2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[HsTypes]{Abstract syntax: user-defined types}
8 HsType(..), HsUsageAnn(..), HsTyVarBndr(..),
9 , HsContext, HsPred(..)
10 , HsTupCon(..), hsTupParens, mkHsTupCon,
12 , mkHsForAllTy, mkHsUsForAllTy, mkHsDictTy, mkHsIParamTy
13 , hsTyVarName, hsTyVarNames, replaceTyVarName
16 , pprParendHsType, pprHsForAll, pprHsContext, pprHsTyVarBndr
18 -- Equality over Hs things
19 , EqHsEnv, emptyEqHsEnv, extendEqHsEnv,
20 , eqWithHsTyVars, eq_hsVar, eq_hsVars, eq_hsType, eq_hsContext, eqListBy
22 -- Converting from Type to HsType
23 , toHsType, toHsTyVar, toHsTyVars, toHsContext, toHsFDs
26 #include "HsVersions.h"
28 import Class ( FunDep )
29 import Type ( Type, Kind, PredType(..), ClassContext,
30 splitSigmaTy, unUsgTy, boxedTypeKind
32 import TypeRep ( Type(..), TyNote(..) ) -- toHsType sees the representation
33 import TyCon ( isTupleTyCon, tupleTyConBoxity, tyConArity )
34 import RdrName ( RdrName )
35 import Name ( Name, getName )
36 import OccName ( NameSpace )
37 import Var ( TyVar, tyVarKind )
38 import PprType ( {- instance Outputable Kind -}, pprParendKind )
39 import BasicTypes ( Boxity(..), tupleParens )
40 import PrelNames ( mkTupConRdrName, listTyConKey, hasKey )
46 This is the syntax for types as seen in type signatures.
49 type HsContext name = [HsPred name]
51 data HsPred name = HsPClass name [HsType name]
52 | HsPIParam name (HsType name)
55 = HsForAllTy (Maybe [HsTyVarBndr name]) -- Nothing for implicitly quantified signatures
59 | HsTyVar name -- Type variable or type constructor
61 | HsAppTy (HsType name)
64 | HsFunTy (HsType name) -- function type
67 | HsListTy (HsType name) -- Element type
69 | HsTupleTy (HsTupCon name)
70 [HsType name] -- Element types (length gives arity)
72 | HsOpTy (HsType name) name (HsType name)
74 -- these next two are only used in interfaces
75 | HsPredTy (HsPred name)
77 | HsUsgTy (HsUsageAnn name)
89 -----------------------
90 data HsTupCon name = HsTupCon name Boxity
92 instance Eq name => Eq (HsTupCon name) where
93 (HsTupCon _ b1) == (HsTupCon _ b2) = b1==b2
95 mkHsTupCon :: NameSpace -> Boxity -> [a] -> HsTupCon RdrName
96 mkHsTupCon space boxity args = HsTupCon (mkTupConRdrName space boxity (length args)) boxity
98 hsTupParens :: HsTupCon name -> SDoc -> SDoc
99 hsTupParens (HsTupCon _ b) p = tupleParens b p
101 -----------------------
102 -- Combine adjacent for-alls.
103 -- The following awkward situation can happen otherwise:
104 -- f :: forall a. ((Num a) => Int)
105 -- might generate HsForAll (Just [a]) [] (HsForAll Nothing [Num a] t)
106 -- Then a isn't discovered as ambiguous, and we abstract the AbsBinds wrt []
107 -- but the export list abstracts f wrt [a]. Disaster.
109 -- A valid type must have one for-all at the top of the type, or of the fn arg types
111 mkHsForAllTy (Just []) [] ty = ty -- Explicit for-all with no tyvars
112 mkHsForAllTy mtvs1 [] (HsForAllTy mtvs2 ctxt ty) = mkHsForAllTy (mtvs1 `plus` mtvs2) ctxt ty
114 mtvs1 `plus` Nothing = mtvs1
115 Nothing `plus` mtvs2 = mtvs2
116 (Just tvs1) `plus` (Just tvs2) = Just (tvs1 ++ tvs2)
117 mkHsForAllTy tvs ctxt ty = HsForAllTy tvs ctxt ty
119 mkHsUsForAllTy uvs ty = foldr (\ uv ty -> HsUsgForAllTy uv ty)
122 mkHsDictTy cls tys = HsPredTy (HsPClass cls tys)
123 mkHsIParamTy v ty = HsPredTy (HsPIParam v ty)
125 data HsTyVarBndr name
127 | IfaceTyVar name Kind
128 -- *** NOTA BENE *** A "monotype" in a pragma can have
129 -- for-alls in it, (mostly to do with dictionaries). These
130 -- must be explicitly Kinded.
