\section[TcClassDcl]{Typechecking class declarations}
\begin{code}
-module TcClassDcl ( kcClassDecl, tcClassDecl1, tcClassDecls2,
+module TcClassDcl ( tcClassDecl1, tcClassDecls2, mkImplicitClassBinds,
tcMethodBind, checkFromThisClass
) where
import HsSyn ( HsDecl(..), TyClDecl(..), Sig(..), MonoBinds(..),
InPat(..), HsBinds(..), GRHSs(..),
- HsExpr(..), HsLit(..), HsType(..), pprClassAssertion,
- unguardedRHS, andMonoBinds, andMonoBindList, getTyVarName,
+ HsExpr(..), HsLit(..), HsType(..), HsPred(..),
+ mkSimpleMatch,
+ andMonoBinds, andMonoBindList,
isClassDecl, isClassOpSig, isPragSig, collectMonoBinders
)
-import HsPragmas ( ClassPragmas(..) )
import BasicTypes ( NewOrData(..), TopLevelFlag(..), RecFlag(..) )
import RnHsSyn ( RenamedTyClDecl, RenamedClassPragmas,
RenamedClassOpSig, RenamedMonoBinds,
RenamedContext, RenamedHsDecl, RenamedSig
)
-import TcHsSyn ( TcMonoBinds )
+import TcHsSyn ( TcMonoBinds, idsToMonoBinds )
import Inst ( Inst, InstOrigin(..), LIE, emptyLIE, plusLIE, plusLIEs, newDicts, newMethod )
-import TcEnv ( TcId, ValueEnv, TcTyThing(..), tcAddImportedIdInfo,
- tcLookupClass, tcLookupTy, tcExtendTyVarEnvForMeths, tcExtendGlobalTyVars,
- tcExtendLocalValEnv
+import TcEnv ( TcId, ValueEnv, TyThing(..), TyThingDetails(..), tcAddImportedIdInfo,
+ tcLookupTy, tcExtendTyVarEnvForMeths, tcExtendGlobalTyVars,
+ tcExtendLocalValEnv, tcExtendTyVarEnv, newDefaultMethodName
)
import TcBinds ( tcBindWithSigs, tcSpecSigs )
-import TcUnify ( unifyKinds )
-import TcMonad
-import TcMonoType ( tcHsType, tcHsTopType, tcExtendTopTyVarScope,
- tcContext, checkSigTyVars, sigCtxt, mkTcSig
- )
+import TcTyDecls ( mkNewTyConRep )
+import TcMonoType ( tcHsSigType, tcClassContext, checkSigTyVars, sigCtxt, mkTcSig )
import TcSimplify ( tcSimplifyAndCheck, bindInstsOfLocalFuns )
-import TcType ( TcType, TcTyVar, tcInstTyVars, zonkTcTyVarBndr, tcGetTyVar )
+import TcType ( TcType, TcTyVar, tcInstTyVars, tcGetTyVar, zonkTcSigTyVars )
+import TcInstUtil ( classDataCon )
+import TcMonad
import PrelInfo ( nO_METHOD_BINDING_ERROR_ID )
-import FieldLabel ( firstFieldLabelTag )
import Bag ( unionManyBags, bagToList )
-import Class ( mkClass, classBigSig, Class )
+import Class ( classTyVars, classBigSig, classSelIds, classTyCon, Class, ClassOpItem )
import CmdLineOpts ( opt_GlasgowExts, opt_WarnMissingMethods )
-import MkId ( mkDictSelId, mkDataConId, mkDefaultMethodId )
-import DataCon ( mkDataCon, notMarkedStrict )
-import Id ( Id, setInlinePragma, getIdUnfolding, idType, idName )
-import CoreUnfold ( unfoldingTemplate )
-import IdInfo
+import MkId ( mkDictSelId, mkDataConId, mkDataConWrapId, mkDefaultMethodId )
+import DataCon ( mkDataCon, dataConId, dataConWrapId, notMarkedStrict )
+import Id ( Id, setInlinePragma, idUnfolding, idType, idName )
import Name ( Name, nameOccName, isLocallyDefined, NamedThing(..) )
-import NameSet ( emptyNameSet )
+import NameSet ( NameSet, mkNameSet, elemNameSet, emptyNameSet )
import Outputable
-import Type ( mkFunTy, mkTyVarTy, mkTyVarTys, mkDictTy,
- mkSigmaTy, mkForAllTys, Type, ThetaType,
+import Type ( Type, ThetaType, ClassContext,
+ mkFunTy, mkTyVarTy, mkTyVarTys, mkDictTy, mkDictTys,
