2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[HsTypes]{Abstract syntax: user-defined types}
8 HsType(..), HsTyVarBndr(..),
9 , HsContext, HsPred(..)
10 , HsTupCon(..), hsTupParens, mkHsTupCon,
13 , mkHsForAllTy, mkHsDictTy, mkHsIParamTy
14 , hsTyVarName, hsTyVarNames, replaceTyVarName
18 , PostTcType, placeHolderType,
21 , pprParendHsType, pprHsForAll, pprHsContext, pprHsTyVarBndr
23 -- Equality over Hs things
24 , EqHsEnv, emptyEqHsEnv, extendEqHsEnv,
25 , eqWithHsTyVars, eq_hsVar, eq_hsVars, eq_hsTyVars, eq_hsType, eq_hsContext, eqListBy
27 -- Converting from Type to HsType
28 , toHsType, toHsTyVar, toHsTyVars, toHsContext, toHsFDs
31 #include "HsVersions.h"
33 import Class ( FunDep )
34 import TcType ( Type, Kind, ThetaType, SourceType(..),
35 tcSplitSigmaTy, liftedTypeKind, eqKind, tcEqType
37 import TypeRep ( Type(..), TyNote(..) ) -- toHsType sees the representation
38 import TyCon ( isTupleTyCon, tupleTyConBoxity, tyConArity, isNewTyCon, getSynTyConDefn )
39 import RdrName ( RdrName, mkUnqual )
40 import Name ( Name, getName )
41 import OccName ( NameSpace, tvName )
42 import Var ( TyVar, tyVarKind )
43 import Subst ( substTyWith )
44 import PprType ( {- instance Outputable Kind -}, pprParendKind )
45 import BasicTypes ( Boxity(..), Arity, IPName, tupleParens )
46 import PrelNames ( mkTupConRdrName, listTyConKey, usOnceTyConKey, usManyTyConKey, hasKey,
47 usOnceTyConName, usManyTyConName
50 import Util ( eqListBy, lengthIs )
55 %************************************************************************
57 \subsection{Annotating the syntax}
59 %************************************************************************
62 type PostTcType = Type -- Used for slots in the abstract syntax
63 -- where we want to keep slot for a type
64 -- to be added by the type checker...but
65 -- before typechecking it's just bogus
67 placeHolderType :: PostTcType -- Used before typechecking
68 placeHolderType = panic "Evaluated the place holder for a PostTcType"
72 %************************************************************************
74 \subsection{Data types}
76 %************************************************************************
78 This is the syntax for types as seen in type signatures.
81 type HsContext name = [HsPred name]
83 data HsPred name = HsClassP name [HsType name]
84 | HsIParam (IPName name) (HsType name)
87 = HsForAllTy (Maybe [HsTyVarBndr name]) -- Nothing for implicitly quantified signatures
91 | HsTyVar name -- Type variable or type constructor
93 | HsAppTy (HsType name)
96 | HsFunTy (HsType name) -- function type
99 | HsListTy (HsType name) -- Element type
101 | HsTupleTy (HsTupCon name)
102 [HsType name] -- Element types (length gives arity)
104 | HsOpTy (HsType name) name (HsType name)
107 -- these next two are only used in interfaces
108 | HsPredTy (HsPred name)
110 | HsUsageTy (HsType name) -- Usage annotation
111 (HsType name) -- Annotated type
114 -----------------------
115 hsUsOnce, hsUsMany :: HsType RdrName
116 hsUsOnce = HsTyVar (mkUnqual tvName SLIT(".")) -- deep magic
117 hsUsMany = HsTyVar (mkUnqual tvName SLIT("!")) -- deep magic
119 hsUsOnce_Name, hsUsMany_Name :: HsType Name
120 hsUsOnce_Name = HsTyVar usOnceTyConName
121 hsUsMany_Name = HsTyVar usManyTyConName
123 -----------------------
124 data HsTupCon name = HsTupCon name Boxity Arity
126 instance Eq name => Eq (HsTupCon name) where
127 (HsTupCon _ b1 a1) == (HsTupCon _ b2 a2) = b1==b2 && a1==a2
129 mkHsTupCon :: NameSpace -> Boxity -> [a] -> HsTupCon RdrName
130 mkHsTupCon space boxity args = HsTupCon (mkTupConRdrName space boxity arity) boxity arity
134 hsTupParens :: HsTupCon name -> SDoc -> SDoc
135 hsTupParens (HsTupCon _ b _) p = tupleParens b p
137 -----------------------
138 -- Combine adjacent for-alls.
