X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcInstDcls.lhs;h=991767a4615f8b1330bdd80a6ab40ed8ca19d5dd;hb=34df35343c166dea72507b5d626d7ca792d436c9;hp=0d43182c0f093959a411cb2f93e3258784858be1;hpb=f9120c200bcf613b58d742802172fb4c08171f0d;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcInstDcls.lhs b/ghc/compiler/typecheck/TcInstDcls.lhs index 0d43182..991767a 100644 --- a/ghc/compiler/typecheck/TcInstDcls.lhs +++ b/ghc/compiler/typecheck/TcInstDcls.lhs @@ -1,83 +1,66 @@ % -% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996 +% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % \section[TcInstDecls]{Typechecking instance declarations} \begin{code} +module TcInstDcls ( tcInstDecls1, tcInstDecls2 ) where + #include "HsVersions.h" -module TcInstDcls ( - tcInstDecls1, - tcInstDecls2, - processInstBinds - ) where - - -import Ubiq - -import HsSyn ( InstDecl(..), FixityDecl, Sig(..), - SpecInstSig(..), HsBinds(..), Bind(..), - MonoBinds(..), GRHSsAndBinds, Match, - InPat(..), OutPat(..), HsExpr(..), HsLit(..), - Stmt, Qual, ArithSeqInfo, Fake, - PolyType(..), MonoType ) -import RnHsSyn ( RenamedHsBinds(..), RenamedMonoBinds(..), - RenamedInstDecl(..), RenamedFixityDecl(..), - RenamedSig(..), RenamedSpecInstSig(..), - RnName(..){-incl instance Outputable-} +import HsSyn ( HsDecl(..), InstDecl(..), + HsBinds(..), MonoBinds(..), + HsExpr(..), InPat(..), HsLit(..), Sig(..), + andMonoBindList + ) +import RnHsSyn ( RenamedHsBinds, RenamedInstDecl, RenamedHsDecl ) +import TcHsSyn ( TcMonoBinds, + maybeBoxedPrimType ) -import TcHsSyn ( TcIdOcc(..), TcHsBinds(..), - TcMonoBinds(..), TcExpr(..), tcIdType, - mkHsTyLam, mkHsTyApp, - mkHsDictLam, mkHsDictApp ) - +import TcBinds ( tcSpecSigs ) +import TcClassDcl ( tcMethodBind, checkFromThisClass ) import TcMonad -import GenSpecEtc ( checkSigTyVars ) -import Inst ( Inst, InstOrigin(..), InstanceMapper(..), - newDicts, newMethod, LIE(..), emptyLIE, plusLIE ) -import TcBinds ( tcPragmaSigs ) +import RnMonad ( RnNameSupply, Fixities ) +import Inst ( Inst, InstOrigin(..), + newDicts, LIE, emptyLIE, plusLIE, plusLIEs ) import TcDeriv ( tcDeriving ) -import TcEnv ( tcLookupClass, tcTyVarScope, newLocalId ) -import TcGRHSs ( tcGRHSsAndBinds ) -import TcInstUtil ( InstInfo(..), mkInstanceRelatedIds, buildInstanceEnvs ) -import TcKind ( TcKind, unifyKind ) -import TcMatches ( tcMatchesFun ) -import TcMonoType ( tcContext, tcMonoTypeKind ) -import TcSimplify ( tcSimplifyAndCheck, tcSimplifyThetas ) -import TcType ( TcType(..), TcTyVar(..), - tcInstSigTyVars, tcInstType, tcInstTheta +import TcEnv ( ValueEnv, tcExtendGlobalValEnv, tcExtendTyVarEnvForMeths, + tcAddImportedIdInfo, tcInstId ) -import Unify ( unifyTauTy ) - +import TcInstUtil ( InstInfo(..), classDataCon ) +import TcMonoType ( tcHsTopType ) +import TcSimplify ( tcSimplifyAndCheck ) +import TcType ( TcTyVar, zonkTcTyVarBndr ) import Bag ( emptyBag, unitBag, unionBags, unionManyBags, - concatBag, foldBag, bagToList ) -import CmdLineOpts ( opt_GlasgowExts, opt_CompilingPrelude, - opt_OmitDefaultInstanceMethods, - opt_SpecialiseOverloaded ) -import Class ( GenClass, GenClassOp, - isCcallishClass, getClassBigSig, - getClassOps, getClassOpLocalType ) -import CoreUtils ( escErrorMsg ) -import Id ( GenId, idType, isDefaultMethodId_maybe ) -import ListSetOps ( minusList ) -import Maybes ( maybeToBool, expectJust ) -import Outputable ( getLocalName, getOrigName ) -import PrelInfo ( pAT_ERROR_ID ) -import PprType ( GenType, GenTyVar, GenClass, GenClassOp, TyCon, - pprParendGenType ) -import PprStyle -import Pretty -import RnUtils ( GlobalNameMappers(..), GlobalNameMapper(..) ) -import TyCon ( derivedFor ) -import Type ( GenType(..), ThetaType(..), mkTyVarTys, - splitSigmaTy, splitAppTy, isTyVarTy, matchTy, mkSigmaTy, - getTyCon_maybe, maybeBoxedPrimType ) -import TyVar ( GenTyVar, mkTyVarSet ) + foldBag, Bag + ) +import CmdLineOpts ( opt_GlasgowExts, opt_AllowUndecidableInstances ) +import Class ( classBigSig, Class ) +import Var ( idName, idType, Id, TyVar ) +import DataCon ( isNullaryDataCon, splitProductType_maybe, dataConId ) +import Maybes ( maybeToBool, catMaybes, expectJust ) +import MkId ( mkDictFunId ) +import Module ( ModuleName ) +import Name ( isLocallyDefined, NamedThing(..) ) +import NameSet ( emptyNameSet ) +import PrelInfo ( eRROR_ID ) +import PprType ( pprConstraint ) +import SrcLoc ( SrcLoc ) +import TyCon ( isSynTyCon, isDataTyCon, tyConDerivings ) +import Type ( Type, isUnLiftedType, mkTyVarTys, + splitSigmaTy, isTyVarTy, + splitTyConApp_maybe, splitDictTy_maybe, unUsgTy, + splitAlgTyConApp_maybe, + tyVarsOfTypes + ) +import Subst ( mkTopTyVarSubst, substTheta ) +import VarSet ( mkVarSet, varSetElems ) +import TysPrim ( byteArrayPrimTyCon, mutableByteArrayPrimTyCon ) import TysWiredIn ( stringTy ) -import Unique ( Unique ) -import Util ( panic ) +import Unique ( Unique, cCallableClassKey, cReturnableClassKey, Uniquable(..) ) +import Outputable \end{code} Typechecking instance declarations is done in two passes. The first @@ -154,99 +137,71 @@ and $dbinds_super$ bind the superclass dictionaries sd1 \ldots sdm. \end{enumerate} \begin{code} -tcInstDecls1 :: Bag RenamedInstDecl - -> [RenamedSpecInstSig] - -> Module -- module name for deriving - -> GlobalNameMappers -- renamer fns for deriving - -> [RenamedFixityDecl] -- fixities for