+ mkSigmaTy, mkClassPred, classesOfPreds,
boxedTypeKind, mkArrowKind
)
import Var ( tyVarKind, TyVar )
-import VarSet ( mkVarSet )
-import TyCon ( mkAlgTyCon )
-import Unique ( Unique, Uniquable(..) )
-import Util
+import VarSet ( mkVarSet, emptyVarSet )
+import TyCon ( AlgTyConFlavour(..), mkClassTyCon )
import Maybes ( seqMaybe )
+import SrcLoc ( SrcLoc )
import FiniteMap ( lookupWithDefaultFM )
\end{code}
%************************************************************************
%* *
-\subsection{Kind checking}
-%* *
-%************************************************************************
-
-\begin{code}
-kcClassDecl (ClassDecl context class_name
- tyvar_names class_sigs def_methods pragmas
- tycon_name datacon_name sc_sel_names src_loc)
- = -- CHECK ARITY 1 FOR HASKELL 1.4
- checkTc (opt_GlasgowExts || length tyvar_names == 1)
- (classArityErr class_name) `thenTc_`
-
- -- Get the (mutable) class kind
- tcLookupTy class_name `thenNF_Tc` \ (kind, _, _) ->
-
- -- Make suitable tyvars and do kind checking
- -- The net effect is to mutate the class kind
- tcExtendTopTyVarScope kind tyvar_names $ \ _ _ ->
- tcContext context `thenTc_`
- mapTc kc_sig the_class_sigs `thenTc_`
-
- returnTc ()
- where
- the_class_sigs = filter isClassOpSig class_sigs
-
- kc_sig (ClassOpSig _ _ op_ty loc) = tcAddSrcLoc loc (tcHsType op_ty)
-\end{code}
-
-
-%************************************************************************
-%* *
\subsection{Type checking}
%* *
%************************************************************************
\begin{code}
-tcClassDecl1 rec_env rec_inst_mapper rec_vrcs
+tcClassDecl1 :: ValueEnv -> RenamedTyClDecl -> TcM s (Name, TyThingDetails)
+tcClassDecl1 rec_env
(ClassDecl context class_name
- tyvar_names class_sigs def_methods pragmas
- tycon_name datacon_name sc_sel_names src_loc)
- = -- LOOK THINGS UP IN THE ENVIRONMENT
- tcLookupTy class_name `thenTc` \ (class_kind, _, AClass rec_class) ->
- tcExtendTopTyVarScope class_kind tyvar_names $ \ tyvars _ ->
- -- The class kind is by now immutable
+ tyvar_names fundeps class_sigs def_methods pragmas
+ tycon_name datacon_name datacon_wkr_name sc_sel_names src_loc)
+ = -- CHECK ARITY 1 FOR HASKELL 1.4
+ checkTc (opt_GlasgowExts || length tyvar_names == 1)
+ (classArityErr class_name) `thenTc_`
+
+ -- LOOK THINGS UP IN THE ENVIRONMENT
+ tcLookupTy class_name `thenTc` \ (AClass clas) ->
+ let
+ tyvars = classTyVars clas
+ dm_bndrs_w_locs = bagToList (collectMonoBinders def_methods)
+ dm_bndr_set = mkNameSet (map fst dm_bndrs_w_locs)
+ in
+ tcExtendTyVarEnv tyvars $
-- CHECK THE CONTEXT
--- traceTc (text "tcClassCtxt" <+> ppr class_name) `thenTc_`
- tcClassContext class_name rec_class tyvars context sc_sel_names
- `thenTc` \ (sc_theta, sc_tys, sc_sel_ids) ->
--- traceTc (text "tcClassCtxt done" <+> ppr class_name) `thenTc_`
+ tcSuperClasses class_name clas
+ context sc_sel_names `thenTc` \ (sc_theta, sc_sel_ids) ->
-- CHECK THE CLASS SIGNATURES,
- mapTc (tcClassSig rec_env rec_class tyvars)
- (filter isClassOpSig class_sigs)
- `thenTc` \ sig_stuff ->
+ mapTc (tcClassSig rec_env dm_bndr_set clas tyvars)
