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
15 -- Re-exports from TyCon
18 mkTyVarTy, mkTyVarTys, getTyVar, getTyVar_maybe, isTyVarTy,
20 mkAppTy, mkAppTys, splitAppTy, splitAppTys, splitAppTy_maybe,
22 mkFunTy, mkFunTys, splitFunTy, splitFunTy_maybe, splitFunTys,
23 funResultTy, funArgTy, zipFunTys, isFunTy,
25 mkGenTyConApp, mkTyConApp, mkTyConTy,
26 tyConAppTyCon, tyConAppArgs,
27 splitTyConApp_maybe, splitTyConApp,
33 mkForAllTy, mkForAllTys, splitForAllTy_maybe, splitForAllTys,
34 applyTy, applyTys, isForAllTy, dropForAlls,
37 predTypeRep, mkPredTy, mkPredTys,
40 splitRecNewType_maybe,
43 isUnLiftedType, isUnboxedTupleType, isAlgType, isPrimitiveType,
44 isStrictType, isStrictPred,
47 tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tyVarsOfTheta,
48 typeKind, addFreeTyVars,
50 -- Tidying up for printing
52 tidyOpenType, tidyOpenTypes,
53 tidyTyVarBndr, tidyFreeTyVars,
54 tidyOpenTyVar, tidyOpenTyVars,
55 tidyTopType, tidyPred,
64 pprType, pprParendType,
65 pprPred, pprTheta, pprThetaArrow, pprClassPred
68 #include "HsVersions.h"
70 -- We import the representation and primitive functions from TypeRep.
71 -- Many things are reexported, but not the representation!
77 import {-# SOURCE #-} Subst ( substTyWith )
81 import Var ( TyVar, tyVarKind, tyVarName, setTyVarName )
85 import Name ( NamedThing(..), mkInternalName, tidyOccName )
86 import Class ( Class, classTyCon )
87 import TyCon ( TyCon, isRecursiveTyCon, isPrimTyCon,
88 isUnboxedTupleTyCon, isUnLiftedTyCon,
89 isFunTyCon, isNewTyCon, newTyConRep, newTyConRhs,
90 isAlgTyCon, isSynTyCon, tyConArity,
91 tyConKind, getSynTyConDefn, PrimRep(..), tyConPrimRep,
95 import CmdLineOpts ( opt_DictsStrict )
96 import SrcLoc ( noSrcLoc )
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 -- ToDo: this could be moved to the code generator, using splitTyConApp instead
395 -- of inspecting the type directly.
396 typePrimRep :: Type -> PrimRep
397 typePrimRep ty = case repType ty of
398 TyConApp tc _ -> tyConPrimRep tc
400 AppTy _ _ -> PtrRep -- See note below
402 other -> pprPanic "typePrimRep" (ppr ty)
403 -- Types of the form 'f a' must be of kind *, not *#, so
404 -- we are guaranteed that they are represented by pointers.
405 -- The reason is that f must have kind *->*, not *->*#, because
406 -- (we claim) there is no way to constrain f's kind any other
409 -- new_type_rep doesn't ask any questions:
410 -- it just expands newtype, whether recursive or not
411 new_type_rep new_tycon tys = ASSERT( tys `lengthIs` tyConArity new_tycon )
412 case newTyConRep new_tycon of
413 (tvs, rep_ty) -> substTyWith tvs tys rep_ty
417 ---------------------------------------------------------------------
422 mkForAllTy :: TyVar -> Type -> Type
424 = mkForAllTys [tyvar] ty
426 mkForAllTys :: [TyVar] -> Type -> Type
427 mkForAllTys tyvars ty = foldr ForAllTy ty tyvars
429 isForAllTy :: Type -> Bool
430 isForAllTy (NoteTy _ ty) = isForAllTy ty
431 isForAllTy (ForAllTy _ _) = True
432 isForAllTy other_ty = False
434 splitForAllTy_maybe :: Type -> Maybe (TyVar, Type)
435 splitForAllTy_maybe ty = splitFAT_m ty
437 splitFAT_m (NoteTy _ ty) = splitFAT_m ty
438 splitFAT_m (PredTy p) = splitFAT_m (predTypeRep p)
439 splitFAT_m (NewTcApp tc tys) = splitFAT_m (newTypeRep tc tys)
440 splitFAT_m (ForAllTy tyvar ty) = Just(tyvar, ty)
441 splitFAT_m _ = Nothing
443 splitForAllTys :: Type -> ([TyVar], Type)
444 splitForAllTys ty = split ty ty []
446 split orig_ty (ForAllTy tv ty) tvs = split ty ty (tv:tvs)
447 split orig_ty (NoteTy _ ty) tvs = split orig_ty ty tvs
448 split orig_ty (PredTy p) tvs = split orig_ty (predTypeRep p) tvs
449 split orig_ty (NewTcApp tc tys) tvs = split orig_ty (newTypeRep tc tys) tvs
450 split orig_ty t tvs = (reverse tvs, orig_ty)
452 dropForAlls :: Type -> Type
453 dropForAlls ty = snd (splitForAllTys ty)
456 -- (mkPiType now in CoreUtils)
