\section[TcClassDcl]{Typechecking class declarations}
\begin{code}
-module TcClassDcl ( tcClassDecl1, tcClassDecls2, mkImplicitClassBinds,
- tcMethodBind, checkFromThisClass
+module TcClassDcl ( tcClassDecl1, tcClassDecls2,
+ MethodSpec, tcMethodBind, mkMethodBind, badMethodErr
) where
#include "HsVersions.h"
-import HsSyn ( HsDecl(..), TyClDecl(..), Sig(..), MonoBinds(..),
- InPat(..), HsBinds(..), GRHSs(..),
- HsExpr(..), HsLit(..), HsType(..), HsPred(..),
- mkSimpleMatch,
- andMonoBinds, andMonoBindList,
- isClassDecl, isClassOpSig, isPragSig, collectMonoBinders
+import HsSyn ( TyClDecl(..), Sig(..), MonoBinds(..),
+ HsExpr(..), HsLit(..), Pat(WildPat),
+ mkSimpleMatch, andMonoBinds, andMonoBindList,
+ isClassOpSig, isPragSig,
+ placeHolderType
)
-import BasicTypes ( NewOrData(..), TopLevelFlag(..), RecFlag(..) )
-import RnHsSyn ( RenamedTyClDecl, RenamedClassPragmas,
+import BasicTypes ( RecFlag(..), StrictnessMark(..) )
+import RnHsSyn ( RenamedTyClDecl, RenamedSig,
RenamedClassOpSig, RenamedMonoBinds,
- RenamedContext, RenamedHsDecl, RenamedSig
+ maybeGenericMatch
)
-import TcHsSyn ( TcMonoBinds, idsToMonoBinds )
+import RnEnv ( lookupSysName )
+import TcHsSyn ( TcMonoBinds )
-import Inst ( Inst, InstOrigin(..), LIE, emptyLIE, plusLIE, plusLIEs, newDicts, newMethod )
-import TcEnv ( TcId, ValueEnv, TyThing(..), TyThingDetails(..), tcAddImportedIdInfo,
- tcLookupTy, tcExtendTyVarEnvForMeths, tcExtendGlobalTyVars,
- tcExtendLocalValEnv, tcExtendTyVarEnv, newDefaultMethodName
+import Inst ( Inst, InstOrigin(..), instToId, newDicts, newMethod )
+import TcEnv ( TyThingDetails(..),
+ tcLookupClass, tcExtendTyVarEnv2,
+ tcExtendTyVarEnv
)
-import TcBinds ( tcBindWithSigs, tcSpecSigs )
-import TcTyDecls ( mkNewTyConRep )
-import TcMonoType ( tcHsSigType, tcClassContext, checkSigTyVars, sigCtxt, mkTcSig )
-import TcSimplify ( tcSimplifyAndCheck, bindInstsOfLocalFuns )
-import TcType ( TcType, TcTyVar, tcInstTyVars, tcGetTyVar, zonkTcSigTyVars )
-import TcInstUtil ( classDataCon )
-import TcMonad
+import TcBinds ( tcMonoBinds )
+import TcMonoType ( TcSigInfo(..), tcHsType, tcHsTheta, mkTcSig )
+import TcSimplify ( tcSimplifyCheck )
+import TcUnify ( checkSigTyVars, sigCtxt )
+import TcMType ( tcInstTyVars )
+import TcType ( Type, TyVarDetails(..), TcType, TcThetaType, TcTyVar,
+ mkTyVarTys, mkPredTys, mkClassPred, tcSplitSigmaTy, tcSplitFunTys,
+ tcIsTyVarTy, tcSplitTyConApp_maybe, tcSplitForAllTys, tcSplitPhiTy,
+ getClassPredTys_maybe, mkPhiTy
+ )
+import TcRnMonad
+import Generics ( mkGenericRhs )
import PrelInfo ( nO_METHOD_BINDING_ERROR_ID )
-import Bag ( unionManyBags, bagToList )
-import Class ( classTyVars, classBigSig, classSelIds, classTyCon, Class, ClassOpItem )
-import CmdLineOpts ( opt_GlasgowExts, opt_WarnMissingMethods )
+import Class ( classTyVars, classBigSig, classTyCon,
+ Class, ClassOpItem, DefMeth (..) )
+import TyCon ( tyConGenInfo )
+import Subst ( substTyWith )
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 ( NameSet, mkNameSet, elemNameSet, emptyNameSet )
+import DataCon ( mkDataCon )
