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)
125 -- Parenthesis preserved for the precedence re-arrangement in RnTypes
126 -- It's important that a * (b + c) doesn't get rearranged to (a*b) + c!
128 -- However, NB that toHsType doesn't add HsParTys (in an effort to keep
129 -- interface files smaller), so when printing a HsType we may need to
132 | HsNumTy Integer -- Generics only
134 -- these next two are only used in interfaces
135 | HsPredTy (HsPred name)
137 | HsKindSig (HsType name) -- (ty :: kind)
138 Kind -- A type with a kind signature
141 data HsTyOp name = HsArrow | HsTyOp name
142 -- Function arrows from *source* get read in as HsOpTy t1 HsArrow t2
143 -- But when we generate or parse interface files, we use HsFunTy.
144 -- This keeps interfaces a bit smaller, because there are a lot of arrows
146 -----------------------
147 hsUsOnce, hsUsMany :: HsType RdrName
148 hsUsOnce = HsTyVar (mkUnqual tvName FSLIT(".")) -- deep magic
149 hsUsMany = HsTyVar (mkUnqual tvName FSLIT("!")) -- deep magic
151 hsUsOnce_Name, hsUsMany_Name :: HsType Name
152 hsUsOnce_Name = HsTyVar usOnceTyConName
153 hsUsMany_Name = HsTyVar usManyTyConName
155 -----------------------
156 data HsTupCon name = HsTupCon name Boxity Arity
158 instance Eq name => Eq (HsTupCon name) where
159 (HsTupCon _ b1 a1) == (HsTupCon _ b2 a2) = b1==b2 && a1==a2
161 mkHsTupCon :: NameSpace -> Boxity -> [a] -> HsTupCon RdrName
162 mkHsTupCon space boxity args = HsTupCon (mkTupConRdrName space boxity arity) boxity arity
166 hsTupParens :: HsTupCon name -> SDoc -> SDoc
167 hsTupParens (HsTupCon _ b _) p = tupleParens b p
169 -----------------------
170 -- Combine adjacent for-alls.
171 -- The following awkward situation can happen otherwise:
172 -- f :: forall a. ((Num a) => Int)
173 -- might generate HsForAll (Just [a]) [] (HsForAll Nothing [Num a] t)
174 -- Then a isn't discovered as ambiguous, and we abstract the AbsBinds wrt []
175 -- but the export list abstracts f wrt [a]. Disaster.
177 -- A valid type must have one for-all at the top of the type, or of the fn arg types
179 mkHsForAllTy mtvs [] ty = mk_forall_ty mtvs ty
180 mkHsForAllTy mtvs ctxt ty = HsForAllTy mtvs ctxt ty
182 -- mk_forall_ty makes a pure for-all type (no context)
183 mk_forall_ty (Just []) ty = ty -- Explicit for-all with no tyvars
184 mk_forall_ty mtvs1 (HsParTy ty) = mk_forall_ty mtvs1 ty
185 mk_forall_ty mtvs1 (HsForAllTy mtvs2 ctxt ty) = mkHsForAllTy (mtvs1 `plus` mtvs2) ctxt ty
186 mk_forall_ty mtvs1 ty = HsForAllTy mtvs1 [] ty
188 mtvs1 `plus` Nothing = mtvs1
189 Nothing `plus` mtvs2 = mtvs2
190 (Just tvs1) `plus` (Just tvs2) = Just (tvs1 ++ tvs2)
192 mkHsDictTy cls tys = HsPredTy (HsClassP cls tys)
193 mkHsIParamTy v ty = HsPredTy (HsIParam v ty)
195 data HsTyVarBndr name
197 | IfaceTyVar name Kind
198 -- *** NOTA BENE *** A "monotype" in a pragma can have
199 -- for-alls in it, (mostly to do with dictionaries). These
200 -- must be explicitly Kinded.
