X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypes%2FTypeRep.lhs;h=45cd457baa2c6b488ea174c5b454f4d21e245e47;hb=8e67f5502e2e316245806ee3735a2f41a844b611;hp=b5e04a1299672074d0880b94173cb01803e07bbb;hpb=266fadd93461d4317967df08cd641e965cd8769a;p=ghc-hetmet.git diff --git a/ghc/compiler/types/TypeRep.lhs b/ghc/compiler/types/TypeRep.lhs index b5e04a1..45cd457 100644 --- a/ghc/compiler/types/TypeRep.lhs +++ b/ghc/compiler/types/TypeRep.lhs @@ -5,42 +5,42 @@ \begin{code} module TypeRep ( - Type(..), TyNote(..), UsageAnn(..), -- Representation visible to friends - Kind, TyVarSubst, + TyThing(..), + Type(..), TyNote(..), -- Representation visible + PredType(..), -- to friends + + Kind, ThetaType, -- Synonyms - superKind, superBoxity, -- :: SuperKind + funTyCon, - boxedKind, -- :: Kind :: BX - anyBoxKind, -- :: Kind :: BX - typeCon, -- :: KindCon :: BX -> KX - anyBoxCon, -- :: KindCon :: BX - - boxedTypeKind, unboxedTypeKind, openTypeKind, -- Kind :: superKind + -- Pretty-printing + pprType, pprParendType, pprTyThingCategory, + pprPred, pprTheta, pprThetaArrow, pprClassPred, + -- Re-export fromKind + liftedTypeKind, unliftedTypeKind, openTypeKind, + isLiftedTypeKind, isUnliftedTypeKind, isOpenTypeKind, mkArrowKind, mkArrowKinds, - - funTyCon + pprKind, pprParendKind ) where #include "HsVersions.h" --- friends: -import Var ( TyVar, UVar ) -import VarEnv -import VarSet +import {-# SOURCE #-} DataCon( DataCon, dataConName ) -import Name ( Name, Provenance(..), ExportFlag(..), - mkWiredInTyConName, mkGlobalName, mkKindOccFS, tcName, - ) -import TyCon ( TyCon, KindCon, - mkFunTyCon, mkKindCon, mkSuperKindCon, - ) +-- friends: +import Kind +import Var ( Var, Id, TyVar, tyVarKind ) +import VarSet ( TyVarSet ) +import Name ( Name, NamedThing(..), BuiltInSyntax(..), mkWiredInName ) +import OccName ( mkOccFS, tcName, parenSymOcc ) +import BasicTypes ( IPName, tupleParens ) +import TyCon ( TyCon, mkFunTyCon, tyConArity, tupleTyConBoxity, isTupleTyCon, isRecursiveTyCon, isNewTyCon ) +import Class ( Class ) -- others -import SrcLoc ( mkBuiltinSrcLoc ) -import PrelMods ( pREL_GHC ) -import Unique -- quite a few *Keys -import Util ( thenCmp ) +import PrelNames ( gHC_PRIM, funTyConKey, listTyConKey, parrTyConKey, hasKey ) +import Outputable \end{code} %************************************************************************ @@ -52,15 +52,15 @@ import Util ( thenCmp ) A type is *unboxed* iff its representation is other than a pointer - Unboxed types cannot instantiate a type variable. - Unboxed types are always unlifted. + Unboxed types are also unlifted. *lifted* A type is lifted iff it has bottom as an element. Closures always have lifted types: i.e. any let-bound identifier in Core must have a lifted type. Operationally, a lifted object is one that can be entered. - (NOTE: previously "pointed"). + + Only lifted types may be unified with a type variable. *algebraic* A type with one or more constructors, whether declared with "data" or "newtype". @@ -91,6 +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} @@ -99,137 +144,116 @@ 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 - - | TyConApp -- Application of a TyCon - TyCon -- *Invariant* saturated appliations of FunTyCon and - -- synonyms have their own constructors, below. + Type -- It must be another AppTy, or TyVarTy + -- (or NoteTy of these) + + | TyConApp -- Application of a TyCon, including newtypes + TyCon -- *Invariant* saturated appliations of FunTyCon and + -- synonyms have their own constructors, below. + -- However, *unsaturated* type synonyms, and FunTyCons + -- do appear as TyConApps. (Unsaturated type synonyms + -- can appear as the RHS of a type synonym, for exmaple.) [Type] -- Might not be saturated. - | FunTy -- Special case of TyConApp: TyConApp FunTyCon [t1,t2] + | FunTy -- Special case of TyConApp: TyConApp FunTyCon [t1,t2] Type Type - | NoteTy -- Saturated