2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[HsTypes]{Abstract syntax: user-defined types}
8 HsType(..), HsTyVarBndr(..), HsTyOp(..),
9 , HsContext, HsPred(..)
10 , HsTupCon(..), hsTupParens, mkHsTupCon,
13 , mkHsForAllTy, mkHsDictTy, mkHsIParamTy
14 , hsTyVarName, hsTyVarNames, replaceTyVarName
18 , PostTcType, placeHolderType,
21 , SyntaxName, placeHolderName,
24 , pprParendHsType, pprHsForAll, pprHsContext, ppr_hs_context, pprHsTyVarBndr
26 -- Equality over Hs things
27 , EqHsEnv, emptyEqHsEnv, extendEqHsEnv,
28 , eqWithHsTyVars, eq_hsVar, eq_hsVars, eq_hsTyVars, eq_hsType, eq_hsContext, eqListBy
30 -- Converting from Type to HsType
31 , toHsType, toHsTyVar, toHsTyVars, toHsContext, toHsFDs
34 #include "HsVersions.h"
36 import Class ( FunDep )
37 import TcType ( Type, Kind, ThetaType, SourceType(..),
38 tcSplitSigmaTy, liftedTypeKind, eqKind, tcEqType
40 import TypeRep ( Type(..), TyNote(..) ) -- toHsType sees the representation
41 import TyCon ( isTupleTyCon, tupleTyConBoxity, tyConArity, isNewTyCon, getSynTyConDefn )
42 import RdrName ( RdrName, mkUnqual )
43 import Name ( Name, getName, mkInternalName )
44 import OccName ( NameSpace, mkVarOcc, tvName )
45 import Var ( TyVar, tyVarKind )
46 import Subst ( substTyWith )
47 import PprType ( {- instance Outputable Kind -}, pprParendKind, pprKind )
48 import BasicTypes ( Boxity(..), Arity, IPName, tupleParens )
49 import PrelNames ( mkTupConRdrName, listTyConKey, parrTyConKey,
50 usOnceTyConKey, usManyTyConKey, hasKey, unboundKey,
51 usOnceTyConName, usManyTyConName )
52 import SrcLoc ( builtinSrcLoc )
53 import Util ( eqListBy, lengthIs )
59 %************************************************************************
61 \subsection{Annotating the syntax}
63 %************************************************************************
66 type PostTcType = Type -- Used for slots in the abstract syntax
67 -- where we want to keep slot for a type
68 -- to be added by the type checker...but
69 -- before typechecking it's just bogus
71 placeHolderType :: PostTcType -- Used before typechecking
72 placeHolderType = panic "Evaluated the place holder for a PostTcType"
75 type SyntaxName = Name -- These names are filled in by the renamer
76 -- Before then they are a placeHolderName (so that
77 -- we can still print the HsSyn)
78 -- They correspond to "rebindable syntax";
79 -- See RnEnv.lookupSyntaxName
81 placeHolderName :: SyntaxName
82 placeHolderName = mkInternalName unboundKey
83 (mkVarOcc FSLIT("syntaxPlaceHolder"))
88 %************************************************************************
90 \subsection{Data types}
92 %************************************************************************
94 This is the syntax for types as seen in type signatures.
97 type HsContext name = [HsPred name]
99 data HsPred name = HsClassP name [HsType name]
100 | HsIParam (IPName name) (HsType name)
103 = HsForAllTy (Maybe [HsTyVarBndr name]) -- Nothing for implicitly quantified signatures
107 | HsTyVar name -- Type variable or type constructor
109 | HsAppTy (HsType name)
112 | HsFunTy (HsType name) -- function type
115 | HsListTy (HsType name) -- Element type
117 | HsPArrTy (HsType name) -- Elem. type of parallel array: [:t:]
119 | HsTupleTy (HsTupCon name)
120 [HsType name] -- Element types (length gives arity)
122 | HsOpTy (HsType name) (HsTyOp name) (HsType name)
124 | HsParTy (HsType name) -- Parenthesis preserved for the
125 -- precedence parser; are removed by
128 | HsNumTy Integer -- Generics only
130 -- these next two are only used in interfaces
131 | HsPredTy (HsPred name)
133 | HsKindSig (HsType name) -- (ty :: kind)
134 Kind -- A type with a kind signature
137 data HsTyOp name = HsArrow | HsTyOp name
138 -- Function arrows from *source* get read in as HsOpTy t1 HsArrow t2
139 -- But when we generate or parse interface files, we use HsFunTy.
