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 mtvs [] ty = mk_forall_ty mtvs ty
176 mkHsForAllTy mtvs ctxt ty = HsForAllTy mtvs ctxt ty
178 -- mk_forall_ty makes a pure for-all type (no context)
179 mk_forall_ty (Just []) ty = ty -- Explicit for-all with no tyvars
180 mk_forall_ty mtvs1 (HsParTy ty) = mk_forall_ty mtvs1 ty
181 mk_forall_ty mtvs1 (HsForAllTy mtvs2 ctxt ty) = mkHsForAllTy (mtvs1 `plus` mtvs2) ctxt ty
182 mk_forall_ty mtvs1 ty = HsForAllTy mtvs1 [] ty
184 mtvs1 `plus` Nothing = mtvs1
185 Nothing `plus` mtvs2 = mtvs2
186 (Just tvs1) `plus` (Just tvs2) = Just (tvs1 ++ tvs2)
188 mkHsDictTy cls tys = HsPredTy (HsClassP cls tys)
189 mkHsIParamTy v ty = HsPredTy (HsIParam v ty)
191 data HsTyVarBndr name
193 | IfaceTyVar name Kind
194 -- *** NOTA BENE *** A "monotype" in a pragma can have
195 -- for-alls in it, (mostly to do with dictionaries). These
196 -- must be explicitly Kinded.
198 hsTyVarName (UserTyVar n) = n
199 hsTyVarName (IfaceTyVar n _) = n
201 hsTyVarNames tvs = map hsTyVarName tvs
203 replaceTyVarName :: HsTyVarBndr name1 -> name2 -> HsTyVarBndr name2
204 replaceTyVarName (UserTyVar n) n' = UserTyVar n'
205 replaceTyVarName (IfaceTyVar n k) n' = IfaceTyVar n' k
210 getHsInstHead :: HsType name -> ([HsTyVarBndr name], (name, [HsType name]))
211 -- Split up an instance decl type, returning the 'head' part
213 -- In interface fiels, the type of the decl is held like this:
214 -- forall a. Foo a -> Baz (T a)
215 -- so we have to strip off function argument types,
216 -- as well as the bit before the '=>' (which is always
217 -- empty in interface files)
219 -- The parser ensures the type will have the right shape.
220 -- (e.g. see ParseUtil.checkInstType)
222 getHsInstHead (HsForAllTy (Just tvs) _ tau) = (tvs, get_head1 tau)
223 getHsInstHead tau = ([], get_head1 tau)
225 get_head1 (HsFunTy _ ty) = get_head1 ty
226 get_head1 (HsPredTy (HsClassP cls tys)) = (cls,tys)
230 %************************************************************************
232 \subsection{Pretty printing}
234 %************************************************************************
236 NB: these types get printed into interface files, so
237 don't change the printing format lightly
240 instance (Outputable name) => Outputable (HsType name) where
241 ppr ty = pprHsType ty
243 instance (Outputable name) => Outputable (HsTyOp name) where
244 ppr HsArrow = ftext FSLIT("->")
245 ppr (HsTyOp n) = ppr n
247 instance (Outputable name) => Outputable (HsTyVarBndr name) where
248 ppr (UserTyVar name) = ppr name
249 ppr (IfaceTyVar name kind) = pprHsTyVarBndr name kind
251 instance Outputable name => Outputable (HsPred name) where
252 ppr (HsClassP clas tys) = ppr clas <+> hsep (map pprParendHsType tys)
253 ppr (HsIParam n ty) = hsep [ppr n, dcolon, ppr ty]
255 pprHsTyVarBndr :: Outputable name => name -> Kind -> SDoc
256 pprHsTyVarBndr name kind | kind `eqKind` liftedTypeKind = ppr name
257 | otherwise = hsep [ppr name, dcolon, pprParendKind kind]
259 pprHsForAll [] [] = empty
261 -- This printer is used for both interface files and
262 -- printing user types in error messages; and alas the
263 -- two use slightly different syntax. Ah well.
264 = getPprStyle $ \ sty ->
265 if userStyle sty then
266 ptext SLIT("forall") <+> interppSP tvs <> dot <+>
267 -- **! ToDo: want to hide uvars from user, but not enough info
268 -- in a HsTyVarBndr name (see PprType). KSW 2000-10.