+ (filter isClassOpSig class_sigs) `thenTc` \ sig_stuff ->
- -- MAKE THE CLASS OBJECT ITSELF
+ -- MAKE THE CLASS DETAILS
let
- (op_tys, op_sel_ids, defm_ids) = unzip3 sig_stuff
- rec_class_inst_env = rec_inst_mapper rec_class
- clas = mkClass class_name tyvars
- sc_theta sc_sel_ids op_sel_ids defm_ids
- tycon
- rec_class_inst_env
-
+ (op_tys, op_items) = unzip sig_stuff
+ sc_tys = mkDictTys sc_theta
dict_component_tys = sc_tys ++ op_tys
- new_or_data = case dict_component_tys of
- [_] -> NewType
- other -> DataType
dict_con = mkDataCon datacon_name
[notMarkedStrict | _ <- dict_component_tys]
[{-No context-}]
[{-No existential tyvars-}] [{-Or context-}]
dict_component_tys
- tycon dict_con_id
-
- dict_con_id = mkDataConId dict_con
-
- argvrcs = lookupWithDefaultFM rec_vrcs (pprPanic "tcClassDecl1: argvrcs:" $
- ppr tycon_name)
- tycon_name
-
- tycon = mkAlgTyCon tycon_name
- class_kind
- tyvars
- [] -- No context
- argvrcs
- [dict_con] -- Constructors
- [] -- No derivings
- (Just clas) -- Yes! It's a dictionary
- new_or_data
- NonRecursive
+ (classTyCon clas)
+ dict_con_id dict_wrap_id
+
+ dict_con_id = mkDataConId datacon_wkr_name dict_con
+ dict_wrap_id = mkDataConWrapId dict_con
in
- returnTc clas
+ returnTc (class_name, ClassDetails sc_theta sc_sel_ids op_items dict_con)
\end{code}
-
\begin{code}
-tcClassContext :: Name -> Class -> [TyVar]
+tcSuperClasses :: Name -> Class
-> RenamedContext -- class context
-> [Name] -- Names for superclass selectors
- -> TcM s (ThetaType, -- the superclass context
- [Type], -- types of the superclass dictionaries
+ -> TcM s (ClassContext, -- the superclass context
[Id]) -- superclass selector Ids
-tcClassContext class_name rec_class rec_tyvars context sc_sel_names
+tcSuperClasses class_name clas context sc_sel_names
= -- Check the context.
-- The renamer has already checked that the context mentions
-- only the type variable of the class decl.
-- For std Haskell check that the context constrains only tyvars
(if opt_GlasgowExts then
- returnTc []
+ returnTc ()
else
- mapTc check_constraint context
+ mapTc_ check_constraint context
) `thenTc_`
- tcContext context `thenTc` \ sc_theta ->
-
+ -- Context is already kind-checked
+ tcClassContext context `thenTc` \ sc_theta ->
let
- sc_tys = [mkDictTy sc tys | (sc,tys) <- sc_theta]
- sc_sel_ids = zipWithEqual "tcClassContext" mk_super_id sc_sel_names sc_tys
+ sc_sel_ids = [mkDictSelId sc_name clas | sc_name <- sc_sel_names]
in
-- Done
- returnTc (sc_theta, sc_tys, sc_sel_ids)
+ returnTc (sc_theta, sc_sel_ids)
where
- rec_tyvar_tys = mkTyVarTys rec_tyvars
-
- mk_super_id name dict_ty
- = mkDictSelId name rec_class ty
- where
- ty = mkForAllTys rec_tyvars $
- mkFunTy (mkDictTy rec_class rec_tyvar_tys) dict_ty
-
- check_constraint (c, tys) = checkTc (all is_tyvar tys)
- (superClassErr class_name (c, tys))
+ check_constraint sc@(HsPClass c tys)
+ = checkTc (all is_tyvar tys) (superClassErr class_name sc)
- is_tyvar (MonoTyVar _) = True
- is_tyvar other = False
+ is_tyvar (HsTyVar _) = True
+ is_tyvar other = False
tcClassSig :: ValueEnv -- Knot tying only!
+ -> NameSet -- Names bound in the default-method bindings
-> Class -- ...ditto...
