X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcClassDcl.lhs;h=820ed749f5a100788c6196d3a06ed98793065266;hb=1f861358a07a4bf2586964a65aebb4433f16ac70;hp=f9f28b3c0783b12e9035c1ac9af6b5e8ca3bcd61;hpb=2c8f04b5b883db74f449dfc8c224929fe28b027d;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcClassDcl.lhs b/ghc/compiler/typecheck/TcClassDcl.lhs index f9f28b3..820ed74 100644 --- a/ghc/compiler/typecheck/TcClassDcl.lhs +++ b/ghc/compiler/typecheck/TcClassDcl.lhs @@ -1,66 +1,67 @@ % -% (c) The GRASP/AQUA Project, Glasgow University, 1992-1995 +% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % \section[TcClassDcl]{Typechecking class declarations} \begin{code} -module TcClassDcl ( tcClassDecl1, tcClassDecls2, tcMethodBind, badMethodErr ) where +module TcClassDcl ( tcClassDecl1, tcClassDecls2, + MethodSpec, tcMethodBind, mkMethodBind, badMethodErr + ) where #include "HsVersions.h" -import HsSyn ( HsDecl(..), ClassDecl(..), Sig(..), MonoBinds(..), - InPat(..), andMonoBinds, getTyVarName +import HsSyn ( TyClDecl(..), Sig(..), MonoBinds(..), + HsExpr(..), HsLit(..), Pat(WildPat), + mkSimpleMatch, andMonoBinds, andMonoBindList, + isClassOpSig, isPragSig, + placeHolderType ) -import HsPragmas ( ClassPragmas(..) ) -import BasicTypes ( NewOrData(..), TopLevelFlag(..), RecFlag(..) ) -import RnHsSyn ( RenamedClassDecl(..), RenamedClassPragmas(..), - RenamedClassOpSig(..), RenamedMonoBinds, - RenamedContext(..), RenamedHsDecl +import BasicTypes ( RecFlag(..) ) +import RnHsSyn ( RenamedTyClDecl, RenamedSig, + RenamedClassOpSig, RenamedMonoBinds, + maybeGenericMatch ) +import RnEnv ( lookupSysName ) import TcHsSyn ( TcMonoBinds ) -import Inst ( Inst, InstOrigin(..), LIE, emptyLIE, plusLIE, newDicts, newMethod ) -import TcEnv ( TcIdOcc(..), tcAddImportedIdInfo, - tcLookupClass, tcLookupTyVar, - tcExtendGlobalTyVars ) -import TcBinds ( tcBindWithSigs, checkSigTyVars, sigCtxt, TcSigInfo(..) ) -import TcKind ( unifyKinds, TcKind ) -import TcMonad -import TcMonoType ( tcHsType, tcContext ) -import TcSimplify ( tcSimplifyAndCheck ) -import TcType ( TcType, TcTyVar, TcTyVarSet, tcInstSigTyVars, - zonkSigTyVar, tcInstSigTcType +import Inst ( Inst, InstOrigin(..), instToId, newDicts, newMethod ) +import TcEnv ( TyThingDetails(..), + tcLookupClass, tcExtendLocalValEnv2, + tcExtendTyVarEnv2, tcExtendTyVarEnv ) -import FieldLabel ( firstFieldLabelTag ) -import Bag ( unionManyBags ) -import Class ( mkClass, classBigSig, Class ) -import CmdLineOpts ( opt_GlasgowExts ) -import MkId ( mkDataCon, mkSuperDictSelId, - mkMethodSelId, mkDefaultMethodId +import TcTyDecls ( tcMkDataCon ) +import TcBinds ( tcMonoBinds, tcSpecSigs ) +import TcMonoType ( TcSigInfo(..), tcHsType, tcHsTheta, mkTcSig ) +import TcSimplify ( tcSimplifyCheck, bindInstsOfLocalFuns ) +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 Id ( Id, StrictnessMark(..), - getIdUnfolding, idType - ) -import CoreUnfold ( getUnfoldingTemplate ) -import IdInfo -import Name ( Name, isLocallyDefined, OccName, nameOccName, - NamedThing(..) ) +import TcRnMonad +import Generics ( mkGenericRhs ) +import PrelInfo ( nO_METHOD_BINDING_ERROR_ID ) +import Class ( classTyVars, classBigSig, classTyCon, + Class, ClassOpItem, DefMeth (..) ) +import TyCon ( tyConGenInfo ) +import Subst ( substTyWith ) +import MkId ( mkDictSelId, mkDefaultMethodId ) +import Id ( Id, idType, idName, mkUserLocal, setInlinePragma ) +import Name ( Name, NamedThing(..) ) +import NameEnv ( NameEnv, lookupNameEnv, emptyNameEnv, unitNameEnv, plusNameEnv ) +import NameSet ( emptyNameSet, unitNameSet ) +import OccName ( mkClassTyConOcc, mkClassDataConOcc, mkSuperDictSelOcc, reportIfUnused ) import Outputable -import Type ( mkFunTy, mkTyVarTy, mkTyVarTys, mkDictTy, splitRhoTy, - mkSigmaTy, mkForAllTys, Type, ThetaType - ) -import TyVar ( mkTyVarSet, tyVarKind, TyVar ) -import TyCon ( mkDataTyCon ) -import Kind ( mkBoxedTypeKind, mkArrowKind ) -import Unique ( Unique, Uniquable(..) ) -import Util -import Maybes ( assocMaybe, maybeToBool ) - - --- import TcPragmas ( tcGenPragmas, tcClassOpPragmas ) -tcGenPragmas ty id ps = returnNF_Tc noIdInfo -tcClassOpPragmas ty sel def spec ps = returnNF_Tc (spec `setSpecInfo` noIdInfo, - noIdInfo) +import Var ( TyVar ) +import CmdLineOpts +import UnicodeUtil ( stringToUtf8 ) +import ErrUtils ( dumpIfSet ) +import Util ( count, lengthIs, isSingleton ) +import Maybes ( seqMaybe ) +import Maybe ( isJust ) +import FastString \end{code} @@ -98,226 +99,156 @@ Now DictTy in Type is just a form of type synomym: Death to "ExpandingDicts". -\begin{code} -tcClassDecl1 rec_env rec_inst_mapper - (ClassDecl context class_name - tyvar_names class_sigs def_methods pragmas - tycon_name datacon_name src_loc) - = tcAddSrcLoc src_loc $ - tcAddErrCtxt (classDeclCtxt class_name) $ - - -- CHECK ARITY 1 FOR HASKELL 1.4 - checkTc (opt_GlasgowExts || length tyvar_names == 1) - (classArityErr class_name) `thenTc_` +%************************************************************************ +%* * +\subsection{Type checking} +%* * +%************************************************************************ - -- LOOK THINGS UP IN THE ENVIRONMENT - tcLookupClass class_name `thenTc` \ (class_kinds, rec_class) -> - mapAndUnzipNF_Tc (tcLookupTyVar . getTyVarName) tyvar_names - `thenNF_Tc` \ (tyvar_kinds, rec_tyvars) -> +\begin{code} - -- FORCE THE CLASS AND ITS TYVAR TO HAVE SAME KIND - unifyKinds class_kinds tyvar_kinds `thenTc_` +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 + op_sigs = filter isClassOpSig class_sigs + op_names = [n | ClassOpSig n _ _ _ <- op_sigs] + in + tcExtendTyVarEnv tyvars $ + checkDefaultBinds clas op_names def_methods `thenM` \ mb_dm_env -> + -- CHECK THE CONTEXT - tcClassContext rec_class rec_tyvars context pragmas - `thenTc` \ (sc_theta, sc_tys, 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 rec_class rec_tyvars) class_sigs - `thenTc` \ sig_stuff -> - - -- MAKE THE CLASS OBJECT ITSELF + mappM (tcClassSig clas tyvars mb_dm_env) op_sigs `thenM` \ sig_stuff -> + + -- MAKE THE CLASS DETAILS + lookupSysName class_name mkClassTyConOcc `thenM` \ tycon_name -> + lookupSysName class_name mkClassDataConOcc `thenM` \ datacon_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!) let - (op_tys, op_sel_ids, defm_ids) = unzip3 sig_stuff - rec_class_inst_env = rec_inst_mapper rec_class - clas = mkClass (getName class_name) rec_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 = mkPredTys sc_theta dict_component_tys = sc_tys ++ op_tys - new_or_data = case dict_component_tys of - [_] -> NewType - other -> DataType - - dict_con_id = mkDataCon datacon_name - [NotMarkedStrict | _ <- dict_component_tys] - [{- No labelled fields -}] - rec_tyvars - [{-No context-}] - [{-No existential tyvars-}] [{-Or context-}] - dict_component_tys - tycon - - tycon = mkDataTyCon tycon_name - (foldr (mkArrowKind . tyVarKind) mkBoxedTypeKind rec_tyvars) - rec_tyvars - [] -- No context - [dict_con_id] -- Constructors - [] -- No derivings - (Just clas) -- Yes! It's a dictionary - new_or_data - NonRecursive + sc_sel_ids = [mkDictSelId sc_name clas | sc_name <- sc_sel_names] in - returnTc clas + tcMkDataCon datacon_name + [{- No strictness -}] + [{- No labelled fields -}] + tyvars [{-No context-}] + [{-No existential tyvars-}] [{-Or context-}] + dict_component_tys + (classTyCon clas) `thenM` \ dict_con -> + + returnM (class_name, ClassDetails sc_theta sc_sel_ids op_items dict_con tycon_name) \end{code} - \begin{code} -tcClassContext :: Class -> [TyVar] - -> RenamedContext -- class context - -> RenamedClassPragmas -- pragmas