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,
72 #include "HsVersions.h"
74 -- We import the representation and primitive functions from TypeRep.
75 -- Many things are reexported, but not the representation!
81 import {-# SOURCE #-} Subst ( substTyWith )
84 import Var ( TyVar, tyVarKind, tyVarName, setTyVarName )
88 import Name ( NamedThing(..), mkInternalName, tidyOccName )
89 import Class ( Class, classTyCon )
90 import TyCon ( TyCon, isRecursiveTyCon, isPrimTyCon,
91 isUnboxedTupleTyCon, isUnLiftedTyCon,
92 isFunTyCon, isNewTyCon, newTyConRep,
93 isAlgTyCon, isSynTyCon, tyConArity,
94 tyConKind, getSynTyConDefn,
99 import CmdLineOpts ( opt_DictsStrict )
100 import SrcLoc ( noSrcLoc )
101 import PrimRep ( PrimRep(..) )
102 import Unique ( Uniquable(..) )
103 import Util ( mapAccumL, seqList, lengthIs, snocView )
105 import UniqSet ( sizeUniqSet ) -- Should come via VarSet
106 import Maybe ( isJust )
110 %************************************************************************
112 \subsection{Stuff to do with kinds.}
114 %************************************************************************
117 hasMoreBoxityInfo :: Kind -> Kind -> Bool
118 -- (k1 `hasMoreBoxityInfo` k2) checks that k1 <: k2
119 hasMoreBoxityInfo k1 k2
120 | k2 `eqKind` openTypeKind = isAnyTypeKind k1
121 | otherwise = k1 `eqKind` k2
123 isAnyTypeKind :: Kind -> Bool
124 -- True of kind * and *# and ?
125 isAnyTypeKind (TyConApp tc _) = tc == typeCon || tc == openKindCon
126 isAnyTypeKind (NoteTy _ k) = isAnyTypeKind k
127 isAnyTypeKind other = False
129 isTypeKind :: Kind -> Bool
130 -- True of kind * and *#
131 isTypeKind (TyConApp tc _) = tc == typeCon
132 isTypeKind (NoteTy _ k) = isTypeKind k
133 isTypeKind other = False
135 defaultKind :: Kind -> Kind
136 -- Used when generalising: default kind '?' to '*'
137 defaultKind kind | kind `eqKind` openTypeKind = liftedTypeKind
142 %************************************************************************
144 \subsection{Constructor-specific functions}
146 %************************************************************************
149 ---------------------------------------------------------------------
153 mkTyVarTy :: TyVar -> Type
156 mkTyVarTys :: [TyVar] -> [Type]
157 mkTyVarTys = map mkTyVarTy -- a common use of mkTyVarTy
159 getTyVar :: String -> Type -> TyVar
160 getTyVar msg ty = case getTyVar_maybe ty of
162 Nothing -> panic ("getTyVar: " ++ msg)
164 isTyVarTy :: Type -> Bool
165 isTyVarTy ty = isJust (getTyVar_maybe ty)
167 getTyVar_maybe :: Type -> Maybe TyVar
168 getTyVar_maybe (TyVarTy tv) = Just tv
169 getTyVar_maybe (NoteTy _ t) = getTyVar_maybe t
170 getTyVar_maybe (PredTy p) = getTyVar_maybe (predTypeRep p)
171 getTyVar_maybe (NewTcApp tc tys) = getTyVar_maybe (newTypeRep tc tys)
172 getTyVar_maybe other = Nothing
176 ---------------------------------------------------------------------
179 We need to be pretty careful with AppTy to make sure we obey the
180 invariant that a TyConApp is always visibly so. mkAppTy maintains the
184 mkAppTy orig_ty1 orig_ty2
187 mk_app (NoteTy _ ty1) = mk_app ty1
188 mk_app (NewTcApp tc tys) = NewTcApp tc (tys ++ [orig_ty2])
189 mk_app (TyConApp tc tys) = mkGenTyConApp tc (tys ++ [orig_ty2])
190 mk_app ty1 = AppTy orig_ty1 orig_ty2
191 -- We call mkGenTyConApp because the TyConApp could be an
192 -- under-saturated type synonym. GHC allows that; e.g.
193 -- type Foo k = k a -> k a
195 -- foo :: Foo Id -> Foo Id
197 -- Here Id is partially applied in the type sig for Foo,
198 -- but once the type synonyms are expanded all is well
200 mkAppTys :: Type -> [Type] -> Type
201 mkAppTys orig_ty1 [] = orig_ty1
202 -- This check for an empty list of type arguments
203 -- avoids the needless loss of a type synonym constructor.
