2 % (c) The GRASP/AQUA Project, Glasgow University, 1998
4 \section[Type]{Type - public interface}
8 -- re-exports from TypeRep:
10 Type, PredType(..), ThetaType,
13 superKind, superBoxity, -- KX and BX respectively
14 liftedBoxity, unliftedBoxity, -- :: BX
16 typeCon, -- :: BX -> KX
17 liftedTypeKind, unliftedTypeKind, openTypeKind, -- :: KX
18 mkArrowKind, mkArrowKinds, -- :: KX -> KX -> KX
19 isTypeKind, isAnyTypeKind,
22 -- exports from this module:
23 hasMoreBoxityInfo, defaultKind,
25 mkTyVarTy, mkTyVarTys, getTyVar, getTyVar_maybe, isTyVarTy,
27 mkAppTy, mkAppTys, splitAppTy, splitAppTys, splitAppTy_maybe,
29 mkFunTy, mkFunTys, splitFunTy, splitFunTy_maybe, splitFunTys,
30 funResultTy, funArgTy, zipFunTys, isFunTy,
32 mkGenTyConApp, mkTyConApp, mkTyConTy,
33 tyConAppTyCon, tyConAppArgs,
34 splitTyConApp_maybe, splitTyConApp,
40 mkForAllTy, mkForAllTys, splitForAllTy_maybe, splitForAllTys,
41 applyTy, applyTys, isForAllTy, dropForAlls,
44 predTypeRep, mkPredTy, mkPredTys,
47 splitRecNewType_maybe,
50 isUnLiftedType, isUnboxedTupleType, isAlgType, isPrimitiveType,
51 isStrictType, isStrictPred,
54 tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tyVarsOfTheta,
55 typeKind, addFreeTyVars,
57 -- Tidying up for printing
59 tidyOpenType, tidyOpenTypes,
60 tidyTyVarBndr, tidyFreeTyVars,
61 tidyOpenTyVar, tidyOpenTyVars,
62 tidyTopType, tidyPred,
71 pprKind, pprParendKind,
72 pprType, pprParendType,
73 pprPred, pprTheta, pprThetaArrow, pprClassPred
76 #include "HsVersions.h"
78 -- We import the representation and primitive functions from TypeRep.
79 -- Many things are reexported, but not the representation!
85 import {-# SOURCE #-} Subst ( substTyWith )
88 import Var ( TyVar, tyVarKind, tyVarName, setTyVarName )
92 import Name ( NamedThing(..), mkInternalName, tidyOccName )
93 import Class ( Class, classTyCon )
94 import TyCon ( TyCon, isRecursiveTyCon, isPrimTyCon,
95 isUnboxedTupleTyCon, isUnLiftedTyCon,
96 isFunTyCon, isNewTyCon, newTyConRep,
97 isAlgTyCon, isSynTyCon, tyConArity,
98 tyConKind, getSynTyConDefn,
103 import CmdLineOpts ( opt_DictsStrict )
104 import SrcLoc ( noSrcLoc )
105 import PrimRep ( PrimRep(..) )
106 import Unique ( Uniquable(..) )
107 import Util ( mapAccumL, seqList, lengthIs, snocView )
109 import UniqSet ( sizeUniqSet ) -- Should come via VarSet
110 import Maybe ( isJust )
114 %************************************************************************
116 \subsection{Stuff to do with kinds.}
118 %************************************************************************
121 hasMoreBoxityInfo :: Kind -> Kind -> Bool
122 -- (k1 `hasMoreBoxityInfo` k2) checks that k1 <: k2
123 hasMoreBoxityInfo k1 k2
124 | k2 `eqKind` openTypeKind = isAnyTypeKind k1
125 | otherwise = k1 `eqKind` k2
127 isAnyTypeKind :: Kind -> Bool
128 -- True of kind * and *# and ?
