X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcInstDcls.lhs;h=5d1e63ae0e6f4f38ba1e76e94036568e62aeab21;hp=b4d34983680bd4b8c80b155c8ddc3a91a5cee5f7;hb=6d2b0ae3ae3296cb6cdd496cbf85b897c7ce150b;hpb=e3dd39bf230380f02d73efc287226117bb2eb47f diff --git a/compiler/typecheck/TcInstDcls.lhs b/compiler/typecheck/TcInstDcls.lhs index b4d3498..5d1e63a 100644 --- a/compiler/typecheck/TcInstDcls.lhs +++ b/compiler/typecheck/TcInstDcls.lhs @@ -6,6 +6,13 @@ TcInstDecls: Typechecking instance declarations \begin{code} +{-# OPTIONS -w #-} +-- The above warning supression flag is a temporary kludge. +-- While working on this module you are encouraged to remove it and fix +-- any warnings in the module. See +-- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings +-- for details + module TcInstDcls ( tcInstDecls1, tcInstDecls2 ) where #include "HsVersions.h" @@ -29,6 +36,7 @@ import TcSimplify import Type import Coercion import TyCon +import TypeRep import DataCon import Class import Var @@ -179,7 +187,10 @@ tcInstDecls1 tycl_decls inst_decls deriv_decls -- (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 deriv_decls + -- NB: class instance declarations can contain derivings as + -- part of associated data type declarations + ; (deriv_inst_info, deriv_binds) <- tcDeriving tycl_decls inst_decls + deriv_decls ; addInsts deriv_inst_info $ do { ; gbl_env <- getGblEnv @@ -252,9 +263,11 @@ tcLocalInstDecl1 decl@(L loc (InstDecl poly_ty binds uprags ats)) -- Finally, construct the Core representation of the instance. -- (This no longer includes the associated types.) - ; dfun_name <- newDFunName clas inst_tys (srcSpanStart loc) + ; dfun_name <- newDFunName clas inst_tys loc ; overlap_flag <- getOverlapFlag - ; let dfun = mkDictFunId dfun_name tyvars theta clas inst_tys + ; let (eq_theta,dict_theta) = partition isEqPred theta + theta' = eq_theta ++ dict_theta + dfun = mkDictFunId dfun_name tyvars theta' clas inst_tys ispec = mkLocalInstance dfun overlap_flag ; return ([InstInfo { iSpec = ispec, @@ -390,39 +403,37 @@ tcInstDecls2 tycl_decls inst_decls The main purpose of @tcInstDecl2@ is to return a @HsBinds@ which defines the dictionary function for this instance declaration. For example -\begin{verbatim} + instance Foo a => Foo [a] where op1 x = ... op2 y = ... -\end{verbatim} + might generate something like -\begin{verbatim} + dfun.Foo.List dFoo_a = let op1 x = ... op2 y = ... in Dict [op1, op2] -\end{verbatim} HOWEVER, if the instance decl has no context, then it returns a bigger @HsBinds@ with declarations for each method. For example -\begin{verbatim} + instance Foo [a] where op1 x = ... op2 y = ... -\end{verbatim} + might produce -\begin{verbatim} + dfun.Foo.List a = Dict [Foo.op1.List a, Foo.op2.List a] const.Foo.op1.List a x = ... const.Foo.op2.List a y = ... -\end{verbatim} + This group may be mutually recursive, because (for example) there may be no method supplied for op2 in which case we'll get -\begin{verbatim} + const.Foo.op2.List a = default.Foo.op2 (dfun.Foo.List a) -\end{verbatim} -that is, the default method applied to the dictionary at this type. +that is, the default method applied to the dictionary at this type. What we actually produce in either case is: AbsBinds [a] [dfun_theta_dicts] @@ -434,7 +445,6 @@ What we actually produce in either case is: The "maybe" says that we only ask AbsBinds to make global constant methods if the dfun_theta is empty. - For an instance declaration, say, @@ -450,8 +460,6 @@ Notice that we pass it the superclass dictionaries at the instance type; this is the ``Mark Jones optimisation''. The stuff before the "=>" here is the @dfun_theta@ below. -First comes the easy case of a non-local instance decl. - \begin{code} tcInstDecl2 :: InstInfo -> TcM (LHsBinds Id) @@ -460,23 +468,23 @@ tcInstDecl2 :: InstInfo -> TcM (LHsBinds Id) ------------------------ -- Derived newtype instances; surprisingly tricky! -- --- In the case of a newtype, things are rather easy -- class Show a => Foo a b where ... --- newtype T a = MkT (Tree [a]) deriving( Foo Int ) +-- newtype N a = MkN (Tree [a]) deriving( Foo Int ) +-- -- The newtype gives an FC axiom looking like --- axiom CoT a :: T a :=: Tree [a] +-- axiom CoN a :: N a :=: Tree [a] -- (see Note [Newtype coercions] in TyCon for this unusual form of axiom) -- -- 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 (sym (CoT a))) of +-- dfunFooT :: forall a. (Foo Int (Tree [a], Show (N a)) => Foo Int (N a) +-- dfunFooT = /\a. \(ds:Show (N a)) (df:Foo (Tree [a])). +-- case df `cast` (Foo Int (sym (CoN a))) of -- Foo _ op1 .. opn -> Foo ds op1 .. opn -- -- If there are no superclasses, matters are simpler, because we don't need the case -- see Note [Newtype deriving superclasses] in TcDeriv.lhs -tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = NewTypeDerived mb_preds }) +tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = NewTypeDerived }) = do { let dfun_id = instanceDFunId ispec rigid_info = InstSkol origin = SigOrigin rigid_info @@ -484,46 +492,43 @@ tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = NewTypeDerived mb_preds }) ; (tvs, theta, inst_head_ty) <- tcSkolSigType rigid_info inst_ty -- inst_head_ty is a PredType - ; inst_loc <- getInstLoc origin - ; (rep_dict_id : sc_dict_ids, wrap_fn, sc_binds) - <- make_wrapper inst_loc tvs theta mb_preds - -- Here, we are relying on the order of dictionary - -- arguments built by NewTypeDerived in TcDeriv; - -- namely, that the rep_dict_id comes first - ; let (cls, cls_inst_tys) = tcSplitDFunHead inst_head_ty - cls_tycon = classTyCon cls - the_coercion = make_coercion cls_tycon cls_inst_tys - coerced_rep_dict = mkHsWrap the_coercion (HsVar rep_dict_id) - - ; body <- make_body cls_tycon cls_inst_tys sc_dict_ids coerced_rep_dict + (class_tyvars, sc_theta, _, op_items) = classBigSig cls + cls_tycon = classTyCon cls + sc_theta' = substTheta (zipOpenTvSubst class_tyvars cls_inst_tys) sc_theta + + Just (initial_cls_inst_tys, last_ty) = snocView cls_inst_tys + (nt_tycon, tc_args) = tcSplitTyConApp last_ty -- Can't fail + rep_ty = newTyConInstRhs nt_tycon tc_args + + rep_pred = mkClassPred cls (initial_cls_inst_tys ++ [rep_ty]) + -- In our example, rep_pred is (Foo Int (Tree [a])) + the_coercion = make_coercion cls_tycon initial_cls_inst_tys nt_tycon tc_args + -- Coercion of kind (Foo Int (Tree [a]) ~ Foo Int (N a) - ; return (sc_binds `snocBag` (noLoc $ VarBind dfun_id $ noLoc $ mkHsWrap wrap_fn body)) } + ; inst_loc <- getInstLoc origin + ; sc_loc <- getInstLoc InstScOrigin + ; dfun_dicts <- newDictBndrs inst_loc theta + ; sc_dicts <- newDictBndrs sc_loc sc_theta' + ; this_dict <- newDictBndr inst_loc (mkClassPred cls cls_inst_tys) + ; rep_dict <- newDictBndr inst_loc rep_pred + + -- Figure out bindings for the superclass context from dfun_dicts + -- Don't include this_dict in the 'givens', else + -- wanted_sc_insts get bound by just selecting from this_dict!! + ; sc_binds <- addErrCtxt superClassCtxt $ + tcSimplifySuperClasses inst_loc dfun_dicts (rep_dict:sc_dicts) + + ; let coerced_rep_dict = mkHsWrap the_coercion (HsVar (instToId rep_dict)) + + ; body <- make_body cls_tycon cls_inst_tys sc_dicts coerced_rep_dict + ; let dict_bind = noLoc $ VarBind (instToId this_dict) (noLoc body) + + ; return (unitBag $ noLoc $ + AbsBinds tvs (map instToId dfun_dicts) + [(tvs, dfun_id, instToId this_dict, [])] + (dict_bind `consBag` sc_binds)) } where - - ----------------------- - -- make_wrapper - -- We distinguish two cases: - -- (a) there is no tyvar abstraction in the dfun, so all dicts are constant, - -- and the new dict can just be a constant - -- (mb_preds = Just preds) - -- (b) there