204 -- For example: mkAppTys Rational []
205 -- returns to (Ratio Integer), which has needlessly lost
206 -- the Rational part.
207 mkAppTys orig_ty1 orig_tys2
210 mk_app (NoteTy _ ty1) = mk_app ty1
211 mk_app (NewTcApp tc tys) = NewTcApp tc (tys ++ orig_tys2)
212 mk_app (TyConApp tc tys) = mkTyConApp tc (tys ++ orig_tys2)
213 -- Use mkTyConApp in case tc is (->)
214 mk_app ty1 = foldl AppTy orig_ty1 orig_tys2
216 splitAppTy_maybe :: Type -> Maybe (Type, Type)
217 splitAppTy_maybe (FunTy ty1 ty2) = Just (TyConApp funTyCon [ty1], ty2)
218 splitAppTy_maybe (AppTy ty1 ty2) = Just (ty1, ty2)
219 splitAppTy_maybe (NoteTy _ ty) = splitAppTy_maybe ty
220 splitAppTy_maybe (PredTy p) = splitAppTy_maybe (predTypeRep p)
221 splitAppTy_maybe (NewTcApp tc tys) = splitAppTy_maybe (newTypeRep tc tys)
222 splitAppTy_maybe (TyConApp tc tys) = case snocView tys of
224 Just (tys',ty') -> Just (mkGenTyConApp tc tys', ty')
225 -- mkGenTyConApp just in case the tc is a newtype
227 splitAppTy_maybe other = Nothing
229 splitAppTy :: Type -> (Type, Type)
230 splitAppTy ty = case splitAppTy_maybe ty of
232 Nothing -> panic "splitAppTy"
234 splitAppTys :: Type -> (Type, [Type])
235 splitAppTys ty = split ty ty []
237 split orig_ty (AppTy ty arg) args = split ty ty (arg:args)
238 split orig_ty (NoteTy _ ty) args = split orig_ty ty args
239 split orig_ty (PredTy p) args = split orig_ty (predTypeRep p) args
240 split orig_ty (NewTcApp tc tc_args) args = split orig_ty (newTypeRep tc tc_args) args
241 split orig_ty (TyConApp tc tc_args) args = (mkGenTyConApp tc [], tc_args ++ args)
242 -- mkGenTyConApp just in case the tc is a newtype
243 split orig_ty (FunTy ty1 ty2) args = ASSERT( null args )
244 (TyConApp funTyCon [], [ty1,ty2])
245 split orig_ty ty args = (orig_ty, args)
249 ---------------------------------------------------------------------
254 mkFunTy :: Type -> Type -> Type
255 mkFunTy arg res = FunTy arg res
257 mkFunTys :: [Type] -> Type -> Type
258 mkFunTys tys ty = foldr FunTy ty tys
260 isFunTy :: Type -> Bool
261 isFunTy ty = isJust (splitFunTy_maybe ty)
263 splitFunTy :: Type -> (Type, Type)
264 splitFunTy (FunTy arg res) = (arg, res)
265 splitFunTy (NoteTy _ ty) = splitFunTy ty
266 splitFunTy (PredTy p) = splitFunTy (predTypeRep p)
267 splitFunTy (NewTcApp tc tys) = splitFunTy (newTypeRep tc tys)
268 splitFunTy other = pprPanic "splitFunTy" (crudePprType other)
270 splitFunTy_maybe :: Type -> Maybe (Type, Type)
271 splitFunTy_maybe (FunTy arg res) = Just (arg, res)
272 splitFunTy_maybe (NoteTy _ ty) = splitFunTy_maybe ty
273 splitFunTy_maybe (PredTy p) = splitFunTy_maybe (predTypeRep p)
274 splitFunTy_maybe (NewTcApp tc tys) = splitFunTy_maybe (newTypeRep tc tys)
275 splitFunTy_maybe other = Nothing
277 splitFunTys :: Type -> ([Type], Type)
278 splitFunTys ty = split [] ty ty
280 split args orig_ty (FunTy arg res) = split (arg:args) res res
281 split args orig_ty (NoteTy _ ty) = split args orig_ty ty
282 split args orig_ty (PredTy p) = split args orig_ty (predTypeRep p)
283 split args orig_ty (NewTcApp tc tys) = split args orig_ty (newTypeRep tc tys)
284 split args orig_ty ty = (reverse args, orig_ty)
286 zipFunTys :: Outputable a => [a] -> Type -> ([(a,Type)], Type)
287 zipFunTys orig_xs orig_ty = split [] orig_xs orig_ty orig_ty
289 split acc [] nty ty = (reverse acc, nty)
290 split acc (x:xs) nty (FunTy arg res) = split ((x,arg):acc) xs res res
291 split acc xs nty (NoteTy _ ty) = split acc xs nty ty
292 split acc xs nty (PredTy p) = split acc xs nty (predTypeRep p)
