\section[TcClassDcl]{Typechecking class declarations}
\begin{code}
-module TcClassDcl ( kcClassDecl, tcClassDecl1, tcClassDecls2, mkImplicitClassBinds,
- tcMethodBind, checkFromThisClass
+module TcClassDcl ( tcClassDecl1, checkValidClass, tcClassDecls2,
+ tcMethodBind, badMethodErr
) where
#include "HsVersions.h"
-import HsSyn ( HsDecl(..), TyClDecl(..), Sig(..), MonoBinds(..),
- InPat(..), HsBinds(..), GRHSs(..),
- HsExpr(..), HsLit(..), HsType(..), HsPred(..),
- mkSimpleMatch,
- andMonoBinds, andMonoBindList, getTyVarName,
- isClassDecl, isClassOpSig, isPragSig, collectMonoBinders
+import HsSyn ( TyClDecl(..), Sig(..), MonoBinds(..),
+ HsExpr(..), HsLit(..),
+ mkSimpleMatch, andMonoBinds, andMonoBindList,
+ isClassOpSig, isPragSig,
+ getClassDeclSysNames, placeHolderType
)
-import HsPragmas ( ClassPragmas(..) )
-import BasicTypes ( NewOrData(..), TopLevelFlag(..), RecFlag(..) )
-import RnHsSyn ( RenamedTyClDecl, RenamedClassPragmas,
+import BasicTypes ( TopLevelFlag(..), RecFlag(..), StrictnessMark(..) )
+import RnHsSyn ( RenamedTyClDecl,
RenamedClassOpSig, RenamedMonoBinds,
- RenamedContext, RenamedHsDecl, RenamedSig
+ RenamedSig, maybeGenericMatch
)
-import TcHsSyn ( TcMonoBinds, idsToMonoBinds )
+import TcHsSyn ( TcMonoBinds )
-import Inst ( Inst, InstOrigin(..), LIE, emptyLIE, plusLIE, plusLIEs, newDicts, newMethod )
-import TcEnv ( TcId, ValueEnv, TcTyThing(..), tcAddImportedIdInfo,
- tcLookupTy, tcExtendTyVarEnvForMeths, tcExtendGlobalTyVars,
- tcExtendLocalValEnv
+import Inst ( Inst, InstOrigin(..), LIE, emptyLIE, plusLIE, plusLIEs,
+ instToId, newDicts, newMethod )
+import TcEnv ( RecTcEnv, TyThingDetails(..), tcAddImportedIdInfo,
+ tcLookupClass, tcExtendTyVarEnvForMeths, tcExtendGlobalTyVars,
+ tcExtendLocalValEnv, tcExtendTyVarEnv
)
import TcBinds ( tcBindWithSigs, tcSpecSigs )
-import TcTyDecls ( mkNewTyConRep )
-import TcUnify ( unifyKinds )
-import TcMonad
-import TcMonoType ( kcHsType, tcHsTopType, tcExtendTopTyVarScope,
- tcContext, checkSigTyVars, sigCtxt, mkTcSig
+import TcMonoType ( tcHsType, tcHsTheta, checkSigTyVars, sigCtxt, mkTcSig )
+import TcSimplify ( tcSimplifyCheck, bindInstsOfLocalFuns )
+import TcMType ( tcInstSigTyVars, checkValidTheta, checkValidType, SourceTyCtxt(..), UserTypeCtxt(..) )
+import TcType ( Type, TyVarDetails(..), TcType, TcThetaType, TcTyVar,
+ mkSigmaTy, mkTyVarTys, mkPredTys, mkClassPred,
+ tcIsTyVarTy, tcSplitTyConApp_maybe, tcSplitSigmaTy
)
-import TcSimplify ( tcSimplifyAndCheck, bindInstsOfLocalFuns )
-import TcType ( TcType, TcTyVar, tcInstTyVars, zonkTcTyVarBndr, tcGetTyVar )
-import TcInstUtil ( classDataCon )
+import TcMonad
+import Generics ( mkGenericRhs, validGenericMethodType )
import PrelInfo ( nO_METHOD_BINDING_ERROR_ID )
-import FieldLabel ( firstFieldLabelTag )
-import Bag ( unionManyBags, bagToList )
-import Class ( mkClass, classBigSig, classSelIds, Class, ClassOpItem )
-import CmdLineOpts ( opt_GlasgowExts, opt_WarnMissingMethods )
+import Class ( classTyVars, classBigSig, classTyCon, className,
+ Class, ClassOpItem, DefMeth (..) )
import MkId ( mkDictSelId, mkDataConId, mkDataConWrapId, mkDefaultMethodId )
-import DataCon ( mkDataCon, dataConId, dataConWrapId, notMarkedStrict )
-import Id ( Id, setInlinePragma, idUnfolding, idType, idName )
-import CoreUnfold ( unfoldingTemplate )
-import IdInfo
-import Name ( Name, nameOccName, isLocallyDefined, NamedThing(..) )
+import DataCon ( mkDataCon )
+import Id ( Id, idType, idName, setIdLocalExported )
+import Module ( Module )
+import Name ( Name, NamedThing(..) )
+import NameEnv ( NameEnv, lookupNameEnv, emptyNameEnv, unitNameEnv, plusNameEnv )
import NameSet ( emptyNameSet )
import Outputable
-import Type ( Type, ThetaType, ClassContext,
- mkFunTy, mkTyVarTy, mkTyVarTys, mkDictTy, mkDictTys,
