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 , 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, pprKind )
45 import BasicTypes ( Boxity(..), Arity, IPName, tupleParens )
46 import PrelNames ( mkTupConRdrName, listTyConKey, parrTyConKey,
47 usOnceTyConKey, usManyTyConKey, hasKey,
48 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 | HsPArrTy (HsType name) -- Elem. type of parallel array: [:t:]
103 | HsTupleTy (HsTupCon name)
104 [HsType name] -- Element types (length gives arity)
106 | HsOpTy (HsType name) (HsTyOp name) (HsType name)
107 | HsNumTy Integer -- Generics only
109 -- these next two are only used in interfaces
110 | HsPredTy (HsPred name)
112 | HsKindSig (HsType name) -- (ty :: kind)
113 Kind -- A type with a kind signature
116 data HsTyOp name = HsArrow | HsTyOp name
117 -- Function arrows from *source* get read in as HsOpTy t1 HsArrow t2
118 -- But when we generate or parse interface files, we use HsFunTy.
119 -- This keeps interfaces a bit smaller, because there are a lot of arrows
121 -----------------------
122 hsUsOnce, hsUsMany :: HsType RdrName
123 hsUsOnce = HsTyVar (mkUnqual tvName FSLIT(".")) -- deep magic
124 hsUsMany = HsTyVar (mkUnqual tvName FSLIT("!")) -- deep magic
126 hsUsOnce_Name, hsUsMany_Name :: HsType Name
127 hsUsOnce_Name = HsTyVar usOnceTyConName
128 hsUsMany_Name = HsTyVar usManyTyConName
130 -----------------------
131 data HsTupCon name = HsTupCon name Boxity Arity
133 instance Eq name => Eq (HsTupCon name) where
134 (HsTupCon _ b1 a1) == (HsTupCon _ b2 a2) = b1==b2 && a1==a2
136 mkHsTupCon :: NameSpace -> Boxity -> [a] -> HsTupCon RdrName
137 mkHsTupCon space boxity args = HsTupCon (mkTupConRdrName space boxity arity) boxity arity
141 hsTupParens :: HsTupCon name -> SDoc -> SDoc
142 hsTupParens (HsTupCon _ b _) p = tupleParens b p
144 -----------------------
145 -- Combine adjacent for-alls.
146 -- The following awkward situation can happen otherwise:
147 -- f :: forall a. ((Num a) => Int)
148 -- might generate HsForAll (Just [a]) [] (HsForAll Nothing [Num a] t)
149 -- Then a isn't discovered as ambiguous, and we abstract the AbsBinds wrt []
150 -- but the export list abstracts f wrt [a]. Disaster.
152 -- A valid type must have one for-all at the top of the type, or of the fn arg types
154 mkHsForAllTy (Just []) [] ty = ty -- Explicit for-all with no tyvars
155 mkHsForAllTy mtvs1 [] (HsForAllTy mtvs2 ctxt ty) = mkHsForAllTy (mtvs1 `plus` mtvs2) ctxt ty
157 mtvs1 `plus` Nothing = mtvs1
158 Nothing `plus` mtvs2 = mtvs2
159 (Just tvs1) `plus` (Just tvs2) = Just (tvs1 ++ tvs2)
160 mkHsForAllTy tvs ctxt ty = HsForAllTy tvs ctxt ty
162 mkHsDictTy cls tys = HsPredTy (HsClassP cls tys)
163 mkHsIParamTy v ty = HsPredTy (HsIParam v ty)
165 data HsTyVarBndr name
167 | IfaceTyVar name Kind
168 -- *** NOTA BENE *** A "monotype" in a pragma can have
169 -- for-alls in it, (mostly to do with dictionaries). These
170 -- must be explicitly Kinded.
172 hsTyVarName (UserTyVar n) = n
173 hsTyVarName (IfaceTyVar n _) = n
175 hsTyVarNames tvs = map hsTyVarName tvs
177 replaceTyVarName :: HsTyVarBndr name1 -> name2 -> HsTyVarBndr name2
178 replaceTyVarName (UserTyVar n) n' = UserTyVar n'
179 replaceTyVarName (IfaceTyVar n k) n' = IfaceTyVar n' k
184 getHsInstHead :: HsType name -> ([HsTyVarBndr name], (name, [HsType name]))
185 -- Split up an instance decl type, returning the 'head' part
187 -- In interface fiels, the type of the decl is held like this:
188 -- forall a. Foo a -> Baz (T a)
189 -- so we have to strip off function argument types,
190 -- as well as the bit before the '=>' (which is always
191 -- empty in interface files)
193 -- The parser ensures the type will have the right shape.
