X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcInstDcls.lhs;h=6135ca249b4c6ddfb5c9e21ba8f3223d48a2f3c3;hp=6ff97e36af653ab014f2f60de7ea2d79c2758286;hb=138b885a335734039daf7debb0a7dfc3dc947c00;hpb=d937e740b0c861a40243a83ac119de76775bd880 diff --git a/compiler/typecheck/TcInstDcls.lhs b/compiler/typecheck/TcInstDcls.lhs index 6ff97e3..6135ca2 100644 --- a/compiler/typecheck/TcInstDcls.lhs +++ b/compiler/typecheck/TcInstDcls.lhs @@ -10,34 +10,55 @@ module TcInstDcls ( tcInstDecls1, tcInstDecls2 ) where import HsSyn import TcBinds ( mkPragFun, tcPrags, badBootDeclErr ) -import TcClassDcl ( tcMethodBind, mkMethodBind, badMethodErr, - tcClassDecl2, getGenericInstances ) +import TcTyClsDecls ( tcIdxTyInstDecl ) +import TcClassDcl ( tcMethodBind, mkMethodBind, badMethodErr, badATErr, + omittedATWarn, tcClassDecl2, getGenericInstances ) import TcRnMonad -import TcMType ( tcSkolSigType, checkValidInstance, checkValidInstHead ) -import TcType ( mkClassPred, tcSplitSigmaTy, tcSplitDFunHead, mkTyVarTys, - SkolemInfo(InstSkol), tcSplitDFunTy ) -import Inst ( tcInstClassOp, newDicts, instToId, showLIE, +import TcMType ( tcSkolSigType, checkValidInstance, + checkValidInstHead ) +import TcType ( TcType, mkClassPred, tcSplitSigmaTy, + tcSplitDFunHead, SkolemInfo(InstSkol), + tcSplitDFunTy, mkFunTy ) +import Inst ( newDictBndr, newDictBndrs, instToId, showLIE, getOverlapFlag, tcExtendLocalInstEnv ) import InstEnv ( mkLocalInstance, instanceDFunId ) +import FamInst ( tcExtendLocalFamInstEnv ) +import FamInstEnv ( extractFamInsts ) import TcDeriv ( tcDeriving ) import TcEnv ( InstInfo(..), InstBindings(..), - newDFunName, tcExtendIdEnv + newDFunName, tcExtendIdEnv, tcExtendGlobalEnv ) import TcHsType ( kcHsSigType, tcHsKindedType ) import TcUnify ( checkSigTyVars ) -import TcSimplify ( tcSimplifyCheck, tcSimplifySuperClasses ) -import Type ( zipOpenTvSubst, substTheta, substTys ) -import DataCon ( classDataCon ) -import Class ( classBigSig ) -import Var ( Id, idName, idType ) +import TcSimplify ( tcSimplifySuperClasses ) +import Type ( zipOpenTvSubst, substTheta, mkTyConApp, mkTyVarTy, + splitFunTys, TyThing(ATyCon), isTyVarTy, tcEqType, + substTys, emptyTvSubst, extendTvSubst ) +import Coercion ( mkSymCoercion ) +import TyCon ( TyCon, tyConName, newTyConCo_maybe, tyConTyVars, + isTyConAssoc, tyConFamInst_maybe, + assocTyConArgPoss_maybe ) +import DataCon ( classDataCon, dataConTyCon, dataConInstArgTys ) +import Class ( Class, classBigSig, classATs ) +import Var ( TyVar, Id, idName, idType, tyVarKind, tyVarName ) +import VarEnv ( rnBndrs2, mkRnEnv2, emptyInScopeSet ) +import Id ( mkSysLocal ) +import UniqSupply ( uniqsFromSupply, splitUniqSupply ) import MkId ( mkDictFunId ) -import Name ( Name, getSrcLoc ) -import Maybe ( catMaybes ) -import SrcLoc ( srcLocSpan, unLoc, noLoc, Located(..), srcSpanStart ) +import Name ( Name, getSrcLoc, nameOccName ) +import NameSet ( addListToNameSet, emptyNameSet, minusNameSet, + nameSetToList ) +import Maybe ( isNothing, fromJust, catMaybes ) +import Monad ( when ) +import List ( find ) +import DynFlags ( DynFlag(Opt_WarnMissingMethods) ) +import SrcLoc ( srcLocSpan, unLoc, noLoc, Located(..), srcSpanStart, + getLoc) import ListSetOps ( minusList ) import Outputable import Bag import BasicTypes ( Activation( AlwaysActive ), InlineSpec(..) ) +import HscTypes ( implicitTyThings ) import FastString \end{code} @@ -133,52 +154,92 @@ tcInstDecls1 -- Deal with both source-code and imported instance decls tcInstDecls1 tycl_decls inst_decls = checkNoErrs $ - -- Stop if addInstInfos etc discovers any errors - -- (they recover, so that we get more than one error each