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,
48 isTauTy, tcIsTyVarTy, tcIsForAllTy,
51 ---------------------------------
52 -- Misc type manipulators
53 deNoteType, classNamesOfTheta,
54 tyClsNamesOfType, tyClsNamesOfDFunHead,
57 ---------------------------------
59 getClassPredTys_maybe, getClassPredTys,
60 isPredTy, isClassPred, isTyVarClassPred, predHasFDs,
61 mkDictTy, tcSplitPredTy_maybe,
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
95 isPrimitiveType, isTyVarTy,
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 )
108 -- PprType imports TcType so that it can print intelligently
111 import TypeRep ( Type(..), TyNote(..), funTyCon ) -- friend
113 import Type ( -- Re-exports
114 tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tyVarsOfTheta,
115 Kind, Type, SourceType(..), PredType, ThetaType,
116 unliftedTypeKind, liftedTypeKind, openTypeKind, mkArrowKind, mkArrowKinds,
117 mkForAllTy, mkForAllTys, defaultKind, isTypeKind, isAnyTypeKind,
118 mkFunTy, mkFunTys, zipFunTys, isTyVarTy,
119 mkTyConApp, mkGenTyConApp, mkAppTy, mkAppTys, mkSynTy, applyTy, applyTys,
120 mkTyVarTy, mkTyVarTys, mkTyConTy, mkPredTy, mkPredTys,
121 isUnLiftedType, isUnboxedTupleType, isPrimitiveType,
122 splitNewType_maybe, splitTyConApp_maybe,
123 tidyTopType, tidyType, tidyPred, tidyTypes, tidyFreeTyVars, tidyOpenType, tidyOpenTypes,
124 tidyTyVarBndr, tidyOpenTyVar, tidyOpenTyVars, eqKind, eqUsage,
125 hasMoreBoxityInfo, liftedBoxity, superBoxity, typeKind, superKind
127 import TyCon ( TyCon, isUnLiftedTyCon )
128 import Class ( classHasFDs, Class )
129 import Var ( TyVar, tyVarKind, isMutTyVar, mutTyVarDetails )
130 import ForeignCall ( Safety, playSafe )
135 import CmdLineOpts ( DynFlags, DynFlag( Opt_GlasgowExts ), dopt )
136 import Name ( Name, NamedThing(..), mkInternalName, getSrcLoc )
137 import OccName ( OccName, mkDictOcc )
139 import PrelNames -- Lots (e.g. in isFFIArgumentTy)
140 import TysWiredIn ( ptrTyCon, funPtrTyCon, addrTyCon, unitTyCon )
141 import BasicTypes ( IPName(..), ipNameName )
142 import Unique ( Unique, Uniquable(..) )
143 import SrcLoc ( SrcLoc )
144 import Util ( cmpList, thenCmp, equalLength )
145 import Maybes ( maybeToBool, expectJust )
150 %************************************************************************
154 %************************************************************************
156 The type checker divides the generic Type world into the
157 following more structured beasts:
159 sigma ::= forall tyvars. phi
160 -- A sigma type is a qualified type
162 -- Note that even if 'tyvars' is empty, theta
163 -- may not be: e.g. (?x::Int) => Int
165 -- Note that 'sigma' is in prenex form:
166 -- all the foralls are at the front.
167 -- A 'phi' type has no foralls to the right of
175 -- A 'tau' type has no quantification anywhere
176 -- Note that the args of a type constructor must be taus
178 | tycon tau_1 .. tau_n
182 -- In all cases, a (saturated) type synonym application is legal,
183 -- provided it expands to the required form.
187 type SigmaType = Type
193 type TcTyVar = TyVar -- Might be a mutable tyvar
194 type TcTyVarSet = TyVarSet
196 type TcType = Type -- A TcType can have mutable type variables
197 -- Invariant on ForAllTy in TcTypes:
199 -- a cannot occur inside a MutTyVar in T; that is,
200 -- T is "flattened" before quantifying over a
202 type TcPredType = PredType
203 type TcThetaType = ThetaType
204 type TcSigmaType = TcType
205 type TcRhoType = TcType
206 type TcTauType = TcType
211 %************************************************************************
213 \subsection{TyVarDetails}
215 %************************************************************************
217 TyVarDetails gives extra info about type variables, used during type
218 checking. It's attached to mutable type variables only.
219 It's knot-tied back to Var.lhs. There is no reason in principle
220 why Var.lhs shouldn't actually have the definition, but it "belongs" here.
224 = HoleTv -- Used *only* by the type checker when passing in a type
225 -- variable that should be side-effected to the result type.
