2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[TcType]{Types used in the typechecker}
6 This module provides the Type interface for front-end parts of the
9 * treat "source types" as opaque:
10 newtypes, and predicates are meaningful.
11 * look through usage types
13 The "tc" prefix is for "typechechecker", because the type checker
14 is the principal client.
18 --------------------------------
20 TcType, TcSigmaType, TcRhoType, TcTauType, TcPredType, TcThetaType,
21 TcTyVar, TcTyVarSet, TcKind,
23 --------------------------------
25 TyVarDetails(..), isUserTyVar, isSkolemTyVar, isHoleTyVar,
28 --------------------------------
32 --------------------------------
34 -- These are important because they do not look through newtypes
35 tcSplitForAllTys, tcSplitPhiTy,
36 tcSplitFunTy_maybe, tcSplitFunTys, tcFunArgTy, tcFunResultTy,
37 tcSplitTyConApp, tcSplitTyConApp_maybe, tcTyConAppTyCon, tcTyConAppArgs,
38 tcSplitAppTy_maybe, tcSplitAppTy, tcSplitSigmaTy,
39 tcSplitMethodTy, tcGetTyVar_maybe, tcGetTyVar,
41 ---------------------------------
43 -- Again, newtypes are opaque
44 tcEqType, tcEqTypes, tcEqPred, tcCmpType, tcCmpTypes, tcCmpPred,
45 isSigmaTy, isOverloadedTy,
46 isDoubleTy, isFloatTy, isIntTy,
47 isIntegerTy, isAddrTy, isBoolTy, isUnitTy, isForeignPtrTy,
48 isTauTy, tcIsTyVarTy, tcIsForAllTy,
51 ---------------------------------
52 -- Misc type manipulators
53 hoistForAllTys, deNoteType,
54 namesOfType, namesOfDFunHead,
57 ---------------------------------
59 PredType, getClassPredTys_maybe, getClassPredTys,
60 isPredTy, isClassPred, isTyVarClassPred, predHasFDs,
61 mkDictTy, tcSplitPredTy_maybe, predTyUnique,
62 isDictTy, tcSplitDFunTy, predTyUnique,
63 mkClassPred, isInheritablePred, isLinearPred, isIPPred, mkPredName,
65 ---------------------------------
66 -- Foreign import and export
67 isFFIArgumentTy, -- :: DynFlags -> Safety -> Type -> Bool
68 isFFIImportResultTy, -- :: DynFlags -> Type -> Bool
69 isFFIExportResultTy, -- :: Type -> Bool
70 isFFIExternalTy, -- :: Type -> Bool
71 isFFIDynArgumentTy, -- :: Type -> Bool
72 isFFIDynResultTy, -- :: Type -> Bool
73 isFFILabelTy, -- :: Type -> Bool
75 ---------------------------------
76 -- Unifier and matcher
77 unifyTysX, unifyTyListsX, unifyExtendTysX,
78 matchTy, matchTys, match,
80 --------------------------------
81 -- Rexported from Type
82 Kind, -- Stuff to do with kinds is insensitive to pre/post Tc
83 unliftedTypeKind, liftedTypeKind, openTypeKind, mkArrowKind, mkArrowKinds,
84 superBoxity, liftedBoxity, hasMoreBoxityInfo, defaultKind, superKind,
85 isTypeKind, isAnyTypeKind,
87 Type, SourceType(..), PredType, ThetaType,
88 mkForAllTy, mkForAllTys,
89 mkFunTy, mkFunTys, zipFunTys,
90 mkTyConApp, mkGenTyConApp, mkAppTy, mkAppTys, mkSynTy, applyTy, applyTys,
91 mkTyVarTy, mkTyVarTys, mkTyConTy, mkPredTy, mkPredTys,
93 isUnLiftedType, -- Source types are always lifted
94 isUnboxedTupleType, -- Ditto
97 tidyTopType, tidyType, tidyPred, tidyTypes, tidyFreeTyVars, tidyOpenType, tidyOpenTypes,
98 tidyTyVarBndr, tidyOpenTyVar, tidyOpenTyVars,
99 typeKind, eqKind, eqUsage,
101 tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tyVarsOfTheta
104 #include "HsVersions.h"
107 import {-# SOURCE #-} PprType( pprType )
110 import TypeRep ( Type(..), TyNote(..), funTyCon ) -- friend
112 import Type ( -- Re-exports
113 tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tyVarsOfTheta,
114 Kind, Type, SourceType(..), PredType, ThetaType,
115 unliftedTypeKind, liftedTypeKind, openTypeKind, mkArrowKind, mkArrowKinds,
116 mkForAllTy, mkForAllTys, defaultKind, isTypeKind, isAnyTypeKind,
117 mkFunTy, mkFunTys, zipFunTys,
118 mkTyConApp, mkGenTyConApp, mkAppTy, mkAppTys, mkSynTy, applyTy, applyTys,
119 mkTyVarTy, mkTyVarTys, mkTyConTy, mkPredTy, mkPredTys,
120 isUnLiftedType, isUnboxedTupleType, isPrimitiveType,
121 splitNewType_maybe, splitTyConApp_maybe,
122 tidyTopType, tidyType, tidyPred, tidyTypes, tidyFreeTyVars, tidyOpenType, tidyOpenTypes,
123 tidyTyVarBndr, tidyOpenTyVar, tidyOpenTyVars, eqKind, eqUsage,
124 hasMoreBoxityInfo, liftedBoxity, superBoxity, typeKind, superKind
126 import TyCon ( TyCon, isUnLiftedTyCon )
127 import Class ( classHasFDs, Class )
128 import Var ( TyVar, tyVarKind, isMutTyVar, mutTyVarDetails )
129 import ForeignCall ( Safety, playSafe )
134 import CmdLineOpts ( DynFlags, DynFlag( Opt_GlasgowExts ), dopt )
135 import Name ( Name, NamedThing(..), mkInternalName, getSrcLoc )
136 import OccName ( OccName, mkDictOcc )
138 import PrelNames -- Lots (e.g. in isFFIArgumentTy)
139 import TysWiredIn ( ptrTyCon, funPtrTyCon, addrTyCon, unitTyCon )
140 import BasicTypes ( IPName(..), ipNameName )
141 import Unique ( Unique, Uniquable(..) )
142 import SrcLoc ( SrcLoc )
143 import Util ( cmpList, thenCmp, equalLength )
144 import Maybes ( maybeToBool, expectJust )
149 %************************************************************************
153 %************************************************************************
155 The type checker divides the generic Type world into the
156 following more structured beasts:
158 sigma ::= forall tyvars. phi
159 -- A sigma type is a qualified type
161 -- Note that even if 'tyvars' is empty, theta
162 -- may not be: e.g. (?x::Int) => Int
164 -- Note that 'sigma' is in prenex form:
165 -- all the foralls are at the front.