293 split acc xs nty (NewTcApp tc tys) = split acc xs nty (newTypeRep tc tys)
294 split acc (x:xs) nty ty = pprPanic "zipFunTys" (ppr orig_xs <+> crudePprType orig_ty)
296 funResultTy :: Type -> Type
297 funResultTy (FunTy arg res) = res
298 funResultTy (NoteTy _ ty) = funResultTy ty
299 funResultTy (PredTy p) = funResultTy (predTypeRep p)
300 funResultTy (NewTcApp tc tys) = funResultTy (newTypeRep tc tys)
301 funResultTy ty = pprPanic "funResultTy" (crudePprType ty)
303 funArgTy :: Type -> Type
304 funArgTy (FunTy arg res) = arg
305 funArgTy (NoteTy _ ty) = funArgTy ty
306 funArgTy (PredTy p) = funArgTy (predTypeRep p)
307 funArgTy (NewTcApp tc tys) = funArgTy (newTypeRep tc tys)
308 funArgTy ty = pprPanic "funArgTy" (crudePprType ty)
312 ---------------------------------------------------------------------
315 @mkTyConApp@ is a key function, because it builds a TyConApp, FunTy or PredTy,
319 mkGenTyConApp :: TyCon -> [Type] -> Type
321 | isSynTyCon tc = mkSynTy tc tys
322 | otherwise = mkTyConApp tc tys
324 mkTyConApp :: TyCon -> [Type] -> Type
325 -- Assumes TyCon is not a SynTyCon; use mkSynTy instead for those
327 | isFunTyCon tycon, [ty1,ty2] <- tys
334 = ASSERT(not (isSynTyCon tycon))
337 mkTyConTy :: TyCon -> Type
338 mkTyConTy tycon = mkTyConApp tycon []
340 -- splitTyConApp "looks through" synonyms, because they don't
341 -- mean a distinct type, but all other type-constructor applications
342 -- including functions are returned as Just ..
344 tyConAppTyCon :: Type -> TyCon
345 tyConAppTyCon ty = fst (splitTyConApp ty)
347 tyConAppArgs :: Type -> [Type]
348 tyConAppArgs ty = snd (splitTyConApp ty)
350 splitTyConApp :: Type -> (TyCon, [Type])
351 splitTyConApp ty = case splitTyConApp_maybe ty of
353 Nothing -> pprPanic "splitTyConApp" (crudePprType ty)
355 splitTyConApp_maybe :: Type -> Maybe (TyCon, [Type])
356 splitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
357 splitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res])
358 splitTyConApp_maybe (NoteTy _ ty) = splitTyConApp_maybe ty
359 splitTyConApp_maybe (PredTy p) = splitTyConApp_maybe (predTypeRep p)
360 splitTyConApp_maybe (NewTcApp tc tys) = splitTyConApp_maybe (newTypeRep tc tys)
361 splitTyConApp_maybe other = Nothing
365 ---------------------------------------------------------------------
371 | n_args == arity -- Exactly saturated
373 | n_args > arity -- Over-saturated
374 = case splitAt arity tys of { (as,bs) -> mkAppTys (mk_syn as) bs }
375 -- Its important to use mkAppTys, rather than (foldl AppTy),
376 -- because (mk_syn as) might well return a partially-applied
377 -- type constructor; indeed, usually will!
378 | otherwise -- Un-saturated
380 -- For the un-saturated case we build TyConApp directly
381 -- (mkTyConApp ASSERTs that the tc isn't a SynTyCon).
382 -- Here we are relying on checkValidType to find
383 -- the error. What we can't do is use mkSynTy with
384 -- too few arg tys, because that is utterly bogus.
387 mk_syn tys = NoteTy (SynNote (TyConApp tycon tys))
388 (substTyWith tyvars tys body)
390 (tyvars, body) = ASSERT( isSynTyCon tycon ) getSynTyConDefn tycon
391 arity = tyConArity tycon
395 Notes on type synonyms
396 ~~~~~~~~~~~~~~~~~~~~~~
397 The various "split" functions (splitFunTy, splitRhoTy, splitForAllTy) try
398 to return type synonyms whereever possible. Thus
403 splitFunTys (a -> Foo a) = ([a], Foo a)
406 The reason is that we then get better (shorter) type signatures in
407 interfaces. Notably this plays a role in tcTySigs in TcBinds.lhs.