139 -- The following awkward situation can happen otherwise:
140 -- f :: forall a. ((Num a) => Int)
141 -- might generate HsForAll (Just [a]) [] (HsForAll Nothing [Num a] t)
142 -- Then a isn't discovered as ambiguous, and we abstract the AbsBinds wrt []
143 -- but the export list abstracts f wrt [a]. Disaster.
145 -- A valid type must have one for-all at the top of the type, or of the fn arg types
147 mkHsForAllTy (Just []) [] ty = ty -- Explicit for-all with no tyvars
148 mkHsForAllTy mtvs1 [] (HsForAllTy mtvs2 ctxt ty) = mkHsForAllTy (mtvs1 `plus` mtvs2) ctxt ty
150 mtvs1 `plus` Nothing = mtvs1
151 Nothing `plus` mtvs2 = mtvs2
152 (Just tvs1) `plus` (Just tvs2) = Just (tvs1 ++ tvs2)
153 mkHsForAllTy tvs ctxt ty = HsForAllTy tvs ctxt ty
155 mkHsDictTy cls tys = HsPredTy (HsClassP cls tys)
156 mkHsIParamTy v ty = HsPredTy (HsIParam v ty)
158 data HsTyVarBndr name
160 | IfaceTyVar name Kind
161 -- *** NOTA BENE *** A "monotype" in a pragma can have
162 -- for-alls in it, (mostly to do with dictionaries). These
163 -- must be explicitly Kinded.
165 hsTyVarName (UserTyVar n) = n
166 hsTyVarName (IfaceTyVar n _) = n
168 hsTyVarNames tvs = map hsTyVarName tvs
170 replaceTyVarName :: HsTyVarBndr name1 -> name2 -> HsTyVarBndr name2
171 replaceTyVarName (UserTyVar n) n' = UserTyVar n'
172 replaceTyVarName (IfaceTyVar n k) n' = IfaceTyVar n' k
177 getHsInstHead :: HsType name -> ([HsTyVarBndr name], (name, [HsType name]))
178 -- Split up an instance decl type, returning the 'head' part
180 -- In interface fiels, the type of the decl is held like this:
181 -- forall a. Foo a -> Baz (T a)
182 -- so we have to strip off function argument types,
183 -- as well as the bit before the '=>' (which is always
184 -- empty in interface files)
186 -- The parser ensures the type will have the right shape.
187 -- (e.g. see ParseUtil.checkInstType)
189 getHsInstHead (HsForAllTy (Just tvs) _ tau) = (tvs, get_head1 tau)
190 getHsInstHead tau = ([], get_head1 tau)
192 get_head1 (HsFunTy _ ty) = get_head1 ty
193 get_head1 (HsPredTy (HsClassP cls tys)) = (cls,tys)
197 %************************************************************************
199 \subsection{Pretty printing}
201 %************************************************************************
203 NB: these types get printed into interface files, so
204 don't change the printing format lightly
207 instance (Outputable name) => Outputable (HsType name) where
208 ppr ty = pprHsType ty
210 instance (Outputable name) => Outputable (HsTyVarBndr name) where
211 ppr (UserTyVar name) = ppr name
212 ppr (IfaceTyVar name kind) = pprHsTyVarBndr name kind
214 instance Outputable name => Outputable (HsPred name) where
215 ppr (HsClassP clas tys) = ppr clas <+> hsep (map pprParendHsType tys)
216 ppr (HsIParam n ty) = hsep [ppr n, dcolon, ppr ty]
218 pprHsTyVarBndr :: Outputable name => name -> Kind -> SDoc
219 pprHsTyVarBndr name kind | kind `eqKind` liftedTypeKind = ppr name
220 | otherwise = hsep [ppr name, dcolon, pprParendKind kind]
222 pprHsForAll [] [] = empty
224 -- This printer is used for both interface files and
225 -- printing user types in error messages; and alas the
226 -- two use slightly different syntax. Ah well.