226 -- Always has kind openTypeKind.
227 -- Never appears in types
229 | SigTv -- Introduced when instantiating a type signature,
230 -- prior to checking that the defn of a fn does
231 -- have the expected type. Should not be instantiated.
233 -- f :: forall a. a -> a
235 -- When checking e, with expected type (a->a), we
236 -- should not instantiate a
238 | ClsTv -- Scoped type variable introduced by a class decl
239 -- class C a where ...
241 | InstTv -- Ditto, but instance decl
243 | PatSigTv -- Scoped type variable, introduced by a pattern
247 | VanillaTv -- Everything else
249 isUserTyVar :: TcTyVar -> Bool -- Avoid unifying these if possible
250 isUserTyVar tv = case mutTyVarDetails tv of
254 isSkolemTyVar :: TcTyVar -> Bool
255 isSkolemTyVar tv = case mutTyVarDetails tv of
261 isHoleTyVar :: TcTyVar -> Bool
262 -- NB: the hole might be filled in by now, and this
263 -- function does not check for that
264 isHoleTyVar tv = ASSERT( isMutTyVar tv )
265 case mutTyVarDetails tv of
269 tyVarBindingInfo :: TyVar -> SDoc -- Used in checkSigTyVars
272 = sep [ptext SLIT("is bound by the") <+> details (mutTyVarDetails tv),
273 ptext SLIT("at") <+> ppr (getSrcLoc tv)]
277 details SigTv = ptext SLIT("type signature")
278 details ClsTv = ptext SLIT("class declaration")
279 details InstTv = ptext SLIT("instance declaration")
280 details PatSigTv = ptext SLIT("pattern type signature")
281 details HoleTv = ptext SLIT("//hole//") -- Should not happen
282 details VanillaTv = ptext SLIT("//vanilla//") -- Ditto
286 %************************************************************************
288 \subsection{Tau, sigma and rho}
290 %************************************************************************
293 mkSigmaTy tyvars theta tau = mkForAllTys tyvars (mkPhiTy theta tau)
295 mkPhiTy :: [SourceType] -> Type -> Type
296 mkPhiTy theta ty = foldr (\p r -> FunTy (mkPredTy p) r) ty theta
300 @isTauTy@ tests for nested for-alls.
303 isTauTy :: Type -> Bool
304 isTauTy (TyVarTy v) = True
305 isTauTy (TyConApp _ tys) = all isTauTy tys
306 isTauTy (AppTy a b) = isTauTy a && isTauTy b
307 isTauTy (FunTy a b) = isTauTy a && isTauTy b
308 isTauTy (SourceTy p) = True -- Don't look through source types
309 isTauTy (NoteTy _ ty) = isTauTy ty
310 isTauTy other = False
314 getDFunTyKey :: Type -> OccName -- Get some string from a type, to be used to
315 -- construct a dictionary function name
316 getDFunTyKey (TyVarTy tv) = getOccName tv
317 getDFunTyKey (TyConApp tc _) = getOccName tc
318 getDFunTyKey (AppTy fun _) = getDFunTyKey fun
319 getDFunTyKey (NoteTy _ t) = getDFunTyKey t
320 getDFunTyKey (FunTy arg _) = getOccName funTyCon
321 getDFunTyKey (ForAllTy _ t) = getDFunTyKey t
322 getDFunTyKey (SourceTy (NType tc _)) = getOccName tc -- Newtypes are quite reasonable
323 getDFunTyKey ty = pprPanic "getDFunTyKey" (pprType ty)
324 -- SourceTy shouldn't happen
328 %************************************************************************
330 \subsection{Expanding and splitting}
332 %************************************************************************
334 These tcSplit functions are like their non-Tc analogues, but
335 a) they do not look through newtypes
336 b) they do not look through PredTys
337 c) [future] they ignore usage-type annotations
339 However, they are non-monadic and do not follow through mutable type
340 variables. It's up to you to make sure this doesn't matter.