412 repType looks through
416 (d) usage annotations
417 (e) [recursive] newtypes
418 It's useful in the back end.
421 repType :: Type -> Type
422 -- Only applied to types of kind *; hence tycons are saturated
423 repType (ForAllTy _ ty) = repType ty
424 repType (NoteTy _ ty) = repType ty
425 repType (PredTy p) = repType (predTypeRep p)
426 repType (NewTcApp tc tys) = ASSERT( tys `lengthIs` tyConArity tc )
427 repType (new_type_rep tc tys)
431 typePrimRep :: Type -> PrimRep
432 typePrimRep ty = case repType ty of
433 TyConApp tc _ -> tyConPrimRep tc
435 AppTy _ _ -> PtrRep -- ??
437 other -> pprPanic "typePrimRep" (crudePprType ty)
442 ---------------------------------------------------------------------
447 mkForAllTy :: TyVar -> Type -> Type
449 = mkForAllTys [tyvar] ty
451 mkForAllTys :: [TyVar] -> Type -> Type
452 mkForAllTys tyvars ty = foldr ForAllTy ty tyvars
454 isForAllTy :: Type -> Bool
455 isForAllTy (NoteTy _ ty) = isForAllTy ty
456 isForAllTy (ForAllTy _ _) = True
457 isForAllTy other_ty = False
459 splitForAllTy_maybe :: Type -> Maybe (TyVar, Type)
460 splitForAllTy_maybe ty = splitFAT_m ty
462 splitFAT_m (NoteTy _ ty) = splitFAT_m ty
463 splitFAT_m (PredTy p) = splitFAT_m (predTypeRep p)
464 splitFAT_m (NewTcApp tc tys) = splitFAT_m (newTypeRep tc tys)
465 splitFAT_m (ForAllTy tyvar ty) = Just(tyvar, ty)
466 splitFAT_m _ = Nothing
468 splitForAllTys :: Type -> ([TyVar], Type)
469 splitForAllTys ty = split ty ty []
471 split orig_ty (ForAllTy tv ty) tvs = split ty ty (tv:tvs)
472 split orig_ty (NoteTy _ ty) tvs = split orig_ty ty tvs
473 split orig_ty (PredTy p) tvs = split orig_ty (predTypeRep p) tvs
474 split orig_ty (NewTcApp tc tys) tvs = split orig_ty (newTypeRep tc tys) tvs
475 split orig_ty t tvs = (reverse tvs, orig_ty)
477 dropForAlls :: Type -> Type
478 dropForAlls ty = snd (splitForAllTys ty)
481 -- (mkPiType now in CoreUtils)
485 Instantiate a for-all type with one or more type arguments.
486 Used when we have a polymorphic function applied to type args:
488 Then we use (applyTys type-of-f [t1,t2]) to compute the type of
492 applyTy :: Type -> Type -> Type
493 applyTy (PredTy p) arg = applyTy (predTypeRep p) arg
494 applyTy (NewTcApp tc tys) arg = applyTy (newTypeRep tc tys) arg
495 applyTy (NoteTy _ fun) arg = applyTy fun arg
496 applyTy (ForAllTy tv ty) arg = substTyWith [tv] [arg] ty
497 applyTy other arg = panic "applyTy"
499 applyTys :: Type -> [Type] -> Type
500 -- This function is interesting because
501 -- a) the function may have more for-alls than there are args
502 -- b) less obviously, it may have fewer for-alls
503 -- For case (b) think of
504 -- applyTys (forall a.a) [forall b.b, Int]
505 -- This really can happen, via dressing up polymorphic types with newtype
506 -- clothing. Here's an example:
507 -- newtype R = R (forall a. a->a)
508 -- foo = case undefined :: R of
511 applyTys orig_fun_ty [] = orig_fun_ty
512 applyTys orig_fun_ty arg_tys
513 | n_tvs == n_args -- The vastly common case
514 = substTyWith tvs arg_tys rho_ty
515 | n_tvs > n_args -- Too many for-alls
516 = substTyWith (take n_args tvs) arg_tys
517 (mkForAllTys (drop n_args tvs) rho_ty)
518 | otherwise -- Too many type args
519 = ASSERT2( n_tvs > 0, crudePprType orig_fun_ty ) -- Zero case gives infnite loop!