deriving +tcInstDecls1 :: ValueEnv -- Contains IdInfo for dfun ids + -> [RenamedHsDecl] + -> ModuleName -- module name for deriving + -> Fixities + -> RnNameSupply -- for renaming derivings -> TcM s (Bag InstInfo, - RenamedHsBinds, - PprStyle -> Pretty) + RenamedHsBinds) -tcInstDecls1 inst_decls specinst_sigs mod_name renamer_name_funs fixities +tcInstDecls1 unf_env decls mod_name fixs rn_name_supply = -- Do the ordinary instance declarations - mapBagNF_Tc (tcInstDecl1 mod_name) inst_decls - `thenNF_Tc` \ inst_info_bags -> + mapNF_Tc (tcInstDecl1 unf_env) + [inst_decl | InstD inst_decl <- decls] `thenNF_Tc` \ inst_info_bags -> let - decl_inst_info = concatBag inst_info_bags + decl_inst_info = unionManyBags inst_info_bags in -- Handle "derived" instances; note that we only do derivings -- for things in this module; we ignore deriving decls from - -- interfaces! We pass fixities, because they may be used - -- in deriving Read and Show. - tcDeriving mod_name renamer_name_funs decl_inst_info fixities - `thenTc` \ (deriv_inst_info, deriv_binds, ddump_deriv) -> + -- interfaces! + tcDeriving mod_name fixs rn_name_supply decl_inst_info + `thenTc` \ (deriv_inst_info, deriv_binds) -> let - inst_info = deriv_inst_info `unionBags` decl_inst_info - in -{- LATER - -- Handle specialise instance pragmas - tcSpecInstSigs inst_info specinst_sigs - `thenTc` \ spec_inst_info -> --} - let - spec_inst_info = emptyBag -- For now - - full_inst_info = inst_info `unionBags` spec_inst_info + full_inst_info = deriv_inst_info `unionBags` decl_inst_info in - returnTc (full_inst_info, deriv_binds, ddump_deriv) + returnTc (full_inst_info, deriv_binds) -tcInstDecl1 :: FAST_STRING -> RenamedInstDecl -> NF_TcM s (Bag InstInfo) +tcInstDecl1 :: ValueEnv -> RenamedInstDecl -> NF_TcM s (Bag InstInfo) -tcInstDecl1 mod_name - (InstDecl class_name - poly_ty@(HsForAllTy tyvar_names context inst_ty) - binds - from_here inst_mod uprags pragmas src_loc) +tcInstDecl1 unf_env (InstDecl poly_ty binds uprags dfun_name src_loc) = -- Prime error recovery, set source location recoverNF_Tc (returnNF_Tc emptyBag) $ tcAddSrcLoc src_loc $ - -- Look things up - tcLookupClass class_name `thenNF_Tc` \ (clas_kind, clas) -> - + -- Type-check all the stuff before the "where" + tcHsTopType poly_ty `thenTc` \ poly_ty' -> let - de_rn (RnName n) = n + (tyvars, theta, dict_ty) = splitSigmaTy poly_ty' + (clas, inst_tys) = case splitDictTy_maybe dict_ty of + Nothing -> pprPanic "tcInstDecl1" (ppr poly_ty) + Just pair -> pair in - -- Typecheck the context and instance type - tcTyVarScope (map de_rn tyvar_names) (\ tyvars -> - tcContext context `thenTc` \ theta -> - tcMonoTypeKind inst_ty `thenTc` \ (tau_kind, tau) -> - unifyKind clas_kind tau_kind `thenTc_` - returnTc (tyvars, theta, tau) - ) `thenTc` \ (inst_tyvars, inst_theta, inst_tau) -> - - -- Check for respectable instance type - scrutiniseInstanceType from_here clas inst_tau - `thenTc` \ (inst_tycon,arg_tys) -> - - -- Deal with the case where we are deriving - -- and importing the same instance - if (not from_here && (clas `derivedFor` inst_tycon) - && all isTyVarTy arg_tys) - then - if not opt_CompilingPrelude && maybeToBool inst_mod && - mod_name == expectJust "inst_mod" inst_mod - then - -- Imported instance came from this module; - -- discard and derive fresh instance - returnTc emptyBag - else - -- Imported instance declared in another module; - -- report duplicate instance error - failTc (derivingWhenInstanceImportedErr inst_mod clas inst_tycon) - else - -- Make the dfun id and constant-method ids - mkInstanceRelatedIds from_here inst_mod pragmas - clas inst_tyvars inst_tau inst_theta uprags - `thenTc` \ (dfun_id, dfun_theta, const_meth_ids) -> + -- Check for respectable instance type, and context + -- but only do this for non-imported instance decls. + -- Imported ones should have been checked already, and may indeed + -- contain something illegal in normal Haskell, notably + -- instance CCallable [Char] + (if isLocallyDefined dfun_name then + scrutiniseInstanceHead clas inst_tys `thenNF_Tc_` + mapNF_Tc scrutiniseInstanceConstraint theta + else + returnNF_Tc [] + ) `thenNF_Tc_` + + -- Make the dfun id + let + dfun_id = mkDictFunId dfun_name clas tyvars inst_tys theta - returnTc (unitBag (InstInfo clas inst_tyvars inst_tau inst_theta - dfun_theta dfun_id const_meth_ids - binds from_here inst_mod src_loc uprags)) + -- Add info from interface file + final_dfun_id = tcAddImportedIdInfo unf_env dfun_id + in + returnTc (unitBag (InstInfo clas tyvars inst_tys theta + final_dfun_id + binds src_loc uprags)) \end{code} @@ -258,15 +213,15 @@ tcInstDecl1 mod_name \begin{code} tcInstDecls2 :: Bag InstInfo - -> NF_TcM s (LIE s, TcHsBinds s) + -> NF_TcM s (LIE, TcMonoBinds) tcInstDecls2 inst_decls - = foldBag combine tcInstDecl2 (returnNF_Tc (emptyLIE, EmptyBinds)) inst_decls + = foldBag combine tcInstDecl2 (returnNF_Tc (emptyLIE, EmptyMonoBinds)) inst_decls where combine tc1 tc2 = tc1 `thenNF_Tc` \ (lie1, binds1) -> tc2 `thenNF_Tc` \ (lie2, binds2) -> returnNF_Tc (lie1 `plusLIE` lie2, - binds1 `ThenBinds` binds2) + binds1 `AndMonoBinds` binds2) \end{code} @@ -337,545 +292,187 @@ is the @dfun_theta@ below. First comes the easy case of a non-local instance decl. \begin{code} -tcInstDecl2 :: InstInfo - -> NF_TcM s (LIE s, TcHsBinds s) - -tcInstDecl2 (InstInfo _ _ _ _ _ _ _ _ False{-import-} _ _ _) +tcInstDecl2 :: InstInfo -> NF_TcM s (LIE, TcMonoBinds) + +tcInstDecl2 (InstInfo clas inst_tyvars inst_tys + inst_decl_theta + dfun_id monobinds + locn uprags) + | not (isLocallyDefined dfun_id) + = returnNF_Tc (emptyLIE, EmptyMonoBinds) + +{- + -- I deleted this "optimisation" because when importing these + -- instance decls the renamer would look for the dfun bindings and they weren't there. + -- This would be fixable, but it seems simpler just to produce a tiny void binding instead, + -- even though it's never used. + + -- This case deals with CCallable etc, which don't need any bindings + | isNoDictClass clas = returnNF_Tc (emptyLIE, EmptyBinds) +-} -tcInstDecl2 (InstInfo clas inst_tyvars inst_ty - inst_decl_theta dfun_theta - dfun_id const_meth_ids monobinds - True{-here-} inst_mod locn uprags) + | otherwise = -- Prime error recovery - recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyBinds)) $ - tcAddSrcLoc locn $ - - -- Get the class signature - tcInstSigTyVars inst_tyvars `thenNF_Tc` \ (inst_tyvars', _, tenv) -> - let - (class_tyvar, - super_classes, sc_sel_ids, - class_ops, op_sel_ids, defm_ids) = getClassBigSig clas - in - tcInstType tenv inst_ty `thenNF_Tc` \ inst_ty' -> - tcInstTheta tenv dfun_theta `thenNF_Tc` \ dfun_theta' -> - tcInstTheta tenv inst_decl_theta `thenNF_Tc` \ inst_decl_theta' -> + recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $ + tcAddSrcLoc locn $ + + -- Instantiate the instance decl with tc-style type variables + tcInstId dfun_id `thenNF_Tc` \ (inst_tyvars', dfun_theta', dict_ty') -> let - sc_theta' = super_classes `zip` (repeat inst_ty') - origin = InstanceDeclOrigin - mk_method sel_id = newMethodId sel_id inst_ty' origin locn + (clas, inst_tys') = expectJust "tcInstDecl2" (splitDictTy_maybe dict_ty') + + origin = InstanceDeclOrigin + + (class_tyvars, + sc_theta, sc_sel_ids, + op_sel_ids, defm_ids) = classBigSig clas + + -- Instantiate the theta found in the original instance decl + inst_decl_theta' = substTheta (mkTopTyVarSubst inst_tyvars (mkTyVarTys inst_tyvars')) + inst_decl_theta + + -- Instantiate the super-class context with inst_tys + sc_theta' = substTheta (mkTopTyVarSubst class_tyvars inst_tys') sc_theta in -- Create dictionary Ids from the specified instance contexts. newDicts origin sc_theta' `thenNF_Tc` \ (sc_dicts, sc_dict_ids) -> newDicts origin dfun_theta' `thenNF_Tc` \ (dfun_arg_dicts, dfun_arg_dicts_ids) -> newDicts origin inst_decl_theta' `thenNF_Tc` \ (inst_decl_dicts, _) -> - newDicts origin [(clas,inst_ty')] `thenNF_Tc` \ (this_dict, [this_dict_id]) -> + newDicts origin [(clas,inst_tys')] `thenNF_Tc` \ (this_dict, [this_dict_id]) -> - -- Create method variables - mapAndUnzipNF_Tc mk_method op_sel_ids `thenNF_Tc` \ (meth_insts_s, meth_ids) -> + -- Check that all the method bindings come from this class + checkFromThisClass clas op_sel_ids monobinds `thenNF_Tc_` - -- Collect available Insts + tcExtendTyVarEnvForMeths inst_tyvars inst_tyvars' ( + tcExtendGlobalValEnv (catMaybes defm_ids) ( + -- Default-method Ids may be mentioned in synthesised RHSs + + mapAndUnzip3Tc (tcMethodBind clas origin inst_tyvars' inst_tys' inst_decl_theta' + monobinds uprags True) + (op_sel_ids `zip` defm_ids) + )) `thenTc` \ (method_binds_s, insts_needed_s, meth_lies_w_ids) -> + + -- Deal with SPECIALISE instance pragmas by making them + -- look like SPECIALISE pragmas for the dfun let - avail_insts -- These insts are in scope; quite a few, eh? - = unionManyBags (this_dict : dfun_arg_dicts : meth_insts_s) - - mk_method_expr - = if opt_OmitDefaultInstanceMethods then - makeInstanceDeclNoDefaultExpr origin meth_ids defm_ids inst_ty' clas inst_mod - else - makeInstanceDeclDefaultMethodExpr origin meth_ids defm_ids inst_ty' this_dict_id + dfun_prags = [SpecSig (idName dfun_id) ty loc | SpecInstSig ty loc <- uprags] in - processInstBinds mk_method_expr inst_tyvars' avail_insts meth_ids monobinds - `thenTc` \ (insts_needed, method_mbinds) -> + tcExtendGlobalValEnv [dfun_id] ( + tcSpecSigs dfun_prags + ) `thenTc` \ (prag_binds, prag_lie) -> + + -- Check the overloading constraints of the methods and superclasses + + -- tcMethodBind has checked that the class_tyvars havn't + -- been unified with each other or another type, but we must + -- still zonk them + mapNF_Tc zonkTcTyVarBndr inst_tyvars' `thenNF_Tc` \ zonked_inst_tyvars -> let - -- Create the dict and method binds - dict_bind - = VarMonoBind this_dict_id (Dictionary sc_dict_ids meth_ids) + inst_tyvars_set = mkVarSet zonked_inst_tyvars + + (meth_lies, meth_ids) = unzip meth_lies_w_ids - dict_and_method_binds - = dict_bind `AndMonoBinds` method_mbinds + -- These insts are in scope; quite a few, eh? + avail_insts = this_dict `plusLIE` + dfun_arg_dicts `plusLIE` + sc_dicts `plusLIE` + unionManyBags meth_lies - inst_tyvars_set' = mkTyVarSet inst_tyvars' + methods_lie = plusLIEs insts_needed_s in - -- Check the overloading constraints of the methods and superclasses - tcAddErrCtxt (bindSigCtxt meth_ids) ( - tcSimplifyAndCheck - inst_tyvars_set' -- Local tyvars - avail_insts - (sc_dicts `unionBags` insts_needed) -- Need to get defns for all these - ) `thenTc` \ (const_lie, super_binds) -> + -- Ditto method bindings + tcAddErrCtxt methodCtxt ( + tcSimplifyAndCheck + (ptext SLIT("instance declaration