343 tcSplitForAllTys :: Type -> ([TyVar], Type)
344 tcSplitForAllTys ty = split ty ty []
346 split orig_ty (ForAllTy tv ty) tvs = split ty ty (tv:tvs)
347 split orig_ty (NoteTy n ty) tvs = split orig_ty ty tvs
348 split orig_ty t tvs = (reverse tvs, orig_ty)
350 tcIsForAllTy (ForAllTy tv ty) = True
351 tcIsForAllTy (NoteTy n ty) = tcIsForAllTy ty
352 tcIsForAllTy t = False
354 tcSplitPhiTy :: Type -> ([PredType], Type)
355 tcSplitPhiTy ty = split ty ty []
357 split orig_ty (FunTy arg res) ts = case tcSplitPredTy_maybe arg of
358 Just p -> split res res (p:ts)
359 Nothing -> (reverse ts, orig_ty)
360 split orig_ty (NoteTy n ty) ts = split orig_ty ty ts
361 split orig_ty ty ts = (reverse ts, orig_ty)
363 tcSplitSigmaTy ty = case tcSplitForAllTys ty of
364 (tvs, rho) -> case tcSplitPhiTy rho of
365 (theta, tau) -> (tvs, theta, tau)
367 tcTyConAppTyCon :: Type -> TyCon
368 tcTyConAppTyCon ty = fst (tcSplitTyConApp ty)
370 tcTyConAppArgs :: Type -> [Type]
371 tcTyConAppArgs ty = snd (tcSplitTyConApp ty)
373 tcSplitTyConApp :: Type -> (TyCon, [Type])
374 tcSplitTyConApp ty = case tcSplitTyConApp_maybe ty of
376 Nothing -> pprPanic "tcSplitTyConApp" (pprType ty)
378 tcSplitTyConApp_maybe :: Type -> Maybe (TyCon, [Type])
379 tcSplitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
380 tcSplitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res])
381 tcSplitTyConApp_maybe (NoteTy n ty) = tcSplitTyConApp_maybe ty
382 tcSplitTyConApp_maybe (SourceTy (NType tc tys)) = Just (tc,tys)
383 -- Newtypes are opaque, so they may be split
384 -- However, predicates are not treated
385 -- as tycon applications by the type checker
386 tcSplitTyConApp_maybe other = Nothing
388 tcSplitFunTys :: Type -> ([Type], Type)
389 tcSplitFunTys ty = case tcSplitFunTy_maybe ty of
391 Just (arg,res) -> (arg:args, res')
393 (args,res') = tcSplitFunTys res
395 tcSplitFunTy_maybe :: Type -> Maybe (Type, Type)
396 tcSplitFunTy_maybe (FunTy arg res) = Just (arg, res)
397 tcSplitFunTy_maybe (NoteTy n ty) = tcSplitFunTy_maybe ty
398 tcSplitFunTy_maybe other = Nothing
400 tcFunArgTy ty = case tcSplitFunTy_maybe ty of { Just (arg,res) -> arg }
401 tcFunResultTy ty = case tcSplitFunTy_maybe ty of { Just (arg,res) -> res }
404 tcSplitAppTy_maybe :: Type -> Maybe (Type, Type)
405 tcSplitAppTy_maybe (FunTy ty1 ty2) = Just (TyConApp funTyCon [ty1], ty2)
406 tcSplitAppTy_maybe (AppTy ty1 ty2) = Just (ty1, ty2)
407 tcSplitAppTy_maybe (NoteTy n ty) = tcSplitAppTy_maybe ty
408 tcSplitAppTy_maybe (SourceTy (NType tc tys)) = tc_split_app tc tys
409 --- Don't forget that newtype!
410 tcSplitAppTy_maybe (TyConApp tc tys) = tc_split_app tc tys
411 tcSplitAppTy_maybe other = Nothing
413 tc_split_app tc [] = Nothing
414 tc_split_app tc tys = split tys []
416 split [ty2] acc = Just (TyConApp tc (reverse acc), ty2)
417 split (ty:tys) acc = split tys (ty:acc)
419 tcSplitAppTy ty = case tcSplitAppTy_maybe ty of
421 Nothing -> pprPanic "tcSplitAppTy" (pprType ty)
423 tcGetTyVar_maybe :: Type -> Maybe TyVar
424 tcGetTyVar_maybe (TyVarTy tv) = Just tv
425 tcGetTyVar_maybe (NoteTy _ t) = tcGetTyVar_maybe t
426 tcGetTyVar_maybe other = Nothing
428 tcGetTyVar :: String -> Type -> TyVar
429 tcGetTyVar msg ty = expectJust msg (tcGetTyVar_maybe ty)
431 tcIsTyVarTy :: Type -> Bool
432 tcIsTyVarTy ty = maybeToBool (tcGetTyVar_maybe ty)
435 The type of a method for class C is always of the form:
436 Forall a1..an. C a1..an => sig_ty
437 where sig_ty is the type given by the method's signature, and thus in general
438 is a ForallTy. At the point that splitMethodTy is called, it is expected
439 that the outer Forall has already been stripped off. splitMethodTy then
440 returns (C a1..an, sig_ty') where sig_ty' is sig_ty with any Notes or
444 tcSplitMethodTy :: Type -> (PredType, Type)
445 tcSplitMethodTy ty = split ty
447 split (FunTy arg res) = case tcSplitPredTy_maybe arg of
449 Nothing -> panic "splitMethodTy"
450 split (NoteTy n ty) = split ty
451 split _ = panic "splitMethodTy"
453 tcSplitDFunTy :: Type -> ([TyVar], [SourceType], Class, [Type])
454 -- Split the type of a dictionary function
456 = case tcSplitSigmaTy ty of { (tvs, theta, tau) ->
457 case tcSplitPredTy_maybe tau of { Just (ClassP clas tys) ->
458 (tvs, theta, clas, tys) }}
461 (allDistinctTyVars tys tvs) = True
463 all the types tys are type variables,
464 distinct from each other and from tvs.
