%
\section[HsTypes]{Abstract syntax: user-defined types}
-If compiled without \tr{#define COMPILING_GHC}, you get
-(part of) a Haskell-abstract-syntax library. With it,
-you get part of GHC.
-
\begin{code}
module HsTypes (
- HsType(..), HsTyVar(..),
- Context, ClassAssertion
-
- , mkHsForAllTy
- , getTyVarName, replaceTyVarName
- , pprParendHsType
- , pprForAll, pprContext, pprClassAssertion
- , cmpHsType, cmpHsTypes, cmpContext
+ HsType(..), LHsType,
+ HsTyVarBndr(..), LHsTyVarBndr,
+ HsExplicitForAll(..),
+ HsContext, LHsContext,
+ HsPred(..), LHsPred,
+
+ LBangType, BangType, HsBang(..),
+ getBangType, getBangStrictness,
+
+ mkExplicitHsForAllTy, mkImplicitHsForAllTy,
+ hsTyVarName, hsTyVarNames, replaceTyVarName,
+ hsLTyVarName, hsLTyVarNames, hsLTyVarLocName, hsLTyVarLocNames,
+ splitHsInstDeclTy, splitHsFunType,
+
+ -- Type place holder
+ PostTcType, placeHolderType,
+
+ -- Printing
+ pprParendHsType, pprHsForAll, pprHsContext, ppr_hs_context, pprHsTyVarBndr
) where
#include "HsVersions.h"
-import Type ( Kind )
-import PprType ( {- instance Outputable Kind -} )
+import {-# SOURCE #-} HsExpr ( HsSplice, pprSplice )
+
+import Type ( Type )
+import Kind ( {- instance Outputable Kind -}, Kind,
+ pprParendKind, pprKind, isLiftedTypeKind )
+import BasicTypes ( IPName, Boxity, tupleParens )
+import SrcLoc ( Located(..), unLoc, noSrcSpan )
+import StaticFlags ( opt_PprStyle_Debug )
import Outputable
-import Util ( thenCmp, cmpList )
\end{code}
+
+%************************************************************************
+%* *
+\subsection{Annotating the syntax}
+%* *
+%************************************************************************
+
+\begin{code}
+type PostTcType = Type -- Used for slots in the abstract syntax
+ -- where we want to keep slot for a type
+ -- to be added by the type checker...but
+ -- before typechecking it's just bogus
+
+placeHolderType :: PostTcType -- Used before typechecking
+placeHolderType = panic "Evaluated the place holder for a PostTcType"
+\end{code}
+
+%************************************************************************
+%* *
+\subsection{Bang annotations}
+%* *
+%************************************************************************
+
+\begin{code}
+type LBangType name = Located (BangType name)
+type BangType name = HsType name -- Bangs are in the HsType data type
+
+data HsBang = HsNoBang -- Only used as a return value for getBangStrictness,
+ -- never appears on a HsBangTy
+ | HsStrict -- !
+ | HsUnbox -- {-# UNPACK #-} ! (GHC extension, meaning "unbox")
+
+instance Outputable HsBang where
+ ppr (HsNoBang) = empty
+ ppr (HsStrict) = char '!'
+ ppr (HsUnbox) = ptext SLIT("!!")
+
+getBangType :: LHsType a -> LHsType a
+getBangType (L _ (HsBangTy _ ty)) = ty
+getBangType ty = ty
+
+getBangStrictness :: LHsType a -> HsBang
+getBangStrictness (L _ (HsBangTy s _)) = s
+getBangStrictness _ = HsNoBang
+\end{code}
+
+
+%************************************************************************
+%* *
+\subsection{Data types}
+%* *
+%************************************************************************
+
This is the syntax for types as seen in type signatures.
