2 % (c) The GRASP/AQUA Project, Glasgow University, 1998
4 \section[Type]{Type - public interface}
8 -- re-exports from TypeRep
9 TyThing(..), Type, PredType(..), ThetaType, TyVarSubst,
12 -- Re-exports from Kind
16 mkTyVarTy, mkTyVarTys, getTyVar, getTyVar_maybe, isTyVarTy,
18 mkAppTy, mkAppTys, splitAppTy, splitAppTys, splitAppTy_maybe,
20 mkFunTy, mkFunTys, splitFunTy, splitFunTy_maybe, splitFunTys,
21 funResultTy, funArgTy, zipFunTys, isFunTy,
23 mkGenTyConApp, mkTyConApp, mkTyConTy,
24 tyConAppTyCon, tyConAppArgs,
25 splitTyConApp_maybe, splitTyConApp,
31 mkForAllTy, mkForAllTys, splitForAllTy_maybe, splitForAllTys,
32 applyTy, applyTys, isForAllTy, dropForAlls,
35 predTypeRep, mkPredTy, mkPredTys,
38 splitRecNewType_maybe,
41 isUnLiftedType, isUnboxedTupleType, isAlgType, isPrimitiveType,
42 isStrictType, isStrictPred,
45 tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tyVarsOfTheta,
46 typeKind, addFreeTyVars,
48 -- Tidying up for printing
50 tidyOpenType, tidyOpenTypes,
51 tidyTyVarBndr, tidyFreeTyVars,
52 tidyOpenTyVar, tidyOpenTyVars,
53 tidyTopType, tidyPred,
62 pprType, pprParendType,
63 pprPred, pprTheta, pprThetaArrow, pprClassPred
66 #include "HsVersions.h"
68 -- We import the representation and primitive functions from TypeRep.
69 -- Many things are reexported, but not the representation!
75 import {-# SOURCE #-} Subst ( substTyWith )
79 import Var ( TyVar, tyVarKind, tyVarName, setTyVarName )
83 import Name ( NamedThing(..), mkInternalName, tidyOccName )
84 import Class ( Class, classTyCon )
85 import TyCon ( TyCon, isRecursiveTyCon, isPrimTyCon,
86 isUnboxedTupleTyCon, isUnLiftedTyCon,
87 isFunTyCon, isNewTyCon, newTyConRep,
88 isAlgTyCon, isSynTyCon, tyConArity,
89 tyConKind, getSynTyConDefn,
94 import CmdLineOpts ( opt_DictsStrict )
95 import SrcLoc ( noSrcLoc )
96 import PrimRep ( PrimRep(..) )
97 import Unique ( Uniquable(..) )
98 import Util ( mapAccumL, seqList, lengthIs, snocView )
100 import UniqSet ( sizeUniqSet ) -- Should come via VarSet
101 import Maybe ( isJust )
105 %************************************************************************
107 \subsection{Constructor-specific functions}
109 %************************************************************************
112 ---------------------------------------------------------------------
116 mkTyVarTy :: TyVar -> Type
119 mkTyVarTys :: [TyVar] -> [Type]
120 mkTyVarTys = map mkTyVarTy -- a common use of mkTyVarTy
122 getTyVar :: String -> Type -> TyVar
123 getTyVar msg ty = case getTyVar_maybe ty of
125 Nothing -> panic ("getTyVar: " ++ msg)
127 isTyVarTy :: Type -> Bool
128 isTyVarTy ty = isJust (getTyVar_maybe ty)
130 getTyVar_maybe :: Type -> Maybe TyVar
131 getTyVar_maybe (TyVarTy tv) = Just tv
132 getTyVar_maybe (NoteTy _ t) = getTyVar_maybe t
133 getTyVar_maybe (PredTy p) = getTyVar_maybe (predTypeRep p)
134 getTyVar_maybe (NewTcApp tc tys) = getTyVar_maybe (newTypeRep tc tys)
135 getTyVar_maybe other = Nothing
139 ---------------------------------------------------------------------
142 We need to be pretty careful with AppTy to make sure we obey the
143 invariant that a TyConApp is always visibly so. mkAppTy maintains the
147 mkAppTy orig_ty1 orig_ty2
150 mk_app (NoteTy _ ty1) = mk_app ty1
151 mk_app (NewTcApp tc tys) = NewTcApp tc (tys ++ [orig_ty2])
152 mk_app (TyConApp tc tys) = mkGenTyConApp tc (tys ++ [orig_ty2])
153 mk_app ty1 = AppTy orig_ty1 orig_ty2
154 -- We call mkGenTyConApp because the TyConApp could be an
155 -- under-saturated type synonym. GHC allows that; e.g.
