X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcClassDcl.lhs;h=d7da12c6223242ef99be8b5d5ced166ad3588262;hb=7c068acee32d0d6e346fb71c4efaeacbf756c496;hp=ea8e4773c2023f842c346a637197cc315ad1eeb1;hpb=f9120c200bcf613b58d742802172fb4c08171f0d;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcClassDcl.lhs b/ghc/compiler/typecheck/TcClassDcl.lhs index ea8e477..d7da12c 100644 --- a/ghc/compiler/typecheck/TcClassDcl.lhs +++ b/ghc/compiler/typecheck/TcClassDcl.lhs @@ -1,404 +1,320 @@ % -% (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, mkImplicitClassBinds, + tcMethodBind, badMethodErr + ) where + #include "HsVersions.h" -module TcClassDcl ( - tcClassDecl1, tcClassDecls2 - ) where - -import Ubiq - -import HsSyn ( ClassDecl(..), HsBinds(..), Bind(..), MonoBinds(..), - Match(..), GRHSsAndBinds(..), GRHS(..), HsExpr(..), - HsLit(..), OutPat(..), Sig(..), PolyType(..), MonoType, - Stmt, Qual, ArithSeqInfo, InPat, Fake ) -import HsPragmas ( ClassPragmas(..) ) -import RnHsSyn ( RenamedClassDecl(..), RenamedClassPragmas(..), - RenamedClassOpSig(..), RenamedMonoBinds(..), - RenamedGenPragmas(..), RenamedContext(..), - RnName{-instance Uniquable-} +import HsSyn ( HsDecl(..), TyClDecl(..), Sig(..), MonoBinds(..), + HsExpr(..), HsLit(..), HsType(..), HsPred(..), + mkSimpleMatch, andMonoBinds, andMonoBindList, + isClassDecl, isClassOpSig, isPragSig, + getClassDeclSysNames, tyClDeclName + ) +import BasicTypes ( TopLevelFlag(..), RecFlag(..) ) +import RnHsSyn ( RenamedTyClDecl, + RenamedClassOpSig, RenamedMonoBinds, + RenamedContext, RenamedHsDecl, RenamedSig, + maybeGenericMatch ) -import TcHsSyn ( TcIdOcc(..), TcHsBinds(..), TcMonoBinds(..), TcExpr(..), - mkHsTyApp, mkHsTyLam, mkHsDictApp, mkHsDictLam, unZonkId ) +import TcHsSyn ( TcMonoBinds, idsToMonoBinds ) +import Inst ( InstOrigin(..), LIE, emptyLIE, plusLIE, plusLIEs, + newDicts, newMethod ) +import TcEnv ( TcId, TcEnv, RecTcEnv, TyThingDetails(..), tcAddImportedIdInfo, + tcLookupClass, tcExtendTyVarEnvForMeths, tcExtendGlobalTyVars, + tcExtendLocalValEnv, tcExtendTyVarEnv, newDefaultMethodName + ) +import TcBinds ( tcBindWithSigs, tcSpecSigs ) +import TcMonoType ( tcHsSigType, tcClassContext, checkSigTyVars, checkAmbiguity, sigCtxt, mkTcSig ) +import TcSimplify ( tcSimplifyAndCheck, bindInstsOfLocalFuns ) +import TcType ( TcType, TcTyVar, tcInstTyVars, zonkTcSigTyVars ) import TcMonad -import Inst ( Inst, InstOrigin(..), LIE(..), emptyLIE, plusLIE, newDicts ) -import TcEnv ( tcLookupClass, tcLookupTyVar, tcLookupTyCon, newLocalIds) -import TcInstDcls ( processInstBinds ) -import TcKind ( unifyKind ) -import TcMonoType ( tcMonoType, tcContext ) -import TcType ( TcType(..), TcTyVar(..), tcInstType, tcInstSigTyVars ) -import TcKind ( TcKind ) - -import Bag ( foldBag ) -import Class ( GenClass, mkClass, mkClassOp, getClassBigSig, - getClassOps, getClassOpString, getClassOpLocalType ) -import CoreUtils ( escErrorMsg ) -import Id ( mkSuperDictSelId, mkMethodSelId, mkDefaultMethodId, - idType ) -import IdInfo ( noIdInfo ) -import Outputable ( isLocallyDefined, getOrigName, getLocalName ) -import PrelVals ( pAT_ERROR_ID ) -import PprStyle -import Pretty -import PprType ( GenType, GenTyVar, GenClassOp ) -import SpecEnv ( SpecEnv(..) ) -import SrcLoc ( mkGeneratedSrcLoc ) -import Type ( mkFunTy, mkTyVarTy, mkTyVarTys, mkDictTy, - mkForAllTy, mkSigmaTy, splitSigmaTy) -import TysWiredIn ( stringTy ) -import TyVar ( GenTyVar ) -import Unique ( Unique ) -import Util - --- import TcPragmas ( tcGenPragmas, tcClassOpPragmas ) -tcGenPragmas ty id ps = returnNF_Tc noIdInfo -tcClassOpPragmas ty sel def spec ps = returnNF_Tc (noIdInfo, noIdInfo) - +import Generics ( mkGenericRhs, validGenericMethodType ) +import PrelInfo ( nO_METHOD_BINDING_ERROR_ID ) +import Class ( classTyVars, classBigSig, classSelIds, classTyCon, classTvsFds, + Class, ClassOpItem, DefMeth (..), FunDep ) +import MkId ( mkDictSelId, mkDataConId, mkDataConWrapId, mkDefaultMethodId ) +import DataCon ( mkDataCon, notMarkedStrict ) +import Id ( Id, idType, idName ) +import Module ( Module ) +import Name ( Name, NamedThing(..), isFrom, + NameEnv, lookupNameEnv, emptyNameEnv, unitNameEnv, + plusNameEnv, nameEnvElts ) +import NameSet ( emptyNameSet ) +import Outputable +import Type ( Type, ClassContext, mkTyVarTys, mkDictTys, mkClassPred, + splitTyConApp_maybe, isTyVarTy + ) +import Var ( TyVar ) +import VarSet ( mkVarSet, emptyVarSet ) +import CmdLineOpts +import ErrUtils ( dumpIfSet ) +import Util ( count ) +import Maybes ( seqMaybe, maybeToBool, orElse ) \end{code} -\begin{code} -tcClassDecl1 rec_inst_mapper - (ClassDecl context class_name - tyvar_name class_sigs def_methods pragmas src_loc) - = tcAddSrcLoc src_loc $ - tcAddErrCtxt (classDeclCtxt class_name) $ - -- LOOK THINGS UP IN THE ENVIRONMENT - tcLookupClass class_name `thenNF_Tc` \ (class_kind, rec_class) -> - tcLookupTyVar tyvar_name `thenNF_Tc` \ (tyvar_kind, rec_tyvar) -> - let - (rec_class_inst_env, rec_class_op_inst_fn) = rec_inst_mapper rec_class - in - -- FORCE THE CLASS AND ITS TYVAR TO HAVE SAME KIND - unifyKind class_kind tyvar_kind `thenTc_` +Dictionary handling +~~~~~~~~~~~~~~~~~~~ +Every class implicitly declares a new data type, corresponding to dictionaries +of that class. So, for example: - -- CHECK THE CONTEXT - tcClassContext rec_class rec_tyvar context pragmas - `thenTc` \ (scs, sc_sel_ids) -> + class (D a) => C a where + op1 :: a -> a + op2 :: forall b. Ord b => a -> b -> b - -- CHECK THE CLASS SIGNATURES, - mapTc (tcClassSig rec_class rec_tyvar rec_class_op_inst_fn) class_sigs - `thenTc` \ sig_stuff -> +would implicitly declare - -- MAKE THE CLASS OBJECT ITSELF - tcGetUnique `thenNF_Tc` \ uniq -> - let - (ops, op_sel_ids, defm_ids) = unzip3 sig_stuff - clas = mkClass uniq (getName class_name) rec_tyvar - scs sc_sel_ids ops op_sel_ids defm_ids - rec_class_inst_env - in - returnTc clas -\end{code} + data CDict a = CDict (D a) + (a -> a) + (forall b. Ord b => a -> b -> b) +(We could use a record decl, but that means changing more of the existing apparatus. +One step at at time!) -\begin{code} -tcClassContext :: Class -> TyVar - -> RenamedContext -- class context - -> RenamedClassPragmas -- pragmas for superclasses - -> TcM s ([Class], -- the superclasses - [Id]) -- superclass selector Ids +For classes with just one superclass+method, we use a newtype decl instead: -tcClassContext rec_class rec_tyvar 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` \ theta -> - let - super_classes = [ supers | (supers, _) <- theta ] - in + class C a where + op :: forallb. a -> b -> b - -- Make super-class selector ids - mapTc (mk_super_id rec_class) - (super_classes `zip` maybe_pragmas) `thenTc` \ sc_sel_ids -> +generates - -- Done - returnTc (super_classes, sc_sel_ids) + newtype CDict a = CDict (forall b. a -> b -> b) - where - mk_super_id rec_class (super_class, maybe_pragma) - = fixTc ( \ rec_super_id -> - tcGetUnique `thenNF_Tc` \ uniq -> - - -- GET THE PRAGMA INFO FOR THE SUPERCLASS - (case maybe_pragma of - Nothing -> returnNF_Tc noIdInfo - Just prag -> tcGenPragmas Nothing{-ty unknown-} rec_super_id prag - ) `thenNF_Tc` \ id_info -> - let - ty = mkForAllTy rec_tyvar ( - mkFunTy (mkDictTy rec_class (mkTyVarTy rec_tyvar)) - (mkDictTy super_class (mkTyVarTy rec_tyvar)) - ) - in - -- BUILD THE SUPERCLASS ID - returnTc (mkSuperDictSelId uniq rec_class super_class ty id_info) - ) - - maybe_pragmas :: [Maybe RenamedGenPragmas] - maybe_pragmas = case pragmas of - NoClassPragmas -> repeat Nothing - SuperDictPragmas prags -> ASSERT(length prags == length context) - map Just prags - -- If there are any pragmas there should - -- be one for each superclass - - - -tcClassSig :: Class -- Knot tying only! - -> TyVar -- The class type variable, used for error check only - -> (ClassOp -> SpecEnv) -- Ditto; the spec info for the class ops - -> RenamedClassOpSig - -> TcM s (ClassOp, -- class op - Id, -- selector id - Id) -- default-method ids - -tcClassSig rec_clas rec_clas_tyvar rec_classop_spec_fn - (ClassOpSig op_name - (HsForAllTy tyvar_names context monotype) - pragmas src_loc) - = tcAddSrcLoc src_loc $ - fixTc ( \ ~(_, rec_sel_id, rec_defm_id) -> -- Knot for pragmas +Now DictTy in Type is just a form of type synomym: + DictTy c t = TyConTy CDict `AppTy` t - -- Check the type signature. NB that the envt *already has* - -- bindings for the type variables; see comments in TcTyAndClassDcls. - tcContext context `thenTc` \ theta -> - tcMonoType monotype `thenTc` \ tau -> - mapAndUnzipNF_Tc tcLookupTyVar tyvar_names `thenNF_Tc` \ (_,tyvars) -> +Death to "ExpandingDicts". + + +%************************************************************************ +%* * +\subsection{Type checking} +%* * +%************************************************************************ + +\begin{code} +tcClassDecl1 :: RecTcEnv -> RenamedTyClDecl -> TcM (Name, TyThingDetails) +tcClassDecl1 rec_env + (ClassDecl context class_name + tyvar_names fundeps class_sigs def_methods + sys_names src_loc) + = -- CHECK ARITY 1 FOR HASKELL 1.4 + doptsTc Opt_GlasgowExts `thenTc` \ glaExts -> + checkTc (glaExts || length tyvar_names == 1) + (classArityErr class_name) `thenTc_` + + -- LOOK THINGS UP IN THE ENVIRONMENT + tcLookupClass class_name `thenTc` \ clas -> let - full_tyvars = rec_clas_tyvar : tyvars - full_theta = (rec_clas, mkTyVarTy rec_clas_tyvar) : theta - global_ty = mkSigmaTy full_tyvars full_theta tau - local_ty = mkSigmaTy tyvars theta tau - class_op = mkClassOp (getLocalName op_name) - (panic "(getTagFromClassOpName op_name)TcClassDecl"{-(getTagFromClassOpName op_name)-}) - local_ty + (tyvars, fds) = classTvsFds 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 $ - -- Munch the pragmas - tcClassOpPragmas - global_ty - rec_sel_id rec_defm_id - (rec_classop_spec_fn class_op) - pragmas `thenNF_Tc` \ (op_info, defm_info) -> + -- CHECK THAT THE DEFAULT BINDINGS ARE LEGAL + checkDefaultBinds clas op_names def_methods `thenTc` \ dm_info -> + checkGenericClassIsUnary clas dm_info `thenTc_` + + -- CHECK THE CONTEXT + tcSuperClasses clas context sc_sel_names `thenTc` \ (sc_theta, sc_sel_ids) -> - -- Build the selector id and default method id - tcGetUnique `thenNF_Tc` \ d_uniq -> + -- CHECK THE CLASS SIGNATURES, + mapTc (tcClassSig rec_env clas tyvars fds dm_info) + op_sigs `thenTc` \ sig_stuff -> + + -- MAKE THE CLASS DETAILS let - op_uniq = uniqueOf op_name - sel_id = mkMethodSelId op_uniq rec_clas class_op global_ty op_info - defm_id = mkDefaultMethodId d_uniq rec_clas class_op False global_ty