--------------------------------
-- Creating new mutable type variables
- newTyVar,
- newTyVarTy, -- Kind -> TcM TcType
- newTyVarTys, -- Int -> Kind -> TcM [TcType]
- newKindVar, newKindVars, newOpenTypeKind,
- putTcTyVar, getTcTyVar,
- newMutTyVar, readMutTyVar, writeMutTyVar,
-
- newHoleTyVarTy, readHoleResult, zapToType,
+ newFlexiTyVar,
+ newTyFlexiVarTy, -- Kind -> TcM TcType
+ newTyFlexiVarTys, -- Int -> Kind -> TcM [TcType]
+ newKindVar, newKindVars,
+ lookupTcTyVar, condLookupTcTyVar, LookupTyVarResult(..),
+ newMetaTyVar, readMetaTyVar, writeMetaTyVar, putMetaTyVar,
--------------------------------
-- Instantiation
tcInstTyVar, tcInstTyVars, tcInstType,
+ tcSkolType, tcSkolTyVars, tcInstSigType,
+ tcSkolSigType, tcSkolSigTyVars,
--------------------------------
-- Checking type validity
- Rank, UserTypeCtxt(..), checkValidType, pprUserTypeCtxt,
- SourceTyCtxt(..), checkValidTheta,
- checkValidTyCon, checkValidClass,
+ Rank, UserTypeCtxt(..), checkValidType, pprHsSigCtxt,
+ SourceTyCtxt(..), checkValidTheta, checkFreeness,
checkValidInstHead, instTypeErr, checkAmbiguity,
- arityErr,
+ arityErr,
--------------------------------
-- Zonking
- zonkType,
- zonkTcTyVar, zonkTcTyVars, zonkTcTyVarsAndFV,
+ zonkType, zonkTcPredType,
+ zonkTcTyVar, zonkTcTyVars, zonkTcTyVarsAndFV, zonkQuantifiedTyVar,
zonkTcType, zonkTcTypes, zonkTcClassConstraints, zonkTcThetaType,
- zonkTcPredType, zonkTcTyVarToTyVar, zonkKindEnv,
+ zonkTcKindToKind, zonkTcKind,
+
+ readKindVar, writeKindVar
) where
-- friends:
-import TypeRep ( Type(..), SourceType(..), TyNote(..), -- Friend; can see representation
- Kind, ThetaType, typeCon
+import HsSyn ( LHsType )
+import TypeRep ( Type(..), PredType(..), TyNote(..), -- Friend; can see representation
+ Kind, ThetaType
)
import TcType ( TcType, TcThetaType, TcTauType, TcPredType,
- TcTyVarSet, TcKind, TcTyVar, TyVarDetails(..),
- tcEqType, tcCmpPred, isClassPred,
+ TcTyVarSet, TcKind, TcTyVar, TcTyVarDetails(..),
+ MetaDetails(..), SkolemInfo(..), isMetaTyVar, metaTvRef,
+ tcCmpPred, isClassPred,
tcSplitPhiTy, tcSplitPredTy_maybe, tcSplitAppTy_maybe,
tcSplitTyConApp_maybe, tcSplitForAllTys,
- tcIsTyVarTy, tcSplitSigmaTy, mkTyConApp,
- isUnLiftedType, isIPPred, isHoleTyVar, isTyVarTy,
-
+ tcIsTyVarTy, tcSplitSigmaTy, tcIsTyVarTy,
+ 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 ( Class, DefMeth(..), classArity, className, classBigSig )
+import Type ( TvSubst, zipTopTvSubst, substTy )
+import Class ( Class, classArity, className )
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 )
+ tyConArity, tyConName )
+import Var ( TyVar, tyVarKind, tyVarName,
+ mkTyVar, mkTcTyVar, tcTyVarDetails, isTcTyVar )
-- others:
-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, setNameUnique, mkSystemTvNameEncoded )
+import Name ( Name, setNameUnique, mkSysTvName )
import VarSet
+import VarEnv
import CmdLineOpts ( dopt, DynFlag(..) )
+import UniqSupply ( uniqsFromSupply )
import Util ( nOfThem, isSingleton, equalLength, notNull )
-import ListSetOps ( equivClasses, removeDups )
+import ListSetOps ( removeDups )
+import SrcLoc ( unLoc )
import Outputable
\end{code}
%************************************************************************
\begin{code}
-newMutTyVar :: Name -> Kind -> TyVarDetails -> TcM TyVar
-newMutTyVar name kind details
- = do { ref <- newMutVar Nothing ;
- return (mkMutTyVar name kind details ref) }
+newMetaTyVar :: Name -> Kind -> MetaDetails -> TcM TyVar
+newMetaTyVar name kind details
+ = do { ref <- newMutVar details ;
+ return (mkTcTyVar name kind (MetaTv ref)) }