+import Id ( Id, idType, idName, mkUserLocal, setIdLocalExported, setInlinePragma )
+import Name ( Name, NamedThing(..) )
+import NameEnv ( NameEnv, lookupNameEnv, emptyNameEnv, unitNameEnv, plusNameEnv )
+import NameSet ( emptyNameSet, unitNameSet )
+import OccName ( mkClassTyConOcc, mkClassDataConOcc, mkWorkerOcc,
+ mkSuperDictSelOcc, reportIfUnused )
import Outputable
-import Type ( Type, ThetaType, ClassContext,
- mkFunTy, mkTyVarTy, mkTyVarTys, mkDictTy, mkDictTys,
- mkSigmaTy, mkClassPred, classesOfPreds,
- boxedTypeKind, mkArrowKind
- )
-import Var ( tyVarKind, TyVar )
-import VarSet ( mkVarSet, emptyVarSet )
-import TyCon ( AlgTyConFlavour(..), mkClassTyCon )
+import Var ( TyVar )
+import CmdLineOpts
+import UnicodeUtil ( stringToUtf8 )
+import ErrUtils ( dumpIfSet )
+import Util ( count, lengthIs, isSingleton )
import Maybes ( seqMaybe )
-import SrcLoc ( SrcLoc )
-import FiniteMap ( lookupWithDefaultFM )
+import Maybe ( isJust )
+import FastString
\end{code}
%************************************************************************
\begin{code}
-tcClassDecl1 :: ValueEnv -> RenamedTyClDecl -> TcM s (Name, TyThingDetails)
-tcClassDecl1 rec_env
- (ClassDecl context class_name
- 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) ->
+
+tcClassDecl1 :: RenamedTyClDecl -> TcM (Name, TyThingDetails)
+tcClassDecl1 (ClassDecl {tcdCtxt = context, tcdName = class_name,
+ tcdTyVars = tyvar_names, tcdFDs = fundeps,
+ tcdSigs = class_sigs, tcdMeths = def_methods,
+ tcdLoc = src_loc})
+ = -- LOOK THINGS UP IN THE ENVIRONMENT
+ tcLookupClass class_name `thenM` \ clas ->
let
- tyvars = classTyVars clas
- dm_bndrs_w_locs = bagToList (collectMonoBinders def_methods)
- dm_bndr_set = mkNameSet (map fst dm_bndrs_w_locs)
+ tyvars = classTyVars clas
+ op_sigs = filter isClassOpSig class_sigs
+ op_names = [n | ClassOpSig n _ _ _ <- op_sigs]
in
- tcExtendTyVarEnv tyvars $
+ tcExtendTyVarEnv tyvars $
+
+ checkDefaultBinds clas op_names def_methods `thenM` \ mb_dm_env ->
-- CHECK THE CONTEXT
- tcSuperClasses class_name clas
- context sc_sel_names `thenTc` \ (sc_theta, sc_sel_ids) ->
+ -- The renamer has already checked that the context mentions
+ -- only the type variable of the class decl.
+ -- Context is already kind-checked
+ tcHsTheta context `thenM` \ sc_theta ->
-- CHECK THE CLASS SIGNATURES,
- mapTc (tcClassSig rec_env dm_bndr_set clas tyvars)
- (filter isClassOpSig class_sigs) `thenTc` \ sig_stuff ->
+ mappM (tcClassSig clas tyvars mb_dm_env) op_sigs `thenM` \ sig_stuff ->
-- MAKE THE CLASS DETAILS
+ lookupSysName class_name mkClassDataConOcc `thenM` \ datacon_name ->
+ lookupSysName datacon_name mkWorkerOcc `thenM` \ datacon_wkr_name ->
+ mapM (lookupSysName class_name . mkSuperDictSelOcc)
+ [1..length context] `thenM` \ sc_sel_names ->
+ -- We number off the superclass selectors, 1, 2, 3 etc so that we
+ -- can construct names for the selectors. Thus
+ -- class (C a, C b) => D a b where ...
+ -- gives superclass selectors
+ -- D_sc1, D_sc2
+ -- (We used to call them D_C, but now we can have two different
+ -- superclasses both called C!)
