X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypes%2FTypeRep.lhs;h=7bb863a210e37841c77a8b7be7a6dac00985a439;hb=28a464a75e14cece5db40f2765a29348273ff2d2;hp=d48bcaca928ebea728b351df8eae9628be02e5f9;hpb=788faebb40b51d37e73ed94dfc99460d39a1a811;p=ghc-hetmet.git diff --git a/ghc/compiler/types/TypeRep.lhs b/ghc/compiler/types/TypeRep.lhs index d48bcac..7bb863a 100644 --- a/ghc/compiler/types/TypeRep.lhs +++ b/ghc/compiler/types/TypeRep.lhs @@ -5,43 +5,42 @@ \begin{code} module TypeRep ( - Type(..), TyNote(..), PredType(..), -- Representation visible to friends + TyThing(..), + Type(..), TyNote(..), -- Representation visible + PredType(..), -- to friends - Kind, ThetaType, RhoType, TauType, SigmaType, -- Synonyms - TyVarSubst, - - superKind, superBoxity, -- KX and BX respectively - liftedBoxity, unliftedBoxity, -- :: BX - openKindCon, -- :: KX - typeCon, -- :: BX -> KX - liftedTypeKind, unliftedTypeKind, openTypeKind, -- :: KX - mkArrowKind, mkArrowKinds, -- :: KX -> KX -> KX - - usageKindCon, -- :: KX - usageTypeKind, -- :: KX - usOnceTyCon, usManyTyCon, -- :: $ - usOnce, usMany, -- :: $ - - funTyCon + Kind, ThetaType, -- Synonyms + + funTyCon, + + -- Pretty-printing + pprType, pprParendType, pprTyThingCategory, + pprPred, pprTheta, pprThetaArrow, pprClassPred, + + -- Re-export fromKind + liftedTypeKind, unliftedTypeKind, openTypeKind, + isLiftedTypeKind, isUnliftedTypeKind, isOpenTypeKind, + mkArrowKind, mkArrowKinds, + pprKind, pprParendKind ) where #include "HsVersions.h" --- friends: -import Var ( TyVar ) -import VarEnv -import VarSet +import {-# SOURCE #-} DataCon( DataCon, dataConName ) -import Name ( Name ) -import TyCon ( TyCon, KindCon, mkFunTyCon, mkKindCon, mkSuperKindCon ) -import Class ( Class ) +-- friends: +import Kind +import Var ( Var, Id, TyVar, tyVarKind ) +import VarSet ( TyVarSet ) +import Name ( Name, NamedThing(..), BuiltInSyntax(..), mkWiredInName ) +import OccName ( mkOccNameFS, tcName, parenSymOcc ) +import BasicTypes ( IPName, tupleParens ) +import TyCon ( TyCon, mkFunTyCon, tyConArity, tupleTyConBoxity, isTupleTyCon, isRecursiveTyCon, isNewTyCon ) +import Class ( Class ) -- others -import PrelNames ( superKindName, superBoxityName, liftedConName, - unliftedConName, typeConName, openKindConName, - usageKindConName, usOnceTyConName, usManyTyConName, - funTyConName - ) +import PrelNames ( gHC_PRIM, funTyConKey, listTyConKey, parrTyConKey, hasKey ) +import Outputable \end{code} %************************************************************************ @@ -92,6 +91,51 @@ ByteArray# Yes Yes No No ( a, b ) No Yes Yes Yes [a] No Yes Yes Yes + + + ---------------------- + A note about newtypes + ---------------------- + +Consider + newtype N = MkN Int + +Then we want N to be represented as an Int, and that's what we arrange. +The front end of the compiler [TcType.lhs] treats N as opaque, +the back end treats it as transparent [Type.lhs]. + +There's a bit of a problem with recursive newtypes + newtype P = MkP P + newtype Q = MkQ (Q->Q) + +Here the 'implicit expansion' we get from treating P and Q as transparent +would give rise to infinite types, which in turn makes eqType diverge. +Similarly splitForAllTys and splitFunTys can get into a loop. + +Solution: + +* Newtypes are always represented using TyConApp. + +* For non-recursive newtypes, P, treat P just like a type synonym after + type-checking is done; i.e. it's opaque during type checking (functions + from TcType) but transparent afterwards (functions from Type). + "Treat P as a type synonym" means "all functions expand NewTcApps + on the fly". + + Applications of the data constructor P simply vanish: + P x = x + + +* For recursive newtypes Q, treat the Q and its representation as + distinct right through the compiler. Applications of the data consructor + use a coerce: + Q = \(x::Q->Q). coerce Q x + They are rare, so who cares if they are a tiny bit less efficient. + +The typechecker (TcTyDecls) identifies enough type construtors as 'recursive' +to cut all loops. The other members of the loop may be marked 'non-recursive'. + + %************************************************************************ %* * \subsection{The data type} @@ -100,22 +144,23 @@ ByteArray# Yes Yes No No \begin{code} -type SuperKind = Type -type Kind = Type - -type TyVarSubst = TyVarEnv Type - data Type - = TyVarTy TyVar + = TyVarTy TyVar | AppTy Type -- Function is *not* a TyConApp - Type + Type -- It must be another AppTy, or TyVarTy + -- (or NoteTy of these) - | TyConApp -- Application of a TyCon - TyCon -- *Invariant* saturated appliations of FunTyCon and + | TyConApp -- Application of a TyCon, including newtypes *and* synonyms + TyCon -- *Invariant* saturated appliations of FunTyCon and -- synonyms have their own constructors, below. + -- However, *unsaturated* FunTyCons do appear as TyConApps. + -- [Type] -- Might not be saturated. + -- Even type synonyms are not necessarily saturated; + -- for example unsaturated type synonyms can appear as the + -- RHS of a type synonym. | FunTy -- Special case of TyConApp: TyConApp FunTyCon [t1,t2] Type @@ -125,34 +170,27 @@ data Type TyVar Type - | PredTy -- A Haskell predicate - PredType - - | UsageTy -- A usage-annotated type - Type -- - Annotation of kind $ (i.e., usage annotation) - Type -- - Annotated type + | PredTy -- A high level source type + PredType -- ...can be expanded to a representation type... | NoteTy -- A type with a note attached TyNote Type -- The expanded version -data TyNote - = SynNote Type -- The unexpanded version of the type synonym; always a TyConApp - | FTVNote TyVarSet -- The free type variables of the noted expression - -type ThetaType = [PredType] -type RhoType = Type -type TauType = Type -type SigmaType = Type +data TyNote = FTVNote TyVarSet -- The free type variables of the noted expression \end{code} -INVARIANT: UsageTys are optional, but may *only* appear immediately -under a FunTy (either argument), or at top-level of a Type permitted -to be annotated (such as the type of an Id). NoteTys are transparent -for the purposes of this rule. - ------------------------------------- - Predicates + Source types + +A type of the form + PredTy p +represents a value whose type is the Haskell predicate p, +where a predicate is what occurs before the '=>' in a Haskell type. +It can be expanded into its representation, but: + + * The type checker must treat it as opaque + * The rest of the compiler treats it as transparent Consider these examples: f :: (Eq a) => a -> Int @@ -163,8 +201,11 @@ Here the "Eq a" and "?x :: Int -> Int" and "r\l" are all called *predicates* Predicates are represented inside GHC by PredType: \begin{code} -data PredType = ClassP Class [Type] - | IParam Name Type +data PredType + = ClassP Class [Type] -- Class predicate + | IParam (IPName Name) Type -- Implicit parameter + +type ThetaType = [PredType] \end{code} (We don't support TREX records yet, but the setup is designed @@ -182,102 +223,34 @@ represented by evidence (a dictionary, for example, of type (predRepTy p). %************************************************************************ %* * -\subsection{Kinds} + TyThing %* * %************************************************************************ -Kinds -~~~~~ -kind :: KX = kind -> kind - - | Type liftedness -- (Type *) is printed as just * - -- (Type #) is printed as just # - - | UsageKind -- Printed '$'; used for usage annotations - - | OpenKind -- Can be lifted or unlifted - -- Printed '?' - - | kv -- A kind variable; *only* happens during kind checking - -boxity :: BX = * -- Lifted - | # -- Unlifted - | bv -- A boxity variable; *only* happens during kind checking - -There's a little subtyping at the kind level: - forall b. Type b <: OpenKind - -That is, a type of kind (Type b) is OK in a context requiring an OpenKind - -OpenKind, written '?', is used as the kind for certain type variables, -in two situations: - -1. The universally quantified type variable(s) for special built-in - things like error :: forall (a::?). String -> a. - Here, the 'a' can be instantiated to a lifted or unlifted type. - -2. Kind '?' is also used when the typechecker needs to create a fresh - type variable, one that may very well later be unified with a type. - For example, suppose f::a, and we see an application (f x). Then a - must be a function type, so we unify a with (b->c). But what kind - are b and c? They can be lifted or unlifted types, so we give them - kind '?'