are tyvars, so we must make a dict *fun* - -- (mb_preds = Nothing) - -- See the defn of NewTypeDerived for the meaning of mb_preds - make_wrapper inst_loc tvs theta (Just preds) -- Case (a) - = ASSERT( null tvs && null theta ) - do { dicts <- newDictBndrs inst_loc preds - ; sc_binds <- addErrCtxt superClassCtxt $ - tcSimplifySuperClasses inst_loc [] dicts - -- Use tcSimplifySuperClasses to avoid creating loops, for the - -- same reason as Note [SUPERCLASS-LOOP 1] in TcSimplify - ; return (map instToId dicts, idHsWrapper, sc_binds) } - - make_wrapper inst_loc tvs theta Nothing -- Case (b) - = do { dicts <- newDictBndrs inst_loc theta - ; let dict_ids = map instToId dicts - ; return (dict_ids, mkWpTyLams tvs <.> mkWpLams dict_ids, emptyBag) } - ----------------------- -- make_coercion -- The inst_head looks like (C s1 .. sm (T a1 .. ak)) @@ -533,25 +538,24 @@ tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = NewTypeDerived mb_preds }) -- So we just replace T with CoT, and insert a 'sym' -- NB: we know that k will be >= arity of CoT, because the latter fully eta-reduced - make_coercion cls_tycon cls_inst_tys - | Just (all_tys_but_last, last_ty) <- snocView cls_inst_tys - , (tycon, tc_args) <- tcSplitTyConApp last_ty -- Should not fail - , Just co_con <- newTyConCo_maybe tycon + make_coercion cls_tycon initial_cls_inst_tys nt_tycon tc_args + | Just co_con <- newTyConCo_maybe nt_tycon , let co = mkSymCoercion (mkTyConApp co_con tc_args) - = WpCo (mkTyConApp cls_tycon (all_tys_but_last ++ [co])) + = WpCo (mkTyConApp cls_tycon (initial_cls_inst_tys ++ [co])) | otherwise -- The newtype is transparent; no need for a cast = idHsWrapper ----------------------- - -- make_body - -- Two cases; see Note [Newtype deriving superclasses] in TcDeriv.lhs - -- (a) no superclasses; then we can just use the coerced dict - -- (b) one or more superclasses; then new need to do the unpack/repack + -- (make_body C tys scs coreced_rep_dict) + -- returns + -- (case coerced_rep_dict of { C _ ops -> C scs ops }) + -- But if there are no superclasses, it returns just coerced_rep_dict + -- See Note [Newtype deriving superclasses] in TcDeriv.lhs - make_body cls_tycon cls_inst_tys sc_dict_ids coerced_rep_dict - | null sc_dict_ids -- Case (a) + make_body cls_tycon cls_inst_tys sc_dicts coerced_rep_dict + | null sc_dicts -- Case (a) = return coerced_rep_dict - | otherwise -- Case (b) + | otherwise -- Case (b) = do { op_ids <- newSysLocalIds FSLIT("op") op_tys ; dummy_sc_dict_ids <- newSysLocalIds FSLIT("sc") (map idType sc_dict_ids) ; let the_pat = ConPatOut { pat_con = noLoc cls_data_con, pat_tvs = [], @@ -569,6 +573,7 @@ tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = NewTypeDerived mb_preds }) ; return (HsCase (noLoc coerced_rep_dict) $ MatchGroup [the_match] (mkFunTy pat_ty pat_ty)) } where + sc_dict_ids = map instToId sc_dicts pat_ty = mkTyConApp cls_tycon cls_inst_tys cls_data_con = head (tyConDataCons cls_tycon) cls_arg_tys = dataConInstArgTys cls_data_con cls_inst_tys @@ -582,10 +587,11 @@ tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = VanillaInst monobinds uprags }) dfun_id = instanceDFunId ispec rigid_info = InstSkol inst_ty = idType dfun_id + loc = srcLocSpan (getSrcLoc dfun_id) in -- Prime error recovery recoverM (returnM emptyLHsBinds) $ - setSrcSpan (srcLocSpan (getSrcLoc dfun_id)) $ + setSrcSpan loc $ addErrCtxt (instDeclCtxt2 (idType dfun_id)) $ -- Instantiate the instance decl with skolem constants @@ -599,20 +605,30 @@ tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = VanillaInst monobinds uprags }) -- Instantiate the super-class context with inst_tys sc_theta' = substTheta (zipOpenTvSubst class_tyvars inst_tys') sc_theta + (eq_sc_theta',dict_sc_theta') = partition isEqPred sc_theta' origin = SigOrigin rigid_info + (eq_dfun_theta',dict_dfun_theta') = partition isEqPred dfun_theta' in -- Create dictionary Ids from the specified instance contexts. getInstLoc InstScOrigin `thenM` \ sc_loc -> - newDictBndrs sc_loc sc_theta' `thenM` \ sc_dicts -> + newDictBndrs sc_loc dict_sc_theta' `thenM` \ sc_dicts -> getInstLoc origin `thenM` \ inst_loc -> - newDictBndrs inst_loc dfun_theta' `thenM` \ dfun_arg_dicts -> + mkMetaCoVars eq_sc_theta' `thenM` \ sc_covars -> + mkEqInsts eq_sc_theta' (map mkWantedCo sc_covars) `thenM` \ wanted_sc_eqs -> + mkCoVars eq_dfun_theta' `thenM` \ dfun_covars -> + mkEqInsts eq_dfun_theta' (map mkGivenCo $ mkTyVarTys dfun_covars) `thenM` \ dfun_eqs -> + newDictBndrs inst_loc dict_dfun_theta' `thenM` \ dfun_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. -- Typecheck the methods let -- These insts are in scope; quite a few, eh? - avail_insts = [this_dict] ++ dfun_arg_dicts ++ sc_dicts + dfun_insts = dfun_eqs ++ dfun_dicts + wanted_sc_insts = wanted_sc_eqs ++ sc_dicts + given_sc_eqs = map (updateEqInstCoercion (mkGivenCo . TyVarTy . fromWantedCo "tcInstDecl2") ) wanted_sc_eqs + given_sc_insts = given_sc_eqs ++ sc_dicts + avail_insts = [this_dict] ++ dfun_insts ++ given_sc_insts in tcMethods origin clas inst_tyvars' dfun_theta' inst_tys' avail_insts @@ -620,10 +636,10 @@ tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = VanillaInst monobinds uprags }) -- Figure out bindings for the superclass context -- Don't include this_dict in the 'givens', else - -- sc_dicts get bound by just selecting from this_dict!! + -- wanted_sc_insts get bound by just selecting from this_dict!! addErrCtxt superClassCtxt (tcSimplifySuperClasses inst_loc - dfun_arg_dicts sc_dicts) `thenM` \ sc_binds -> + dfun_insts wanted_sc_insts) `thenM` \ sc_binds -> -- It's possible that the superclass stuff might unified one -- of the inst_tyavars' with something in the envt @@ -637,8 +653,8 @@ tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = VanillaInst monobinds uprags }) dict_constr = classDataCon clas scs_and_meths = map instToId sc_dicts ++ meth_ids this_dict_id = instToId this_dict - inline_prag | null dfun_arg_dicts = [] - | otherwise = [InlinePrag (Inline AlwaysActive True)] + inline_prag | null dfun_insts = [] + | otherwise = [L loc (InlinePrag (Inline AlwaysActive True))] -- Always inline the dfun; this is an experimental decision -- because it makes a big performance difference sometimes. -- Often it means we can do the method selection, and then @@ -651,7 +667,7 @@ tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = VanillaInst monobinds uprags }) -- See Note [Inline dfuns] below dict_rhs - = mkHsConApp dict_constr inst_tys' (map HsVar scs_and_meths) + = mkHsConApp dict_constr (inst_tys' ++ mkTyVarTys sc_covars) (map HsVar scs_and_meths) -- 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 @@ -663,15 +679,25 @@ tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = VanillaInst monobinds uprags }) all_binds = dict_bind `consBag` (sc_binds `unionBags` meth_binds) main_bind = noLoc $ AbsBinds - inst_tyvars' - (map instToId dfun_arg_dicts) - [(inst_tyvars', dfun_id, this_dict_id, - inline_prag ++ prags)] + (inst_tyvars' ++ dfun_covars) + (map instToId dfun_dicts) + [(inst_tyvars' ++ dfun_covars, dfun_id, this_dict_id, inline_prag ++ prags)] all_binds in showLIE (text "instance") `thenM_` returnM (unitBag main_bind) +mkCoVars :: [PredType] -> TcM [TyVar] +mkCoVars = newCoVars . map unEqPred + where + unEqPred (EqPred ty1 ty2) = (ty1, ty2) + unEqPred _ = panic "TcInstDcls.mkCoVars" + +mkMetaCoVars :: [PredType] -> TcM [TyVar] +mkMetaCoVars = mappM eqPredToCoVar + where + eqPredToCoVar (EqPred ty1 ty2) = newMetaCoVar ty1 ty2 + eqPredToCoVar _ = panic "TcInstDcls.mkMetaCoVars" tcMethods origin clas inst_tyvars' dfun_theta' inst_tys' avail_insts op_items monobinds uprags