-> [TyVar] -- The class type variable, used for error check only
-> RenamedClassOpSig
-> TcM s (Type, -- Type of the method
- Id, -- selector id
- Maybe Id) -- default-method ids
+ ClassOpItem) -- Selector Id, default-method Id, True if explicit default binding
-tcClassSig rec_env rec_clas rec_clas_tyvars
- (ClassOpSig op_name maybe_dm_name
- op_ty
- src_loc)
+
+tcClassSig rec_env dm_bind_names clas clas_tyvars
+ (ClassOpSig op_name maybe_dm_stuff op_ty src_loc)
= tcAddSrcLoc src_loc $
-- Check the type signature. NB that the envt *already has*
-- NB: Renamer checks that the class type variable is mentioned in local_ty,
-- and that it is not constrained by theta
--- traceTc (text "tcClassSig" <+> ppr op_name) `thenTc_`
- tcHsTopType op_ty `thenTc` \ local_ty ->
+ tcHsSigType op_ty `thenTc` \ local_ty ->
let
- global_ty = mkSigmaTy rec_clas_tyvars
- [(rec_clas, mkTyVarTys rec_clas_tyvars)]
+ global_ty = mkSigmaTy clas_tyvars
+ [mkClassPred clas (mkTyVarTys clas_tyvars)]
local_ty
-- Build the selector id and default method id
- sel_id = mkDictSelId op_name rec_clas global_ty
- maybe_dm_id = case maybe_dm_name of
- Nothing -> Nothing
- Just dm_name -> let
- dm_id = mkDefaultMethodId dm_name rec_clas global_ty
- in
- Just (tcAddImportedIdInfo rec_env dm_id)
+ sel_id = mkDictSelId op_name clas
in
--- traceTc (text "tcClassSig done" <+> ppr op_name) `thenTc_`
- returnTc (local_ty, sel_id, maybe_dm_id)
+ (case maybe_dm_stuff of
+ Nothing -> -- Source-file class declaration
+ newDefaultMethodName op_name src_loc `thenNF_Tc` \ dm_name ->
+ returnNF_Tc (mkDefaultMethodId dm_name clas global_ty, op_name `elemNameSet` dm_bind_names)
+
+ Just (dm_name, explicit_dm) -> -- Interface-file class decl
+ let
+ dm_id = mkDefaultMethodId dm_name clas global_ty
+ in
+ returnNF_Tc (tcAddImportedIdInfo rec_env dm_id, explicit_dm)
+ ) `thenNF_Tc` \ (dm_id, explicit_dm) ->
+
+ returnTc (local_ty, (sel_id, dm_id, explicit_dm))
\end{code}
-> NF_TcM s (LIE, TcMonoBinds)
tcClassDecl2 (ClassDecl context class_name
- tyvar_names class_sigs default_binds pragmas _ _ _ src_loc)
+ tyvar_names _ class_sigs default_binds pragmas _ _ _ _ src_loc)
| not (isLocallyDefined class_name)
= returnNF_Tc (emptyLIE, EmptyMonoBinds)
| otherwise -- It is locally defined
= recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $
tcAddSrcLoc src_loc $
+ tcLookupTy class_name `thenNF_Tc` \ (AClass clas) ->
+ tcDefaultMethodBinds clas default_binds class_sigs
+\end{code}
- -- Get the relevant class
- tcLookupClass class_name `thenNF_Tc` \ clas ->
- let
- (tyvars, sc_theta, sc_sel_ids, op_sel_ids, defm_ids) = classBigSig clas
-
+\begin{code}
+mkImplicitClassBinds :: [Class] -> NF_TcM s ([Id], TcMonoBinds)
+mkImplicitClassBinds classes
+ = returnNF_Tc (concat cls_ids_s, andMonoBindList binds_s)
-- The selector binds are already in the selector Id's unfoldings
- sel_binds = [ CoreMonoBind sel_id (unfoldingTemplate (getIdUnfolding sel_id))
- | sel_id <- sc_sel_ids ++ op_sel_ids
- ]
- in
- -- Generate bindings for the default methods
- tcDefaultMethodBinds clas default_binds class_sigs `thenTc` \ (const_insts, meth_binds) ->
+ -- We don't return the data constructor etc from the class,
+ -- because that's done via the class's TyCon
+ where
+ (cls_ids_s, binds_s) = unzip (map mk_implicit classes)
- returnTc (const_insts,
- meth_binds `AndMonoBinds` andMonoBindList sel_binds)
+ mk_implicit clas = (sel_ids, binds)
+ where
+ sel_ids = classSelIds clas
+ binds | isLocallyDefined clas = idsToMonoBinds sel_ids
+ | otherwise = EmptyMonoBinds
\end{code}
%************************************************************************
tcDefaultMethodBinds clas default_binds sigs
= -- Check that the default bindings come from this class
- checkFromThisClass clas op_sel_ids default_binds `thenNF_Tc_`
+ checkFromThisClass clas default_binds `thenNF_Tc_`
-- Do each default method separately
- mapAndUnzipTc tc_dm sel_ids_w_dms `thenTc` \ (defm_binds, const_lies) ->
+ -- For Hugs compatibility we make a default-method for every
+ -- class op, regardless of whether or not the programmer supplied an
+ -- explicit default decl for the class. GHC will actually never
+ -- call the default method for such operations, because it'll whip up
+ -- a more-informative default method at each instance decl.
