--------------------------------
-- Creating new mutable type variables
- newTyVar, newHoleTyVarTy,
+ newTyVar,
newTyVarTy, -- Kind -> NF_TcM TcType
newTyVarTys, -- Int -> Kind -> NF_TcM [TcType]
newKindVar, newKindVars, newBoxityVar,
putTcTyVar, getTcTyVar,
+ newHoleTyVarTy, readHoleResult, zapToType,
+
--------------------------------
-- Instantiation
- tcInstTyVar, tcInstTyVars,
- tcInstSigTyVars, tcInstType, tcInstSigType,
- tcSplitRhoTyM,
+ tcInstTyVar, tcInstTyVars, tcInstType,
--------------------------------
-- Checking type validity
Rank, UserTypeCtxt(..), checkValidType, pprUserTypeCtxt,
SourceTyCtxt(..), checkValidTheta,
+ checkValidTyCon, checkValidClass,
checkValidInstHead, instTypeErr, checkAmbiguity,
--------------------------------
import TcType ( TcType, TcThetaType, TcTauType, TcPredType,
TcTyVarSet, TcKind, TcTyVar, TyVarDetails(..),
tcEqType, tcCmpPred,
- tcSplitRhoTy, tcSplitPredTy_maybe, tcSplitAppTy_maybe,
+ tcSplitPhiTy, tcSplitPredTy_maybe, tcSplitAppTy_maybe,
tcSplitTyConApp_maybe, tcSplitForAllTys,
tcIsTyVarTy, tcSplitSigmaTy,
- isUnLiftedType, isIPPred,
+ isUnLiftedType, isIPPred, isHoleTyVar, isTyVarTy,
mkAppTy, mkTyVarTy, mkTyVarTys,
tyVarsOfPred, getClassPredTys_maybe,
)
import qualified Type ( splitFunTys )
import Subst ( Subst, mkTopTyVarSubst, substTy )
-import Class ( Class, classArity, className )
+import Class ( Class, DefMeth(..), classArity, className, classBigSig )
import TyCon ( TyCon, mkPrimTyCon, isSynTyCon, isUnboxedTupleTyCon,
- tyConArity, tyConName, tyConKind )
+ tyConArity, tyConName, tyConKind, tyConTheta,
+ getSynTyConDefn, tyConDataCons )
+import DataCon ( DataCon, dataConWrapId, dataConName, dataConSig, dataConFieldLabels )
+import FieldLabel ( fieldLabelName, fieldLabelType )
import PrimRep ( PrimRep(VoidRep) )
-import Var ( TyVar, tyVarKind, tyVarName, isTyVar, mkTyVar, isMutTyVar )
+import Var ( TyVar, idType, idName, tyVarKind, tyVarName, isTyVar, mkTyVar, isMutTyVar )
-- others:
+import Generics ( validGenericMethodType )
import TcMonad -- TcType, amongst others
import TysWiredIn ( voidTy, listTyCon, tupleTyCon )
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
+import Name ( Name, NamedThing(..), setNameUnique,
+ mkInternalName, mkDerivedTyConOcc,
+ mkSystemTvNameEncoded,
)
import VarSet
import BasicTypes ( Boxity(Boxed) )
import CmdLineOpts ( dopt, DynFlag(..) )
import Unique ( Uniquable(..) )
import SrcLoc ( noSrcLoc )
-import Util ( nOfThem, isSingleton, equalLength )
-import ListSetOps ( removeDups )
+import Util ( nOfThem, isSingleton, equalLength, notNull )
+import ListSetOps ( equivClasses, removeDups )
import Outputable
\end{code}
newTyVar :: Kind -> NF_TcM TcTyVar
newTyVar kind
= tcGetUnique `thenNF_Tc` \ uniq ->
- tcNewMutTyVar (mkSysLocalName uniq FSLIT("t")) kind VanillaTv
+ tcNewMutTyVar (mkSystemTvNameEncoded uniq FSLIT("t")) kind VanillaTv
newTyVarTy :: Kind -> NF_TcM TcType
newTyVarTy kind
= newTyVar kind `thenNF_Tc` \ tc_tyvar ->