156 -- type Foo k = k a -> k a
158 -- foo :: Foo Id -> Foo Id
160 -- Here Id is partially applied in the type sig for Foo,
161 -- but once the type synonyms are expanded all is well
163 mkAppTys :: Type -> [Type] -> Type
164 mkAppTys orig_ty1 [] = orig_ty1
165 -- This check for an empty list of type arguments
166 -- avoids the needless loss of a type synonym constructor.
167 -- For example: mkAppTys Rational []
168 -- returns to (Ratio Integer), which has needlessly lost
169 -- the Rational part.
170 mkAppTys orig_ty1 orig_tys2
173 mk_app (NoteTy _ ty1) = mk_app ty1
174 mk_app (NewTcApp tc tys) = NewTcApp tc (tys ++ orig_tys2)
175 mk_app (TyConApp tc tys) = mkTyConApp tc (tys ++ orig_tys2)
176 -- Use mkTyConApp in case tc is (->)
177 mk_app ty1 = foldl AppTy orig_ty1 orig_tys2
179 splitAppTy_maybe :: Type -> Maybe (Type, Type)
180 splitAppTy_maybe (FunTy ty1 ty2) = Just (TyConApp funTyCon [ty1], ty2)
181 splitAppTy_maybe (AppTy ty1 ty2) = Just (ty1, ty2)
182 splitAppTy_maybe (NoteTy _ ty) = splitAppTy_maybe ty
183 splitAppTy_maybe (PredTy p) = splitAppTy_maybe (predTypeRep p)
184 splitAppTy_maybe (NewTcApp tc tys) = splitAppTy_maybe (newTypeRep tc tys)
185 splitAppTy_maybe (TyConApp tc tys) = case snocView tys of
187 Just (tys',ty') -> Just (mkGenTyConApp tc tys', ty')
188 -- mkGenTyConApp just in case the tc is a newtype
190 splitAppTy_maybe other = Nothing
192 splitAppTy :: Type -> (Type, Type)
193 splitAppTy ty = case splitAppTy_maybe ty of
195 Nothing -> panic "splitAppTy"
197 splitAppTys :: Type -> (Type, [Type])
198 splitAppTys ty = split ty ty []
200 split orig_ty (AppTy ty arg) args = split ty ty (arg:args)
201 split orig_ty (NoteTy _ ty) args = split orig_ty ty args
202 split orig_ty (PredTy p) args = split orig_ty (predTypeRep p) args
203 split orig_ty (NewTcApp tc tc_args) args = split orig_ty (newTypeRep tc tc_args) args
204 split orig_ty (TyConApp tc tc_args) args = (mkGenTyConApp tc [], tc_args ++ args)
205 -- mkGenTyConApp just in case the tc is a newtype
206 split orig_ty (FunTy ty1 ty2) args = ASSERT( null args )
207 (TyConApp funTyCon [], [ty1,ty2])
208 split orig_ty ty args = (orig_ty, args)
212 ---------------------------------------------------------------------
217 mkFunTy :: Type -> Type -> Type
218 mkFunTy arg res = FunTy arg res
220 mkFunTys :: [Type] -> Type -> Type
221 mkFunTys tys ty = foldr FunTy ty tys
223 isFunTy :: Type -> Bool
224 isFunTy ty = isJust (splitFunTy_maybe ty)
226 splitFunTy :: Type -> (Type, Type)
227 splitFunTy (FunTy arg res) = (arg, res)
228 splitFunTy (NoteTy _ ty) = splitFunTy ty
229 splitFunTy (PredTy p) = splitFunTy (predTypeRep p)
230 splitFunTy (NewTcApp tc tys) = splitFunTy (newTypeRep tc tys)
231 splitFunTy other = pprPanic "splitFunTy" (ppr other)
233 splitFunTy_maybe :: Type -> Maybe (Type, Type)
234 splitFunTy_maybe (FunTy arg res) = Just (arg, res)
235 splitFunTy_maybe (NoteTy _ ty) = splitFunTy_maybe ty
236 splitFunTy_maybe (PredTy p) = splitFunTy_maybe (predTypeRep p)
237 splitFunTy_maybe (NewTcApp tc tys) = splitFunTy_maybe (newTypeRep tc tys)
238 splitFunTy_maybe other = Nothing
240 splitFunTys :: Type -> ([Type], Type)
241 splitFunTys ty = split [] ty ty
243 split args orig_ty (FunTy arg res) = split (arg:args) res res
244 split args orig_ty (NoteTy _ ty) = split args orig_ty ty
245 split args orig_ty (PredTy p) = split args orig_ty (predTypeRep p)