+ mapAndUnzipTc tc_dm op_items `thenTc` \ (defm_binds, const_lies) ->
returnTc (plusLIEs const_lies, andMonoBindList defm_binds)
where
prags = filter isPragSig sigs
- (tyvars, sc_theta, sc_sel_ids, op_sel_ids, defm_ids) = classBigSig clas
-
- sel_ids_w_dms = [pair | pair@(_, Just _) <- op_sel_ids `zip` defm_ids]
- -- Just the ones for which there is an explicit
- -- user default declaration
+ (tyvars, _, _, op_items) = classBigSig clas
origin = ClassDeclOrigin
-- And since ds is big, it doesn't get inlined, so we don't get good
-- default methods. Better to make separate AbsBinds for each
- tc_dm sel_id_w_dm@(_, Just dm_id)
+ tc_dm op_item@(_, dm_id, _)
= tcInstTyVars tyvars `thenNF_Tc` \ (clas_tyvars, inst_tys, _) ->
let
- theta = [(clas,inst_tys)]
+ theta = [(mkClassPred clas inst_tys)]
in
newDicts origin theta `thenNF_Tc` \ (this_dict, [this_dict_id]) ->
let
tcExtendTyVarEnvForMeths tyvars clas_tyvars (
tcMethodBind clas origin clas_tyvars inst_tys theta
default_binds prags False
- sel_id_w_dm
+ op_item
) `thenTc` \ (defm_bind, insts_needed, (_, local_dm_id)) ->
tcAddErrCtxt (defltMethCtxt clas) $
-- tcMethodBind has checked that the class_tyvars havn't
-- been unified with each other or another type, but we must
-- still zonk them before passing them to tcSimplifyAndCheck
- mapNF_Tc zonkTcTyVarBndr clas_tyvars `thenNF_Tc` \ clas_tyvars' ->
+ zonkTcSigTyVars clas_tyvars `thenNF_Tc` \ clas_tyvars' ->
-- Check the context
tcSimplifyAndCheck
\end{code}
\begin{code}
-checkFromThisClass :: Class -> [Id] -> RenamedMonoBinds -> NF_TcM s ()
-checkFromThisClass clas op_sel_ids mono_binds
- = mapNF_Tc check_from_this_class bndrs `thenNF_Tc_`
+checkFromThisClass :: Class -> RenamedMonoBinds -> NF_TcM s ()
+checkFromThisClass clas mbinds
+ = mapNF_Tc check_from_this_class bndrs_w_locs `thenNF_Tc_`
returnNF_Tc ()
where
check_from_this_class (bndr, loc)
| nameOccName bndr `elem` sel_names = returnNF_Tc ()
| otherwise = tcAddSrcLoc loc $
addErrTc (badMethodErr bndr clas)
- sel_names = map getOccName op_sel_ids
- bndrs = bagToList (collectMonoBinders mono_binds)
+ sel_names = map getOccName (classSelIds clas)
+ bndrs_w_locs = bagToList (collectMonoBinders mbinds)
\end{code}
-- the caller; here, it's just used for the error message
-> RenamedMonoBinds -- Method binding (pick the right one from in here)
-> [RenamedSig] -- Pramgas (just for this one)
- -> Bool -- True <=> supply default decl if no explicit decl
- -- This is true for instance decls,
- -- false for class decls
- -> (Id, Maybe Id) -- The method selector and default-method Id
+ -> Bool -- True <=> This method is from an instance declaration
+ -> ClassOpItem -- The method selector and default-method Id
-> TcM s (TcMonoBinds, LIE, (LIE, TcId))
tcMethodBind clas origin inst_tyvars inst_tys inst_theta
- meth_binds prags supply_default_bind
- (sel_id, maybe_dm_id)
+ meth_binds prags is_inst_decl
+ (sel_id, dm_id, explicit_dm)
= tcGetSrcLoc `thenNF_Tc` \ loc ->
newMethod origin sel_id inst_tys `thenNF_Tc` \ meth@(_, meth_id) ->
maybe_user_bind = find_bind meth_name meth_binds