for superclasses - -> TcM s (ThetaType, -- the superclass context - [Type], -- types of the superclass dictionaries - [Id]) -- superclass selector Ids - -tcClassContext rec_class rec_tyvars context pragmas - = -- Check the context. - -- The renamer has already checked that the context mentions - -- only the type variable of the class decl. - tcContext context `thenTc` \ sc_theta -> - let - sc_tys = [mkDictTy sc tys | (sc,tys) <- sc_theta] - in +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 - -- Make super-class selector ids - -- We number them off, 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!) - mapTc mk_super_id (sc_theta `zip` [firstFieldLabelTag..]) `thenTc` \ sc_sel_ids -> + go (AndMonoBinds b1 b2) + = go b1 `thenM` \ dm_info1 -> + go b2 `thenM` \ dm_info2 -> + returnM (dm_info1 `plusNameEnv` dm_info2) - -- Done - returnTc (sc_theta, sc_tys, sc_sel_ids) + go (FunMonoBind op _ matches loc) + = addSrcLoc loc $ - where - rec_tyvar_tys = mkTyVarTys rec_tyvars + -- 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_` - mk_super_id ((super_class, tys), index) - = tcGetUnique `thenNF_Tc` \ uniq -> - let - ty = mkForAllTys rec_tyvars $ - mkFunTy (mkDictTy rec_class rec_tyvar_tys) (mkDictTy super_class tys) - in - returnTc (mkSuperDictSelId uniq rec_class index ty) + 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 :: TcEnv s -- Knot tying only! - -> 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 - Id, -- selector id - Maybe Id) -- default-method ids + -> 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 maybe_dm_name - 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 - tcHsType op_ty `thenTc` \ local_ty -> let - global_ty = mkSigmaTy rec_clas_tyvars - [(rec_clas, mkTyVarTys rec_clas_tyvars)] - local_ty - in + theta = [mkClassPred clas (mkTyVarTys clas_tyvars)] -- Build the selector id and default method id - let - sel_id = mkMethodSelId 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) - in - returnTc (local_ty, sel_id, maybe_dm_id) -\end{code} - - -%************************************************************************ -%* * -\subsection[ClassDcl-pass2]{Class decls pass 2: default methods} -%* * -%************************************************************************ - -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} - -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 s, TcMonoBinds s) - -tcClassDecls2 decls - = foldr combine - (returnNF_Tc (emptyLIE, EmptyMonoBinds)) - [tcClassDecl2 cls_decl | ClD cls_decl <- decls] - 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 :: RenamedClassDecl -- The class declaration - -> NF_TcM s (LIE s, TcMonoBinds s) + sel_id = mkDictSelId op_name clas + DefMeth dm_name = sig_dm -tcClassDecl2 (ClassDecl context class_name - tyvar_names class_sigs default_binds pragmas _ _ src_loc) + dm_info = case maybe_dm_env of + Nothing -> sig_dm + Just dm_env -> mk_src_dm_info dm_env - | not (isLocallyDefined class_name) - = returnNF_Tc (emptyLIE, EmptyMonoBinds) - - | otherwise -- It is locally defined - = recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $ - tcAddSrcLoc src_loc $ - - -- Get the relevant class - tcLookupClass class_name `thenTc` \ (_, clas) -> - let - (tyvars, sc_theta, sc_sel_ids, op_sel_ids, defm_ids) = classBigSig clas - - -- The selector binds are already in the selector Id's unfoldings - sel_binds = [ CoreMonoBind (RealId sel_id) (getUnfoldingTemplate (getIdUnfolding sel_id)) - | sel_id <- sc_sel_ids ++ op_sel_ids, - isLocallyDefined sel_id - ] - - final_sel_binds = andMonoBinds sel_binds + mk_src_dm_info dm_env = case lookupNameEnv dm_env op_name of + Nothing -> NoDefMeth + Just True -> GenDefMeth + Just False -> DefMeth dm_name in - -- Generate bindings for the default methods - tcDefaultMethodBinds