\begin{code}
-type Context name = [ClassAssertion name]
+type LHsContext name = Located (HsContext name)
+
+type HsContext name = [LHsPred name]
+
+type LHsPred name = Located (HsPred name)
+
+data HsPred name = HsClassP name [LHsType name]
+ | HsIParam (IPName name) (LHsType name)
-type ClassAssertion name = (name, [HsType name])
- -- The type is usually a type variable, but it
- -- doesn't have to be when reading interface files
+type LHsType name = Located (HsType name)
data HsType name
- = HsForAllTy [HsTyVar name]
- (Context name)
- (HsType name)
+ = HsForAllTy HsExplicitForAll -- Renamer leaves this flag unchanged, to record the way
+ -- the user wrote it originally, so that the printer can
+ -- print it as the user wrote it
+ [LHsTyVarBndr name] -- With ImplicitForAll, this is the empty list
+ -- until the renamer fills in the variables
+ (LHsContext name)
+ (LHsType name)
- | MonoTyVar name -- Type variable
+ | HsTyVar name -- Type variable or type constructor
- | MonoTyApp (HsType name)
- (HsType name)
+ | HsBangTy HsBang (LHsType name) -- Bang-style type annotations
- | MonoFunTy (HsType name) -- function type
- (HsType name)
+ | HsAppTy (LHsType name)
+ (LHsType name)
- | MonoListTy (HsType name) -- Element type
+ | HsFunTy (LHsType name) -- function type
+ (LHsType name)
- | MonoTupleTy [HsType name] -- Element types (length gives arity)
- Bool -- boxed?
+ | HsListTy (LHsType name) -- Element type
- -- these next two are only used in unfoldings in interfaces
- | MonoDictTy name -- Class
- [HsType name]
+ | HsPArrTy (LHsType name) -- Elem. type of parallel array: [:t:]
-mkHsForAllTy [] [] ty = ty
-mkHsForAllTy tvs ctxt ty = HsForAllTy tvs ctxt ty
+ | HsTupleTy Boxity
+ [LHsType name] -- Element types (length gives arity)
-data HsTyVar name
- = UserTyVar name
- | IfaceTyVar name Kind
- -- *** NOTA BENE *** A "monotype" in a pragma can have
- -- for-alls in it, (mostly to do with dictionaries). These
- -- must be explicitly Kinded.
+ | HsOpTy (LHsType name) (Located name) (LHsType name)
-getTyVarName (UserTyVar n) = n
-getTyVarName (IfaceTyVar n _) = n
+ | HsParTy (LHsType name)
+ -- Parenthesis preserved for the precedence re-arrangement in RnTypes
+ -- It's important that a * (b + c) doesn't get rearranged to (a*b) + c!
+ --
+ -- However, NB that toHsType doesn't add HsParTys (in an effort to keep
+ -- interface files smaller), so when printing a HsType we may need to
+ -- add parens.
-replaceTyVarName :: HsTyVar name1 -> name2 -> HsTyVar name2
-replaceTyVarName (UserTyVar n) n' = UserTyVar n'
-replaceTyVarName (IfaceTyVar n k) n' = IfaceTyVar n' k
-\end{code}
+ | HsNumTy Integer -- Generics only
+ | HsPredTy (HsPred name) -- Only used in the type of an instance
+ -- declaration, eg. Eq [a] -> Eq a
+ -- ^^^^
+ -- HsPredTy
+ -- Note no need for location info on the
+ -- enclosed HsPred; the one on the type will do
-%************************************************************************
-%* *
-\subsection{Pretty printing}
-%* *
-%************************************************************************
+ | HsKindSig (LHsType name) -- (ty :: kind)
+ Kind -- A type with a kind signature
-\begin{code}
+ | HsSpliceTy (HsSplice name)
-instance (Outputable name) => Outputable (HsType name) where
- ppr ty = pprHsType ty
+data HsExplicitForAll = Explicit | Implicit
-instance (Outputable name) => Outputable (HsTyVar name) where
- ppr (UserTyVar name) = ppr name
- ppr (IfaceTyVar name kind) = hsep [ppr name, dcolon, ppr kind]
+-----------------------
+-- Combine adjacent for-alls.
+-- The following awkward situation can happen otherwise:
+-- f :: forall a. ((Num a) => Int)
+-- might generate HsForAll (Just [a]) [] (HsForAll Nothing [Num a] t)
+-- Then a isn't discovered as ambiguous, and we abstract the AbsBinds wrt []
+-- but the export list abstracts f wrt [a]. Disaster.
+--
+-- A valid type must have one for-all at the top of the type, or of the fn arg types
-pprForAll [] = empty
-pprForAll tvs = ptext SLIT("forall") <+> interppSP tvs <> ptext SLIT(".")