+ lookupSysName class_name mkClassTyConOcc `thenM` \ tycon_name ->
let
(op_tys, op_items) = unzip sig_stuff
- sc_tys = mkDictTys sc_theta
+ sc_tys = mkPredTys sc_theta
dict_component_tys = sc_tys ++ op_tys
+ 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
- (classTyCon clas)
- 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
in
- returnTc (class_name, ClassDetails sc_theta sc_sel_ids op_items dict_con)
+ returnM (class_name, ClassDetails sc_theta sc_sel_ids op_items dict_con tycon_name)
\end{code}
\begin{code}
-tcSuperClasses :: Name -> Class
- -> RenamedContext -- class context
- -> [Name] -- Names for superclass selectors
- -> TcM s (ClassContext, -- the superclass context
- [Id]) -- superclass selector Ids
-
-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.
+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
+ = returnM Nothing
+
+checkDefaultBinds clas ops (Just mbs)
+ = go mbs `thenM` \ dm_env ->
+ returnM (Just dm_env)
+ where
+ go EmptyMonoBinds = returnM 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 `thenM` \ dm_info1 ->
+ go b2 `thenM` \ dm_info2 ->
+ returnM (dm_info1 `plusNameEnv` dm_info2)
- -- Context is already kind-checked
- tcClassContext context `thenTc` \ sc_theta ->
- let
- sc_sel_ids = [mkDictSelId sc_name clas | sc_name <- sc_sel_names]
- in
- -- Done
- returnTc (sc_theta, sc_sel_ids)
+ go (FunMonoBind op _ matches loc)
+ = addSrcLoc loc $
- where
- check_constraint sc@(HsPClass c tys)
- = checkTc (all is_tyvar tys) (superClassErr class_name sc)
+ -- Check that the op is from this class
+ checkTc (op `elem` ops) (badMethodErr clas op) `thenM_`
+
+ -- Check that all the defns ar generic, or none are
+ checkTc (all_generic || none_generic) (mixedGenericErr op) `thenM_`
- is_tyvar (HsTyVar _) = True
- is_tyvar other = False
+ returnM (unitNameEnv op all_generic)
+ where
+ n_generic = count (isJust . maybeGenericMatch) matches
+ none_generic = n_generic == 0
+ all_generic = matches `lengthIs` n_generic
+\end{code}
-tcClassSig :: ValueEnv -- Knot tying only!
- -> NameSet -- Names bound in the default-method bindings
- -> Class -- ...ditto...
+\begin{code}
+tcClassSig :: 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 dm_bind_names clas clas_tyvars
- (ClassOpSig op_name maybe_dm_stuff op_ty src_loc)
- = tcAddSrcLoc src_loc $
+tcClassSig clas clas_tyvars maybe_dm_env
+ (ClassOpSig op_name sig_dm op_ty src_loc)
+ = addSrcLoc src_loc $
-- Check the type signature. NB that the envt *already has*
-- bindings for the type variables; see comments in TcTyAndClassDcls.
+ tcHsType op_ty `thenM` \ local_ty ->
- -- NB: Renamer checks that the class type variable is mentioned in local_ty,
- -- and that it is not constrained by theta
- tcHsSigType op_ty `thenTc` \ local_ty ->
let
- global_ty = mkSigmaTy clas_tyvars
- [mkClassPred clas (mkTyVarTys clas_tyvars)]
- local_ty
+ theta = [mkClassPred clas (mkTyVarTys clas_tyvars)]
-- Build the selector id and default method id
- sel_id = mkDictSelId op_name clas
- in
- (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}
-
-
-%************************************************************************
-%* *
-\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)
-\end{code}
-
-@tcClassDecl2@ is the business end of things.
-
-\begin{code}
-tcClassDecl2 :: RenamedTyClDecl -- The class declaration
- -> NF_TcM s (LIE, TcMonoBinds)
-
-tcClassDecl2 (ClassDecl context class_name
- 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
+ mk_src_dm_info dm_env = case lookupNameEnv dm_env op_name of
+ Nothing -> NoDefMeth
+ Just True -> GenDefMeth
+ Just False -> DefMeth dm_name
+ in
+ returnM (local_ty, (sel_id, dm_info))
\end{code}
-\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
- -- 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)
-
- mk_implicit clas = (sel_ids, binds)
- where
- sel_ids = classSelIds clas
- binds | isLocallyDefined clas = idsToMonoBinds sel_ids
- | otherwise = EmptyMonoBinds
-\end{code}
%************************************************************************
%* *
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 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 :: [RenamedTyClDecl] -> TcM (TcMonoBinds, [Id])
+
+tcClassDecls2 decls
+ = foldr combine
+ (returnM (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 `thenM` \ (binds1, ids1) ->
+ tc2 `thenM` \ (binds2, ids2) ->
+ returnM (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
+ -> TcM (TcMonoBinds, [Id])
+
+tcClassDecl2 (ClassDecl {tcdName = class_name, tcdSigs = sigs,
+ tcdMeths = Just default_binds, tcdLoc = src_loc})
+ = -- The 'Just' picks out source ClassDecls
+ recoverM (returnM (EmptyMonoBinds, [])) $
+ addSrcLoc src_loc $
+ tcLookupClass class_name `thenM` \ 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
+ mapAndUnzipM tc_dm op_items `thenM` \ (defm_binds, dm_ids_s) ->
- -- 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)) ->
+ returnM (andMonoBindList defm_binds, concat dm_ids_s)
- tcAddErrCtxt (defltMethCtxt clas) $
+
+tcDefMeth clas tyvars binds_in prags (_, NoDefMeth) = returnM (EmptyMonoBinds, [])
+tcDefMeth clas tyvars binds_in prags (_, GenDefMeth) = returnM (EmptyMonoBinds, [])
+ -- 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)
+ = tcInstTyVars ClsTv tyvars `thenM` \ (clas_tyvars, inst_tys, _) ->
+ 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.