clas default_binds `thenTc` \ (const_insts, meth_binds) -> - - returnTc (const_insts, - final_sel_binds `AndMonoBinds` meth_binds) + returnM (local_ty, (sel_id, dm_info)) \end{code} + %************************************************************************ %* * \subsection[Default methods]{Default methods} @@ -340,23 +271,11 @@ we get the default methods: defm.Foo.op1 :: forall a. Foo a => a -> Bool defm.Foo.op1 = /\a -> \dfoo -> \x -> True -====================== OLD ================== -\begin{verbatim} -defm.Foo.op2 :: forall a, b. (Foo a, Ord b) => a -> b -> b -> b -defm.Foo.op2 = /\ a b -> \ dfoo dord -> \x y z -> - if (op1 a dfoo x) && (< b dord y z) then y else z -\end{verbatim} -Notice that, like all ids, the foralls of defm.Foo.op2 are at the top. -====================== END OF OLD =================== - -NEW: -\begin{verbatim} defm.Foo.op2 :: forall a. Foo a => forall b. Ord b => a -> b -> b -> b defm.Foo.op2 = /\ a -> \ dfoo -> /\ b -> \ dord -> \x y z -> if (op1 a dfoo x) && (< b dord y z) then y else z \end{verbatim} - When we come across an instance decl, we may need to use the default methods: \begin{verbatim} @@ -391,139 +310,409 @@ dfun.Foo.List dfoo_list \end{verbatim} +The function @tcClassDecls2@ just arranges to apply @tcClassDecl2@ to +each local class decl. + \begin{code} -tcDefaultMethodBinds - :: Class - -> RenamedMonoBinds - -> TcM s (LIE s, TcMonoBinds s) +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 + combine tc1 tc2 = tc1 `thenM` \ (binds1, ids1) -> + tc2 `thenM` \ (binds2, ids2) -> + returnM (binds1 `AndMonoBinds` binds2, + ids1 ++ ids2) +\end{code} -tcDefaultMethodBinds clas default_binds - = -- Construct suitable signatures - tcInstSigTyVars tyvars `thenNF_Tc` \ (clas_tyvars, inst_tys, inst_env) -> +@tcClassDecl2@ generates bindings for polymorphic default methods +(generic default methods have by now turned into instance declarations) - -- Typecheck the default bindings +\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 - tc_dm meth_bind - | not (maybeToBool maybe_stuff) - = -- Binding for something that isn't in the class signature - failWithTc (badMethodErr bndr_name clas) - - | otherwise - = -- Normal case - tcMethodBind clas origin inst_tys clas_tyvars sel_id meth_bind - `thenTc` \ (bind, insts, (_, local_dm_id)) -> - returnTc (bind, insts, (clas_tyvars, RealId dm_id, local_dm_id)) - where - bndr_name = case meth_bind of - FunMonoBind name _ _ _ -> name - PatMonoBind (VarPatIn name) _ _ -> name - - maybe_stuff = assocMaybe assoc_list (nameOccName bndr_name) - assoc_list = [ (getOccName sel_id, pair) - | pair@(sel_id, dm_ie) <- op_sel_ids `zip` defm_ids - ] - Just (sel_id, Just dm_id) = maybe_stuff - -- We're looking at a default-method binding, so the dm_id - -- is sure to be there! Hence the inner "Just". - in - mapAndUnzip3Tc tc_dm - (flatten default_binds []) `thenTc` \ (defm_binds, insts_needed, abs_bind_stuff) -> - - -- Check the context - newDicts origin [(clas,inst_tys)] `thenNF_Tc` \ (this_dict, [this_dict_id]) -> + (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) -> + + returnM (andMonoBindList defm_binds, concat dm_ids_s) + + +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 - avail_insts = this_dict + dm_ty = idType sel_id -- Same as dict selector! + theta = [mkClassPred clas inst_tys] + local_dm_id = mkDefaultMethodId dm_name dm_ty + xtve = tyvars `zip` clas_tyvars in - tcAddErrCtxt (classDeclCtxt clas) $ - mapNF_Tc zonkSigTyVar clas_tyvars `thenNF_Tc` \ clas_tyvars' -> - tcSimplifyAndCheck - (ptext SLIT("class") <+> ppr clas) - (mkTyVarSet clas_tyvars') - avail_insts - (unionManyBags insts_needed) `thenTc` \ (const_lie, dict_binds) -> - + 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) -> + + addErrCtxt (defltMethCtxt clas) $ + + -- 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_binds = AbsBinds - clas_tyvars' - [this_dict_id] - abs_bind_stuff - (dict_binds `AndMonoBinds` andMonoBinds defm_binds) + (_,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 - returnTc (const_lie, full_binds) - + returnM (full_bind, [local_dm_id]) where - (tyvars, sc_theta, sc_sel_ids, op_sel_ids, defm_ids) = classBigSig clas origin = ClassDeclOrigin - - flatten EmptyMonoBinds rest = rest - flatten (AndMonoBinds b1 b2) rest = flatten b1 (flatten b2 rest) - flatten a_bind rest = a_bind : rest \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 s - -> [TcType s] -- Instance types - -> [TcTyVar s] -- Free variables of those instance types - -- they'll be signature tyvars, and we - -- want to check that they don't bound - -> Id -- The method selector - -> RenamedMonoBinds -- Method binding (just one) - -> TcM s (TcMonoBinds s, LIE s, (LIE s, TcIdOcc s)) - -tcMethodBind clas origin inst_tys inst_tyvars sel_id meth_bind - = tcAddSrcLoc src_loc $ - newMethod origin (RealId sel_id) inst_tys `thenNF_Tc` \ meth@(_, TcId local_meth_id) -> - tcInstSigTcType (idType local_meth_id) `thenNF_Tc` \ (tyvars', rho_ty') -> - let - (theta', tau') = splitRhoTy rho_ty' - sig_info = TySigInfo bndr_name local_meth_id tyvars' theta' tau' src_loc - in - tcExtendGlobalTyVars inst_tyvars ( - tcAddErrCtxt (methodCtxt sel_id) $ - tcBindWithSigs NotTopLevel [bndr_name] meth_bind [sig_info] - NonRecursive (\_ -> noIdInfo) - ) `thenTc` \ (binds, insts, _) -> - - -- 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 - tcAddErrCtxt (monoCtxt sel_id) ( - tcAddErrCtxt (sigCtxt sel_id) $ - checkSigTyVars inst_tyvars (idType local_meth_id) - ) `thenTc_` - - returnTc (binds, insts, meth) - where - (bndr_name, src_loc) = case meth_bind of - FunMonoBind name _ _ loc -> (name, loc) - PatMonoBind (VarPatIn name) _ loc -> (name, loc) + :: [(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 + -- 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 + 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 + + 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 + sel_name = idName sel_id + inline_prags = [ (is_inl, phase) + | InlineSig is_inl name phase _ <- prags, + name == sel_name ] + spec_prags = [ prag + | prag@(SpecSig name _ _) <- prags, + name == sel_name] + + -- Attach inline pragmas as appropriate + (final_meth_id, inlines) + | ((is_inline, phase) : _) <- inline_prags + = (meth_id `setInlinePragma` phase, + if is_inline then unitNameSet (idName meth_id) else emptyNameSet) + | otherwise + = (meth_id, emptyNameSet) + + 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 + -- Deal with specialisation pragmas + -- The sel_name is what appears in the pragma + tcExtendLocalValEnv2 [(sel_name, final_meth_id)] ( + getLIE (tcSpecSigs spec_prags) `thenM` \ (spec_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 [final_meth_id] `thenM` \ spec_binds2 -> + returnM (spec_binds1 `andMonoBinds` spec_binds2) + ) `thenM` \ spec_binds -> + + returnM (poly_meth_bind `andMonoBinds` spec_binds) + + +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 +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} + +\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) - -classDeclCtxt class_name - = ptext SLIT("In the class declaration for") <+> 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) -monoCtxt sel_id - = sep [ptext SLIT("Probable cause: the right hand side of") <+> quotes (ppr sel_id), - nest 4 (ptext SLIT("mentions a top-level variable subject to the dreaded monomorphism restriction")) - ] - -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")] + +mixedGenericErr op + = ptext SLIT("Can't mix generic and non-generic equations for class method") <+> quotes (ppr op) \end{code}