X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcClassDcl.lhs;h=3994e93952ab2bc9a97d14967ea00554e34bdd2d;hb=df65fd0b7646ffa17ed553289a4cd0e806bef8b9;hp=a890255ed1b71dc1c4235d338837ba13ac642036;hpb=68a1f0233996ed79824d11d946e9801473f6946c;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcClassDcl.lhs b/ghc/compiler/typecheck/TcClassDcl.lhs index a890255..3994e93 100644 --- a/ghc/compiler/typecheck/TcClassDcl.lhs +++ b/ghc/compiler/typecheck/TcClassDcl.lhs @@ -1,393 +1,314 @@ % -% (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} -#include "HsVersions.h" - -module TcClassDcl ( - tcClassDecls1, tcClassDecls2, - ClassInfo -- abstract - ) where +module TcClassDcl ( tcClassDecl1, tcClassDecls2, + tcMethodBind, badMethodErr + ) where -IMPORT_Trace -- ToDo: rm (debugging) -import Pretty -- add proper one below - -import TcMonad -- typechecking monad machinery -import TcMonadFns ( newDicts, newClassOpLocals, copyTyVars ) -import AbsSyn -- the stuff being typechecked +#include "HsVersions.h" -import AbsPrel ( pAT_ERROR_ID ) -import AbsUniType ( mkClass, getClassKey, getClassBigSig, - getClassOpString, getClassOps, splitType, - mkSuperDictSelType, InstTyEnv(..), - instantiateTy, instantiateThetaTy, UniType +import HsSyn ( TyClDecl(..), Sig(..), MonoBinds(..), + HsExpr(..), HsLit(..), HsType(..), HsPred(..), + mkSimpleMatch, andMonoBinds, andMonoBindList, + isClassOpSig, isPragSig, + getClassDeclSysNames, ) -import BackSubst ( applyTcSubstToBinds ) -import CE -- ( nullCE, unitCE, plusCE, CE(..), UniqFM ) -import E ( mkE, getE_TCE, getE_CE, tvOfE, nullGVE, plusGVE, E, TCE(..), UniqFM, GVE(..) ) -import Errors ( confusedNameErr, Error(..) ) -import HsPragmas -- ****** NEED TO SEE CONSTRUCTORS ****** -import Id ( mkSuperDictSelId, mkInstId, getIdUniType, - Id, DictFun(..) +import BasicTypes ( TopLevelFlag(..), RecFlag(..) ) +import RnHsSyn ( RenamedTyClDecl, + RenamedClassOpSig, RenamedMonoBinds, + RenamedContext, RenamedSig, + maybeGenericMatch ) -import IdInfo -import Inst ( InstOrigin(..), Inst ) -import InstEnv -import LIE ( nullLIE, mkLIE, plusLIE, LIE ) -import Maybes ( Maybe(..) ) -import Name ( Name(..) ) -import PlainCore ( escErrorMsg ) -import Spec ( specTy ) -import TVE ( mkTVE, TVE(..) - IF_ATTACK_PRAGMAS(COMMA u2i) +import TcHsSyn ( TcMonoBinds ) + +import Inst ( Inst, InstOrigin(..), LIE, emptyLIE, plusLIE, plusLIEs, + instToId, newDicts, newMethod ) +import TcEnv ( RecTcEnv, TyThingDetails(..), tcAddImportedIdInfo, + tcLookupClass, tcExtendTyVarEnvForMeths, tcExtendGlobalTyVars, + tcExtendLocalValEnv, tcExtendTyVarEnv + ) +import TcBinds ( tcBindWithSigs, tcSpecSigs ) +import TcMonoType ( tcHsRecType, tcRecTheta, checkSigTyVars, checkAmbiguity, sigCtxt, mkTcSig ) +import TcSimplify ( tcSimplifyCheck, bindInstsOfLocalFuns ) +import TcType ( TcType, TcTyVar, tcInstTyVars ) +import TcMonad +import Generics ( mkGenericRhs, validGenericMethodType ) +import PrelInfo ( nO_METHOD_BINDING_ERROR_ID ) +import Class ( classTyVars, classBigSig, classTyCon, + Class, ClassOpItem, DefMeth (..) ) +import MkId ( mkDictSelId, mkDataConId, mkDataConWrapId, mkDefaultMethodId ) +import DataCon ( mkDataCon, notMarkedStrict ) +import Id ( Id, idType, idName ) +import Module ( Module ) +import Name ( Name, NamedThing(..) ) +import NameEnv ( NameEnv, lookupNameEnv, emptyNameEnv, unitNameEnv, plusNameEnv, nameEnvElts ) +import NameSet ( emptyNameSet ) +import Outputable +import Type ( Type, ThetaType, mkTyVarTys, mkPredTys, mkClassPred, + splitTyConApp_maybe, isTyVarTy ) -import TcClassSig ( tcClassSigs ) -import TcContext ( tcContext ) -import TcInstDcls ( processInstBinds ) -import TcPragmas ( tcGenPragmas ) -import Util +import Var ( TyVar ) +import VarSet ( mkVarSet, emptyVarSet ) +import CmdLineOpts +import ErrUtils ( dumpIfSet ) +import Util ( count ) +import Maybes ( seqMaybe, maybeToBool ) \end{code} -@ClassInfo@ communicates the essential information about -locally-defined classes between passes 1 and 2. -\begin{code} -data ClassInfo - = ClassInfo Class - RenamedMonoBinds -\end{code} + +Dictionary handling +~~~~~~~~~~~~~~~~~~~ +Every class implicitly declares a new data type, corresponding to dictionaries +of that class. So, for example: + + class (D a) => C a where + op1 :: a -> a + op2 :: forall b. Ord b => a -> b -> b + +would implicitly declare + + 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!) + +For classes with just one superclass+method, we use a newtype decl instead: + + class C a where + op :: forallb. a -> b -> b + +generates + + newtype CDict a = CDict (forall b. a -> b -> b) + +Now DictTy in Type is just a form of type synomym: + DictTy c t = TyConTy CDict `AppTy` t + +Death to "ExpandingDicts". %************************************************************************ %* * -\subsection[TcClassDcl]{Does the real work (apart from default methods)} +\subsection{Type checking} %* * %************************************************************************ \begin{code} -tcClassDecls1 - :: E -- Consult the CE/TCE args only to build knots - -> InstanceMapper -- Maps class name to its instances, - -- ...and its ops to their instances, - -> [RenamedClassDecl] - -> TcM ([ClassInfo], -- boiled-down info related to classes - CE, -- env so we can look up classes elsewhere - GVE) -- env so we can look up class ops elsewhere - -tcClassDecls1 e rec_inst_mapper [] - = returnTc ([], nullCE, nullGVE) - -tcClassDecls1 e rec_inst_mapper (cd:cds) - = tc_clas1 cd `thenTc` \ (cinfo1_maybe, ce1, gve1) -> - tcClassDecls1 e rec_inst_mapper cds `thenTc` \ (cinfo2, ce2, gve2) -> + +tcClassDecl1 :: RecFlag -> RecTcEnv -> RenamedTyClDecl -> TcM (Name, TyThingDetails) +tcClassDecl1 is_rec rec_env + (ClassDecl {tcdCtxt = context, tcdName = class_name, + tcdTyVars = tyvar_names, tcdFDs = fundeps, + tcdSigs = class_sigs, tcdMeths = def_methods, + tcdSysNames = sys_names, tcdLoc = src_loc}) + = -- CHECK ARITY 1 FOR HASKELL 1.4 + doptsTc Opt_GlasgowExts `thenTc` \ gla_ext_opt -> + let + gla_exts = gla_ext_opt || not (maybeToBool def_methods) + -- Accept extensions if gla_exts is on, + -- or if we're looking at an interface file decl + in -- (in which case def_methods = Nothing + + -- LOOK THINGS UP IN THE ENVIRONMENT + tcLookupClass class_name `thenTc` \ clas -> let - glued_cinfos - = case cinfo1_maybe of - Nothing -> cinfo2 - Just xx -> xx : cinfo2 + tyvars = classTyVars clas + op_sigs = filter isClassOpSig class_sigs + op_names = [n | ClassOpSig n _ _ _ <- op_sigs] + (_, datacon_name, datacon_wkr_name, sc_sel_names) = getClassDeclSysNames sys_names in - returnTc (glued_cinfos, ce1 `plusCE` ce2, gve1 `plusGVE` gve2) - where - rec_ce = getE_CE e - rec_tce = getE_TCE e - - tc_clas1 (ClassDecl context class_name - tyvar_name class_sigs def_methods pragmas src_loc) - - = addSrcLocTc src_loc ( - - -- The knot is needed so that the signatures etc can point - -- back to the class itself - fixTc (\ ~(rec_clas, _) -> - let - (rec_clas_inst_env, rec_class_op_inst_fn) = rec_inst_mapper rec_clas - in - -- Get new (template) type variables for the class - let (tve, [clas_tyvar], [alpha]) = mkTVE [tyvar_name] in - - -- Typecheck the class context; since there is only one type - -- variable in scope, we are assured that the it will be of - -- the form (C1 a, C2 a...) - babyTcMtoTcM (tcContext rec_ce rec_tce tve context) `thenTc` \ theta -> - - -- Make the superclass selector ids; the "class" pragmas - -- may have info about the superclass dict selectors; - -- so it is only tcClassPragmas that gives back the - -- final Ids. - getUniquesTc (length theta) `thenNF_Tc` \ uniqs -> - let - super_classes = [ supers | (supers, _) <- theta ] - super_tys - = [ mkSuperDictSelType rec_clas super | super <- super_classes ] - super_info = zip3 super_classes uniqs super_tys - in - (case pragmas of - NoClassPragmas -> - returnNF_Tc [ mk_super_id rec_clas info noIdInfo | info <- super_info ] - - SuperDictPragmas prags -> --- pprTrace "SuperDictPragmas:" (ppAboves (ppr PprDebug prags : map pp super_info)) ( - mapNF_Tc (mk_super_id_w_info rec_clas) (super_info `zipEqual` prags) --- ) --- where --- pp (sc, u, ty) = ppCat [ppr PprDebug sc, ppr PprDebug ty] - - ) `thenNF_Tc` \ super_class_sel_ids -> - - -- Typecheck the class signatures, checking that each mentions - -- the class type variable somewhere, and manufacturing - -- suitable Ids for selectors and default methods. - babyTcMtoTcM - (tcClassSigs e tve rec_clas rec_class_op_inst_fn - clas_tyvar defm_names class_sigs) - `thenTc` \ (ops, ops_gve, op_sel_ids, defm_ids) -> - - -- Make the class object itself, producing clas::Class - let - clas - = mkClass class_name clas_tyvar - super_classes super_class_sel_ids - ops op_sel_ids defm_ids - rec_clas_inst_env - in - returnTc (clas, ops_gve) - ) `thenTc` \ (clas, ops_gve) -> - - -- Return the class decl for further work if it is - -- local, otherwise just return the CE - returnTc (if (isLocallyDefined class_name) then - Just (ClassInfo clas def_methods) - else - Nothing, - unitCE (getClassKey clas) clas, - ops_gve - )) - where - defm_names = collectMonoBinders def_methods - - ----------- - mk_super_id clas (super_clas, uniq, ty) id_info - = mkSuperDictSelId uniq clas super_clas ty id_info - - ----------- - mk_super_id_w_info clas ((super_clas, uniq, ty), gen_prags) - = fixNF_Tc ( \ rec_super_id -> - babyTcMtoNF_TcM - (tcGenPragmas e{-fake_E-} Nothing{-ty unknown-} rec_super_id gen_prags) - `thenNF_Tc` \ id_info -> - - returnNF_Tc(mkSuperDictSelId uniq clas super_clas ty id_info) - ) - -{- SOMETHING LIKE THIS NEEDED? ToDo [WDP] - tc_clas1 (ClassDecl _ bad_name _ _ _ _ src_loc) - = failTc (confusedNameErr - "Bad name for a class (a type constructor, or Prelude name?)" - bad_name src_loc) --} -\end{code} + tcExtendTyVarEnv tyvars $ + -- SOURCE-CODE CONSISTENCY CHECKS + (case def_methods of + Nothing -> -- Not source + returnTc Nothing -%************************************************************************ -%* * -\subsection[ClassDcl-pass2]{Class decls pass 2: default methods} -%* * -%************************************************************************ + Just dms -> -- Source so do error checks + checkTc (gla_exts || length tyvar_names == 1) + (classArityErr class_name) `thenTc_` -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 -\end{enumerate} + checkDefaultBinds clas op_names dms `thenTc` \ dm_env -> + checkGenericClassIsUnary clas dm_env `thenTc_` + returnTc (Just dm_env) + ) `thenTc` \ mb_dm_env -> + + -- CHECK THE CONTEXT + tcSuperClasses is_rec gla_exts clas context sc_sel_names `thenTc` \ (sc_theta, sc_sel_ids) -> -Pass~2 only applies to locally-defined class declarations. + -- CHECK THE CLASS SIGNATURES, + mapTc (tcClassSig is_rec rec_env clas tyvars mb_dm_env) op_sigs `thenTc` \ sig_stuff -> -The function @tcClassDecls2@ just arranges to apply -@tcClassDecls2_help@ to each local class decl. + -- MAKE THE CLASS DETAILS + let + (op_tys, op_items) = unzip sig_stuff + sc_tys = mkPredTys 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_name, ClassDetails sc_theta sc_sel_ids op_items dict_con) +\end{code} \begin{code} -tcClassDecls2 