application of a type synonym - TyNote - Type -- The expanded version - - | ForAllTy + | ForAllTy -- A polymorphic type TyVar - Type -- TypeKind + Type -data TyNote - = SynNote Type -- The unexpanded version of the type synonym; always a TyConApp - | FTVNote TyVarSet -- The free type variables of the noted expression - | UsgNote UsageAnn -- The usage annotation at this node - | UsgForAll UVar -- Annotation variable binder - | IPNote Name -- It's an implicit parameter - -data UsageAnn - = UsOnce -- Used at most once - | UsMany -- Used possibly many times (no info; this annotation can be omitted) - | UsVar UVar -- Annotation is variable (unbound OK only inside analysis) -\end{code} - - -%************************************************************************ -%* * -\subsection{Kinds} -%* * -%************************************************************************ + | PredTy -- A high level source type + PredType -- ...can be expanded to a representation type... -Kinds -~~~~~ -k::K = Type bx - | k -> k - | kv + | NoteTy -- A type with a note attached + TyNote + Type -- The expanded version -kv :: KX is a kind variable +data TyNote + = FTVNote TyVarSet -- The free type variables of the noted expression -Type :: BX -> KX + | SynNote Type -- Used for type synonyms + -- The Type is always a TyConApp, and is the un-expanded form. + -- The type to which the note is attached is the expanded form. +\end{code} -bx::BX = Boxed - | Unboxed - | AnyBox -- Used *only* for special built-in things - -- like error :: forall (a::*?). String -> a - -- Here, the 'a' can be instantiated to a boxed or - -- unboxed type. - | bv +------------------------------------- + Source types -bxv :: BX is a boxity variable +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: -sk = KX -- A kind - | BX -- A boxity - | sk -> sk -- In ptic (BX -> KX) + * The type checker must treat it as opaque + * The rest of the compiler treats it as transparent -\begin{code} -mk_kind_name key str = mkGlobalName key pREL_GHC (mkKindOccFS tcName str) - (LocalDef mkBuiltinSrcLoc NotExported) - -- mk_kind_name is a bit of a hack - -- The LocalDef means that we print the name without - -- a qualifier, which is what we want for these kinds. - -- It's used for both Kinds and Boxities -\end{code} +Consider these examples: + f :: (Eq a) => a -> Int + g :: (?x :: Int -> Int) => a -> Int + h :: (r\l) => {r} => {l::Int | r} -Define KX, BX. +Here the "Eq a" and "?x :: Int -> Int" and "r\l" are all called *predicates* +Predicates are represented inside GHC by PredType: \begin{code} -superKind :: SuperKind -- KX, the type of all kinds -superKindName = mk_kind_name kindConKey SLIT("KX") -superKind = TyConApp (mkSuperKindCon superKindName) [] +data PredType + = ClassP Class [Type] -- Class predicate + | IParam (IPName Name) Type -- Implicit parameter -superBoxity :: SuperKind -- BX, the type of all boxities -superBoxityName = mk_kind_name boxityConKey SLIT("BX") -superBoxity = TyConApp (mkSuperKindCon superBoxityName) [] +type ThetaType = [PredType] \end{code} -Define Boxed, Unboxed, AnyBox - -\begin{code} -boxedKind, unboxedKind, anyBoxKind :: Kind -- Of superkind superBoxity +(We don't support TREX records yet, but the setup is designed +to expand to allow them.) -boxedConName = mk_kind_name boxedConKey SLIT("*") -boxedKind = TyConApp (mkKindCon boxedConName superBoxity) [] +A Haskell qualified type, such as that for f,g,h above, is +represented using + * a FunTy for the double arrow + * with a PredTy as the function argument -unboxedConName = mk_kind_name unboxedConKey SLIT("#") -unboxedKind = TyConApp (mkKindCon unboxedConName superBoxity) [] +The predicate really does turn into a real extra argument to the +function. If the argument has type (PredTy p) then the predicate p is +represented by evidence (a dictionary, for example, of type (predRepTy p). -anyBoxConName = mk_kind_name