X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Fiface%2FBuildTyCl.lhs;h=8459edf98ad5ec54933f884af52260d3f8fb7dfd;hb=a08b4f85df5fbebc237bb7798cabe3812500e921;hp=8689306e6944324cd63a044810260b9e2d8b5f90;hpb=13cd965d80be5c25dc54534a833df39ab7aa7a12;p=ghc-hetmet.git diff --git a/compiler/iface/BuildTyCl.lhs b/compiler/iface/BuildTyCl.lhs index 8689306..8459edf 100644 --- a/compiler/iface/BuildTyCl.lhs +++ b/compiler/iface/BuildTyCl.lhs @@ -7,19 +7,17 @@ module BuildTyCl ( buildSynTyCon, buildAlgTyCon, buildDataCon, buildClass, - mkAbstractTyConRhs, mkOpenDataTyConRhs, mkOpenNewTyConRhs, + mkAbstractTyConRhs, mkOpenDataTyConRhs, mkNewTyConRhs, mkDataTyConRhs ) where #include "HsVersions.h" import IfaceEnv -import TcRnMonad import DataCon import Var import VarSet -import TysWiredIn import BasicTypes import Name import OccName @@ -28,6 +26,9 @@ import Class import TyCon import Type import Coercion + +import TcRnMonad +import Util ( count ) import Outputable import Data.List @@ -116,10 +117,7 @@ mkAbstractTyConRhs :: AlgTyConRhs mkAbstractTyConRhs = AbstractTyCon mkOpenDataTyConRhs :: AlgTyConRhs -mkOpenDataTyConRhs = OpenTyCon Nothing False - -mkOpenNewTyConRhs :: AlgTyConRhs -mkOpenNewTyConRhs = OpenTyCon Nothing True +mkOpenDataTyConRhs = OpenTyCon Nothing mkDataTyConRhs :: [DataCon] -> AlgTyConRhs mkDataTyConRhs cons @@ -136,22 +134,26 @@ mkNewTyConRhs tycon_name tycon con = Just co_tycon | otherwise = Nothing + ; traceIf (text "mkNewTyConRhs" <+> ppr cocon_maybe) ; return (NewTyCon { data_con = con, nt_rhs = rhs_ty, nt_etad_rhs = (etad_tvs, etad_rhs), - nt_co = cocon_maybe, + nt_co = cocon_maybe } ) } -- Coreview looks through newtypes with a Nothing -- for nt_co, or uses explicit coercions otherwise - nt_rep = mkNewTyConRep tycon rhs_ty }) } where -- If all_coercions is True then we use coercions for all newtypes -- otherwise we use coercions for recursive newtypes and look through -- non-recursive newtypes all_coercions = True tvs = tyConTyVars tycon - rhs_ty = head (dataConInstOrigArgTys con (mkTyVarTys tvs)) + rhs_ty = ASSERT(not (null (dataConInstOrigDictsAndArgTys con (mkTyVarTys tvs)))) + -- head (dataConInstOrigArgTys con (mkTyVarTys tvs)) + head (dataConInstOrigDictsAndArgTys con (mkTyVarTys tvs)) -- Instantiate the data con with the -- type variables from the tycon + -- NB: a newtype DataCon has no existentials; hence the + -- call to dataConInstOrigArgTys has the right type args etad_tvs :: [TyVar] -- Matched lazily, so that mkNewTypeCoercion can etad_rhs :: Type -- return a TyCon without pulling on rhs_ty @@ -169,42 +171,6 @@ mkNewTyConRhs tycon_name tycon con eta_reduce tvs ty = (reverse tvs, ty) -mkNewTyConRep :: TyCon -- The original type constructor - -> Type -- The arg type of its constructor - -> Type -- Chosen representation type --- The "representation type" is guaranteed not to be another newtype --- at the outermost level; but it might have newtypes in type arguments - --- Find the representation type for this newtype TyCon --- Remember that the representation type is the *ultimate* representation --- type, looking through other newtypes. --- --- splitTyConApp_maybe no longer looks through newtypes, so we must --- deal explicitly with this case --- --- The trick is to to deal correctly with recursive newtypes --- such as newtype T = MkT T - -mkNewTyConRep tc rhs_ty - | null (tyConDataCons tc) = unitTy - -- External Core programs can have newtypes with no data constructors - | otherwise = go [tc] rhs_ty - where - -- Invariant: tcs have been seen before - go tcs rep_ty - = case splitTyConApp_maybe rep_ty of - Just (tc, tys) - | tc `elem` tcs -> unitTy -- Recursive loop - | isNewTyCon tc -> - if isRecursiveTyCon tc then - go (tc:tcs) (substTyWith tvs tys rhs_ty) - else - substTyWith tvs tys rhs_ty - where - (tvs, rhs_ty) = newTyConRhs tc - - other -> rep_ty - ------------------------------------------------------ buildDataCon :: Name -> Bool -> [StrictnessMark] @@ -236,13 +202,14 @@ buildDataCon src_name declared_infix arg_stricts field_lbls stupid_ctxt dc_ids dc_ids = mkDataConIds wrap_name work_name data_con - ; returnM data_con } + ; return data_con } -- The stupid context for a data constructor should be limited to -- the type variables mentioned in the arg_tys -- ToDo: Or functionally dependent on? -- This whole stupid theta thing is, well, stupid. +mkDataConStupidTheta :: TyCon -> [Type] -> [TyVar] -> [PredType] mkDataConStupidTheta tycon arg_tys univ_tvs | null stupid_theta = [] -- The common case | otherwise = filter in_arg_tys stupid_theta @@ -268,52 +235,68 @@ mkTyConSelIds tycon rhs ------------------------------------------------------ \begin{code} -buildClass :: Name -> [TyVar] -> ThetaType +buildClass :: Bool -- True <=> do not include unfoldings + -- on dict selectors + -- Used when importing a class without -O + -> Name -> [TyVar] -> ThetaType -> [FunDep TyVar] -- Functional dependencies -> [TyThing] -- Associated types -> [(Name, DefMeth, Type)] -- Method info -> RecFlag -- Info for type constructor -> TcRnIf m n Class -buildClass class_name tvs sc_theta fds ats sig_stuff tc_isrec - = do { tycon_name <- newImplicitBinder class_name mkClassTyConOcc +buildClass no_unf class_name tvs sc_theta fds ats sig_stuff tc_isrec + = do { traceIf (text "buildClass") + ; tycon_name <- newImplicitBinder class_name mkClassTyConOcc ; datacon_name <- newImplicitBinder class_name mkClassDataConOcc -- The class name is the 'parent' for this datacon, not its tycon, -- because one should import the class to get the binding for -- the datacon - ; sc_sel_names <- mapM (newImplicitBinder class_name . mkSuperDictSelOcc) - [1..length sc_theta] - -- We number off the superclass selectors, 1, 2, 3 etc so that we - -- can construct names for the selectors. Thus - -- class (C a, C b) => D a b where ... - -- gives superclass selectors - -- D_sc1, D_sc2 - -- (We used to call them D_C, but now we can have two different - -- superclasses both called C!) ; fixM (\ rec_clas -> do { -- Only name generation inside loop - let { rec_tycon = classTyCon rec_clas - ; op_tys = [ty | (_,_,ty) <- sig_stuff] - ; sc_tys = mkPredTys sc_theta - ; dict_component_tys = sc_tys ++ op_tys - ; sc_sel_ids = [mkDictSelId sc_name rec_clas | sc_name <- sc_sel_names] - ; op_items = [ (mkDictSelId op_name rec_clas, dm_info) - | (op_name, dm_info, _) <- sig_stuff ] } + let { rec_tycon = classTyCon rec_clas + ; op_tys = [ty | (_,_,ty) <- sig_stuff] + ; op_items = [ (mkDictSelId no_unf op_name rec_clas, dm_info) + | (op_name, dm_info, _) <- sig_stuff ] } -- Build the selector id and default method id ; dict_con <- buildDataCon datacon_name False -- Not declared infix - (map (const NotMarkedStrict) dict_component_tys) + (map (const NotMarkedStrict) op_tys) [{- No labelled fields -}] tvs [{- no existentials -}] - [{- No equalities -}] [{-No context-}] - dict_component_tys + [{- No GADT equalities -}] sc_theta + op_tys rec_tycon - ; rhs <- case dict_component_tys of - [rep_ty] -> mkNewTyConRhs tycon_name rec_tycon dict_con - other -> return (mkDataTyConRhs [dict_con]) + ; let n_value_preds = count (not . isEqPred) sc_theta + all_value_preds = n_value_preds == length sc_theta + -- We only make selectors for the *value* superclasses, + -- not equality predicates + + ; sc_sel_names <- mapM (newImplicitBinder class_name . mkSuperDictSelOcc) + [1..n_value_preds] + ; let sc_sel_ids = [mkDictSelId no_unf sc_name rec_clas | sc_name <- sc_sel_names] + -- We number off the Dict superclass selectors, 1, 2, 3 etc so that we + -- can construct names for the selectors. Thus + -- class (C a, C b) => D a b where ... + -- gives superclass selectors + -- D_sc1, D_sc2 + -- (We used to call them D_C, but now we can have two different + -- superclasses both called C!) + -- + + ; let use_newtype = (n_value_preds + length sig_stuff == 1) && all_value_preds + -- Use a newtype if the data constructor has + -- (a) exactly one value field + -- (b) no existential or equality-predicate fields + -- i.e. exactly one operation or superclass taken together + -- See note [Class newtypes and equality predicates] + + ; rhs <- if use_newtype + then mkNewTyConRhs tycon_name rec_tycon dict_con + else return (mkDataTyConRhs [dict_con]) ; let { clas_kind = mkArrowKinds (map tyVarKind tvs) liftedTypeKind @@ -328,11 +311,29 @@ buildClass class_name tvs sc_theta fds ats sig_stuff tc_isrec -- newtype like a synonym, but that will lead to an infinite -- type] ; atTyCons = [tycon | ATyCon tycon <- ats] + + ; result = mkClass class_name tvs fds + sc_theta sc_sel_ids atTyCons + op_items tycon } - ; return (mkClass class_name tvs fds - sc_theta sc_sel_ids atTyCons op_items - tycon) + ; traceIf (text "buildClass" <+> ppr tycon) + ; return result })} \end{code} +Note [Class newtypes and equality predicates] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Consider + class (a ~ F b) => C a b where + op :: a -> b + +We cannot represent this by a newtype, even though it's not +existential, and there's only one value field, because we do +capture an equality predicate: + + data C a b where + MkC :: forall a b. (a ~ F b) => (a->b) -> C a b + +We need to access this equality predicate when we get passes a C +dictionary. See Trac #2238