+
+ theta = [mkClassPred clas inst_tys]
+ local_dm_id = mkDefaultMethodId dm_name dm_ty
+ xtve = tyvars `zip` clas_tyvars
+ in
+ newDicts origin theta `thenM` \ [this_dict] ->
+
+ mkMethodBind origin clas inst_tys binds_in op_item `thenM` \ (_, meth_info) ->
+ getLIE (tcMethodBind xtve clas_tyvars theta
+ [this_dict] prags meth_info) `thenM` \ (defm_bind, insts_needed) ->
- -- 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
- zonkTcSigTyVars clas_tyvars `thenNF_Tc` \ clas_tyvars' ->
+ addErrCtxt (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 `thenM` \ dict_binds ->
+
+ -- Simplification can do unification
+ checkSigTyVars clas_tyvars `thenM` \ 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 -> RenamedMonoBinds -> NF_TcM s ()
-checkFromThisClass clas mbinds
- = mapNF_Tc check_from_this_class bndrs_w_locs `thenNF_Tc_`
- returnNF_Tc ()
+ let
+ (_,dm_inst_id,_) = meth_info
+ full_bind = AbsBinds
+ clas_tyvars'
+ [instToId this_dict]
+ [(clas_tyvars', local_dm_id, dm_inst_id)]
+ emptyNameSet -- No inlines (yet)
+ (dict_binds `andMonoBinds` defm_bind)
+ in
+ returnM (full_bind, [local_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 = map getOccName (classSelIds clas)
- bndrs_w_locs = bagToList (collectMonoBinders mbinds)
+ 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
tyvar sets.
\begin{code}
+type MethodSpec = (Id, -- Global selector Id
+ Id, -- Local Id (class tyvars instantiated)
+ RenamedMonoBinds) -- Binding for the method
+
tcMethodBind
- :: Class
- -> InstOrigin
+ :: [(TyVar,TcTyVar)] -- Bindings for type environment
-> [TcTyVar] -- Instantiated type variables for the
- -- enclosing class/instance decl.
- -- They'll be signature tyvars, and we
- -- want to check that they don't get bound
- -> [TcType] -- Instance types
- -> TcThetaType -- Available theta; this could be used to check
- -- the method signature, but actually that's done by
- -- 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 <=> 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 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
+ -- enclosing class/instance decl.
