM` \ tys' ->
+ returnM (NType tc tys')
+ go_pred (IParam n ty) = go ty `thenM` \ ty' ->
+ returnM (IParam n ty')
-zonkTyVar :: (TcTyVar -> NF_TcM Type) -- What to do for an unbound mutable variable
- -> TcTyVar -> NF_TcM TcType
+zonkTyVar :: (TcTyVar -> TcM Type) -- What to do for an unbound mutable variable
+ -> TcTyVar -> 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)
+ returnM (TyVarTy tyvar)
| otherwise
- = getTcTyVar tyvar `thenNF_Tc` \ maybe_ty ->
+ = getTcTyVar tyvar `thenM` \ maybe_ty ->
case maybe_ty of
Nothing -> unbound_var_fn tyvar -- Mutable and unbound
Just other_ty -> zonkType unbound_var_fn other_ty -- Bound
checkValidType :: UserTypeCtxt -> Type -> TcM ()
-- Checks that the type is valid for the given context
checkValidType ctxt ty
- = doptsTc Opt_GlasgowExts `thenNF_Tc` \ gla_exts ->
+ = doptM Opt_GlasgowExts `thenM` \ gla_exts ->
let
- rank = case ctxt of
- GenPatCtxt -> 0
- PatSigCtxt -> 0
- ResSigCtxt -> 0
- ExprSigCtxt -> 1
- FunSigCtxt _ | gla_exts -> 2
- | otherwise -> 1
- ConArgCtxt _ | gla_exts -> 2 -- We are given the type of the entire
- | otherwise -> 1 -- constructor; hence rank 1 is ok
- TySynCtxt _ | gla_exts -> 1
- | otherwise -> 0
- ForSigCtxt _ -> 1
- RuleSigCtxt _ -> 1
+ rank | gla_exts = Arbitrary
+ | otherwise
+ = case ctxt of -- Haskell 98
+ GenPatCtxt -> Rank 0
+ PatSigCtxt -> Rank 0
+ ResSigCtxt -> Rank 0
+ TySynCtxt _ -> Rank 0
+ ExprSigCtxt -> Rank 1
+ FunSigCtxt _ -> Rank 1
+ ConArgCtxt _ -> Rank 1 -- We are given the type of the entire
+ -- constructor, hence rank 1
+ ForSigCtxt _ -> Rank 1
+ RuleSigCtxt _ -> Rank 1
actual_kind = typeKind ty
GenPatCtxt -> actual_kind_is_lifted
ForSigCtxt _ -> actual_kind_is_lifted
other -> isTypeKind actual_kind
+
+ ubx_tup | not gla_exts = UT_NotOk
+ | otherwise = case ctxt of
+ TySynCtxt _ -> 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) $
+ addErrCtxt (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
+ check_poly_type rank ubx_tup ty
checkTypeCtxt ctxt ty
-- 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
+ppr_ty ty | null forall_tvs && notNull theta = pprTheta theta <+> ptext SLIT("=>") <+> ppr tau
| otherwise = ppr ty
where
(forall_tvs, theta, tau) = tcSplitSigmaTy ty
\begin{code}
-type Rank = Int
-check_poly_type :: Rank -> Type -> TcM ()
-check_poly_type rank ty
- | rank == 0
- = check_tau_type 0 False ty
- | otherwise -- rank > 0
+data Rank = Rank Int | Arbitrary
+
+decRank :: Rank -> Rank
+decRank Arbitrary = Arbitrary
+decRank (Rank n) = Rank (n-1)
+
+----------------------------------------
+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 ubx_tup ty
= let
(tvs, theta, tau) = tcSplitSigmaTy ty
in
- check_valid_theta SigmaCtxt theta `thenTc_`
- check_tau_type (rank-1) 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 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 (SourceTy 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 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 0 False ty
+forAllTyErr ty = ptext SLIT("Illegal polymorphic 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}
+
+
+
+%************************************************************************
+%* *
+\subsection{Checking a theta or source type}
+%* *
+%************************************************************************
+
+\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
+ -- 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")
+pprSourceTyCtxt (DataTyCtxt tc) = ptext SLIT("the context of the data type declaration for") <+> quotes (ppr tc)
+pprSourceTyCtxt InstThetaCtxt = ptext SLIT("the context of an instance declaration")
+pprSourceTyCtxt InstHeadCtxt = ptext SLIT("the head of an instance declaration")
+pprSourceTyCtxt TypeCtxt = ptext SLIT("the context of a type")
+\end{code}
+
+\begin{code}
+checkValidTheta :: SourceTyCtxt -> ThetaType -> TcM ()
+checkValidTheta ctxt theta
+ = addErrCtxt (checkThetaCtxt ctxt theta) (check_valid_theta ctxt theta)
+
+-------------------------
+check_valid_theta ctxt []
+ = returnM ()
+check_valid_theta ctxt theta
+ = getDOpts `thenM` \ dflags ->
+ warnTc (notNull dups) (dupPredWarn dups) `thenM_`
+ -- Actually, in instance decls and type signatures,
+ -- duplicate constraints are eliminated by TcMonoType.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
+ mappM_ check_arg_type tys `thenM_`
+ checkTc (arity == n_tys) arity_err `thenM_`
+ checkTc (check_class_pred_tys dflags ctxt tys)
+ (predTyVarErr pred $$ how_to_allow)
+
+ where
+ class_name = className cls
+ arity = classArity cls
+ n_tys = length tys
+ arity_err = arityErr "Class" class_name arity n_tys
+
+ 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
+ -- signatures; not in instance decls, superclasses etc
+ -- The reason for not allowing implicit params in instances is a bit subtle
+ -- If we allowed instance (?x::Int, Eq a) => Foo [a] where ...