- mkSigmaTy, mkForAllTys, mkClassPred, classesOfPreds,
- boxedTypeKind, mkArrowKind
- )
-import Var ( tyVarKind, TyVar )
+import Var ( TyVar )
import VarSet ( mkVarSet, emptyVarSet )
-import TyCon ( AlgTyConFlavour(..), mkClassTyCon )
-import Unique ( Unique, Uniquable(..) )
-import Util
-import Maybes ( seqMaybe )
-import FiniteMap ( lookupWithDefaultFM )
+import CmdLineOpts
+import ErrUtils ( dumpIfSet )
+import Util ( count, isSingleton, lengthIs, equalLength )
+import Maybes ( seqMaybe, maybeToBool )
\end{code}
%************************************************************************
%* *
-\subsection{Kind checking}
-%* *
-%************************************************************************
-
-\begin{code}
-kcClassDecl (ClassDecl context class_name
- tyvar_names fundeps class_sigs def_methods pragmas
- _ _ _ _ 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 (kcHsType op_ty)
-\end{code}
-
-
-%************************************************************************
-%* *
\subsection{Type checking}
%* *
%************************************************************************
\begin{code}
-tcClassDecl1 rec_env rec_inst_mapper rec_vrcs
- (ClassDecl context class_name
- tyvar_names fundeps class_sigs def_methods pragmas
- tycon_name datacon_name datacon_wkr_name sc_sel_names src_loc)
+
+tcClassDecl1 :: RecTcEnv -> RenamedTyClDecl -> TcM (Name, TyThingDetails)
+tcClassDecl1 rec_env
+ (ClassDecl {tcdCtxt = context, tcdName = class_name,
+ tcdTyVars = tyvar_names, tcdFDs = fundeps,
+ tcdSigs = class_sigs, tcdMeths = def_methods,
+ tcdSysNames = sys_names, tcdLoc = src_loc})
= -- LOOK THINGS UP IN THE ENVIRONMENT
- tcLookupTy class_name `thenTc` \ (class_kind, AClass rec_class arity) ->
- tcExtendTopTyVarScope class_kind tyvar_names $ \ tyvars _ ->
- -- The class kind is by now immutable
+ tcLookupClass class_name `thenTc` \ clas ->
+ let
+ tyvars = classTyVars clas
+ op_sigs = filter isClassOpSig class_sigs
+ op_names = [n | ClassOpSig n _ _ _ <- op_sigs]
+ (_, datacon_name, datacon_wkr_name, sc_sel_names) = getClassDeclSysNames sys_names
+ in
+ tcExtendTyVarEnv tyvars $
+
+ checkDefaultBinds clas op_names def_methods `thenTc` \ mb_dm_env ->
-- 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_`
-
- -- CHECK THE FUNCTIONAL DEPENDENCIES,
- tcFundeps fundeps `thenTc` \ fds ->
+ -- The renamer has already checked that the context mentions
+ -- only the type variable of the class decl.
+ -- Context is already kind-checked
+ ASSERT( equalLength context sc_sel_names )
+ tcHsTheta context `thenTc` \ sc_theta ->
-- CHECK THE CLASS SIGNATURES,
- mapTc (tcClassSig rec_env rec_class tyvars)
- (filter isClassOpSig class_sigs)
- `thenTc` \ sig_stuff ->
+ mapTc (tcClassSig rec_env clas tyvars mb_dm_env) op_sigs `thenTc` \ sig_stuff ->
- -- MAKE THE CLASS OBJECT ITSELF
+ -- MAKE THE CLASS DETAILS
let
(op_tys, op_items) = unzip sig_stuff
- rec_class_inst_env = rec_inst_mapper rec_class
- clas = mkClass class_name tyvars fds
- sc_theta sc_sel_ids op_items
- tycon
- rec_class_inst_env
-
+ sc_tys = mkPredTys sc_theta
dict_component_tys = sc_tys ++ op_tys
- new_or_data = case dict_component_tys of
- [_] -> NewTyCon (mkNewTyConRep tycon)
- other -> DataTyCon
+ sc_sel_ids = [mkDictSelId sc_name clas | sc_name <- sc_sel_names]
dict_con = mkDataCon datacon_name
- [notMarkedStrict | _ <- dict_component_tys]
- [{- No labelled fields -}]
- tyvars
- [{-No context-}]
- [{-No existential tyvars-}] [{-Or context-}]
- dict_component_tys
- tycon dict_con_id dict_wrap_id
+ [NotMarkedStrict | _ <- dict_component_tys]
+ [{- No labelled fields -}]
+ tyvars
+ [{-No context-}]
+ [{-No existential tyvars-}] [{-Or context-}]
+ dict_component_tys
+ (classTyCon clas)
+ dict_con_id dict_wrap_id
dict_con_id = mkDataConId datacon_wkr_name dict_con