+ -- They'll be signature tyvars, and we
+ -- want to check that they don't get bound
+ -- Always equal the range of the type envt
+ -> TcThetaType -- Available theta; it's just used for the error message
+ -> [Inst] -- Available from context, used to simplify constraints
+ -- from the method body
+ -> [RenamedSig] -- Pragmas (e.g. inline pragmas)
+ -> MethodSpec -- Details of this method
+ -> TcM TcMonoBinds
+
+tcMethodBind xtve inst_tyvars inst_theta avail_insts prags
+ (sel_id, meth_id, meth_bind)
+ = -- Check the bindings; first adding 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) ->
+ mkTcSig meth_id `thenM` \ meth_sig ->
+
+ tcExtendTyVarEnv2 xtve (
+ addErrCtxt (methodCtxt sel_id) $
+ getLIE (tcMonoBinds meth_bind [meth_sig] NonRecursive)
+ ) `thenM` \ ((meth_bind, _, _), meth_lie) ->
+
+ -- Now do context reduction. We simplify wrt both the local tyvars
+ -- and the ones of the class/instance decl, so that there is
+ -- no problem with
+ -- class C a where
+ -- op :: Eq a => a -> b -> a
+ --
+ -- We do this for each method independently to localise error messages
- -- 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) ->
+ let
+ TySigInfo meth_id meth_tvs meth_theta _ local_meth_id _ _ = meth_sig
+ in
+ addErrCtxtM (sigCtxt sel_id inst_tyvars inst_theta (idType meth_id)) $
+ newDicts SignatureOrigin meth_theta `thenM` \ meth_dicts ->
+ let
+ all_tyvars = meth_tvs ++ inst_tyvars
+ all_insts = avail_insts ++ meth_dicts
+ in
+ tcSimplifyCheck
+ (ptext SLIT("class or instance method") <+> quotes (ppr sel_id))
+ all_tyvars all_insts meth_lie `thenM` \ lie_binds ->
+
+ checkSigTyVars all_tyvars `thenM` \ all_tyvars' ->
+
+ let
+ -- Attach inline pragmas as appropriate
+ (final_meth_id, inlines)
+ | (InlineSig inl _ phase _ : _) <- filter is_inline prags
+ = (meth_id `setInlinePragma` phase,
+ if inl then unitNameSet (idName meth_id) else emptyNameSet)
+ | otherwise
+ = (meth_id, emptyNameSet)
+
+ is_inline (InlineSig _ name _ _) = name == idName sel_id
+ is_inline other = False
+
+ meth_tvs' = take (length meth_tvs) all_tyvars'
+ poly_meth_bind = AbsBinds meth_tvs'
+ (map instToId meth_dicts)
+ [(meth_tvs', final_meth_id, local_meth_id)]
+ inlines
+ (lie_binds `andMonoBinds` meth_bind)
+ in
+ returnM poly_meth_bind
+
+
+mkMethodBind :: InstOrigin
+ -> Class -> [TcType] -- Class and instance types
+ -> RenamedMonoBinds -- Method binding (pick the right one from in here)
+ -> ClassOpItem
+ -> TcM (Maybe Inst, -- Method inst
+ MethodSpec)
+-- Find the binding for the specified method, or make
+-- up a suitable default method if it isn't there
+
+mkMethodBind origin clas inst_tys meth_binds (sel_id, dm_info)
+ = mkMethId origin clas sel_id inst_tys `thenM` \ (mb_inst, meth_id) ->
+ let
+ meth_name = idName meth_id
+ in
+ -- Figure out what method binding to use
+ -- If the user suppplied one, use it, else construct a default one
+ getSrcLocM `thenM` \ loc ->
+ (case find_bind (idName sel_id) meth_name meth_binds of
+ Just user_bind -> returnM user_bind
+ Nothing -> mkDefMethRhs origin clas inst_tys sel_id loc dm_info `thenM` \ rhs ->
+ returnM (FunMonoBind meth_name False -- Not infix decl
+ [mkSimpleMatch [] rhs placeHolderType loc] loc)
+ ) `thenM` \ meth_bind ->
+
+ returnM (mb_inst, (sel_id, meth_id, meth_bind))
+
+mkMethId :: InstOrigin -> Class
+ -> Id -> [TcType] -- Selector, and instance types
+ -> TcM (Maybe Inst, Id)
+
+-- mkMethId instantiates the selector Id at the specified types
+-- THe
+mkMethId origin clas sel_id inst_tys
+ = let
+ (tyvars,rho) = tcSplitForAllTys (idType sel_id)
+ rho_ty = ASSERT( length tyvars == length inst_tys )
+ substTyWith tyvars inst_tys rho
+ (preds,tau) = tcSplitPhiTy rho_ty
+ first_pred = head preds
+ in
+ -- The first predicate should be of form (C a b)
+ -- where C is the class in question
+ ASSERT( not (null preds) &&
+ case getClassPredTys_maybe first_pred of
+ { Just (clas1,tys) -> clas == clas1 ; Nothing -> False }
+ )
+ if isSingleton preds then
+ -- If it's the only one, make a 'method'
+ getInstLoc origin `thenM` \ inst_loc ->
+ newMethod inst_loc sel_id inst_tys preds tau `thenM` \ meth_inst ->
+ returnM (Just meth_inst, instToId meth_inst)
+ else
+ -- If it's not the only one we need to be careful
+ -- For example, given 'op' defined thus:
+ -- class Foo a where
+ -- op :: (?x :: String) => a -> a
+ -- (mkMethId op T) should return an Inst with type
+ -- (?x :: String) => T -> T
+ -- That is, the class-op's context is still there.