140 -- This keeps interfaces a bit smaller, because there are a lot of arrows
142 -----------------------
143 hsUsOnce, hsUsMany :: HsType RdrName
144 hsUsOnce = HsTyVar (mkUnqual tvName FSLIT(".")) -- deep magic
145 hsUsMany = HsTyVar (mkUnqual tvName FSLIT("!")) -- deep magic
147 hsUsOnce_Name, hsUsMany_Name :: HsType Name
148 hsUsOnce_Name = HsTyVar usOnceTyConName
149 hsUsMany_Name = HsTyVar usManyTyConName
151 -----------------------
152 data HsTupCon name = HsTupCon name Boxity Arity
154 instance Eq name => Eq (HsTupCon name) where
155 (HsTupCon _ b1 a1) == (HsTupCon _ b2 a2) = b1==b2 && a1==a2
157 mkHsTupCon :: NameSpace -> Boxity -> [a] -> HsTupCon RdrName
158 mkHsTupCon space boxity args = HsTupCon (mkTupConRdrName space boxity arity) boxity arity
162 hsTupParens :: HsTupCon name -> SDoc -> SDoc
163 hsTupParens (HsTupCon _ b _) p = tupleParens b p
165 -----------------------
166 -- Combine adjacent for-alls.
167 -- The following awkward situation can happen otherwise:
168 -- f :: forall a. ((Num a) => Int)
169 -- might generate HsForAll (Just [a]) [] (HsForAll Nothing [Num a] t)
170 -- Then a isn't discovered as ambiguous, and we abstract the AbsBinds wrt []
171 -- but the export list abstracts f wrt [a]. Disaster.
173 -- A valid type must have one for-all at the top of the type, or of the fn arg types
175 mkHsForAllTy (Just []) [] ty = ty -- Explicit for-all with no tyvars
176 mkHsForAllTy mtvs1 [] (HsForAllTy mtvs2 ctxt ty) = mkHsForAllTy (mtvs1 `plus` mtvs2) ctxt ty
178 mtvs1 `plus` Nothing = mtvs1
179 Nothing `plus` mtvs2 = mtvs2
180 (Just tvs1) `plus` (Just tvs2) = Just (tvs1 ++ tvs2)
181 mkHsForAllTy tvs ctxt ty = HsForAllTy tvs ctxt ty
183 mkHsDictTy cls tys = HsPredTy (HsClassP cls tys)
184 mkHsIParamTy v ty = HsPredTy (HsIParam v ty)
186 data HsTyVarBndr name
188 | IfaceTyVar name Kind
189 -- *** NOTA BENE *** A "monotype" in a pragma can have
190 -- for-alls in it, (mostly to do with dictionaries). These
191 -- must be explicitly Kinded.
193 hsTyVarName (UserTyVar n) = n
194 hsTyVarName (IfaceTyVar n _) = n
196 hsTyVarNames tvs = map hsTyVarName tvs
198 replaceTyVarName :: HsTyVarBndr name1 -> name2 -> HsTyVarBndr name2
199 replaceTyVarName (UserTyVar n) n' = UserTyVar n'
200 replaceTyVarName (IfaceTyVar n k) n' = IfaceTyVar n' k
205 getHsInstHead :: HsType name -> ([HsTyVarBndr name], (name, [HsType name]))
206 -- Split up an instance decl type, returning the 'head' part
208 -- In interface fiels, the type of the decl is held like this:
209 -- forall a. Foo a -> Baz (T a)
210 -- so we have to strip off function argument types,
211 -- as well as the bit before the '=>' (which is always
212 -- empty in interface files)
214 -- The parser ensures the type will have the right shape.