227 = getPprStyle $ \ sty ->
228 if userStyle sty then
229 ptext SLIT("forall") <+> interppSP tvs <> dot <+>
230 -- **! ToDo: want to hide uvars from user, but not enough info
231 -- in a HsTyVarBndr name (see PprType). KSW 2000-10.
235 ppr_context cxt <+> ptext SLIT("=>")
237 else -- Used in interfaces
238 ptext SLIT("__forall") <+> interppSP tvs <+>
239 ppr_context cxt <+> ptext SLIT("=>")
241 pprHsContext :: (Outputable name) => HsContext name -> SDoc
242 pprHsContext [] = empty
243 pprHsContext cxt = ppr_context cxt <+> ptext SLIT("=>")
245 ppr_context [] = empty
246 ppr_context cxt = parens (interpp'SP cxt)
250 pREC_TOP = (0 :: Int) -- type in ParseIface.y
251 pREC_FUN = (1 :: Int) -- btype in ParseIface.y
252 pREC_CON = (2 :: Int) -- atype in ParseIface.y
254 maybeParen :: Bool -> SDoc -> SDoc
255 maybeParen True p = parens p
256 maybeParen False p = p
258 -- printing works more-or-less as for Types
260 pprHsType, pprParendHsType :: (Outputable name) => HsType name -> SDoc
262 pprHsType ty = ppr_mono_ty pREC_TOP ty
263 pprParendHsType ty = ppr_mono_ty pREC_CON ty
265 ppr_mono_ty ctxt_prec (HsForAllTy maybe_tvs ctxt ty)
266 = maybeParen (ctxt_prec >= pREC_FUN) $
267 sep [pp_header, pprHsType ty]
269 pp_header = case maybe_tvs of
270 Just tvs -> pprHsForAll tvs ctxt
271 Nothing -> pprHsContext ctxt
273 ppr_mono_ty ctxt_prec (HsTyVar name)
276 ppr_mono_ty ctxt_prec (HsFunTy ty1 ty2)
277 = let p1 = ppr_mono_ty pREC_FUN ty1
278 p2 = ppr_mono_ty pREC_TOP ty2
280 maybeParen (ctxt_prec >= pREC_FUN)
281 (sep [p1, (<>) (ptext SLIT("-> ")) p2])
283 ppr_mono_ty ctxt_prec (HsTupleTy con tys) = hsTupParens con (interpp'SP tys)
284 ppr_mono_ty ctxt_prec (HsListTy ty) = brackets (ppr_mono_ty pREC_TOP ty)
286 ppr_mono_ty ctxt_prec (HsAppTy fun_ty arg_ty)
287 = maybeParen (ctxt_prec >= pREC_CON)
288 (hsep [ppr_mono_ty pREC_FUN fun_ty, ppr_mono_ty pREC_CON arg_ty])
290 ppr_mono_ty ctxt_prec (HsPredTy pred)
293 ppr_mono_ty ctxt_prec (HsUsageTy u ty)
294 = maybeParen (ctxt_prec >= pREC_CON)
295 (sep [ptext SLIT("__u") <+> ppr_mono_ty pREC_CON u,
296 ppr_mono_ty pREC_CON ty])
297 -- pREC_FUN would be logical for u, but it yields a reduce/reduce conflict with AppTy
300 ppr_mono_ty ctxt_prec (HsNumTy n) = integer n
301 ppr_mono_ty ctxt_prec (HsOpTy ty1 op ty2) = ppr ty1 <+> ppr op <+> ppr ty2
305 %************************************************************************
307 \subsection{Converting from Type to HsType}
309 %************************************************************************
311 @toHsType@ converts from a Type to a HsType, making the latter look as
312 user-friendly as possible. Notably, it uses synonyms where possible, and
313 expresses overloaded functions using the '=>' context part of a HsForAllTy.