246 split args orig_ty (NewTcApp tc tys) = split args orig_ty (newTypeRep tc tys)
247 split args orig_ty ty = (reverse args, orig_ty)
249 zipFunTys :: Outputable a => [a] -> Type -> ([(a,Type)], Type)
250 zipFunTys orig_xs orig_ty = split [] orig_xs orig_ty orig_ty
252 split acc [] nty ty = (reverse acc, nty)
253 split acc (x:xs) nty (FunTy arg res) = split ((x,arg):acc) xs res res
254 split acc xs nty (NoteTy _ ty) = split acc xs nty ty
255 split acc xs nty (PredTy p) = split acc xs nty (predTypeRep p)
256 split acc xs nty (NewTcApp tc tys) = split acc xs nty (newTypeRep tc tys)
257 split acc (x:xs) nty ty = pprPanic "zipFunTys" (ppr orig_xs <+> ppr orig_ty)
259 funResultTy :: Type -> Type
260 funResultTy (FunTy arg res) = res
261 funResultTy (NoteTy _ ty) = funResultTy ty
262 funResultTy (PredTy p) = funResultTy (predTypeRep p)
263 funResultTy (NewTcApp tc tys) = funResultTy (newTypeRep tc tys)
264 funResultTy ty = pprPanic "funResultTy" (ppr ty)
266 funArgTy :: Type -> Type
267 funArgTy (FunTy arg res) = arg
268 funArgTy (NoteTy _ ty) = funArgTy ty
269 funArgTy (PredTy p) = funArgTy (predTypeRep p)
270 funArgTy (NewTcApp tc tys) = funArgTy (newTypeRep tc tys)
271 funArgTy ty = pprPanic "funArgTy" (ppr ty)
275 ---------------------------------------------------------------------
278 @mkTyConApp@ is a key function, because it builds a TyConApp, FunTy or PredTy,
282 mkGenTyConApp :: TyCon -> [Type] -> Type
284 | isSynTyCon tc = mkSynTy tc tys
285 | otherwise = mkTyConApp tc tys
287 mkTyConApp :: TyCon -> [Type] -> Type
288 -- Assumes TyCon is not a SynTyCon; use mkSynTy instead for those
290 | isFunTyCon tycon, [ty1,ty2] <- tys
297 = ASSERT(not (isSynTyCon tycon))
300 mkTyConTy :: TyCon -> Type
301 mkTyConTy tycon = mkTyConApp tycon []
303 -- splitTyConApp "looks through" synonyms, because they don't
304 -- mean a distinct type, but all other type-constructor applications
305 -- including functions are returned as Just ..
307 tyConAppTyCon :: Type -> TyCon
308 tyConAppTyCon ty = fst (splitTyConApp ty)
310 tyConAppArgs :: Type -> [Type]
311 tyConAppArgs ty = snd (splitTyConApp ty)
313 splitTyConApp :: Type -> (TyCon, [Type])
314 splitTyConApp ty = case splitTyConApp_maybe ty of
316 Nothing -> pprPanic "splitTyConApp" (ppr ty)
318 splitTyConApp_maybe :: Type -> Maybe (TyCon, [Type])
319 splitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
320 splitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res])
321 splitTyConApp_maybe (NoteTy _ ty) = splitTyConApp_maybe ty
322 splitTyConApp_maybe (PredTy p) = splitTyConApp_maybe (predTypeRep p)
323 splitTyConApp_maybe (NewTcApp tc tys) = splitTyConApp_maybe (newTypeRep tc tys)
324 splitTyConApp_maybe other = Nothing
328 ---------------------------------------------------------------------
334 | n_args == arity -- Exactly saturated
336 | n_args > arity -- Over-saturated
337 = case splitAt arity tys of { (as,bs) -> mkAppTys (mk_syn as) bs }
338 -- Its important to use mkAppTys, rather than (foldl AppTy),
339 -- because (mk_syn as) might well return a partially-applied
340 -- type constructor; indeed, usually will!
341 | otherwise -- Un-saturated
343 -- For the un-saturated case we build TyConApp directly
344 -- (mkTyConApp ASSERTs that the tc isn't a SynTyCon).
345 -- Here we are relying on checkValidType to find
346 -- the error. What we can't do is use mkSynTy with
347 -- too few arg tys, because that is utterly bogus.