+ -- then when we saw (e :: (?x::Int) => t) it would be unclear how to
+ -- discharge all the potential usas of the ?x in e. For example, a
+ -- 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) = mappM_ 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 isTyVarTy 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
+ = case tcSplitAppTy_maybe ty of
+ Just (ty, _) -> tyvar_head ty
+ Nothing -> False
\end{code}
Check for ambiguity
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
(see is_ambig).
\begin{code}
-checkAmbiguity :: [TyVar] -> ThetaType -> TauType -> TcM ()
-checkAmbiguity forall_tyvars theta tau
- = mapTc_ check_pred theta `thenTc_`
- returnTc ()
+checkAmbiguity :: [TyVar] -> ThetaType -> TyVarSet -> TcM ()
+checkAmbiguity forall_tyvars theta tau_tyvars
+ = mappM_ complain (filter is_ambig theta)
where
- tau_vars = tyVarsOfType tau
- extended_tau_vars = grow theta tau_vars
-
- is_ambig ct_var = (ct_var `elem` forall_tyvars) &&
+ 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)
- 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
-\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 =>"))]
+ 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}
+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"))
+ nest 4 (ptext SLIT("(at least one must be universally quantified here)"))
]
+\end{code}
-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
+\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") <+> 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)
+
+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}
+
%************************************************************************
%* *
-\subsection{Checking a theta or source type}
+\subsection{Validity check for TyCons}
%* *
%************************************************************************
+checkValidTyCon is called once the mutually-recursive knot has been
+tied, so we can look at things freely.
+
\begin{code}
-data SourceTyCtxt
- = ClassSCCtxt Name -- Superclasses of clas
- | SigmaCtxt -- Context of a normal for-all type
- | DataTyCtxt Name -- Context of a data decl
- | TypeCtxt -- Source type in an ordinary type
- | InstThetaCtxt -- Context of an instance decl
- | InstHeadCtxt -- Head of an instance decl
-
-pprSourceTyCtxt (ClassSCCtxt c) = ptext SLIT("the super-classes of class") <+> quotes (ppr c)
-pprSourceTyCtxt SigmaCtxt = ptext SLIT("the context of a polymorphic type")
-pprSourceTyCtxt (DataTyCtxt tc) = ptext SLIT("the context of the data type declaration for") <+> quotes (ppr tc)
-pprSourceTyCtxt InstThetaCtxt = ptext SLIT("the context of an instance declaration")
-pprSourceTyCtxt InstHeadCtxt = ptext SLIT("the head of an instance declaration")
-pprSourceTyCtxt TypeCtxt = ptext SLIT("the context of a type")
+checkValidTyCon :: TyCon -> TcM ()
+checkValidTyCon tc
+ | isSynTyCon tc = checkValidType (TySynCtxt name) syn_rhs
+ | otherwise
+ = -- Check the context on the data decl
+ checkValidTheta (DataTyCtxt name) (tyConTheta tc) `thenM_`
+
+ -- Check arg types of data constructors
+ mappM_ checkValidDataCon data_cons `thenM_`
+
+ -- Check that fields with the same name share a type
+ mappM_ check_fields groups
+
+ where
+ name = tyConName tc
+ (_, syn_rhs) = getSynTyConDefn tc
+ data_cons = tyConDataCons tc
+
+ fields = [field | con <- data_cons, field <- dataConFieldLabels con]
+ groups = equivClasses cmp_name fields
+ cmp_name field1 field2 = fieldLabelName field1 `compare` fieldLabelName field2
+
+ check_fields fields@(first_field_label : other_fields)
+ -- These fields all have the same name, but are from
+ -- different constructors in the data type
+ = -- Check that all the fields in the group have the same type
+ -- NB: this check assumes that all the constructors of a given
+ -- data type use the same type variables
+ checkTc (all (tcEqType field_ty) other_tys) (fieldTypeMisMatch field_name)
+ where
+ field_ty = fieldLabelType first_field_label
+ field_name = fieldLabelName first_field_label
+ other_tys = map fieldLabelType other_fields
+
+checkValidDataCon :: DataCon -> TcM ()
+checkValidDataCon con
+ = checkValidType ctxt (idType (dataConWrapId con)) `thenM_`
+ -- This checks the argument types and
+ -- ambiguity of the existential context (if any)
+ addErrCtxt (existentialCtxt con)
+ (checkFreeness ex_tvs ex_theta)
+ where
+ ctxt = ConArgCtxt (dataConName con)
+ (_, _, ex_tvs, ex_theta, _, _) = dataConSig con
+
+
+fieldTypeMisMatch field_name
+ = sep [ptext SLIT("Different constructors give different types for field"), quotes (ppr field_name)]
+
+existentialCtxt con = ptext SLIT("When checking the existential context of constructor")
+ <+> quotes (ppr con)
\end{code}
+
+checkValidClass is called once the mutually-recursive knot has been
+tied, so we can look at things freely.