-readMutTyVar :: TyVar -> TcM (Maybe Type)
-readMutTyVar tyvar = readMutVar (mutTyVarRef tyvar)
+readMetaTyVar :: TyVar -> TcM MetaDetails
+readMetaTyVar tyvar = ASSERT2( isMetaTyVar tyvar, ppr tyvar )
+ readMutVar (metaTvRef tyvar)
-writeMutTyVar :: TyVar -> Maybe Type -> TcM ()
-writeMutTyVar tyvar val = writeMutVar (mutTyVarRef tyvar) val
+writeMetaTyVar :: TyVar -> MetaDetails -> TcM ()
+writeMetaTyVar tyvar val = ASSERT2( isMetaTyVar tyvar, ppr tyvar )
+ writeMutVar (metaTvRef tyvar) val
-newTyVar :: Kind -> TcM TcTyVar
-newTyVar kind
+newFlexiTyVar :: Kind -> TcM TcTyVar
+newFlexiTyVar kind
= newUnique `thenM` \ uniq ->
- newMutTyVar (mkSystemTvNameEncoded uniq FSLIT("t")) kind VanillaTv
+ newMetaTyVar (mkSysTvName uniq FSLIT("t")) kind Flexi
-newTyVarTy :: Kind -> TcM TcType
-newTyVarTy kind
- = newTyVar kind `thenM` \ tc_tyvar ->
+newTyFlexiVarTy :: Kind -> TcM TcType
+newTyFlexiVarTy kind
+ = newFlexiTyVar kind `thenM` \ tc_tyvar ->
returnM (TyVarTy tc_tyvar)
-newTyVarTys :: Int -> Kind -> TcM [TcType]
-newTyVarTys n kind = mappM newTyVarTy (nOfThem n kind)
+newTyFlexiVarTys :: Int -> Kind -> TcM [TcType]
+newTyFlexiVarTys n kind = mappM newTyFlexiVarTy (nOfThem n kind)
newKindVar :: TcM TcKind
-newKindVar
- = newUnique `thenM` \ uniq ->
- newMutTyVar (mkSystemTvNameEncoded uniq FSLIT("k")) superKind VanillaTv `thenM` \ kv ->
- returnM (TyVarTy kv)
+newKindVar = do { uniq <- newUnique
+ ; ref <- newMutVar Nothing
+ ; return (KindVar (mkKindVar uniq ref)) }
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}
%************************************************************************
%* *
-\subsection{'hole' type variables}
-%* *
-%************************************************************************
-
-\begin{code}
-newHoleTyVarTy :: TcM TcType
- = newUnique `thenM` \ uniq ->
- newMutTyVar (mkSystemTvNameEncoded uniq FSLIT("h")) openTypeKind HoleTv `thenM` \ tv ->
- returnM (TyVarTy tv)
-
-readHoleResult :: TcType -> TcM TcType
--- Read the answer out of a hole, constructed by newHoleTyVarTy
-readHoleResult (TyVarTy tv)
- = ASSERT( isHoleTyVar tv )
- getTcTyVar tv `thenM` \ maybe_res ->
- case maybe_res of
- Just ty -> returnM ty
- Nothing -> pprPanic "readHoleResult: empty" (ppr tv)
-readHoleResult ty = pprPanic "readHoleResult: not hole" (ppr ty)
-
-zapToType :: TcType -> TcM TcType
-zapToType (TyVarTy tv)
- | isHoleTyVar tv
- = getTcTyVar tv `thenM` \ maybe_res ->
- case maybe_res of
- Nothing -> newTyVarTy openTypeKind `thenM` \ ty ->
- putTcTyVar tv ty `thenM_`
- returnM ty
- Just ty -> returnM ty -- No need to loop; we never
- -- have chains of holes
-
-zapToType other_ty = returnM other_ty
-\end{code}
-
-%************************************************************************
-%* *
\subsection{Type instantiation}
%* *
%************************************************************************
Instantiating a bunch of type variables
-\begin{code}
-tcInstTyVars :: TyVarDetails -> [TyVar]
- -> TcM ([TcTyVar], [TcType], Subst)
+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.
-tcInstTyVars tv_details tyvars
- = mappM (tcInstTyVar tv_details) tyvars `thenM` \ tc_tyvars ->
- let
- tys = mkTyVarTys tc_tyvars
- in
- returnM (tc_tyvars, tys, mkTopTyVarSubst tyvars tys)
+
+\begin{code}
+-----------------------
+tcInstTyVars :: [TyVar] -> TcM ([TcTyVar], [TcType], TvSubst)
+tcInstTyVars tyvars
+ = 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 tv_details tyvar
- = newUnique `thenM` \ 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 mkSystemName.