129 isAnyTypeKind (TyConApp tc _) = tc == typeCon || tc == openKindCon
130 isAnyTypeKind (NoteTy _ k) = isAnyTypeKind k
131 isAnyTypeKind other = False
133 isTypeKind :: Kind -> Bool
134 -- True of kind * and *#
135 isTypeKind (TyConApp tc _) = tc == typeCon
136 isTypeKind (NoteTy _ k) = isTypeKind k
137 isTypeKind other = False
139 defaultKind :: Kind -> Kind
140 -- Used when generalising: default kind '?' to '*'
141 defaultKind kind | kind `eqKind` openTypeKind = liftedTypeKind
146 %************************************************************************
148 \subsection{Constructor-specific functions}
150 %************************************************************************
153 ---------------------------------------------------------------------
157 mkTyVarTy :: TyVar -> Type
160 mkTyVarTys :: [TyVar] -> [Type]
161 mkTyVarTys = map mkTyVarTy -- a common use of mkTyVarTy
163 getTyVar :: String -> Type -> TyVar
164 getTyVar msg ty = case getTyVar_maybe ty of
166 Nothing -> panic ("getTyVar: " ++ msg)
168 isTyVarTy :: Type -> Bool
169 isTyVarTy ty = isJust (getTyVar_maybe ty)
171 getTyVar_maybe :: Type -> Maybe TyVar
172 getTyVar_maybe (TyVarTy tv) = Just tv
173 getTyVar_maybe (NoteTy _ t) = getTyVar_maybe t
174 getTyVar_maybe (PredTy p) = getTyVar_maybe (predTypeRep p)
175 getTyVar_maybe (NewTcApp tc tys) = getTyVar_maybe (newTypeRep tc tys)
176 getTyVar_maybe other = Nothing
180 ---------------------------------------------------------------------
183 We need to be pretty careful with AppTy to make sure we obey the
184 invariant that a TyConApp is always visibly so. mkAppTy maintains the
188 mkAppTy orig_ty1 orig_ty2
191 mk_app (NoteTy _ ty1) = mk_app ty1
192 mk_app (NewTcApp tc tys) = NewTcApp tc (tys ++ [orig_ty2])
193 mk_app (TyConApp tc tys) = mkGenTyConApp tc (tys ++ [orig_ty2])
194 mk_app ty1 = AppTy orig_ty1 orig_ty2
195 -- We call mkGenTyConApp because the TyConApp could be an
196 -- under-saturated type synonym. GHC allows that; e.g.
197 -- type Foo k = k a -> k a
199 -- foo :: Foo Id -> Foo Id
201 -- Here Id is partially applied in the type sig for Foo,
202 -- but once the type synonyms are expanded all is well
204 mkAppTys :: Type -> [Type] -> Type
205 mkAppTys orig_ty1 [] = orig_ty1
206 -- This check for an empty list of type arguments
207 -- avoids the needless loss of a type synonym constructor.
208 -- For example: mkAppTys Rational []
209 -- returns to (Ratio Integer), which has needlessly lost
210 -- the Rational part.
211 mkAppTys orig_ty1 orig_tys2
214 mk_app (NoteTy _ ty1) = mk_app ty1
215 mk_app (NewTcApp tc tys) = NewTcApp tc (tys ++ orig_tys2)
216 mk_app (TyConApp tc tys) = mkTyConApp tc (tys ++ orig_tys2)
217 -- Use mkTyConApp in case tc is (->)
218 mk_app ty1 = foldl AppTy orig_ty1 orig_tys2
220 splitAppTy_maybe :: Type -> Maybe (Type, Type)
221 splitAppTy_maybe (FunTy ty1 ty2) = Just (TyConApp funTyCon [ty1], ty2)
222 splitAppTy_maybe (AppTy ty1 ty2) = Just (ty1, ty2)
223 splitAppTy_maybe (NoteTy _ ty) = splitAppTy_maybe ty
224 splitAppTy_maybe (PredTy p) = splitAppTy_maybe (predTypeRep p)
225 splitAppTy_maybe (NewTcApp tc tys) = splitAppTy_maybe (newTypeRep tc tys)
226 splitAppTy_maybe (TyConApp tc tys) = case snocView tys of
228 Just (tys',ty') -> Just (mkGenTyConApp tc tys', ty')
229 -- mkGenTyConApp just in case the tc is a newtype
231 splitAppTy_maybe other = Nothing
233 splitAppTy :: Type -> (Type, Type)
234 splitAppTy ty = case splitAppTy_maybe ty of
236 Nothing -> panic "splitAppTy"
238 splitAppTys :: Type -> (Type, [Type])
239 splitAppTys ty = split ty ty []
241 split orig_ty (AppTy ty arg) args = split ty ty (arg:args)
242 split orig_ty (NoteTy _ ty) args = split orig_ty ty args
243 split orig_ty (PredTy p) args = split orig_ty (predTypeRep p) args
244 split orig_ty (NewTcApp tc tc_args) args = split orig_ty (newTypeRep tc tc_args) args
245 split orig_ty (TyConApp tc tc_args) args = (mkGenTyConApp tc [], tc_args ++ args)
246 -- mkGenTyConApp just in case the tc is a newtype
247 split orig_ty (FunTy ty1 ty2) args = ASSERT( null args )
248 (TyConApp funTyCon [], [ty1,ty2])
249 split orig_ty ty args = (orig_ty, args)
253 ---------------------------------------------------------------------
258 mkFunTy :: Type -> Type -> Type