. - - When the type checker generalises over a bunch of type variables, it - makes any that still have kind '?' into kind '*'. So kind '?' is never - present in an inferred type. - - ------------------------------------------- -Define KX, the type of a kind - BX, the type of a boxity +Despite the fact that DataCon has to be imported via a hi-boot route, +this module seems the right place for TyThing, because it's needed for +funTyCon and all the types in TysPrim. \begin{code} -superKind :: SuperKind -- KX, the type of all kinds -superKind = TyConApp (mkSuperKindCon superKindName) [] - -superBoxity :: SuperKind -- BX, the type of all boxities -superBoxity = TyConApp (mkSuperKindCon superBoxityName) [] -\end{code} - ------------------------------------------- -Define boxities: @*@ and @#@ - -\begin{code} -liftedBoxity, unliftedBoxity :: Kind -- :: BX -liftedBoxity = TyConApp (mkKindCon liftedConName superBoxity) [] - -unliftedBoxity = TyConApp (mkKindCon unliftedConName superBoxity) [] -\end{code} - ------------------------------------------- -Define kinds: Type, Type *, Type #, OpenKind, and UsageKind - -\begin{code} -typeCon :: KindCon -- :: BX -> KX -typeCon = mkKindCon typeConName (superBoxity `FunTy` superKind) - -liftedTypeKind, unliftedTypeKind, openTypeKind :: Kind -- Of superkind superKind - -liftedTypeKind = TyConApp typeCon [liftedBoxity] -unliftedTypeKind = TyConApp typeCon [unliftedBoxity] - -openKindCon = mkKindCon openKindConName superKind -openTypeKind = TyConApp openKindCon [] - -usageKindCon = mkKindCon usageKindConName superKind -usageTypeKind = TyConApp usageKindCon [] -\end{code} - ------------------------------------------- -Define arrow kinds - -\begin{code} -mkArrowKind :: Kind -> Kind -> Kind -mkArrowKind k1 k2 = k1 `FunTy` k2 - -mkArrowKinds :: [Kind] -> Kind -> Kind -mkArrowKinds arg_kinds result_kind = foldr mkArrowKind result_kind arg_kinds +data TyThing = AnId Id + | ADataCon DataCon + | ATyCon TyCon + | AClass Class + +instance Outputable TyThing where + ppr thing = pprTyThingCategory thing <+> quotes (ppr (getName thing)) + +pprTyThingCategory :: TyThing -> SDoc +pprTyThingCategory (ATyCon _) = ptext SLIT("Type constructor") +pprTyThingCategory (AClass _) = ptext SLIT("Class") +pprTyThingCategory (AnId _) = ptext SLIT("Identifier") +pprTyThingCategory (ADataCon _) = ptext SLIT("Data constructor") + +instance NamedThing TyThing where -- Can't put this with the type + getName (AnId id) = getName id -- decl, because the DataCon instance + getName (ATyCon tc) = getName tc -- isn't visible there + getName (AClass cl) = getName cl + getName (ADataCon dc) = dataConName dc \end{code} @@ -290,20 +263,147 @@ mkArrowKinds arg_kinds result_kind = foldr mkArrowKind result_kind arg_kinds We define a few wired-in type constructors here to avoid module knots \begin{code} -funTyCon = mkFunTyCon funTyConName (mkArrowKinds [liftedTypeKind, liftedTypeKind] liftedTypeKind) +funTyCon = mkFunTyCon funTyConName (mkArrowKinds [argTypeKind, openTypeKind] liftedTypeKind) + -- You might think that (->) should have type (?? -> ? -> *), and you'd be right + -- But if we do that we get kind errors when saying + -- instance Control.Arrow (->) + -- becuase the expected kind is (*->*->*). The trouble is that the + -- expected/actual stuff in the unifier does not go contra-variant, whereas + -- the kind sub-typing does. Sigh. It really only matters if you use (->) in + -- a prefix way, thus: (->) Int# Int#. And this is unusual. + +funTyConName = mkWiredInName gHC_PRIM + (mkOccNameFS tcName FSLIT("(->)")) + funTyConKey + Nothing -- No parent object + (ATyCon funTyCon) -- Relevant TyCon + BuiltInSyntax \end{code} ------------------------------------------- -Usage tycons @.@ and @!