- in
- newMutTyVar name (tyVarKind tyvar) tv_details
+ -- any existing for-alls. Hence zipTopTvSubst
+
+tcInstTyVar tyvar -- Freshen the Name of the tyvar
+ = do { uniq <- newUnique
+ ; newMetaTyVar (setNameUnique (tyVarName tyvar) uniq)
+ (tyVarKind tyvar) Flexi }
-tcInstType :: TyVarDetails -> TcType -> TcM ([TcTyVar], TcThetaType, TcType)
+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 tv_details ty
+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 despite no type variables;
+ ([], rho) -> let -- There may be overloading despite no type variables;
-- (?x :: Int) => Int -> Int
- let
(theta, tau) = tcSplitPhiTy rho
in
- returnM ([], theta, tau)
+ return ([], theta, tau)
- (tyvars, rho) -> tcInstTyVars tv_details tyvars `thenM` \ (tyvars', _, tenv) ->
- let
- (theta, tau) = tcSplitPhiTy (substTy tenv rho)
- in
- returnM (tyvars', theta, tau)
+ (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 -> TcM TcType
-getTcTyVar :: TcTyVar -> 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) $
- returnM ty
+ returnM ()
| otherwise
- = ASSERT( isMutTyVar tyvar )
- writeMutTyVar tyvar (Just ty) `thenM_`
- returnM 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 = readMutTyVar 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) $
returnM (Just (mkTyVarTy tyvar))
| otherwise
- = ASSERT2( isMutTyVar tyvar, ppr tyvar )
- readMutTyVar tyvar `thenM` \ maybe_ty ->
+ = ASSERT2( isTcTyVar tyvar, ppr tyvar )
+ readMetaTyVar tyvar `thenM` \ maybe_ty ->
case maybe_ty of
Just ty -> short_out ty `thenM` \ ty' ->
- writeMutTyVar tyvar (Just ty') `thenM_`
+ writeMetaTyVar tyvar (Just ty') `thenM_`
returnM (Just ty')
Nothing -> returnM Nothing
short_out :: TcType -> TcM TcType
short_out ty@(TyVarTy tyvar)
- | not (isMutTyVar tyvar)
+ | not (isTcTyVar tyvar)
= returnM ty
| otherwise
- = readMutTyVar tyvar `thenM` \ maybe_ty ->
+ = readMetaTyVar tyvar `thenM` \ maybe_ty ->
case maybe_ty of
Just ty' -> short_out ty' `thenM` \ ty' ->
- writeMutTyVar tyvar (Just ty') `thenM_`
+ writeMetaTyVar tyvar (Just ty') `thenM_`
returnM ty'
other -> returnM ty
short_out other_ty = returnM other_ty
+-}
\end{code}
returnM (tyVarsOfTypes tys)
zonkTcTyVar :: TcTyVar -> TcM TcType
-zonkTcTyVar tyvar = zonkTyVar (\ tv -> returnM (TyVarTy tv)) tyvar
+zonkTcTyVar tyvar = zonkTyVar (\ tv -> returnM (TyVarTy tv)) True tyvar
\end{code}
----------------- Types
\begin{code}
zonkTcType :: TcType -> TcM TcType
-zonkTcType ty = zonkType (\ tv -> returnM (TyVarTy tv)) ty
+zonkTcType ty = zonkType (\ tv -> returnM (TyVarTy tv)) True ty
zonkTcTypes :: [TcType] -> TcM [TcType]
zonkTcTypes tys = mappM zonkTcType tys
are used at the end of type checking
\begin{code}
-zonkKindEnv :: [(Name, TcKind)] -> TcM [(Name, Kind)]
-zonkKindEnv pairs
- = mappM zonk_it pairs
- where
- 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 *)
- -- 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)
-
--- 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.
-
-zonkTcTyVarToTyVar :: TcTyVar -> 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
-
- 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 `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 $$ ppr ty2 )
-
- returnM immut_tv
+zonkQuantifiedTyVar :: TcTyVar -> TcM TyVar
+-- zonkQuantifiedTyVar is applied to the a TcTyVar when quantifying over it.
+-- It might be a meta TyVar, in which case we freeze it into an ordinary TyVar.
+-- When we do this, we also default the kind -- see notes with Kind.defaultKind
+-- The meta tyvar is updated to point to the new regular TyVar. Now any
+-- bound occurences of the original type variable will get zonked to
+-- the immutable version.
+--
+-- We leave skolem TyVars alone; they are immutable.