350 mk_syn tys = NoteTy (SynNote (TyConApp tycon tys))
351 (substTyWith tyvars tys body)
353 (tyvars, body) = ASSERT( isSynTyCon tycon ) getSynTyConDefn tycon
354 arity = tyConArity tycon
358 Notes on type synonyms
359 ~~~~~~~~~~~~~~~~~~~~~~
360 The various "split" functions (splitFunTy, splitRhoTy, splitForAllTy) try
361 to return type synonyms whereever possible. Thus
366 splitFunTys (a -> Foo a) = ([a], Foo a)
369 The reason is that we then get better (shorter) type signatures in
370 interfaces. Notably this plays a role in tcTySigs in TcBinds.lhs.
375 repType looks through
379 (d) usage annotations
380 (e) [recursive] newtypes
381 It's useful in the back end.
384 repType :: Type -> Type
385 -- Only applied to types of kind *; hence tycons are saturated
386 repType (ForAllTy _ ty) = repType ty
387 repType (NoteTy _ ty) = repType ty
388 repType (PredTy p) = repType (predTypeRep p)
389 repType (NewTcApp tc tys) = ASSERT( tys `lengthIs` tyConArity tc )
390 repType (new_type_rep tc tys)
394 typePrimRep :: Type -> PrimRep
395 typePrimRep ty = case repType ty of
396 TyConApp tc _ -> tyConPrimRep tc
398 AppTy _ _ -> PtrRep -- ??
400 other -> pprPanic "typePrimRep" (ppr ty)
405 ---------------------------------------------------------------------
410 mkForAllTy :: TyVar -> Type -> Type
412 = mkForAllTys [tyvar] ty
414 mkForAllTys :: [TyVar] -> Type -> Type
415 mkForAllTys tyvars ty = foldr ForAllTy ty tyvars
417 isForAllTy :: Type -> Bool
418 isForAllTy (NoteTy _ ty) = isForAllTy ty
419 isForAllTy (ForAllTy _ _) = True
420 isForAllTy other_ty = False
422 splitForAllTy_maybe :: Type -> Maybe (TyVar, Type)
423 splitForAllTy_maybe ty = splitFAT_m ty
425 splitFAT_m (NoteTy _ ty) = splitFAT_m ty
426 splitFAT_m (PredTy p) = splitFAT_m (predTypeRep p)
427 splitFAT_m (NewTcApp tc tys) = splitFAT_m (newTypeRep tc tys)
428 splitFAT_m (ForAllTy tyvar ty) = Just(tyvar, ty)
429 splitFAT_m _ = Nothing
431 splitForAllTys :: Type -> ([TyVar], Type)
432 splitForAllTys ty = split ty ty []
434 split orig_ty (ForAllTy tv ty) tvs = split ty ty (tv:tvs)
435 split orig_ty (NoteTy _ ty) tvs = split orig_ty ty tvs
436 split orig_ty (PredTy p) tvs = split orig_ty (predTypeRep p) tvs
437 split orig_ty (NewTcApp tc tys) tvs = split orig_ty (newTypeRep tc tys) tvs
438 split orig_ty t tvs = (reverse tvs, orig_ty)
440 dropForAlls :: Type -> Type
441 dropForAlls ty = snd (splitForAllTys ty)
444 -- (mkPiType now in CoreUtils)
448 Instantiate a for-all type with one or more type arguments.
449 Used when we have a polymorphic function applied to type args:
451 Then we use (applyTys type-of-f [t1,t2]) to compute the type of
455 applyTy :: Type -> Type -> Type
456 applyTy (PredTy p) arg = applyTy (predTypeRep p) arg
457 applyTy (NewTcApp tc tys) arg = applyTy (newTypeRep tc tys) arg
458 applyTy (NoteTy _ fun) arg = applyTy fun arg
459 applyTy (ForAllTy tv ty) arg = substTyWith [tv] [arg] ty
460 applyTy other arg = panic "applyTy"
462 applyTys :: Type -> [Type] -> Type
463 -- This function is interesting because
464 -- a) the function may have more for-alls than there are args
465 -- b) less obviously, it may have fewer for-alls
466 -- For case (b) think of
467 -- applyTys (forall a.a) [forall b.b, Int]
468 -- This really can happen, via dressing up polymorphic types with newtype
469 -- clothing. Here's an example:
470 -- newtype R = R (forall a. a->a)
471 -- foo = case undefined :: R of
474 applyTys orig_fun_ty [] = orig_fun_ty
475 applyTys orig_fun_ty arg_tys
476 | n_tvs == n_args -- The vastly common case
477 = substTyWith tvs arg_tys rho_ty
478 | n_tvs > n_args -- Too many for-alls
479 = substTyWith (take n_args tvs) arg_tys
480 (mkForAllTys (drop n_args tvs) rho_ty)
481 | otherwise -- Too many type args
482 = ASSERT2( n_tvs > 0, ppr orig_fun_ty ) -- Zero case gives infnite loop!