+
\begin{code}
-checkValidTheta :: SourceTyCtxt -> ThetaType -> TcM ()
-checkValidTheta ctxt theta
- = tcAddErrCtxt (checkThetaCtxt ctxt theta) (check_valid_theta ctxt theta)
+checkValidClass :: Class -> TcM ()
+checkValidClass cls
+ = -- CHECK ARITY 1 FOR HASKELL 1.4
+ doptM Opt_GlasgowExts `thenM` \ gla_exts ->
--------------------------
-check_valid_theta ctxt []
- = returnTc ()
-check_valid_theta ctxt theta
- = getDOptsTc `thenNF_Tc` \ dflags ->
- warnTc (not (null dups)) (dupPredWarn dups) `thenNF_Tc_`
- mapTc_ (check_source_ty dflags ctxt) theta
- where
- (_,dups) = removeDups tcCmpPred theta
+ -- Check that the class is unary, unless GlaExs
+ checkTc (notNull tyvars) (nullaryClassErr cls) `thenM_`
+ checkTc (gla_exts || unary) (classArityErr cls) `thenM_`
--------------------------
-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)
+ -- Check the super-classes
+ checkValidTheta (ClassSCCtxt (className cls)) theta `thenM_`
+
+ -- Check the class operations
+ mappM_ check_op op_stuff `thenM_`
+
+ -- Check that if the class has generic methods, then the
+ -- class has only one parameter. We can't do generic
+ -- multi-parameter type classes!
+ checkTc (unary || no_generics) (genericMultiParamErr cls)
where
- class_name = className cls
- arity = classArity cls
- n_tys = length tys
- arity_err = arityErr "Class" class_name arity n_tys
+ (tyvars, theta, _, op_stuff) = classBigSig cls
+ unary = isSingleton tyvars
+ no_generics = null [() | (_, GenDefMeth) <- op_stuff]
- 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
+ check_op (sel_id, dm)
+ = checkValidTheta SigmaCtxt (tail theta) `thenM_`
+ -- The 'tail' removes the initial (C a) from the
+ -- class itself, leaving just the method type
-check_source_ty dflags SigmaCtxt (IParam name ty) = check_arg_type ty
-check_source_ty dflags TypeCtxt (NType tc tys) = mapTc_ check_arg_type tys
+ checkValidType (FunSigCtxt op_name) tau `thenM_`
--- Catch-all
-check_source_ty dflags ctxt sty = failWithTc (badSourceTyErr sty)
+ -- Check that for a generic method, the type of
+ -- the method is sufficiently simple
+ checkTc (dm /= GenDefMeth || validGenericMethodType op_ty)
+ (badGenericMethodType op_name op_ty)
+ where
+ op_name = idName sel_id
+ op_ty = idType sel_id
+ (_,theta,tau) = tcSplitSigmaTy op_ty
--------------------------
-tyvar_head ty -- Haskell 98 allows predicates of form
- | tcIsTyVarTy ty = True -- C (a ty1 .. tyn)
- | otherwise -- where a is a type variable
- = case tcSplitAppTy_maybe ty of
- Just (ty, _) -> tyvar_head ty
- Nothing -> False
-\end{code}
+nullaryClassErr cls
+ = ptext SLIT("No parameters for class") <+> quotes (ppr cls)
-\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)
+classArityErr cls
+ = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
+ parens (ptext SLIT("Use -fglasgow-exts to allow multi-parameter classes"))]
-checkThetaCtxt ctxt theta
- = vcat [ptext SLIT("In the context:") <+> pprTheta theta,
- ptext SLIT("While checking") <+> pprSourceTyCtxt ctxt ]
+genericMultiParamErr clas
+ = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+>
+ ptext SLIT("cannot have generic methods")
+
+badGenericMethodType op op_ty
+ = hang (ptext SLIT("Generic method type is too complex"))
+ 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
+ ptext SLIT("You can only use type variables, arrows, and tuples")])
\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
= check_tyvars dflags clas tys
-- WITH HASKELL 1.4, MUST HAVE C (T a b c)
- | length tys == 1,
+ | isSingleton tys,
Just (tycon, arg_tys) <- tcSplitTyConApp_maybe first_ty,
not (isSynTyCon tycon), -- ...but not a synonym