dict_wrap_id = mkDataConWrapId dict_con
-
- argvrcs = lookupWithDefaultFM rec_vrcs (pprPanic "tcClassDecl1: argvrcs:" $
- ppr tycon_name)
- tycon_name
-
- tycon = mkClassTyCon tycon_name
- class_kind
- tyvars
- argvrcs
- dict_con -- Constructors
- clas -- Yes! It's a dictionary
- new_or_data
in
- returnTc (class_name, AClass clas arity)
-\end{code}
-
-\begin{code}
-tcFundeps = mapTc tc_fundep
-tc_fundep (us, vs) =
- mapTc tc_fd_tyvar us `thenTc` \ us' ->
- mapTc tc_fd_tyvar vs `thenTc` \ vs' ->
- returnTc (us', vs')
-tc_fd_tyvar v =
- tcLookupTy v `thenTc` \(_, ATyVar tv) ->
- returnTc tv
+ returnTc (class_name, ClassDetails sc_theta sc_sel_ids op_items dict_con)
\end{code}
\begin{code}
-tcClassContext :: Name -> Class -> [TyVar]
- -> RenamedContext -- class context
- -> [Name] -- Names for superclass selectors
- -> TcM s (ClassContext, -- the superclass context
- [Type], -- types of the superclass dictionaries
- [Id]) -- superclass selector Ids
-
-tcClassContext class_name rec_class rec_tyvars context sc_sel_names
- = -- Check the context.
- -- The renamer has already checked that the context mentions
- -- only the type variable of the class decl.
+checkDefaultBinds :: Class -> [Name] -> Maybe RenamedMonoBinds
+ -> TcM (Maybe (NameEnv Bool))
+ -- The returned environment says
+ -- x not in env => no default method
+ -- x -> True => generic default method
+ -- x -> False => polymorphic default method
+
+ -- Check default bindings
+ -- a) must be for a class op for this class
+ -- b) must be all generic or all non-generic
+ -- and return a mapping from class-op to DefMeth info
+
+ -- But do all this only for source binds
+
+checkDefaultBinds clas ops Nothing
+ = returnTc Nothing
+
+checkDefaultBinds clas ops (Just mbs)
+ = go mbs `thenTc` \ dm_env ->
+ returnTc (Just dm_env)
+ where
+ go EmptyMonoBinds = returnTc emptyNameEnv
- -- For std Haskell check that the context constrains only tyvars
- (if opt_GlasgowExts then
- returnTc []
- else
- mapTc check_constraint context
- ) `thenTc_`
+ go (AndMonoBinds b1 b2)
+ = go b1 `thenTc` \ dm_info1 ->
+ go b2 `thenTc` \ dm_info2 ->
+ returnTc (dm_info1 `plusNameEnv` dm_info2)
- tcContext context `thenTc` \ sc_theta ->
+ go (FunMonoBind op _ matches loc)
+ = tcAddSrcLoc loc $
- let
- sc_theta' = classesOfPreds sc_theta
- sc_tys = mkDictTys sc_theta'
- sc_sel_ids = [mkDictSelId sc_name rec_class | sc_name <- sc_sel_names]
- in
- -- Done
- returnTc (sc_theta', sc_tys, sc_sel_ids)
+ -- Check that the op is from this class
+ checkTc (op `elem` ops) (badMethodErr clas op) `thenTc_`
- where
- check_constraint sc@(HsPClass c tys) = checkTc (all is_tyvar tys)
- (superClassErr class_name sc)
+ -- Check that all the defns ar generic, or none are
+ checkTc (all_generic || none_generic) (mixedGenericErr op) `thenTc_`
- is_tyvar (HsTyVar _) = True
- is_tyvar other = False
+ returnTc (unitNameEnv op all_generic)
+ where
+ n_generic = count (maybeToBool . maybeGenericMatch) matches
+ none_generic = n_generic == 0
+ all_generic = matches `lengthIs` n_generic
+\end{code}
-tcClassSig :: ValueEnv -- Knot tying only!
+\begin{code}
+tcClassSig :: RecTcEnv -- Knot tying only!
-> Class -- ...ditto...
-> [TyVar] -- The class type variable, used for error check only
+ -> Maybe (NameEnv Bool) -- Info about default methods;
+ -- Nothing => imported class defn with no method binds
-> RenamedClassOpSig
- -> TcM s (Type, -- Type of the method
+ -> TcM (Type, -- Type of the method
ClassOpItem) -- Selector Id, default-method Id, True if explicit default binding
+-- This warrants an explanation: we need to separate generic
+-- default methods and default methods later on in the compiler
+-- so we distinguish them in checkDefaultBinds, and pass this knowledge in the
+-- Class.DefMeth data structure.