483 applyTys (substTyWith tvs (take n_tvs arg_tys) rho_ty)
486 (tvs, rho_ty) = splitForAllTys orig_fun_ty
488 n_args = length arg_tys
492 %************************************************************************
494 \subsection{Source types}
496 %************************************************************************
498 A "source type" is a type that is a separate type as far as the type checker is
499 concerned, but which has low-level representation as far as the back end is concerned.
501 Source types are always lifted.
503 The key function is predTypeRep which gives the representation of a source type:
506 mkPredTy :: PredType -> Type
507 mkPredTy pred = PredTy pred
509 mkPredTys :: ThetaType -> [Type]
510 mkPredTys preds = map PredTy preds
512 predTypeRep :: PredType -> Type
513 -- Convert a PredType to its "representation type";
514 -- the post-type-checking type used by all the Core passes of GHC.
515 predTypeRep (IParam _ ty) = ty
516 predTypeRep (ClassP clas tys) = mkTyConApp (classTyCon clas) tys
517 -- Result might be a NewTcApp, but the consumer will
518 -- look through that too if necessary
522 %************************************************************************
526 %************************************************************************
529 splitRecNewType_maybe :: Type -> Maybe Type
530 -- Newtypes are always represented by a NewTcApp
531 -- Sometimes we want to look through a recursive newtype, and that's what happens here
532 -- Only applied to types of kind *, hence the newtype is always saturated
533 splitRecNewType_maybe (NoteTy _ ty) = splitRecNewType_maybe ty
534 splitRecNewType_maybe (NewTcApp tc tys)
535 | isRecursiveTyCon tc
536 = ASSERT( tys `lengthIs` tyConArity tc && isNewTyCon tc )
537 -- The assert should hold because repType should
538 -- only be applied to *types* (of kind *)
539 Just (new_type_rep tc tys)
540 splitRecNewType_maybe other = Nothing
542 -----------------------------
543 newTypeRep :: TyCon -> [Type] -> Type
544 -- A local helper function (not exported)
545 -- Expands a newtype application to
546 -- *either* a vanilla TyConApp (recursive newtype, or non-saturated)
547 -- *or* the newtype representation (otherwise)
548 -- Either way, the result is not a NewTcApp
550 -- NB: the returned TyConApp is always deconstructed immediately by the
551 -- caller... a TyConApp with a newtype type constructor never lives
552 -- in an ordinary type
554 | not (isRecursiveTyCon tc), -- Not recursive and saturated
555 tys `lengthIs` tyConArity tc -- treat as equivalent to expansion
556 = new_type_rep tc tys
559 -- ToDo: Consider caching this substitution in a NType
561 ----------------------------
562 -- new_type_rep doesn't ask any questions:
563 -- it just expands newtype, whether recursive or not
564 new_type_rep new_tycon tys = ASSERT( tys `lengthIs` tyConArity new_tycon )
565 case newTyConRep new_tycon of
566 (tvs, rep_ty) -> substTyWith tvs tys rep_ty
570 %************************************************************************
572 \subsection{Kinds and free variables}
574 %************************************************************************
576 ---------------------------------------------------------------------
577 Finding the kind of a type
578 ~~~~~~~~~~~~~~~~~~~~~~~~~~
580 typeKind :: Type -> Kind
582 typeKind (TyVarTy tyvar) = tyVarKind tyvar
583 typeKind (TyConApp tycon tys) = foldr (\_ k -> kindFunResult k) (tyConKind tycon) tys
584 typeKind (NewTcApp tycon tys) = foldr (\_ k -> kindFunResult k) (tyConKind tycon) tys
585 typeKind (NoteTy _ ty) = typeKind ty
586 typeKind (PredTy _) = liftedTypeKind -- Predicates are always
587 -- represented by lifted types
588 typeKind (AppTy fun arg) = kindFunResult (typeKind fun)
589 typeKind (FunTy arg res) = liftedTypeKind
590 typeKind (ForAllTy tv ty) = typeKind ty
594 ---------------------------------------------------------------------
595 Free variables of a type
596 ~~~~~~~~~~~~~~~~~~~~~~~~
598 tyVarsOfType :: Type -> TyVarSet
599 tyVarsOfType (TyVarTy tv) = unitVarSet tv
600 tyVarsOfType (TyConApp tycon tys) = tyVarsOfTypes tys
601 tyVarsOfType (NewTcApp tycon tys) = tyVarsOfTypes tys
602 tyVarsOfType (NoteTy (FTVNote tvs) ty2) = tvs
603 tyVarsOfType (NoteTy (SynNote ty1) ty2) = tyVarsOfType ty2 -- See note [Syn] below
604 tyVarsOfType (PredTy sty) = tyVarsOfPred sty
605 tyVarsOfType (FunTy arg res) = tyVarsOfType arg `unionVarSet` tyVarsOfType res
606 tyVarsOfType (AppTy fun arg) = tyVarsOfType fun `unionVarSet` tyVarsOfType arg
607 tyVarsOfType (ForAllTy tyvar ty) = tyVarsOfType ty `minusVarSet` unitVarSet tyvar
612 -- What are the free tyvars of (T x)? Empty, of course!