166 -- A 'phi' type has no foralls to the right of
174 -- A 'tau' type has no quantification anywhere
175 -- Note that the args of a type constructor must be taus
177 | tycon tau_1 .. tau_n
181 -- In all cases, a (saturated) type synonym application is legal,
182 -- provided it expands to the required form.
186 type SigmaType = Type
192 type TcTyVar = TyVar -- Might be a mutable tyvar
193 type TcTyVarSet = TyVarSet
195 type TcType = Type -- A TcType can have mutable type variables
196 -- Invariant on ForAllTy in TcTypes:
198 -- a cannot occur inside a MutTyVar in T; that is,
199 -- T is "flattened" before quantifying over a
201 type TcPredType = PredType
202 type TcThetaType = ThetaType
203 type TcSigmaType = TcType
204 type TcRhoType = TcType
205 type TcTauType = TcType
210 %************************************************************************
212 \subsection{TyVarDetails}
214 %************************************************************************
216 TyVarDetails gives extra info about type variables, used during type
217 checking. It's attached to mutable type variables only.
218 It's knot-tied back to Var.lhs. There is no reason in principle
219 why Var.lhs shouldn't actually have the definition, but it "belongs" here.
223 = HoleTv -- Used *only* by the type checker when passing in a type
224 -- variable that should be side-effected to the result type.
225 -- Always has kind openTypeKind.
226 -- Never appears in types
228 | SigTv -- Introduced when instantiating a type signature,
229 -- prior to checking that the defn of a fn does
230 -- have the expected type. Should not be instantiated.
232 -- f :: forall a. a -> a
234 -- When checking e, with expected type (a->a), we
235 -- should not instantiate a
237 | ClsTv -- Scoped type variable introduced by a class decl
238 -- class C a where ...
240 | InstTv -- Ditto, but instance decl
242 | PatSigTv -- Scoped type variable, introduced by a pattern
246 | VanillaTv -- Everything else
248 isUserTyVar :: TcTyVar -> Bool -- Avoid unifying these if possible
249 isUserTyVar tv = case mutTyVarDetails tv of
253 isSkolemTyVar :: TcTyVar -> Bool
254 isSkolemTyVar tv = case mutTyVarDetails tv of
260 isHoleTyVar :: TcTyVar -> Bool
261 -- NB: the hole might be filled in by now, and this
262 -- function does not check for that
263 isHoleTyVar tv = ASSERT( isMutTyVar tv )
264 case mutTyVarDetails tv of
268 tyVarBindingInfo :: TyVar -> SDoc -- Used in checkSigTyVars
271 = sep [ptext SLIT("is bound by the") <+> details (mutTyVarDetails tv),
272 ptext SLIT("at") <+> ppr (getSrcLoc tv)]
276 details SigTv = ptext SLIT("type signature")
277 details ClsTv = ptext SLIT("class declaration")
278 details InstTv = ptext SLIT("instance declaration")
279 details PatSigTv = ptext SLIT("pattern type signature")
280 details HoleTv = ptext SLIT("//hole//") -- Should not happen
281 details VanillaTv = ptext SLIT("//vanilla//") -- Ditto
285 %************************************************************************
287 \subsection{Tau, sigma and rho}
289 %************************************************************************
292 mkSigmaTy tyvars theta tau = mkForAllTys tyvars (mkPhiTy theta tau)
294 mkPhiTy :: [SourceType] -> Type -> Type
295 mkPhiTy theta ty = foldr (\p r -> FunTy (mkPredTy p) r) ty theta
299 @isTauTy@ tests for nested for-alls.
302 isTauTy :: Type -> Bool
303 isTauTy (TyVarTy v) = True
304 isTauTy (TyConApp _ tys) = all isTauTy tys
305 isTauTy (AppTy a b) = isTauTy a && isTauTy b
306 isTauTy (FunTy a b) = isTauTy a && isTauTy b
307 isTauTy (SourceTy p) = True -- Don't look through source types
308 isTauTy (NoteTy _ ty) = isTauTy ty
309 isTauTy other = False
313 getDFunTyKey :: Type -> OccName -- Get some string from a type, to be used to
314 -- construct a dictionary function name
315 getDFunTyKey (TyVarTy tv) = getOccName tv
316 getDFunTyKey (TyConApp tc _) = getOccName tc
317 getDFunTyKey (AppTy fun _) = getDFunTyKey fun
318 getDFunTyKey (NoteTy _ t) = getDFunTyKey t
319 getDFunTyKey (FunTy arg _) = getOccName funTyCon
320 getDFunTyKey (ForAllTy _ t) = getDFunTyKey t
321 getDFunTyKey (SourceTy (NType tc _)) = getOccName tc -- Newtypes are quite reasonable
322 getDFunTyKey ty = pprPanic "getDFunTyKey" (pprType ty)
323 -- SourceTy shouldn't happen
327 %************************************************************************
329 \subsection{Expanding and splitting}
331 %************************************************************************
333 These tcSplit functions are like their non-Tc analogues, but
334 a) they do not look through newtypes
335 b) they do not look through PredTys
336 c) [future] they ignore usage-type annotations
338 However, they are non-monadic and do not follow through mutable type
339 variables. It's up to you to make sure this doesn't matter.