202 hsTyVarName (UserTyVar n) = n
203 hsTyVarName (IfaceTyVar n _) = n
205 hsTyVarNames tvs = map hsTyVarName tvs
207 replaceTyVarName :: HsTyVarBndr name1 -> name2 -> HsTyVarBndr name2
208 replaceTyVarName (UserTyVar n) n' = UserTyVar n'
209 replaceTyVarName (IfaceTyVar n k) n' = IfaceTyVar n' k
214 getHsInstHead :: HsType name -> ([HsTyVarBndr name], (name, [HsType name]))
215 -- Split up an instance decl type, returning the 'head' part
217 -- In interface fiels, the type of the decl is held like this:
218 -- forall a. Foo a -> Baz (T a)
219 -- so we have to strip off function argument types,
220 -- as well as the bit before the '=>' (which is always
221 -- empty in interface files)
223 -- The parser ensures the type will have the right shape.
224 -- (e.g. see ParseUtil.checkInstType)
226 getHsInstHead (HsForAllTy (Just tvs) _ tau) = (tvs, get_head1 tau)
227 getHsInstHead tau = ([], get_head1 tau)
229 get_head1 (HsFunTy _ ty) = get_head1 ty
230 get_head1 (HsPredTy (HsClassP cls tys)) = (cls,tys)
234 %************************************************************************
236 \subsection{Pretty printing}
238 %************************************************************************
240 NB: these types get printed into interface files, so
241 don't change the printing format lightly
244 instance (Outputable name) => Outputable (HsType name) where
245 ppr ty = pprHsType ty
247 instance (Outputable name) => Outputable (HsTyOp name) where
248 ppr HsArrow = ftext FSLIT("->")
249 ppr (HsTyOp n) = ppr n
251 instance (Outputable name) => Outputable (HsTyVarBndr name) where
252 ppr (UserTyVar name) = ppr name
253 ppr (IfaceTyVar name kind) = pprHsTyVarBndr name kind
255 instance Outputable name => Outputable (HsPred name) where
256 ppr (HsClassP clas tys) = ppr clas <+> hsep (map pprParendHsType tys)
257 ppr (HsIParam n ty) = hsep [ppr n, dcolon, ppr ty]
259 pprHsTyVarBndr :: Outputable name => name -> Kind -> SDoc
260 pprHsTyVarBndr name kind | kind `eqKind` liftedTypeKind = ppr name
261 | otherwise = hsep [ppr name, dcolon, pprParendKind kind]
263 pprHsForAll [] [] = empty
265 -- This printer is used for both interface files and
266 -- printing user types in error messages; and alas the
267 -- two use slightly different syntax. Ah well.
268 = getPprStyle $ \ sty ->
269 if userStyle sty then
270 ptext SLIT("forall") <+> interppSP tvs <> dot <+>
271 -- **! ToDo: want to hide uvars from user, but not enough info
272 -- in a HsTyVarBndr name (see PprType). KSW 2000-10.
