X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Fiface%2FBuildTyCl.lhs;h=6f56d4f4e14b8d09f63aa7180e9297402f9dd2b4;hb=960a5edb6ac87c7d85e36f4b70be8da0175819f7;hp=534bc5f4f1e2df7a22a090a692140a645d25bf50;hpb=219f900f4e518e8158807cdda6fdec8331f701f0;p=ghc-hetmet.git diff --git a/compiler/iface/BuildTyCl.lhs b/compiler/iface/BuildTyCl.lhs index 534bc5f..6f56d4f 100644 --- a/compiler/iface/BuildTyCl.lhs +++ b/compiler/iface/BuildTyCl.lhs @@ -4,13 +4,6 @@ % \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 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 @@ -47,22 +39,23 @@ import Data.List ------------------------------------------------------ buildSynTyCon :: Name -> [TyVar] -> SynTyConRhs + -> Kind -- Kind of the RHS -> Maybe (TyCon, [Type]) -- family instance if applicable -> TcRnIf m n TyCon -buildSynTyCon tc_name tvs rhs@(OpenSynTyCon rhs_ki _) _ +buildSynTyCon tc_name tvs rhs@(OpenSynTyCon {}) rhs_kind _ = let - kind = mkArrowKinds (map tyVarKind tvs) rhs_ki + kind = mkArrowKinds (map tyVarKind tvs) rhs_kind in return $ mkSynTyCon tc_name kind tvs rhs NoParentTyCon -buildSynTyCon tc_name tvs rhs@(SynonymTyCon rhs_ty) mb_family +buildSynTyCon tc_name tvs rhs@(SynonymTyCon {}) rhs_kind mb_family = do { -- We need to tie a knot as the coercion of a data instance depends -- on the instance representation tycon and vice versa. ; tycon <- fixM (\ tycon_rec -> do { parent <- mkParentInfo mb_family tc_name tvs tycon_rec ; let { tycon = mkSynTyCon tc_name kind tvs rhs parent - ; kind = mkArrowKinds (map tyVarKind tvs) (typeKind rhs_ty) + ; kind = mkArrowKinds (map tyVarKind tvs) rhs_kind } ; return tycon }) @@ -100,7 +93,7 @@ buildAlgTyCon tc_name tvs stupid_theta rhs is_rec want_generics gadt_syn -- -- (1) create a coercion that identifies the family instance type and the -- representation type from Step (1); ie, it is of the form --- `Co tvs :: F ts :=: R tvs', where `Co' is the name of the coercion, +-- `Co tvs :: F ts ~ R tvs', where `Co' is the name of the coercion, -- `F' the family tycon and `R' the (derived) representation tycon, -- and -- (2) produce a `TyConParent' value containing the parent and coercion @@ -155,13 +148,16 @@ mkNewTyConRhs tycon_name tycon con -- non-recursive newtypes all_coercions = True tvs = tyConTyVars tycon - rhs_ty = ASSERT(not (null (dataConInstOrigDictsAndArgTys con (mkTyVarTys tvs)))) - -- head (dataConInstOrigArgTys con (mkTyVarTys tvs)) - head (dataConInstOrigDictsAndArgTys con (mkTyVarTys tvs)) + inst_con_ty = applyTys (dataConUserType con) (mkTyVarTys tvs) + rhs_ty = ASSERT( isFunTy inst_con_ty ) funArgTy inst_con_ty -- 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 + -- NB: a newtype DataCon has a type that must look like + -- forall tvs. -> T tvs + -- Note that we *can't* use dataConInstOrigArgTys here because + -- the newtype arising from class Foo a => Bar a where {} + -- has a single argument (Foo a) that is a *type class*, so + -- dataConInstOrigArgTys returns []. etad_tvs :: [TyVar] -- Matched lazily, so that mkNewTypeCoercion can etad_rhs :: Type -- return a TyCon without pulling on rhs_ty @@ -187,14 +183,15 @@ buildDataCon :: Name -> Bool -> [(TyVar,Type)] -- Equality spec -> ThetaType -- Does not include the "stupid theta" -- or the GADT equalities - -> [Type] -> TyCon + -> [Type] -> Type -- Argument and result types + -> TyCon -- Rep tycon -> TcRnIf m n DataCon -- A wrapper for DataCon.mkDataCon that -- a) makes the worker Id -- b) makes the wrapper Id if necessary, including -- allocating its unique (hence monadic) buildDataCon src_name declared_infix arg_stricts field_lbls - univ_tvs ex_tvs eq_spec ctxt arg_tys tycon + univ_tvs ex_tvs eq_spec ctxt arg_tys res_ty rep_tycon = do { wrap_name <- newImplicitBinder src_name mkDataConWrapperOcc ; work_name <- newImplicitBinder src_name mkDataConWorkerOcc -- This last one takes the name of the data constructor in the source @@ -202,21 +199,22 @@ buildDataCon src_name declared_infix arg_stricts field_lbls -- space, and puts it into the VarName name space ; let - stupid_ctxt = mkDataConStupidTheta tycon arg_tys univ_tvs + stupid_ctxt = mkDataConStupidTheta rep_tycon arg_tys univ_tvs data_con = mkDataCon src_name declared_infix arg_stricts field_lbls univ_tvs ex_tvs eq_spec ctxt - arg_tys tycon + arg_tys res_ty rep_tycon 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 @@ -242,14 +240,17 @@ 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 @@ -261,7 +262,7 @@ 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 @@ -271,25 +272,35 @@ buildClass class_name tvs sc_theta fds ats sig_stuff tc_isrec [{- No labelled fields -}] tvs [{- no existentials -}] [{- No GADT equalities -}] sc_theta - op_tys + op_tys + (mkTyConApp rec_tycon (mkTyVarTys tvs)) 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]) @@ -316,4 +327,19 @@ 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