all tcIsTyVarTy arg_tys, -- Applied to type variables
- length (varSetElems (tyVarsOfTypes arg_tys)) == length arg_tys
+ 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)
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}
= hang (ptext SLIT("Unacceptable instance type for ccall-ish class"))
4 (pprClassPred clas [inst_ty])
\end{code}
-
-
-%************************************************************************
-%* *
-\subsection{Kind unification}
-%* *
-%************************************************************************
-
-\begin{code}
-unifyKind :: TcKind -- Expected
- -> TcKind -- Actual
- -> TcM ()
-unifyKind k1 k2
- = tcAddErrCtxtM (unifyCtxt "kind" k1 k2) $
- uTys k1 k1 k2 k2
-
-unifyKinds :: [TcKind] -> [TcKind] -> TcM ()
-unifyKinds [] [] = returnTc ()
-unifyKinds (k1:ks1) (k2:ks2) = unifyKind k1 k2 `thenTc_`
- unifyKinds ks1 ks2
-unifyKinds _ _ = panic "unifyKinds: length mis-match"
-\end{code}
-
-\begin{code}
-unifyOpenTypeKind :: TcKind -> TcM ()
--- Ensures that the argument kind is of the form (Type bx)
--- for some boxity bx
-
-unifyOpenTypeKind ty@(TyVarTy tyvar)
- = getTcTyVar tyvar `thenNF_Tc` \ maybe_ty ->
- case maybe_ty of
- Just ty' -> unifyOpenTypeKind ty'
- other -> unify_open_kind_help ty
-
-unifyOpenTypeKind ty
- | isTypeKind ty = returnTc ()
- | otherwise = unify_open_kind_help ty
-
-unify_open_kind_help ty -- Revert to ordinary unification
- = newBoxityVar `thenNF_Tc` \ boxity ->
- unifyKind ty (mkTyConApp typeCon [boxity])
-\end{code}
-
-
-%************************************************************************
-%* *
-\subsection[Unify-exported]{Exported unification functions}
-%* *
-%************************************************************************
-
-The exported functions are all defined as versions of some
-non-exported generic functions.
-
-Unify two @TauType@s. Dead straightforward.
-
-\begin{code}
-unifyTauTy :: TcTauType -> TcTauType -> TcM ()
-unifyTauTy ty1 ty2 -- ty1 expected, ty2 inferred
- = tcAddErrCtxtM (unifyCtxt "type" ty1 ty2) $
- uTys ty1 ty1 ty2 ty2
-\end{code}
-
-@unifyTauTyList@ unifies corresponding elements of two lists of
-@TauType@s. It uses @uTys@ to do the real work. The lists should be
-of equal length. We charge down the list explicitly so that we can
-complain if their lengths differ.
-
-\begin{code}
-unifyTauTyLists :: [TcTauType] -> [TcTauType] -> TcM ()
-unifyTauTyLists [] [] = returnTc ()
-unifyTauTyLists (ty1:tys1) (ty2:tys2) = uTys ty1 ty1 ty2 ty2 `thenTc_`
- unifyTauTyLists tys1 tys2
-unifyTauTyLists ty1s ty2s = panic "Unify.unifyTauTyLists: mismatched type lists!"
-\end{code}
-
-@unifyTauTyList@ takes a single list of @TauType@s and unifies them
-all together. It is used, for example, when typechecking explicit
-lists, when all the elts should be of the same type.
-
-\begin{code}
-unifyTauTyList :: [TcTauType] -> TcM ()
-unifyTauTyList [] = returnTc ()
-unifyTauTyList [ty] = returnTc ()
-unifyTauTyList (ty1:tys@(ty2:_)) = unifyTauTy ty1 ty2 `thenTc_`
- unifyTauTyList tys
-\end{code}
-
-%************************************************************************
-%* *
-\subsection[Unify-uTys]{@uTys@: getting down to business}
-%* *
-%************************************************************************
-
-@uTys@ is the heart of the unifier. Each arg happens twice, because
-we want to report errors in terms of synomyms if poss. The first of
-the pair is used in error messages only; it is always the same as the
-second, except that if the first is a synonym then the second may be a
-de-synonym'd version. This way we get better error messages.