274 else -- Used in interfaces
275 ptext SLIT("__forall") <+> interppSP tvs <+>
276 ppr_hs_context cxt <+> ptext SLIT("=>")
278 pprHsContext :: (Outputable name) => HsContext name -> SDoc
279 pprHsContext [] = empty
280 pprHsContext cxt = ppr_hs_context cxt <+> ptext SLIT("=>")
282 ppr_hs_context [] = empty
283 ppr_hs_context cxt = parens (interpp'SP cxt)
287 pREC_TOP = (0 :: Int) -- type in ParseIface.y
288 pREC_FUN = (1 :: Int) -- btype in ParseIface.y
289 -- Used for LH arg of (->)
290 pREC_OP = (2 :: Int) -- Used for arg of any infix operator
291 -- (we don't keep their fixities around)
292 pREC_CON = (3 :: Int) -- Used for arg of type applicn:
293 -- always parenthesise unless atomic
295 maybeParen :: Int -- Precedence of context
296 -> Int -- Precedence of top-level operator
297 -> SDoc -> SDoc -- Wrap in parens if (ctxt >= op)
298 maybeParen ctxt_prec op_prec p | ctxt_prec >= op_prec = parens p
301 -- printing works more-or-less as for Types
303 pprHsType, pprParendHsType :: (Outputable name) => HsType name -> SDoc
305 pprHsType ty = ppr_mono_ty pREC_TOP ty
306 pprParendHsType ty = ppr_mono_ty pREC_CON ty
308 ppr_mono_ty ctxt_prec (HsForAllTy maybe_tvs ctxt ty)
309 = maybeParen ctxt_prec pREC_FUN $
310 sep [pp_header, pprHsType ty]
312 pp_header = case maybe_tvs of
313 Just tvs -> pprHsForAll tvs ctxt
314 Nothing -> pprHsContext ctxt
316 ppr_mono_ty ctxt_prec (HsTyVar name) = ppr name
317 ppr_mono_ty ctxt_prec (HsFunTy ty1 ty2) = ppr_fun_ty ctxt_prec ty1 ty2
318 ppr_mono_ty ctxt_prec (HsTupleTy con tys) = hsTupParens con (interpp'SP tys)
319 ppr_mono_ty ctxt_prec (HsKindSig ty kind) = parens (ppr_mono_ty pREC_TOP ty <+> dcolon <+> pprKind kind)
320 ppr_mono_ty ctxt_prec (HsListTy ty) = brackets (ppr_mono_ty pREC_TOP ty)
321 ppr_mono_ty ctxt_prec (HsPArrTy ty) = pabrackets (ppr_mono_ty pREC_TOP ty)
322 ppr_mono_ty ctxt_prec (HsPredTy pred) = braces (ppr pred)
323 ppr_mono_ty ctxt_prec (HsNumTy n) = integer n -- generics only
325 ppr_mono_ty ctxt_prec (HsAppTy fun_ty arg_ty)
326 = maybeParen ctxt_prec pREC_CON $
327 hsep [ppr_mono_ty pREC_FUN fun_ty, ppr_mono_ty pREC_CON arg_ty]
329 ppr_mono_ty ctxt_prec (HsOpTy ty1 HsArrow ty2)
330 = ppr_fun_ty ctxt_prec ty1 ty2
332 ppr_mono_ty ctxt_prec (HsOpTy ty1 op ty2)
333 = maybeParen ctxt_prec pREC_OP $
334 ppr_mono_ty pREC_OP ty1 <+> ppr op <+> ppr_mono_ty pREC_OP ty2
336 ppr_mono_ty ctxt_prec (HsParTy ty)
337 = parens (ppr_mono_ty pREC_TOP ty)
338 -- Put the parens in where the user did
339 -- But we still use the precedence stuff to add parens because
340 -- toHsType doesn't put in any HsParTys, so we may still need them
342 --------------------------
343 ppr_fun_ty ctxt_prec ty1 ty2
344 = let p1 = ppr_mono_ty pREC_FUN ty1
345 p2 = ppr_mono_ty pREC_TOP ty2
347 maybeParen ctxt_prec pREC_FUN $
348 sep [p1, ptext SLIT("->") <+> p2]
350 --------------------------
351 pabrackets p = ptext SLIT("[:") <> p <> ptext SLIT(":]")
355 %************************************************************************
357 \subsection{Converting from Type to HsType}
359 %************************************************************************
361 @toHsType@ converts from a Type to a HsType, making the latter look as
362 user-friendly as possible. Notably, it uses synonyms where possible, and
363 expresses overloaded functions using the '=>' context part of a HsForAllTy.
366 toHsTyVar :: TyVar -> HsTyVarBndr Name
367 toHsTyVar tv = IfaceTyVar (getName tv) (tyVarKind tv)
369 toHsTyVars tvs = map toHsTyVar tvs
371 toHsType :: Type -> HsType Name
372 -- This function knows the representation of types
373 toHsType (TyVarTy tv) = HsTyVar (getName tv)
374 toHsType (FunTy arg res) = HsFunTy (toHsType arg) (toHsType res)
375 toHsType (AppTy fun arg) = HsAppTy (toHsType fun) (toHsType arg)
377 toHsType (NoteTy (SynNote ty@(TyConApp tycon tyargs)) real_ty)
378 | isNewTyCon tycon = toHsType ty
379 | syn_matches = toHsType ty -- Use synonyms if possible!!