no_user_bind = case maybe_user_bind of {Nothing -> True; other -> False}
- no_user_default = case maybe_dm_id of {Nothing -> True; other -> False}
meth_bind = case maybe_user_bind of
Just bind -> bind
in
-- Warn if no method binding, only if -fwarn-missing-methods
- if no_user_bind && not supply_default_bind then
- pprPanic "tcMethodBind" (ppr clas <+> ppr inst_tys)
- else
- warnTc (opt_WarnMissingMethods && no_user_bind && no_user_default)
+ warnTc (is_inst_decl && opt_WarnMissingMethods && no_user_bind && not explicit_dm)
(omittedMethodWarn sel_id clas) `thenNF_Tc_`
-- Check the bindings; first add inst_tyvars to the envt
-- Now check that the instance type variables
-- (or, in the case of a class decl, the class tyvars)
-- have not been unified with anything in the environment
- tcAddErrCtxtM (sigCtxt sig_msg (mkSigmaTy inst_tyvars inst_theta (idType meth_id))) $
- checkSigTyVars inst_tyvars `thenTc_`
+ --
+ -- We do this for each method independently to localise error messages
+ tcAddErrCtxtM (sigCtxt sig_msg inst_tyvars inst_theta (idType meth_id)) $
+ checkSigTyVars inst_tyvars emptyVarSet `thenTc_`
returnTc (binds `AndMonoBinds` prag_binds1 `AndMonoBinds` prag_binds2,
insts `plusLIE` prag_lie',
meth)
where
- sig_msg ty = sep [ptext SLIT("When checking the expected type for"),
- nest 4 (ppr sel_name <+> dcolon <+> ppr ty)]
+ sig_msg = ptext SLIT("When checking the expected type for class method") <+> ppr sel_name
sel_name = idName sel_id
-- but we must use the method name; so we substitute it here. Crude but simple.
find_bind meth_name (FunMonoBind op_name fix matches loc)
| op_name == sel_name = Just (FunMonoBind meth_name fix matches loc)
- find_bind meth_name (PatMonoBind (VarPatIn op_name) grhss loc)
- | op_name == sel_name = Just (PatMonoBind (VarPatIn meth_name) grhss loc)
find_bind meth_name (AndMonoBinds b1 b2)
= find_bind meth_name b1 `seqMaybe` find_bind meth_name b2
find_bind meth_name other = Nothing -- Default case
find_prags meth_name (prag:prags) = find_prags meth_name prags
mk_default_bind local_meth_name loc
- = PatMonoBind (VarPatIn local_meth_name)
- (GRHSs (unguardedRHS (default_expr loc) loc) EmptyBinds Nothing)
+ = FunMonoBind local_meth_name
+ False -- Not infix decl
+ [mkSimpleMatch [] (default_expr loc) Nothing loc]
loc
default_expr loc
- = case maybe_dm_id of
- Just dm_id -> HsVar (getName dm_id) -- There's a default method
- Nothing -> error_expr loc -- No default method
+ | explicit_dm = HsVar (getName dm_id) -- There's a default method
+ | otherwise = error_expr loc -- No default method
error_expr loc = HsApp (HsVar (getName nO_METHOD_BINDING_ERROR_ID))
(HsLit (HsString (_PK_ (error_msg loc))))
= ptext SLIT("Too many parameters for class") <+> quotes (ppr class_name)
superClassErr class_name sc
- = ptext SLIT("Illegal superclass constraint") <+> quotes (pprClassAssertion sc)
+ = ptext SLIT("Illegal superclass constraint") <+> quotes (ppr sc)
<+> ptext SLIT("in declaration for class") <+> quotes (ppr class_name)
defltMethCtxt class_name
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