-tcClassSig rec_env rec_clas rec_clas_tyvars
- (ClassOpSig op_name dm_name explicit_dm
- op_ty src_loc)
+tcClassSig unf_env clas clas_tyvars maybe_dm_env
+ (ClassOpSig op_name sig_dm op_ty src_loc)
= tcAddSrcLoc src_loc $
-- Check the type signature. NB that the envt *already has*
-- bindings for the type variables; see comments in TcTyAndClassDcls.
+ tcHsType op_ty `thenTc` \ local_ty ->
- -- 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 ->
let
- global_ty = mkSigmaTy rec_clas_tyvars
- [mkClassPred rec_clas (mkTyVarTys rec_clas_tyvars)]
- local_ty
+ theta = [mkClassPred clas (mkTyVarTys clas_tyvars)]
-- Build the selector id and default method id
- sel_id = mkDictSelId op_name rec_clas
- dm_id = mkDefaultMethodId dm_name rec_clas global_ty
- final_dm_id = tcAddImportedIdInfo rec_env dm_id
- in
--- traceTc (text "tcClassSig done" <+> ppr op_name) `thenTc_`
- returnTc (local_ty, (sel_id, final_dm_id, explicit_dm))
-\end{code}
-
-
-%************************************************************************
-%* *
-\subsection[ClassDcl-pass2]{Class decls pass 2: default methods}
-%* *
-%************************************************************************
+ sel_id = mkDictSelId op_name clas
+ DefMeth dm_name = sig_dm
-The purpose of pass 2 is
-\begin{enumerate}
-\item
-to beat on the explicitly-provided default-method decls (if any),
-using them to produce a complete set of default-method decls.
-(Omitted ones elicit an error message.)
-\item
-to produce a definition for the selector function for each method
-and superclass dictionary.
-\end{enumerate}
+ dm_info = case maybe_dm_env of
+ Nothing -> sig_dm
+ Just dm_env -> mk_src_dm_info dm_env
-Pass~2 only applies to locally-defined class declarations.
-
-The function @tcClassDecls2@ just arranges to apply @tcClassDecl2@ to
-each local class decl.
-
-\begin{code}
-tcClassDecls2 :: [RenamedHsDecl]
- -> NF_TcM s (LIE, TcMonoBinds)
-
-tcClassDecls2 decls
- = foldr combine
- (returnNF_Tc (emptyLIE, EmptyMonoBinds))
- [tcClassDecl2 cls_decl | TyClD cls_decl <- decls, isClassDecl cls_decl]
- where
- combine tc1 tc2 = tc1 `thenNF_Tc` \ (lie1, binds1) ->
- tc2 `thenNF_Tc` \ (lie2, binds2) ->
- returnNF_Tc (lie1 `plusLIE` lie2,
- binds1 `AndMonoBinds` binds2)
+ mk_src_dm_info dm_env = case lookupNameEnv dm_env op_name of
+ Nothing -> NoDefMeth
+ Just True -> GenDefMeth
+ Just False -> DefMeth dm_name
+ in
+ returnTc (local_ty, (sel_id, dm_info))
\end{code}
-@tcClassDecl2@ is the business end of things.
+checkValidClass is called once the mutually-recursive knot has been
+tied, so we can look at things freely.
\begin{code}
-tcClassDecl2 :: RenamedTyClDecl -- The class declaration
- -> NF_TcM s (LIE, TcMonoBinds)
+checkValidClass :: Class -> TcM ()
+checkValidClass cls
+ = -- CHECK ARITY 1 FOR HASKELL 1.4
+ doptsTc Opt_GlasgowExts `thenTc` \ gla_exts ->
-tcClassDecl2 (ClassDecl context class_name
- tyvar_names _ class_sigs default_binds pragmas _ _ _ _ src_loc)
+ -- Check that the class is unary, unless GlaExs
+ checkTc (not (null tyvars)) (nullaryClassErr cls) `thenTc_`
+ checkTc (gla_exts || unary) (classArityErr cls) `thenTc_`
- | not (isLocallyDefined class_name)
- = returnNF_Tc (emptyLIE, EmptyMonoBinds)
+ -- Check the super-classes
+ checkValidTheta (ClassSCCtxt (className cls)) theta `thenTc_`
- | 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}
+ -- Check the class operations
+ mapTc_ check_op op_stuff `thenTc_`
-\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
- where
- (cls_ids_s, binds_s) = unzip (map mk_implicit classes)
+ -- 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)
- mk_implicit clas = (all_cls_ids, binds)
- where
- dict_con = classDataCon clas
- all_cls_ids = dataConId dict_con : cls_ids
- cls_ids = dataConWrapId dict_con : classSelIds clas
-
- -- The wrapper and selectors get bindings, the worker does not
- binds | isLocallyDefined clas = idsToMonoBinds cls_ids
- | otherwise = EmptyMonoBinds
+ 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
\end{code}
+
%************************************************************************
%* *
\subsection[Default methods]{Default methods}
dfoo_list
\end{verbatim}
+The function @tcClassDecls2@ just arranges to apply @tcClassDecl2@ to
+each local class decl.