460 Instantiate a for-all type with one or more type arguments.
461 Used when we have a polymorphic function applied to type args:
463 Then we use (applyTys type-of-f [t1,t2]) to compute the type of
467 applyTy :: Type -> Type -> Type
468 applyTy (PredTy p) arg = applyTy (predTypeRep p) arg
469 applyTy (NewTcApp tc tys) arg = applyTy (newTypeRep tc tys) arg
470 applyTy (NoteTy _ fun) arg = applyTy fun arg
471 applyTy (ForAllTy tv ty) arg = substTyWith [tv] [arg] ty
472 applyTy other arg = panic "applyTy"
474 applyTys :: Type -> [Type] -> Type
475 -- This function is interesting because
476 -- a) the function may have more for-alls than there are args
477 -- b) less obviously, it may have fewer for-alls
478 -- For case (b) think of
479 -- applyTys (forall a.a) [forall b.b, Int]
480 -- This really can happen, via dressing up polymorphic types with newtype
481 -- clothing. Here's an example:
482 -- newtype R = R (forall a. a->a)
483 -- foo = case undefined :: R of
486 applyTys orig_fun_ty [] = orig_fun_ty
487 applyTys orig_fun_ty arg_tys
488 | n_tvs == n_args -- The vastly common case
489 = substTyWith tvs arg_tys rho_ty
490 | n_tvs > n_args -- Too many for-alls
491 = substTyWith (take n_args tvs) arg_tys
492 (mkForAllTys (drop n_args tvs) rho_ty)
493 | otherwise -- Too many type args
494 = ASSERT2( n_tvs > 0, ppr orig_fun_ty ) -- Zero case gives infnite loop!
495 applyTys (substTyWith tvs (take n_tvs arg_tys) rho_ty)
498 (tvs, rho_ty) = splitForAllTys orig_fun_ty
500 n_args = length arg_tys
504 %************************************************************************
506 \subsection{Source types}
508 %************************************************************************
510 A "source type" is a type that is a separate type as far as the type checker is
511 concerned, but which has low-level representation as far as the back end is concerned.
513 Source types are always lifted.
515 The key function is predTypeRep which gives the representation of a source type:
518 mkPredTy :: PredType -> Type
519 mkPredTy pred = PredTy pred
521 mkPredTys :: ThetaType -> [Type]
522 mkPredTys preds = map PredTy preds
524 predTypeRep :: PredType -> Type
525 -- Convert a PredType to its "representation type";
526 -- the post-type-checking type used by all the Core passes of GHC.