194 -- (e.g. see ParseUtil.checkInstType)
196 getHsInstHead (HsForAllTy (Just tvs) _ tau) = (tvs, get_head1 tau)
197 getHsInstHead tau = ([], get_head1 tau)
199 get_head1 (HsFunTy _ ty) = get_head1 ty
200 get_head1 (HsPredTy (HsClassP cls tys)) = (cls,tys)
204 %************************************************************************
206 \subsection{Pretty printing}
208 %************************************************************************
210 NB: these types get printed into interface files, so
211 don't change the printing format lightly
214 instance (Outputable name) => Outputable (HsType name) where
215 ppr ty = pprHsType ty
217 instance (Outputable name) => Outputable (HsTyOp name) where
218 ppr HsArrow = ftext FSLIT("->")
219 ppr (HsTyOp n) = ppr n
221 instance (Outputable name) => Outputable (HsTyVarBndr name) where
222 ppr (UserTyVar name) = ppr name
223 ppr (IfaceTyVar name kind) = pprHsTyVarBndr name kind
225 instance Outputable name => Outputable (HsPred name) where
226 ppr (HsClassP clas tys) = ppr clas <+> hsep (map pprParendHsType tys)
227 ppr (HsIParam n ty) = hsep [ppr n, dcolon, ppr ty]
229 pprHsTyVarBndr :: Outputable name => name -> Kind -> SDoc
230 pprHsTyVarBndr name kind | kind `eqKind` liftedTypeKind = ppr name
231 | otherwise = hsep [ppr name, dcolon, pprParendKind kind]
233 pprHsForAll [] [] = empty
235 -- This printer is used for both interface files and
236 -- printing user types in error messages; and alas the
237 -- two use slightly different syntax. Ah well.
238 = getPprStyle $ \ sty ->
239 if userStyle sty then
240 ptext SLIT("forall") <+> interppSP tvs <> dot <+>
241 -- **! ToDo: want to hide uvars from user, but not enough info
242 -- in a HsTyVarBndr name (see PprType). KSW 2000-10.
244 else -- Used in interfaces
245 ptext SLIT("__forall") <+> interppSP tvs <+>
246 ppr_hs_context cxt <+> ptext SLIT("=>")
248 pprHsContext :: (Outputable name) => HsContext name -> SDoc
249 pprHsContext [] = empty
250 pprHsContext cxt = ppr_hs_context cxt <+> ptext SLIT("=>")
252 ppr_hs_context [] = empty
253 ppr_hs_context cxt = parens (interpp'SP cxt)
257 pREC_TOP = (0 :: Int) -- type in ParseIface.y
258 pREC_FUN = (1 :: Int) -- btype in ParseIface.y
259 pREC_CON = (2 :: Int) -- atype in ParseIface.y
261 maybeParen :: Bool -> SDoc -> SDoc
262 maybeParen True p = parens p
263 maybeParen False p = p
265 -- printing works more-or-less as for Types
267 pprHsType, pprParendHsType :: (Outputable name) => HsType name -> SDoc
269 pprHsType ty = ppr_mono_ty pREC_TOP ty
270 pprParendHsType ty = ppr_mono_ty pREC_CON ty
272 ppr_mono_ty ctxt_prec (HsForAllTy maybe_tvs ctxt ty)
273 = maybeParen (ctxt_prec >= pREC_FUN) $
274 sep [pp_header, pprHsType ty]
276 pp_header = case maybe_tvs of
277 Just tvs -> pprHsForAll tvs ctxt
278 Nothing -> pprHsContext ctxt
280 ppr_mono_ty ctxt_prec (HsTyVar name)
283 ppr_mono_ty ctxt_prec (HsFunTy ty1 ty2)
284 = let p1 = ppr_mono_ty pREC_FUN ty1
285 p2 = ppr_mono_ty pREC_TOP ty2
287 maybeParen (ctxt_prec >= pREC_FUN)
288 (sep [p1, (<>) (ptext SLIT("-> ")) p2])
290 ppr_mono_ty ctxt_prec (HsTupleTy con tys) = hsTupParens con (interpp'SP tys)
291 ppr_mono_ty ctxt_prec (HsKindSig ty kind) = parens (ppr_mono_ty pREC_TOP ty <+> dcolon <+> pprKind kind)
292 ppr_mono_ty ctxt_prec (HsListTy ty) = brackets (ppr_mono_ty pREC_TOP ty)
293 ppr_mono_ty ctxt_prec (HsPArrTy ty) = pabrackets (ppr_mono_ty pREC_TOP ty)
295 pabrackets p = ptext SLIT("[:") <> p <> ptext SLIT(":]")
297 ppr_mono_ty ctxt_prec (HsAppTy fun_ty arg_ty)
298 = maybeParen (ctxt_prec >= pREC_CON)
299 (hsep [ppr_mono_ty pREC_FUN fun_ty, ppr_mono_ty pREC_CON arg_ty])
301 ppr_mono_ty ctxt_prec (HsPredTy pred)
305 ppr_mono_ty ctxt_prec (HsNumTy n) = integer n
306 ppr_mono_ty ctxt_prec (HsOpTy ty1 op ty2) = ppr ty1 <+> ppr op <+> ppr ty2
310 %************************************************************************
312 \subsection{Converting from Type to HsType}
314 %************************************************************************
316 @toHsType@ converts from a Type to a HsType, making the latter look as
317 user-friendly as possible. Notably, it uses synonyms where possible, and
318 expresses overloaded functions using the '=>' context part of a HsForAllTy.