316 toHsTyVar :: TyVar -> HsTyVarBndr Name
317 toHsTyVar tv = IfaceTyVar (getName tv) (tyVarKind tv)
319 toHsTyVars tvs = map toHsTyVar tvs
321 toHsType :: Type -> HsType Name
322 -- This function knows the representation of types
323 toHsType (TyVarTy tv) = HsTyVar (getName tv)
324 toHsType (FunTy arg res) = HsFunTy (toHsType arg) (toHsType res)
325 toHsType (AppTy fun arg) = HsAppTy (toHsType fun) (toHsType arg)
327 toHsType (NoteTy (SynNote ty@(TyConApp tycon tyargs)) real_ty)
328 | isNewTyCon tycon = toHsType ty
329 | syn_matches = toHsType ty -- Use synonyms if possible!!
332 pprTrace "WARNING: synonym info lost in .hi file for " (ppr syn_ty) $
334 toHsType real_ty -- but drop it if not.
336 syn_matches = ty_from_syn `tcEqType` real_ty
337 (tyvars,syn_ty) = getSynTyConDefn tycon
338 ty_from_syn = substTyWith tyvars tyargs syn_ty
340 -- We only use the type synonym in the file if this doesn't cause
341 -- us to lose important information. This matters for usage
342 -- annotations. It's an issue if some of the args to the synonym
343 -- have arrows in them, or if the synonym's RHS has an arrow; for
344 -- example, with nofib/real/ebnf2ps/ in Parsers.using.
346 -- **! It would be nice if when this test fails we could still
347 -- write the synonym in as a Note, so we don't lose the info for
348 -- error messages, but it's too much work for right now.
351 toHsType (NoteTy _ ty) = toHsType ty
353 toHsType (SourceTy (NType tc tys)) = foldl HsAppTy (HsTyVar (getName tc)) (map toHsType tys)
354 toHsType (SourceTy pred) = HsPredTy (toHsPred pred)
356 toHsType ty@(TyConApp tc tys) -- Must be saturated because toHsType's arg is of kind *
357 | not saturated = generic_case
358 | isTupleTyCon tc = HsTupleTy (HsTupCon (getName tc) (tupleTyConBoxity tc) (tyConArity tc)) tys'
359 | tc `hasKey` listTyConKey = HsListTy (head tys')
360 | tc `hasKey` usOnceTyConKey = hsUsOnce_Name -- must print !, . unqualified
361 | tc `hasKey` usManyTyConKey = hsUsMany_Name -- must print !, . unqualified
362 | otherwise = generic_case
364 generic_case = foldl HsAppTy (HsTyVar (getName tc)) tys'
365 tys' = map toHsType tys
366 saturated = tys `lengthIs` tyConArity tc
368 toHsType ty@(ForAllTy _ _) = case tcSplitSigmaTy ty of
369 (tvs, preds, tau) -> HsForAllTy (Just (map toHsTyVar tvs))
373 toHsType (UsageTy u ty) = HsUsageTy (toHsType u) (toHsType ty)
374 -- **! consider dropping usMany annotations ToDo KSW 2000-10
377 toHsPred (ClassP cls tys) = HsClassP (getName cls) (map toHsType tys)
378 toHsPred (IParam n ty) = HsIParam n (toHsType ty)
380 toHsContext :: ThetaType -> HsContext Name
381 toHsContext theta = map toHsPred theta
383 toHsFDs :: [FunDep TyVar] -> [FunDep Name]
384 toHsFDs fds = [(map getName ns, map getName ms) | (ns,ms) <- fds]
388 %************************************************************************
390 \subsection{Comparison}
392 %************************************************************************
395 instance Ord a => Eq (HsType a) where
396 -- The Ord is needed because we keep a
397 -- finite map of variables to variables
398 (==) a b = eq_hsType emptyEqHsEnv a b
400 instance Ord a => Eq (HsPred a) where
401 (==) a b = eq_hsPred emptyEqHsEnv a b
403 eqWithHsTyVars :: Ord name =>
404 [HsTyVarBndr name] -> [HsTyVarBndr name]
405 -> (EqHsEnv name -> Bool) -> Bool
406 eqWithHsTyVars = eq_hsTyVars emptyEqHsEnv
410 type EqHsEnv n = FiniteMap n n
411 -- Tracks the mapping from L-variables to R-variables
413 eq_hsVar :: Ord n => EqHsEnv n -> n -> n -> Bool
414 eq_hsVar env n1 n2 = case lookupFM env n1 of
418 extendEqHsEnv env n1 n2
420 | otherwise = addToFM env n1 n2
422 emptyEqHsEnv :: EqHsEnv n
423 emptyEqHsEnv = emptyFM
426 We do define a specialised equality for these \tr{*Type} types; used
427 in checking interfaces.