+
\begin{code}
-tcDefaultMethodBinds
- :: Class
- -> RenamedMonoBinds
- -> [RenamedSig]
- -> TcM s (LIE, TcMonoBinds)
-
-tcDefaultMethodBinds clas default_binds sigs
- = -- Check that the default bindings come from this class
- checkFromThisClass clas op_items default_binds `thenNF_Tc_`
-
- -- Do each default method separately
- -- 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)
+tcClassDecls2 :: Module -> [RenamedTyClDecl] -> NF_TcM (LIE, TcMonoBinds, [Id])
+
+tcClassDecls2 this_mod decls
+ = foldr combine
+ (returnNF_Tc (emptyLIE, EmptyMonoBinds, []))
+ [tcClassDecl2 cls_decl | cls_decl@(ClassDecl {tcdMeths = Just _}) <- decls]
+ -- The 'Just' picks out source ClassDecls
where
- prags = filter isPragSig sigs
+ combine tc1 tc2 = tc1 `thenNF_Tc` \ (lie1, binds1, ids1) ->
+ tc2 `thenNF_Tc` \ (lie2, binds2, ids2) ->
+ returnNF_Tc (lie1 `plusLIE` lie2,
+ binds1 `AndMonoBinds` binds2,
+ ids1 ++ ids2)
+\end{code}
- (tyvars, _, _, op_items) = classBigSig clas
+@tcClassDecl2@ generates bindings for polymorphic default methods
+(generic default methods have by now turned into instance declarations)
- origin = ClassDeclOrigin
+\begin{code}
+tcClassDecl2 :: RenamedTyClDecl -- The class declaration
+ -> NF_TcM (LIE, TcMonoBinds, [Id])
- -- We make a separate binding for each default method.
- -- At one time I used a single AbsBinds for all of them, thus
- -- AbsBind [d] [dm1, dm2, dm3] { dm1 = ...; dm2 = ...; dm3 = ... }
- -- But that desugars into
- -- ds = \d -> (..., ..., ...)
- -- dm1 = \d -> case ds d of (a,b,c) -> a
- -- 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 op_item@(_, dm_id, _)
- = tcInstTyVars tyvars `thenNF_Tc` \ (clas_tyvars, inst_tys, _) ->
- let
- theta = [(mkClassPred clas inst_tys)]
- in
- newDicts origin theta `thenNF_Tc` \ (this_dict, [this_dict_id]) ->
- let
- avail_insts = this_dict
- in
- tcExtendTyVarEnvForMeths tyvars clas_tyvars (
- tcMethodBind clas origin clas_tyvars inst_tys theta
- default_binds prags False
- op_item
- ) `thenTc` \ (defm_bind, insts_needed, (_, local_dm_id)) ->
+tcClassDecl2 (ClassDecl {tcdName = class_name, tcdSigs = sigs,
+ tcdMeths = Just default_binds, tcdLoc = src_loc})
+ = -- The 'Just' picks out source ClassDecls
+ recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds, [])) $
+ tcAddSrcLoc src_loc $
+ tcLookupClass class_name `thenNF_Tc` \ clas ->
+
+ -- We make a separate binding for each default method.
+ -- At one time I used a single AbsBinds for all of them, thus
+ -- AbsBind [d] [dm1, dm2, dm3] { dm1 = ...; dm2 = ...; dm3 = ... }
+ -- But that desugars into
+ -- ds = \d -> (..., ..., ...)
+ -- dm1 = \d -> case ds d of (a,b,c) -> a
+ -- 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
+ let
+ (tyvars, _, _, op_items) = classBigSig clas
+ prags = filter isPragSig sigs
+ tc_dm = tcDefMeth clas tyvars default_binds prags
+ in
+ mapAndUnzip3Tc tc_dm op_items `thenTc` \ (defm_binds, const_lies, dm_ids_s) ->
+
+ returnTc (plusLIEs const_lies, andMonoBindList defm_binds, concat dm_ids_s)
- tcAddErrCtxt (defltMethCtxt clas) $
+
+tcDefMeth clas tyvars binds_in prags (_, NoDefMeth) = returnTc (EmptyMonoBinds, emptyLIE, [])
+tcDefMeth clas tyvars binds_in prags (_, GenDefMeth) = returnTc (EmptyMonoBinds, emptyLIE, [])
+ -- Generate code for polymorphic default methods only
+ -- (Generic default methods have turned into instance decls by now.)
+ -- This is incompatible with Hugs, which expects a polymorphic
+ -- default method for every class op, regardless of whether or not
+ -- the programmer supplied an explicit default decl for the class.
+ -- (If necessary we can fix that, but we don't have a convenient Id to hand.)