context")) + inst_tyvars_set -- Local tyvars + avail_insts + methods_lie + ) `thenTc` \ (const_lie1, lie_binds1) -> + -- Check that we *could* construct the superclass dictionaries, -- even though we are *actually* going to pass the superclass dicts in; - -- the check ensures that the caller will never have a problem building - -- them. - tcAddErrCtxt superClassSigCtxt ( - tcSimplifyAndCheck - inst_tyvars_set' -- Local tyvars + -- the check ensures that the caller will never have + --a problem building them. + tcAddErrCtxt superClassCtxt ( + tcSimplifyAndCheck + (ptext SLIT("instance declaration context")) + inst_tyvars_set -- Local tyvars inst_decl_dicts -- The instance dictionaries available sc_dicts -- The superclass dicationaries reqd - ) `thenTc_` - -- Ignore the result; we're only doing + ) `thenTc` \ _ -> + -- Ignore the result; we're only doing -- this to make sure it can be done. - -- Now process any SPECIALIZE pragmas for the methods - let - spec_sigs = [ s | s@(SpecSig _ _ _ _) <- uprags ] - in - tcPragmaSigs spec_sigs `thenTc` \ (_, spec_binds, spec_lie) -> + -- Now do the simplification again, this time to get the + -- bindings; this time we use an enhanced "avails" + -- Ignore errors because they come from the *previous* tcSimplify + discardErrsTc ( + tcSimplifyAndCheck + (ptext SLIT("instance declaration context")) + inst_tyvars_set + dfun_arg_dicts -- NB! Don't include this_dict here, else the sc_dicts + -- get bound by just selecting from this_dict!! + sc_dicts + ) `thenTc` \ (const_lie2, lie_binds2) -> + + + -- Create the result bindings let - -- Complete the binding group, adding any spec_binds - inst_binds + dict_constr = classDataCon clas + scs_and_meths = sc_dict_ids ++ meth_ids + + dict_rhs + | null scs_and_meths + = -- Blatant special case for CCallable, CReturnable + -- If the dictionary is empty then we should never + -- select anything from it, so we make its RHS just + -- emit an error message. This in turn means that we don't + -- mention the constructor, which doesn't exist for CCallable, CReturnable + -- Hardly beautiful, but only three extra lines. + HsApp (TyApp (HsVar eRROR_ID) [(unUsgTy . idType) this_dict_id]) + (HsLitOut (HsString msg) stringTy) + + | otherwise -- The common case + = foldl HsApp (TyApp (HsVar (dataConId dict_constr)) inst_tys') + (map HsVar (sc_dict_ids ++ meth_ids)) + -- We don't produce a binding for the dict_constr; instead we + -- rely on the simplifier to unfold this saturated application + -- We do this rather than generate an HsCon directly, because + -- it means that the special cases (e.g. dictionary with only one + -- member) are dealt with by the common MkId.mkDataConId code rather + -- than needing to be repeated here. + + where + msg = _PK_ ("Compiler error: bad dictionary " ++ showSDoc (ppr clas)) + + dict_bind = VarMonoBind this_dict_id dict_rhs + method_binds = andMonoBindList method_binds_s + + main_bind = AbsBinds - inst_tyvars' + zonked_inst_tyvars dfun_arg_dicts_ids - ((this_dict_id, RealId dfun_id) - : (meth_ids `zip` (map RealId const_meth_ids))) - -- const_meth_ids will often be empty - super_binds - (RecBind dict_and_method_binds) - - `ThenBinds` - spec_binds - in - - returnTc (const_lie `plusLIE` spec_lie, inst_binds) -\end{code} - -@mkMethodId@ manufactures an id for a local method. -It's rather turgid stuff, because there are two cases: - - (a) For methods with no local polymorphism, we can make an Inst of the - class-op selector function and a corresp InstId; - which is good because then other methods which call - this one will do so directly. - - (b) For methods with local polymorphism, we can't do this. For example, - - class Foo a where - op :: (Num b) => a -> b -> a - - Here the type of the class-op-selector is - - forall a b. (Foo a, Num b) => a -> b -> a - - The locally defined method at (say) type Float will have type - - forall b. (Num b) => Float -> b -> Float - - and the one is not an instance of the other. - - So for these we just make a local (non-Inst) id with a suitable type. - -How disgusting. - -\begin{code} -newMethodId sel_id inst_ty origin loc - = let (sel_tyvars,sel_theta,sel_tau) = splitSigmaTy (idType sel_id) - (_:meth_theta) = sel_theta -- The local theta is all except the - -- first element of the context - in - case sel_tyvars of - -- Ah! a selector for a class op with no local polymorphism - -- Build an Inst for this - [clas_tyvar] -> newMethod origin (RealId sel_id) [inst_ty] - - -- Ho! a selector for a class op with local polymorphism. - -- Just make a suitably typed local id for this - (clas_tyvar:local_tyvars) -> - tcInstType [(clas_tyvar,inst_ty)] - (mkSigmaTy local_tyvars meth_theta sel_tau) - `thenNF_Tc` \ method_ty -> - newLocalId (getLocalName sel_id) method_ty `thenNF_Tc` \ meth_id -> - returnNF_Tc (emptyLIE, meth_id) -\end{code} - -The next function makes a default method which calls the global default method, at -the appropriate instance type. - -See the notes under default decls in TcClassDcl.lhs. - -\begin{code} -makeInstanceDeclDefaultMethodExpr - :: InstOrigin s - -> [TcIdOcc s] - -> [Id] - -> TcType s - -> TcIdOcc s - -> Int - -> NF_TcM s (TcExpr s) - -makeInstanceDeclDefaultMethodExpr origin meth_ids defm_ids inst_ty this_dict tag - = newDicts origin op_theta `thenNF_Tc` \ (op_lie,op_dicts) -> - - -- def_op_id = /\ op_tyvars -> \ op_dicts -> - -- defm_id inst_ty op_tyvars this_dict op_dicts - returnNF_Tc ( - mkHsTyLam op_tyvars ( - mkHsDictLam op_dicts ( - mkHsDictApp (mkHsTyApp (HsVar (RealId defm_id)) - (inst_ty : mkTyVarTys op_tyvars)) - (this_dict : op_dicts) - ))) - where - idx = tag - 1 - meth_id = meth_ids !! idx - defm_id = defm_ids !! idx - (op_tyvars, op_theta, op_tau) = splitSigmaTy (tcIdType meth_id) - -makeInstanceDeclNoDefaultExpr - :: InstOrigin s - -> [TcIdOcc s] - -> [Id] - -> TcType s - -> Class - -> Maybe Module - -> Int - -> NF_TcM s (TcExpr s) - -makeInstanceDeclNoDefaultExpr origin meth_ids defm_ids inst_ty clas inst_mod tag - = newDicts origin op_theta `thenNF_Tc` \ (op_lie, op_dicts) -> - - -- Produce a warning if the default instance method - -- has been omitted when one exists in the class - warnTc (not err_defm_ok) - (omitDefaultMethodWarn clas_op clas_name inst_ty) - `thenNF_Tc_` - returnNF_Tc (mkHsTyLam op_tyvars ( - mkHsDictLam op_dicts ( - HsApp (mkHsTyApp (HsVar (RealId pAT_ERROR_ID)) [op_tau]) - (HsLitOut (HsString (_PK_ error_msg)) stringTy)))) - where - idx = tag - 1 - meth_id = meth_ids !! idx - clas_op = (getClassOps clas) !! idx - defm_id = defm_ids !! idx - (op_tyvars,op_theta,op_tau) = splitSigmaTy (tcIdType meth_id) - - Just (_, _, err_defm_ok) = isDefaultMethodId_maybe defm_id - - error_msg = "%E" -- => No explicit method for \" - ++ escErrorMsg error_str - - mod_str = case inst_mod of { Nothing -> SLIT("Prelude"); Just m -> m } - - error_str = _UNPK_ mod_str ++ "." ++ _UNPK_ clas_name ++ "." - ++ (ppShow 80 (ppr PprForUser inst_ty)) ++ "." - ++ (ppShow 80 (ppr PprForUser clas_op)) ++ "\"" - - (_, clas_name) = getOrigName clas -\end{code} - - -%************************************************************************ -%* * -\subsection{Processing each method} -%* * -%************************************************************************ - -@processInstBinds@ returns a @MonoBinds@ which binds -all the method ids (which are passed in). It is used - - both for instance decls, - - and to compile the default-method declarations in a class decl. - -Any method ids which don't have a binding have a suitable default -binding created for them. The actual right-hand side used is -created using a function which is passed in, because the right thing to -do differs between instance and class decls. - -\begin{code} -processInstBinds - :: (Int -> NF_TcM s (TcExpr s)) -- Function to make default method - -> [TcTyVar s] -- Tyvars for this instance decl - -> LIE s -- available Insts - -> [TcIdOcc s] -- Local method ids in tag order - -- (instance tyvars are free in their types) - -> RenamedMonoBinds - -> TcM s (LIE s, -- These are required - TcMonoBinds s) - -processInstBinds mk_default_method_rhs inst_tyvars avail_insts method_ids monobinds - = - -- Process the explicitly-given method bindings - processInstBinds1 inst_tyvars avail_insts method_ids monobinds - `thenTc` \ (tags, insts_needed_in_methods, method_binds) -> - - -- Find the methods not handled, and make default method bindings for them. - let - unmentioned_tags = [1.. length method_ids] `minusList` tags + [(inst_tyvars', dfun_id, this_dict_id)] + emptyNameSet -- No inlines (yet) + (lie_binds1 `AndMonoBinds` + lie_binds2 `AndMonoBinds` + method_binds `AndMonoBinds` + dict_bind) in - mapNF_Tc mk_default_method unmentioned_tags - `thenNF_Tc` \ default_bind_list -> - - returnTc (insts_needed_in_methods, - foldr AndMonoBinds method_binds default_bind_list) - where - -- From a tag construct us the passed-in function to construct - -- the binding for the default method - mk_default_method tag = mk_default_method_rhs tag `thenNF_Tc` \ rhs -> - returnNF_Tc (VarMonoBind (method_ids !! (tag-1)) rhs) -\end{code} - -\begin{code} -processInstBinds1 - :: [TcTyVar s] -- Tyvars for this instance decl - -> LIE s -- available Insts - -> [TcIdOcc s] -- Local method ids in tag order (instance tyvars are free), - -> RenamedMonoBinds - -> TcM s ([Int], -- Class-op tags accounted for - LIE s, -- These are required - TcMonoBinds s) - -processInstBinds1 inst_tyvars avail_insts method_ids EmptyMonoBinds - = returnTc ([], emptyLIE, EmptyMonoBinds) - -processInstBinds1 inst_tyvars avail_insts method_ids (AndMonoBinds mb1 mb2) - = processInstBinds1 inst_tyvars avail_insts method_ids mb1 - `thenTc` \ (op_tags1,dicts1,method_binds1) -> - processInstBinds1 inst_tyvars avail_insts method_ids mb2 - `thenTc` \ (op_tags2,dicts2,method_binds2) -> - returnTc (op_tags1 ++ op_tags2, - dicts1 `unionBags` dicts2, - AndMonoBinds method_binds1 method_binds2) -\end{code} - -\begin{code} -processInstBinds1 inst_tyvars avail_insts method_ids mbind - = - -- Find what class op is being defined here. The complication is - -- that we could have a PatMonoBind or a FunMonoBind. If the - -- former, it should only bind a single variable, or else we're in - -- trouble (I'm not sure what the static semantics of methods - -- defined in a pattern binding with multiple patterns is!) - -- Renamer has reduced us to these two cases. - let - (op,locn) = case mbind of - FunMonoBind op _ locn -> (op, locn) - PatMonoBind (VarPatIn op) _ locn -> (op, locn) - - occ = getLocalName op - origin = InstanceDeclOrigin - in - tcAddSrcLoc locn $ - - -- Make a method id for the method - let tag = panic "processInstBinds1:getTagFromClassOpName"{-getTagFromClassOpName