259 mkFunTy arg res = FunTy arg res
261 mkFunTys :: [Type] -> Type -> Type
262 mkFunTys tys ty = foldr FunTy ty tys
264 isFunTy :: Type -> Bool
265 isFunTy ty = isJust (splitFunTy_maybe ty)
267 splitFunTy :: Type -> (Type, Type)
268 splitFunTy (FunTy arg res) = (arg, res)
269 splitFunTy (NoteTy _ ty) = splitFunTy ty
270 splitFunTy (PredTy p) = splitFunTy (predTypeRep p)
271 splitFunTy (NewTcApp tc tys) = splitFunTy (newTypeRep tc tys)
272 splitFunTy other = pprPanic "splitFunTy" (ppr other)
274 splitFunTy_maybe :: Type -> Maybe (Type, Type)
275 splitFunTy_maybe (FunTy arg res) = Just (arg, res)
276 splitFunTy_maybe (NoteTy _ ty) = splitFunTy_maybe ty
277 splitFunTy_maybe (PredTy p) = splitFunTy_maybe (predTypeRep p)
278 splitFunTy_maybe (NewTcApp tc tys) = splitFunTy_maybe (newTypeRep tc tys)
279 splitFunTy_maybe other = Nothing
281 splitFunTys :: Type -> ([Type], Type)
282 splitFunTys ty = split [] ty ty
284 split args orig_ty (FunTy arg res) = split (arg:args) res res
285 split args orig_ty (NoteTy _ ty) = split args orig_ty ty
286 split args orig_ty (PredTy p) = split args orig_ty (predTypeRep p)
287 split args orig_ty (NewTcApp tc tys) = split args orig_ty (newTypeRep tc tys)
288 split args orig_ty ty = (reverse args, orig_ty)
290 zipFunTys :: Outputable a => [a] -> Type -> ([(a,Type)], Type)
291 zipFunTys orig_xs orig_ty = split [] orig_xs orig_ty orig_ty
293 split acc [] nty ty = (reverse acc, nty)
294 split acc (x:xs) nty (FunTy arg res) = split ((x,arg):acc) xs res res
295 split acc xs nty (NoteTy _ ty) = split acc xs nty ty
296 split acc xs nty (PredTy p) = split acc xs nty (predTypeRep p)
297 split acc xs nty (NewTcApp tc tys) = split acc xs nty (newTypeRep tc tys)
298 split acc (x:xs) nty ty = pprPanic "zipFunTys" (ppr orig_xs <+> ppr orig_ty)
300 funResultTy :: Type -> Type
301 funResultTy (FunTy arg res) = res
302 funResultTy (NoteTy _ ty) = funResultTy ty
303 funResultTy (PredTy p) = funResultTy (predTypeRep p)
304 funResultTy (NewTcApp tc tys) = funResultTy (newTypeRep tc tys)
305 funResultTy ty = pprPanic "funResultTy" (ppr ty)
307 funArgTy :: Type -> Type
308 funArgTy (FunTy arg res) = arg
309 funArgTy (NoteTy _ ty) = funArgTy ty
310 funArgTy (PredTy p) = funArgTy (predTypeRep p)
311 funArgTy (NewTcApp tc tys) = funArgTy (newTypeRep tc tys)
312 funArgTy ty = pprPanic "funArgTy" (ppr ty)
316 ---------------------------------------------------------------------
319 @mkTyConApp@ is a key function, because it builds a TyConApp, FunTy or PredTy,
323 mkGenTyConApp :: TyCon -> [Type] -> Type
325 | isSynTyCon tc = mkSynTy tc tys
326 | otherwise = mkTyConApp tc tys
328 mkTyConApp :: TyCon -> [Type] -> Type
329 -- Assumes TyCon is not a SynTyCon; use mkSynTy instead for those
331 | isFunTyCon tycon, [ty1,ty2] <- tys
338 = ASSERT(not (isSynTyCon tycon))
341 mkTyConTy :: TyCon -> Type
342 mkTyConTy tycon = mkTyConApp tycon []
344 -- splitTyConApp "looks through" synonyms, because they don't
345 -- mean a distinct type, but all other type-constructor applications
346 -- including functions are returned as Just ..
348 tyConAppTyCon :: Type -> TyCon
349 tyConAppTyCon ty = fst (splitTyConApp ty)
351 tyConAppArgs :: Type -> [Type]
352 tyConAppArgs ty = snd (splitTyConApp ty)
354 splitTyConApp :: Type -> (TyCon, [Type])
355 splitTyConApp ty = case splitTyConApp_maybe ty of
357 Nothing -> pprPanic "splitTyConApp" (ppr ty)
359 splitTyConApp_maybe :: Type -> Maybe (TyCon, [Type])
360 splitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
361 splitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res])
362 splitTyConApp_maybe (NoteTy _ ty) = splitTyConApp_maybe ty
363 splitTyConApp_maybe (PredTy p) = splitTyConApp_maybe (predTypeRep p)
364 splitTyConApp_maybe (NewTcApp tc tys) = splitTyConApp_maybe (newTypeRep tc tys)
365 splitTyConApp_maybe other = Nothing
369 ---------------------------------------------------------------------
375 | n_args == arity -- Exactly saturated
377 | n_args > arity -- Over-saturated
378 = case splitAt arity tys of { (as,bs) -> mkAppTys (mk_syn as) bs }
379 -- Its important to use mkAppTys, rather than (foldl AppTy),
380 -- because (mk_syn as) might well return a partially-applied
381 -- type constructor; indeed, usually will!