+
+tcDefMeth clas tyvars binds_in prags op_item@(sel_id, DefMeth dm_name)
+ = tcInstSigTyVars ClsTv tyvars `thenNF_Tc` \ clas_tyvars ->
+ let
+ dm_ty = idType sel_id -- Same as dict selector!
+ -- The default method's type should really come from the
+ -- iface file, since it could be usage-generalised, but this
+ -- requires altering the mess of knots in TcModule and I'm
+ -- too scared to do that. Instead, I have disabled generalisation
+ -- of types of default methods (and dict funs) by annotating them
+ -- TyGenNever (in MkId). Ugh! KSW 1999-09.
+
+ inst_tys = mkTyVarTys clas_tyvars
+ theta = [mkClassPred clas inst_tys]
+ dm_id = mkDefaultMethodId dm_name dm_ty
+ local_dm_id = setIdLocalExported dm_id
+ -- Reason for setIdLocalExported: see notes with MkId.mkDictFunId
+ in
+ newDicts origin theta `thenNF_Tc` \ [this_dict] ->
+
+ tcExtendTyVarEnvForMeths tyvars clas_tyvars (
+ tcMethodBind clas origin clas_tyvars inst_tys theta
+ binds_in prags False op_item
+ ) `thenTc` \ (defm_bind, insts_needed, local_dm_inst) ->
- -- 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' ->
+ tcAddErrCtxt (defltMethCtxt clas) $
- -- Check the context
- tcSimplifyAndCheck
- (ptext SLIT("class") <+> ppr clas)
- (mkVarSet clas_tyvars')
- avail_insts
- insts_needed `thenTc` \ (const_lie, dict_binds) ->
+ -- Check the context
+ tcSimplifyCheck
+ (ptext SLIT("class") <+> ppr clas)
+ clas_tyvars
+ [this_dict]
+ insts_needed `thenTc` \ (const_lie, dict_binds) ->
+
+ -- Simplification can do unification
+ checkSigTyVars clas_tyvars emptyVarSet `thenTc` \ clas_tyvars' ->
- let
- full_bind = AbsBinds
- clas_tyvars'
- [this_dict_id]
- [(clas_tyvars', dm_id, local_dm_id)]
- emptyNameSet -- No inlines (yet)
- (dict_binds `andMonoBinds` defm_bind)
- in
- returnTc (full_bind, const_lie)
-\end{code}
-
-\begin{code}
-checkFromThisClass :: Class -> [ClassOpItem] -> RenamedMonoBinds -> NF_TcM s ()
-checkFromThisClass clas op_items mono_binds
- = mapNF_Tc check_from_this_class bndrs `thenNF_Tc_`
- returnNF_Tc ()
+ let
+ full_bind = AbsBinds
+ clas_tyvars'
+ [instToId this_dict]
+ [(clas_tyvars', local_dm_id, instToId local_dm_inst)]
+ emptyNameSet -- No inlines (yet)
+ (dict_binds `andMonoBinds` defm_bind)
+ in
+ returnTc (full_bind, const_lie, [dm_id])
where
- check_from_this_class (bndr, loc)
- | nameOccName bndr `elem` sel_names = returnNF_Tc ()
- | otherwise = tcAddSrcLoc loc $
- addErrTc (badMethodErr bndr clas)
- sel_names = [getOccName sel_id | (sel_id,_,_) <- op_items]
- bndrs = bagToList (collectMonoBinders mono_binds)
+ origin = ClassDeclOrigin
\end{code}
+
+%************************************************************************
+%* *
+\subsection{Typechecking a method}
+%* *
+%************************************************************************
+
@tcMethodBind@ is used to type-check both default-method and
instance-decl method declarations. We must type-check methods one at a
time, because their signatures may have different contexts and
-> [RenamedSig] -- Pramgas (just for this one)
-> Bool -- True <=> This method is from an instance declaration
-> ClassOpItem -- The method selector and default-method Id
- -> TcM s (TcMonoBinds, LIE, (LIE, TcId))
+ -> TcM (TcMonoBinds, LIE, Inst)
tcMethodBind clas origin inst_tyvars inst_tys inst_theta
- 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) ->
- mkTcSig meth_id loc `thenNF_Tc` \ sig_info ->
-
- let
- meth_name = idName meth_id
- maybe_user_bind = find_bind meth_name meth_binds
-
- no_user_bind = case maybe_user_bind of {Nothing -> True; other -> False}
-
- meth_bind = case maybe_user_bind of
- Just bind -> bind
- Nothing -> mk_default_bind meth_name loc
-
- meth_prags = find_prags meth_name prags
- in
-
- -- Warn if no method binding, only if -fwarn-missing-methods
- 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
- -- so that we don't quantify over them in nested places
- -- The *caller* put the class/inst decl tyvars into the envt
- tcExtendGlobalTyVars (mkVarSet inst_tyvars) (
- tcAddErrCtxt (methodCtxt sel_id) $
- tcBindWithSigs NotTopLevel meth_bind
- [sig_info] meth_prags NonRecursive
- ) `thenTc` \ (binds, insts, _) ->
-
-
- tcExtendLocalValEnv [(meth_name, meth_id)] (
- tcSpecSigs meth_prags
- ) `thenTc` \ (prag_binds1, prag_lie) ->
-
- -- The prag_lie for a SPECIALISE pragma will mention the function
- -- itself, so we have to simplify them away right now lest they float
- -- outwards!