anyBoxConKey SLIT("?") -anyBoxCon = mkKindCon anyBoxConName superBoxity -- A kind of wild card -anyBoxKind = TyConApp anyBoxCon [] -\end{code} -Define Type - -\begin{code} -typeCon :: KindCon -typeConName = mk_kind_name typeConKey SLIT("Type") -typeCon = mkKindCon typeConName (superBoxity `FunTy` superKind) -\end{code} +%************************************************************************ +%* * + TyThing +%* * +%************************************************************************ -Define (Type Boxed), (Type Unboxed), (Type AnyBox) +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} -boxedTypeKind, unboxedTypeKind, openTypeKind :: Kind -boxedTypeKind = TyConApp typeCon [boxedKind] -unboxedTypeKind = TyConApp typeCon [unboxedKind] -openTypeKind = TyConApp typeCon [anyBoxKind] - -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} @@ -242,66 +266,149 @@ 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} -funTyConName = mkWiredInTyConName funTyConKey pREL_GHC SLIT("(->)") funTyCon -funTyCon = mkFunTyCon funTyConName (mkArrowKinds [boxedTypeKind, boxedTypeKind] boxedTypeKind) +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 + (mkOccFS tcName FSLIT("(->)")) + funTyConKey + Nothing -- No parent object + (ATyCon funTyCon) -- Relevant TyCon + BuiltInSyntax \end{code} %************************************************************************ %* * -\subsection{Equality on types} +\subsection{The external interface} %* * %************************************************************************ -For the moment at least, type comparisons don't work if -there are embedded for-alls. +@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} -instance Eq Type where - ty1 == ty2 = case ty1 `cmpTy` ty2 of { EQ -> True; other -> False } +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 Ord Type where - compare ty1 ty2 = cmpTy ty1 ty2 +instance Outputable name => OutputableBndr (IPName name) where + pprBndr _ n = ppr n -- Simple for now -cmpTy :: Type -> Type -> Ordering -cmpTy ty1 ty2 - = cmp emptyVarEnv ty1 ty2 +------------------ + -- 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 (SynNote ty1) ty2) = ppr_type p ty1 +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 (FTVNote _) ty) = split1 tvs ty + split1 tvs ty = (reverse tvs, ty) + + split2 ps (NoteTy (FTVNote _) 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 (FTVNote _) 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 - -- The "env" maps type variables in ty1 to type variables in ty2 - -- So when comparing for-alls.. (forall tv1 . t1) (forall tv2 . t2) - -- we in effect substitute tv2 for tv1 in t1 before continuing - lookup env tv1 = case lookupVarEnv env tv1 of - Just tv2 -> tv2 - Nothing -> tv1 - - -- Get rid of NoteTy - cmp env (NoteTy _ ty1) ty2 = cmp env ty1 ty2 - cmp env ty1 (NoteTy _ ty2) = cmp env ty1 ty2 - - -- Deal with equal constructors - cmp env (TyVarTy tv1) (TyVarTy tv2) = lookup env tv1 `compare` tv2 - cmp env (AppTy f1 a1) (AppTy f2 a2) = cmp env f1 f2 `thenCmp` cmp env a1 a2 - cmp env (FunTy f1 a1) (FunTy f2 a2) = cmp env f1 f2 `thenCmp` cmp env a1 a2 - cmp env (TyConApp tc1 tys1) (TyConApp tc2 tys2) = (tc1 `compare` tc2) `thenCmp` (cmps env tys1 tys2) - cmp env (ForAllTy tv1 t1) (ForAllTy tv2 t2) = cmp (extendVarEnv env tv1 tv2) t1 t2 - - -- Deal with the rest: TyVarTy < AppTy < FunTy < TyConApp < ForAllTy - cmp env (AppTy _ _) (TyVarTy _) = GT - - cmp env (FunTy _ _) (TyVarTy _) = GT - cmp env (FunTy _ _) (AppTy _ _) = GT - - cmp env (TyConApp _ _) (TyVarTy _) = GT - cmp env (TyConApp _ _) (AppTy _ _) = GT - cmp env (TyConApp _ _) (FunTy _ _) = GT - - cmp env (ForAllTy _ _) other = GT - - cmp env _ _ = LT - - cmps env [] [] = EQ - cmps env (t:ts) [] = GT - cmps env [] (t:ts) = LT - cmps env (t1:t1s) (t2:t2s) = cmp env t1 t2 `thenCmp` cmps env t1s t2s + 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}