returnNF_Tc (TyVarTy tc_tyvar)
-newHoleTyVarTy :: NF_TcM TcType
- = tcGetUnique `thenNF_Tc` \ uniq ->
- tcNewMutTyVar (mkSysLocalName uniq FSLIT("h")) openTypeKind HoleTv `thenNF_Tc` \ tv ->
- returnNF_Tc (TyVarTy tv)
-
newTyVarTys :: Int -> Kind -> NF_TcM [TcType]
newTyVarTys n kind = mapNF_Tc newTyVarTy (nOfThem n kind)
newKindVar :: NF_TcM TcKind
newKindVar
= tcGetUnique `thenNF_Tc` \ uniq ->
- tcNewMutTyVar (mkSysLocalName uniq FSLIT("k")) superKind VanillaTv `thenNF_Tc` \ kv ->
+ tcNewMutTyVar (mkSystemTvNameEncoded uniq FSLIT("k")) superKind VanillaTv `thenNF_Tc` \ kv ->
returnNF_Tc (TyVarTy kv)
newKindVars :: Int -> NF_TcM [TcKind]
newBoxityVar :: NF_TcM TcKind
newBoxityVar
= tcGetUnique `thenNF_Tc` \ uniq ->
- tcNewMutTyVar (mkSysLocalName uniq FSLIT("bx")) superBoxity VanillaTv `thenNF_Tc` \ kv ->
+ tcNewMutTyVar (mkSystemTvNameEncoded uniq FSLIT("bx")) superBoxity VanillaTv `thenNF_Tc` \ kv ->
returnNF_Tc (TyVarTy kv)
\end{code}
%************************************************************************
%* *
-\subsection{Type instantiation}
+\subsection{'hole' type variables}
%* *
%************************************************************************
-I don't understand why this is needed
-An old comments says "No need for tcSplitForAllTyM because a type
- variable can't be instantiated to a for-all type"
-But the same is true of rho types!
-
\begin{code}
-tcSplitRhoTyM :: TcType -> NF_TcM (TcThetaType, TcType)
-tcSplitRhoTyM t
- = go t t []
- where
- -- A type variable is never instantiated to a dictionary type,
- -- so we don't need to do a tcReadVar on the "arg".
- go syn_t (FunTy arg res) ts = case tcSplitPredTy_maybe arg of
- Just pair -> go res res (pair:ts)
- Nothing -> returnNF_Tc (reverse ts, syn_t)
- go syn_t (NoteTy n t) ts = go syn_t t ts
- go syn_t (TyVarTy tv) ts = getTcTyVar tv `thenNF_Tc` \ maybe_ty ->
- case maybe_ty of
- Just ty | not (tcIsTyVarTy ty) -> go syn_t ty ts
- other -> returnNF_Tc (reverse ts, syn_t)
- go syn_t t ts = returnNF_Tc (reverse ts, syn_t)
-\end{code}
+newHoleTyVarTy :: NF_TcM TcType
+ = tcGetUnique `thenNF_Tc` \ uniq ->
+ tcNewMutTyVar (mkSystemTvNameEncoded uniq FSLIT("h")) openTypeKind HoleTv `thenNF_Tc` \ tv ->
+ returnNF_Tc (TyVarTy tv)
+readHoleResult :: TcType -> NF_TcM TcType
+-- Read the answer out of a hole, constructed by newHoleTyVarTy
+readHoleResult (TyVarTy tv)
+ = ASSERT( isHoleTyVar tv )
+ getTcTyVar tv `thenNF_Tc` \ maybe_res ->
+ case maybe_res of
+ Just ty -> returnNF_Tc ty
+ Nothing -> pprPanic "readHoleResult: empty" (ppr tv)
+readHoleResult ty = pprPanic "readHoleResult: not hole" (ppr ty)
+
+zapToType :: TcType -> NF_TcM TcType
+zapToType (TyVarTy tv)
+ | isHoleTyVar tv
+ = getTcTyVar tv `thenNF_Tc` \ maybe_res ->
+ case maybe_res of
+ Nothing -> newTyVarTy openTypeKind `thenNF_Tc` \ ty ->
+ putTcTyVar tv ty `thenNF_Tc_`
+ returnNF_Tc ty
+ Just ty -> returnNF_Tc ty -- No need to loop; we never