527 -- Unwraps only the outermost level; for example, the result might
528 -- be a NewTcApp; c.f. newTypeRep
529 predTypeRep (IParam _ ty) = ty
530 predTypeRep (ClassP clas tys) = mkTyConApp (classTyCon clas) tys
531 -- Result might be a NewTcApp, but the consumer will
532 -- look through that too if necessary
536 %************************************************************************
540 %************************************************************************
543 splitRecNewType_maybe :: Type -> Maybe Type
544 -- Newtypes are always represented by a NewTcApp
545 -- Sometimes we want to look through a recursive newtype, and that's what happens here
546 -- It only strips *one layer* off, so the caller will usually call itself recursively
547 -- Only applied to types of kind *, hence the newtype is always saturated
548 splitRecNewType_maybe (NoteTy _ ty) = splitRecNewType_maybe ty
549 splitRecNewType_maybe (PredTy p) = splitRecNewType_maybe (predTypeRep p)
550 splitRecNewType_maybe (NewTcApp tc tys)
551 | isRecursiveTyCon tc
552 = ASSERT( tys `lengthIs` tyConArity tc && isNewTyCon tc )
553 -- The assert should hold because splitRecNewType_maybe
554 -- should only be applied to *types* (of kind *)
555 Just (new_type_rhs tc tys)
556 splitRecNewType_maybe other = Nothing
558 -----------------------------
559 newTypeRep :: TyCon -> [Type] -> Type
560 -- A local helper function (not exported)
561 -- Expands *the outermoset level of* a newtype application to
562 -- *either* a vanilla TyConApp (recursive newtype, or non-saturated)
563 -- *or* the newtype representation (otherwise), meaning the
564 -- type written in the RHS of the newtype decl,
565 -- which may itself be a newtype
567 -- Example: newtype R = MkR S
569 -- newtype T = MkT (T -> T)
570 -- newTypeRep on R gives NewTcApp S
571 -- on S gives NewTcApp T
572 -- on T gives TyConApp T
574 -- NB: the returned TyConApp is always deconstructed immediately by the
575 -- caller... a TyConApp with a newtype type constructor never lives
576 -- in an ordinary type
578 | not (isRecursiveTyCon tc), -- Not recursive and saturated
579 tys `lengthIs` tyConArity tc -- treat as equivalent to expansion
580 = new_type_rhs tc tys
583 -- ToDo: Consider caching this substitution in a NType
585 -- new_type_rhs doesn't ask any questions:
586 -- it just expands newtype one level, whether recursive or not
588 = case newTyConRhs tc of
589 (tvs, rep_ty) -> substTyWith tvs tys rep_ty
593 %************************************************************************
595 \subsection{Kinds and free variables}
597 %************************************************************************
599 ---------------------------------------------------------------------
600 Finding the kind of a type
601 ~~~~~~~~~~~~~~~~~~~~~~~~~~
603 typeKind :: Type -> Kind
605 typeKind (TyVarTy tyvar) = tyVarKind tyvar
606 typeKind (TyConApp tycon tys) = foldr (\_ k -> kindFunResult k) (tyConKind tycon) tys
607 typeKind (NewTcApp tycon tys) = foldr (\_ k -> kindFunResult k) (tyConKind tycon) tys
608 typeKind (NoteTy _ ty) = typeKind ty
609 typeKind (PredTy _) = liftedTypeKind -- Predicates are always
610 -- represented by lifted types
611 typeKind (AppTy fun arg) = kindFunResult (typeKind fun)
612 typeKind (FunTy arg res) = liftedTypeKind
613 typeKind (ForAllTy tv ty) = typeKind ty
617 ---------------------------------------------------------------------
618 Free variables of a type
619 ~~~~~~~~~~~~~~~~~~~~~~~~
621 tyVarsOfType :: Type -> TyVarSet
622 tyVarsOfType (TyVarTy tv) = unitVarSet tv
623 tyVarsOfType (TyConApp tycon tys) = tyVarsOfTypes tys
624 tyVarsOfType (NewTcApp tycon tys) = tyVarsOfTypes tys
625 tyVarsOfType (NoteTy (FTVNote tvs) ty2) = tvs
626 tyVarsOfType (NoteTy (SynNote ty1) ty2) = tyVarsOfType ty2 -- See note [Syn] below
627 tyVarsOfType (PredTy sty) = tyVarsOfPred sty
628 tyVarsOfType (FunTy arg res) = tyVarsOfType arg `unionVarSet` tyVarsOfType res
629 tyVarsOfType (AppTy fun arg) = tyVarsOfType fun `unionVarSet` tyVarsOfType arg
630 tyVarsOfType (ForAllTy tyvar ty) = tyVarsOfType ty `minusVarSet` unitVarSet tyvar
635 -- What are the free tyvars of (T x)? Empty, of course!