e class_info - = let - -- Get type variables free in environment. Sadly, there may be - -- some, because of the dreaded monomorphism restriction - free_tyvars = tvOfE e - in - tcClassDecls2_help e free_tyvars class_info +checkDefaultBinds :: Class -> [Name] -> RenamedMonoBinds + -> TcM (NameEnv Bool) + -- The returned environment says + -- x not in env => no default method + -- x -> True => generic default method + -- x -> False => polymorphic default method -tcClassDecls2_help - :: E - -> [TyVar] - -> [ClassInfo] - -> NF_TcM (LIE, TypecheckedBinds) + -- 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 -tcClassDecls2_help e free_tyvars [] = returnNF_Tc (nullLIE, EmptyBinds) + -- But do all this only for source binds -tcClassDecls2_help e free_tyvars ((ClassInfo clas default_binds) : rest) - = tcClassDecl2 e free_tyvars clas default_binds `thenNF_Tc` \ (lie1, binds1) -> - tcClassDecls2_help e free_tyvars rest `thenNF_Tc` \ (lie2, binds2) -> - returnNF_Tc (lie1 `plusLIE` lie2, binds1 `ThenBinds` binds2) -\end{code} +checkDefaultBinds clas ops EmptyMonoBinds = returnTc emptyNameEnv -@tcClassDecl2@ is the business end of things. +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) -\begin{code} -tcClassDecl2 :: E - -> [TyVar] -- Free in the envt - -> Class - -> RenamedMonoBinds -- The default decls - -> NF_TcM (LIE, TypecheckedBinds) - -tcClassDecl2 e free_tyvars clas default_binds - = let - src_loc = getSrcLoc clas - origin = ClassDeclOrigin src_loc - (clas_tyvar_tmpl, scs, sc_sel_ids, ops, op_sel_ids, defm_ids) - = getClassBigSig clas - in - -- Prune the substitution when we are finished, and arrange error recovery - recoverTc (nullLIE, EmptyBinds) ( - addSrcLocTc src_loc ( - pruneSubstTc free_tyvars ( - - -- Generate bindings for the selector functions - buildSelectors origin clas clas_tyvar_tmpl scs sc_sel_ids ops op_sel_ids - `thenNF_Tc` \ sel_binds -> - -- Ditto for the methods - buildDefaultMethodBinds e free_tyvars origin clas clas_tyvar_tmpl - defm_ids default_binds `thenTc` \ (const_insts, meth_binds) -> - - -- Back-substitute through the definitions - applyTcSubstToInsts const_insts `thenNF_Tc` \ final_const_insts -> - applyTcSubstToBinds (sel_binds `ThenBinds` meth_binds) `thenNF_Tc` \ final_binds -> - returnTc (mkLIE final_const_insts, final_binds) - ))) +checkDefaultBinds clas ops (FunMonoBind op _ matches loc) + = tcAddSrcLoc loc $ + + -- 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_` + + returnTc (unitNameEnv op all_generic) + where + n_generic = count (maybeToBool . maybeGenericMatch) matches + none_generic = n_generic == 0 + all_generic = n_generic == length matches + +checkGenericClassIsUnary clas dm_env + = -- 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 = not (or (nameEnvElts dm_env)) \end{code} -%************************************************************************ -%* * -\subsection[ClassDcl-bld-sels]{Building the selector functions for methods and superclasses} -%* * -%************************************************************************ \begin{code} -buildSelectors :: InstOrigin - -> Class -- The class object - -> TyVarTemplate -- Class type variable - -> [Class] -> [Id] -- Superclasses and selectors - -> [ClassOp] -> [Id] -- Class ops and selectors - -> NF_TcM TypecheckedBinds - -buildSelectors origin clas clas_tyvar_tmpl - scs sc_sel_ids - ops op_sel_ids - = - -- Instantiate the class variable - copyTyVars [clas_tyvar_tmpl] `thenNF_Tc` \ (inst_env, [clas_tyvar], [clas_tyvar_ty]) -> - -- Make an Inst for each class op, and - -- dicts for the superclasses. These are used to - -- construct the selector functions - newClassOpLocals inst_env ops `thenNF_Tc` \ method_ids -> - newDicts