321 toHsTyVar :: TyVar -> HsTyVarBndr Name
322 toHsTyVar tv = IfaceTyVar (getName tv) (tyVarKind tv)
324 toHsTyVars tvs = map toHsTyVar tvs
326 toHsType :: Type -> HsType Name
327 -- This function knows the representation of types
328 toHsType (TyVarTy tv) = HsTyVar (getName tv)
329 toHsType (FunTy arg res) = HsFunTy (toHsType arg) (toHsType res)
330 toHsType (AppTy fun arg) = HsAppTy (toHsType fun) (toHsType arg)
332 toHsType (NoteTy (SynNote ty@(TyConApp tycon tyargs)) real_ty)
333 | isNewTyCon tycon = toHsType ty
334 | syn_matches = toHsType ty -- Use synonyms if possible!!
337 pprTrace "WARNING: synonym info lost in .hi file for " (ppr syn_ty) $
339 toHsType real_ty -- but drop it if not.
341 syn_matches = ty_from_syn `tcEqType` real_ty
342 (tyvars,syn_ty) = getSynTyConDefn tycon
343 ty_from_syn = substTyWith tyvars tyargs syn_ty
345 -- We only use the type synonym in the file if this doesn't cause
346 -- us to lose important information. This matters for usage
347 -- annotations. It's an issue if some of the args to the synonym
348 -- have arrows in them, or if the synonym's RHS has an arrow; for
349 -- example, with nofib/real/ebnf2ps/ in Parsers.using.
351 -- **! It would be nice if when this test fails we could still
352 -- write the synonym in as a Note, so we don't lose the info for
353 -- error messages, but it's too much work for right now.
356 toHsType (NoteTy _ ty) = toHsType ty
358 toHsType (SourceTy (NType tc tys)) = foldl HsAppTy (HsTyVar (getName tc)) (map toHsType tys)
359 toHsType (SourceTy pred) = HsPredTy (toHsPred pred)
361 toHsType ty@(TyConApp tc tys) -- Must be saturated because toHsType's arg is of kind *
362 | not saturated = generic_case
363 | isTupleTyCon tc = HsTupleTy (HsTupCon (getName tc) (tupleTyConBoxity tc) (tyConArity tc)) tys'
364 | tc `hasKey` listTyConKey = HsListTy (head tys')
365 | tc `hasKey` parrTyConKey = HsPArrTy (head tys')
366 | tc `hasKey` usOnceTyConKey = hsUsOnce_Name -- must print !, . unqualified
367 | tc `hasKey` usManyTyConKey = hsUsMany_Name -- must print !, . unqualified
368 | otherwise = generic_case
370 generic_case = foldl HsAppTy (HsTyVar (getName tc)) tys'
371 tys' = map toHsType tys
372 saturated = tys `lengthIs` tyConArity tc
374 toHsType ty@(ForAllTy _ _) = case tcSplitSigmaTy ty of
375 (tvs, preds, tau) -> HsForAllTy (Just (map toHsTyVar tvs))
379 toHsPred (ClassP cls tys) = HsClassP (getName cls) (map toHsType tys)
380 toHsPred (IParam n ty) = HsIParam n (toHsType ty)
382 toHsContext :: ThetaType -> HsContext Name
383 toHsContext theta = map toHsPred theta
385 toHsFDs :: [FunDep TyVar] -> [FunDep Name]
386 toHsFDs fds = [(map getName ns, map getName ms) | (ns,ms) <- fds]
390 %************************************************************************
392 \subsection{Comparison}
394 %************************************************************************
397 instance Ord a => Eq (HsType a) where
398 -- The Ord is needed because we keep a
399 -- finite map of variables to variables
400 (==) a b = eq_hsType emptyEqHsEnv a b
402 instance Ord a => Eq (HsPred a) where
403 (==) a b = eq_hsPred emptyEqHsEnv a b
405 eqWithHsTyVars :: Ord name =>
406 [HsTyVarBndr name] -> [HsTyVarBndr name]
407 -> (EqHsEnv name -> Bool) -> Bool
408 eqWithHsTyVars = eq_hsTyVars emptyEqHsEnv
412 type EqHsEnv n = FiniteMap n n
413 -- Tracks the mapping from L-variables to R-variables
415 eq_hsVar :: Ord n => EqHsEnv n -> n -> n -> Bool
416 eq_hsVar env n1 n2 = case lookupFM env n1 of
420 extendEqHsEnv env n1 n2
422 | otherwise = addToFM env n1 n2
424 emptyEqHsEnv :: EqHsEnv n
425 emptyEqHsEnv = emptyFM
428 We do define a specialised equality for these \tr{*Type} types; used
429 in checking interfaces.