466 This is useful when checking that unification hasn't unified signature
467 type variables. For example, if the type sig is
468 f :: forall a b. a -> b -> b
469 we want to check that 'a' and 'b' havn't
470 (a) been unified with a non-tyvar type
471 (b) been unified with each other (all distinct)
472 (c) been unified with a variable free in the environment
475 allDistinctTyVars :: [Type] -> TyVarSet -> Bool
477 allDistinctTyVars [] acc
479 allDistinctTyVars (ty:tys) acc
480 = case tcGetTyVar_maybe ty of
481 Nothing -> False -- (a)
482 Just tv | tv `elemVarSet` acc -> False -- (b) or (c)
483 | otherwise -> allDistinctTyVars tys (acc `extendVarSet` tv)
487 %************************************************************************
489 \subsection{Predicate types}
491 %************************************************************************
493 "Predicates" are particular source types, namelyClassP or IParams
496 isPred :: SourceType -> Bool
497 isPred (ClassP _ _) = True
498 isPred (IParam _ _) = True
499 isPred (NType _ _) = False
501 isPredTy :: Type -> Bool
502 isPredTy (NoteTy _ ty) = isPredTy ty
503 isPredTy (SourceTy sty) = isPred sty
506 tcSplitPredTy_maybe :: Type -> Maybe PredType
507 -- Returns Just for predicates only
508 tcSplitPredTy_maybe (NoteTy _ ty) = tcSplitPredTy_maybe ty
509 tcSplitPredTy_maybe (SourceTy p) | isPred p = Just p
510 tcSplitPredTy_maybe other = Nothing
512 predTyUnique :: PredType -> Unique
513 predTyUnique (IParam n _) = getUnique (ipNameName n)
514 predTyUnique (ClassP clas tys) = getUnique clas
516 predHasFDs :: PredType -> Bool
517 -- True if the predicate has functional depenencies;
518 -- I.e. should participate in improvement
519 predHasFDs (IParam _ _) = True
520 predHasFDs (ClassP cls _) = classHasFDs cls
522 mkPredName :: Unique -> SrcLoc -> SourceType -> Name
523 mkPredName uniq loc (ClassP cls tys) = mkInternalName uniq (mkDictOcc (getOccName cls)) loc
524 mkPredName uniq loc (IParam ip ty) = mkInternalName uniq (getOccName (ipNameName ip)) loc
528 --------------------- Dictionary types ---------------------------------
531 mkClassPred clas tys = ClassP clas tys
533 isClassPred :: SourceType -> Bool
534 isClassPred (ClassP clas tys) = True
535 isClassPred other = False
537 isTyVarClassPred (ClassP clas tys) = all tcIsTyVarTy tys
538 isTyVarClassPred other = False
540 getClassPredTys_maybe :: SourceType -> Maybe (Class, [Type])
541 getClassPredTys_maybe (ClassP clas tys) = Just (clas, tys)
542 getClassPredTys_maybe _ = Nothing
544 getClassPredTys :: PredType -> (Class, [Type])
545 getClassPredTys (ClassP clas tys) = (clas, tys)
547 mkDictTy :: Class -> [Type] -> Type
548 mkDictTy clas tys = mkPredTy (ClassP clas tys)
550 isDictTy :: Type -> Bool
551 isDictTy (SourceTy p) = isClassPred p
552 isDictTy (NoteTy _ ty) = isDictTy ty
553 isDictTy other = False
556 --------------------- Implicit parameters ---------------------------------
559 isIPPred :: SourceType -> Bool
560 isIPPred (IParam _ _) = True
561 isIPPred other = False
563 isInheritablePred :: PredType -> Bool
564 -- Can be inherited by a context. For example, consider
565 -- f x = let g y = (?v, y+x)
566 -- in (g 3 with ?v = 8,
568 -- The point is that g's type must be quantifed over ?v:
569 -- g :: (?v :: a) => a -> a