origin [ (super_clas, clas_tyvar_ty) - | super_clas <- scs - ] `thenNF_Tc` \ dicts -> - let dict_ids = map mkInstId dicts in - - -- Make suitable bindings for the selectors - let mk_op_sel op sel_id method_id - = mkSelExpr origin clas_tyvar dict_ids method_ids method_id `thenNF_Tc` \ rhs -> - returnNF_Tc (VarMonoBind sel_id rhs) - mk_sc_sel sc sel_id dict_id - = mkSelExpr origin clas_tyvar dict_ids method_ids dict_id `thenNF_Tc` \ rhs -> - returnNF_Tc (VarMonoBind sel_id rhs) +tcSuperClasses :: RecFlag -> Bool -> Class + -> RenamedContext -- class context + -> [Name] -- Names for superclass selectors + -> TcM (ThetaType, -- the superclass context + [Id]) -- superclass selector Ids + +tcSuperClasses is_rec gla_exts clas context sc_sel_names + = ASSERT( length context == length sc_sel_names ) + -- Check the context. + -- The renamer has already checked that the context mentions + -- only the type variable of the class decl. + + -- For std Haskell check that the context constrains only tyvars + mapTc_ check_constraint context `thenTc_` + + -- Context is already kind-checked + tcRecTheta is_rec context `thenTc` \ sc_theta -> + let + sc_sel_ids = [mkDictSelId sc_name clas | sc_name <- sc_sel_names] in - listNF_Tc (zipWith3 mk_op_sel ops op_sel_ids method_ids) `thenNF_Tc` \ op_sel_binds -> - listNF_Tc (zipWith3 mk_sc_sel scs sc_sel_ids dict_ids) `thenNF_Tc` \ sc_sel_binds -> + -- Done + returnTc (sc_theta, sc_sel_ids) - returnNF_Tc (SingleBind ( - NonRecBind ( - foldr AndMonoBinds EmptyMonoBinds ( - op_sel_binds ++ sc_sel_binds)))) -\end{code} + where + check_constraint sc = checkTc (ok sc) (superClassErr clas sc) + ok (HsClassP c tys) | gla_exts = True + | otherwise = all is_tyvar tys + ok (HsIParam _ _) = False -- Never legal -%************************************************************************ -%* * -\subsection[ClassDcl-misc]{Miscellaneous} -%* * -%************************************************************************ + is_tyvar (HsTyVar _) = True + is_tyvar other = False -Make a selector expression for @local@ from a dictionary consisting of -@dicts@ and @op_locals@. -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 = /\ab -> \dFoo -> case dFoo of - (op1_method,op2_method) -> op1_method b -\end{verbatim} -Note that the type variable for \tr{b} is lifted to the top big lambda, and -\tr{op1_method} is applied to it. 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} +tcClassSig :: RecFlag -> RecTcEnv -- Knot tying only! + -> Class -- ...ditto... + -> [TyVar] -- The class type variable, used for error check only + -> Maybe (NameEnv Bool) -- Info about default methods + -> RenamedClassOpSig + -> TcM (Type, -- Type of the method + ClassOpItem) -- Selector Id, default-method Id, True if explicit default binding -{\em NOTE:} -We could do the same thing for the dictionaries, giving -\begin{verbatim} - op1_sel = /\ab -> \dFoo -> \dOrd -> case dFoo of - (m1,m2) -> m1 b dOrd -\end{verbatim} -but WE ASSUME THAT DICTIONARY APPLICATION IS CURRIED, so the two are -precisely equivalent, and have the same type, namely -\begin{verbatim} - op1_sel :: forall a b. Foo a -> Ord b -> a -> b -> a -\end{verbatim} +-- 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. -WDP 95/03: Quite false (``DICTIONARY APPLICATION IS CURRIED''). -Specialisation now wants to see all type- and dictionary-applications -absolutely explicitly. +tcClassSig is_rec unf_env clas clas_tyvars maybe_dm_env + (ClassOpSig op_name sig_dm op_ty src_loc) + = tcAddSrcLoc src_loc $ -\begin{code} -mkSelExpr :: InstOrigin -> TyVar -> [Id] -> [Id] -> Id -> NF_TcM TypecheckedExpr + -- Check the type signature. NB that the envt *already has* + -- bindings for the type variables; see