636 -- Here's the example that Ralf Laemmel showed me:
637 -- foo :: (forall a. C u a -> C u a) -> u
638 -- mappend :: Monoid u => u -> u -> u
640 -- bar :: Monoid u => u
641 -- bar = foo (\t -> t `mappend` t)
642 -- We have to generalise at the arg to f, and we don't
643 -- want to capture the constraint (Monad (C u a)) because
644 -- it appears to mention a. Pretty silly, but it was useful to him.
647 tyVarsOfTypes :: [Type] -> TyVarSet
648 tyVarsOfTypes tys = foldr (unionVarSet.tyVarsOfType) emptyVarSet tys
650 tyVarsOfPred :: PredType -> TyVarSet
651 tyVarsOfPred (IParam _ ty) = tyVarsOfType ty
652 tyVarsOfPred (ClassP _ tys) = tyVarsOfTypes tys
654 tyVarsOfTheta :: ThetaType -> TyVarSet
655 tyVarsOfTheta = foldr (unionVarSet . tyVarsOfPred) emptyVarSet
657 -- Add a Note with the free tyvars to the top of the type
658 addFreeTyVars :: Type -> Type
659 addFreeTyVars ty@(NoteTy (FTVNote _) _) = ty
660 addFreeTyVars ty = NoteTy (FTVNote (tyVarsOfType ty)) ty
663 %************************************************************************
665 \subsection{TidyType}
667 %************************************************************************
669 tidyTy tidies up a type for printing in an error message, or in
672 It doesn't change the uniques at all, just the print names.
675 tidyTyVarBndr :: TidyEnv -> TyVar -> (TidyEnv, TyVar)
676 tidyTyVarBndr (tidy_env, subst) tyvar
677 = case tidyOccName tidy_env (getOccName name) of
678 (tidy', occ') -> ((tidy', subst'), tyvar')
680 subst' = extendVarEnv subst tyvar tyvar'
681 tyvar' = setTyVarName tyvar name'
682 name' = mkInternalName (getUnique name) occ' noSrcLoc
683 -- Note: make a *user* tyvar, so it printes nicely
684 -- Could extract src loc, but no need.
686 name = tyVarName tyvar
688 tidyFreeTyVars :: TidyEnv -> TyVarSet -> TidyEnv
689 -- Add the free tyvars to the env in tidy form,
690 -- so that we can tidy the type they are free in
691 tidyFreeTyVars env tyvars = fst (tidyOpenTyVars env (varSetElems tyvars))
693 tidyOpenTyVars :: TidyEnv -> [TyVar] -> (TidyEnv, [TyVar])
694 tidyOpenTyVars env tyvars = mapAccumL tidyOpenTyVar env tyvars
696 tidyOpenTyVar :: TidyEnv -> TyVar -> (TidyEnv, TyVar)
697 -- Treat a new tyvar as a binder, and give it a fresh tidy name
698 tidyOpenTyVar env@(tidy_env, subst) tyvar
699 = case lookupVarEnv subst tyvar of
700 Just tyvar' -> (env, tyvar') -- Already substituted
701 Nothing -> tidyTyVarBndr env tyvar -- Treat it as a binder
703 tidyType :: TidyEnv -> Type -> Type
704 tidyType env@(tidy_env, subst) ty
707 go (TyVarTy tv) = case lookupVarEnv subst tv of
708 Nothing -> TyVarTy tv
709 Just tv' -> TyVarTy tv'
710 go (TyConApp tycon tys) = let args = map go tys
711 in args `seqList` TyConApp tycon args
712 go (NewTcApp tycon tys) = let args = map go tys
713 in args `seqList` NewTcApp tycon args
714 go (NoteTy note ty) = (NoteTy $! (go_note note)) $! (go ty)
715 go (PredTy sty) = PredTy (tidyPred env sty)
716 go (AppTy fun arg) = (AppTy $! (go fun)) $! (go arg)
717 go (FunTy fun arg) = (FunTy $! (go fun)) $! (go arg)
718 go (ForAllTy tv ty) = ForAllTy tvp $! (tidyType envp ty)