382 pprTrace "WARNING: synonym info lost in .hi file for " (ppr syn_ty) $
384 toHsType real_ty -- but drop it if not.
386 syn_matches = ty_from_syn `tcEqType` real_ty
387 (tyvars,syn_ty) = getSynTyConDefn tycon
388 ty_from_syn = substTyWith tyvars tyargs syn_ty
390 -- We only use the type synonym in the file if this doesn't cause
391 -- us to lose important information. This matters for usage
392 -- annotations. It's an issue if some of the args to the synonym
393 -- have arrows in them, or if the synonym's RHS has an arrow; for
394 -- example, with nofib/real/ebnf2ps/ in Parsers.using.
396 -- **! It would be nice if when this test fails we could still
397 -- write the synonym in as a Note, so we don't lose the info for
398 -- error messages, but it's too much work for right now.
401 toHsType (NoteTy _ ty) = toHsType ty
403 toHsType (SourceTy (NType tc tys)) = foldl HsAppTy (HsTyVar (getName tc)) (map toHsType tys)
404 toHsType (SourceTy pred) = HsPredTy (toHsPred pred)
406 toHsType ty@(TyConApp tc tys) -- Must be saturated because toHsType's arg is of kind *
407 | not saturated = generic_case
408 | isTupleTyCon tc = HsTupleTy (HsTupCon (getName tc) (tupleTyConBoxity tc) (tyConArity tc)) tys'
409 | tc `hasKey` listTyConKey = HsListTy (head tys')
410 | tc `hasKey` parrTyConKey = HsPArrTy (head tys')
411 | tc `hasKey` usOnceTyConKey = hsUsOnce_Name -- must print !, . unqualified
412 | tc `hasKey` usManyTyConKey = hsUsMany_Name -- must print !, . unqualified
413 | otherwise = generic_case
415 generic_case = foldl HsAppTy (HsTyVar (getName tc)) tys'
416 tys' = map toHsType tys
417 saturated = tys `lengthIs` tyConArity tc
419 toHsType ty@(ForAllTy _ _) = case tcSplitSigmaTy ty of
420 (tvs, preds, tau) -> HsForAllTy (Just (map toHsTyVar tvs))
424 toHsPred (ClassP cls tys) = HsClassP (getName cls) (map toHsType tys)
425 toHsPred (IParam n ty) = HsIParam n (toHsType ty)
427 toHsContext :: ThetaType -> HsContext Name
428 toHsContext theta = map toHsPred theta
430 toHsFDs :: [FunDep TyVar] -> [FunDep Name]
431 toHsFDs fds = [(map getName ns, map getName ms) | (ns,ms) <- fds]
435 %************************************************************************
437 \subsection{Comparison}
439 %************************************************************************
442 instance Ord a => Eq (HsType a) where
443 -- The Ord is needed because we keep a
444 -- finite map of variables to variables
445 (==) a b = eq_hsType emptyEqHsEnv a b
447 instance Ord a => Eq (HsPred a) where
448 (==) a b = eq_hsPred emptyEqHsEnv a b
450 eqWithHsTyVars :: Ord name =>
451 [HsTyVarBndr name] -> [HsTyVarBndr name]
452 -> (EqHsEnv name -> Bool) -> Bool
453 eqWithHsTyVars = eq_hsTyVars emptyEqHsEnv
457 type EqHsEnv n = FiniteMap n n
458 -- Tracks the mapping from L-variables to R-variables
460 eq_hsVar :: Ord n => EqHsEnv n -> n -> n -> Bool
461 eq_hsVar env n1 n2 = case lookupFM env n1 of
465 extendEqHsEnv env n1 n2
467 | otherwise = addToFM env n1 n2
469 emptyEqHsEnv :: EqHsEnv n
470 emptyEqHsEnv = emptyFM
473 We do define a specialised equality for these \tr{*Type} types; used
474 in checking interfaces.