270 else -- Used in interfaces
271 ptext SLIT("__forall") <+> interppSP tvs <+>
272 ppr_hs_context cxt <+> ptext SLIT("=>")
274 pprHsContext :: (Outputable name) => HsContext name -> SDoc
275 pprHsContext [] = empty
276 pprHsContext cxt = ppr_hs_context cxt <+> ptext SLIT("=>")
278 ppr_hs_context [] = empty
279 ppr_hs_context cxt = parens (interpp'SP cxt)
283 pREC_TOP = (0 :: Int) -- type in ParseIface.y
284 pREC_FUN = (1 :: Int) -- btype in ParseIface.y
285 pREC_CON = (2 :: Int) -- atype in ParseIface.y
287 maybeParen :: Bool -> SDoc -> SDoc
288 maybeParen True p = parens p
289 maybeParen False p = p
291 -- printing works more-or-less as for Types
293 pprHsType, pprParendHsType :: (Outputable name) => HsType name -> SDoc
295 pprHsType ty = ppr_mono_ty pREC_TOP ty
296 pprParendHsType ty = ppr_mono_ty pREC_CON ty
298 ppr_mono_ty ctxt_prec (HsForAllTy maybe_tvs ctxt ty)
299 = maybeParen (ctxt_prec >= pREC_FUN) $
300 sep [pp_header, pprHsType ty]
302 pp_header = case maybe_tvs of
303 Just tvs -> pprHsForAll tvs ctxt
304 Nothing -> pprHsContext ctxt
306 ppr_mono_ty ctxt_prec (HsTyVar name)
309 ppr_mono_ty ctxt_prec (HsFunTy ty1 ty2)
310 = let p1 = ppr_mono_ty pREC_FUN ty1
311 p2 = ppr_mono_ty pREC_TOP ty2
313 maybeParen (ctxt_prec >= pREC_FUN)
314 (sep [p1, ptext SLIT("->") <+> p2])
316 ppr_mono_ty ctxt_prec (HsTupleTy con tys) = hsTupParens con (interpp'SP tys)
317 ppr_mono_ty ctxt_prec (HsKindSig ty kind) = parens (ppr_mono_ty pREC_TOP ty <+> dcolon <+> pprKind kind)
318 ppr_mono_ty ctxt_prec (HsListTy ty) = brackets (ppr_mono_ty pREC_TOP ty)
319 ppr_mono_ty ctxt_prec (HsPArrTy ty) = pabrackets (ppr_mono_ty pREC_TOP ty)
321 pabrackets p = ptext SLIT("[:") <> p <> ptext SLIT(":]")
323 ppr_mono_ty ctxt_prec (HsAppTy fun_ty arg_ty) =
324 maybeParen (ctxt_prec >= pREC_CON)
325 (hsep [ppr_mono_ty pREC_FUN fun_ty, ppr_mono_ty pREC_CON arg_ty])
327 ppr_mono_ty ctxt_prec (HsPredTy pred)
330 ppr_mono_ty ctxt_prec (HsOpTy ty1 op ty2) =
331 maybeParen (ctxt_prec >= pREC_FUN)
332 (ppr_mono_ty pREC_FUN ty1 <+> ppr op <+> ppr_mono_ty pREC_FUN ty2)
334 ppr_mono_ty ctxt_prec (HsParTy ty) = ppr_mono_ty ctxt_prec ty
335 -- `HsParTy' isn't useful for pretty printing, as it is removed by the type
336 -- checker and we need to be able to pretty print after type checking
338 ppr_mono_ty ctxt_prec (HsNumTy n) = integer n -- generics only
342 %************************************************************************
344 \subsection{Converting from Type to HsType}
346 %************************************************************************
348 @toHsType@ converts from a Type to a HsType, making the latter look as
349 user-friendly as possible. Notably, it uses synonyms where possible, and
350 expresses overloaded functions using the '=>' context part of a HsForAllTy.
