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, ppr_hs_context, 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.
233 else -- Used in interfaces
234 ptext SLIT("__forall") <+> interppSP tvs <+>
235 ppr_hs_context cxt <+> ptext SLIT("=>")
237 pprHsContext :: (Outputable name) => HsContext name -> SDoc
238 pprHsContext [] = empty
239 pprHsContext cxt = ppr_hs_context cxt <+> ptext SLIT("=>")
241 ppr_hs_context [] = empty
242 ppr_hs_context cxt = parens (interpp'SP cxt)
246 pREC_TOP = (0 :: Int) -- type in ParseIface.y
247 pREC_FUN = (1 :: Int) -- btype in ParseIface.y
248 pREC_CON = (2 :: Int) -- atype in ParseIface.y
250 maybeParen :: Bool -> SDoc -> SDoc
251 maybeParen True p = parens p
252 maybeParen False p = p
254 -- printing works more-or-less as for Types
256 pprHsType, pprParendHsType :: (Outputable name) => HsType name -> SDoc
258 pprHsType ty = ppr_mono_ty pREC_TOP ty
259 pprParendHsType ty = ppr_mono_ty pREC_CON ty
261 ppr_mono_ty ctxt_prec (HsForAllTy maybe_tvs ctxt ty)
262 = maybeParen (ctxt_prec >= pREC_FUN) $
263 sep [pp_header, pprHsType ty]
265 pp_header = case maybe_tvs of
266 Just tvs -> pprHsForAll tvs ctxt
267 Nothing -> pprHsContext ctxt
269 ppr_mono_ty ctxt_prec (HsTyVar name)
272 ppr_mono_ty ctxt_prec (HsFunTy ty1 ty2)
273 = let p1 = ppr_mono_ty pREC_FUN ty1
274 p2 = ppr_mono_ty pREC_TOP ty2
276 maybeParen (ctxt_prec >= pREC_FUN)
277 (sep [p1, (<>) (ptext SLIT("-> ")) p2])
279 ppr_mono_ty ctxt_prec (HsTupleTy con tys) = hsTupParens con (interpp'SP tys)
280 ppr_mono_ty ctxt_prec (HsListTy ty) = brackets (ppr_mono_ty pREC_TOP ty)
282 ppr_mono_ty ctxt_prec (HsAppTy fun_ty arg_ty)
283 = maybeParen (ctxt_prec >= pREC_CON)
284 (hsep [ppr_mono_ty pREC_FUN fun_ty, ppr_mono_ty pREC_CON arg_ty])
286 ppr_mono_ty ctxt_prec (HsPredTy pred)
289 ppr_mono_ty ctxt_prec (HsUsageTy u ty)
290 = maybeParen (ctxt_prec >= pREC_CON)
291 (sep [ptext SLIT("__u") <+> ppr_mono_ty pREC_CON u,
292 ppr_mono_ty pREC_CON ty])
293 -- pREC_FUN would be logical for u, but it yields a reduce/reduce conflict with AppTy
296 ppr_mono_ty ctxt_prec (HsNumTy n) = integer n
297 ppr_mono_ty ctxt_prec (HsOpTy ty1 op ty2) = ppr ty1 <+> ppr op <+> ppr ty2
301 %************************************************************************
303 \subsection{Converting from Type to HsType}
305 %************************************************************************
307 @toHsType@ converts from a Type to a HsType, making the latter look as
308 user-friendly as possible. Notably, it uses synonyms where possible, and
309 expresses overloaded functions using the '=>' context part of a HsForAllTy.