-
-We call the first one \tr{ps_ty1}, \tr{ps_ty2} for ``possible synomym''.
-
-\begin{code}
-uTys :: TcTauType -> TcTauType -- Error reporting ty1 and real ty1
- -- ty1 is the *expected* type
-
- -> TcTauType -> TcTauType -- Error reporting ty2 and real ty2
- -- ty2 is the *actual* type
- -> TcM ()
-
- -- Always expand synonyms (see notes at end)
- -- (this also throws away FTVs)
-uTys ps_ty1 (NoteTy n1 ty1) ps_ty2 ty2 = uTys ps_ty1 ty1 ps_ty2 ty2
-uTys ps_ty1 ty1 ps_ty2 (NoteTy n2 ty2) = uTys ps_ty1 ty1 ps_ty2 ty2
-
- -- Ignore usage annotations inside typechecker
-uTys ps_ty1 (UsageTy _ ty1) ps_ty2 ty2 = uTys ps_ty1 ty1 ps_ty2 ty2
-uTys ps_ty1 ty1 ps_ty2 (UsageTy _ ty2) = uTys ps_ty1 ty1 ps_ty2 ty2
-
- -- Variables; go for uVar
-uTys ps_ty1 (TyVarTy tyvar1) ps_ty2 ty2 = uVar False tyvar1 ps_ty2 ty2
-uTys ps_ty1 ty1 ps_ty2 (TyVarTy tyvar2) = uVar True tyvar2 ps_ty1 ty1
- -- "True" means args swapped
-
- -- Predicates
-uTys _ (SourceTy (IParam n1 t1)) _ (SourceTy (IParam n2 t2))
- | n1 == n2 = uTys t1 t1 t2 t2
-uTys _ (SourceTy (ClassP c1 tys1)) _ (SourceTy (ClassP c2 tys2))
- | c1 == c2 = unifyTauTyLists tys1 tys2
-uTys _ (SourceTy (NType tc1 tys1)) _ (SourceTy (NType tc2 tys2))
- | tc1 == tc2 = unifyTauTyLists tys1 tys2
-
- -- Functions; just check the two parts
-uTys _ (FunTy fun1 arg1) _ (FunTy fun2 arg2)
- = uTys fun1 fun1 fun2 fun2 `thenTc_` uTys arg1 arg1 arg2 arg2
-
- -- Type constructors must match
-uTys ps_ty1 (TyConApp con1 tys1) ps_ty2 (TyConApp con2 tys2)
- | con1 == con2 && length tys1 == length tys2
- = unifyTauTyLists tys1 tys2
-
- | con1 == openKindCon
- -- When we are doing kind checking, we might match a kind '?'
- -- against a kind '*' or '#'. Notably, CCallable :: ? -> *, and
- -- (CCallable Int) and (CCallable Int#) are both OK
- = unifyOpenTypeKind ps_ty2
-
- -- Applications need a bit of care!
- -- They can match FunTy and TyConApp, so use splitAppTy_maybe
- -- NB: we've already dealt with type variables and Notes,
- -- so if one type is an App the other one jolly well better be too
-uTys ps_ty1 (AppTy s1 t1) ps_ty2 ty2
- = case tcSplitAppTy_maybe ty2 of
- Just (s2,t2) -> uTys s1 s1 s2 s2 `thenTc_` uTys t1 t1 t2 t2
- Nothing -> unifyMisMatch ps_ty1 ps_ty2
-
- -- Now the same, but the other way round
- -- Don't swap the types, because the error messages get worse
-uTys ps_ty1 ty1 ps_ty2 (AppTy s2 t2)
- = case tcSplitAppTy_maybe ty1 of
- Just (s1,t1) -> uTys s1 s1 s2 s2 `thenTc_` uTys t1 t1 t2 t2
- Nothing -> unifyMisMatch ps_ty1 ps_ty2
-
- -- Not expecting for-alls in unification
- -- ... but the error message from the unifyMisMatch more informative
- -- than a panic message!
-
- -- Anything else fails
-uTys ps_ty1 ty1 ps_ty2 ty2 = unifyMisMatch ps_ty1 ps_ty2
-\end{code}
-
-
-Notes on synonyms
-~~~~~~~~~~~~~~~~~
-If you are tempted to make a short cut on synonyms, as in this
-pseudocode...