defm_info - -- ToDo: improve the "False" + (op_tys, op_items) = unzip sig_stuff + sc_tys = mkDictTys sc_theta + dict_component_tys = sc_tys ++ op_tys + + 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 + + dict_con_id = mkDataConId datacon_wkr_name dict_con + dict_wrap_id = mkDataConWrapId dict_con in - returnTc (class_op, sel_id, defm_id) - ) + returnTc (class_name, ClassDetails sc_theta sc_sel_ids op_items dict_con) \end{code} +\begin{code} +checkDefaultBinds :: Class -> [Name] -> RenamedMonoBinds -> TcM (NameEnv (DefMeth Name)) + -- 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 -%************************************************************************ -%* * -\subsection[ClassDcl-pass2]{Class decls pass 2: default methods} -%* * -%************************************************************************ +checkDefaultBinds clas ops EmptyMonoBinds = returnTc emptyNameEnv -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} +checkDefaultBinds clas ops (AndMonoBinds b1 b2) + = checkDefaultBinds clas ops b1 `thenTc` \ dm_info1 -> + checkDefaultBinds clas ops b2 `thenTc` \ dm_info2 -> + returnTc (dm_info1 `plusNameEnv` dm_info2) -Pass~2 only applies to locally-defined class declarations. +checkDefaultBinds clas ops (FunMonoBind op _ matches loc) + = tcAddSrcLoc loc $ -The function @tcClassDecls2@ just arranges to apply @tcClassDecl2@ to -each local class decl. + -- Check that the op is from this class + checkTc (op `elem` ops) (badMethodErr clas op) `thenTc_` + + -- Check that all the defns ar generic, or none are + checkTc (all_generic || none_generic) (mixedGenericErr op) `thenTc_` + + -- Make up the right dm_info + if all_generic then + returnTc (unitNameEnv op GenDefMeth) + else + -- An explicit non-generic default method + newDefaultMethodName op loc `thenNF_Tc` \ dm_name -> + returnTc (unitNameEnv op (DefMeth dm_name)) -\begin{code} -tcClassDecls2 :: Bag RenamedClassDecl - -> NF_TcM s (LIE s, TcHsBinds s) - -tcClassDecls2 decls - = foldBag combine - tcClassDecl2 - (returnNF_Tc (emptyLIE, EmptyBinds)) - decls where - combine tc1 tc2 = tc1 `thenNF_Tc` \ (lie1, binds1) -> - tc2 `thenNF_Tc` \ (lie2, binds2) -> - returnNF_Tc (lie1 `plusLIE` lie2, - binds1 `ThenBinds` binds2) + n_generic = count (maybeToBool . maybeGenericMatch) matches + none_generic = n_generic == 0 + all_generic = n_generic == length matches + +checkGenericClassIsUnary clas dm_info + = -- 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 clas) + where + unary = length (classTyVars clas) == 1 + no_generics = null [() | GenDefMeth <- nameEnvElts dm_info] \end{code} -@tcClassDecl2@ is the business end of things. \begin{code} -tcClassDecl2 :: RenamedClassDecl -- The class declaration - -> NF_TcM s (LIE s, TcHsBinds s) - -tcClassDecl2 (ClassDecl context class_name - tyvar_name class_sigs default_binds pragmas src_loc) +tcSuperClasses :: Class + -> RenamedContext -- class context + -> [Name] -- Names for superclass selectors + -> TcM (ClassContext, -- the superclass context + [Id]) -- superclass selector Ids - | not (isLocallyDefined class_name) - = returnNF_Tc (emptyLIE, EmptyBinds) +tcSuperClasses 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. - | otherwise -- It is locally defined - = recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyBinds)) $ - tcAddSrcLoc src_loc $ + -- For std Haskell check that the context constrains only tyvars + doptsTc Opt_GlasgowExts `thenTc` \ glaExts -> + (if glaExts then + returnTc () + else + mapTc_ check_constraint