342 tcSplitForAllTys :: Type -> ([TyVar], Type)
343 tcSplitForAllTys ty = split ty ty []
345 split orig_ty (ForAllTy tv ty) tvs = split ty ty (tv:tvs)
346 split orig_ty (NoteTy n ty) tvs = split orig_ty ty tvs
347 split orig_ty t tvs = (reverse tvs, orig_ty)
349 tcIsForAllTy (ForAllTy tv ty) = True
350 tcIsForAllTy (NoteTy n ty) = tcIsForAllTy ty
351 tcIsForAllTy t = False
353 tcSplitPhiTy :: Type -> ([PredType], Type)
354 tcSplitPhiTy ty = split ty ty []
356 split orig_ty (FunTy arg res) ts = case tcSplitPredTy_maybe arg of
357 Just p -> split res res (p:ts)
358 Nothing -> (reverse ts, orig_ty)
359 split orig_ty (NoteTy n ty) ts = split orig_ty ty ts
360 split orig_ty ty ts = (reverse ts, orig_ty)
362 tcSplitSigmaTy ty = case tcSplitForAllTys ty of
363 (tvs, rho) -> case tcSplitPhiTy rho of
364 (theta, tau) -> (tvs, theta, tau)
366 tcTyConAppTyCon :: Type -> TyCon
367 tcTyConAppTyCon ty = fst (tcSplitTyConApp ty)
369 tcTyConAppArgs :: Type -> [Type]
370 tcTyConAppArgs ty = snd (tcSplitTyConApp ty)
372 tcSplitTyConApp :: Type -> (TyCon, [Type])
373 tcSplitTyConApp ty = case tcSplitTyConApp_maybe ty of
375 Nothing -> pprPanic "tcSplitTyConApp" (pprType ty)
377 tcSplitTyConApp_maybe :: Type -> Maybe (TyCon, [Type])
378 tcSplitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
379 tcSplitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res])
380 tcSplitTyConApp_maybe (NoteTy n ty) = tcSplitTyConApp_maybe ty
381 tcSplitTyConApp_maybe (SourceTy (NType tc tys)) = Just (tc,tys)
382 -- Newtypes are opaque, so they may be split
383 -- However, predicates are not treated
384 -- as tycon applications by the type checker
385 tcSplitTyConApp_maybe other = Nothing
387 tcSplitFunTys :: Type -> ([Type], Type)
388 tcSplitFunTys ty = case tcSplitFunTy_maybe ty of
390 Just (arg,res) -> (arg:args, res')
392 (args,res') = tcSplitFunTys res
394 tcSplitFunTy_maybe :: Type -> Maybe (Type, Type)
395 tcSplitFunTy_maybe (FunTy arg res) = Just (arg, res)
396 tcSplitFunTy_maybe (NoteTy n ty) = tcSplitFunTy_maybe ty
397 tcSplitFunTy_maybe other = Nothing
399 tcFunArgTy ty = case tcSplitFunTy_maybe ty of { Just (arg,res) -> arg }
400 tcFunResultTy ty = case tcSplitFunTy_maybe ty of { Just (arg,res) -> res }
403 tcSplitAppTy_maybe :: Type -> Maybe (Type, Type)
404 tcSplitAppTy_maybe (FunTy ty1 ty2) = Just (TyConApp funTyCon [ty1], ty2)
405 tcSplitAppTy_maybe (AppTy ty1 ty2) = Just (ty1, ty2)
406 tcSplitAppTy_maybe (NoteTy n ty) = tcSplitAppTy_maybe ty
407 tcSplitAppTy_maybe (SourceTy (NType tc tys)) = tc_split_app tc tys
408 --- Don't forget that newtype!
409 tcSplitAppTy_maybe (TyConApp tc tys) = tc_split_app tc tys
410 tcSplitAppTy_maybe other = Nothing
412 tc_split_app tc [] = Nothing
413 tc_split_app tc tys = split tys []
415 split [ty2] acc = Just (TyConApp tc (reverse acc), ty2)
416 split (ty:tys) acc = split tys (ty:acc)
418 tcSplitAppTy ty = case tcSplitAppTy_maybe ty of
420 Nothing -> pprPanic "tcSplitAppTy" (pprType ty)
422 tcGetTyVar_maybe :: Type -> Maybe TyVar
423 tcGetTyVar_maybe (TyVarTy tv) = Just tv
424 tcGetTyVar_maybe (NoteTy _ t) = tcGetTyVar_maybe t
425 tcGetTyVar_maybe other = Nothing
427 tcGetTyVar :: String -> Type -> TyVar
428 tcGetTyVar msg ty = expectJust msg (tcGetTyVar_maybe ty)
430 tcIsTyVarTy :: Type -> Bool
431 tcIsTyVarTy ty = maybeToBool (tcGetTyVar_maybe ty)
434 The type of a method for class C is always of the form:
435 Forall a1..an. C a1..an => sig_ty
436 where sig_ty is the type given by the method's signature, and thus in general
437 is a ForallTy. At the point that splitMethodTy is called, it is expected
438 that the outer Forall has already been stripped off. splitMethodTy then
439 returns (C a1..an, sig_ty') where sig_ty' is sig_ty with any Notes or
443 tcSplitMethodTy :: Type -> (PredType, Type)
444 tcSplitMethodTy ty = split ty
446 split (FunTy arg res) = case tcSplitPredTy_maybe arg of
448 Nothing -> panic "splitMethodTy"
449 split (NoteTy n ty) = split ty
450 split _ = panic "splitMethodTy"
452 tcSplitDFunTy :: Type -> ([TyVar], [SourceType], Class, [Type])
453 -- Split the type of a dictionary function
455 = case tcSplitSigmaTy ty of { (tvs, theta, tau) ->
456 case tcSplitPredTy_maybe tau of { Just (ClassP clas tys) ->
457 (tvs, theta, clas, tys) }}
460 (allDistinctTyVars tys tvs) = True
462 all the types tys are type variables,
463 distinct from each other and from tvs.