312 toHsTyVar :: TyVar -> HsTyVarBndr Name
313 toHsTyVar tv = IfaceTyVar (getName tv) (tyVarKind tv)
315 toHsTyVars tvs = map toHsTyVar tvs
317 toHsType :: Type -> HsType Name
318 -- This function knows the representation of types
319 toHsType (TyVarTy tv) = HsTyVar (getName tv)
320 toHsType (FunTy arg res) = HsFunTy (toHsType arg) (toHsType res)
321 toHsType (AppTy fun arg) = HsAppTy (toHsType fun) (toHsType arg)
323 toHsType (NoteTy (SynNote ty@(TyConApp tycon tyargs)) real_ty)
324 | isNewTyCon tycon = toHsType ty
325 | syn_matches = toHsType ty -- Use synonyms if possible!!
328 pprTrace "WARNING: synonym info lost in .hi file for " (ppr syn_ty) $
330 toHsType real_ty -- but drop it if not.
332 syn_matches = ty_from_syn `tcEqType` real_ty
333 (tyvars,syn_ty) = getSynTyConDefn tycon
334 ty_from_syn = substTyWith tyvars tyargs syn_ty
336 -- We only use the type synonym in the file if this doesn't cause
337 -- us to lose important information. This matters for usage
338 -- annotations. It's an issue if some of the args to the synonym
339 -- have arrows in them, or if the synonym's RHS has an arrow; for
340 -- example, with nofib/real/ebnf2ps/ in Parsers.using.
342 -- **! It would be nice if when this test fails we could still
343 -- write the synonym in as a Note, so we don't lose the info for
344 -- error messages, but it's too much work for right now.
347 toHsType (NoteTy _ ty) = toHsType ty
349 toHsType (SourceTy (NType tc tys)) = foldl HsAppTy (HsTyVar (getName tc)) (map toHsType tys)
350 toHsType (SourceTy pred) = HsPredTy (toHsPred pred)
352 toHsType ty@(TyConApp tc tys) -- Must be saturated because toHsType's arg is of kind *
353 | not saturated = generic_case
354 | isTupleTyCon tc = HsTupleTy (HsTupCon (getName tc) (tupleTyConBoxity tc) (tyConArity tc)) tys'
355 | tc `hasKey` listTyConKey = HsListTy (head tys')
356 | tc `hasKey` usOnceTyConKey = hsUsOnce_Name -- must print !, . unqualified
357 | tc `hasKey` usManyTyConKey = hsUsMany_Name -- must print !, . unqualified
358 | otherwise = generic_case
360 generic_case = foldl HsAppTy (HsTyVar (getName tc)) tys'
361 tys' = map toHsType tys
362 saturated = tys `lengthIs` tyConArity tc
364 toHsType ty@(ForAllTy _ _) = case tcSplitSigmaTy ty of
365 (tvs, preds, tau) -> HsForAllTy (Just (map toHsTyVar tvs))
369 toHsType (UsageTy u ty) = HsUsageTy (toHsType u) (toHsType ty)
370 -- **! consider dropping usMany annotations ToDo KSW 2000-10
373 toHsPred (ClassP cls tys) = HsClassP (getName cls) (map toHsType tys)
374 toHsPred (IParam n ty) = HsIParam n (toHsType ty)
376 toHsContext :: ThetaType -> HsContext Name
377 toHsContext theta = map toHsPred theta
379 toHsFDs :: [FunDep TyVar] -> [FunDep Name]
380 toHsFDs fds = [(map getName ns, map getName ms) | (ns,ms) <- fds]
384 %************************************************************************
386 \subsection{Comparison}
388 %************************************************************************
391 instance Ord a => Eq (HsType a) where
392 -- The Ord is needed because we keep a
393 -- finite map of variables to variables
394 (==) a b = eq_hsType emptyEqHsEnv a b
396 instance Ord a => Eq (HsPred a) where
397 (==) a b = eq_hsPred emptyEqHsEnv a b
399 eqWithHsTyVars :: Ord name =>
400 [HsTyVarBndr name] -> [HsTyVarBndr name]
401 -> (EqHsEnv name -> Bool) -> Bool
402 eqWithHsTyVars = eq_hsTyVars emptyEqHsEnv
406 type EqHsEnv n = FiniteMap n n
407 -- Tracks the mapping from L-variables to R-variables
409 eq_hsVar :: Ord n => EqHsEnv n -> n -> n -> Bool
410 eq_hsVar env n1 n2 = case lookupFM env n1 of
414 extendEqHsEnv env n1 n2
416 | otherwise = addToFM env n1 n2
418 emptyEqHsEnv :: EqHsEnv n
419 emptyEqHsEnv = emptyFM
422 We do define a specialised equality for these \tr{*Type} types; used
423 in checking interfaces.