132 hsTyVarName (UserTyVar n) = n
133 hsTyVarName (IfaceTyVar n _) = n
135 hsTyVarNames tvs = map hsTyVarName tvs
137 replaceTyVarName :: HsTyVarBndr name1 -> name2 -> HsTyVarBndr name2
138 replaceTyVarName (UserTyVar n) n' = UserTyVar n'
139 replaceTyVarName (IfaceTyVar n k) n' = IfaceTyVar n' k
143 %************************************************************************
145 \subsection{Pretty printing}
147 %************************************************************************
149 NB: these types get printed into interface files, so
150 don't change the printing format lightly
153 instance (Outputable name) => Outputable (HsType name) where
154 ppr ty = pprHsType ty
156 instance (Outputable name) => Outputable (HsTyVarBndr name) where
157 ppr (UserTyVar name) = ppr name
158 ppr (IfaceTyVar name kind) = pprHsTyVarBndr name kind
160 instance Outputable name => Outputable (HsPred name) where
161 ppr (HsPClass clas tys) = ppr clas <+> hsep (map pprParendHsType tys)
162 ppr (HsPIParam n ty) = hsep [char '?' <> ppr n, text "::", ppr ty]
164 pprHsTyVarBndr :: Outputable name => name -> Kind -> SDoc
165 pprHsTyVarBndr name kind | kind == boxedTypeKind = ppr name
166 | otherwise = hsep [ppr name, dcolon, pprParendKind kind]
168 pprHsForAll [] [] = empty
170 -- This printer is used for both interface files and
171 -- printing user types in error messages; and alas the
172 -- two use slightly different syntax. Ah well.
173 = getPprStyle $ \ sty ->
174 if userStyle sty then
175 ptext SLIT("forall") <+> interppSP tvs <> dot <+>
179 ppr_context cxt <+> ptext SLIT("=>")
181 else -- Used in interfaces
182 ptext SLIT("__forall") <+> interppSP tvs <+>
183 ppr_context cxt <+> ptext SLIT("=>")
185 pprHsContext :: (Outputable name) => HsContext name -> SDoc
186 pprHsContext [] = empty
187 pprHsContext cxt = ppr_context cxt <+> ptext SLIT("=>")
189 ppr_context [] = empty
190 ppr_context cxt = parens (interpp'SP cxt)
194 pREC_TOP = (0 :: Int)
195 pREC_FUN = (1 :: Int)
196 pREC_CON = (2 :: Int)
198 maybeParen :: Bool -> SDoc -> SDoc
199 maybeParen True p = parens p
200 maybeParen False p = p
202 -- printing works more-or-less as for Types
204 pprHsType, pprParendHsType :: (Outputable name) => HsType name -> SDoc
206 pprHsType ty = ppr_mono_ty pREC_TOP ty
207 pprParendHsType ty = ppr_mono_ty pREC_CON ty
209 ppr_mono_ty ctxt_prec (HsForAllTy maybe_tvs ctxt ty)
210 = maybeParen (ctxt_prec >= pREC_FUN) $
211 sep [pp_header, pprHsType ty]
213 pp_header = case maybe_tvs of
214 Just tvs -> pprHsForAll tvs ctxt
215 Nothing -> pprHsContext ctxt
217 ppr_mono_ty ctxt_prec (HsTyVar name)
220 ppr_mono_ty ctxt_prec (HsFunTy ty1 ty2)
221 = let p1 = ppr_mono_ty pREC_FUN ty1
222 p2 = ppr_mono_ty pREC_TOP ty2
224 maybeParen (ctxt_prec >= pREC_FUN)
225 (sep [p1, (<>) (ptext SLIT("-> ")) p2])
227 ppr_mono_ty ctxt_prec (HsTupleTy con tys) = hsTupParens con (interpp'SP tys)
228 ppr_mono_ty ctxt_prec (HsListTy ty) = brackets (ppr_mono_ty pREC_TOP ty)
230 ppr_mono_ty ctxt_prec (HsAppTy fun_ty arg_ty)
231 = maybeParen (ctxt_prec >= pREC_CON)
232 (hsep [ppr_mono_ty pREC_FUN fun_ty, ppr_mono_ty pREC_CON arg_ty])
234 ppr_mono_ty ctxt_prec (HsPredTy pred)
235 = maybeParen (ctxt_prec >= pREC_FUN) $
238 ppr_mono_ty ctxt_prec ty@(HsUsgForAllTy _ _)
240 sep [ ptext SLIT("__fuall") <+> brackets pp_uvars <+> ptext SLIT("=>"),
241 ppr_mono_ty pREC_TOP sigma
244 (uvars,sigma) = split [] ty
245 pp_uvars = interppSP uvars
247 split uvs (HsUsgForAllTy uv ty') = split (uv:uvs) ty'
248 split uvs ty' = (reverse uvs,ty')
250 ppr_mono_ty ctxt_prec (HsUsgTy u ty)