@ -The usage tycons are of kind usageTypeKind (`$'). The types contain -no values, and are used purely for usage annotation. +%************************************************************************ +%* * +\subsection{The external interface} +%* * +%************************************************************************ + +@pprType@ is the standard @Type@ printer; the overloaded @ppr@ function is +defined to use this. @pprParendType@ is the same, except it puts +parens around the type, except for the atomic cases. @pprParendType@ +works just by setting the initial context precedence very high. \begin{code} -usOnceTyCon = mkKindCon usOnceTyConName usageTypeKind -usOnce = TyConApp usOnceTyCon [] - -usManyTyCon = mkKindCon usManyTyConName usageTypeKind -usMany = TyConApp usManyTyCon [] +data Prec = TopPrec -- No parens + | FunPrec -- Function args; no parens for tycon apps + | TyConPrec -- Tycon args; no parens for atomic + deriving( Eq, Ord ) + +maybeParen :: Prec -> Prec -> SDoc -> SDoc +maybeParen ctxt_prec inner_prec pretty + | ctxt_prec < inner_prec = pretty + | otherwise = parens pretty + +------------------ +pprType, pprParendType :: Type -> SDoc +pprType ty = ppr_type TopPrec ty +pprParendType ty = ppr_type TyConPrec ty + +------------------ +pprPred :: PredType -> SDoc +pprPred (ClassP cls tys) = pprClassPred cls tys +pprPred (IParam ip ty) = ppr ip <> dcolon <> pprType ty + +pprClassPred :: Class -> [Type] -> SDoc +pprClassPred clas tys = parenSymOcc (getOccName clas) (ppr clas) + <+> sep (map pprParendType tys) + +pprTheta :: ThetaType -> SDoc +pprTheta theta = parens (sep (punctuate comma (map pprPred theta))) + +pprThetaArrow :: ThetaType -> SDoc +pprThetaArrow theta + | null theta = empty + | otherwise = parens (sep (punctuate comma (map pprPred theta))) <+> ptext SLIT("=>") + +------------------ +instance Outputable Type where + ppr ty = pprType ty + +instance Outputable PredType where + ppr = pprPred + +instance Outputable name => OutputableBndr (IPName name) where + pprBndr _ n = ppr n -- Simple for now + +------------------ + -- OK, here's the main printer + +ppr_type :: Prec -> Type -> SDoc +ppr_type p (TyVarTy tv) = ppr tv +ppr_type p (PredTy pred) = braces (ppr pred) +ppr_type p (NoteTy other ty2) = ppr_type p ty2 +ppr_type p (TyConApp tc tys) = ppr_tc_app p tc tys + +ppr_type p (AppTy t1 t2) = maybeParen p TyConPrec $ + pprType t1 <+> ppr_type TyConPrec t2 + +ppr_type p ty@(ForAllTy _ _) = ppr_forall_type p ty +ppr_type p ty@(FunTy (PredTy _) _) = ppr_forall_type p ty + +ppr_type p (FunTy ty1 ty2) + = -- We don't want to lose synonyms, so we mustn't use splitFunTys here. + maybeParen p FunPrec $ + sep (ppr_type FunPrec ty1 : ppr_fun_tail ty2) + where + ppr_fun_tail (FunTy ty1 ty2) = (arrow <+> ppr_type FunPrec ty1) : ppr_fun_tail ty2 + ppr_fun_tail other_ty = [arrow <+> pprType other_ty] + +ppr_forall_type :: Prec -> Type -> SDoc +ppr_forall_type p ty + = maybeParen p FunPrec $ + sep [pprForAll tvs, pprThetaArrow ctxt, pprType tau] + where + (tvs, rho) = split1 [] ty + (ctxt, tau) = split2 [] rho + + split1 tvs (ForAllTy tv ty) = split1 (tv:tvs) ty + split1 tvs (NoteTy _ ty) = split1 tvs ty + split1 tvs ty = (reverse tvs, ty) + + split2 ps (NoteTy _ arg -- Rather a disgusting case + `FunTy` res) = split2 ps (arg `FunTy` res) + split2 ps (PredTy p `FunTy` ty) = split2 (p:ps) ty + split2 ps (NoteTy _ ty) = split2 ps ty + split2 ps ty = (reverse ps, ty) + +ppr_tc_app :: Prec -> TyCon -> [Type] -> SDoc +ppr_tc_app p tc [] + = ppr_tc tc +ppr_tc_app p tc [ty] + | tc `hasKey` listTyConKey = brackets (pprType ty) + | tc `hasKey` parrTyConKey = ptext SLIT("[:") <> pprType ty <> ptext SLIT(":]") +ppr_tc_app p tc tys + | isTupleTyCon tc && tyConArity tc == length tys + = tupleParens (tupleTyConBoxity tc) (sep (punctuate comma (map pprType tys))) + | otherwise + = maybeParen p TyConPrec $ + ppr_tc tc <+> sep (map (ppr_type TyConPrec) tys) + +ppr_tc :: TyCon -> SDoc +ppr_tc tc = parenSymOcc (getOccName tc) (pp_nt_debug <> ppr tc) + where + pp_nt_debug | isNewTyCon tc = ifPprDebug (if isRecursiveTyCon tc + then ptext SLIT("") + else ptext SLIT("")) + | otherwise = empty + +------------------- +pprForAll [] = empty +pprForAll tvs = ptext SLIT("forall") <+> sep (map pprTvBndr tvs) <> dot + +pprTvBndr tv | isLiftedTypeKind kind = ppr tv + | otherwise = parens (ppr tv <+> dcolon <+> pprKind kind) + where + kind = tyVarKind tv \end{code}