465 This is useful when checking that unification hasn't unified signature
466 type variables. For example, if the type sig is
467 f :: forall a b. a -> b -> b
468 we want to check that 'a' and 'b' havn't
469 (a) been unified with a non-tyvar type
470 (b) been unified with each other (all distinct)
471 (c) been unified with a variable free in the environment
474 allDistinctTyVars :: [Type] -> TyVarSet -> Bool
476 allDistinctTyVars [] acc
478 allDistinctTyVars (ty:tys) acc
479 = case tcGetTyVar_maybe ty of
480 Nothing -> False -- (a)
481 Just tv | tv `elemVarSet` acc -> False -- (b) or (c)
482 | otherwise -> allDistinctTyVars tys (acc `extendVarSet` tv)
486 %************************************************************************
488 \subsection{Predicate types}
490 %************************************************************************
492 "Predicates" are particular source types, namelyClassP or IParams
495 isPred :: SourceType -> Bool
496 isPred (ClassP _ _) = True
497 isPred (IParam _ _) = True
498 isPred (NType _ _) = False
500 isPredTy :: Type -> Bool
501 isPredTy (NoteTy _ ty) = isPredTy ty
502 isPredTy (SourceTy sty) = isPred sty
505 tcSplitPredTy_maybe :: Type -> Maybe PredType
506 -- Returns Just for predicates only
507 tcSplitPredTy_maybe (NoteTy _ ty) = tcSplitPredTy_maybe ty
508 tcSplitPredTy_maybe (SourceTy p) | isPred p = Just p
509 tcSplitPredTy_maybe other = Nothing
511 predTyUnique :: PredType -> Unique
512 predTyUnique (IParam n _) = getUnique (ipNameName n)
513 predTyUnique (ClassP clas tys) = getUnique clas
515 predHasFDs :: PredType -> Bool
516 -- True if the predicate has functional depenencies;
517 -- I.e. should participate in improvement
518 predHasFDs (IParam _ _) = True
519 predHasFDs (ClassP cls _) = classHasFDs cls
521 mkPredName :: Unique -> SrcLoc -> SourceType -> Name
522 mkPredName uniq loc (ClassP cls tys) = mkInternalName uniq (mkDictOcc (getOccName cls)) loc
523 mkPredName uniq loc (IParam ip ty) = mkInternalName uniq (getOccName (ipNameName ip)) loc
527 --------------------- Dictionary types ---------------------------------
530 mkClassPred clas tys = ClassP clas tys
532 isClassPred :: SourceType -> Bool
533 isClassPred (ClassP clas tys) = True
534 isClassPred other = False
536 isTyVarClassPred (ClassP clas tys) = all tcIsTyVarTy tys
537 isTyVarClassPred other = False
539 getClassPredTys_maybe :: SourceType -> Maybe (Class, [Type])
540 getClassPredTys_maybe (ClassP clas tys) = Just (clas, tys)
541 getClassPredTys_maybe _ = Nothing
543 getClassPredTys :: PredType -> (Class, [Type])
544 getClassPredTys (ClassP clas tys) = (clas, tys)
546 mkDictTy :: Class -> [Type] -> Type
547 mkDictTy clas tys = mkPredTy (ClassP clas tys)
549 isDictTy :: Type -> Bool
550 isDictTy (SourceTy p) = isClassPred p
551 isDictTy (NoteTy _ ty) = isDictTy ty
552 isDictTy other = False
555 --------------------- Implicit parameters ---------------------------------
558 isIPPred :: SourceType -> Bool
559 isIPPred (IParam _ _) = True
560 isIPPred other = False
562 isInheritablePred :: PredType -> Bool
563 -- Can be inherited by a context. For example, consider
564 -- f x = let g y = (?v, y+x)
565 -- in (g 3 with ?v = 8,
567 -- The point is that g's type must be quantifed over ?v:
568 -- g :: (?v :: a) => a -> a
569 -- but it doesn't need to be quantified over the Num a dictionary
570 -- which can be free in g's rhs, and shared by both calls to g
571 isInheritablePred (ClassP _ _) = True
572 isInheritablePred other = False
574 isLinearPred :: TcPredType -> Bool
575 isLinearPred (IParam (Linear n) _) = True
576 isLinearPred other = False
580 %************************************************************************
582 \subsection{Comparison}
584 %************************************************************************
586 Comparison, taking note of newtypes, predicates, etc,
587 But ignoring usage types
590 tcEqType :: Type -> Type -> Bool
591 tcEqType ty1 ty2 = case ty1 `tcCmpType` ty2 of { EQ -> True; other -> False }
593 tcEqTypes :: [Type] -> [Type] -> Bool
594 tcEqTypes ty1 ty2 = case ty1 `tcCmpTypes` ty2 of { EQ -> True; other -> False }
596 tcEqPred :: PredType -> PredType -> Bool
597 tcEqPred p1 p2 = case p1 `tcCmpPred` p2 of { EQ -> True; other -> False }
600 tcCmpType :: Type -> Type -> Ordering
601 tcCmpType ty1 ty2 = cmpTy emptyVarEnv ty1 ty2
603 tcCmpTypes tys1 tys2 = cmpTys emptyVarEnv tys1 tys2
605 tcCmpPred p1 p2 = cmpSourceTy emptyVarEnv p1 p2
607 cmpTys env tys1 tys2 = cmpList (cmpTy env) tys1 tys2
610 cmpTy :: TyVarEnv TyVar -> Type -> Type -> Ordering
611 -- The "env" maps type variables in ty1 to type variables in ty2
612 -- So when comparing for-alls.. (forall tv1 . t1) (forall tv2 . t2)
613 -- we in effect substitute tv2 for tv1 in t1 before continuing
615 -- Look through NoteTy
616 cmpTy env (NoteTy _ ty1) ty2 = cmpTy env ty1 ty2
617 cmpTy env ty1 (NoteTy _ ty2) = cmpTy env ty1 ty2
619 -- Deal with equal constructors
620 cmpTy env (TyVarTy tv1) (TyVarTy tv2) = case lookupVarEnv env tv1 of
621 Just tv1a -> tv1a `compare` tv2
622 Nothing -> tv1 `compare` tv2
624 cmpTy env (SourceTy p1) (SourceTy p2) = cmpSourceTy env p1 p2
625 cmpTy env (AppTy f1 a1) (AppTy f2 a2) = cmpTy env f1 f2 `thenCmp` cmpTy env a1 a2
626 cmpTy env (FunTy f1 a1) (FunTy f2 a2) = cmpTy env f1 f2 `thenCmp` cmpTy env a1 a2
627 cmpTy env (TyConApp tc1 tys1) (TyConApp tc2 tys2) = (tc1 `compare` tc2) `thenCmp` (cmpTys env tys1 tys2)
628 cmpTy env (ForAllTy tv1 t1) (ForAllTy tv2 t2) = cmpTy (extendVarEnv env tv1 tv2) t1 t2
630 -- Deal with the rest: TyVarTy < AppTy < FunTy < TyConApp < ForAllTy < SourceTy