+mkImplicitHsForAllTy ctxt ty = mkHsForAllTy Implicit [] ctxt ty
+mkExplicitHsForAllTy tvs ctxt ty = mkHsForAllTy Explicit tvs ctxt ty
-pprContext :: (Outputable name) => Context name -> SDoc
-pprContext [] = empty
-pprContext context = parens (hsep (punctuate comma (map pprClassAssertion context))) <+> ptext SLIT("=>")
+mkHsForAllTy :: HsExplicitForAll -> [LHsTyVarBndr name] -> LHsContext name -> LHsType name -> HsType name
+-- Smart constructor for HsForAllTy
+mkHsForAllTy exp tvs (L _ []) ty = mk_forall_ty exp tvs ty
+mkHsForAllTy exp tvs ctxt ty = HsForAllTy exp tvs ctxt ty
-pprClassAssertion :: (Outputable name) => ClassAssertion name -> SDoc
-pprClassAssertion (clas, tys)
- = ppr clas <+> hsep (map pprParendHsType tys)
-\end{code}
+-- mk_forall_ty makes a pure for-all type (no context)
+mk_forall_ty exp tvs (L _ (HsParTy ty)) = mk_forall_ty exp tvs ty
+mk_forall_ty exp1 tvs1 (L _ (HsForAllTy exp2 tvs2 ctxt ty)) = mkHsForAllTy (exp1 `plus` exp2) (tvs1 ++ tvs2) ctxt ty
+mk_forall_ty exp tvs ty = HsForAllTy exp tvs (L noSrcSpan []) ty
+ -- Even if tvs is empty, we still make a HsForAll!
+ -- In the Implicit case, this signals the place to do implicit quantification
+ -- In the Explicit case, it prevents implicit quantification
+ -- (see the sigtype production in Parser.y.pp)
+ -- so that (forall. ty) isn't implicitly quantified
-\begin{code}
-pREC_TOP = (0 :: Int)
-pREC_FUN = (1 :: Int)
-pREC_CON = (2 :: Int)
+Implicit `plus` Implicit = Implicit
+exp1 `plus` exp2 = Explicit
-maybeParen :: Bool -> SDoc -> SDoc
-maybeParen True p = parens p
-maybeParen False p = p
-
--- printing works more-or-less as for Types
+type LHsTyVarBndr name = Located (HsTyVarBndr name)
-pprHsType, pprParendHsType :: (Outputable name) => HsType name -> SDoc
+data HsTyVarBndr name
+ = UserTyVar name
+ | KindedTyVar name Kind
+ -- *** NOTA BENE *** A "monotype" in a pragma can have
+ -- for-alls in it, (mostly to do with dictionaries). These
+ -- must be explicitly Kinded.
-pprHsType ty = ppr_mono_ty pREC_TOP ty
-pprParendHsType ty = ppr_mono_ty pREC_CON ty
+hsTyVarName :: HsTyVarBndr name -> name
+hsTyVarName (UserTyVar n) = n
+hsTyVarName (KindedTyVar n _) = n
-ppr_mono_ty ctxt_prec (HsForAllTy tvs ctxt ty)
- = maybeParen (ctxt_prec >= pREC_FUN) $
- sep [pprForAll tvs, pprContext ctxt, pprHsType ty]
+hsLTyVarName :: LHsTyVarBndr name -> name
+hsLTyVarName = hsTyVarName . unLoc
-ppr_mono_ty ctxt_prec (MonoTyVar name)
- = ppr name
+hsTyVarNames :: [HsTyVarBndr name] -> [name]
+hsTyVarNames tvs = map hsTyVarName tvs
-ppr_mono_ty ctxt_prec (MonoFunTy ty1 ty2)