+ -- have chains of holes
+
+zapToType other_ty = returnNF_Tc other_ty
+\end{code}
%************************************************************************
%* *
Instantiating a bunch of type variables
\begin{code}
-tcInstTyVars :: [TyVar]
+tcInstTyVars :: TyVarDetails -> [TyVar]
-> NF_TcM ([TcTyVar], [TcType], Subst)
-tcInstTyVars tyvars
- = mapNF_Tc tcInstTyVar tyvars `thenNF_Tc` \ tc_tyvars ->
+tcInstTyVars tv_details tyvars
+ = mapNF_Tc (tcInstTyVar tv_details) tyvars `thenNF_Tc` \ tc_tyvars ->
let
tys = mkTyVarTys tc_tyvars
in
-- they cannot possibly be captured by
-- any existing for-alls. Hence mkTopTyVarSubst
-tcInstTyVar tyvar
+tcInstTyVar tv_details tyvar
= tcGetUnique `thenNF_Tc` \ uniq ->
let
name = setNameUnique (tyVarName tyvar) uniq
-- 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) VanillaTv
-
-tcInstSigTyVars :: TyVarDetails -> [TyVar] -> NF_TcM [TcTyVar]
-tcInstSigTyVars details tyvars -- Very similar to tcInstTyVar
- = tcGetUniques `thenNF_Tc` \ uniqs ->
- listTc [ ASSERT( not (kind `eqKind` openTypeKind) ) -- Shouldn't happen
- tcNewMutTyVar name kind details
- | (tyvar, uniq) <- tyvars `zip` uniqs,
- let name = setNameUnique (tyVarName tyvar) uniq,
- let kind = tyVarKind tyvar
- ]
-\end{code}
+ tcNewMutTyVar 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 -> NF_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)
- (tyvars, rho) -> tcInstTyVars tyvars `thenNF_Tc` \ (tyvars', _, tenv) ->
+ (tyvars, rho) -> tcInstTyVars tv_details tyvars `thenNF_Tc` \ (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)
-
-
-tcInstSigType :: TyVarDetails -> Type -> NF_TcM ([TcTyVar], TcThetaType, TcType)
--- Very similar to tcInstSigType, but uses signature type variables
--- Also, somewhat arbitrarily, don't deal with the monomorphic case so efficiently
-tcInstSigType tv_details poly_ty
- = let
- (tyvars, rho) = tcSplitForAllTys poly_ty
- in
- tcInstSigTyVars tv_details tyvars `thenNF_Tc` \ tyvars' ->
- -- Make *signature* type variables
-
- let
- tyvar_tys' = mkTyVarTys tyvars'
- rho' = substTy (mkTopTyVarSubst tyvars tyvar_tys') rho
- -- mkTopTyVarSubst because the tyvars' are fresh
-
- (theta', tau') = tcSplitRhoTy rho'
- -- This splitRhoTy tries hard to make sure that tau' is a type synonym
- -- wherever possible, which can improve interface files.
- in
- returnNF_Tc (tyvars', theta', tau')
\end{code}
-
%************************************************************************
%* *
\subsection{Putting and getting mutable type variables}
= tupleTyCon Boxed (length args) -- *-> ... ->*->*
| otherwise
- = pprTrace "Urk! Inventing strangely-kinded void TyCon" (ppr tc_name) $
+ = pprTrace "Urk! Inventing strangely-kinded void TyCon:" (ppr tc_name $$ ppr kind) $
mkPrimTyCon tc_name kind 0 [] VoidRep
-- Same name as the tyvar, apart from making it start with a colon (sigh)
-- I dread to think what will happen if this gets out into an
-- interface file. Catastrophe likely. Major sigh.