631 cmpTy env (AppTy _ _) (TyVarTy _) = GT
633 cmpTy env (FunTy _ _) (TyVarTy _) = GT
634 cmpTy env (FunTy _ _) (AppTy _ _) = GT
636 cmpTy env (TyConApp _ _) (TyVarTy _) = GT
637 cmpTy env (TyConApp _ _) (AppTy _ _) = GT
638 cmpTy env (TyConApp _ _) (FunTy _ _) = GT
640 cmpTy env (ForAllTy _ _) (TyVarTy _) = GT
641 cmpTy env (ForAllTy _ _) (AppTy _ _) = GT
642 cmpTy env (ForAllTy _ _) (FunTy _ _) = GT
643 cmpTy env (ForAllTy _ _) (TyConApp _ _) = GT
645 cmpTy env (SourceTy _) t2 = GT
651 cmpSourceTy :: TyVarEnv TyVar -> SourceType -> SourceType -> Ordering
652 cmpSourceTy env (IParam n1 ty1) (IParam n2 ty2) = (n1 `compare` n2) `thenCmp` (cmpTy env ty1 ty2)
653 -- Compare types as well as names for implicit parameters
654 -- This comparison is used exclusively (I think) for the
655 -- finite map built in TcSimplify
656 cmpSourceTy env (IParam _ _) sty = LT
658 cmpSourceTy env (ClassP _ _) (IParam _ _) = GT
659 cmpSourceTy env (ClassP c1 tys1) (ClassP c2 tys2) = (c1 `compare` c2) `thenCmp` (cmpTys env tys1 tys2)
660 cmpSourceTy env (ClassP _ _) (NType _ _) = LT
662 cmpSourceTy env (NType tc1 tys1) (NType tc2 tys2) = (tc1 `compare` tc2) `thenCmp` (cmpTys env tys1 tys2)
663 cmpSourceTy env (NType _ _) sty = GT
666 PredTypes are used as a FM key in TcSimplify,
667 so we take the easy path and make them an instance of Ord
670 instance Eq SourceType where { (==) = tcEqPred }
671 instance Ord SourceType where { compare = tcCmpPred }
675 %************************************************************************
677 \subsection{Predicates}
679 %************************************************************************
681 isSigmaTy returns true of any qualified type. It doesn't *necessarily* have
683 f :: (?x::Int) => Int -> Int
686 isSigmaTy :: Type -> Bool
687 isSigmaTy (ForAllTy tyvar ty) = True
688 isSigmaTy (FunTy a b) = isPredTy a
689 isSigmaTy (NoteTy n ty) = isSigmaTy ty
692 isOverloadedTy :: Type -> Bool
693 isOverloadedTy (ForAllTy tyvar ty) = isOverloadedTy ty
694 isOverloadedTy (FunTy a b) = isPredTy a
695 isOverloadedTy (NoteTy n ty) = isOverloadedTy ty
696 isOverloadedTy _ = False
700 isFloatTy = is_tc floatTyConKey
701 isDoubleTy = is_tc doubleTyConKey
702 isForeignPtrTy = is_tc foreignPtrTyConKey
703 isIntegerTy = is_tc integerTyConKey
704 isIntTy = is_tc intTyConKey
705 isAddrTy = is_tc addrTyConKey
706 isBoolTy = is_tc boolTyConKey
707 isUnitTy = is_tc unitTyConKey
709 is_tc :: Unique -> Type -> Bool
710 -- Newtypes are opaque to this
711 is_tc uniq ty = case tcSplitTyConApp_maybe ty of
712 Just (tc, _) -> uniq == getUnique tc
717 %************************************************************************
721 %************************************************************************
724 hoistForAllTys :: Type -> Type
725 -- Used for user-written type signatures only
726 -- Move all the foralls and constraints to the top
727 -- e.g. T -> forall a. a ==> forall a. T -> a
728 -- T -> (?x::Int) -> Int ==> (?x::Int) -> T -> Int
730 -- We want to 'look through' type synonyms when doing this
731 -- so it's better done on the Type than the HsType
734 = case hoist ty ty of
735 (tvs, theta, body) -> mkForAllTys tvs (mkFunTys theta body)
737 hoist orig_ty (ForAllTy tv ty) = case hoist ty ty of
738 (tvs,theta,tau) -> (tv:tvs,theta,tau)
739 hoist orig_ty (FunTy arg res)
740 | isPredTy arg = case hoist res res of
741 (tvs,theta,tau) -> (tvs,arg:theta,tau)
742 | otherwise = case hoist res res of
743 (tvs,theta,tau) -> (tvs,theta,mkFunTy arg tau)
745 hoist orig_ty (NoteTy _ ty) = hoist orig_ty ty
746 hoist orig_ty ty = ([], [], orig_ty)
751 deNoteType :: Type -> Type
752 -- Remove synonyms, but not source types
753 deNoteType ty@(TyVarTy tyvar) = ty
754 deNoteType (TyConApp tycon tys) = TyConApp tycon (map deNoteType tys)
755 deNoteType (SourceTy p) = SourceTy (deNoteSourceType p)
756 deNoteType (NoteTy _ ty) = deNoteType ty
757 deNoteType (AppTy fun arg) = AppTy (deNoteType fun) (deNoteType arg)
758 deNoteType (FunTy fun arg) = FunTy (deNoteType fun) (deNoteType arg)
759 deNoteType (ForAllTy tv ty) = ForAllTy tv (deNoteType ty)
761 deNoteSourceType :: SourceType -> SourceType
762 deNoteSourceType (ClassP c tys) = ClassP c (map deNoteType tys)
763 deNoteSourceType (IParam n ty) = IParam n (deNoteType ty)
764 deNoteSourceType (NType tc tys) = NType tc (map deNoteType tys)
767 Find the free names of a type, including the type constructors and classes it mentions
768 This is used in the front end of the compiler
771 namesOfType :: Type -> NameSet
772 namesOfType (TyVarTy tv) = unitNameSet (getName tv)
773 namesOfType (TyConApp tycon tys) = unitNameSet (getName tycon) `unionNameSets` namesOfTypes tys
774 namesOfType (NoteTy (SynNote ty1) ty2) = namesOfType ty1
775 namesOfType (NoteTy other_note ty2) = namesOfType ty2
776 namesOfType (SourceTy (IParam n ty)) = namesOfType ty
777 namesOfType (SourceTy (ClassP cl tys)) = unitNameSet (getName cl) `unionNameSets` namesOfTypes tys
778 namesOfType (SourceTy (NType tc tys)) = unitNameSet (getName tc) `unionNameSets` namesOfTypes tys
779 namesOfType (FunTy arg res) = namesOfType arg `unionNameSets` namesOfType res
780 namesOfType (AppTy fun arg) = namesOfType fun `unionNameSets` namesOfType arg
781 namesOfType (ForAllTy tyvar ty) = namesOfType ty `delFromNameSet` getName tyvar
783 namesOfTypes tys = foldr (unionNameSets . namesOfType) emptyNameSet tys
785 namesOfDFunHead :: Type -> NameSet
786 -- Find the free type constructors and classes
787 -- of the head of the dfun instance type
788 -- The 'dfun_head_type' is because of
789 -- instance Foo a => Baz T where ...