382 | otherwise -- Un-saturated
384 -- For the un-saturated case we build TyConApp directly
385 -- (mkTyConApp ASSERTs that the tc isn't a SynTyCon).
386 -- Here we are relying on checkValidType to find
387 -- the error. What we can't do is use mkSynTy with
388 -- too few arg tys, because that is utterly bogus.
391 mk_syn tys = NoteTy (SynNote (TyConApp tycon tys))
392 (substTyWith tyvars tys body)
394 (tyvars, body) = ASSERT( isSynTyCon tycon ) getSynTyConDefn tycon
395 arity = tyConArity tycon
399 Notes on type synonyms
400 ~~~~~~~~~~~~~~~~~~~~~~
401 The various "split" functions (splitFunTy, splitRhoTy, splitForAllTy) try
402 to return type synonyms whereever possible. Thus
407 splitFunTys (a -> Foo a) = ([a], Foo a)
410 The reason is that we then get better (shorter) type signatures in
411 interfaces. Notably this plays a role in tcTySigs in TcBinds.lhs.
416 repType looks through
420 (d) usage annotations
421 (e) [recursive] newtypes
422 It's useful in the back end.
425 repType :: Type -> Type
426 -- Only applied to types of kind *; hence tycons are saturated
427 repType (ForAllTy _ ty) = repType ty
428 repType (NoteTy _ ty) = repType ty
429 repType (PredTy p) = repType (predTypeRep p)
430 repType (NewTcApp tc tys) = ASSERT( tys `lengthIs` tyConArity tc )
431 repType (new_type_rep tc tys)
435 typePrimRep :: Type -> PrimRep
436 typePrimRep ty = case repType ty of
437 TyConApp tc _ -> tyConPrimRep tc
439 AppTy _ _ -> PtrRep -- ??
441 other -> pprPanic "typePrimRep" (ppr ty)
446 ---------------------------------------------------------------------
451 mkForAllTy :: TyVar -> Type -> Type
453 = mkForAllTys [tyvar] ty
455 mkForAllTys :: [TyVar] -> Type -> Type
456 mkForAllTys tyvars ty = foldr ForAllTy ty tyvars
458 isForAllTy :: Type -> Bool
459 isForAllTy (NoteTy _ ty) = isForAllTy ty
460 isForAllTy (ForAllTy _ _) = True
461 isForAllTy other_ty = False
463 splitForAllTy_maybe :: Type -> Maybe (TyVar, Type)
464 splitForAllTy_maybe ty = splitFAT_m ty
466 splitFAT_m (NoteTy _ ty) = splitFAT_m ty
467 splitFAT_m (PredTy p) = splitFAT_m (predTypeRep p)
468 splitFAT_m (NewTcApp tc tys) = splitFAT_m (newTypeRep tc tys)
469 splitFAT_m (ForAllTy tyvar ty) = Just(tyvar, ty)
470 splitFAT_m _ = Nothing
472 splitForAllTys :: Type -> ([TyVar], Type)
473 splitForAllTys ty = split ty ty []
475 split orig_ty (ForAllTy tv ty) tvs = split ty ty (tv:tvs)
476 split orig_ty (NoteTy _ ty) tvs = split orig_ty ty tvs
477 split orig_ty (PredTy p) tvs = split orig_ty (predTypeRep p) tvs
478 split orig_ty (NewTcApp tc tys) tvs = split orig_ty (newTypeRep tc tys) tvs
479 split orig_ty t tvs = (reverse tvs, orig_ty)
481 dropForAlls :: Type -> Type
482 dropForAlls ty = snd (splitForAllTys ty)
485 -- (mkPiType now in CoreUtils)