- tc_name = mkLocalName (getUnique tv) (mkDerivedTyConOcc (getOccName tv)) noSrcLoc
+ tc_name = mkInternalName (getUnique tv) (mkDerivedTyConOcc (getOccName tv)) noSrcLoc
-- zonkTcTyVarToTyVar is applied to the *binding* occurrence
-- of a type variable, at the *end* of type checking. It changes
-- so that all other occurrences of the tyvar will get zapped too
zonkTyVar zap tv `thenNF_Tc` \ ty2 ->
+ -- This warning shows up if the allegedly-unbound tyvar is
+ -- already bound to something. It can actually happen, and
+ -- in a harmless way (see [Silly Type Synonyms] below) so
+ -- it's only a warning
WARN( not (immut_tv_ty `tcEqType` ty2), ppr tv $$ ppr immut_tv $$ ppr ty2 )
returnNF_Tc immut_tv
\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.
+
%************************************************************************
%* *
go (AppTy fun arg) = go fun `thenNF_Tc` \ fun' ->
go arg `thenNF_Tc` \ arg' ->
returnNF_Tc (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
-- 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
check_tau_type rank ubx_tup (AppTy ty1 ty2)
= check_arg_type ty1 `thenTc_` check_arg_type ty2
-check_tau_type rank ubx_tup (NoteTy note ty)
- = check_tau_type rank ubx_tup ty
+check_tau_type rank ubx_tup (NoteTy (SynNote syn) ty)
-- Synonym notes are built only when the synonym is
-- saturated (see Type.mkSynTy)
- -- Not checking the 'note' part allows us to instantiate a synonym
- -- defn with a for-all type, but that seems OK too
+ = doptsTc Opt_GlasgowExts `thenNF_Tc` \ 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.
+ returnTc ()
+ else
+ -- For H98, do check the un-expanded part
+ check_tau_type rank ubx_tup syn
+ ) `thenTc_`
+
+ 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
+ -- synonym application, leaving it to checkValidType (i.e. right here)
-- to find the error
checkTc syn_arity_ok arity_msg `thenTc_`
mapTc_ check_arg_type tys
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}
= returnTc ()
check_valid_theta ctxt theta
= getDOptsTc `thenNF_Tc` \ dflags ->
- warnTc (not (null dups)) (dupPredWarn dups) `thenNF_Tc_`
+ warnTc (notNull dups) (dupPredWarn dups) `thenNF_Tc_`
+ -- 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.
mapTc_ (check_source_ty dflags ctxt) theta
where
(_,dups) = removeDups tcCmpPred theta
= -- 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)
+ checkTc (check_class_pred_tys dflags ctxt tys)
(predTyVarErr pred $$ how_to_allow)
where
n_tys = length tys
arity_err = arityErr "Class" class_name arity n_tys
- arby_preds_ok = case ctxt of
- InstHeadCtxt -> True -- We check for instance-head formation
- -- in checkValidInstHead
- InstThetaCtxt -> dopt Opt_AllowUndecidableInstances dflags
- other -> dopt Opt_GlasgowExts dflags
-
how_to_allow = case ctxt of
InstHeadCtxt -> empty -- Should not happen
InstThetaCtxt -> parens undecidableMsg
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
%************************************************************************
%* *
+\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) `thenTc_`
+
+ -- Check arg types of data constructors
+ mapTc_ checkValidDataCon data_cons `thenTc_`
+
+ -- Check that fields with the same name share a type
+ mapTc_ 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)) `thenTc_`
+ -- This checks the argument types and
+ -- ambiguity of the existential context (if any)
+ tcAddErrCtxt (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
+ doptsTc Opt_GlasgowExts `thenTc` \ gla_exts ->
+
+ -- Check that the class is unary, unless GlaExs
+ checkTc (notNull tyvars) (nullaryClassErr cls) `thenTc_`
+ checkTc (gla_exts || unary) (classArityErr cls) `thenTc_`
+
+ -- Check the super-classes
+ checkValidTheta (ClassSCCtxt (className cls)) theta `thenTc_`
+
+ -- Check the class operations
+ mapTc_ check_op op_stuff `thenTc_`
+
+ -- 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) `thenTc_`
+ -- The 'tail' removes the initial (C a) from the
+ -- class itself, leaving just the method type
+
+ checkValidType (FunSigCtxt op_name) tau `thenTc_`
+
+ -- 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}
%* *
%************************************************************************
projects / ghc-hetmet.git / blobdiff