790 -- The decl is an orphan if Baz and T are both not locally defined,
791 -- even if Foo *is* locally defined
792 namesOfDFunHead dfun_ty = case tcSplitSigmaTy dfun_ty of
793 (tvs,_,head_ty) -> delListFromNameSet (namesOfType head_ty)
798 %************************************************************************
800 \subsection[TysWiredIn-ext-type]{External types}
802 %************************************************************************
804 The compiler's foreign function interface supports the passing of a
805 restricted set of types as arguments and results (the restricting factor
809 isFFIArgumentTy :: DynFlags -> Safety -> Type -> Bool
810 -- Checks for valid argument type for a 'foreign import'
811 isFFIArgumentTy dflags safety ty
812 = checkRepTyCon (legalOutgoingTyCon dflags safety) ty
814 isFFIExternalTy :: Type -> Bool
815 -- Types that are allowed as arguments of a 'foreign export'
816 isFFIExternalTy ty = checkRepTyCon legalFEArgTyCon ty
818 isFFIImportResultTy :: DynFlags -> Type -> Bool
819 isFFIImportResultTy dflags ty
820 = checkRepTyCon (legalFIResultTyCon dflags) ty
822 isFFIExportResultTy :: Type -> Bool
823 isFFIExportResultTy ty = checkRepTyCon legalFEResultTyCon ty
825 isFFIDynArgumentTy :: Type -> Bool
826 -- The argument type of a foreign import dynamic must be Ptr, FunPtr, Addr,
827 -- or a newtype of either.
828 isFFIDynArgumentTy = checkRepTyCon (\tc -> tc == ptrTyCon || tc == funPtrTyCon || tc == addrTyCon)
830 isFFIDynResultTy :: Type -> Bool
831 -- The result type of a foreign export dynamic must be Ptr, FunPtr, Addr,
832 -- or a newtype of either.
833 isFFIDynResultTy = checkRepTyCon (\tc -> tc == ptrTyCon || tc == funPtrTyCon || tc == addrTyCon)
835 isFFILabelTy :: Type -> Bool
836 -- The type of a foreign label must be Ptr, FunPtr, Addr,
837 -- or a newtype of either.
838 isFFILabelTy = checkRepTyCon (\tc -> tc == ptrTyCon || tc == funPtrTyCon || tc == addrTyCon)
840 checkRepTyCon :: (TyCon -> Bool) -> Type -> Bool
841 -- Look through newtypes
842 -- Non-recursive ones are transparent to splitTyConApp,
843 -- but recursive ones aren't; hence the splitNewType_maybe
844 checkRepTyCon check_tc ty
845 | Just ty' <- splitNewType_maybe ty = checkRepTyCon check_tc ty'
846 | Just (tc,_) <- splitTyConApp_maybe ty = check_tc tc
850 ----------------------------------------------
851 These chaps do the work; they are not exported
852 ----------------------------------------------
855 legalFEArgTyCon :: TyCon -> Bool
856 -- It's illegal to return foreign objects and (mutable)
857 -- bytearrays from a _ccall_ / foreign declaration
858 -- (or be passed them as arguments in foreign exported functions).
860 | getUnique tc `elem` [ foreignObjTyConKey, foreignPtrTyConKey,
861 byteArrayTyConKey, mutableByteArrayTyConKey ]
863 -- It's also illegal to make foreign exports that take unboxed
864 -- arguments. The RTS API currently can't invoke such things. --SDM 7/2000
866 = boxedMarshalableTyCon tc
868 legalFIResultTyCon :: DynFlags -> TyCon -> Bool
869 legalFIResultTyCon dflags tc
870 | getUnique tc `elem`
871 [ foreignObjTyConKey, foreignPtrTyConKey,
872 byteArrayTyConKey, mutableByteArrayTyConKey ] = False
873 | tc == unitTyCon = True
874 | otherwise = marshalableTyCon dflags tc
876 legalFEResultTyCon :: TyCon -> Bool
877 legalFEResultTyCon tc
878 | getUnique tc `elem`
879 [ foreignObjTyConKey, foreignPtrTyConKey,
880 byteArrayTyConKey, mutableByteArrayTyConKey ] = False
881 | tc == unitTyCon = True
882 | otherwise = boxedMarshalableTyCon tc
884 legalOutgoingTyCon :: DynFlags -> Safety -> TyCon -> Bool
885 -- Checks validity of types going from Haskell -> external world
886 legalOutgoingTyCon dflags safety tc
887 | playSafe safety && getUnique tc `elem` [byteArrayTyConKey, mutableByteArrayTyConKey]
890 = marshalableTyCon dflags tc
892 marshalableTyCon dflags tc
893 = (dopt Opt_GlasgowExts dflags && isUnLiftedTyCon tc)