489 Instantiate a for-all type with one or more type arguments.
490 Used when we have a polymorphic function applied to type args:
492 Then we use (applyTys type-of-f [t1,t2]) to compute the type of
496 applyTy :: Type -> Type -> Type
497 applyTy (PredTy p) arg = applyTy (predTypeRep p) arg
498 applyTy (NewTcApp tc tys) arg = applyTy (newTypeRep tc tys) arg
499 applyTy (NoteTy _ fun) arg = applyTy fun arg
500 applyTy (ForAllTy tv ty) arg = substTyWith [tv] [arg] ty
501 applyTy other arg = panic "applyTy"
503 applyTys :: Type -> [Type] -> Type
504 -- This function is interesting because
505 -- a) the function may have more for-alls than there are args
506 -- b) less obviously, it may have fewer for-alls
507 -- For case (b) think of
508 -- applyTys (forall a.a) [forall b.b, Int]
509 -- This really can happen, via dressing up polymorphic types with newtype
510 -- clothing. Here's an example:
511 -- newtype R = R (forall a. a->a)
512 -- foo = case undefined :: R of
515 applyTys orig_fun_ty [] = orig_fun_ty
516 applyTys orig_fun_ty arg_tys
517 | n_tvs == n_args -- The vastly common case
518 = substTyWith tvs arg_tys rho_ty
519 | n_tvs > n_args -- Too many for-alls
520 = substTyWith (take n_args tvs) arg_tys
521 (mkForAllTys (drop n_args tvs) rho_ty)
522 | otherwise -- Too many type args
523 = ASSERT2( n_tvs > 0, ppr orig_fun_ty ) -- Zero case gives infnite loop!
524 applyTys (substTyWith tvs (take n_tvs arg_tys) rho_ty)
527 (tvs, rho_ty) = splitForAllTys orig_fun_ty
529 n_args = length arg_tys
533 %************************************************************************
535 \subsection{Source types}
537 %************************************************************************
539 A "source type" is a type that is a separate type as far as the type checker is
540 concerned, but which has low-level representation as far as the back end is concerned.
542 Source types are always lifted.
544 The key function is predTypeRep which gives the representation of a source type:
547 mkPredTy :: PredType -> Type
548 mkPredTy pred = PredTy pred
550 mkPredTys :: ThetaType -> [Type]
551 mkPredTys preds = map PredTy preds
553 predTypeRep :: PredType -> Type
554 -- Convert a PredType to its "representation type";
555 -- the post-type-checking type used by all the Core passes of GHC.
556 predTypeRep (IParam _ ty) = ty
557 predTypeRep (ClassP clas tys) = mkTyConApp (classTyCon clas) tys
558 -- Result might be a NewTcApp, but the consumer will
559 -- look through that too if necessary
563 %************************************************************************
567 %************************************************************************
570 splitRecNewType_maybe :: Type -> Maybe Type
571 -- Newtypes are always represented by a NewTcApp
572 -- Sometimes we want to look through a recursive newtype, and that's what happens here
573 -- Only applied to types of kind *, hence the newtype is always saturated
574 splitRecNewType_maybe (NoteTy _ ty) = splitRecNewType_maybe ty
575 splitRecNewType_maybe (NewTcApp tc tys)
576 | isRecursiveTyCon tc
577 = ASSERT( tys `lengthIs` tyConArity tc && isNewTyCon tc )
578 -- The assert should hold because repType should
579 -- only be applied to *types* (of kind *)
580 Just (new_type_rep tc tys)
581 splitRecNewType_maybe other = Nothing
583 -----------------------------
584 newTypeRep :: TyCon -> [Type] -> Type
585 -- A local helper function (not exported)
586 -- Expands a newtype application to
587 -- *either* a vanilla TyConApp (recursive newtype, or non-saturated)
588 -- *or* the newtype representation (otherwise)
589 -- Either way, the result is not a NewTcApp
591 -- NB: the returned TyConApp is always deconstructed immediately by the
592 -- caller... a TyConApp with a newtype type constructor never lives
593 -- in an ordinary type
595 | not (isRecursiveTyCon tc), -- Not recursive and saturated
596 tys `lengthIs` tyConArity tc -- treat as equivalent to expansion
597 = new_type_rep tc tys
600 -- ToDo: Consider caching this substitution in a NType
602 ----------------------------
603 -- new_type_rep doesn't ask any questions:
604 -- it just expands newtype, whether recursive or not
605 new_type_rep new_tycon tys = ASSERT( tys `lengthIs` tyConArity new_tycon )
606 case newTyConRep new_tycon of
607 (tvs, rep_ty) -> substTyWith tvs tys rep_ty
611 %************************************************************************
613 \subsection{Kinds and free variables}
615 %************************************************************************
617 ---------------------------------------------------------------------
618 Finding the kind of a type
619 ~~~~~~~~~~~~~~~~~~~~~~~~~~
621 typeKind :: Type -> Kind
623 typeKind (TyVarTy tyvar) = tyVarKind tyvar
624 typeKind (TyConApp tycon tys) = foldr (\_ k -> funResultTy k) (tyConKind tycon) tys
625 typeKind (NewTcApp tycon tys) = foldr (\_ k -> funResultTy k) (tyConKind tycon) tys
626 typeKind (NoteTy _ ty) = typeKind ty
627 typeKind (PredTy _) = liftedTypeKind -- Predicates are always
628 -- represented by lifted types
629 typeKind (AppTy fun arg) = funResultTy (typeKind fun)
631 typeKind (FunTy arg res) = fix_up (typeKind res)
633 fix_up (TyConApp tycon _) | tycon == typeCon
634 || tycon == openKindCon = liftedTypeKind
635 fix_up (NoteTy _ kind) = fix_up kind
637 -- The basic story is
638 -- typeKind (FunTy arg res) = typeKind res
639 -- But a function is lifted regardless of its result type
640 -- Hence the strange fix-up.