- bindInstsOfLocalFuns prag_lie [meth_id] `thenTc` \ (prag_lie', prag_binds2) ->
-
-
- -- 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 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 = ptext SLIT("When checking the expected type for class method") <+> ppr sel_name
-
- sel_name = idName sel_id
-
- -- The renamer just puts the selector ID as the binder in the method binding
- -- 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 (AndMonoBinds b1 b2)
- = find_bind meth_name b1 `seqMaybe` find_bind meth_name b2
- find_bind meth_name other = Nothing -- Default case
-
-
- -- Find the prags for this method, and replace the
- -- selector name with the method name
- find_prags meth_name [] = []
- find_prags meth_name (SpecSig name ty loc : prags)
- | name == sel_name = SpecSig meth_name ty loc : find_prags meth_name prags
- find_prags meth_name (InlineSig name phase loc : prags)
- | name == sel_name = InlineSig meth_name phase loc : find_prags meth_name prags
- find_prags meth_name (NoInlineSig name phase loc : prags)
- | name == sel_name = NoInlineSig meth_name phase loc : find_prags meth_name prags
- find_prags meth_name (prag:prags) = find_prags meth_name prags
-
- mk_default_bind local_meth_name loc
- = FunMonoBind local_meth_name
- False -- Not infix decl
- [mkSimpleMatch [] (default_expr loc) Nothing loc]
- loc
-
- default_expr loc
- | 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))))
-
- error_msg loc = showSDoc (hcat [ppr loc, text "|", ppr sel_id ])
+ meth_binds prags is_inst_decl (sel_id, dm_info)
+ = tcGetSrcLoc `thenNF_Tc` \ loc ->
+ newMethod origin sel_id inst_tys `thenNF_Tc` \ meth ->
+ let
+ meth_id = instToId meth
+ meth_name = idName meth_id
+ sig_msg = ptext SLIT("When checking the expected type for class method") <+> ppr sel_id
+ meth_prags = find_prags (idName sel_id) meth_name prags
+ in
+ mkTcSig meth_id loc `thenNF_Tc` \ sig_info ->
+
+ -- Figure out what method binding to use
+ -- If the user suppplied one, use it, else construct a default one
+ (case find_bind (idName sel_id) meth_name meth_binds of
+ Just user_bind -> returnTc user_bind
+ Nothing -> mkDefMethRhs is_inst_decl clas inst_tys sel_id loc dm_info `thenTc` \ rhs ->
+ returnTc (FunMonoBind meth_name False -- Not infix decl
+ [mkSimpleMatch [] rhs placeHolderType loc] loc)
+ ) `thenTc` \ meth_bind ->
+ -- Check the bindings; first add inst_tyvars to the envt
+ -- so that we don't quantify over them in nested places
+ -- The *caller* put the class/inst decl tyvars into the envt
+ tcExtendGlobalTyVars (mkVarSet inst_tyvars)
+ (tcAddErrCtxt (methodCtxt sel_id) $
+ tcBindWithSigs NotTopLevel meth_bind
+ [sig_info] meth_prags NonRecursive
+ ) `thenTc` \ (binds, insts, _) ->
+
+ tcExtendLocalValEnv [(meth_name, meth_id)]
+ (tcSpecSigs meth_prags) `thenTc` \ (prag_binds1, prag_lie) ->
+
+ -- The prag_lie for a SPECIALISE pragma will mention the function
+ -- itself, so we have to simplify them away right now lest they float
+ -- outwards!