- = let p1 = ppr_mono_ty pREC_FUN ty1
- p2 = ppr_mono_ty pREC_TOP ty2
- in
- maybeParen (ctxt_prec >= pREC_FUN)
- (sep [p1, (<>) (ptext SLIT("-> ")) p2])
+hsLTyVarNames :: [LHsTyVarBndr name] -> [name]
+hsLTyVarNames = map hsLTyVarName
-ppr_mono_ty ctxt_prec (MonoTupleTy tys True)
- = parens (sep (punctuate comma (map ppr tys)))
-ppr_mono_ty ctxt_prec (MonoTupleTy tys False)
- = ptext SLIT("(#") <> sep (punctuate comma (map ppr tys)) <> ptext SLIT("#)")
+hsLTyVarLocName :: LHsTyVarBndr name -> Located name
+hsLTyVarLocName = fmap hsTyVarName
-ppr_mono_ty ctxt_prec (MonoListTy ty)
- = brackets (ppr_mono_ty pREC_TOP ty)
+hsLTyVarLocNames :: [LHsTyVarBndr name] -> [Located name]
+hsLTyVarLocNames = map hsLTyVarLocName
+
+replaceTyVarName :: HsTyVarBndr name1 -> name2 -> HsTyVarBndr name2
+replaceTyVarName (UserTyVar n) n' = UserTyVar n'
+replaceTyVarName (KindedTyVar n k) n' = KindedTyVar n' k
+\end{code}
-ppr_mono_ty ctxt_prec (MonoTyApp fun_ty arg_ty)
- = maybeParen (ctxt_prec >= pREC_CON)
- (hsep [ppr_mono_ty pREC_FUN fun_ty, ppr_mono_ty pREC_CON arg_ty])
-ppr_mono_ty ctxt_prec (MonoDictTy clas tys)
- = ppr clas <+> hsep (map (ppr_mono_ty pREC_CON) tys)
+\begin{code}
+splitHsInstDeclTy
+ :: OutputableBndr name
+ => HsType name
+ -> ([LHsTyVarBndr name], HsContext name, name, [LHsType name])
+ -- Split up an instance decl type, returning the pieces
+
+splitHsInstDeclTy inst_ty
+ = case inst_ty of
+ HsParTy (L _ ty) -> splitHsInstDeclTy ty
+ HsForAllTy _ tvs cxt (L _ ty) -> split_tau tvs (unLoc cxt) ty
+ other -> split_tau [] [] other
+ -- The type vars should have been computed by now, even if they were implicit
+ where
+ split_tau tvs cxt (HsPredTy (HsClassP cls tys)) = (tvs, cxt, cls, tys)
+ split_tau tvs cxt (HsParTy (L _ ty)) = split_tau tvs cxt ty
+
+-- Splits HsType into the (init, last) parts
+-- Breaks up any parens in the result type:
+-- splitHsFunType (a -> (b -> c)) = ([a,b], c)
+splitHsFunType :: LHsType name -> ([LHsType name], LHsType name)
+splitHsFunType (L l (HsFunTy x y)) = (x:args, res)
+ where
+ (args, res) = splitHsFunType y
+splitHsFunType (L _ (HsParTy ty)) = splitHsFunType ty
+splitHsFunType other = ([], other)
\end{code}
%************************************************************************
%* *
-\subsection{Comparison}
+\subsection{Pretty printing}
%* *
%************************************************************************
-We do define a specialised equality for these \tr{*Type} types; used
-in checking interfaces. Most any other use is likely to be {\em
-wrong}, so be careful!