op-} - method_id = method_ids !! (tag-1) - - TcId method_bndr = method_id - method_ty = idType method_bndr - (method_tyvars, method_theta, method_tau) = splitSigmaTy method_ty - in - newDicts origin method_theta `thenNF_Tc` \ (method_dicts,method_dict_ids) -> - - case (method_tyvars, method_dict_ids) of - - ([],[]) -> -- The simple case; no local polymorphism or overloading in the method - - -- Type check the method itself - tcMethodBind method_id method_tau mbind `thenTc` \ (mbind', lieIop) -> - returnTc ([tag], lieIop, mbind') - - other -> -- It's a locally-polymorphic and/or overloaded method; UGH! - - -- Make a new id for (a) the local, non-overloaded method - -- and (b) the locally-overloaded method - -- The latter is needed just so we can return an AbsBinds wrapped - -- up inside a MonoBinds. - - newLocalId occ method_tau `thenNF_Tc` \ local_id -> - newLocalId occ method_ty `thenNF_Tc` \ copy_id -> - let - inst_method_tyvars = inst_tyvars ++ method_tyvars - in - -- Typecheck the method - tcMethodBind local_id method_tau mbind `thenTc` \ (mbind', lieIop) -> - - -- Check the overloading part of the signature. - -- Simplify everything fully, even though some - -- constraints could "really" be left to the next - -- level out. The case which forces this is - -- - -- class Foo a where { op :: Bar a => a -> a } - -- - -- Here we must simplify constraints on "a" to catch all - -- the Bar-ish things. - tcAddErrCtxt (methodSigCtxt op method_ty) ( - tcSimplifyAndCheck - (mkTyVarSet inst_method_tyvars) - (method_dicts `plusLIE` avail_insts) - lieIop - ) `thenTc` \ (f_dicts, dict_binds) -> - - returnTc ([tag], - f_dicts, - VarMonoBind method_id - (HsLet - (AbsBinds - method_tyvars - method_dict_ids - [(local_id, copy_id)] - dict_binds - (NonRecBind mbind')) - (HsVar copy_id))) -\end{code} - -\begin{code} -tcMethodBind :: TcIdOcc s -> TcType s -> RenamedMonoBinds - -> TcM s (TcMonoBinds s, LIE s) - -tcMethodBind meth_id meth_ty (FunMonoBind name matches locn) - = tcMatchesFun name meth_ty matches `thenTc` \ (rhs', lie) -> - returnTc (FunMonoBind meth_id rhs' locn, lie) - -tcMethodBind meth_id meth_ty pbind@(PatMonoBind pat grhss_and_binds locn) - -- pat is sure to be a (VarPatIn op) - = tcAddErrCtxt (patMonoBindsCtxt pbind) $ - tcGRHSsAndBinds grhss_and_binds `thenTc` \ (grhss_and_binds', lie, rhs_ty) -> - unifyTauTy meth_ty rhs_ty `thenTc_` - returnTc (PatMonoBind (VarPat meth_id) grhss_and_binds' locn, lie) + returnTc (const_lie1 `plusLIE` const_lie2 `plusLIE` prag_lie, + main_bind `AndMonoBinds` prag_binds) \end{code} %************************************************************************ %* * -\subsection{Type-checking specialise instance pragmas} +\subsection{Checking for a decent instance type} %* * %************************************************************************ -\begin{code} -{- LATER -tcSpecInstSigs :: E -> CE -> TCE - -> Bag InstInfo -- inst decls seen (declared and derived) - -> [RenamedSpecInstSig] -- specialise instance upragmas - -> TcM (Bag InstInfo) -- new, overlapped, inst decls - -tcSpecInstSigs e ce tce inst_infos [] - = returnTc emptyBag - -tcSpecInstSigs e ce tce inst_infos sigs - = buildInstanceEnvs inst_infos `thenTc` \ inst_mapper -> - tc_inst_spec_sigs inst_mapper sigs `thenNF_Tc` \ spec_inst_infos -> - returnTc spec_inst_infos - where - tc_inst_spec_sigs inst_mapper [] - = returnNF_Tc emptyBag - tc_inst_spec_sigs inst_mapper (sig:sigs) - = tcSpecInstSig e ce tce inst_infos inst_mapper sig `thenNF_Tc` \ info_sig -> - tc_inst_spec_sigs inst_mapper sigs `thenNF_Tc` \ info_sigs -> - returnNF_Tc (info_sig `unionBags` info_sigs) - -tcSpecInstSig :: E -> CE -> TCE - -> Bag InstInfo - -> InstanceMapper - -> RenamedSpecInstSig - -> NF_TcM (Bag InstInfo) - -tcSpecInstSig e ce tce inst_infos inst_mapper (SpecInstSig class_name ty src_loc) - = recoverTc emptyBag ( - tcAddSrcLoc src_loc ( - let - clas = lookupCE ce class_name -- Renamer ensures this can't fail - - -- Make some new type variables, named as in the specialised instance type - ty_names = extractMonoTyNames (==) ty - (tmpl_e,inst_tmpls,inst_tmpl_tys) = mkTVE ty_names - in - babyTcMtoTcM (tcInstanceType ce tce tmpl_e True src_loc ty) - `thenTc` \ inst_ty -> - let - maybe_tycon = case maybeAppDataTyCon inst_ty of - Just (tc,_,_) -> Just tc - Nothing -> Nothing - - maybe_unspec_inst = lookup_unspec_inst clas maybe_tycon inst_infos - in - -- Check that we have a local instance declaration to specialise - checkMaybeTc maybe_unspec_inst - (specInstUnspecInstNotFoundErr clas inst_ty src_loc) `thenTc_` - - -- Create tvs to substitute for tmpls while simplifying the context - copyTyVars inst_tmpls `thenNF_Tc` \ (tv_e, inst_tvs, inst_tv_tys) -> - let - Just (InstInfo _ unspec_tyvars unspec_inst_ty unspec_theta - _ _ _ binds True{-from here-} mod _ uprag) = maybe_unspec_inst - - subst = case matchTy unspec_inst_ty inst_ty of - Just subst -> subst - Nothing -> panic "tcSpecInstSig:matchTy" - - subst_theta = instantiateThetaTy subst unspec_theta - subst_tv_theta = instantiateThetaTy tv_e subst_theta - - mk_spec_origin clas ty - = InstanceSpecOrigin inst_mapper clas ty src_loc - in - tcSimplifyThetas mk_spec_origin subst_tv_theta - `thenTc` \ simpl_tv_theta -> - let - simpl_theta = [ (clas, tv_to_tmpl tv) | (clas, tv) <- simpl_tv_theta ] - - tv_tmpl_map = inst_tv_tys `zipEqual` inst_tmpl_tys - tv_to_tmpl tv = assoc "tcSpecInstSig" tv_tmpl_map tv - in - mkInstanceRelatedIds e True{-from here-} mod NoInstancePragmas src_loc - clas inst_tmpls inst_ty simpl_theta uprag - `thenTc` \ (dfun_id, dfun_theta, const_meth_ids) -> - - getSwitchCheckerTc `thenNF_Tc` \ sw_chkr -> - (if sw_chkr SpecialiseTrace then - pprTrace "Specialised Instance: " - (ppAboves [ppCat [if null simpl_theta then ppNil else ppr PprDebug simpl_theta, - if null simpl_theta then ppNil else ppStr "=>", - ppr PprDebug clas, - pprParendGenType PprDebug inst_ty], - ppCat [ppStr " derived from:", - if null unspec_theta then ppNil else ppr PprDebug unspec_theta, - if null unspec_theta then ppNil else ppStr "=>", - ppr PprDebug clas, - pprParendGenType PprDebug unspec_inst_ty]]) - else id) ( - - returnTc (unitBag (InstInfo clas inst_tmpls inst_ty simpl_theta - dfun_theta dfun_id const_meth_ids - binds True{-from here-} mod src_loc uprag)) - ))) - - -lookup_unspec_inst clas maybe_tycon inst_infos - = case filter (match_info match_inst_ty) (bagToList inst_infos) of - [] -> Nothing - (info:_) -> Just info - where - match_info match_ty (InstInfo inst_clas _ inst_ty _ _ _ _ _ from_here _ _ _) - = from_here && clas == inst_clas && - match_ty inst_ty && is_plain_instance inst_ty - - match_inst_ty = case maybe_tycon of - Just tycon -> match_tycon tycon - Nothing -> match_fun - - match_tycon tycon inst_ty = case (maybeAppDataTyCon inst_ty) of - Just (inst_tc,_,_) -> tycon == inst_tc - Nothing -> False - - match_fun inst_ty = isFunType inst_ty - - -is_plain_instance inst_ty - = case (maybeAppDataTyCon inst_ty) of - Just (_,tys,_) -> all isTyVarTemplateTy tys - Nothing -> case maybeUnpackFunTy inst_ty of - Just (arg, res) -> isTyVarTemplateTy arg && isTyVarTemplateTy res - Nothing -> error "TcInstDecls:is_plain_instance" --} -\end{code} - - -Checking for a decent instance type -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -@scrutiniseInstanceType@ checks the type {\em and} its syntactic constraints: +@scrutiniseInstanceHead@ checks the type {\em and} its syntactic constraints: it must normally look like: @instance Foo (Tycon a b c ...) ...@ The exceptions to this syntactic checking: (1)~if the @GlasgowExts@ @@ -885,94 +482,143 @@ compiled elsewhere). In these cases, we let them go through anyway. We can also have instances for functions: @instance Foo (a -> b) ...@. \begin{code} -scrutiniseInstanceType from_here clas inst_tau - -- TYCON CHECK - | not (maybeToBool inst_tycon_maybe) - = failTc (instTypeErr inst_tau) - - -- IMPORTED INSTANCES ARE OK (but see tcInstDecl1) - | from_here - = returnTc (inst_tycon,arg_tys) - - -- TYVARS CHECK - | not (all isTyVarTy arg_tys || - not from_here || - opt_GlasgowExts) - = failTc (instTypeErr inst_tau) +scrutiniseInstanceConstraint (clas, tys) + | all isTyVarTy tys + || opt_AllowUndecidableInstances = returnNF_Tc () + | otherwise = addErrTc (instConstraintErr clas tys) + +scrutiniseInstanceHead clas inst_taus + | -- CCALL CHECK (a).... urgh! + -- To verify that a user declaration of a CCallable/CReturnable + -- instance is OK, we must be able to see the constructor(s) + -- of the instance type (see next guard.) + -- + -- We flag this separately to give a more precise error msg. + -- + (getUnique clas == cCallableClassKey || getUnique clas == cReturnableClassKey) + && is_alg_tycon_app && not constructors_visible + = addErrTc (invisibleDataConPrimCCallErr clas first_inst_tau) + + | -- CCALL CHECK (b) + -- A user declaration of a CCallable/CReturnable instance + -- must be for a "boxed primitive" type. + (getUnique clas == cCallableClassKey && not (ccallable_type first_inst_tau)) || + (getUnique clas == cReturnableClassKey && not (creturnable_type first_inst_tau)) + = addErrTc (nonBoxedPrimCCallErr clas first_inst_tau) -- DERIVING CHECK -- It is obviously illegal to have an explicit instance -- for something that we are also planning to `derive' - -- Though we can have an explicit instance which is more - -- specific than the derived instance - | clas `derivedFor` inst_tycon - && all isTyVarTy arg_tys - = failTc (derivingWhenInstanceExistsErr clas inst_tycon) - - | -- CCALL CHECK - -- A user declaration of a _CCallable/_CReturnable instance - -- must be for a "boxed primitive" type. - isCcallishClass clas - && not opt_CompilingPrelude -- which allows anything - && maybeToBool (maybeBoxedPrimType inst_tau) - = failTc (nonBoxedPrimCCallErr clas inst_tau) + | maybeToBool alg_tycon_app_maybe && clas `elem` (tyConDerivings alg_tycon) + = addErrTc (derivingWhenInstanceExistsErr clas first_inst_tau) + -- Kind check will have ensured inst_taus is of length 1 + + -- Allow anything for AllowUndecidableInstances + | opt_AllowUndecidableInstances + = returnNF_Tc () + + -- If GlasgowExts then check at least one isn't a type variable + | opt_GlasgowExts + = if all isTyVarTy inst_taus then + addErrTc (instTypeErr clas inst_taus (text "There must be at least one non-type-variable in the instance head")) + else + returnNF_Tc () + + -- WITH HASKELL 1.4, MUST HAVE C (T a b c) + | not (length inst_taus == 1 && + maybeToBool maybe_tycon_app && -- Yes, there's a type constuctor + not (isSynTyCon tycon) && -- ...but not a synonym + all isTyVarTy arg_tys && -- Applied to type variables + length (varSetElems (tyVarsOfTypes