613 -- Here's the example that Ralf Laemmel showed me:
614 -- foo :: (forall a. C u a -> C u a) -> u
615 -- mappend :: Monoid u => u -> u -> u
617 -- bar :: Monoid u => u
618 -- bar = foo (\t -> t `mappend` t)
619 -- We have to generalise at the arg to f, and we don't
620 -- want to capture the constraint (Monad (C u a)) because
621 -- it appears to mention a. Pretty silly, but it was useful to him.
624 tyVarsOfTypes :: [Type] -> TyVarSet
625 tyVarsOfTypes tys = foldr (unionVarSet.tyVarsOfType) emptyVarSet tys
627 tyVarsOfPred :: PredType -> TyVarSet
628 tyVarsOfPred (IParam _ ty) = tyVarsOfType ty
629 tyVarsOfPred (ClassP _ tys) = tyVarsOfTypes tys
631 tyVarsOfTheta :: ThetaType -> TyVarSet
632 tyVarsOfTheta = foldr (unionVarSet . tyVarsOfPred) emptyVarSet
634 -- Add a Note with the free tyvars to the top of the type
635 addFreeTyVars :: Type -> Type
636 addFreeTyVars ty@(NoteTy (FTVNote _) _) = ty
637 addFreeTyVars ty = NoteTy (FTVNote (tyVarsOfType ty)) ty
640 %************************************************************************
642 \subsection{TidyType}
644 %************************************************************************
646 tidyTy tidies up a type for printing in an error message, or in
649 It doesn't change the uniques at all, just the print names.
652 tidyTyVarBndr :: TidyEnv -> TyVar -> (TidyEnv, TyVar)
653 tidyTyVarBndr (tidy_env, subst) tyvar
654 = case tidyOccName tidy_env (getOccName name) of
655 (tidy', occ') -> ((tidy', subst'), tyvar')
657 subst' = extendVarEnv subst tyvar tyvar'
658 tyvar' = setTyVarName tyvar name'
659 name' = mkInternalName (getUnique name) occ' noSrcLoc
660 -- Note: make a *user* tyvar, so it printes nicely
661 -- Could extract src loc, but no need.
