% % (c) The University of Glasgow 2006 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % \begin{code} module BuildTyCl ( buildSynTyCon, buildAlgTyCon, buildDataCon, TcMethInfo, buildClass, mkAbstractTyConRhs, mkNewTyConRhs, mkDataTyConRhs ) where #include "HsVersions.h" import IfaceEnv import DataCon import Var import VarSet import BasicTypes import Name import MkId import Class import TyCon import Type import Coercion import TcRnMonad import Data.List ( partition ) import Outputable \end{code} \begin{code} ------------------------------------------------------ buildSynTyCon :: Name -> [TyVar] -> SynTyConRhs -> Kind -- ^ Kind of the RHS -> TyConParent -> Maybe (TyCon, [Type]) -- ^ family instance if applicable -> TcRnIf m n TyCon buildSynTyCon tc_name tvs rhs rhs_kind parent mb_family | Just fam_inst_info <- mb_family = ASSERT( isNoParent parent ) fixM $ \ tycon_rec -> do { fam_parent <- mkFamInstParentInfo tc_name tvs fam_inst_info tycon_rec ; return (mkSynTyCon tc_name kind tvs rhs fam_parent) } | otherwise = return (mkSynTyCon tc_name kind tvs rhs parent) where kind = mkArrowKinds (map tyVarKind tvs) rhs_kind ------------------------------------------------------ buildAlgTyCon :: Name -> [TyVar] -> ThetaType -- ^ Stupid theta -> AlgTyConRhs -> RecFlag -> Bool -- ^ True <=> want generics functions -> Bool -- ^ True <=> was declared in GADT syntax -> TyConParent -> Maybe (TyCon, [Type]) -- ^ family instance if applicable -> TcRnIf m n TyCon buildAlgTyCon tc_name tvs stupid_theta rhs is_rec want_generics gadt_syn parent mb_family | Just fam_inst_info <- mb_family = -- We need to tie a knot as the coercion of a data instance depends -- on the instance representation tycon and vice versa. ASSERT( isNoParent parent ) fixM $ \ tycon_rec -> do { fam_parent <- mkFamInstParentInfo tc_name tvs fam_inst_info tycon_rec ; return (mkAlgTyCon tc_name kind tvs stupid_theta rhs fam_parent is_rec want_generics gadt_syn) } | otherwise = return (mkAlgTyCon tc_name kind tvs stupid_theta rhs parent is_rec want_generics gadt_syn) where kind = mkArrowKinds (map tyVarKind tvs) liftedTypeKind -- | If a family tycon with instance types is given, the current tycon is an -- instance of that family and we need to -- -- (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, -- `F' the family tycon and `R' the (derived) representation tycon, -- and -- (2) produce a `TyConParent' value containing the parent and coercion -- information. -- mkFamInstParentInfo :: Name -> [TyVar] -> (TyCon, [Type]) -> TyCon -> TcRnIf m n TyConParent mkFamInstParentInfo tc_name tvs (family, instTys) rep_tycon = do { -- Create the coercion ; co_tycon_name <- newImplicitBinder tc_name mkInstTyCoOcc ; let co_tycon = mkFamInstCoercion co_tycon_name tvs family instTys rep_tycon ; return $ FamInstTyCon family instTys co_tycon } ------------------------------------------------------ mkAbstractTyConRhs :: AlgTyConRhs mkAbstractTyConRhs = AbstractTyCon mkDataTyConRhs :: [DataCon] -> AlgTyConRhs mkDataTyConRhs cons = DataTyCon { data_cons = cons, is_enum = not (null cons) && all is_enum_con cons -- See Note [Enumeration types] in TyCon } where is_enum_con con | (_tvs, theta, arg_tys, _res) <- dataConSig con = null theta && null arg_tys mkNewTyConRhs :: Name -> TyCon -> DataCon -> TcRnIf m n AlgTyConRhs -- ^ Monadic because it makes a Name for the coercion TyCon -- We pass the Name of the parent TyCon, as well as the TyCon itself, -- because the latter is part of a knot, whereas the former is not. mkNewTyConRhs tycon_name tycon con = do { co_tycon_name <- newImplicitBinder tycon_name mkNewTyCoOcc ; let co_tycon = mkNewTypeCoercion co_tycon_name tycon etad_tvs etad_rhs cocon_maybe | all_coercions || isRecursiveTyCon tycon = 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 } ) } -- Coreview looks through newtypes with a Nothing -- for nt_co, or uses explicit coercions otherwise 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 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 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 -- See Note [Tricky iface loop] in LoadIface (etad_tvs, etad_rhs) = eta_reduce (reverse tvs) rhs_ty