427 eq_hsTyVars env [] [] k = k env
428 eq_hsTyVars env (tv1:tvs1) (tv2:tvs2) k = eq_hsTyVar env tv1 tv2 $ \ env ->
429 eq_hsTyVars env tvs1 tvs2 k
430 eq_hsTyVars env _ _ _ = False
432 eq_hsTyVar env (UserTyVar v1) (UserTyVar v2) k = k (extendEqHsEnv env v1 v2)
433 eq_hsTyVar env (IfaceTyVar v1 k1) (IfaceTyVar v2 k2) k = k1 `eqKind` k2 && k (extendEqHsEnv env v1 v2)
434 eq_hsTyVar env _ _ _ = False
436 eq_hsVars env [] [] k = k env
437 eq_hsVars env (v1:bs1) (v2:bs2) k = eq_hsVars (extendEqHsEnv env v1 v2) bs1 bs2 k
438 eq_hsVars env _ _ _ = False
443 eq_hsTypes env = eqListBy (eq_hsType env)
446 eq_hsType env (HsForAllTy tvs1 c1 t1) (HsForAllTy tvs2 c2 t2)
447 = eq_tvs tvs1 tvs2 $ \env ->
448 eq_hsContext env c1 c2 &&
451 eq_tvs Nothing (Just _) k = False
452 eq_tvs Nothing Nothing k = k env
453 eq_tvs (Just _) Nothing k = False
454 eq_tvs (Just tvs1) (Just tvs2) k = eq_hsTyVars env tvs1 tvs2 k
456 eq_hsType env (HsTyVar n1) (HsTyVar n2)
459 eq_hsType env (HsTupleTy c1 tys1) (HsTupleTy c2 tys2)
460 = (c1 == c2) && eq_hsTypes env tys1 tys2
462 eq_hsType env (HsListTy ty1) (HsListTy ty2)
463 = eq_hsType env ty1 ty2
465 eq_hsType env (HsAppTy fun_ty1 arg_ty1) (HsAppTy fun_ty2 arg_ty2)
466 = eq_hsType env fun_ty1 fun_ty2 && eq_hsType env arg_ty1 arg_ty2
468 eq_hsType env (HsFunTy a1 b1) (HsFunTy a2 b2)
469 = eq_hsType env a1 a2 && eq_hsType env b1 b2
471 eq_hsType env (HsPredTy p1) (HsPredTy p2)
472 = eq_hsPred env p1 p2
474 eq_hsType env (HsUsageTy u1 ty1) (HsUsageTy u2 ty2)
475 = eq_hsType env u1 u2 && eq_hsType env ty1 ty2
477 eq_hsType env (HsOpTy lty1 op1 rty1) (HsOpTy lty2 op2 rty2)
478 = eq_hsVar env op1 op2 && eq_hsType env lty1 lty2 && eq_hsType env rty1 rty2
480 eq_hsType env ty1 ty2 = False
484 eq_hsContext env a b = eqListBy (eq_hsPred env) a b
487 eq_hsPred env (HsClassP c1 tys1) (HsClassP c2 tys2)
488 = c1 == c2 && eq_hsTypes env tys1 tys2
489 eq_hsPred env (HsIParam n1 ty1) (HsIParam n2 ty2)
490 = n1 == n2 && eq_hsType env ty1 ty2
491 eq_hsPred env _ _ = False