+ bindInstsOfLocalFuns prag_lie [meth_id] `thenTc` \ (prag_lie', prag_binds2) ->
+
+ -- 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
+ --
+ -- We do this for each method independently to localise error messages
+ -- ...and this is why the call to tcExtendGlobalTyVars must be here
+ -- rather than in the caller
+ 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)
+
+ -- The user didn't supply a method binding,
+ -- so we have to make up a default binding
+ -- The RHS of a default method depends on the default-method info
+mkDefMethRhs is_inst_decl clas inst_tys sel_id loc (DefMeth dm_name)
+ = -- An polymorphic default method
+ returnTc (HsVar dm_name)
+
+mkDefMethRhs is_inst_decl clas inst_tys sel_id loc NoDefMeth
+ = -- No default method
+ -- Warn only if -fwarn-missing-methods
+ doptsTc Opt_WarnMissingMethods `thenNF_Tc` \ warn ->
+ warnTc (is_inst_decl && warn)
+ (omittedMethodWarn sel_id) `thenNF_Tc_`
+ returnTc error_rhs
+ where
+ error_rhs = HsApp (HsVar (getName nO_METHOD_BINDING_ERROR_ID))
+ (HsLit (HsString (_PK_ error_msg)))
+ error_msg = showSDoc (hcat [ppr loc, text "|", ppr sel_id ])
+
+
+mkDefMethRhs is_inst_decl clas inst_tys sel_id loc GenDefMeth
+ = -- A generic default method
+ -- If the method is defined generically, we can only do the job if the
+ -- instance declaration is for a single-parameter type class with
+ -- a type constructor applied to type arguments in the instance decl
+ -- (checkTc, so False provokes the error)
+ checkTc (not is_inst_decl || simple_inst)
+ (badGenericInstance sel_id) `thenTc_`
+
+ ioToTc (dumpIfSet opt_PprStyle_Debug "Generic RHS" stuff) `thenNF_Tc_`
+ returnTc rhs
+ where
+ rhs = mkGenericRhs sel_id clas_tyvar tycon
+
+ stuff = vcat [ppr clas <+> ppr inst_tys,
+ nest 4 (ppr sel_id <+> equals <+> ppr rhs)]
+
+ -- The tycon is only used in the generic case, and in that
+ -- case we require that the instance decl is for a single-parameter
+ -- type class with type variable arguments:
+ -- instance (...) => C (T a b)
+ simple_inst = maybeToBool maybe_tycon
+ clas_tyvar = head (classTyVars clas)
+ Just tycon = maybe_tycon
+ maybe_tycon = case inst_tys of
+ [ty] -> case tcSplitTyConApp_maybe ty of
+ Just (tycon, arg_tys) | all tcIsTyVarTy arg_tys -> Just tycon
+ other -> Nothing
+ other -> Nothing
\end{code}
+
+\begin{code}
+-- The renamer just puts the selector ID as the binder in the method binding
+-- but we must use the method name; so we substitute it here. Crude but simple.
+find_bind sel_name meth_name (FunMonoBind op_name fix matches loc)
+ | op_name == sel_name = Just (FunMonoBind meth_name fix matches loc)
+find_bind sel_name meth_name (AndMonoBinds b1 b2)
+ = find_bind sel_name meth_name b1 `seqMaybe` find_bind sel_name meth_name b2
+find_bind sel_name meth_name other = Nothing -- Default case
+
+ -- Find the prags for this method, and replace the
+ -- selector name with the method name
+find_prags sel_name meth_name [] = []
+find_prags sel_name meth_name (SpecSig name ty loc : prags)
+ | name == sel_name = SpecSig meth_name ty loc : find_prags sel_name meth_name prags
+find_prags sel_name meth_name (InlineSig sense name phase loc : prags)
+ | name == sel_name = InlineSig sense meth_name phase loc : find_prags sel_name meth_name prags
+find_prags sel_name meth_name (prag:prags) = find_prags sel_name meth_name prags
+\end{code}
+
+
Contexts and errors
~~~~~~~~~~~~~~~~~~~
\begin{code}
-classArityErr class_name
- = ptext SLIT("Too many parameters for class") <+> quotes (ppr class_name)
+nullaryClassErr cls
+ = ptext SLIT("No parameters for class") <+> quotes (ppr cls)
-superClassErr class_name sc
- = ptext SLIT("Illegal superclass constraint") <+> quotes (ppr sc)
- <+> ptext SLIT("in declaration for class") <+> quotes (ppr class_name)
+classArityErr cls
+ = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
+ parens (ptext SLIT("Use -fglasgow-exts to allow multi-parameter classes"))]
-defltMethCtxt class_name
- = ptext SLIT("When checking the default methods for class") <+> quotes (ppr class_name)
+defltMethCtxt clas
+ = ptext SLIT("When checking the default methods for class") <+> quotes (ppr clas)
methodCtxt sel_id
= ptext SLIT("In the definition for method") <+> quotes (ppr sel_id)
-badMethodErr bndr clas
+badMethodErr clas op
= hsep [ptext SLIT("Class"), quotes (ppr clas),
- ptext SLIT("does not have a method"), quotes (ppr bndr)]
+ ptext SLIT("does not have a method"), quotes (ppr op)]
+
+omittedMethodWarn sel_id
+ = ptext SLIT("No explicit method nor default method for") <+> quotes (ppr sel_id)
+
+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")])
+
+badGenericInstance sel_id
+ = sep [ptext SLIT("Can't derive generic code for") <+> quotes (ppr sel_id),
+ ptext SLIT("because the instance declaration is not for a simple type (T a b c)"),
+ ptext SLIT("(where T is a derivable type constructor)")]
+
+mixedGenericErr op
+ = ptext SLIT("Can't mix generic and non-generic equations for class method") <+> quotes (ppr op)
-omittedMethodWarn sel_id clas
- = sep [ptext SLIT("No explicit method nor default method for") <+> quotes (ppr sel_id),
- ptext SLIT("in an instance declaration for") <+> quotes (ppr clas)]
+genericMultiParamErr clas
+ = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+>
+ ptext SLIT("cannot have generic methods")
\end{code}
projects / ghc-hetmet.git / blobdiff