+NB: these types get printed into interface files, so
+ don't change the printing format lightly
\begin{code}
-cmpHsTyVar :: (a -> a -> Ordering) -> HsTyVar a -> HsTyVar a -> Ordering
-cmpHsType :: (a -> a -> Ordering) -> HsType a -> HsType a -> Ordering
-cmpHsTypes :: (a -> a -> Ordering) -> [HsType a] -> [HsType a] -> Ordering
-cmpContext :: (a -> a -> Ordering) -> Context a -> Context a -> Ordering
-
-cmpHsTyVar cmp (UserTyVar v1) (UserTyVar v2) = v1 `cmp` v2
-cmpHsTyVar cmp (IfaceTyVar v1 _) (IfaceTyVar v2 _) = v1 `cmp` v2
-cmpHsTyVar cmp (UserTyVar _) other = LT
-cmpHsTyVar cmp other1 other2 = GT
+instance (OutputableBndr name) => Outputable (HsType name) where
+ ppr ty = pprHsType ty
+instance (Outputable name) => Outputable (HsTyVarBndr name) where
+ ppr (UserTyVar name) = ppr name
+ ppr (KindedTyVar name kind) = pprHsTyVarBndr name kind
-cmpHsTypes cmp [] [] = EQ
-cmpHsTypes cmp [] tys2 = LT
-cmpHsTypes cmp tys1 [] = GT
-cmpHsTypes cmp (ty1:tys1) (ty2:tys2) = cmpHsType cmp ty1 ty2 `thenCmp` cmpHsTypes cmp tys1 tys2
+instance OutputableBndr name => Outputable (HsPred name) where
+ ppr (HsClassP clas tys) = ppr clas <+> hsep (map (pprParendHsType.unLoc) tys)
+ ppr (HsIParam n ty) = hsep [ppr n, dcolon, ppr ty]
-cmpHsType cmp (HsForAllTy tvs1 c1 t1) (HsForAllTy tvs2 c2 t2)
- = cmpList (cmpHsTyVar cmp) tvs1 tvs2 `thenCmp`
- cmpContext cmp c1 c2 `thenCmp`
- cmpHsType cmp t1 t2
+pprHsTyVarBndr :: Outputable name => name -> Kind -> SDoc
+pprHsTyVarBndr name kind | isLiftedTypeKind kind = ppr name
+ | otherwise = hsep [ppr name, dcolon, pprParendKind kind]
-cmpHsType cmp (MonoTyVar n1) (MonoTyVar n2)
- = cmp n1 n2
+pprHsForAll exp tvs cxt
+ | show_forall = forall_part <+> pprHsContext (unLoc cxt)
+ | otherwise = pprHsContext (unLoc cxt)
+ where
+ show_forall = opt_PprStyle_Debug
+ || (not (null tvs) && is_explicit)
+ is_explicit = case exp of {Explicit -> True; Implicit -> False}
+ forall_part = ptext SLIT("forall") <+> interppSP tvs <> dot
-cmpHsType cmp (MonoTupleTy tys1 b1) (MonoTupleTy tys2 b2)
- = (b1 `compare` b2) `thenCmp` cmpHsTypes cmp tys1 tys2
+pprHsContext :: (OutputableBndr name) => HsContext name -> SDoc
+pprHsContext [] = empty
+pprHsContext cxt = ppr_hs_context cxt <+> ptext SLIT("=>")
-cmpHsType cmp (MonoListTy ty1) (MonoListTy ty2)
- = cmpHsType cmp ty1 ty2
+ppr_hs_context [] = empty
+ppr_hs_context cxt = parens (interpp'SP cxt)
+\end{code}
-cmpHsType cmp (MonoTyApp fun_ty1 arg_ty1) (MonoTyApp fun_ty2 arg_ty2)
- = cmpHsType cmp fun_ty1 fun_ty2 `thenCmp` cmpHsType cmp arg_ty1 arg_ty2
+\begin{code}
+pREC_TOP = (0 :: Int) -- type in ParseIface.y
+pREC_FUN = (1 :: Int) -- btype in ParseIface.y
+ -- Used for LH arg of (->)
+pREC_OP = (2 :: Int) -- Used for arg of any infix operator
+ -- (we don't keep their fixities around)
+pREC_CON = (3 :: Int) -- Used for arg of type applicn:
+ -- always parenthesise unless atomic
+
+maybeParen :: Int -- Precedence of context
+ -> Int -- Precedence of top-level operator
+ -> SDoc -> SDoc -- Wrap in parens if (ctxt >= op)
+maybeParen ctxt_prec op_prec p | ctxt_prec >= op_prec = parens p