+zonkQuantifiedTyVar tv
+ | isSkolemTyVar tv = return tv
+ -- It might be a skolem type variable,
+ -- for example from a user type signature
+
+ | otherwise -- It's a meta-type-variable
+ = do { details <- readMetaTyVar tv
+
+ -- Create the new, frozen, regular type variable
+ ; let final_kind = defaultKind (tyVarKind tv)
+ final_tv = mkTyVar (tyVarName tv) final_kind
+
+ -- Bind the meta tyvar to the new tyvar
+ ; case details of
+ Indirect ty -> WARN( True, ppr tv $$ 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}
[Silly Type Synonyms]
* 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.
+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 -> TcM Type) -- What to do with unbound mutable type variables
-- see zonkTcType, and zonkTcTypeToType
- -> TcType
+ -> Bool -- Should we consult the current type refinement?
+ -> TcType
-> TcM Type
-zonkType unbound_var_fn ty
+zonkType unbound_var_fn rflag ty
= go ty
where
go (TyConApp tycon tys) = mappM go tys `thenM` \ tys' ->
go (NoteTy (FTVNote _) ty2) = go ty2 -- Discard free-tyvar annotations
- go (SourceTy p) = go_pred p `thenM` \ p' ->
- returnM (SourceTy p')
+ go (PredTy p) = go_pred p `thenM` \ p' ->
+ returnM (PredTy p')
go (FunTy arg res) = go arg `thenM` \ arg' ->
go res `thenM` \ res' ->
-- to pull the TyConApp to the top.
-- The two interesting cases!
- go (TyVarTy tyvar) = zonkTyVar unbound_var_fn tyvar
+ go (TyVarTy tyvar) = zonkTyVar unbound_var_fn rflag tyvar
- go (ForAllTy tyvar ty) = zonkTcTyVarToTyVar tyvar `thenM` \ tyvar' ->
- go ty `thenM` \ ty' ->
- returnM (ForAllTy tyvar' ty')
+ 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 (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 -> 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
- returnM (TyVarTy tyvar)
+ -> 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 `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
+ = 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
- = doptM Opt_GlasgowExts `thenM` \ 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
- addErrCtxt (checkTypeCtxt ctxt ty) $
-
-- Check that the thing has kind Type, and is lifted if necessary
checkTc kind_ok (kindErr actual_kind) `thenM_`
-- Check the internal validity of the type itself
- check_poly_type rank ubx_tup 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 && notNull 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}
-- Rank is allowed rank for function args
-- No foralls otherwise
-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 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_`
= 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
+ -- Args are allowed to be unlifted, or
+ -- more unboxed tuples, so can't use check_arg_ty
| otherwise
= mappM_ check_arg_type tys
ubx_tup_msg = ubxArgTyErr 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
+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}
+-- 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")
= getDOpts `thenM` \ dflags ->
warnTc (notNull dups) (dupPredWarn dups) `thenM_`
-- Actually, in instance decls and type signatures,
- -- duplicate constraints are eliminated by TcMonoType.hoistForAllTys,
+ -- 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
-------------------------
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_`
+
+ -- 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)
-- 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)
= case ctxt of
InstHeadCtxt -> True -- We check for instance-head
-- formation in checkValidInstHead
- InstThetaCtxt -> undecidable_ok || all isTyVarTy tys
+ InstThetaCtxt -> undecidable_ok || all tcIsTyVarTy tys
other -> gla_exts || all tyvar_head tys
where
undecidable_ok = dopt Opt_AllowUndecidableInstances dflags
= vcat [ptext SLIT("In the context:") <+> pprTheta theta,
ptext SLIT("While checking") <+> pprSourceTyCtxt ctxt ]
-badSourceTyErr sty = ptext SLIT("Illegal constraint") <+> pprSourceType sty
+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)
%************************************************************************
%* *
-\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}
-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}
-checkValidClass :: Class -> TcM ()
-checkValidClass cls
- = -- CHECK ARITY 1 FOR HASKELL 1.4
- doptM Opt_GlasgowExts `thenM` \ gla_exts ->
-
- -- Check that the class is unary, unless GlaExs
- checkTc (notNull tyvars) (nullaryClassErr cls) `thenM_`
- checkTc (gla_exts || unary) (classArityErr cls) `thenM_`
-
- -- 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
- (tyvars, theta, _, op_stuff) = classBigSig cls
- unary = isSingleton tyvars
- no_generics = null [() | (_, GenDefMeth) <- op_stuff]
-
- 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
-
- checkValidType (FunSigCtxt op_name) tau `thenM_`
-
- -- 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
-
-nullaryClassErr cls
- = ptext SLIT("No parameters for class") <+> quotes (ppr cls)
-
-classArityErr cls
- = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
- parens (ptext SLIT("Use -fglasgow-exts to allow multi-parameter classes"))]
-
-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}
-
-
-%************************************************************************
-%* *
\subsection{Checking for a decent instance head type}
%* *
%************************************************************************
}}
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
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")
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}
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