478 eq_hsTyVars env [] [] k = k env
479 eq_hsTyVars env (tv1:tvs1) (tv2:tvs2) k = eq_hsTyVar env tv1 tv2 $ \ env ->
480 eq_hsTyVars env tvs1 tvs2 k
481 eq_hsTyVars env _ _ _ = False
483 eq_hsTyVar env (UserTyVar v1) (UserTyVar v2) k = k (extendEqHsEnv env v1 v2)
484 eq_hsTyVar env (IfaceTyVar v1 k1) (IfaceTyVar v2 k2) k = k1 `eqKind` k2 && k (extendEqHsEnv env v1 v2)
485 eq_hsTyVar env _ _ _ = False
487 eq_hsVars env [] [] k = k env
488 eq_hsVars env (v1:bs1) (v2:bs2) k = eq_hsVars (extendEqHsEnv env v1 v2) bs1 bs2 k
489 eq_hsVars env _ _ _ = False
494 eq_hsTypes env = eqListBy (eq_hsType env)
497 eq_hsType env (HsForAllTy tvs1 c1 t1) (HsForAllTy tvs2 c2 t2)
498 = eq_tvs tvs1 tvs2 $ \env ->
499 eq_hsContext env c1 c2 &&
502 eq_tvs Nothing (Just _) k = False
503 eq_tvs Nothing Nothing k = k env
504 eq_tvs (Just _) Nothing k = False
505 eq_tvs (Just tvs1) (Just tvs2) k = eq_hsTyVars env tvs1 tvs2 k
507 eq_hsType env (HsTyVar n1) (HsTyVar n2)
510 eq_hsType env (HsTupleTy c1 tys1) (HsTupleTy c2 tys2)
511 = (c1 == c2) && eq_hsTypes env tys1 tys2
513 eq_hsType env (HsListTy ty1) (HsListTy ty2)
514 = eq_hsType env ty1 ty2
516 eq_hsType env (HsKindSig ty1 k1) (HsKindSig ty2 k2)
517 = eq_hsType env ty1 ty2 && k1 `eqKind` k2
519 eq_hsType env (HsPArrTy ty1) (HsPArrTy ty2)
520 = eq_hsType env ty1 ty2
522 eq_hsType env (HsAppTy fun_ty1 arg_ty1) (HsAppTy fun_ty2 arg_ty2)
523 = eq_hsType env fun_ty1 fun_ty2 && eq_hsType env arg_ty1 arg_ty2
525 eq_hsType env (HsFunTy a1 b1) (HsFunTy a2 b2)
526 = eq_hsType env a1 a2 && eq_hsType env b1 b2
528 eq_hsType env (HsPredTy p1) (HsPredTy p2)
529 = eq_hsPred env p1 p2
531 eq_hsType env (HsOpTy lty1 op1 rty1) (HsOpTy lty2 op2 rty2)
532 = eq_hsOp env op1 op2 && eq_hsType env lty1 lty2 && eq_hsType env rty1 rty2
534 eq_hsType env ty1 ty2 = False
537 eq_hsOp env (HsTyOp n1) (HsTyOp n2) = eq_hsVar env n1 n2
538 eq_hsOp env HsArrow HsArrow = True
539 eq_hsOp env op1 op2 = False
542 eq_hsContext env a b = eqListBy (eq_hsPred env) a b
545 eq_hsPred env (HsClassP c1 tys1) (HsClassP c2 tys2)
546 = c1 == c2 && eq_hsTypes env tys1 tys2
547 eq_hsPred env (HsIParam n1 ty1) (HsIParam n2 ty2)
548 = n1 == n2 && eq_hsType env ty1 ty2
549 eq_hsPred env _ _ = False