215 -- (e.g. see ParseUtil.checkInstType)
217 getHsInstHead (HsForAllTy (Just tvs) _ tau) = (tvs, get_head1 tau)
218 getHsInstHead tau = ([], get_head1 tau)
220 get_head1 (HsFunTy _ ty) = get_head1 ty
221 get_head1 (HsPredTy (HsClassP cls tys)) = (cls,tys)
225 %************************************************************************
227 \subsection{Pretty printing}
229 %************************************************************************
231 NB: these types get printed into interface files, so
232 don't change the printing format lightly
235 instance (Outputable name) => Outputable (HsType name) where
236 ppr ty = pprHsType ty
238 instance (Outputable name) => Outputable (HsTyOp name) where
239 ppr HsArrow = ftext FSLIT("->")
240 ppr (HsTyOp n) = ppr n
242 instance (Outputable name) => Outputable (HsTyVarBndr name) where
243 ppr (UserTyVar name) = ppr name
244 ppr (IfaceTyVar name kind) = pprHsTyVarBndr name kind
246 instance Outputable name => Outputable (HsPred name) where
247 ppr (HsClassP clas tys) = ppr clas <+> hsep (map pprParendHsType tys)
248 ppr (HsIParam n ty) = hsep [ppr n, dcolon, ppr ty]
250 pprHsTyVarBndr :: Outputable name => name -> Kind -> SDoc
251 pprHsTyVarBndr name kind | kind `eqKind` liftedTypeKind = ppr name
252 | otherwise = hsep [ppr name, dcolon, pprParendKind kind]
254 pprHsForAll [] [] = empty
256 -- This printer is used for both interface files and
257 -- printing user types in error messages; and alas the
258 -- two use slightly different syntax. Ah well.
259 = getPprStyle $ \ sty ->
260 if userStyle sty then
261 ptext SLIT("forall") <+> interppSP tvs <> dot <+>
262 -- **! ToDo: want to hide uvars from user, but not enough info
263 -- in a HsTyVarBndr name (see PprType). KSW 2000-10.
265 else -- Used in interfaces
266 ptext SLIT("__forall") <+> interppSP tvs <+>
267 ppr_hs_context cxt <+> ptext SLIT("=>")
269 pprHsContext :: (Outputable name) => HsContext name -> SDoc
270 pprHsContext [] = empty
271 pprHsContext cxt = ppr_hs_context cxt <+> ptext SLIT("=>")
273 ppr_hs_context [] = empty
274 ppr_hs_context cxt = parens (interpp'SP cxt)
278 pREC_TOP = (0 :: Int) -- type in ParseIface.y
279 pREC_FUN = (1 :: Int) -- btype in ParseIface.y
280 pREC_CON = (2 :: Int) -- atype in ParseIface.y
282 maybeParen :: Bool -> SDoc -> SDoc
283 maybeParen True p = parens p
284 maybeParen False p = p
286 -- printing works more-or-less as for Types
288 pprHsType, pprParendHsType :: (Outputable name) => HsType name -> SDoc
290 pprHsType ty = ppr_mono_ty pREC_TOP ty
291 pprParendHsType ty = ppr_mono_ty pREC_CON ty
293 ppr_mono_ty ctxt_prec (HsForAllTy maybe_tvs ctxt ty)
294 = maybeParen (ctxt_prec >= pREC_FUN) $
295 sep [pp_header, pprHsType ty]
297 pp_header = case maybe_tvs of
298 Just tvs -> pprHsForAll tvs ctxt
299 Nothing -> pprHsContext ctxt
301 ppr_mono_ty ctxt_prec (HsTyVar name)
304 ppr_mono_ty ctxt_prec (HsFunTy ty1 ty2)
305 = let p1 = ppr_mono_ty pREC_FUN ty1
306 p2 = ppr_mono_ty pREC_TOP ty2
308 maybeParen (ctxt_prec >= pREC_FUN)
309 (sep [p1, (<>) (ptext SLIT("-> ")) p2])
311 ppr_mono_ty ctxt_prec (HsTupleTy con tys) = hsTupParens con (interpp'SP tys)
312 ppr_mono_ty ctxt_prec (HsKindSig ty kind) = parens (ppr_mono_ty pREC_TOP ty <+> dcolon <+> pprKind kind)
313 ppr_mono_ty ctxt_prec (HsListTy ty) = brackets (ppr_mono_ty pREC_TOP ty)
314 ppr_mono_ty ctxt_prec (HsPArrTy ty) = pabrackets (ppr_mono_ty pREC_TOP ty)
316 pabrackets p = ptext SLIT("[:") <> p <> ptext SLIT(":]")
318 ppr_mono_ty ctxt_prec (HsAppTy fun_ty arg_ty) =
319 maybeParen (ctxt_prec >= pREC_CON)
320 (hsep [ppr_mono_ty pREC_FUN fun_ty, ppr_mono_ty pREC_CON arg_ty])
322 ppr_mono_ty ctxt_prec (HsPredTy pred)
325 ppr_mono_ty ctxt_prec (HsOpTy ty1 op ty2) =
326 maybeParen (ctxt_prec >= pREC_FUN)
327 (ppr_mono_ty pREC_FUN ty1 <+> ppr op <+> ppr_mono_ty pREC_FUN ty2)
329 ppr_mono_ty ctxt_prec (HsParTy ty) = ppr_mono_ty ctxt_prec ty
330 -- `HsParTy' isn't useful for pretty printing, as it is removed by the type
331 -- checker and we need to be able to pretty print after type checking
333 ppr_mono_ty ctxt_prec (HsNumTy n) = integer n -- generics only
337 %************************************************************************
339 \subsection{Converting from Type to HsType}
341 %************************************************************************
343 @toHsType@ converts from a Type to a HsType, making the latter look as
344 user-friendly as possible. Notably, it uses synonyms where possible, and
345 expresses overloaded functions using the '=>' context part of a HsForAllTy.