-
-\begin{verbatim}
--- NO uTys (SynTy con1 args1 ty1) (SynTy con2 args2 ty2)
--- NO = if (con1 == con2) then
--- NO -- Good news! Same synonym constructors, so we can shortcut
--- NO -- by unifying their arguments and ignoring their expansions.
--- NO unifyTauTypeLists args1 args2
--- NO else
--- NO -- Never mind. Just expand them and try again
--- NO uTys ty1 ty2
-\end{verbatim}
-
-then THINK AGAIN. Here is the whole story, as detected and reported
-by Chris Okasaki \tr{<Chris_Okasaki@loch.mess.cs.cmu.edu>}:
-\begin{quotation}
-Here's a test program that should detect the problem:
-
-\begin{verbatim}
- type Bogus a = Int
- x = (1 :: Bogus Char) :: Bogus Bool
-\end{verbatim}
-
-The problem with [the attempted shortcut code] is that
-\begin{verbatim}
- con1 == con2
-\end{verbatim}
-is not a sufficient condition to be able to use the shortcut!
-You also need to know that the type synonym actually USES all
-its arguments. For example, consider the following type synonym
-which does not use all its arguments.
-\begin{verbatim}
- type Bogus a = Int
-\end{verbatim}
-
-If you ever tried unifying, say, \tr{Bogus Char} with \tr{Bogus Bool},
-the unifier would blithely try to unify \tr{Char} with \tr{Bool} and
-would fail, even though the expanded forms (both \tr{Int}) should
-match.
-
-Similarly, unifying \tr{Bogus Char} with \tr{Bogus t} would
-unnecessarily bind \tr{t} to \tr{Char}.
-
-... You could explicitly test for the problem synonyms and mark them
-somehow as needing expansion, perhaps also issuing a warning to the
-user.
-\end{quotation}
-
-
-%************************************************************************
-%* *
-\subsection[Unify-uVar]{@uVar@: unifying with a type variable}
-%* *
-%************************************************************************
-
-@uVar@ is called when at least one of the types being unified is a
-variable. It does {\em not} assume that the variable is a fixed point
-of the substitution; rather, notice that @uVar@ (defined below) nips
-back into @uTys@ if it turns out that the variable is already bound.
-
-\begin{code}
-uVar :: Bool -- False => tyvar is the "expected"
- -- True => ty is the "expected" thing
- -> TcTyVar
- -> TcTauType -> TcTauType -- printing and real versions
- -> TcM ()
-
-uVar swapped tv1 ps_ty2 ty2
- = getTcTyVar tv1 `thenNF_Tc` \ maybe_ty1 ->
- case maybe_ty1 of
- Just ty1 | swapped -> uTys ps_ty2 ty2 ty1 ty1 -- Swap back
- | otherwise -> uTys ty1 ty1 ps_ty2 ty2 -- Same order
- other -> uUnboundVar swapped tv1 maybe_ty1 ps_ty2 ty2
-
- -- Expand synonyms; ignore FTVs
-uUnboundVar swapped tv1 maybe_ty1 ps_ty2 (NoteTy n2 ty2)
- = uUnboundVar swapped tv1 maybe_ty1 ps_ty2 ty2
-
-
- -- The both-type-variable case
-uUnboundVar swapped tv1 maybe_ty1 ps_ty2 ty2@(TyVarTy tv2)
-
- -- Same type variable => no-op
- | tv1 == tv2
- = returnTc ()
-
- -- Distinct type variables
- -- ASSERT maybe_ty1 /= Just
- | otherwise
- = getTcTyVar tv2 `thenNF_Tc` \ maybe_ty2 ->
- case maybe_ty2 of
- Just ty2' -> uUnboundVar swapped tv1 maybe_ty1 ty2' ty2'
-
- Nothing | update_tv2
-
- -> WARN( not (k1 `hasMoreBoxityInfo` k2), (ppr tv1 <+> ppr k1) $$ (ppr tv2 <+> ppr k2) )
- putTcTyVar tv2 (TyVarTy tv1) `thenNF_Tc_`
- returnTc ()
- | otherwise
-
- -> WARN( not (k2 `hasMoreBoxityInfo` k1), (ppr tv2 <+> ppr k2) $$ (ppr tv1 <+> ppr k1) )
- (putTcTyVar tv1 ps_ty2 `thenNF_Tc_`
- returnTc ())
- where
- k1 = tyVarKind tv1
- k2 = tyVarKind tv2
- update_tv2 = (k2 `eqKind` openTypeKind) || (not (k1 `eqKind` openTypeKind) && nicer_to_update_tv2)
