PredType(..), -- to friends
Kind, ThetaType, -- 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
-
- funTyCon
-#ifdef DEBUG
- , crudePprType
-#endif
+
+ 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"
-import {-# SOURCE #-} DataCon( DataCon )
+import {-# SOURCE #-} DataCon( DataCon, dataConName )
-- friends:
-import Var ( Id, TyVar, tyVarKind )
-import VarEnv ( TyVarEnv )
+import Kind
+import Var ( Var, Id, TyVar, tyVarKind )
import VarSet ( TyVarSet )
-import Name ( Name, mkWiredInName, mkInternalName )
-import OccName ( mkOccFS, mkKindOccFS, tcName )
-import BasicTypes ( IPName )
-import TyCon ( TyCon, KindCon, mkFunTyCon, mkKindCon, mkSuperKindCon, isNewTyCon )
+import Name ( Name, NamedThing(..), BuiltInSyntax(..), mkWiredInName )
+import OccName ( mkOccFS, tcName )
+import BasicTypes ( IPName, tupleParens )
+import TyCon ( TyCon, mkFunTyCon, tyConArity, tupleTyConBoxity, isTupleTyCon, isRecursiveTyCon, isNewTyCon )
import Class ( Class )
-- others
-import PrelNames ( gHC_PRIM, kindConKey, boxityConKey, liftedConKey,
- unliftedConKey, typeConKey, anyBoxConKey,
- funTyConKey
- )
-import SrcLoc ( noSrcLoc )
+import PrelNames ( gHC_PRIM, funTyConKey, listTyConKey, parrTyConKey, hasKey )
import Outputable
\end{code}
Solution:
-* Newtypes are always represented using NewTcApp, never as TyConApp.
+* 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
\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
+ | TyConApp -- Application of a TyCon, including newtypes
TyCon -- *Invariant* saturated appliations of FunTyCon and
-- synonyms have their own constructors, below.
- [Type] -- Might not be saturated.
-
- | NewTcApp -- Application of a NewType TyCon. All newtype applications
- TyCon -- show up like this until they are fed through newTypeRep,
- -- which returns
- -- * an ordinary TyConApp for non-saturated,
- -- or recursive newtypes
- --
- -- * the representation type of the newtype for satuarted,
- -- non-recursive ones
- -- [But the result of a call to newTypeRep is always consumed
- -- immediately; it never lives on in another type. So in any
- -- type, newtypes are always represented with NewTcApp.]
+ -- 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]
%************************************************************************
%* *
-\subsection{Kinds}
-%* *
-%************************************************************************
-
-Kinds
-~~~~~
-kind :: KX = kind -> kind
-
- | Type liftedness -- (Type *) is printed as just *
- -- (Type #) is printed as just #
-
- | 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, or indeed type schemes,
- 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
-
-\begin{code}
-superKindName = kindQual FSLIT("KX") kindConKey
-superBoxityName = kindQual FSLIT("BX") boxityConKey
-liftedConName = kindQual FSLIT("*") liftedConKey
-unliftedConName = kindQual FSLIT("#") unliftedConKey
-openKindConName = kindQual FSLIT("?") anyBoxConKey
-typeConName = kindQual FSLIT("Type") typeConKey
-
-kindQual str uq = mkInternalName uq (mkKindOccFS tcName str) noSrcLoc
- -- Kinds are not z-encoded in interface file, hence mkKindOccFS
- -- And they don't come from any particular module; indeed we always
- -- want to print them unqualified. Hence the InternalName.
-\end{code}
-
-\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 liftedBoxityCon []
-unliftedBoxity = TyConApp unliftedBoxityCon []
-
-liftedBoxityCon = mkKindCon liftedConName superBoxity
-unliftedBoxityCon = mkKindCon unliftedConName superBoxity
-\end{code}
-
-------------------------------------------
-Define kinds: Type, Type *, Type #, OpenKind
-
-\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 []
-\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
-\end{code}
-
-
-%************************************************************************
-%* *
TyThing
%* *
%************************************************************************
| 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}
We define a few wired-in type constructors here to avoid module knots
\begin{code}
-funTyCon = mkFunTyCon funTyConName (mkArrowKinds [liftedTypeKind, liftedTypeKind] liftedTypeKind)
- -- You might think that (->) should have type (? -> ? -> *), and you'd be right
+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
funTyConKey
Nothing -- No parent object
(ATyCon funTyCon) -- Relevant TyCon
+ BuiltInSyntax
\end{code}
-
%************************************************************************
%* *
- Crude printing
- For debug purposes, we may want to print a type directly
+\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}
-#ifdef DEBUG
-crudePprType :: Type -> SDoc
-crudePprType (TyVarTy tv) = ppr tv
-crudePprType (AppTy t1 t2) = crudePprType t1 <+> (parens (crudePprType t2))
-crudePprType (FunTy t1 t2) = crudePprType t1 <+> (parens (crudePprType t2))
-crudePprType (TyConApp tc tys) = ppr_tc_app (ppr tc <> pp_nt tc) tys
-crudePprType (NewTcApp tc tys) = ptext SLIT("<nt>") <+> ppr_tc_app (ppr tc <> pp_nt tc) tys
-crudePprType (ForAllTy tv ty) = sep [ptext SLIT("forall") <+>
- parens (ppr tv <+> crudePprType (tyVarKind tv)) <> dot,
- crudePprType ty]
-crudePprType (PredTy st) = braces (crudePprPredTy st)
-crudePprType (NoteTy (SynNote ty1) ty2) = crudePprType ty1
-crudePprType (NoteTy other ty) = crudePprType ty
-
-crudePprPredTy (ClassP cls tys) = ppr_tc_app (ppr cls) tys
-crudePprPredTy (IParam ip ty) = ppr ip <> dcolon <> crudePprType ty
-
-ppr_tc_app :: SDoc -> [Type] -> SDoc
-ppr_tc_app tc tys = tc <+> sep (map (parens . crudePprType) tys)
-
-pp_nt tc | isNewTyCon tc = ptext SLIT("(nt)")
- | otherwise = empty
-#endif
-\end{code}
\ No newline at end of file
+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 = 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 (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
+ | isNewTyCon tc = ifPprDebug (if isRecursiveTyCon tc
+ then ptext SLIT("<recnt>")
+ else ptext SLIT("<nt>")
+ ) <> ppr tc
+ | otherwise = ppr tc
+
+-------------------
+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}
+
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