641 -- Note that 'res', being the result of a FunTy, can't have
642 -- a strange kind like (*->*).
644 typeKind (ForAllTy tv ty) = typeKind ty
648 ---------------------------------------------------------------------
649 Free variables of a type
650 ~~~~~~~~~~~~~~~~~~~~~~~~
652 tyVarsOfType :: Type -> TyVarSet
653 tyVarsOfType (TyVarTy tv) = unitVarSet tv
654 tyVarsOfType (TyConApp tycon tys) = tyVarsOfTypes tys
655 tyVarsOfType (NewTcApp tycon tys) = tyVarsOfTypes tys
656 tyVarsOfType (NoteTy (FTVNote tvs) ty2) = tvs
657 tyVarsOfType (NoteTy (SynNote ty1) ty2) = tyVarsOfType ty2 -- See note [Syn] below
658 tyVarsOfType (PredTy sty) = tyVarsOfPred sty
659 tyVarsOfType (FunTy arg res) = tyVarsOfType arg `unionVarSet` tyVarsOfType res
660 tyVarsOfType (AppTy fun arg) = tyVarsOfType fun `unionVarSet` tyVarsOfType arg
661 tyVarsOfType (ForAllTy tyvar ty) = tyVarsOfType ty `minusVarSet` unitVarSet tyvar
666 -- What are the free tyvars of (T x)? Empty, of course!
667 -- Here's the example that Ralf Laemmel showed me:
668 -- foo :: (forall a. C u a -> C u a) -> u
669 -- mappend :: Monoid u => u -> u -> u
671 -- bar :: Monoid u => u
672 -- bar = foo (\t -> t `mappend` t)
673 -- We have to generalise at the arg to f, and we don't
674 -- want to capture the constraint (Monad (C u a)) because
675 -- it appears to mention a. Pretty silly, but it was useful to him.
678 tyVarsOfTypes :: [Type] -> TyVarSet
679 tyVarsOfTypes tys = foldr (unionVarSet.tyVarsOfType) emptyVarSet tys
681 tyVarsOfPred :: PredType -> TyVarSet
682 tyVarsOfPred (IParam _ ty) = tyVarsOfType ty
683 tyVarsOfPred (ClassP _ tys) = tyVarsOfTypes tys
685 tyVarsOfTheta :: ThetaType -> TyVarSet
686 tyVarsOfTheta = foldr (unionVarSet . tyVarsOfPred) emptyVarSet
688 -- Add a Note with the free tyvars to the top of the type
689 addFreeTyVars :: Type -> Type
690 addFreeTyVars ty@(NoteTy (FTVNote _) _) = ty
691 addFreeTyVars ty = NoteTy (FTVNote (tyVarsOfType ty)) ty
694 %************************************************************************
696 \subsection{TidyType}
698 %************************************************************************
700 tidyTy tidies up a type for printing in an error message, or in
703 It doesn't change the uniques at all, just the print names.
706 tidyTyVarBndr :: TidyEnv -> TyVar -> (TidyEnv, TyVar)
707 tidyTyVarBndr (tidy_env, subst) tyvar
708 = case tidyOccName tidy_env (getOccName name) of
709 (tidy', occ') -> -- New occname reqd
710 ((tidy', subst'), tyvar')
712 subst' = extendVarEnv subst tyvar tyvar'
713 tyvar' = setTyVarName tyvar name'
714 name' = mkInternalName (getUnique name) occ' noSrcLoc
715 -- Note: make a *user* tyvar, so it printes nicely
716 -- Could extract src loc, but no need.