520 applyTys (substTyWith tvs (take n_tvs arg_tys) rho_ty)
523 (tvs, rho_ty) = splitForAllTys orig_fun_ty
525 n_args = length arg_tys
529 %************************************************************************
531 \subsection{Source types}
533 %************************************************************************
535 A "source type" is a type that is a separate type as far as the type checker is
536 concerned, but which has low-level representation as far as the back end is concerned.
538 Source types are always lifted.
540 The key function is predTypeRep which gives the representation of a source type:
543 mkPredTy :: PredType -> Type
544 mkPredTy pred = PredTy pred
546 mkPredTys :: ThetaType -> [Type]
547 mkPredTys preds = map PredTy preds
549 predTypeRep :: PredType -> Type
550 -- Convert a PredType to its "representation type";
551 -- the post-type-checking type used by all the Core passes of GHC.
552 predTypeRep (IParam _ ty) = ty
553 predTypeRep (ClassP clas tys) = mkTyConApp (classTyCon clas) tys
554 -- Result might be a NewTcApp, but the consumer will
555 -- look through that too if necessary
559 %************************************************************************
563 %************************************************************************
566 splitRecNewType_maybe :: Type -> Maybe Type
567 -- Newtypes are always represented by a NewTcApp
568 -- Sometimes we want to look through a recursive newtype, and that's what happens here
569 -- Only applied to types of kind *, hence the newtype is always saturated
570 splitRecNewType_maybe (NoteTy _ ty) = splitRecNewType_maybe ty
571 splitRecNewType_maybe (NewTcApp tc tys)
572 | isRecursiveTyCon tc
573 = ASSERT( tys `lengthIs` tyConArity tc && isNewTyCon tc )
574 -- The assert should hold because repType should
575 -- only be applied to *types* (of kind *)
576 Just (new_type_rep tc tys)
577 splitRecNewType_maybe other = Nothing
579 -----------------------------
580 newTypeRep :: TyCon -> [Type] -> Type
581 -- A local helper function (not exported)
582 -- Expands a newtype application to
583 -- *either* a vanilla TyConApp (recursive newtype, or non-saturated)
584 -- *or* the newtype representation (otherwise)
585 -- Either way, the result is not a NewTcApp
587 -- NB: the returned TyConApp is always deconstructed immediately by the
588 -- caller... a TyConApp with a newtype type constructor never lives
589 -- in an ordinary type
591 | not (isRecursiveTyCon tc), -- Not recursive and saturated
592 tys `lengthIs` tyConArity tc -- treat as equivalent to expansion
593 = new_type_rep tc tys
596 -- ToDo: Consider caching this substitution in a NType
598 ----------------------------
599 -- new_type_rep doesn't ask any questions:
600 -- it just expands newtype, whether recursive or not
601 new_type_rep new_tycon tys = ASSERT( tys `lengthIs` tyConArity new_tycon )
602 case newTyConRep new_tycon of
603 (tvs, rep_ty) -> substTyWith tvs tys rep_ty
607 %************************************************************************
609 \subsection{Kinds and free variables}
611 %************************************************************************
613 ---------------------------------------------------------------------
614 Finding the kind of a type
615 ~~~~~~~~~~~~~~~~~~~~~~~~~~
617 typeKind :: Type -> Kind
619 typeKind (TyVarTy tyvar) = tyVarKind tyvar
620 typeKind (TyConApp tycon tys) = foldr (\_ k -> funResultTy k) (tyConKind tycon) tys
621 typeKind (NewTcApp tycon tys) = foldr (\_ k -> funResultTy k) (tyConKind tycon) tys
622 typeKind (NoteTy _ ty) = typeKind ty
623 typeKind (PredTy _) = liftedTypeKind -- Predicates are always
624 -- represented by lifted types
625 typeKind (AppTy fun arg) = funResultTy (typeKind fun)
627 typeKind (FunTy arg res) = fix_up (typeKind res)
629 fix_up (TyConApp tycon _) | tycon == typeCon
630 || tycon == openKindCon = liftedTypeKind
631 fix_up (NoteTy _ kind) = fix_up kind
633 -- The basic story is
634 -- typeKind (FunTy arg res) = typeKind res
635 -- But a function is lifted regardless of its result type
636 -- Hence the strange fix-up.
637 -- Note that 'res', being the result of a FunTy, can't have
638 -- a strange kind like (*->*).