663 name = tyVarName tyvar
665 tidyFreeTyVars :: TidyEnv -> TyVarSet -> TidyEnv
666 -- Add the free tyvars to the env in tidy form,
667 -- so that we can tidy the type they are free in
668 tidyFreeTyVars env tyvars = fst (tidyOpenTyVars env (varSetElems tyvars))
670 tidyOpenTyVars :: TidyEnv -> [TyVar] -> (TidyEnv, [TyVar])
671 tidyOpenTyVars env tyvars = mapAccumL tidyOpenTyVar env tyvars
673 tidyOpenTyVar :: TidyEnv -> TyVar -> (TidyEnv, TyVar)
674 -- Treat a new tyvar as a binder, and give it a fresh tidy name
675 tidyOpenTyVar env@(tidy_env, subst) tyvar
676 = case lookupVarEnv subst tyvar of
677 Just tyvar' -> (env, tyvar') -- Already substituted
678 Nothing -> tidyTyVarBndr env tyvar -- Treat it as a binder
680 tidyType :: TidyEnv -> Type -> Type
681 tidyType env@(tidy_env, subst) ty
684 go (TyVarTy tv) = case lookupVarEnv subst tv of
685 Nothing -> TyVarTy tv
686 Just tv' -> TyVarTy tv'
687 go (TyConApp tycon tys) = let args = map go tys
688 in args `seqList` TyConApp tycon args
689 go (NewTcApp tycon tys) = let args = map go tys
690 in args `seqList` NewTcApp tycon args
691 go (NoteTy note ty) = (NoteTy $! (go_note note)) $! (go ty)
692 go (PredTy sty) = PredTy (tidyPred env sty)
693 go (AppTy fun arg) = (AppTy $! (go fun)) $! (go arg)
694 go (FunTy fun arg) = (FunTy $! (go fun)) $! (go arg)
695 go (ForAllTy tv ty) = ForAllTy tvp $! (tidyType envp ty)
697 (envp, tvp) = tidyTyVarBndr env tv
699 go_note (SynNote ty) = SynNote $! (go ty)
700 go_note note@(FTVNote ftvs) = note -- No need to tidy the free tyvars
702 tidyTypes env tys = map (tidyType env) tys
704 tidyPred :: TidyEnv -> PredType -> PredType
705 tidyPred env (IParam n ty) = IParam n (tidyType env ty)
706 tidyPred env (ClassP clas tys) = ClassP clas (tidyTypes env tys)
710 @tidyOpenType@ grabs the free type variables, tidies them
711 and then uses @tidyType@ to work over the type itself
714 tidyOpenType :: TidyEnv -> Type -> (TidyEnv, Type)
716 = (env', tidyType env' ty)
718 env' = tidyFreeTyVars env (tyVarsOfType ty)
720 tidyOpenTypes :: TidyEnv -> [Type] -> (TidyEnv, [Type])
721 tidyOpenTypes env tys = mapAccumL tidyOpenType env tys
723 tidyTopType :: Type -> Type
724 tidyTopType ty = tidyType emptyTidyEnv ty
729 %************************************************************************
731 \subsection{Liftedness}
733 %************************************************************************
736 isUnLiftedType :: Type -> Bool
737 -- isUnLiftedType returns True for forall'd unlifted types:
738 -- x :: forall a. Int#
739 -- I found bindings like these were getting floated to the top level.
740 -- They are pretty bogus types, mind you. It would be better never to
743 isUnLiftedType (ForAllTy tv ty) = isUnLiftedType ty
744 isUnLiftedType (NoteTy _ ty) = isUnLiftedType ty
745 isUnLiftedType (TyConApp tc _) = isUnLiftedTyCon tc
746 isUnLiftedType (PredTy _) = False -- All source types are lifted
747 isUnLiftedType (NewTcApp tc tys) = isUnLiftedType (newTypeRep tc tys)
748 isUnLiftedType other = False
750 isUnboxedTupleType :: Type -> Bool
751 isUnboxedTupleType ty = case splitTyConApp_maybe ty of
752 Just (tc, ty_args) -> isUnboxedTupleTyCon tc
755 -- Should only be applied to *types*; hence the assert
756 isAlgType :: Type -> Bool
757 isAlgType ty = case splitTyConApp_maybe ty of
758 Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc )
763 @isStrictType@ computes whether an argument (or let RHS) should
764 be computed strictly or lazily, based only on its type.
765 Works just like isUnLiftedType, except that it has a special case
766 for dictionaries. Since it takes account of ClassP, you might think
767 this function should be in TcType, but isStrictType is used by DataCon,
768 which is below TcType in the hierarchy, so it's convenient to put it here.
771 isStrictType (ForAllTy tv ty) = isStrictType ty
772 isStrictType (NoteTy _ ty) = isStrictType ty
773 isStrictType (TyConApp tc _) = isUnLiftedTyCon tc
774 isStrictType (NewTcApp tc tys) = isStrictType (newTypeRep tc tys)
775 isStrictType (PredTy pred) = isStrictPred pred
776 isStrictType other = False
778 isStrictPred (ClassP clas _) = opt_DictsStrict && not (isNewTyCon (classTyCon clas))
779 isStrictPred other = False
780 -- We may be strict in dictionary types, but only if it
781 -- has more than one component.
782 -- [Being strict in a single-component dictionary risks
783 -- poking the dictionary component, which is wrong.]
787 isPrimitiveType :: Type -> Bool
788 -- Returns types that are opaque to Haskell.