718 name = tyVarName tyvar
720 tidyFreeTyVars :: TidyEnv -> TyVarSet -> TidyEnv
721 -- Add the free tyvars to the env in tidy form,
722 -- so that we can tidy the type they are free in
723 tidyFreeTyVars env tyvars = fst (tidyOpenTyVars env (varSetElems tyvars))
725 tidyOpenTyVars :: TidyEnv -> [TyVar] -> (TidyEnv, [TyVar])
726 tidyOpenTyVars env tyvars = mapAccumL tidyOpenTyVar env tyvars
728 tidyOpenTyVar :: TidyEnv -> TyVar -> (TidyEnv, TyVar)
729 -- Treat a new tyvar as a binder, and give it a fresh tidy name
730 tidyOpenTyVar env@(tidy_env, subst) tyvar
731 = case lookupVarEnv subst tyvar of
732 Just tyvar' -> (env, tyvar') -- Already substituted
733 Nothing -> tidyTyVarBndr env tyvar -- Treat it as a binder
735 tidyType :: TidyEnv -> Type -> Type
736 tidyType env@(tidy_env, subst) ty
739 go (TyVarTy tv) = case lookupVarEnv subst tv of
740 Nothing -> TyVarTy tv
741 Just tv' -> TyVarTy tv'
742 go (TyConApp tycon tys) = let args = map go tys
743 in args `seqList` TyConApp tycon args
744 go (NewTcApp tycon tys) = let args = map go tys
745 in args `seqList` NewTcApp tycon args
746 go (NoteTy note ty) = (NoteTy $! (go_note note)) $! (go ty)
747 go (PredTy sty) = PredTy (tidyPred env sty)
748 go (AppTy fun arg) = (AppTy $! (go fun)) $! (go arg)
749 go (FunTy fun arg) = (FunTy $! (go fun)) $! (go arg)
750 go (ForAllTy tv ty) = ForAllTy tvp $! (tidyType envp ty)
752 (envp, tvp) = tidyTyVarBndr env tv
754 go_note (SynNote ty) = SynNote $! (go ty)
755 go_note note@(FTVNote ftvs) = note -- No need to tidy the free tyvars
757 tidyTypes env tys = map (tidyType env) tys
759 tidyPred :: TidyEnv -> PredType -> PredType
760 tidyPred env (IParam n ty) = IParam n (tidyType env ty)
761 tidyPred env (ClassP clas tys) = ClassP clas (tidyTypes env tys)
765 @tidyOpenType@ grabs the free type variables, tidies them
766 and then uses @tidyType@ to work over the type itself
769 tidyOpenType :: TidyEnv -> Type -> (TidyEnv, Type)
771 = (env', tidyType env' ty)
773 env' = tidyFreeTyVars env (tyVarsOfType ty)
775 tidyOpenTypes :: TidyEnv -> [Type] -> (TidyEnv, [Type])
776 tidyOpenTypes env tys = mapAccumL tidyOpenType env tys
778 tidyTopType :: Type -> Type
779 tidyTopType ty = tidyType emptyTidyEnv ty
784 %************************************************************************
786 \subsection{Liftedness}
788 %************************************************************************
791 isUnLiftedType :: Type -> Bool
792 -- isUnLiftedType returns True for forall'd unlifted types:
793 -- x :: forall a. Int#
794 -- I found bindings like these were getting floated to the top level.
795 -- They are pretty bogus types, mind you. It would be better never to
798 isUnLiftedType (ForAllTy tv ty) = isUnLiftedType ty
799 isUnLiftedType (NoteTy _ ty) = isUnLiftedType ty
800 isUnLiftedType (TyConApp tc _) = isUnLiftedTyCon tc
801 isUnLiftedType (PredTy _) = False -- All source types are lifted
802 isUnLiftedType (NewTcApp tc tys) = isUnLiftedType (newTypeRep tc tys)
803 isUnLiftedType other = False
805 isUnboxedTupleType :: Type -> Bool
806 isUnboxedTupleType ty = case splitTyConApp_maybe ty of
807 Just (tc, ty_args) -> isUnboxedTupleTyCon tc
810 -- Should only be applied to *types*; hence the assert
811 isAlgType :: Type -> Bool
812 isAlgType ty = case splitTyConApp_maybe ty of
813 Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc )
818 @isStrictType@ computes whether an argument (or let RHS) should
819 be computed strictly or lazily, based only on its type.
820 Works just like isUnLiftedType, except that it has a special case
821 for dictionaries. Since it takes account of ClassP, you might think
822 this function should be in TcType, but isStrictType is used by DataCon,
823 which is below TcType in the hierarchy, so it's convenient to put it here.
826 isStrictType (ForAllTy tv ty) = isStrictType ty
827 isStrictType (NoteTy _ ty) = isStrictType ty
828 isStrictType (TyConApp tc _) = isUnLiftedTyCon tc
829 isStrictType (NewTcApp tc tys) = isStrictType (newTypeRep tc tys)
830 isStrictType (PredTy pred) = isStrictPred pred
831 isStrictType other = False
833 isStrictPred (ClassP clas _) = opt_DictsStrict && not (isNewTyCon (classTyCon clas))
834 isStrictPred other = False
835 -- We may be strict in dictionary types, but only if it
836 -- has more than one component.
837 -- [Being strict in a single-component dictionary risks
838 -- poking the dictionary component, which is wrong.]
842 isPrimitiveType :: Type -> Bool
843 -- Returns types that are opaque to Haskell.