348 toHsTyVar :: TyVar -> HsTyVarBndr Name
349 toHsTyVar tv = IfaceTyVar (getName tv) (tyVarKind tv)
351 toHsTyVars tvs = map toHsTyVar tvs
353 toHsType :: Type -> HsType Name
354 -- This function knows the representation of types
355 toHsType (TyVarTy tv) = HsTyVar (getName tv)
356 toHsType (FunTy arg res) = HsFunTy (toHsType arg) (toHsType res)
357 toHsType (AppTy fun arg) = HsAppTy (toHsType fun) (toHsType arg)
359 toHsType (NoteTy (SynNote ty@(TyConApp tycon tyargs)) real_ty)
360 | isNewTyCon tycon = toHsType ty
361 | syn_matches = toHsType ty -- Use synonyms if possible!!
364 pprTrace "WARNING: synonym info lost in .hi file for " (ppr syn_ty) $
366 toHsType real_ty -- but drop it if not.
368 syn_matches = ty_from_syn `tcEqType` real_ty
369 (tyvars,syn_ty) = getSynTyConDefn tycon
370 ty_from_syn = substTyWith tyvars tyargs syn_ty
372 -- We only use the type synonym in the file if this doesn't cause
373 -- us to lose important information. This matters for usage
374 -- annotations. It's an issue if some of the args to the synonym
375 -- have arrows in them, or if the synonym's RHS has an arrow; for
376 -- example, with nofib/real/ebnf2ps/ in Parsers.using.
378 -- **! It would be nice if when this test fails we could still
379 -- write the synonym in as a Note, so we don't lose the info for
380 -- error messages, but it's too much work for right now.
383 toHsType (NoteTy _ ty) = toHsType ty
385 toHsType (SourceTy (NType tc tys)) = foldl HsAppTy (HsTyVar (getName tc)) (map toHsType tys)
386 toHsType (SourceTy pred) = HsPredTy (toHsPred pred)
388 toHsType ty@(TyConApp tc tys) -- Must be saturated because toHsType's arg is of kind *
389 | not saturated = generic_case
390 | isTupleTyCon tc = HsTupleTy (HsTupCon (getName tc) (tupleTyConBoxity tc) (tyConArity tc)) tys'
391 | tc `hasKey` listTyConKey = HsListTy (head tys')
392 | tc `hasKey` parrTyConKey = HsPArrTy (head tys')
393 | tc `hasKey` usOnceTyConKey = hsUsOnce_Name -- must print !, . unqualified
394 | tc `hasKey` usManyTyConKey = hsUsMany_Name -- must print !, . unqualified
395 | otherwise = generic_case
397 generic_case = foldl HsAppTy (HsTyVar (getName tc)) tys'
398 tys' = map toHsType tys
399 saturated = tys `lengthIs` tyConArity tc
401 toHsType ty@(ForAllTy _ _) = case tcSplitSigmaTy ty of
402 (tvs, preds, tau) -> HsForAllTy (Just (map toHsTyVar tvs))
406 toHsPred (ClassP cls tys) = HsClassP (getName cls) (map toHsType tys)
407 toHsPred (IParam n ty) = HsIParam n (toHsType ty)
409 toHsContext :: ThetaType -> HsContext Name
410 toHsContext theta = map toHsPred theta
412 toHsFDs :: [FunDep TyVar] -> [FunDep Name]
413 toHsFDs fds = [(map getName ns, map getName ms) | (ns,ms) <- fds]
417 %************************************************************************
419 \subsection{Comparison}
421 %************************************************************************
424 instance Ord a => Eq (HsType a) where
425 -- The Ord is needed because we keep a
426 -- finite map of variables to variables
427 (==) a b = eq_hsType emptyEqHsEnv a b
429 instance Ord a => Eq (HsPred a) where
430 (==) a b = eq_hsPred emptyEqHsEnv a b
432 eqWithHsTyVars :: Ord name =>
433 [HsTyVarBndr name] -> [HsTyVarBndr name]
434 -> (EqHsEnv name -> Bool) -> Bool
435 eqWithHsTyVars = eq_hsTyVars emptyEqHsEnv
439 type EqHsEnv n = FiniteMap n n
440 -- Tracks the mapping from L-variables to R-variables
442 eq_hsVar :: Ord n => EqHsEnv n -> n -> n -> Bool
443 eq_hsVar env n1 n2 = case lookupFM env n1 of
447 extendEqHsEnv env n1 n2
449 | otherwise = addToFM env n1 n2
451 emptyEqHsEnv :: EqHsEnv n
452 emptyEqHsEnv = emptyFM
455 We do define a specialised equality for these \tr{*Type} types; used
456 in checking interfaces.