round) - - -- (1) Do the ordinary instance declarations - mappM tcLocalInstDecl1 inst_decls `thenM` \ local_inst_infos -> - - let - local_inst_info = catMaybes local_inst_infos - clas_decls = filter (isClassDecl.unLoc) tycl_decls - in - -- (2) Instances from generic class declarations - getGenericInstances clas_decls `thenM` \ generic_inst_info -> - - -- Next, construct the instance environment so far, consisting of - -- a) local instance decls - -- b) generic instances - addInsts local_inst_info $ - addInsts generic_inst_info $ - - -- (3) Compute instances from "deriving" clauses; - -- This stuff computes a context for the derived instance decl, so it - -- needs to know about all the instances possible; hence inst_env4 - tcDeriving tycl_decls `thenM` \ (deriv_inst_info, deriv_binds) -> - addInsts deriv_inst_info $ - - getGblEnv `thenM` \ gbl_env -> - returnM (gbl_env, - generic_inst_info ++ deriv_inst_info ++ local_inst_info, - deriv_binds) + do { -- Stop if addInstInfos etc discovers any errors + -- (they recover, so that we get more than one error each + -- round) + + -- (1) Do class instance declarations and instances of indexed + -- types + ; let { idxty_decls = filter (isIdxTyDecl . unLoc) tycl_decls } + ; local_info_tycons <- mappM tcLocalInstDecl1 inst_decls + ; idx_tycons <- mappM tcIdxTyInstDeclTL idxty_decls + + ; let { (local_infos, + at_tycons) = unzip local_info_tycons + ; local_info = concat local_infos + ; at_idx_tycon = concat at_tycons ++ catMaybes idx_tycons + ; clas_decls = filter (isClassDecl.unLoc) tycl_decls + ; implicit_things = concatMap implicitTyThings at_idx_tycon + } + + -- (2) Add the tycons of indexed types and their implicit + -- tythings to the global environment + ; tcExtendGlobalEnv (at_idx_tycon ++ implicit_things) $ do { + + -- (3) Instances from generic class declarations + ; generic_inst_info <- getGenericInstances clas_decls + + -- Next, construct the instance environment so far, consisting + -- of + -- a) local instance decls + -- b) generic instances + -- c) local family instance decls + ; addInsts local_info $ do { + ; addInsts generic_inst_info $ do { + ; addFamInsts at_idx_tycon $ do { + + -- (4) Compute instances from "deriving" clauses; + -- This stuff computes a context for the derived instance + -- decl, so it needs to know about all the instances possible + ; (deriv_inst_info, deriv_binds) <- tcDeriving tycl_decls + ; addInsts deriv_inst_info $ do { + + ; gbl_env <- getGblEnv + ; returnM (gbl_env, + generic_inst_info ++ deriv_inst_info ++ local_info, + deriv_binds) + }}}}}} + where + -- Make sure that toplevel type instance are not for associated types. + -- !!!TODO: Need to perform this check for the TyThing of type functions, + -- too. + tcIdxTyInstDeclTL ldecl@(L loc decl) = + do { tything <- tcIdxTyInstDecl ldecl + ; setSrcSpan loc $ + when (isAssocFamily tything) $ + addErr $ assocInClassErr (tcdName decl) + ; return tything + } + isAssocFamily (Just (ATyCon tycon)) = + case tyConFamInst_maybe tycon of + Nothing -> panic "isAssocFamily: no family?!?" + Just (fam, _) -> isTyConAssoc fam + isAssocFamily (Just _ ) = panic "isAssocFamily: no tycon?!?" + isAssocFamily Nothing = False + +assocInClassErr name = + ptext SLIT("Associated type") <+> quotes (ppr name) <+> + ptext SLIT("must be inside a class instance") addInsts :: [InstInfo] -> TcM a -> TcM a addInsts infos thing_inside = tcExtendLocalInstEnv (map iSpec infos) thing_inside + +addFamInsts :: [TyThing] -> TcM a -> TcM a +addFamInsts tycons thing_inside + = tcExtendLocalFamInstEnv (extractFamInsts tycons) thing_inside \end{code} \begin{code} tcLocalInstDecl1 :: LInstDecl Name - -> TcM (Maybe InstInfo) -- Nothing if there was an error + -> TcM ([InstInfo], [TyThing]) -- [] if there was an error -- A source-file instance declaration -- Type-check all the stuff before the "where" -- -- We check for respectable instance type, and context tcLocalInstDecl1 decl@(L loc (InstDecl poly_ty binds uprags ats)) - -- !!!TODO: Handle the `ats' parameter!!! -=chak = -- Prime error recovery, set source location - recoverM (returnM Nothing) $ + recoverM (returnM ([], [])) $ setSrcSpan loc $ addErrCtxt (instDeclCtxt1 poly_ty) $ @@ -192,15 +253,118 @@ tcLocalInstDecl1 decl@(L loc (InstDecl poly_ty binds uprags ats)) ; poly_ty' <- tcHsKindedType kinded_ty ; let (tyvars, theta, tau) = tcSplitSigmaTy poly_ty' + -- Next, process any associated types. + ; idx_tycons <- mappM tcIdxTyInstDecl ats + + -- Now, check the validity of the instance. ; (clas, inst_tys) <- checkValidInstHead tau ; checkValidInstance tyvars theta clas inst_tys + ; checkValidAndMissingATs clas (tyvars, inst_tys) + (zip ats idx_tycons) + -- Finally, construct the Core representation of the instance. + -- (This no longer includes the associated types.) ; dfun_name <- newDFunName clas inst_tys (srcSpanStart loc) ; overlap_flag <- getOverlapFlag - ; let dfun = mkDictFunId dfun_name tyvars theta clas inst_tys - ispec = mkLocalInstance dfun overlap_flag + ; let dfun = mkDictFunId dfun_name tyvars theta clas inst_tys + ispec = mkLocalInstance dfun overlap_flag - ; return (Just (InstInfo { iSpec = ispec, iBinds = VanillaInst binds uprags })) } + ; return ([InstInfo { iSpec = ispec, + iBinds = VanillaInst binds uprags }], + catMaybes idx_tycons) + } + where + -- We pass in the source form and the type checked form of the ATs. We + -- really need the source form only to be able to produce more informative + -- error messages. + checkValidAndMissingATs :: Class + -> ([TyVar], [TcType]) -- instance types + -> [(LTyClDecl Name, -- source form of AT + Maybe TyThing)] -- Core form of AT + -> TcM () + checkValidAndMissingATs clas inst_tys ats + = do { -- Issue a warning for each class AT that is not defined in this + -- instance. + ; let classDefATs = listToNameSet . map tyConName . classATs $ clas + definedATs = listToNameSet . map (tcdName.unLoc.fst) $ ats + omitted = classDefATs `minusNameSet` definedATs + ; warn <- doptM Opt_WarnMissingMethods + ; mapM_ (warnTc warn . omittedATWarn) (nameSetToList omitted) + + -- Ensure that all AT indexes that correspond to class parameters + -- coincide with the types in the instance head. All remaining + -- AT arguments must be variables. Also raise an error for any + -- type instances that are not associated with this class. + ; mapM_ (checkIndexes clas inst_tys) ats + } + + checkIndexes _ _ (hsAT, Nothing) = + return () -- skip, we already had an error here + checkIndexes clas inst_tys (hsAT, Just (ATyCon tycon)) = +-- !!!TODO: check that this does the Right Thing for indexed synonyms, too! + checkIndexes' clas inst_tys hsAT + (tyConTyVars tycon, + snd . fromJust . tyConFamInst_maybe $ tycon) + checkIndexes _ _ _ = panic "checkIndexes" + + checkIndexes' clas (instTvs, instTys) hsAT (atTvs, atTys) + = let atName = tcdName . unLoc $ hsAT + in + setSrcSpan (getLoc hsAT) $ + addErrCtxt (atInstCtxt atName) $ + case find ((atName ==) . tyConName) (classATs clas) of + Nothing -> addErrTc $ badATErr clas atName -- not in this class + Just atDecl -> + case assocTyConArgPoss_maybe atDecl of + Nothing -> panic "checkIndexes': AT has no args poss?!?" + Just poss -> + + -- The following is tricky! We need to deal with three + -- complications: (1) The AT possibly only uses a subset of + -- the class