894 || boxedMarshalableTyCon tc
896 boxedMarshalableTyCon tc
897 = getUnique tc `elem` [ intTyConKey, int8TyConKey, int16TyConKey
898 , int32TyConKey, int64TyConKey
899 , wordTyConKey, word8TyConKey, word16TyConKey
900 , word32TyConKey, word64TyConKey
901 , floatTyConKey, doubleTyConKey
902 , addrTyConKey, ptrTyConKey, funPtrTyConKey
903 , charTyConKey, foreignObjTyConKey
906 , byteArrayTyConKey, mutableByteArrayTyConKey
912 %************************************************************************
914 \subsection{Unification with an explicit substitution}
916 %************************************************************************
918 Unify types with an explicit substitution and no monad.
919 Ignore usage annotations.
923 = (TyVarSet, -- Set of template tyvars
924 TyVarSubstEnv) -- Not necessarily idempotent
926 unifyTysX :: TyVarSet -- Template tyvars
929 -> Maybe TyVarSubstEnv
930 unifyTysX tmpl_tyvars ty1 ty2
931 = uTysX ty1 ty2 (\(_,s) -> Just s) (tmpl_tyvars, emptySubstEnv)
933 unifyExtendTysX :: TyVarSet -- Template tyvars
934 -> TyVarSubstEnv -- Substitution to start with
937 -> Maybe TyVarSubstEnv -- Extended substitution
938 unifyExtendTysX tmpl_tyvars subst ty1 ty2
939 = uTysX ty1 ty2 (\(_,s) -> Just s) (tmpl_tyvars, subst)
941 unifyTyListsX :: TyVarSet -> [Type] -> [Type]
942 -> Maybe TyVarSubstEnv
943 unifyTyListsX tmpl_tyvars tys1 tys2
944 = uTyListsX tys1 tys2 (\(_,s) -> Just s) (tmpl_tyvars, emptySubstEnv)
949 -> (MySubst -> Maybe result)
953 uTysX (NoteTy _ ty1) ty2 k subst = uTysX ty1 ty2 k subst
954 uTysX ty1 (NoteTy _ ty2) k subst = uTysX ty1 ty2 k subst
956 -- Variables; go for uVar
957 uTysX (TyVarTy tyvar1) (TyVarTy tyvar2) k subst
960 uTysX (TyVarTy tyvar1) ty2 k subst@(tmpls,_)
961 | tyvar1 `elemVarSet` tmpls
962 = uVarX tyvar1 ty2 k subst
963 uTysX ty1 (TyVarTy tyvar2) k subst@(tmpls,_)
964 | tyvar2 `elemVarSet` tmpls
965 = uVarX tyvar2 ty1 k subst
968 uTysX (SourceTy (IParam n1 t1)) (SourceTy (IParam n2 t2)) k subst
969 | n1 == n2 = uTysX t1 t2 k subst
970 uTysX (SourceTy (ClassP c1 tys1)) (SourceTy (ClassP c2 tys2)) k subst
971 | c1 == c2 = uTyListsX tys1 tys2 k subst
972 uTysX (SourceTy (NType tc1 tys1)) (SourceTy (NType tc2 tys2)) k subst
973 | tc1 == tc2 = uTyListsX tys1 tys2 k subst
975 -- Functions; just check the two parts
976 uTysX (FunTy fun1 arg1) (FunTy fun2 arg2) k subst
977 = uTysX fun1 fun2 (uTysX arg1 arg2 k) subst
979 -- Type constructors must match
980 uTysX (TyConApp con1 tys1) (TyConApp con2 tys2) k subst
981 | (con1 == con2 && equalLength tys1 tys2)
982 = uTyListsX tys1 tys2 k subst
984 -- Applications need a bit of care!
985 -- They can match FunTy and TyConApp, so use splitAppTy_maybe
986 -- NB: we've already dealt with type variables and Notes,
987 -- so if one type is an App the other one jolly well better be too
988 uTysX (AppTy s1 t1) ty2 k subst
989 = case tcSplitAppTy_maybe ty2 of
990 Just (s2, t2) -> uTysX s1 s2 (uTysX t1 t2 k) subst
991 Nothing -> Nothing -- Fail
993 uTysX ty1 (AppTy s2 t2) k subst
994 = case tcSplitAppTy_maybe ty1 of
995 Just (s1, t1) -> uTysX s1 s2 (uTysX t1 t2 k) subst
996 Nothing -> Nothing -- Fail
998 -- Not expecting for-alls in unification
1000 uTysX (ForAllTy _ _) ty2 k subst = panic "Unify.uTysX subst:ForAllTy (1st arg)"
1001 uTysX ty1 (ForAllTy _ _) k subst = panic "Unify.uTysX subst:ForAllTy (2nd arg)"
1004 -- Anything else fails
1005 uTysX ty1 ty2 k subst = Nothing
1008 uTyListsX [] [] k subst = k subst
1009 uTyListsX (ty1:tys1) (ty2:tys2) k subst = uTysX ty1 ty2 (uTyListsX tys1 tys2 k) subst
1010 uTyListsX tys1 tys2 k subst = Nothing -- Fail if the lists are different lengths
1014 -- Invariant: tv1 is a unifiable variable
1015 uVarX tv1 ty2 k subst@(tmpls, env)
1016 = case lookupSubstEnv env tv1 of
1017 Just (DoneTy ty1) -> -- Already bound
1018 uTysX ty1 ty2 k subst
1020 Nothing -- Not already bound
1021 | typeKind ty2 `eqKind` tyVarKind tv1
1022 && occur_check_ok ty2
1023 -> -- No kind mismatch nor occur check
1024 k (tmpls, extendSubstEnv env tv1 (DoneTy ty2))
1026 | otherwise -> Nothing -- Fail if kind mis-match or occur check
1028 occur_check_ok ty = all occur_check_ok_tv (varSetElems (tyVarsOfType ty))
1029 occur_check_ok_tv tv | tv1 == tv = False
1030 | otherwise = case lookupSubstEnv env tv of
1032 Just (DoneTy ty) -> occur_check_ok ty
1037 %************************************************************************
1039 \subsection{Matching on types}
1041 %************************************************************************
1043 Matching is a {\em unidirectional} process, matching a type against a
1044 template (which is just a type with type variables in it). The
1045 matcher assumes that there are no repeated type variables in the
1046 template, so that it simply returns a mapping of type variables to
1047 types. It also fails on nested foralls.