570 -- but it doesn't need to be quantified over the Num a dictionary
571 -- which can be free in g's rhs, and shared by both calls to g
572 isInheritablePred (ClassP _ _) = True
573 isInheritablePred other = False
575 isLinearPred :: TcPredType -> Bool
576 isLinearPred (IParam (Linear n) _) = True
577 isLinearPred other = False
581 %************************************************************************
583 \subsection{Comparison}
585 %************************************************************************
587 Comparison, taking note of newtypes, predicates, etc,
588 But ignoring usage types
591 tcEqType :: Type -> Type -> Bool
592 tcEqType ty1 ty2 = case ty1 `tcCmpType` ty2 of { EQ -> True; other -> False }
594 tcEqTypes :: [Type] -> [Type] -> Bool
595 tcEqTypes ty1 ty2 = case ty1 `tcCmpTypes` ty2 of { EQ -> True; other -> False }
597 tcEqPred :: PredType -> PredType -> Bool
598 tcEqPred p1 p2 = case p1 `tcCmpPred` p2 of { EQ -> True; other -> False }
601 tcCmpType :: Type -> Type -> Ordering
602 tcCmpType ty1 ty2 = cmpTy emptyVarEnv ty1 ty2
604 tcCmpTypes tys1 tys2 = cmpTys emptyVarEnv tys1 tys2
606 tcCmpPred p1 p2 = cmpSourceTy emptyVarEnv p1 p2
608 cmpTys env tys1 tys2 = cmpList (cmpTy env) tys1 tys2
611 cmpTy :: TyVarEnv TyVar -> Type -> Type -> Ordering
612 -- The "env" maps type variables in ty1 to type variables in ty2
613 -- So when comparing for-alls.. (forall tv1 . t1) (forall tv2 . t2)
614 -- we in effect substitute tv2 for tv1 in t1 before continuing
616 -- Look through NoteTy
617 cmpTy env (NoteTy _ ty1) ty2 = cmpTy env ty1 ty2
618 cmpTy env ty1 (NoteTy _ ty2) = cmpTy env ty1 ty2
620 -- Deal with equal constructors
621 cmpTy env (TyVarTy tv1) (TyVarTy tv2) = case lookupVarEnv env tv1 of
622 Just tv1a -> tv1a `compare` tv2
623 Nothing -> tv1 `compare` tv2
625 cmpTy env (SourceTy p1) (SourceTy p2) = cmpSourceTy env p1 p2
626 cmpTy env (AppTy f1 a1) (AppTy f2 a2) = cmpTy env f1 f2 `thenCmp` cmpTy env a1 a2
627 cmpTy env (FunTy f1 a1) (FunTy f2 a2) = cmpTy env f1 f2 `thenCmp` cmpTy env a1 a2
628 cmpTy env (TyConApp tc1 tys1) (TyConApp tc2 tys2) = (tc1 `compare` tc2) `thenCmp` (cmpTys env tys1 tys2)
629 cmpTy env (ForAllTy tv1 t1) (ForAllTy tv2 t2) = cmpTy (extendVarEnv env tv1 tv2) t1 t2
631 -- Deal with the rest: TyVarTy < AppTy < FunTy < TyConApp < ForAllTy < SourceTy
632 cmpTy env (AppTy _ _) (TyVarTy _) = GT
634 cmpTy env (FunTy _ _) (TyVarTy _) = GT
635 cmpTy env (FunTy _ _) (AppTy _ _) = GT
637 cmpTy env (TyConApp _ _) (TyVarTy _) = GT
638 cmpTy env (TyConApp _ _) (AppTy _ _) = GT
639 cmpTy env (TyConApp _ _) (FunTy _ _) = GT
641 cmpTy env (ForAllTy _ _) (TyVarTy _) = GT
642 cmpTy env (ForAllTy _ _) (AppTy _ _) = GT
643 cmpTy env (ForAllTy _ _) (FunTy _ _) = GT
644 cmpTy env (ForAllTy _ _) (TyConApp _ _) = GT
646 cmpTy env (SourceTy _) t2 = GT
652 cmpSourceTy :: TyVarEnv TyVar -> SourceType -> SourceType -> Ordering
653 cmpSourceTy env (IParam n1 ty1) (IParam n2 ty2) = (n1 `compare` n2) `thenCmp` (cmpTy env ty1 ty2)
654 -- Compare types as well as names for implicit parameters
655 -- This comparison is used exclusively (I think) for the
656 -- finite map built in TcSimplify
657 cmpSourceTy env (IParam _ _) sty = LT
659 cmpSourceTy env (ClassP _ _) (IParam _ _) = GT
660 cmpSourceTy env (ClassP c1 tys1) (ClassP c2 tys2) = (c1 `compare` c2) `thenCmp` (cmpTys env tys1 tys2)