720 (envp, tvp) = tidyTyVarBndr env tv
722 go_note (SynNote ty) = SynNote $! (go ty)
723 go_note note@(FTVNote ftvs) = note -- No need to tidy the free tyvars
725 tidyTypes env tys = map (tidyType env) tys
727 tidyPred :: TidyEnv -> PredType -> PredType
728 tidyPred env (IParam n ty) = IParam n (tidyType env ty)
729 tidyPred env (ClassP clas tys) = ClassP clas (tidyTypes env tys)
733 @tidyOpenType@ grabs the free type variables, tidies them
734 and then uses @tidyType@ to work over the type itself
737 tidyOpenType :: TidyEnv -> Type -> (TidyEnv, Type)
739 = (env', tidyType env' ty)
741 env' = tidyFreeTyVars env (tyVarsOfType ty)
743 tidyOpenTypes :: TidyEnv -> [Type] -> (TidyEnv, [Type])
744 tidyOpenTypes env tys = mapAccumL tidyOpenType env tys
746 tidyTopType :: Type -> Type
747 tidyTopType ty = tidyType emptyTidyEnv ty
752 %************************************************************************
754 \subsection{Liftedness}
756 %************************************************************************
759 isUnLiftedType :: Type -> Bool
760 -- isUnLiftedType returns True for forall'd unlifted types:
761 -- x :: forall a. Int#
762 -- I found bindings like these were getting floated to the top level.
763 -- They are pretty bogus types, mind you. It would be better never to
766 isUnLiftedType (ForAllTy tv ty) = isUnLiftedType ty
767 isUnLiftedType (NoteTy _ ty) = isUnLiftedType ty
768 isUnLiftedType (TyConApp tc _) = isUnLiftedTyCon tc
769 isUnLiftedType (PredTy _) = False -- All source types are lifted
770 isUnLiftedType (NewTcApp tc tys) = isUnLiftedType (newTypeRep tc tys)
771 isUnLiftedType other = False
773 isUnboxedTupleType :: Type -> Bool
774 isUnboxedTupleType ty = case splitTyConApp_maybe ty of
775 Just (tc, ty_args) -> isUnboxedTupleTyCon tc
778 -- Should only be applied to *types*; hence the assert
779 isAlgType :: Type -> Bool
780 isAlgType ty = case splitTyConApp_maybe ty of
781 Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc )
786 @isStrictType@ computes whether an argument (or let RHS) should
787 be computed strictly or lazily, based only on its type.
788 Works just like isUnLiftedType, except that it has a special case
789 for dictionaries. Since it takes account of ClassP, you might think
790 this function should be in TcType, but isStrictType is used by DataCon,
791 which is below TcType in the hierarchy, so it's convenient to put it here.
794 isStrictType (ForAllTy tv ty) = isStrictType ty
795 isStrictType (NoteTy _ ty) = isStrictType ty
796 isStrictType (TyConApp tc _) = isUnLiftedTyCon tc
797 isStrictType (NewTcApp tc tys) = isStrictType (newTypeRep tc tys)
798 isStrictType (PredTy pred) = isStrictPred pred
799 isStrictType other = False
801 isStrictPred (ClassP clas _) = opt_DictsStrict && not (isNewTyCon (classTyCon clas))
802 isStrictPred other = False
803 -- We may be strict in dictionary types, but only if it
804 -- has more than one component.
805 -- [Being strict in a single-component dictionary risks
806 -- poking the dictionary component, which is wrong.]
810 isPrimitiveType :: Type -> Bool
811 -- Returns types that are opaque to Haskell.