+ | otherwise = p
+
+-- printing works more-or-less as for Types
-cmpHsType cmp (MonoFunTy a1 b1) (MonoFunTy a2 b2)
- = cmpHsType cmp a1 a2 `thenCmp` cmpHsType cmp b1 b2
+pprHsType, pprParendHsType :: (OutputableBndr name) => HsType name -> SDoc
-cmpHsType cmp (MonoDictTy c1 tys1) (MonoDictTy c2 tys2)
- = cmp c1 c2 `thenCmp` cmpHsTypes cmp tys1 tys2
+pprHsType ty = getPprStyle $ \sty -> ppr_mono_ty pREC_TOP (prepare sty ty)
+pprParendHsType ty = ppr_mono_ty pREC_CON ty
-cmpHsType cmp ty1 ty2 -- tags must be different
- = let tag1 = tag ty1
- tag2 = tag ty2
+-- Before printing a type
+-- (a) Remove outermost HsParTy parens
+-- (b) Drop top-level for-all type variables in user style
+-- since they are implicit in Haskell
+prepare sty (HsParTy ty) = prepare sty (unLoc ty)
+prepare sty ty = ty
+
+ppr_mono_lty ctxt_prec ty = ppr_mono_ty ctxt_prec (unLoc ty)
+
+ppr_mono_ty ctxt_prec (HsForAllTy exp tvs ctxt ty)
+ = maybeParen ctxt_prec pREC_FUN $
+ sep [pprHsForAll exp tvs ctxt, ppr_mono_lty pREC_TOP ty]
+
+-- gaw 2004
+ppr_mono_ty ctxt_prec (HsBangTy b ty) = ppr b <> ppr ty
+ppr_mono_ty ctxt_prec (HsTyVar name) = ppr name
+ppr_mono_ty ctxt_prec (HsFunTy ty1 ty2) = ppr_fun_ty ctxt_prec ty1 ty2
+ppr_mono_ty ctxt_prec (HsTupleTy con tys) = tupleParens con (interpp'SP tys)
+ppr_mono_ty ctxt_prec (HsKindSig ty kind) = parens (ppr_mono_lty pREC_TOP ty <+> dcolon <+> pprKind kind)
+ppr_mono_ty ctxt_prec (HsListTy ty) = brackets (ppr_mono_lty pREC_TOP ty)
+ppr_mono_ty ctxt_prec (HsPArrTy ty) = pabrackets (ppr_mono_lty pREC_TOP ty)
+ppr_mono_ty ctxt_prec (HsPredTy pred) = braces (ppr pred)
+ppr_mono_ty ctxt_prec (HsNumTy n) = integer n -- generics only
+ppr_mono_ty ctxt_prec (HsSpliceTy s) = pprSplice s
+
+ppr_mono_ty ctxt_prec (HsAppTy fun_ty arg_ty)
+ = maybeParen ctxt_prec pREC_CON $
+ hsep [ppr_mono_lty pREC_FUN fun_ty, ppr_mono_lty pREC_CON arg_ty]
+
+ppr_mono_ty ctxt_prec (HsOpTy ty1 op ty2)
+ = maybeParen ctxt_prec pREC_OP $
+ ppr_mono_lty pREC_OP ty1 <+> ppr op <+> ppr_mono_lty pREC_OP ty2
+
+ppr_mono_ty ctxt_prec (HsParTy ty)
+ = parens (ppr_mono_lty pREC_TOP ty)
+ -- Put the parens in where the user did
+ -- But we still use the precedence stuff to add parens because
+ -- toHsType doesn't put in any HsParTys, so we may still need them
+
+--------------------------
+ppr_fun_ty ctxt_prec ty1 ty2
+ = let p1 = ppr_mono_lty pREC_FUN ty1
+ p2 = ppr_mono_lty pREC_TOP ty2
in
- if tag1 _LT_ tag2 then LT else GT
- where
- tag (MonoTyVar n1) = (ILIT(1) :: FAST_INT)
- tag (MonoTupleTy tys1 _) = ILIT(2)
- tag (MonoListTy ty1) = ILIT(3)
- tag (MonoTyApp tc1 tys1) = ILIT(4)
- tag (MonoFunTy a1 b1) = ILIT(5)
- tag (MonoDictTy c1 tys1) = ILIT(7)
- tag (HsForAllTy _ _ _) = ILIT(8)
-
--------------------
-cmpContext cmp a b
- = cmpList cmp_ctxt a b
- where
- cmp_ctxt (c1, tys1) (c2, tys2)
- = cmp c1 c2 `thenCmp` cmpHsTypes cmp tys1 tys2
+ maybeParen ctxt_prec pREC_FUN $
+ sep [p1, ptext SLIT("->") <+> p2]
+
+--------------------------
+pabrackets p = ptext SLIT("[:") <> p <> ptext SLIT(":]")
\end{code}
+
+
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