661 cmpSourceTy env (ClassP _ _) (NType _ _) = LT
663 cmpSourceTy env (NType tc1 tys1) (NType tc2 tys2) = (tc1 `compare` tc2) `thenCmp` (cmpTys env tys1 tys2)
664 cmpSourceTy env (NType _ _) sty = GT
667 PredTypes are used as a FM key in TcSimplify,
668 so we take the easy path and make them an instance of Ord
671 instance Eq SourceType where { (==) = tcEqPred }
672 instance Ord SourceType where { compare = tcCmpPred }
676 %************************************************************************
678 \subsection{Predicates}
680 %************************************************************************
682 isSigmaTy returns true of any qualified type. It doesn't *necessarily* have
684 f :: (?x::Int) => Int -> Int
687 isSigmaTy :: Type -> Bool
688 isSigmaTy (ForAllTy tyvar ty) = True
689 isSigmaTy (FunTy a b) = isPredTy a
690 isSigmaTy (NoteTy n ty) = isSigmaTy ty
693 isOverloadedTy :: Type -> Bool
694 isOverloadedTy (ForAllTy tyvar ty) = isOverloadedTy ty
695 isOverloadedTy (FunTy a b) = isPredTy a
696 isOverloadedTy (NoteTy n ty) = isOverloadedTy ty
697 isOverloadedTy _ = False
701 isFloatTy = is_tc floatTyConKey
702 isDoubleTy = is_tc doubleTyConKey
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 deNoteType :: Type -> Type
725 -- Remove synonyms, but not source types
726 deNoteType ty@(TyVarTy tyvar) = ty
727 deNoteType (TyConApp tycon tys) = TyConApp tycon (map deNoteType tys)
728 deNoteType (SourceTy p) = SourceTy (deNoteSourceType p)
729 deNoteType (NoteTy _ ty) = deNoteType ty
730 deNoteType (AppTy fun arg) = AppTy (deNoteType fun) (deNoteType arg)
731 deNoteType (FunTy fun arg) = FunTy (deNoteType fun) (deNoteType arg)
732 deNoteType (ForAllTy tv ty) = ForAllTy tv (deNoteType ty)
734 deNoteSourceType :: SourceType -> SourceType
735 deNoteSourceType (ClassP c tys) = ClassP c (map deNoteType tys)
736 deNoteSourceType (IParam n ty) = IParam n (deNoteType ty)
737 deNoteSourceType (NType tc tys) = NType tc (map deNoteType tys)
740 Find the free tycons and classes of a type. This is used in the front
744 tyClsNamesOfType :: Type -> NameSet
745 tyClsNamesOfType (TyVarTy tv) = emptyNameSet
746 tyClsNamesOfType (TyConApp tycon tys) = unitNameSet (getName tycon) `unionNameSets` tyClsNamesOfTypes tys
747 tyClsNamesOfType (NoteTy (SynNote ty1) ty2) = tyClsNamesOfType ty1
748 tyClsNamesOfType (NoteTy other_note ty2) = tyClsNamesOfType ty2
749 tyClsNamesOfType (SourceTy (IParam n ty)) = tyClsNamesOfType ty
750 tyClsNamesOfType (SourceTy (ClassP cl tys)) = unitNameSet (getName cl) `unionNameSets` tyClsNamesOfTypes tys
751 tyClsNamesOfType (SourceTy (NType tc tys)) = unitNameSet (getName tc) `unionNameSets` tyClsNamesOfTypes tys
752 tyClsNamesOfType (FunTy arg res) = tyClsNamesOfType arg `unionNameSets` tyClsNamesOfType res
753 tyClsNamesOfType (AppTy fun arg) = tyClsNamesOfType fun `unionNameSets` tyClsNamesOfType arg
754 tyClsNamesOfType (ForAllTy tyvar ty) = tyClsNamesOfType ty
756 tyClsNamesOfTypes tys = foldr (unionNameSets . tyClsNamesOfType) emptyNameSet tys
758 tyClsNamesOfDFunHead :: Type -> NameSet
759 -- Find the free type constructors and classes
760 -- of the head of the dfun instance type
761 -- The 'dfun_head_type' is because of
762 -- instance Foo a => Baz T where ...