812 -- Most of these are unlifted, but now that we interact with .NET, we
813 -- may have primtive (foreign-imported) types that are lifted
814 isPrimitiveType ty = case splitTyConApp_maybe ty of
815 Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc )
821 %************************************************************************
823 \subsection{Sequencing on types
825 %************************************************************************
828 seqType :: Type -> ()
829 seqType (TyVarTy tv) = tv `seq` ()
830 seqType (AppTy t1 t2) = seqType t1 `seq` seqType t2
831 seqType (FunTy t1 t2) = seqType t1 `seq` seqType t2
832 seqType (NoteTy note t2) = seqNote note `seq` seqType t2
833 seqType (PredTy p) = seqPred p
834 seqType (TyConApp tc tys) = tc `seq` seqTypes tys
835 seqType (NewTcApp tc tys) = tc `seq` seqTypes tys
836 seqType (ForAllTy tv ty) = tv `seq` seqType ty
838 seqTypes :: [Type] -> ()
840 seqTypes (ty:tys) = seqType ty `seq` seqTypes tys
842 seqNote :: TyNote -> ()
843 seqNote (SynNote ty) = seqType ty
844 seqNote (FTVNote set) = sizeUniqSet set `seq` ()
846 seqPred :: PredType -> ()
847 seqPred (ClassP c tys) = c `seq` seqTypes tys
848 seqPred (IParam n ty) = n `seq` seqType ty
852 %************************************************************************
854 \subsection{Equality on types}
856 %************************************************************************
858 Comparison; don't use instances so that we know where it happens.
859 Look through newtypes but not usage types.
861 Note that eqType can respond 'False' for partial applications of newtypes.
863 newtype Parser m a = MkParser (Foogle m a)
866 Monad (Parser m) `eqType` Monad (Foogle m)
868 Well, yes, but eqType won't see that they are the same.
869 I don't think this is harmful, but it's soemthing to watch out for.
872 eqType t1 t2 = eq_ty emptyVarEnv t1 t2
874 -- Look through Notes
875 eq_ty env (NoteTy _ t1) t2 = eq_ty env t1 t2
876 eq_ty env t1 (NoteTy _ t2) = eq_ty env t1 t2
878 -- Look through PredTy and NewTcApp. This is where the looping danger comes from.
879 -- We don't bother to check for the PredType/PredType case, no good reason
880 -- Hmm: maybe there is a good reason: see the notes below about newtypes
881 eq_ty env (PredTy sty1) t2 = eq_ty env (predTypeRep sty1) t2
882 eq_ty env t1 (PredTy sty2) = eq_ty env t1 (predTypeRep sty2)
884 -- NB: we *cannot* short-cut the newtype comparison thus:
885 -- eq_ty env (NewTcApp tc1 tys1) (NewTcApp tc2 tys2)
886 -- | (tc1 == tc2) = (eq_tys env tys1 tys2)
889 -- newtype T a = MkT [a]
890 -- newtype Foo m = MkFoo (forall a. m a -> Int)
895 -- w2 = MkFoo (\(MkT x) -> case w1 of MkFoo f -> f x)
897 -- We end up with w2 = w1; so we need that Foo T = Foo []
898 -- but we can only expand saturated newtypes, so just comparing
899 -- T with [] won't do.
901 eq_ty env (NewTcApp tc1 tys1) t2 = eq_ty env (newTypeRep tc1 tys1) t2
902 eq_ty env t1 (NewTcApp tc2 tys2) = eq_ty env t1 (newTypeRep tc2 tys2)
904 -- The rest is plain sailing
905 eq_ty env (TyVarTy tv1) (TyVarTy tv2) = case lookupVarEnv env tv1 of
906 Just tv1a -> tv1a == tv2
907 Nothing -> tv1 == tv2
908 eq_ty env (ForAllTy tv1 t1) (ForAllTy tv2 t2)
909 | tv1 == tv2 = eq_ty (delVarEnv env tv1) t1 t2
910 | otherwise = eq_ty (extendVarEnv env tv1 tv2) t1 t2
911 eq_ty env (AppTy s1 t1) (AppTy s2 t2) = (eq_ty env s1 s2) && (eq_ty env t1 t2)
912 eq_ty env (FunTy s1 t1) (FunTy s2 t2) = (eq_ty env s1 s2) && (eq_ty env t1 t2)
913 eq_ty env (TyConApp tc1 tys1) (TyConApp tc2 tys2) = (tc1 == tc2) && (eq_tys env tys1 tys2)
914 eq_ty env t1 t2 = False
916 eq_tys env [] [] = True
917 eq_tys env (t1:tys1) (t2:tys2) = (eq_ty env t1 t2) && (eq_tys env tys1 tys2)
918 eq_tys env tys1 tys2 = False