789 -- Most of these are unlifted, but now that we interact with .NET, we
790 -- may have primtive (foreign-imported) types that are lifted
791 isPrimitiveType ty = case splitTyConApp_maybe ty of
792 Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc )
798 %************************************************************************
800 \subsection{Sequencing on types
802 %************************************************************************
805 seqType :: Type -> ()
806 seqType (TyVarTy tv) = tv `seq` ()
807 seqType (AppTy t1 t2) = seqType t1 `seq` seqType t2
808 seqType (FunTy t1 t2) = seqType t1 `seq` seqType t2
809 seqType (NoteTy note t2) = seqNote note `seq` seqType t2
810 seqType (PredTy p) = seqPred p
811 seqType (TyConApp tc tys) = tc `seq` seqTypes tys
812 seqType (NewTcApp tc tys) = tc `seq` seqTypes tys
813 seqType (ForAllTy tv ty) = tv `seq` seqType ty
815 seqTypes :: [Type] -> ()
817 seqTypes (ty:tys) = seqType ty `seq` seqTypes tys
819 seqNote :: TyNote -> ()
820 seqNote (SynNote ty) = seqType ty
821 seqNote (FTVNote set) = sizeUniqSet set `seq` ()
823 seqPred :: PredType -> ()
824 seqPred (ClassP c tys) = c `seq` seqTypes tys
825 seqPred (IParam n ty) = n `seq` seqType ty
829 %************************************************************************
831 \subsection{Equality on types}
833 %************************************************************************
835 Comparison; don't use instances so that we know where it happens.
836 Look through newtypes but not usage types.
838 Note that eqType can respond 'False' for partial applications of newtypes.
840 newtype Parser m a = MkParser (Foogle m a)
843 Monad (Parser m) `eqType` Monad (Foogle m)
845 Well, yes, but eqType won't see that they are the same.
846 I don't think this is harmful, but it's soemthing to watch out for.
849 eqType t1 t2 = eq_ty emptyVarEnv t1 t2
851 -- Look through Notes
852 eq_ty env (NoteTy _ t1) t2 = eq_ty env t1 t2
853 eq_ty env t1 (NoteTy _ t2) = eq_ty env t1 t2
855 -- Look through PredTy and NewTcApp. This is where the looping danger comes from.
856 -- We don't bother to check for the PredType/PredType case, no good reason
857 -- Hmm: maybe there is a good reason: see the notes below about newtypes
858 eq_ty env (PredTy sty1) t2 = eq_ty env (predTypeRep sty1) t2
859 eq_ty env t1 (PredTy sty2) = eq_ty env t1 (predTypeRep sty2)
861 -- NB: we *cannot* short-cut the newtype comparison thus:
862 -- eq_ty env (NewTcApp tc1 tys1) (NewTcApp tc2 tys2)
863 -- | (tc1 == tc2) = (eq_tys env tys1 tys2)
866 -- newtype T a = MkT [a]
867 -- newtype Foo m = MkFoo (forall a. m a -> Int)
872 -- w2 = MkFoo (\(MkT x) -> case w1 of MkFoo f -> f x)
874 -- We end up with w2 = w1; so we need that Foo T = Foo []
875 -- but we can only expand saturated newtypes, so just comparing
876 -- T with [] won't do.
878 eq_ty env (NewTcApp tc1 tys1) t2 = eq_ty env (newTypeRep tc1 tys1) t2
879 eq_ty env t1 (NewTcApp tc2 tys2) = eq_ty env t1 (newTypeRep tc2 tys2)
881 -- The rest is plain sailing
882 eq_ty env (TyVarTy tv1) (TyVarTy tv2) = case lookupVarEnv env tv1 of
883 Just tv1a -> tv1a == tv2
884 Nothing -> tv1 == tv2
885 eq_ty env (ForAllTy tv1 t1) (ForAllTy tv2 t2)
886 | tv1 == tv2 = eq_ty (delVarEnv env tv1) t1 t2
887 | otherwise = eq_ty (extendVarEnv env tv1 tv2) t1 t2
888 eq_ty env (AppTy s1 t1) (AppTy s2 t2) = (eq_ty env s1 s2) && (eq_ty env t1 t2)
889 eq_ty env (FunTy s1 t1) (FunTy s2 t2) = (eq_ty env s1 s2) && (eq_ty env t1 t2)
890 eq_ty env (TyConApp tc1 tys1) (TyConApp tc2 tys2) = (tc1 == tc2) && (eq_tys env tys1 tys2)
891 eq_ty env t1 t2 = False
893 eq_tys env [] [] = True
894 eq_tys env (t1:tys1) (t2:tys2) = (eq_ty env t1 t2) && (eq_tys env tys1 tys2)
895 eq_tys env tys1 tys2 = False