251 = maybeParen (ctxt_prec >= pREC_CON) $
252 ptext SLIT("__u") <+> pp_ua <+> ppr_mono_ty pREC_CON ty
255 HsUsOnce -> ptext SLIT("-")
256 HsUsMany -> ptext SLIT("!")
259 ppr_mono_ty ctxt_prec (HsNumTy n) = integer n
260 ppr_mono_ty ctxt_prec (HsOpTy ty1 op ty2) = ppr ty1 <+> ppr op <+> ppr ty2
264 %************************************************************************
266 \subsection{Converting from Type to HsType}
268 %************************************************************************
270 @toHsType@ converts from a Type to a HsType, making the latter look as
271 user-friendly as possible. Notably, it uses synonyms where possible, and
272 expresses overloaded functions using the '=>' context part of a HsForAllTy.
275 toHsTyVar :: TyVar -> HsTyVarBndr Name
276 toHsTyVar tv = IfaceTyVar (getName tv) (tyVarKind tv)
278 toHsTyVars tvs = map toHsTyVar tvs
280 toHsType :: Type -> HsType Name
281 toHsType ty = toHsType' (unUsgTy ty)
282 -- For now we just discard the usage
284 toHsType' :: Type -> HsType Name
285 -- Called after the usage is stripped off
286 -- This function knows the representation of types
287 toHsType' (TyVarTy tv) = HsTyVar (getName tv)
288 toHsType' (FunTy arg res) = HsFunTy (toHsType arg) (toHsType res)
289 toHsType' (AppTy fun arg) = HsAppTy (toHsType fun) (toHsType arg)
291 toHsType' (NoteTy (SynNote ty) _) = toHsType ty -- Use synonyms if possible!!
292 toHsType' (NoteTy _ ty) = toHsType ty
294 toHsType' (PredTy p) = HsPredTy (toHsPred p)
296 toHsType' ty@(TyConApp tc tys) -- Must be saturated because toHsType's arg is of kind *
297 | not saturated = generic_case
298 | isTupleTyCon tc = HsTupleTy (HsTupCon (getName tc) (tupleTyConBoxity tc)) tys'
299 | tc `hasKey` listTyConKey = HsListTy (head tys')
300 | otherwise = generic_case
302 generic_case = foldl HsAppTy (HsTyVar (getName tc)) tys'
303 tys' = map toHsType tys
304 saturated = length tys == tyConArity tc
306 toHsType' ty@(ForAllTy _ _) = case splitSigmaTy ty of
307 (tvs, preds, tau) -> HsForAllTy (Just (map toHsTyVar tvs))
312 toHsPred (Class cls tys) = HsPClass (getName cls) (map toHsType tys)
313 toHsPred (IParam n ty) = HsPIParam (getName n) (toHsType ty)
315 toHsContext :: ClassContext -> HsContext Name
316 toHsContext cxt = [HsPClass (getName cls) (map toHsType tys) | (cls,tys) <- cxt]
318 toHsFDs :: [FunDep TyVar] -> [FunDep Name]
319 toHsFDs fds = [(map getName ns, map getName ms) | (ns,ms) <- fds]
323 %************************************************************************
325 \subsection{Comparison}
327 %************************************************************************
330 instance Ord a => Eq (HsType a) where
331 -- The Ord is needed because we keep a
332 -- finite map of variables to variables
333 (==) a b = eq_hsType emptyEqHsEnv a b
335 instance Ord a => Eq (HsPred a) where
336 (==) a b = eq_hsPred emptyEqHsEnv a b
338 eqWithHsTyVars :: Ord name =>
339 [HsTyVarBndr name] -> [HsTyVarBndr name]
340 -> (EqHsEnv name -> Bool) -> Bool
341 eqWithHsTyVars = eq_hsTyVars emptyEqHsEnv
345 type EqHsEnv n = FiniteMap n n
346 -- Tracks the mapping from L-variables to R-variables
348 eq_hsVar :: Ord n => EqHsEnv n -> n -> n -> Bool
349 eq_hsVar env n1 n2 = case lookupFM env n1 of
353 extendEqHsEnv env n1 n2
355 | otherwise = addToFM env n1 n2
357 emptyEqHsEnv :: EqHsEnv n
358 emptyEqHsEnv = emptyFM
361 We do define a specialised equality for these \tr{*Type} types; used
362 in checking interfaces.