844 -- Most of these are unlifted, but now that we interact with .NET, we
845 -- may have primtive (foreign-imported) types that are lifted
846 isPrimitiveType ty = case splitTyConApp_maybe ty of
847 Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc )
853 %************************************************************************
855 \subsection{Sequencing on types
857 %************************************************************************
860 seqType :: Type -> ()
861 seqType (TyVarTy tv) = tv `seq` ()
862 seqType (AppTy t1 t2) = seqType t1 `seq` seqType t2
863 seqType (FunTy t1 t2) = seqType t1 `seq` seqType t2
864 seqType (NoteTy note t2) = seqNote note `seq` seqType t2
865 seqType (PredTy p) = seqPred p
866 seqType (TyConApp tc tys) = tc `seq` seqTypes tys
867 seqType (NewTcApp tc tys) = tc `seq` seqTypes tys
868 seqType (ForAllTy tv ty) = tv `seq` seqType ty
870 seqTypes :: [Type] -> ()
872 seqTypes (ty:tys) = seqType ty `seq` seqTypes tys
874 seqNote :: TyNote -> ()
875 seqNote (SynNote ty) = seqType ty
876 seqNote (FTVNote set) = sizeUniqSet set `seq` ()
878 seqPred :: PredType -> ()
879 seqPred (ClassP c tys) = c `seq` seqTypes tys
880 seqPred (IParam n ty) = n `seq` seqType ty
884 %************************************************************************
886 \subsection{Equality on types}
888 %************************************************************************
890 Comparison; don't use instances so that we know where it happens.
891 Look through newtypes but not usage types.
893 Note that eqType can respond 'False' for partial applications of newtypes.
895 newtype Parser m a = MkParser (Foogle m a)
898 Monad (Parser m) `eqType` Monad (Foogle m)
900 Well, yes, but eqType won't see that they are the same.
901 I don't think this is harmful, but it's soemthing to watch out for.
904 eqType t1 t2 = eq_ty emptyVarEnv t1 t2
905 eqKind = eqType -- No worries about looking
907 -- Look through Notes
908 eq_ty env (NoteTy _ t1) t2 = eq_ty env t1 t2
909 eq_ty env t1 (NoteTy _ t2) = eq_ty env t1 t2
911 -- Look through PredTy and NewTcApp. This is where the looping danger comes from.
912 -- We don't bother to check for the PredType/PredType case, no good reason
913 -- Hmm: maybe there is a good reason: see the notes below about newtypes
914 eq_ty env (PredTy sty1) t2 = eq_ty env (predTypeRep sty1) t2
915 eq_ty env t1 (PredTy sty2) = eq_ty env t1 (predTypeRep sty2)
917 -- NB: we *cannot* short-cut the newtype comparison thus:
918 -- eq_ty env (NewTcApp tc1 tys1) (NewTcApp tc2 tys2)
919 -- | (tc1 == tc2) = (eq_tys env tys1 tys2)
922 -- newtype T a = MkT [a]
923 -- newtype Foo m = MkFoo (forall a. m a -> Int)
928 -- w2 = MkFoo (\(MkT x) -> case w1 of MkFoo f -> f x)
930 -- We end up with w2 = w1; so we need that Foo T = Foo []
931 -- but we can only expand saturated newtypes, so just comparing
932 -- T with [] won't do.
934 eq_ty env (NewTcApp tc1 tys1) t2 = eq_ty env (newTypeRep tc1 tys1) t2
935 eq_ty env t1 (NewTcApp tc2 tys2) = eq_ty env t1 (newTypeRep tc2 tys2)
937 -- The rest is plain sailing
938 eq_ty env (TyVarTy tv1) (TyVarTy tv2) = case lookupVarEnv env tv1 of
939 Just tv1a -> tv1a == tv2
940 Nothing -> tv1 == tv2
941 eq_ty env (ForAllTy tv1 t1) (ForAllTy tv2 t2)
942 | tv1 == tv2 = eq_ty (delVarEnv env tv1) t1 t2
943 | otherwise = eq_ty (extendVarEnv env tv1 tv2) t1 t2
944 eq_ty env (AppTy s1 t1) (AppTy s2 t2) = (eq_ty env s1 s2) && (eq_ty env t1 t2)
945 eq_ty env (FunTy s1 t1) (FunTy s2 t2) = (eq_ty env s1 s2) && (eq_ty env t1 t2)
946 eq_ty env (TyConApp tc1 tys1) (TyConApp tc2 tys2) = (tc1 == tc2) && (eq_tys env tys1 tys2)
947 eq_ty env t1 t2 = False
949 eq_tys env [] [] = True
950 eq_tys env (t1:tys1) (t2:tys2) = (eq_ty env t1 t2) && (eq_tys env tys1 tys2)
951 eq_tys env tys1 tys2 = False