640 typeKind (ForAllTy tv ty) = typeKind ty
644 ---------------------------------------------------------------------
645 Free variables of a type
646 ~~~~~~~~~~~~~~~~~~~~~~~~
648 tyVarsOfType :: Type -> TyVarSet
649 tyVarsOfType (TyVarTy tv) = unitVarSet tv
650 tyVarsOfType (TyConApp tycon tys) = tyVarsOfTypes tys
651 tyVarsOfType (NewTcApp tycon tys) = tyVarsOfTypes tys
652 tyVarsOfType (NoteTy (FTVNote tvs) ty2) = tvs
653 tyVarsOfType (NoteTy (SynNote ty1) ty2) = tyVarsOfType ty2 -- See note [Syn] below
654 tyVarsOfType (PredTy sty) = tyVarsOfPred sty
655 tyVarsOfType (FunTy arg res) = tyVarsOfType arg `unionVarSet` tyVarsOfType res
656 tyVarsOfType (AppTy fun arg) = tyVarsOfType fun `unionVarSet` tyVarsOfType arg
657 tyVarsOfType (ForAllTy tyvar ty) = tyVarsOfType ty `minusVarSet` unitVarSet tyvar
662 -- What are the free tyvars of (T x)? Empty, of course!
663 -- Here's the example that Ralf Laemmel showed me:
664 -- foo :: (forall a. C u a -> C u a) -> u
665 -- mappend :: Monoid u => u -> u -> u
667 -- bar :: Monoid u => u
668 -- bar = foo (\t -> t `mappend` t)
669 -- We have to generalise at the arg to f, and we don't
670 -- want to capture the constraint (Monad (C u a)) because
671 -- it appears to mention a. Pretty silly, but it was useful to him.
674 tyVarsOfTypes :: [Type] -> TyVarSet
675 tyVarsOfTypes tys = foldr (unionVarSet.tyVarsOfType) emptyVarSet tys
677 tyVarsOfPred :: PredType -> TyVarSet
678 tyVarsOfPred (IParam _ ty) = tyVarsOfType ty
679 tyVarsOfPred (ClassP _ tys) = tyVarsOfTypes tys
681 tyVarsOfTheta :: ThetaType -> TyVarSet
682 tyVarsOfTheta = foldr (unionVarSet . tyVarsOfPred) emptyVarSet
684 -- Add a Note with the free tyvars to the top of the type
685 addFreeTyVars :: Type -> Type
686 addFreeTyVars ty@(NoteTy (FTVNote _) _) = ty
687 addFreeTyVars ty = NoteTy (FTVNote (tyVarsOfType ty)) ty
690 %************************************************************************
692 \subsection{TidyType}
694 %************************************************************************
696 tidyTy tidies up a type for printing in an error message, or in
699 It doesn't change the uniques at all, just the print names.
702 tidyTyVarBndr :: TidyEnv -> TyVar -> (TidyEnv, TyVar)
703 tidyTyVarBndr (tidy_env, subst) tyvar
704 = case tidyOccName tidy_env (getOccName name) of
705 (tidy', occ') -> -- New occname reqd
706 ((tidy', subst'), tyvar')
708 subst' = extendVarEnv subst tyvar tyvar'
709 tyvar' = setTyVarName tyvar name'
710 name' = mkInternalName (getUnique name) occ' noSrcLoc
711 -- Note: make a *user* tyvar, so it printes nicely
712 -- Could extract src loc, but no need.
