X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Fiface%2FBuildTyCl.lhs;h=8459edf98ad5ec54933f884af52260d3f8fb7dfd;hb=a08b4f85df5fbebc237bb7798cabe3812500e921;hp=e951c633d83257505052e34f2b04979af381adba;hpb=17b297d97d327620ed6bfab942f8992b2446f1bf;p=ghc-hetmet.git diff --git a/compiler/iface/BuildTyCl.lhs b/compiler/iface/BuildTyCl.lhs index e951c63..8459edf 100644 --- a/compiler/iface/BuildTyCl.lhs +++ b/compiler/iface/BuildTyCl.lhs @@ -4,13 +4,6 @@ % \begin{code} -{-# OPTIONS_GHC -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/WorkingConventions#Warnings --- for details - module BuildTyCl ( buildSynTyCon, buildAlgTyCon, buildDataCon, buildClass, @@ -21,12 +14,10 @@ module BuildTyCl ( #include "HsVersions.h" import IfaceEnv -import TcRnMonad import DataCon import Var import VarSet -import TysWiredIn import BasicTypes import Name import OccName @@ -37,6 +28,7 @@ import Type import Coercion import TcRnMonad +import Util ( count ) import Outputable import Data.List @@ -146,10 +138,9 @@ mkNewTyConRhs tycon_name tycon con ; 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 @@ -180,42 +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] @@ -247,13 +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 @@ -279,14 +235,17 @@ 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 +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 @@ -298,7 +257,7 @@ buildClass class_name tvs sc_theta fds ats sig_stuff tc_isrec let { rec_tycon = classTyCon rec_clas ; op_tys = [ty | (_,_,ty) <- sig_stuff] - ; op_items = [ (mkDictSelId op_name rec_clas, dm_info) + ; 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 @@ -311,22 +270,31 @@ buildClass class_name tvs sc_theta fds ats sig_stuff tc_isrec op_tys rec_tycon - ; sc_sel_names <- mapM (newImplicitBinder class_name . mkSuperDictSelOcc) - [1..length (dataConDictTheta 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 + -- 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 sc_sel_ids = [mkDictSelId sc_name rec_clas | sc_name <- sc_sel_names] - - -- Use a newtype if the class constructor has exactly one field: + -- + + ; 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 - -- Watch out: the sc_theta includes equality predicates, - -- which don't count for this purpose; hence dataConDictTheta - ; rhs <- if ((length $ dataConDictTheta dict_con) + length sig_stuff) == 1 + -- See note [Class newtypes and equality predicates] + + ; rhs <- if use_newtype then mkNewTyConRhs tycon_name rec_tycon dict_con else return (mkDataTyConRhs [dict_con]) @@ -353,4 +321,19 @@ buildClass class_name tvs sc_theta fds ats sig_stuff tc_isrec })} \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