- -- Try to get rid of open type variables as soon as poss
-
- nicer_to_update_tv2 = isSigTyVar tv1
- -- Don't unify a signature type variable if poss
- || isSystemName (varName tv2)
- -- Try to update sys-y type variables in preference to sig-y ones
-
- -- Second one isn't a type variable
-uUnboundVar swapped tv1 maybe_ty1 ps_ty2 non_var_ty2
- = -- Check that the kinds match
- checkKinds swapped tv1 non_var_ty2 `thenTc_`
-
- -- Check that tv1 isn't a type-signature type variable
- checkTcM (not (isSigTyVar tv1))
- (failWithTcM (unifyWithSigErr tv1 ps_ty2)) `thenTc_`
-
- -- Check that we aren't losing boxity info (shouldn't happen)
- warnTc (not (typeKind non_var_ty2 `hasMoreBoxityInfo` tyVarKind tv1))
- ((ppr tv1 <+> ppr (tyVarKind tv1)) $$
- (ppr non_var_ty2 <+> ppr (typeKind non_var_ty2))) `thenNF_Tc_`
-
- -- Occurs check
- -- Basically we want to update tv1 := ps_ty2
- -- because ps_ty2 has type-synonym info, which improves later error messages
- --
- -- But consider
- -- type A a = ()
- --
- -- f :: (A a -> a -> ()) -> ()
- -- f = \ _ -> ()
- --
- -- x :: ()
- -- x = f (\ x p -> p x)
- --
- -- In the application (p x), we try to match "t" with "A t". If we go
- -- ahead and bind t to A t (= ps_ty2), we'll lead the type checker into
- -- an infinite loop later.
- -- But we should not reject the program, because A t = ().
- -- Rather, we should bind t to () (= non_var_ty2).
- --
- -- That's why we have this two-state occurs-check
- zonkTcType ps_ty2 `thenNF_Tc` \ ps_ty2' ->
- if not (tv1 `elemVarSet` tyVarsOfType ps_ty2') then
- putTcTyVar tv1 ps_ty2' `thenNF_Tc_`
- returnTc ()
- else
- zonkTcType non_var_ty2 `thenNF_Tc` \ non_var_ty2' ->
- if not (tv1 `elemVarSet` tyVarsOfType non_var_ty2') then
- -- This branch rarely succeeds, except in strange cases
- -- like that in the example above
- putTcTyVar tv1 non_var_ty2' `thenNF_Tc_`
- returnTc ()
- else
- failWithTcM (unifyOccurCheck tv1 ps_ty2')
-
-
-checkKinds swapped tv1 ty2
--- We're about to unify a type variable tv1 with a non-tyvar-type ty2.
--- We need to check that we don't unify a lifted type variable with an
--- unlifted type: e.g. (id 3#) is illegal
- | tk1 `eqKind` liftedTypeKind && tk2 `eqKind` unliftedTypeKind
- = tcAddErrCtxtM (unifyKindCtxt swapped tv1 ty2) $
- unifyMisMatch k1 k2
- | otherwise
- = returnTc ()
- where
- (k1,k2) | swapped = (tk2,tk1)
- | otherwise = (tk1,tk2)
- tk1 = tyVarKind tv1
- tk2 = typeKind ty2
-\end{code}
-
-
-%************************************************************************
-%* *
-\subsection[Unify-fun]{@unifyFunTy@}
-%* *
-%************************************************************************
-
-@unifyFunTy@ is used to avoid the fruitless creation of type variables.
-
-\begin{code}
-unifyFunTy :: TcType -- Fail if ty isn't a function type
- -> TcM (TcType, TcType) -- otherwise return arg and result types
-
-unifyFunTy ty@(TyVarTy tyvar)
- = getTcTyVar tyvar `thenNF_Tc` \ maybe_ty ->
- case maybe_ty of
- Just ty' -> unifyFunTy ty'
- other -> unify_fun_ty_help ty
-
-unifyFunTy ty
- = case tcSplitFunTy_maybe ty of
- Just arg_and_res -> returnTc arg_and_res
- Nothing -> unify_fun_ty_help ty
-
-unify_fun_ty_help ty -- Special cases failed, so revert to ordinary unification
- = newTyVarTy openTypeKind `thenNF_Tc` \ arg ->
- newTyVarTy openTypeKind `thenNF_Tc` \ res ->
- unifyTauTy ty (mkFunTy arg res) `thenTc_`
- returnTc (arg,res)
-\end{code}
-
-\begin{code}