714 name = tyVarName tyvar
716 tidyFreeTyVars :: TidyEnv -> TyVarSet -> TidyEnv
717 -- Add the free tyvars to the env in tidy form,
718 -- so that we can tidy the type they are free in
719 tidyFreeTyVars env tyvars = fst (tidyOpenTyVars env (varSetElems tyvars))
721 tidyOpenTyVars :: TidyEnv -> [TyVar] -> (TidyEnv, [TyVar])
722 tidyOpenTyVars env tyvars = mapAccumL tidyOpenTyVar env tyvars
724 tidyOpenTyVar :: TidyEnv -> TyVar -> (TidyEnv, TyVar)
725 -- Treat a new tyvar as a binder, and give it a fresh tidy name
726 tidyOpenTyVar env@(tidy_env, subst) tyvar
727 = case lookupVarEnv subst tyvar of
728 Just tyvar' -> (env, tyvar') -- Already substituted
729 Nothing -> tidyTyVarBndr env tyvar -- Treat it as a binder
731 tidyType :: TidyEnv -> Type -> Type
732 tidyType env@(tidy_env, subst) ty
735 go (TyVarTy tv) = case lookupVarEnv subst tv of
736 Nothing -> TyVarTy tv
737 Just tv' -> TyVarTy tv'
738 go (TyConApp tycon tys) = let args = map go tys
739 in args `seqList` TyConApp tycon args
740 go (NewTcApp tycon tys) = let args = map go tys
741 in args `seqList` NewTcApp tycon args
742 go (NoteTy note ty) = (NoteTy $! (go_note note)) $! (go ty)
743 go (PredTy sty) = PredTy (tidyPred env sty)
744 go (AppTy fun arg) = (AppTy $! (go fun)) $! (go arg)
745 go (FunTy fun arg) = (FunTy $! (go fun)) $! (go arg)
746 go (ForAllTy tv ty) = ForAllTy tvp $! (tidyType envp ty)
748 (envp, tvp) = tidyTyVarBndr env tv
750 go_note (SynNote ty) = SynNote $! (go ty)
751 go_note note@(FTVNote ftvs) = note -- No need to tidy the free tyvars
753 tidyTypes env tys = map (tidyType env) tys
755 tidyPred :: TidyEnv -> PredType -> PredType
756 tidyPred env (IParam n ty) = IParam n (tidyType env ty)
757 tidyPred env (ClassP clas tys) = ClassP clas (tidyTypes env tys)
761 @tidyOpenType@ grabs the free type variables, tidies them
762 and then uses @tidyType@ to work over the type itself
765 tidyOpenType :: TidyEnv -> Type -> (TidyEnv, Type)
767 = (env', tidyType env' ty)
769 env' = tidyFreeTyVars env (tyVarsOfType ty)
771 tidyOpenTypes :: TidyEnv -> [Type] -> (TidyEnv, [Type])
772 tidyOpenTypes env tys = mapAccumL tidyOpenType env tys
774 tidyTopType :: Type -> Type
775 tidyTopType ty = tidyType emptyTidyEnv ty
780 %************************************************************************
782 \subsection{Liftedness}
784 %************************************************************************
787 isUnLiftedType :: Type -> Bool
788 -- isUnLiftedType returns True for forall'd unlifted types:
789 -- x :: forall a. Int#
790 -- I found bindings like these were getting floated to the top level.
791 -- They are pretty bogus types, mind you. It would be better never to
794 isUnLiftedType (ForAllTy tv ty) = isUnLiftedType ty
795 isUnLiftedType (NoteTy _ ty) = isUnLiftedType ty
796 isUnLiftedType (TyConApp tc _) = isUnLiftedTyCon tc
797 isUnLiftedType (PredTy _) = False -- All source types are lifted
798 isUnLiftedType (NewTcApp tc tys) = isUnLiftedType (newTypeRep tc tys)
799 isUnLiftedType other = False
801 isUnboxedTupleType :: Type -> Bool
802 isUnboxedTupleType ty = case splitTyConApp_maybe ty of
803 Just (tc, ty_args) -> isUnboxedTupleTyCon tc
806 -- Should only be applied to *types*; hence the assert
807 isAlgType :: Type -> Bool
808 isAlgType ty = case splitTyConApp_maybe ty of
809 Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc )
814 @isStrictType@ computes whether an argument (or let RHS) should
815 be computed strictly or lazily, based only on its type.
816 Works just like isUnLiftedType, except that it has a special case
817 for dictionaries. Since it takes account of ClassP, you might think
818 this function should be in TcType, but isStrictType is used by DataCon,
819 which is below TcType in the hierarchy, so it's convenient to put it here.
822 isStrictType (ForAllTy tv ty) = isStrictType ty
823 isStrictType (NoteTy _ ty) = isStrictType ty
824 isStrictType (TyConApp tc _) = isUnLiftedTyCon tc
825 isStrictType (NewTcApp tc tys) = isStrictType (newTypeRep tc tys)
826 isStrictType (PredTy pred) = isStrictPred pred
827 isStrictType other = False
829 isStrictPred (ClassP clas _) = opt_DictsStrict && not (isNewTyCon (classTyCon clas))
830 isStrictPred other = False
831 -- We may be strict in dictionary types, but only if it
832 -- has more than one component.
833 -- [Being strict in a single-component dictionary risks
834 -- poking the dictionary component, which is wrong.]
838 isPrimitiveType :: Type -> Bool
839 -- Returns types that are opaque to Haskell.