comments in TcTyAndClassDcls. -mkSelExpr origin clas_tyvar dicts op_locals local - = let - (op_tyvar_tmpls,local_theta,_) = splitType (getIdUniType local) - in - copyTyVars op_tyvar_tmpls `thenNF_Tc` \ (inst_env, op_tyvars, tys) -> + tcHsRecType is_rec op_ty `thenTc` \ local_ty -> + + -- Check for ambiguous class op types let - inst_theta = instantiateThetaTy inst_env local_theta + theta = [mkClassPred clas (mkTyVarTys clas_tyvars)] in - newDicts origin inst_theta `thenNF_Tc` \ local_dict_insts -> + checkAmbiguity is_rec True clas_tyvars theta local_ty `thenTc` \ global_ty -> + -- 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. + let - local_dicts = map mkInstId local_dict_insts + -- Build the selector id and default method id + sel_id = mkDictSelId op_name clas + dm_id = mkDefaultMethodId dm_name global_ty + DefMeth dm_name = sig_dm + + dm_info = case maybe_dm_env of + Nothing -> iface_dm_info + Just dm_env -> mk_src_dm_info dm_env + + iface_dm_info = case sig_dm of + NoDefMeth -> NoDefMeth + GenDefMeth -> GenDefMeth + DefMeth dm_name -> DefMeth (tcAddImportedIdInfo unf_env dm_id) + + mk_src_dm_info dm_env = case lookupNameEnv dm_env op_name of + Nothing -> NoDefMeth + Just True -> GenDefMeth + Just False -> DefMeth dm_id in - returnNF_Tc (TyLam (clas_tyvar:op_tyvars) - (ClassDictLam - dicts - op_locals - (mkDictLam local_dicts - (mkDictApp (mkTyApp (Var local) tys) local_dicts)))) + -- Check that for a generic method, the type of + -- the method is sufficiently simple + checkTc (dm_info /= GenDefMeth || validGenericMethodType local_ty) + (badGenericMethodType op_name op_ty) `thenTc_` + + returnTc (local_ty, (sel_id, dm_info)) \end{code} @@ -413,11 +334,10 @@ 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: @@ -430,14 +350,15 @@ 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 {} @@ -446,66 +367,303 @@ dfun.Foo.List = /\ a -> \ dfoo_a -> let rec op1 = defm.Foo.op1 [a] dfoo_list - op2 = /\b -> defm.Foo.op2 [a] b dfoo_list + 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 - :: E - -> [TyVar] - -> InstOrigin - -> Class - -> TyVarTemplate - -> [Id] - -> RenamedMonoBinds - -> TcM ([Inst], TypecheckedBinds) - -buildDefaultMethodBinds e free_tyvars origin clas clas_tyvar_tmpl - default_method_ids default_binds - = -- Deal with the method declarations themselves - processInstBinds e - free_tyvars - (makeClassDeclDefaultMethodRhs clas origin default_method_ids) - [] -- No tyvars in scope for "this inst decl" - [] -- No insts available - default_method_ids - default_binds `thenTc` \ (dicts_needed, default_binds') -> - - returnTc (dicts_needed, SingleBind (NonRecBind default_binds')) +tcClassDecls2 :: Module -> [RenamedTyClDecl] -> NF_TcM (LIE, TcMonoBinds) + +tcClassDecls2 this_mod decls + = foldr combine + (returnNF_Tc (emptyLIE, EmptyMonoBinds)) + [tcClassDecl2 cls_decl | cls_decl@(ClassDecl {tcdMeths = Just _}) <- decls] + -- The 'Just' picks out source ClassDecls + where + combine tc1 tc2 = tc1 `thenNF_Tc` \ (lie1, binds1) -> + tc2 `thenNF_Tc` \ (lie2, binds2) -> + returnNF_Tc (lie1 `plusLIE` lie2, + binds1 `AndMonoBinds` binds2) +\end{code} + +@tcClassDecl2@ generates bindings for polymorphic default methods +(generic default methods have by now turned into instance declarations) + +\begin{code} +tcClassDecl2 :: RenamedTyClDecl -- The class declaration + -> NF_TcM (LIE, TcMonoBinds) + +tcClassDecl2 (ClassDecl {tcdName = class_name, tcdSigs = sigs, + tcdMeths = Just default_binds, tcdLoc = src_loc}) + = -- The 'Just' picks out source ClassDecls + recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $ + tcAddSrcLoc src_loc $ + tcLookupClass class_name `thenNF_Tc` \ clas -> + + -- We make a separate binding for