1049 @matchTys@ matches corresponding elements of a list of templates and
1050 types. It and @matchTy@ both ignore usage annotations, unlike the
1051 main function @match@.
1054 matchTy :: TyVarSet -- Template tyvars
1056 -> Type -- Proposed instance of template
1057 -> Maybe TyVarSubstEnv -- Matching substitution
1060 matchTys :: TyVarSet -- Template tyvars
1061 -> [Type] -- Templates
1062 -> [Type] -- Proposed instance of template
1063 -> Maybe (TyVarSubstEnv, -- Matching substitution
1064 [Type]) -- Left over instance types
1066 matchTy tmpls ty1 ty2 = match ty1 ty2 tmpls (\ senv -> Just senv) emptySubstEnv
1068 matchTys tmpls tys1 tys2 = match_list tys1 tys2 tmpls
1069 (\ (senv,tys) -> Just (senv,tys))
1073 @match@ is the main function. It takes a flag indicating whether
1074 usage annotations are to be respected.
1077 match :: Type -> Type -- Current match pair
1078 -> TyVarSet -- Template vars
1079 -> (TyVarSubstEnv -> Maybe result) -- Continuation
1080 -> TyVarSubstEnv -- Current subst
1083 -- When matching against a type variable, see if the variable
1084 -- has already been bound. If so, check that what it's bound to
1085 -- is the same as ty; if not, bind it and carry on.
1087 match (TyVarTy v) ty tmpls k senv
1088 | v `elemVarSet` tmpls
1089 = -- v is a template variable
1090 case lookupSubstEnv senv v of
1091 Nothing | typeKind ty `eqKind` tyVarKind v
1092 -- We do a kind check, just as in the uVarX above
1093 -- The kind check is needed to avoid bogus matches
1094 -- of (a b) with (c d), where the kinds don't match
1095 -- An occur check isn't needed when matching.
1096 -> k (extendSubstEnv senv v (DoneTy ty))
1098 | otherwise -> Nothing -- Fails
1100 Just (DoneTy ty') | ty' `tcEqType` ty -> k senv -- Succeeds
1101 | otherwise -> Nothing -- Fails
1104 = -- v is not a template variable; ty had better match
1105 -- Can't use (==) because types differ
1106 case tcGetTyVar_maybe ty of
1107 Just v' | v == v' -> k senv -- Success
1108 other -> Nothing -- Failure
1109 -- This tcGetTyVar_maybe is *required* because it must strip Notes.
1110 -- I guess the reason the Note-stripping case is *last* rather than first
1111 -- is to preserve type synonyms etc., so I'm not moving it to the
1112 -- top; but this means that (without the deNotetype) a type
1113 -- variable may not match the pattern (TyVarTy v') as one would
1114 -- expect, due to an intervening Note. KSW 2000-06.
1117 match (SourceTy (IParam n1 t1)) (SourceTy (IParam n2 t2)) tmpls k senv
1118 | n1 == n2 = match t1 t2 tmpls k senv
1119 match (SourceTy (ClassP c1 tys1)) (SourceTy (ClassP c2 tys2)) tmpls k senv
1120 | c1 == c2 = match_list_exactly tys1 tys2 tmpls k senv
1121 match (SourceTy (NType tc1 tys1)) (SourceTy (NType tc2 tys2)) tmpls k senv
1122 | tc1 == tc2 = match_list_exactly tys1 tys2 tmpls k senv
1124 -- Functions; just check the two parts
1125 match (FunTy arg1 res1) (FunTy arg2 res2) tmpls k senv
1126 = match arg1 arg2 tmpls (match res1 res2 tmpls k) senv
1128 match (AppTy fun1 arg1) ty2 tmpls k senv
1129 = case tcSplitAppTy_maybe ty2 of
1130 Just (fun2,arg2) -> match fun1 fun2 tmpls (match arg1 arg2 tmpls k) senv
1131 Nothing -> Nothing -- Fail
1133 match (TyConApp tc1 tys1) (TyConApp tc2 tys2) tmpls k senv
1134 | tc1 == tc2 = match_list_exactly tys1 tys2 tmpls k senv
1136 -- Newtypes are opaque; other source types should not happen
1137 match (SourceTy (NType tc1 tys1)) (SourceTy (NType tc2 tys2)) tmpls k senv
1138 | tc1 == tc2 = match_list_exactly tys1 tys2 tmpls k senv
1140 -- With type synonyms, we have to be careful for the exact
1141 -- same reasons as in the unifier. Please see the
1142 -- considerable commentary there before changing anything
1143 -- here! (WDP 95/05)
1144 match (NoteTy n1 ty1) ty2 tmpls k senv = match ty1 ty2 tmpls k senv
1145 match ty1 (NoteTy n2 ty2) tmpls k senv = match ty1 ty2 tmpls k senv
1148 match _ _ _ _ _ = Nothing
1150 match_list_exactly tys1 tys2 tmpls k senv
1151 = match_list tys1 tys2 tmpls k' senv
1153 k' (senv', tys2') | null tys2' = k senv' -- Succeed
1154 | otherwise = Nothing -- Fail
1156 match_list [] tys2 tmpls k senv = k (senv, tys2)
1157 match_list (ty1:tys1) [] tmpls k senv = Nothing -- Not enough arg tys => failure
1158 match_list (ty1:tys1) (ty2:tys2) tmpls k senv
1159 = match ty1 ty2 tmpls (match_list tys1 tys2 tmpls k) senv