eta_reduce :: [TyVar] -- Reversed -> Type -- Rhs type -> ([TyVar], Type) -- Eta-reduced version (tyvars in normal order) eta_reduce (a:as) ty | Just (fun, arg) <- splitAppTy_maybe ty, Just tv <- getTyVar_maybe arg, tv == a, not (a `elemVarSet` tyVarsOfType fun) = eta_reduce as fun eta_reduce tvs ty = (reverse tvs, ty) ------------------------------------------------------ buildDataCon :: Name -> Bool -> [HsBang] -> [Name] -- Field labels -> [TyVar] -> [TyVar] -- Univ and ext -> [(TyVar,Type)] -- Equality spec -> ThetaType -- Does not include the "stupid theta" -- or the GADT equalities -> [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 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 -- code, which (for Haskell source anyway) will be in the DataName name -- space, and puts it into the VarName name space ; let 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 res_ty rep_tycon stupid_ctxt dc_ids dc_ids = mkDataConIds wrap_name work_name 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 where tc_subst = zipTopTvSubst (tyConTyVars tycon) (mkTyVarTys univ_tvs) stupid_theta = substTheta tc_subst (tyConStupidTheta tycon) -- Start by instantiating the master copy of the -- stupid theta, taken from the TyCon arg_tyvars = tyVarsOfTypes arg_tys in_arg_tys pred = not $ isEmptyVarSet $ tyVarsOfPred pred `intersectVarSet` arg_tyvars \end{code} ------------------------------------------------------ \begin{code} type TcMethInfo = (Name, DefMethSpec, Type) -- A temporary intermediate, to communicate -- between tcClassSigs and buildClass 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 -> [TcMethInfo] -- Method info -> RecFlag -- Info for type constructor -> TcRnIf m n Class 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 ; fixM (\ rec_clas -> do { -- Only name generation inside loop ; op_items <- mapM (mk_op_item rec_clas) sig_stuff -- Build the selector id and default method id ; let (eq_theta, dict_theta) = partition isEqPred sc_theta -- We only make selectors for the *value* superclasses, -- not equality predicates ; sc_sel_names <- mapM (newImplicitBinder class_name . mkSuperDictSelOcc) [1..length dict_theta] ; 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 = null eq_theta && (length dict_theta + length sig_stuff == 1) -- 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] -- We play a bit fast and loose by treating the dictionary -- superclasses as ordinary arguments. That means that in -- the case of -- class C a => D a -- we don't get a newtype with no arguments! args = sc_sel_names ++ op_names op_tys = [ty | (_,_,ty) <- sig_stuff] op_names = [op | (op,_,_) <- sig_stuff] arg_tys = map mkPredTy dict_theta ++ op_tys rec_tycon = classTyCon rec_clas ; dict_con <- buildDataCon datacon_name False -- Not declared infix (map (const HsNoBang) args) [{- No fields -}] tvs [{- no existentials -}] [{- No GADT equalities -}] eq_theta arg_tys (mkTyConApp rec_tycon (mkTyVarTys tvs)) rec_tycon ; 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 ; tycon = mkClassTyCon tycon_name clas_kind tvs rhs rec_clas tc_isrec -- A class can be recursive, and in the case of newtypes -- this matters. For example -- class C a where { op :: C b => a -> b -> Int } -- Because C has only one operation, it is represented by -- a newtype, and it should be a *recursive* newtype. -- [If we don't make it a recursive newtype, we'll expand the -- newtype like a synonym, but that will lead to an infinite -- type] ; atTyCons = [tycon | ATyCon tycon <- ats] ; result = mkClass class_name tvs fds (eq_theta ++ dict_theta) -- Equalities first (length eq_theta) -- Number of equalities sc_sel_ids atTyCons op_items tycon } ; traceIf (text "buildClass" <+> ppr tycon) ; return result })} where mk_op_item :: Class -> TcMethInfo -> TcRnIf n m ClassOpItem mk_op_item rec_clas (op_name, dm_spec, _) = do { dm_info <- case dm_spec of NoDM -> return NoDefMeth GenericDM -> return GenDefMeth VanillaDM -> do { dm_name <- newImplicitBinder op_name mkDefaultMethodOcc ; return (DefMeth dm_name) } ; return (mkDictSelId no_unf op_name rec_clas, dm_info) } \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