context + ) `thenTc_` - -- Get the relevant class - tcLookupClass class_name `thenNF_Tc` \ (_, clas) -> + -- Context is already kind-checked + tcClassContext context `thenTc` \ sc_theta -> let - (tyvar, scs, sc_sel_ids, ops, op_sel_ids, defm_ids) - = getClassBigSig clas + sc_sel_ids = [mkDictSelId sc_name clas | sc_name <- sc_sel_names] in - tcInstSigTyVars [tyvar] `thenNF_Tc` \ ([clas_tyvar], _, _) -> + -- Done + returnTc (sc_theta, sc_sel_ids) - -- Generate bindings for the selector functions - buildSelectors clas tyvar clas_tyvar scs sc_sel_ids ops op_sel_ids - `thenNF_Tc` \ sel_binds -> - -- Ditto for the methods - buildDefaultMethodBinds clas clas_tyvar defm_ids default_binds - `thenTc` \ (const_insts, meth_binds) -> + where + check_constraint sc@(HsPClass c tys) + = checkTc (all is_tyvar tys) (superClassErr clas sc) - returnTc (const_insts, sel_binds `ThenBinds` meth_binds) -\end{code} + is_tyvar (HsTyVar _) = True + is_tyvar other = False -%************************************************************************ -%* * -\subsection[ClassDcl-bld-sels]{Building the selector functions for methods and superclasses} -%* * -%************************************************************************ -\begin{code} -buildSelectors :: Class -- The class object - -> TyVar -- Class type variable - -> TcTyVar s -- Instantiated class type variable (TyVarTy) - -> [Class] -> [Id] -- Superclasses and selectors - -> [ClassOp] -> [Id] -- Class ops and selectors - -> NF_TcM s (TcHsBinds s) - -buildSelectors clas clas_tyvar clas_tc_tyvar scs sc_sel_ids ops op_sel_ids - = - -- Make new Ids for the components of the dictionary +tcClassSig :: RecTcEnv + -> Class -- ...ditto... + -> [TyVar] -- The class type variable, used for error check only + -> [FunDep TyVar] + -> NameEnv (DefMeth Name) -- Info about default methods + -> RenamedClassOpSig + -> 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 unf_env clas clas_tyvars fds dm_info + (ClassOpSig op_name maybe_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. + + tcHsSigType op_ty `thenTc` \ local_ty -> let - clas_tyvar_ty = mkTyVarTy clas_tc_tyvar - mk_op_ty = tcInstType [(clas_tyvar, clas_tyvar_ty)] . getClassOpLocalType + theta = [mkClassPred clas (mkTyVarTys clas_tyvars)] in - mapNF_Tc mk_op_ty ops `thenNF_Tc` \ op_tys -> - newLocalIds (map getClassOpString ops) op_tys `thenNF_Tc` \ method_ids -> + -- Check for ambiguous class op types + checkAmbiguity True clas_tyvars theta local_ty `thenTc` \ global_ty -> - newDicts ClassDeclOrigin - [ (super_clas, clas_tyvar_ty) - | super_clas <- scs ] `thenNF_Tc` \ (_,dict_ids) -> + let + -- Build the selector id and default method id + sel_id = mkDictSelId op_name clas - newDicts ClassDeclOrigin - [ (clas, clas_tyvar_ty) ] `thenNF_Tc` \ (_,[clas_dict]) -> + dm_info_name = maybe_dm `orElse` lookupNameEnv dm_info op_name `orElse` NoDefMeth - -- Make suitable bindings for the selectors - let - mk_sel sel_id method_or_dict - = mkSelBind sel_id clas_tc_tyvar clas_dict dict_ids method_ids method_or_dict + dm_info_id = case dm_info_name of + NoDefMeth -> NoDefMeth + GenDefMeth -> GenDefMeth + DefMeth dm_name -> DefMeth (tcAddImportedIdInfo unf_env dm_id) + where + dm_id = mkDefaultMethodId dm_name clas global_ty in - listNF_Tc (zipWithEqual mk_sel op_sel_ids method_ids) `thenNF_Tc` \ op_sel_binds -> - listNF_Tc (zipWithEqual mk_sel sc_sel_ids dict_ids) `thenNF_Tc` \ sc_sel_binds -> - - returnNF_Tc (SingleBind ( - NonRecBind ( - foldr AndMonoBinds - (foldr