460 eq_hsTyVars env [] [] k = k env
461 eq_hsTyVars env (tv1:tvs1) (tv2:tvs2) k = eq_hsTyVar env tv1 tv2 $ \ env ->
462 eq_hsTyVars env tvs1 tvs2 k
463 eq_hsTyVars env _ _ _ = False
465 eq_hsTyVar env (UserTyVar v1) (UserTyVar v2) k = k (extendEqHsEnv env v1 v2)
466 eq_hsTyVar env (IfaceTyVar v1 k1) (IfaceTyVar v2 k2) k = k1 `eqKind` k2 && k (extendEqHsEnv env v1 v2)
467 eq_hsTyVar env _ _ _ = False
469 eq_hsVars env [] [] k = k env
470 eq_hsVars env (v1:bs1) (v2:bs2) k = eq_hsVars (extendEqHsEnv env v1 v2) bs1 bs2 k
471 eq_hsVars env _ _ _ = False
476 eq_hsTypes env = eqListBy (eq_hsType env)
479 eq_hsType env (HsForAllTy tvs1 c1 t1) (HsForAllTy tvs2 c2 t2)
480 = eq_tvs tvs1 tvs2 $ \env ->
481 eq_hsContext env c1 c2 &&
484 eq_tvs Nothing (Just _) k = False
485 eq_tvs Nothing Nothing k = k env
486 eq_tvs (Just _) Nothing k = False
487 eq_tvs (Just tvs1) (Just tvs2) k = eq_hsTyVars env tvs1 tvs2 k
489 eq_hsType env (HsTyVar n1) (HsTyVar n2)
492 eq_hsType env (HsTupleTy c1 tys1) (HsTupleTy c2 tys2)
493 = (c1 == c2) && eq_hsTypes env tys1 tys2
495 eq_hsType env (HsListTy ty1) (HsListTy ty2)
496 = eq_hsType env ty1 ty2
498 eq_hsType env (HsKindSig ty1 k1) (HsKindSig ty2 k2)
499 = eq_hsType env ty1 ty2 && k1 `eqKind` k2
501 eq_hsType env (HsPArrTy ty1) (HsPArrTy ty2)
502 = eq_hsType env ty1 ty2
504 eq_hsType env (HsAppTy fun_ty1 arg_ty1) (HsAppTy fun_ty2 arg_ty2)
505 = eq_hsType env fun_ty1 fun_ty2 && eq_hsType env arg_ty1 arg_ty2
507 eq_hsType env (HsFunTy a1 b1) (HsFunTy a2 b2)
508 = eq_hsType env a1 a2 && eq_hsType env b1 b2
510 eq_hsType env (HsPredTy p1) (HsPredTy p2)
511 = eq_hsPred env p1 p2
513 eq_hsType env (HsOpTy lty1 op1 rty1) (HsOpTy lty2 op2 rty2)
514 = eq_hsOp env op1 op2 && eq_hsType env lty1 lty2 && eq_hsType env rty1 rty2
516 eq_hsType env ty1 ty2 = False
519 eq_hsOp env (HsTyOp n1) (HsTyOp n2) = eq_hsVar env n1 n2
520 eq_hsOp env HsArrow HsArrow = True
521 eq_hsOp env op1 op2 = False
524 eq_hsContext env a b = eqListBy (eq_hsPred env) a b
527 eq_hsPred env (HsClassP c1 tys1) (HsClassP c2 tys2)
528 = c1 == c2 && eq_hsTypes env tys1 tys2
529 eq_hsPred env (HsIParam n1 ty1) (HsIParam n2 ty2)
530 = n1 == n2 && eq_hsType env ty1 ty2
531 eq_hsPred env _ _ = False