366 eq_hsTyVars env [] [] k = k env
367 eq_hsTyVars env (tv1:tvs1) (tv2:tvs2) k = eq_hsTyVar env tv1 tv2 $ \ env ->
368 eq_hsTyVars env tvs1 tvs2 k
369 eq_hsTyVars env _ _ _ = False
371 eq_hsTyVar env (UserTyVar v1) (UserTyVar v2) k = k (extendEqHsEnv env v1 v2)
372 eq_hsTyVar env (IfaceTyVar v1 k1) (IfaceTyVar v2 k2) k = k1 == k2 && k (extendEqHsEnv env v1 v2)
373 eq_hsTyVar env _ _ _ = False
375 eq_hsVars env [] [] k = k env
376 eq_hsVars env (v1:bs1) (v2:bs2) k = eq_hsVars (extendEqHsEnv env v1 v2) bs1 bs2 k
377 eq_hsVars env _ _ _ = False
382 eq_hsTypes env = eqListBy (eq_hsType env)
385 eq_hsType env (HsForAllTy tvs1 c1 t1) (HsForAllTy tvs2 c2 t2)
386 = eq_tvs tvs1 tvs2 $ \env ->
387 eq_hsContext env c1 c2 &&
390 eq_tvs Nothing (Just _) k = False
391 eq_tvs Nothing Nothing k = k env
392 eq_tvs (Just _) Nothing k = False
393 eq_tvs (Just tvs1) (Just tvs2) k = eq_hsTyVars env tvs1 tvs2 k
395 eq_hsType env (HsTyVar n1) (HsTyVar n2)
398 eq_hsType env (HsTupleTy c1 tys1) (HsTupleTy c2 tys2)
399 = (c1 == c2) && eq_hsTypes env tys1 tys2
401 eq_hsType env (HsListTy ty1) (HsListTy ty2)
402 = eq_hsType env ty1 ty2
404 eq_hsType env (HsAppTy fun_ty1 arg_ty1) (HsAppTy fun_ty2 arg_ty2)
405 = eq_hsType env fun_ty1 fun_ty2 && eq_hsType env arg_ty1 arg_ty2
407 eq_hsType env (HsFunTy a1 b1) (HsFunTy a2 b2)
408 = eq_hsType env a1 a2 && eq_hsType env b1 b2
410 eq_hsType env (HsPredTy p1) (HsPredTy p2)
411 = eq_hsPred env p1 p2
413 eq_hsType env (HsOpTy lty1 op1 rty1) (HsOpTy lty2 op2 rty2)
414 = eq_hsVar env op1 op2 && eq_hsType env lty1 lty2 && eq_hsType env rty1 rty2
416 eq_hsType env (HsUsgTy u1 ty1) (HsUsgTy u2 ty2)
417 = eqUsg u1 u2 && eq_hsType env ty1 ty2
419 eq_hsType env ty1 ty2 = False
423 eq_hsContext env a b = eqListBy (eq_hsPred env) a b
426 eq_hsPred env (HsPClass c1 tys1) (HsPClass c2 tys2)
427 = c1 == c2 && eq_hsTypes env tys1 tys2
428 eq_hsPred env (HsPIParam n1 ty1) (HsPIParam n2 ty2)
429 = n1 == n2 && eq_hsType env ty1 ty2
430 eq_hsPred env _ _ = False
433 eqUsg HsUsOnce HsUsOnce = True
434 eqUsg HsUsMany HsUsMany = True
435 eqUsg (HsUsVar u1) (HsUsVar u2) = u1 == u2
439 eqListBy :: (a->a->Bool) -> [a] -> [a] -> Bool
440 eqListBy eq [] [] = True
441 eqListBy eq (x:xs) (y:ys) = eq x y && eqListBy eq xs ys
442 eqListBy eq xs ys = False