763 -- The decl is an orphan if Baz and T are both not locally defined,
764 -- even if Foo *is* locally defined
765 tyClsNamesOfDFunHead dfun_ty
766 = case tcSplitSigmaTy dfun_ty of
767 (tvs,_,head_ty) -> tyClsNamesOfType head_ty
769 classNamesOfTheta :: ThetaType -> [Name]
770 -- Looks just for ClassP things; maybe it should check
771 classNamesOfTheta preds = [ getName c | ClassP c _ <- preds ]
775 %************************************************************************
777 \subsection[TysWiredIn-ext-type]{External types}
779 %************************************************************************
781 The compiler's foreign function interface supports the passing of a
782 restricted set of types as arguments and results (the restricting factor
786 isFFIArgumentTy :: DynFlags -> Safety -> Type -> Bool
787 -- Checks for valid argument type for a 'foreign import'
788 isFFIArgumentTy dflags safety ty
789 = checkRepTyCon (legalOutgoingTyCon dflags safety) ty
791 isFFIExternalTy :: Type -> Bool
792 -- Types that are allowed as arguments of a 'foreign export'
793 isFFIExternalTy ty = checkRepTyCon legalFEArgTyCon ty
795 isFFIImportResultTy :: DynFlags -> Type -> Bool
796 isFFIImportResultTy dflags ty
797 = checkRepTyCon (legalFIResultTyCon dflags) ty
799 isFFIExportResultTy :: Type -> Bool
800 isFFIExportResultTy ty = checkRepTyCon legalFEResultTyCon ty
802 isFFIDynArgumentTy :: Type -> Bool
803 -- The argument type of a foreign import dynamic must be Ptr, FunPtr, Addr,
804 -- or a newtype of either.
805 isFFIDynArgumentTy = checkRepTyCon (\tc -> tc == ptrTyCon || tc == funPtrTyCon || tc == addrTyCon)
807 isFFIDynResultTy :: Type -> Bool
808 -- The result type of a foreign export dynamic must be Ptr, FunPtr, Addr,
809 -- or a newtype of either.
810 isFFIDynResultTy = checkRepTyCon (\tc -> tc == ptrTyCon || tc == funPtrTyCon || tc == addrTyCon)
812 isFFILabelTy :: Type -> Bool
813 -- The type of a foreign label must be Ptr, FunPtr, Addr,
814 -- or a newtype of either.
815 isFFILabelTy = checkRepTyCon (\tc -> tc == ptrTyCon || tc == funPtrTyCon || tc == addrTyCon)
817 checkRepTyCon :: (TyCon -> Bool) -> Type -> Bool
818 -- Look through newtypes
819 -- Non-recursive ones are transparent to splitTyConApp,
820 -- but recursive ones aren't; hence the splitNewType_maybe
821 checkRepTyCon check_tc ty
822 | Just ty' <- splitNewType_maybe ty = checkRepTyCon check_tc ty'
823 | Just (tc,_) <- splitTyConApp_maybe ty = check_tc tc
827 ----------------------------------------------
828 These chaps do the work; they are not exported
829 ----------------------------------------------
832 legalFEArgTyCon :: TyCon -> Bool
833 -- It's illegal to return foreign objects and (mutable)
834 -- bytearrays from a _ccall_ / foreign declaration
835 -- (or be passed them as arguments in foreign exported functions).
837 | getUnique tc `elem` [ byteArrayTyConKey, mutableByteArrayTyConKey ]
839 -- It's also illegal to make foreign exports that take unboxed
840 -- arguments. The RTS API currently can't invoke such things. --SDM 7/2000
842 = boxedMarshalableTyCon tc
844 legalFIResultTyCon :: DynFlags -> TyCon -> Bool
845 legalFIResultTyCon dflags tc
846 | getUnique tc `elem`
847 [ byteArrayTyConKey, mutableByteArrayTyConKey ] = False
848 | tc == unitTyCon = True
849 | otherwise = marshalableTyCon dflags tc
851 legalFEResultTyCon :: TyCon -> Bool
852 legalFEResultTyCon tc
853 | getUnique tc `elem`
854 [ byteArrayTyConKey, mutableByteArrayTyConKey ] = False
855 | tc == unitTyCon = True
856 | otherwise = boxedMarshalableTyCon tc
858 legalOutgoingTyCon :: DynFlags -> Safety -> TyCon -> Bool
859 -- Checks validity of types going from Haskell -> external world
860 legalOutgoingTyCon dflags safety tc
861 | playSafe safety && getUnique tc `elem` [byteArrayTyConKey, mutableByteArrayTyConKey]
864 = marshalableTyCon dflags tc
866 marshalableTyCon dflags tc
867 = (dopt Opt_GlasgowExts dflags && isUnLiftedTyCon tc)