840 -- Most of these are unlifted, but now that we interact with .NET, we
841 -- may have primtive (foreign-imported) types that are lifted
842 isPrimitiveType ty = case splitTyConApp_maybe ty of
843 Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc )
849 %************************************************************************
851 \subsection{Sequencing on types
853 %************************************************************************
856 seqType :: Type -> ()
857 seqType (TyVarTy tv) = tv `seq` ()
858 seqType (AppTy t1 t2) = seqType t1 `seq` seqType t2
859 seqType (FunTy t1 t2) = seqType t1 `seq` seqType t2
860 seqType (NoteTy note t2) = seqNote note `seq` seqType t2
861 seqType (PredTy p) = seqPred p
862 seqType (TyConApp tc tys) = tc `seq` seqTypes tys
863 seqType (NewTcApp tc tys) = tc `seq` seqTypes tys
864 seqType (ForAllTy tv ty) = tv `seq` seqType ty
866 seqTypes :: [Type] -> ()
868 seqTypes (ty:tys) = seqType ty `seq` seqTypes tys
870 seqNote :: TyNote -> ()
871 seqNote (SynNote ty) = seqType ty
872 seqNote (FTVNote set) = sizeUniqSet set `seq` ()
874 seqPred :: PredType -> ()
875 seqPred (ClassP c tys) = c `seq` seqTypes tys
876 seqPred (IParam n ty) = n `seq` seqType ty
880 %************************************************************************
882 \subsection{Equality on types}
884 %************************************************************************
886 Comparison; don't use instances so that we know where it happens.
887 Look through newtypes but not usage types.
889 Note that eqType can respond 'False' for partial applications of newtypes.
891 newtype Parser m a = MkParser (Foogle m a)
894 Monad (Parser m) `eqType` Monad (Foogle m)
896 Well, yes, but eqType won't see that they are the same.
897 I don't think this is harmful, but it's soemthing to watch out for.
900 eqType t1 t2 = eq_ty emptyVarEnv t1 t2
901 eqKind = eqType -- No worries about looking
903 -- Look through Notes
904 eq_ty env (NoteTy _ t1) t2 = eq_ty env t1 t2
905 eq_ty env t1 (NoteTy _ t2) = eq_ty env t1 t2
907 -- Look through PredTy and NewTcApp. This is where the looping danger comes from.
908 -- We don't bother to check for the PredType/PredType case, no good reason
909 -- Hmm: maybe there is a good reason: see the notes below about newtypes
910 eq_ty env (PredTy sty1) t2 = eq_ty env (predTypeRep sty1) t2
911 eq_ty env t1 (PredTy sty2) = eq_ty env t1 (predTypeRep sty2)
913 -- NB: we *cannot* short-cut the newtype comparison thus:
914 -- eq_ty env (NewTcApp tc1 tys1) (NewTcApp tc2 tys2)
915 -- | (tc1 == tc2) = (eq_tys env tys1 tys2)
918 -- newtype T a = MkT [a]
919 -- newtype Foo m = MkFoo (forall a. m a -> Int)
924 -- w2 = MkFoo (\(MkT x) -> case w1 of MkFoo f -> f x)
926 -- We end up with w2 = w1; so we need that Foo T = Foo []
927 -- but we can only expand saturated newtypes, so just comparing
928 -- T with [] won't do.
930 eq_ty env (NewTcApp tc1 tys1) t2 = eq_ty env (newTypeRep tc1 tys1) t2
931 eq_ty env t1 (NewTcApp tc2 tys2) = eq_ty env t1 (newTypeRep tc2 tys2)
933 -- The rest is plain sailing
934 eq_ty env (TyVarTy tv1) (TyVarTy tv2) = case lookupVarEnv env tv1 of
935 Just tv1a -> tv1a == tv2
936 Nothing -> tv1 == tv2
937 eq_ty env (ForAllTy tv1 t1) (ForAllTy tv2 t2)
938 | tv1 == tv2 = eq_ty (delVarEnv env tv1) t1 t2
939 | otherwise = eq_ty (extendVarEnv env tv1 tv2) t1 t2
940 eq_ty env (AppTy s1 t1) (AppTy s2 t2) = (eq_ty env s1 s2) && (eq_ty env t1 t2)
941 eq_ty env (FunTy s1 t1) (FunTy s2 t2) = (eq_ty env s1 s2) && (eq_ty env t1 t2)
942 eq_ty env (TyConApp tc1 tys1) (TyConApp tc2 tys2) = (tc1 == tc2) && (eq_tys env tys1 tys2)
943 eq_ty env t1 t2 = False
945 eq_tys env [] [] = True
946 eq_tys env (t1:tys1) (t2:tys2) = (eq_ty env t1 t2) && (eq_tys env tys1 tys2)
947 eq_tys env tys1 tys2 = False