353 toHsTyVar :: TyVar -> HsTyVarBndr Name
354 toHsTyVar tv = IfaceTyVar (getName tv) (tyVarKind tv)
356 toHsTyVars tvs = map toHsTyVar tvs
358 toHsType :: Type -> HsType Name
359 -- This function knows the representation of types
360 toHsType (TyVarTy tv) = HsTyVar (getName tv)
361 toHsType (FunTy arg res) = HsFunTy (toHsType arg) (toHsType res)
362 toHsType (AppTy fun arg) = HsAppTy (toHsType fun) (toHsType arg)
364 toHsType (NoteTy (SynNote ty@(TyConApp tycon tyargs)) real_ty)
365 | isNewTyCon tycon = toHsType ty
366 | syn_matches = toHsType ty -- Use synonyms if possible!!
369 pprTrace "WARNING: synonym info lost in .hi file for " (ppr syn_ty) $
371 toHsType real_ty -- but drop it if not.
373 syn_matches = ty_from_syn `tcEqType` real_ty
374 (tyvars,syn_ty) = getSynTyConDefn tycon
375 ty_from_syn = substTyWith tyvars tyargs syn_ty
377 -- We only use the type synonym in the file if this doesn't cause
378 -- us to lose important information. This matters for usage
379 -- annotations. It's an issue if some of the args to the synonym
380 -- have arrows in them, or if the synonym's RHS has an arrow; for
381 -- example, with nofib/real/ebnf2ps/ in Parsers.using.
383 -- **! It would be nice if when this test fails we could still
384 -- write the synonym in as a Note, so we don't lose the info for
385 -- error messages, but it's too much work for right now.
388 toHsType (NoteTy _ ty) = toHsType ty
390 toHsType (SourceTy (NType tc tys)) = foldl HsAppTy (HsTyVar (getName tc)) (map toHsType tys)
391 toHsType (SourceTy pred) = HsPredTy (toHsPred pred)
393 toHsType ty@(TyConApp tc tys) -- Must be saturated because toHsType's arg is of kind *
394 | not saturated = generic_case
395 | isTupleTyCon tc = HsTupleTy (HsTupCon (getName tc) (tupleTyConBoxity tc) (tyConArity tc)) tys'
396 | tc `hasKey` listTyConKey = HsListTy (head tys')
397 | tc `hasKey` parrTyConKey = HsPArrTy (head tys')
398 | tc `hasKey` usOnceTyConKey = hsUsOnce_Name -- must print !, . unqualified
399 | tc `hasKey` usManyTyConKey = hsUsMany_Name -- must print !, . unqualified
400 | otherwise = generic_case
402 generic_case = foldl HsAppTy (HsTyVar (getName tc)) tys'
403 tys' = map toHsType tys
404 saturated = tys `lengthIs` tyConArity tc
406 toHsType ty@(ForAllTy _ _) = case tcSplitSigmaTy ty of
407 (tvs, preds, tau) -> HsForAllTy (Just (map toHsTyVar tvs))
411 toHsPred (ClassP cls tys) = HsClassP (getName cls) (map toHsType tys)
412 toHsPred (IParam n ty) = HsIParam n (toHsType ty)
414 toHsContext :: ThetaType -> HsContext Name
415 toHsContext theta = map toHsPred theta
417 toHsFDs :: [FunDep TyVar] -> [FunDep Name]
418 toHsFDs fds = [(map getName ns, map getName ms) | (ns,ms) <- fds]
422 %************************************************************************
424 \subsection{Comparison}
426 %************************************************************************
429 instance Ord a => Eq (HsType a) where
430 -- The Ord is needed because we keep a
431 -- finite map of variables to variables
432 (==) a b = eq_hsType emptyEqHsEnv a b
434 instance Ord a => Eq (HsPred a) where
435 (==) a b = eq_hsPred emptyEqHsEnv a b
437 eqWithHsTyVars :: Ord name =>
438 [HsTyVarBndr name] -> [HsTyVarBndr name]
439 -> (EqHsEnv name -> Bool) -> Bool
440 eqWithHsTyVars = eq_hsTyVars emptyEqHsEnv
444 type EqHsEnv n = FiniteMap n n
445 -- Tracks the mapping from L-variables to R-variables
447 eq_hsVar :: Ord n => EqHsEnv n -> n -> n -> Bool
448 eq_hsVar env n1 n2 = case lookupFM env n1 of
452 extendEqHsEnv env n1 n2
454 | otherwise = addToFM env n1 n2
456 emptyEqHsEnv :: EqHsEnv n
457 emptyEqHsEnv = emptyFM
460 We do define a specialised equality for these \tr{*Type} types; used
461 in checking interfaces.