each default method. + -- At one time I used a single AbsBinds for all of them, thus + -- AbsBind [d] [dm1, dm2, dm3] { dm1 = ...; dm2 = ...; dm3 = ... } + -- But that desugars into + -- ds = \d -> (..., ..., ...) + -- dm1 = \d -> case ds d of (a,b,c) -> a + -- And since ds is big, it doesn't get inlined, so we don't get good + -- default methods. Better to make separate AbsBinds for each + let + (tyvars, _, _, op_items) = classBigSig clas + prags = filter isPragSig sigs + tc_dm = tcDefMeth clas tyvars default_binds prags + in + 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] -> + + tcExtendTyVarEnvForMeths tyvars clas_tyvars ( + tcMethodBind clas origin clas_tyvars inst_tys theta + binds_in prags False op_item + ) `thenTc` \ (defm_bind, insts_needed, local_dm_inst) -> + + tcAddErrCtxt (defltMethCtxt clas) $ + + -- Check the context + tcSimplifyCheck + (ptext SLIT("class") <+> ppr clas) + clas_tyvars + [this_dict] + insts_needed `thenTc` \ (const_lie, dict_binds) -> + + -- Simplification can do unification + checkSigTyVars clas_tyvars emptyVarSet `thenTc` \ clas_tyvars' -> + + let + full_bind = AbsBinds + clas_tyvars' + [instToId this_dict] + [(clas_tyvars', dm_id, instToId local_dm_inst)] + emptyNameSet -- No inlines (yet) + (dict_binds `andMonoBinds` defm_bind) + in + returnTc (full_bind, const_lie) + where + origin = ClassDeclOrigin \end{code} -@makeClassDeclDefaultMethodRhs@ builds the default method for a -class declaration when no explicit default method is given. + + +%************************************************************************ +%* * +\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} -makeClassDeclDefaultMethodRhs +tcMethodBind :: Class -> InstOrigin - -> [Id] - -> Int - -> NF_TcM TypecheckedExpr + -> [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, Inst) + +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 -> + let + meth_id = instToId meth + meth_name = idName meth_id + sig_msg = ptext SLIT("When checking the expected type for class method") <+> ppr sel_id + meth_prags = find_prags (idName sel_id) meth_name prags + in + mkTcSig meth_id loc `thenNF_Tc` \ sig_info -> + + -- Figure out what method binding to use + -- If the user suppplied one, use it, else construct a default one + (case find_bind (idName sel_id) meth_name meth_binds of + Just user_bind -> returnTc user_bind + Nothing -> mkDefMethRhs is_inst_decl clas inst_tys sel_id loc dm_info `thenTc` \ rhs -> + returnTc (FunMonoBind meth_name False -- Not infix decl + [mkSimpleMatch [] rhs 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} -makeClassDeclDefaultMethodRhs clas origin method_ids tag - = specTy origin (getIdUniType method_id) `thenNF_Tc` \ (tyvars, dicts, tau) -> - returnNF_Tc (mkTyLam tyvars ( - mkDictLam (map mkInstId dicts) ( - App (mkTyApp (Var pAT_ERROR_ID) [tau]) - (Lit (StringLit (_PK_ error_msg)))))) - where - method_id = method_ids !! (tag-1) - class_op = (getClassOps clas) !! (tag-1) +\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 and errors +~~~~~~~~~~~~~~~~~~~ +\begin{code} +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")]) - error_msg = "%D" -- => No default method for \" - ++ unencoded_part_of_msg +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)] - unencoded_part_of_msg = escErrorMsg ( - _UNPK_ clas_mod ++ "." ++ _UNPK_ clas_name ++ "." - ++ (ppShow 80 (ppr PprForUser class_op)) - ++ "\"" ) +mixedGenericErr op + = ptext SLIT("Can't mix generic and non-generic equations for class method") <+> quotes (ppr op) - (clas_mod, clas_name) = getOrigName clas +genericMultiParamErr clas + = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+> + ptext SLIT("cannot have generic methods") \end{code}