arg_tys)) == length arg_tys + -- This last condition checks that all the type variables are distinct + ) + = addErrTc (instTypeErr clas inst_taus + (text "the instance type must be of form (T a b c)" $$ + text "where T is not a synonym, and a,b,c are distinct type variables") + ) | otherwise - = returnTc (inst_tycon,arg_tys) + = returnNF_Tc () where - (possible_tycon, arg_tys) = splitAppTy inst_tau - inst_tycon_maybe = getTyCon_maybe possible_tycon - inst_tycon = expectJust "tcInstDecls1:inst_tycon" inst_tycon_maybe -\end{code} + (first_inst_tau : _) = inst_taus -\begin{code} + -- Stuff for algebraic or -> type + maybe_tycon_app = splitTyConApp_maybe first_inst_tau + Just (tycon, arg_tys) = maybe_tycon_app -instTypeErr ty sty - = case ty of - SynTy tc _ _ -> ppBesides [ppStr "The type synonym `", ppr sty tc, rest_of_msg] - TyVarTy tv -> ppBesides [ppStr "The type variable `", ppr sty tv, rest_of_msg] - other -> ppBesides [ppStr "The type `", ppr sty ty, rest_of_msg] - where - rest_of_msg = ppStr "' cannot be used as an instance type." - -derivingWhenInstanceExistsErr clas tycon sty - = ppHang (ppBesides [ppStr "Deriving class `", ppr sty clas, ppStr "' type `", ppr sty tycon, ppStr "'"]) - 4 (ppStr "when an explicit instance exists") - -derivingWhenInstanceImportedErr inst_mod clas tycon sty - = ppHang (ppBesides [ppStr "Deriving class `", ppr sty clas, ppStr "' type `", ppr sty tycon, ppStr "'"]) - 4 (ppBesides [ppStr "when an instance declared in module `", pp_mod, ppStr "' has been imported"]) - where - pp_mod = case inst_mod of - Nothing -> ppPStr SLIT("the standard Prelude") - Just m -> ppBesides [ppStr "module `", ppPStr m, ppStr "'"] + -- Stuff for an *algebraic* data type + alg_tycon_app_maybe = splitAlgTyConApp_maybe first_inst_tau + -- The "Alg" part looks through synonyms + is_alg_tycon_app = maybeToBool alg_tycon_app_maybe + Just (alg_tycon, _, data_cons) = alg_tycon_app_maybe -nonBoxedPrimCCallErr clas inst_ty sty - = ppHang (ppStr "Instance isn't for a `boxed-primitive' type") - 4 (ppBesides [ ppStr "class `", ppr sty clas, ppStr "' type `", - ppr sty inst_ty, ppStr "'"]) + constructors_visible = not (null data_cons) + -omitDefaultMethodWarn clas_op clas_name inst_ty sty - = ppCat [ppStr "Warning: Omitted default method for", - ppr sty clas_op, ppStr "in instance", - ppPStr clas_name, pprParendGenType sty inst_ty] +-- These conditions come directly from what the DsCCall is capable of. +-- Totally grotesque. Green card should solve this. +ccallable_type ty = isUnLiftedType ty || -- Allow CCallable Int# etc + maybeToBool (maybeBoxedPrimType ty) || -- Ditto Int etc + ty == stringTy || + byte_arr_thing + where + byte_arr_thing = case splitProductType_maybe ty of + Just (tycon, ty_args, data_con, [data_con_arg_ty1, data_con_arg_ty2, data_con_arg_ty3]) -> + maybeToBool maybe_arg3_tycon && + (arg3_tycon == byteArrayPrimTyCon || + arg3_tycon == mutableByteArrayPrimTyCon) + where + maybe_arg3_tycon = splitTyConApp_maybe data_con_arg_ty3 + Just (arg3_tycon,_) = maybe_arg3_tycon + + other -> False + +creturnable_type ty = maybeToBool (maybeBoxedPrimType ty) || + -- Or, a data type with a single nullary constructor + case (splitAlgTyConApp_maybe ty) of + Just (tycon, tys_applied, [data_con]) + -> isNullaryDataCon data_con + other -> False +\end{code} -patMonoBindsCtxt pbind sty - = ppHang (ppStr "In a pattern binding:") - 4 (ppr sty pbind) - -methodSigCtxt name ty sty - = ppHang (ppBesides [ppStr "When matching the definition of class method `", - ppr sty name, ppStr "' to its signature :" ]) - 4 (ppr sty ty) - -bindSigCtxt method_ids sty - = ppHang (ppStr "When checking type signatures for: ") - 4 (ppInterleave (ppStr ", ") (map (ppr sty) method_ids)) - -superClassSigCtxt sty - = ppStr "When checking superclass constraints on instance declaration" - +\begin{code} +instConstraintErr clas tys + = hang (ptext SLIT("Illegal constaint") <+> + quotes (pprConstraint clas tys) <+> + ptext SLIT("in instance context")) + 4 (ptext SLIT("(Instance contexts must constrain only type variables)")) + +instTypeErr clas tys msg + = sep [ptext SLIT("Illegal instance declaration for") <+> quotes (pprConstraint clas tys), + nest 4 (parens msg) + ] + +derivingWhenInstanceExistsErr clas tycon + = hang (hsep [ptext SLIT("Deriving class"), + quotes (ppr clas), + ptext SLIT("type"), quotes (ppr tycon)]) + 4 (ptext SLIT("when an explicit instance exists")) + +nonBoxedPrimCCallErr clas inst_ty + = hang (ptext SLIT("Unacceptable instance type for ccall-ish class")) + 4 (hsep [ ptext SLIT("class"), ppr clas, ptext SLIT("type"), + ppr inst_ty]) + +{- + Declaring CCallable & CReturnable instances in a module different + from where the type was defined. Caused by importing data type + abstractly (either programmatically or by the renamer being over-eager + in its pruning.) +-} +invisibleDataConPrimCCallErr clas inst_ty + = hang (hsep [ptext SLIT("Constructors for"), quotes (ppr inst_ty), + ptext SLIT("not visible when checking"), + quotes (ppr clas), ptext SLIT("instance")]) + 4 (hsep [text "(Try either importing", ppr inst_ty, + text "non-abstractly or compile using -fno-prune-tydecls ..)"]) + +methodCtxt = ptext SLIT("When checking the methods of an instance declaration") +superClassCtxt = ptext SLIT("When checking the superclasses of an instance declaration") \end{code}