433 eq_hsTyVars env [] [] k = k env
434 eq_hsTyVars env (tv1:tvs1) (tv2:tvs2) k = eq_hsTyVar env tv1 tv2 $ \ env ->
435 eq_hsTyVars env tvs1 tvs2 k
436 eq_hsTyVars env _ _ _ = False
438 eq_hsTyVar env (UserTyVar v1) (UserTyVar v2) k = k (extendEqHsEnv env v1 v2)
439 eq_hsTyVar env (IfaceTyVar v1 k1) (IfaceTyVar v2 k2) k = k1 `eqKind` k2 && k (extendEqHsEnv env v1 v2)
440 eq_hsTyVar env _ _ _ = False
442 eq_hsVars env [] [] k = k env
443 eq_hsVars env (v1:bs1) (v2:bs2) k = eq_hsVars (extendEqHsEnv env v1 v2) bs1 bs2 k
444 eq_hsVars env _ _ _ = False
449 eq_hsTypes env = eqListBy (eq_hsType env)
452 eq_hsType env (HsForAllTy tvs1 c1 t1) (HsForAllTy tvs2 c2 t2)
453 = eq_tvs tvs1 tvs2 $ \env ->
454 eq_hsContext env c1 c2 &&
457 eq_tvs Nothing (Just _) k = False
458 eq_tvs Nothing Nothing k = k env
459 eq_tvs (Just _) Nothing k = False
460 eq_tvs (Just tvs1) (Just tvs2) k = eq_hsTyVars env tvs1 tvs2 k
462 eq_hsType env (HsTyVar n1) (HsTyVar n2)
465 eq_hsType env (HsTupleTy c1 tys1) (HsTupleTy c2 tys2)
466 = (c1 == c2) && eq_hsTypes env tys1 tys2
468 eq_hsType env (HsListTy ty1) (HsListTy ty2)
469 = eq_hsType env ty1 ty2
471 eq_hsType env (HsKindSig ty1 k1) (HsKindSig ty2 k2)
472 = eq_hsType env ty1 ty2 && k1 `eqKind` k2
474 eq_hsType env (HsPArrTy ty1) (HsPArrTy ty2)
475 = eq_hsType env ty1 ty2
477 eq_hsType env (HsAppTy fun_ty1 arg_ty1) (HsAppTy fun_ty2 arg_ty2)
478 = eq_hsType env fun_ty1 fun_ty2 && eq_hsType env arg_ty1 arg_ty2
480 eq_hsType env (HsFunTy a1 b1) (HsFunTy a2 b2)
481 = eq_hsType env a1 a2 && eq_hsType env b1 b2
483 eq_hsType env (HsPredTy p1) (HsPredTy p2)
484 = eq_hsPred env p1 p2
486 eq_hsType env (HsOpTy lty1 op1 rty1) (HsOpTy lty2 op2 rty2)
487 = eq_hsOp env op1 op2 && eq_hsType env lty1 lty2 && eq_hsType env rty1 rty2
489 eq_hsType env ty1 ty2 = False
492 eq_hsOp env (HsTyOp n1) (HsTyOp n2) = eq_hsVar env n1 n2
493 eq_hsOp env HsArrow HsArrow = True
494 eq_hsOp env op1 op2 = False
497 eq_hsContext env a b = eqListBy (eq_hsPred env) a b
500 eq_hsPred env (HsClassP c1 tys1) (HsClassP c2 tys2)
501 = c1 == c2 && eq_hsTypes env tys1 tys2
502 eq_hsPred env (HsIParam n1 ty1) (HsIParam n2 ty2)
503 = n1 == n2 && eq_hsType env ty1 ty2
504 eq_hsPred env _ _ = False