431 eq_hsTyVars env [] [] k = k env
432 eq_hsTyVars env (tv1:tvs1) (tv2:tvs2) k = eq_hsTyVar env tv1 tv2 $ \ env ->
433 eq_hsTyVars env tvs1 tvs2 k
434 eq_hsTyVars env _ _ _ = False
436 eq_hsTyVar env (UserTyVar v1) (UserTyVar v2) k = k (extendEqHsEnv env v1 v2)
437 eq_hsTyVar env (IfaceTyVar v1 k1) (IfaceTyVar v2 k2) k = k1 `eqKind` k2 && k (extendEqHsEnv env v1 v2)
438 eq_hsTyVar env _ _ _ = False
440 eq_hsVars env [] [] k = k env
441 eq_hsVars env (v1:bs1) (v2:bs2) k = eq_hsVars (extendEqHsEnv env v1 v2) bs1 bs2 k
442 eq_hsVars env _ _ _ = False
447 eq_hsTypes env = eqListBy (eq_hsType env)
450 eq_hsType env (HsForAllTy tvs1 c1 t1) (HsForAllTy tvs2 c2 t2)
451 = eq_tvs tvs1 tvs2 $ \env ->
452 eq_hsContext env c1 c2 &&
455 eq_tvs Nothing (Just _) k = False
456 eq_tvs Nothing Nothing k = k env
457 eq_tvs (Just _) Nothing k = False
458 eq_tvs (Just tvs1) (Just tvs2) k = eq_hsTyVars env tvs1 tvs2 k
460 eq_hsType env (HsTyVar n1) (HsTyVar n2)
463 eq_hsType env (HsTupleTy c1 tys1) (HsTupleTy c2 tys2)
464 = (c1 == c2) && eq_hsTypes env tys1 tys2
466 eq_hsType env (HsListTy ty1) (HsListTy ty2)
467 = eq_hsType env ty1 ty2
469 eq_hsType env (HsAppTy fun_ty1 arg_ty1) (HsAppTy fun_ty2 arg_ty2)
470 = eq_hsType env fun_ty1 fun_ty2 && eq_hsType env arg_ty1 arg_ty2
472 eq_hsType env (HsFunTy a1 b1) (HsFunTy a2 b2)
473 = eq_hsType env a1 a2 && eq_hsType env b1 b2
475 eq_hsType env (HsPredTy p1) (HsPredTy p2)
476 = eq_hsPred env p1 p2
478 eq_hsType env (HsUsageTy u1 ty1) (HsUsageTy u2 ty2)
479 = eq_hsType env u1 u2 && eq_hsType env ty1 ty2
481 eq_hsType env (HsOpTy lty1 op1 rty1) (HsOpTy lty2 op2 rty2)
482 = eq_hsVar env op1 op2 && eq_hsType env lty1 lty2 && eq_hsType env rty1 rty2
484 eq_hsType env ty1 ty2 = False
488 eq_hsContext env a b = eqListBy (eq_hsPred env) a b
491 eq_hsPred env (HsClassP c1 tys1) (HsClassP c2 tys2)
492 = c1 == c2 && eq_hsTypes env tys1 tys2
493 eq_hsPred env (HsIParam n1 ty1) (HsIParam n2 ty2)
494 = n1 == n2 && eq_hsType env ty1 ty2
495 eq_hsPred env _ _ = False