AndMonoBinds EmptyMonoBinds op_sel_binds) - sc_sel_binds - ))) + -- Check that for a generic method, the type of + -- the method is sufficiently simple + checkTc (dm_info_name /= GenDefMeth || validGenericMethodType local_ty) + (badGenericMethodType op_name op_ty) `thenTc_` + + returnTc (local_ty, (sel_id, dm_info_id)) \end{code} + %************************************************************************ %* * -\subsection[ClassDcl-misc]{Miscellaneous} +\subsection[ClassDcl-pass2]{Class decls pass 2: default methods} %* * %************************************************************************ -Make a selector expression for @sel_id@ from a dictionary @clas_dict@ -consisting of @dicts@ and @methods@. - -We have to do a bit of jiggery pokery to get the type variables right. -Suppose we have the class decl: -\begin{verbatim} - class Foo a where - op1 :: Ord b => a -> b -> a - op2 :: ... -\end{verbatim} -Then the method selector for \tr{op1} is like this: -\begin{verbatim} - op1_sel = /\a b -> \dFoo dOrd -> case dFoo of - (op1_method,op2_method) -> op1_method b dOrd -\end{verbatim} -Note that the type variable for \tr{b} and the (Ord b) dictionary -are lifted to the top lambda, and -\tr{op1_method} is applied to them. This is preferable to the alternative: -\begin{verbatim} - op1_sel' = /\a -> \dFoo -> case dFoo of - (op1_method,op2_method) -> op1_method -\end{verbatim} -because \tr{op1_sel'} then has the rather strange type -\begin{verbatim} - op1_sel' :: forall a. Foo a -> forall b. Ord b -> a -> b -> a -\end{verbatim} -whereas \tr{op1_sel} (the one we use) has the decent type -\begin{verbatim} - op1_sel :: forall a b. Foo a -> Ord b -> a -> b -> a -\end{verbatim} - -NOTE that we return a TcMonoBinds (which is later zonked) even though -there's no real back-substitution to do. It's just simpler this way! - -NOTE ALSO that the selector has no free type variables, so we -don't bother to instantiate the class-op's local type; instead -we just use the variables inside it. +@mkImplicitClassBinds@ produces a binding for the selector function for each method +and superclass dictionary. \begin{code} -mkSelBind :: Id -- the selector id - -> TcTyVar s -> TcIdOcc s -- class tyvar and dict - -> [TcIdOcc s] -> [TcIdOcc s] -- superclasses and methods in class dict - -> TcIdOcc s -- the superclass/method being slected - -> NF_TcM s (TcMonoBinds s) - -mkSelBind sel_id clas_tyvar clas_dict dicts methods method_or_dict@(TcId op) - = let - (op_tyvars,op_theta,op_tau) = splitSigmaTy (idType op) - op_tys = mkTyVarTys op_tyvars - in - newDicts ClassDeclOrigin op_theta `thenNF_Tc` \ (_, op_dicts) -> - - -- sel_id = /\ clas_tyvar op_tyvars -> \ clas_dict op_dicts -> - -- case clas_dict of - -- -> method_or_dict op_tyvars op_dicts - - returnNF_Tc (VarMonoBind (RealId sel_id) ( - TyLam (clas_tyvar:op_tyvars) ( - DictLam (clas_dict:op_dicts) ( - HsCase - (HsVar clas_dict) - ([PatMatch (DictPat dicts methods) ( - GRHSMatch (GRHSsAndBindsOut - [OtherwiseGRHS - (mkHsDictApp (mkHsTyApp (HsVar method_or_dict) op_tys) op_dicts) - mkGeneratedSrcLoc] - EmptyBinds - op_tau))]) - mkGeneratedSrcLoc - )))) +mkImplicitClassBinds :: Module -> [Class] -> NF_TcM ([Id], TcMonoBinds) +mkImplicitClassBinds this_mod 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 | isFrom this_mod clas = idsToMonoBinds sel_ids + | otherwise = EmptyMonoBinds \end{code} + %************************************************************************ %* * \subsection[Default methods]{Default methods} @@ -421,11 +337,10 @@ we get the default methods: defm.Foo.op1 :: forall a. Foo a => a -> Bool defm.Foo.op1 = /\a -> \dfoo -> \x -> True -defm.Foo.op2 :: forall a, b. (Foo a, Ord b) => a -> b -> b -> b -defm.Foo.op2 = /\ a b -> \ dfoo dord -> \x y z -> +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} -Notice that, like all ids, the foralls of defm.Foo.op2 are at the top. When we come across an instance decl, we may need to use the default methods: @@ -438,14 +353,15 @@ const.Foo.Int.op1 :: Int -> Bool const.Foo.Int.op1 = defm.Foo.op1 Int dfun.Foo.Int const.Foo.Int.op2 :: forall b. Ord b => Int -> b -> b -> b -const.Foo.Int.op2 = /\b -> defm.Foo.op2 Int b dfun.Foo.Int +const.Foo.Int.op2 = defm.Foo.op2 Int dfun.Foo.Int dfun.Foo.Int :: Foo Int dfun.Foo.Int = (const.Foo.Int.op1, const.Foo.Int.op2) \end{verbatim} Notice that, as with method selectors above, we assume that dictionary application is curried, so there's no need to mention the Ord dictionary -in const.Foo.Int.op2 +in const.Foo.Int.op2 (or the type variable). + \begin{verbatim} instance Foo a => Foo [a] where {} @@ -454,74 +370,304 @@ dfun.Foo.List = /\ a -> \ dfoo_a -> let rec op1 = defm.Foo.op1 [a] dfoo_list - op2 = /\b -> \dord -> defm.Foo.op2 [a] b dfoo_list dord + op2 = defm.Foo.op2 [a] dfoo_list dfoo_list = (op1, op2) in dfoo_list \end{verbatim} +The function @tcClassDecls2@ just arranges to apply @tcClassDecl2@ to +each local class decl. + \begin{code} -buildDefaultMethodBinds - :: Class - -> TcTyVar s - -> [Id] - -> RenamedMonoBinds - -> TcM s (LIE s, TcHsBinds s) - -buildDefaultMethodBinds clas clas_tyvar - default_method_ids default_binds - = -- Deal with the method declarations themselves - mapNF_Tc unZonkId default_method_ids `thenNF_Tc` \ tc_defm_ids -> - processInstBinds - (makeClassDeclDefaultMethodRhs clas default_method_ids) - [] -- No tyvars in scope for "this inst decl" - emptyLIE -- No insts available - (map TcId tc_defm_ids) - default_binds `thenTc` \ (dicts_needed, default_binds') -> - - returnTc (dicts_needed, SingleBind (NonRecBind default_binds')) +tcClassDecls2 :: Module -> [RenamedHsDecl] -> NF_TcM (LIE, TcMonoBinds) + +tcClassDecls2 this_mod decls + = foldr combine + (returnNF_Tc (emptyLIE, EmptyMonoBinds)) + [tcClassDecl2 cls_decl | TyClD cls_decl <- decls, + isClassDecl cls_decl, + isFrom this_mod (tyClDeclName 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} -@makeClassDeclDefaultMethodRhs@ builds the default method for a -class declaration when no explicit default method is given. +@tcClassDecl2@ generates bindings for polymorphic default methods +(generic default methods have by now turned into instance declarations) \begin{code} -makeClassDeclDefaultMethodRhs - :: Class - -> [Id] - -> Int - -> NF_TcM s (TcExpr s) - -makeClassDeclDefaultMethodRhs clas method_ids tag - = tcInstType [] (idType method_id) `thenNF_Tc` \ method_ty -> - let - (tyvars, theta, tau) = splitSigmaTy method_ty - in - newDicts ClassDeclOrigin theta `thenNF_Tc` \ (lie, dict_ids) -> - - returnNF_Tc (mkHsTyLam tyvars ( - mkHsDictLam dict_ids ( - HsApp (mkHsTyApp (HsVar (RealId pAT_ERROR_ID)) [tau]) - (HsLitOut (HsString (_PK_ error_msg)) stringTy)))) +tcClassDecl2 :: RenamedTyClDecl -- The class declaration + -> NF_TcM (LIE, TcMonoBinds) + +tcClassDecl2 (ClassDecl context class_name + tyvar_names _ sigs default_binds _ src_loc) + = -- A locally defined class + 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 + mapAndUnzipTc tc_dm op_items `thenTc` \ (defm_binds, const_lies) -> + + returnTc (plusLIEs const_lies, andMonoBindList defm_binds) + + +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@(_, DefMeth 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]) -> + + 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_id)) -> + + tcAddErrCtxt (defltMethCtxt clas) $ + + -- tcMethodBind has checked that the class_tyvars havn't + -- been unified with each other or another type, but we must + -- still zonk them before passing them to tcSimplifyAndCheck + zonkTcSigTyVars clas_tyvars `thenNF_Tc` \ clas_tyvars' -> + + -- Check the context + tcSimplifyAndCheck + (ptext SLIT("class") <+> ppr clas) + (mkVarSet clas_tyvars') + this_dict + insts_needed `thenTc` \ (const_lie, dict_binds) -> + + 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) where - (clas_mod, clas_name) = getOrigName clas + origin = ClassDeclOrigin +\end{code} - method_id = method_ids !! (tag-1) - class_op = (getClassOps clas) !! (tag-1) + - error_msg = "%D" -- => No default method for \" - ++ unencoded_part_of_msg +%************************************************************************ +%* * +\subsection{Typechecking a method} +%* * +%************************************************************************ - unencoded_part_of_msg = escErrorMsg ( - _UNPK_ clas_mod ++ "." ++ _UNPK_ clas_name ++ "." - ++ (ppShow 80 (ppr PprForUser class_op)) - ++ "\"" ) +@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} +tcMethodBind + :: Class + -> InstOrigin + -> [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 (TcMonoBinds, LIE, (LIE, TcId)) + +tcMethodBind clas origin inst_tyvars inst_tys inst_theta + meth_binds prags is_inst_decl (sel_id, dm_info) + = 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 + 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 + -- 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 Nothing 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_id) + = -- An polymorphic default method + returnTc (HsVar (idName dm_id)) + +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 clas) `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 clas) `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 splitTyConApp_maybe ty of + Just (tycon, arg_tys) | all isTyVarTy 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 name phase loc : prags) + | name == sel_name = InlineSig meth_name phase loc : find_prags sel_name meth_name prags +find_prags sel_name meth_name (NoInlineSig name phase loc : prags) + | name == sel_name = NoInlineSig 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 -~~~~~~~~ +Contexts and errors +~~~~~~~~~~~~~~~~~~~ \begin{code} -classDeclCtxt class_name sty - = ppCat [ppStr "In the class declaration for", ppr sty class_name] +classArityErr class_name + = ptext SLIT("Too many parameters for class") <+> quotes (ppr class_name) + +superClassErr clas sc + = ptext SLIT("Illegal superclass constraint") <+> quotes (ppr sc) + <+> ptext SLIT("in declaration for class") <+> quotes (ppr clas) + +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 clas op + = hsep [ptext SLIT("Class"), quotes (ppr clas), + ptext SLIT("does not have a 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)] + +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 clas + = 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)"), + 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) + +genericMultiParamErr clas + = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+> + ptext SLIT("cannot have generic methods") \end{code}