-unifyListTy :: TcType -- expected list type
- -> TcM TcType -- list element type
-
-unifyListTy ty@(TyVarTy tyvar)
- = getTcTyVar tyvar `thenNF_Tc` \ maybe_ty ->
- case maybe_ty of
- Just ty' -> unifyListTy ty'
- other -> unify_list_ty_help ty
-
-unifyListTy ty
- = case tcSplitTyConApp_maybe ty of
- Just (tycon, [arg_ty]) | tycon == listTyCon -> returnTc arg_ty
- other -> unify_list_ty_help ty
-
-unify_list_ty_help ty -- Revert to ordinary unification
- = newTyVarTy liftedTypeKind `thenNF_Tc` \ elt_ty ->
- unifyTauTy ty (mkListTy elt_ty) `thenTc_`
- returnTc elt_ty
-\end{code}
-
-\begin{code}
-unifyTupleTy :: Boxity -> Arity -> TcType -> TcM [TcType]
-unifyTupleTy boxity arity ty@(TyVarTy tyvar)
- = getTcTyVar tyvar `thenNF_Tc` \ maybe_ty ->
- case maybe_ty of
- Just ty' -> unifyTupleTy boxity arity ty'
- other -> unify_tuple_ty_help boxity arity ty
-
-unifyTupleTy boxity arity ty
- = case tcSplitTyConApp_maybe ty of
- Just (tycon, arg_tys)
- | isTupleTyCon tycon
- && tyConArity tycon == arity
- && tupleTyConBoxity tycon == boxity
- -> returnTc arg_tys
- other -> unify_tuple_ty_help boxity arity ty
-
-unify_tuple_ty_help boxity arity ty
- = newTyVarTys arity kind `thenNF_Tc` \ arg_tys ->
- unifyTauTy ty (mkTupleTy boxity arity arg_tys) `thenTc_`
- returnTc arg_tys
- where
- kind | isBoxed boxity = liftedTypeKind
- | otherwise = openTypeKind
-\end{code}
-
-
-%************************************************************************
-%* *
-\subsection[Unify-context]{Errors and contexts}
-%* *
-%************************************************************************
-
-Errors
-~~~~~~
-
-\begin{code}
-unifyCtxt s ty1 ty2 tidy_env -- ty1 expected, ty2 inferred
- = zonkTcType ty1 `thenNF_Tc` \ ty1' ->
- zonkTcType ty2 `thenNF_Tc` \ ty2' ->
- returnNF_Tc (err ty1' ty2')
- where
- err ty1 ty2 = (env1,
- nest 4
- (vcat [
- text "Expected" <+> text s <> colon <+> ppr tidy_ty1,
- text "Inferred" <+> text s <> colon <+> ppr tidy_ty2
- ]))
- where
- (env1, [tidy_ty1,tidy_ty2]) = tidyOpenTypes tidy_env [ty1,ty2]
-
-unifyKindCtxt swapped tv1 ty2 tidy_env -- not swapped => tv1 expected, ty2 inferred
- -- tv1 is zonked already
- = zonkTcType ty2 `thenNF_Tc` \ ty2' ->
- returnNF_Tc (err ty2')
- where
- err ty2 = (env2, ptext SLIT("When matching types") <+>
- sep [quotes pp_expected, ptext SLIT("and"), quotes pp_actual])
- where
- (pp_expected, pp_actual) | swapped = (pp2, pp1)
- | otherwise = (pp1, pp2)
- (env1, tv1') = tidyOpenTyVar tidy_env tv1
- (env2, ty2') = tidyOpenType env1 ty2
- pp1 = ppr tv1'
- pp2 = ppr ty2'
-
-unifyMisMatch ty1 ty2
- = zonkTcType ty1 `thenNF_Tc` \ ty1' ->
- zonkTcType ty2 `thenNF_Tc` \ ty2' ->
- let
- (env, [tidy_ty1, tidy_ty2]) = tidyOpenTypes emptyTidyEnv [ty1',ty2']
- msg = hang (ptext SLIT("Couldn't match"))
- 4 (sep [quotes (ppr tidy_ty1),
- ptext SLIT("against"),
- quotes (ppr tidy_ty2)])
- in
- failWithTcM (env, msg)
-
-unifyWithSigErr tyvar ty
- = (env2, hang (ptext SLIT("Cannot unify the type-signature variable") <+> quotes (ppr tidy_tyvar))
- 4 (ptext SLIT("with the type") <+> quotes (ppr tidy_ty)))
- where
- (env1, tidy_tyvar) = tidyOpenTyVar emptyTidyEnv tyvar
- (env2, tidy_ty) = tidyOpenType env1 ty
-
-unifyOccurCheck tyvar ty
- = (env2, hang (ptext SLIT("Occurs check: cannot construct the infinite type:"))
- 4 (sep [ppr tidy_tyvar, char '=', ppr tidy_ty]))
- where
- (env1, tidy_tyvar) = tidyOpenTyVar emptyTidyEnv tyvar
- (env2, tidy_ty) = tidyOpenType env1 ty
-\end{code}
projects / ghc-hetmet.git / blobdiff