parameters as indexes and those it uses may be in + -- a different order; (2) the AT may have extra arguments, + -- which must be type variables; and (3) variables in AT and + -- instance head will be different `Name's even if their + -- source lexemes are identical. + -- + -- Re (1), `poss' contains a permutation vector to extract the + -- class parameters in the right order. + -- + -- Re (2), we wrap the (permuted) class parameters in a Maybe + -- type and use Nothing for any extra AT arguments. (First + -- equation of `checkIndex' below.) + -- + -- Re (3), we replace any type variable in the AT parameters + -- that has the same source lexeme as some variable in the + -- instance types with the instance type variable sharing its + -- source lexeme. + -- + let relevantInstTys = map (instTys !!) poss + instArgs = map Just relevantInstTys ++ + repeat Nothing -- extra arguments + renaming = substSameTyVar atTvs instTvs + in + zipWithM_ checkIndex (substTys renaming atTys) instArgs + + checkIndex ty Nothing + | isTyVarTy ty = return () + | otherwise = addErrTc $ mustBeVarArgErr ty + checkIndex ty (Just instTy) + | ty `tcEqType` instTy = return () + | otherwise = addErrTc $ wrongATArgErr ty instTy + + listToNameSet = addListToNameSet emptyNameSet + + substSameTyVar [] _ = emptyTvSubst + substSameTyVar (tv:tvs) replacingTvs = + let replacement = case find (tv `sameLexeme`) replacingTvs of + Nothing -> mkTyVarTy tv + Just rtv -> mkTyVarTy rtv + -- + tv1 `sameLexeme` tv2 = + nameOccName (tyVarName tv1) == nameOccName (tyVarName tv2) + in + extendTvSubst (substSameTyVar tvs replacingTvs) tv replacement \end{code} @@ -305,7 +469,7 @@ First comes the easy case of a non-local instance decl. tcInstDecl2 :: InstInfo -> TcM (LHsBinds Id) -- Returns a binding for the dfun --- +------------------------ -- Derived newtype instances -- -- We need to make a copy of the dictionary we are deriving from @@ -316,12 +480,12 @@ tcInstDecl2 :: InstInfo -> TcM (LHsBinds Id) -- class Show a => Foo a b where ... -- newtype T a = MkT (Tree [a]) deriving( Foo Int ) -- The newtype gives an FC axiom looking like --- axiom CoT a :: Tree [a] = T a +-- axiom CoT a :: T a :=: Tree [a] -- -- So all need is to generate a binding looking like -- dfunFooT :: forall a. (Foo Int (Tree [a], Show (T a)) => Foo Int (T a) -- dfunFooT = /\a. \(ds:Show (T a)) (df:Foo (Tree [a])). --- case df `cast` (Foo Int (CoT a)) of +-- case df `cast` (Foo Int (sym (CoT a))) of -- Foo _ op1 .. opn -> Foo ds op1 .. opn tcInstDecl2 (InstInfo { iSpec = ispec, @@ -330,74 +494,71 @@ tcInstDecl2 (InstInfo { iSpec = ispec, rigid_info = InstSkol dfun_id origin = SigOrigin rigid_info inst_ty = idType dfun_id - maybe_co_con = newTyConCo tycon + ; inst_loc <- getInstLoc origin ; (tvs, theta, inst_head) <- tcSkolSigType rigid_info inst_ty - ; dicts <- newDicts origin theta - ; uniqs <- newUniqueSupply - ; let (rep_dict_id:sc_dict_ids) = map instToId dicts - -- (Here, wee are relying on the order of dictionary + ; dicts <- newDictBndrs inst_loc theta + ; uniqs <- newUniqueSupply + ; let (cls, cls_inst_tys) = tcSplitDFunHead inst_head + ; this_dict <- newDictBndr inst_loc (mkClassPred cls rep_tys) + ; let (rep_dict_id:sc_dict_ids) + | null dicts = [instToId this_dict] + | otherwise = map instToId dicts + + -- (Here, we are relying on the order of dictionary -- arguments built by NewTypeDerived in TcDeriv.) - wrap_fn = CoTyLams tvs <.> CoLams dict_ids - - coerced_rep_dict = mkHsCoerce co_fn (HsVar rep_dict_id) + wrap_fn = mkCoTyLams tvs <.