+ -- BUT: it can't be a Method any more, because it breaks
+ -- INVARIANT 2 of methods. (See the data decl for Inst.)
+ newUnique `thenM` \ uniq ->
+ getSrcLocM `thenM` \ loc ->
+ let
+ real_tau = mkPhiTy (tail preds) tau
+ meth_id = mkUserLocal (getOccName sel_id) uniq real_tau loc
+ in
+ returnM (Nothing, meth_id)
+
+ -- 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 origin clas inst_tys sel_id loc (DefMeth dm_name)
+ = -- An polymorphic default method
+ traceRn (text "mkDefMeth" <+> ppr dm_name) `thenM_`
+ returnM (HsVar dm_name)
+
+mkDefMethRhs origin clas inst_tys sel_id loc NoDefMeth
+ = -- No default method
+ -- Warn only if -fwarn-missing-methods
+ doptM Opt_WarnMissingMethods `thenM` \ warn ->
+ warnTc (isInstDecl origin
+ && warn
+ && reportIfUnused (getOccName sel_id))
+ (omittedMethodWarn sel_id) `thenM_`
+ returnM error_rhs
+ where
+ error_rhs = HsLam (mkSimpleMatch wild_pats simple_rhs placeHolderType loc)
+ simple_rhs = HsApp (HsVar (getName nO_METHOD_BINDING_ERROR_ID))
+ (HsLit (HsStringPrim (mkFastString (stringToUtf8 error_msg))))
+ error_msg = showSDoc (hcat [ppr loc, text "|", ppr sel_id ])
+
+ -- When the type is of form t1 -> t2 -> t3
+ -- make a default method like (\ _ _ -> noMethBind "blah")
+ -- rather than simply (noMethBind "blah")
+ -- Reason: if t1 or t2 are higher-ranked types we get n
+ -- silly ambiguity messages.
+ -- Example: f :: (forall a. Eq a => a -> a) -> Int
+ -- f = error "urk"
+ -- Here, tcSub tries to force (error "urk") to have the right type,
+ -- thus: f = \(x::forall a. Eq a => a->a) -> error "urk" (x t)
+ -- where 't' is fresh ty var. This leads directly to "ambiguous t".
+ --
+ -- NB: technically this changes the meaning of the default-default
+ -- method slightly, because `seq` can see the lambdas. Oh well.
+ (_,_,tau1) = tcSplitSigmaTy (idType sel_id)
+ (_,_,tau2) = tcSplitSigmaTy tau1
+ -- Need two splits because the selector can have a type like
+ -- forall a. Foo a => forall b. Eq b => ...
+ (arg_tys, _) = tcSplitFunTys tau2
+ wild_pats = [WildPat placeHolderType | ty <- arg_tys]
+
+mkDefMethRhs origin 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)
+ ASSERT( isInstDecl origin ) -- We never get here from a class decl
+
+ checkTc (isJust maybe_tycon)
+ (badGenericInstance sel_id (notSimple inst_tys)) `thenM_`
+ checkTc (isJust (tyConGenInfo tycon))
+ (badGenericInstance sel_id (notGeneric tycon)) `thenM_`
+
+ ioToTcRn (dumpIfSet opt_PprStyle_Debug "Generic RHS" stuff) `thenM_`
+ returnM 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)
+ 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
+
+isInstDecl InstanceDeclOrigin = True
+isInstDecl ClassDeclOrigin = False
+\end{code}
- -- 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
- 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 ])
+\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)
-
-superClassErr class_name sc
- = ptext SLIT("Illegal superclass constraint") <+> quotes (ppr sc)
- <+> ptext SLIT("in declaration for class") <+> quotes (ppr class_name)
-
-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)
+
+badGenericInstance sel_id because
+ = sep [ptext SLIT("Can't derive generic code for") <+> quotes (ppr sel_id),
+ because]
+
+notSimple inst_tys
+ = vcat [ptext SLIT("because the instance type(s)"),
+ nest 2 (ppr inst_tys),
+ ptext SLIT("is not a simple type of form (T a b c)")]
+
+notGeneric tycon
+ = vcat [ptext SLIT("because the instance type constructor") <+> quotes (ppr tycon) <+>
+ ptext SLIT("was not compiled with -fgenerics")]
-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)]
+mixedGenericErr op
+ = ptext SLIT("Can't mix generic and non-generic equations for class method") <+> quotes (ppr op)
\end{code}
projects / ghc-hetmet.git / blobdiff