465 eq_hsTyVars env [] [] k = k env
466 eq_hsTyVars env (tv1:tvs1) (tv2:tvs2) k = eq_hsTyVar env tv1 tv2 $ \ env ->
467 eq_hsTyVars env tvs1 tvs2 k
468 eq_hsTyVars env _ _ _ = False
470 eq_hsTyVar env (UserTyVar v1) (UserTyVar v2) k = k (extendEqHsEnv env v1 v2)
471 eq_hsTyVar env (IfaceTyVar v1 k1) (IfaceTyVar v2 k2) k = k1 `eqKind` k2 && k (extendEqHsEnv env v1 v2)
472 eq_hsTyVar env _ _ _ = False
474 eq_hsVars env [] [] k = k env
475 eq_hsVars env (v1:bs1) (v2:bs2) k = eq_hsVars (extendEqHsEnv env v1 v2) bs1 bs2 k
476 eq_hsVars env _ _ _ = False
481 eq_hsTypes env = eqListBy (eq_hsType env)
484 eq_hsType env (HsForAllTy tvs1 c1 t1) (HsForAllTy tvs2 c2 t2)
485 = eq_tvs tvs1 tvs2 $ \env ->
486 eq_hsContext env c1 c2 &&
489 eq_tvs Nothing (Just _) k = False
490 eq_tvs Nothing Nothing k = k env
491 eq_tvs (Just _) Nothing k = False
492 eq_tvs (Just tvs1) (Just tvs2) k = eq_hsTyVars env tvs1 tvs2 k
494 eq_hsType env (HsTyVar n1) (HsTyVar n2)
497 eq_hsType env (HsTupleTy c1 tys1) (HsTupleTy c2 tys2)
498 = (c1 == c2) && eq_hsTypes env tys1 tys2
500 eq_hsType env (HsListTy ty1) (HsListTy ty2)
501 = eq_hsType env ty1 ty2
503 eq_hsType env (HsKindSig ty1 k1) (HsKindSig ty2 k2)
504 = eq_hsType env ty1 ty2 && k1 `eqKind` k2
506 eq_hsType env (HsPArrTy ty1) (HsPArrTy ty2)
507 = eq_hsType env ty1 ty2
509 eq_hsType env (HsAppTy fun_ty1 arg_ty1) (HsAppTy fun_ty2 arg_ty2)
510 = eq_hsType env fun_ty1 fun_ty2 && eq_hsType env arg_ty1 arg_ty2
512 eq_hsType env (HsFunTy a1 b1) (HsFunTy a2 b2)
513 = eq_hsType env a1 a2 && eq_hsType env b1 b2
515 eq_hsType env (HsPredTy p1) (HsPredTy p2)
516 = eq_hsPred env p1 p2
518 eq_hsType env (HsOpTy lty1 op1 rty1) (HsOpTy lty2 op2 rty2)
519 = eq_hsOp env op1 op2 && eq_hsType env lty1 lty2 && eq_hsType env rty1 rty2
521 eq_hsType env ty1 ty2 = False
524 eq_hsOp env (HsTyOp n1) (HsTyOp n2) = eq_hsVar env n1 n2
525 eq_hsOp env HsArrow HsArrow = True
526 eq_hsOp env op1 op2 = False
529 eq_hsContext env a b = eqListBy (eq_hsPred env) a b
532 eq_hsPred env (HsClassP c1 tys1) (HsClassP c2 tys2)
533 = c1 == c2 && eq_hsTypes env tys1 tys2
534 eq_hsPred env (HsIParam n1 ty1) (HsIParam n2 ty2)
535 = n1 == n2 && eq_hsType env ty1 ty2
536 eq_hsPred env _ _ = False