> mkCoLams (rep_dict_id:sc_dict_ids) + + -- we need to find the kind that this class applies to + -- and drop trailing tvs appropriately + cls_kind = tyVarKind (head (reverse (tyConTyVars cls_tycon))) + the_tvs = drop_tail (length (fst (splitFunTys cls_kind))) tvs - body | null sc_dicts = coerced_rep_dict - | otherwise = HsCase coerced_rep_dict $ - MatchGroup [the_match] inst_head - the_match = mkSimpleMatch [the_pat] the_rhs - op_ids = zipWith (mkSysLocal FSLIT("op")) - (uniqsFromSupply uniqs) op_tys - the_pat = ConPatOut { pat_con = cls_data_con, pat_tvs = [], - pat_dicts = map (WildPat . idType) sc_dict_ids, - pat_binds = emptyDictBinds, - pat_args = PrefixCon (map VarPat op_ids), - pat_ty = } - the_rhs = mkHsApps (dataConWrapId cls_data_con) types sc_dict_ids (map HsVar op_ids) - - ; return (unitBag (VarBind dfun_id (mkHsCoerce wrap_fn body))) } - where - co_fn :: ExprCoFn - co_fn | Just co_con <- newTyConCo tycon - = ExprCoFn (mkAppCoercion (mkAppsCoercion tycon rep_tys) - (mkTyConApp co_con tvs)) - | otherwise - = idCoerecion + coerced_rep_dict = mkHsCoerce (co_fn the_tvs cls_tycon cls_inst_tys) (HsVar rep_dict_id) -tcMethods origin clas inst_tyvars' dfun_theta' inst_tys' - avail_insts op_items (NewTypeDerived rep_tys) - = getInstLoc origin `thenM` \ inst_loc -> - mapAndUnzip3M (do_one inst_loc) op_items `thenM` \ (meth_ids, meth_binds, rhs_insts) -> - - tcSimplifyCheck - (ptext SLIT("newtype derived instance")) - inst_tyvars' avail_insts rhs_insts `thenM` \ lie_binds -> + body | null sc_dict_ids = coerced_rep_dict + | otherwise = HsCase (noLoc coerced_rep_dict) $ + MatchGroup [the_match] (mkFunTy in_dict_ty inst_head) + in_dict_ty = mkTyConApp cls_tycon cls_inst_tys - -- I don't think we have to do the checkSigTyVars thing + the_match = mkSimpleMatch [noLoc the_pat] the_rhs + the_rhs = mkHsConApp cls_data_con cls_inst_tys (map HsVar (sc_dict_ids ++ op_ids)) - returnM (meth_ids, lie_binds `unionBags` listToBag meth_binds) + (uniqs1, uniqs2) = splitUniqSupply uniqs + op_ids = zipWith (mkSysLocal FSLIT("op")) + (uniqsFromSupply uniqs1) op_tys + + dict_ids = zipWith (mkSysLocal FSLIT("dict")) + (uniqsFromSupply uniqs2) (map idType sc_dict_ids) + + the_pat = ConPatOut { pat_con = noLoc cls_data_con, pat_tvs = [], + pat_dicts = dict_ids, + pat_binds = emptyLHsBinds, + pat_args = PrefixCon (map nlVarPat op_ids), + pat_ty = in_dict_ty} + + cls_data_con = classDataCon cls + cls_tycon = dataConTyCon cls_data_con + cls_arg_tys = dataConInstArgTys cls_data_con cls_inst_tys + + n_dict_args = if length dicts == 0 then 0 else length dicts - 1 + op_tys = drop n_dict_args cls_arg_tys + + dict = mkHsCoerce wrap_fn body + ; return (unitBag (noLoc $ VarBind dfun_id (noLoc dict))) } where - do_one inst_loc (sel_id, _) - = -- The binding is like "op @ NewTy = op @ RepTy" - -- Make the *binder*, like in mkMethodBind - tcInstClassOp inst_loc sel_id inst_tys' `thenM` \ meth_inst -> - - -- Make the *occurrence on the rhs* - tcInstClassOp inst_loc sel_id rep_tys' `thenM` \ rhs_inst -> - let - meth_id = instToId meth_inst - in - return (meth_id, noLoc (VarBind meth_id (nlHsVar (instToId rhs_inst))), rhs_inst) - - -- Instantiate rep_tys with the relevant type variables - -- This looks a bit odd, because inst_tyvars' are the skolemised version - -- of the type variables in the instance declaration; but rep_tys doesn't - -- have the skolemised version, so we substitute them in here - rep_tys' = substTys subst rep_tys - subst = zipOpenTvSubst inst_tyvars' (mkTyVarTys inst_tyvars') - - + -- For newtype T a = MkT + -- The returned coercion has kind :: C (T a):=:C + co_fn tvs cls_tycon cls_inst_tys | Just co_con <- newTyConCo_maybe tycon + = ExprCoFn (mkTyConApp cls_tycon (drop_tail 1 cls_inst_tys ++ + [mkSymCoercion (mkTyConApp co_con (map mkTyVarTy tvs))])) + | otherwise + = idCoercion + drop_tail n l = take (length l - n) l + +------------------------ +-- Ordinary instances tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = VanillaInst monobinds uprags }) = let @@ -424,9 +585,11 @@ tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = VanillaInst monobinds uprags }) origin = SigOrigin rigid_info in -- Create dictionary Ids from the specified instance contexts. - newDicts InstScOrigin sc_theta' `thenM` \ sc_dicts -> - newDicts origin dfun_theta' `thenM` \ dfun_arg_dicts -> - newDicts origin [mkClassPred clas inst_tys'] `thenM` \ [this_dict] -> + getInstLoc InstScOrigin `thenM` \ sc_loc -> + newDictBndrs sc_loc sc_theta' `thenM` \ sc_dicts -> + getInstLoc origin `thenM` \ inst_loc -> + newDictBndrs inst_loc dfun_theta' `thenM` \ dfun_arg_dicts -> + newDictBndr inst_loc (mkClassPred clas inst_tys') `thenM` \ this_dict -> -- Default-method Ids may be mentioned in synthesised RHSs, -- but they'll already be in the environment. @@ -451,7 +614,7 @@ tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = VanillaInst monobinds uprags }) checkSigTyVars inst_tyvars' `thenM_` -- Deal with 'SPECIALISE instance' pragmas - tcPrags dfun_id (filter isSpecInstLSig prags) `thenM` \ prags -> + tcPrags dfun_id (filter isSpecInstLSig uprags) `thenM` \ prags -> -- Create the result bindings let @@ -551,44 +714,6 @@ tcMethods origin clas inst_tyvars' dfun_theta' inst_tys' mapM tc_method_bind meth_infos `thenM` \ meth_binds_s -> returnM (meth_ids, unionManyBags meth_binds_s) -v v v v v v v -************* - - --- Derived newtype instances -tcMethods origin clas inst_tyvars' dfun_theta' inst_tys' - avail_insts op_items (NewTypeDerived maybe_co rep_tys) - = getInstLoc origin `thenM` \ inst_loc -> - mapAndUnzip3M (do_one inst_loc) op_items `thenM` \ (meth_ids, meth_binds, rhs_insts) -> - - tcSimplifyCheck - (ptext SLIT("newtype derived instance")) - inst_tyvars' avail_insts rhs_insts `thenM` \ lie_binds -> - - -- I don't think we have to do the checkSigTyVars thing - - returnM (meth_ids, lie_binds `unionBags` listToBag meth_binds) - - where - do_one inst_loc (sel_id, _) - = -- The binding is like "op @ NewTy = op @ RepTy" - -- Make the *binder*, like in mkMethodBind - tcInstClassOp inst_loc sel_id inst_tys' `thenM` \ meth_inst -> - - -- Make the *occurrence on the rhs* - tcInstClassOp inst_loc sel_id rep_tys' `thenM` \ rhs_inst -> - let - meth_id = instToId meth_inst - in - return (meth_id, noLoc (VarBind meth_id (nlHsVar (instToId rhs_inst))), rhs_inst) - - -- Instantiate rep_tys with the relevant type variables - -- This looks a bit odd, because inst_tyvars' are the skolemised version - -- of the type variables in the instance declaration; but rep_tys doesn't - -- have the skolemised version, so we substitute them in here - rep_tys' = substTys subst rep_tys - subst = zipOpenTvSubst inst_tyvars' (mkTyVarTys inst_tyvars') -^ ^ ^ ^ ^ ^ ^ \end{code} @@ -703,4 +828,19 @@ instDeclCtxt2 dfun_ty inst_decl_ctxt doc = ptext SLIT("In the instance declaration for") <+> quotes doc superClassCtxt = ptext SLIT("When checking the super-classes of an instance declaration") + +atInstCtxt name = ptext SLIT("In the associated type instance for") <+> + quotes (ppr name) + +mustBeVarArgErr ty = + sep [ ptext SLIT("Arguments that do not correspond to a class parameter") <+> + ptext SLIT("must be variables") + , ptext SLIT("Instead of a variable, found") <+> ppr ty + ] + +wrongATArgErr ty instTy = + sep [ ptext SLIT("Type indexes must match class instance head") + , ptext SLIT("Found") <+> ppr ty <+> ptext SLIT("but expected") <+> + ppr instTy + ] \end{code}