868 || boxedMarshalableTyCon tc
870 boxedMarshalableTyCon tc
871 = getUnique tc `elem` [ intTyConKey, int8TyConKey, int16TyConKey
872 , int32TyConKey, int64TyConKey
873 , wordTyConKey, word8TyConKey, word16TyConKey
874 , word32TyConKey, word64TyConKey
875 , floatTyConKey, doubleTyConKey
876 , addrTyConKey, ptrTyConKey, funPtrTyConKey
879 , byteArrayTyConKey, mutableByteArrayTyConKey
885 %************************************************************************
887 \subsection{Unification with an explicit substitution}
889 %************************************************************************
891 Unify types with an explicit substitution and no monad.
892 Ignore usage annotations.
896 = (TyVarSet, -- Set of template tyvars
897 TyVarSubstEnv) -- Not necessarily idempotent
899 unifyTysX :: TyVarSet -- Template tyvars
902 -> Maybe TyVarSubstEnv
903 unifyTysX tmpl_tyvars ty1 ty2
904 = uTysX ty1 ty2 (\(_,s) -> Just s) (tmpl_tyvars, emptySubstEnv)
906 unifyExtendTysX :: TyVarSet -- Template tyvars
907 -> TyVarSubstEnv -- Substitution to start with
910 -> Maybe TyVarSubstEnv -- Extended substitution
911 unifyExtendTysX tmpl_tyvars subst ty1 ty2
912 = uTysX ty1 ty2 (\(_,s) -> Just s) (tmpl_tyvars, subst)
914 unifyTyListsX :: TyVarSet -> [Type] -> [Type]
915 -> Maybe TyVarSubstEnv
916 unifyTyListsX tmpl_tyvars tys1 tys2
917 = uTyListsX tys1 tys2 (\(_,s) -> Just s) (tmpl_tyvars, emptySubstEnv)
922 -> (MySubst -> Maybe result)
926 uTysX (NoteTy _ ty1) ty2 k subst = uTysX ty1 ty2 k subst
927 uTysX ty1 (NoteTy _ ty2) k subst = uTysX ty1 ty2 k subst
929 -- Variables; go for uVar
930 uTysX (TyVarTy tyvar1) (TyVarTy tyvar2) k subst
933 uTysX (TyVarTy tyvar1) ty2 k subst@(tmpls,_)
934 | tyvar1 `elemVarSet` tmpls
935 = uVarX tyvar1 ty2 k subst
936 uTysX ty1 (TyVarTy tyvar2) k subst@(tmpls,_)
937 | tyvar2 `elemVarSet` tmpls
938 = uVarX tyvar2 ty1 k subst
941 uTysX (SourceTy (IParam n1 t1)) (SourceTy (IParam n2 t2)) k subst
942 | n1 == n2 = uTysX t1 t2 k subst
943 uTysX (SourceTy (ClassP c1 tys1)) (SourceTy (ClassP c2 tys2)) k subst
944 | c1 == c2 = uTyListsX tys1 tys2 k subst
945 uTysX (SourceTy (NType tc1 tys1)) (SourceTy (NType tc2 tys2)) k subst
946 | tc1 == tc2 = uTyListsX tys1 tys2 k subst
948 -- Functions; just check the two parts
949 uTysX (FunTy fun1 arg1) (FunTy fun2 arg2) k subst
950 = uTysX fun1 fun2 (uTysX arg1 arg2 k) subst
952 -- Type constructors must match
953 uTysX (TyConApp con1 tys1) (TyConApp con2 tys2) k subst
954 | (con1 == con2 && equalLength tys1 tys2)
955 = uTyListsX tys1 tys2 k subst
957 -- Applications need a bit of care!
958 -- They can match FunTy and TyConApp, so use splitAppTy_maybe
959 -- NB: we've already dealt with type variables and Notes,
960 -- so if one type is an App the other one jolly well better be too
961 uTysX (AppTy s1 t1) ty2 k subst
962 = case tcSplitAppTy_maybe ty2 of
963 Just (s2, t2) -> uTysX s1 s2 (uTysX t1 t2 k) subst
964 Nothing -> Nothing -- Fail
966 uTysX ty1 (AppTy s2 t2) k subst
967 = case tcSplitAppTy_maybe ty1 of
968 Just (s1, t1) -> uTysX s1 s2 (uTysX t1 t2 k) subst
969 Nothing -> Nothing -- Fail
971 -- Not expecting for-alls in unification
973 uTysX (ForAllTy _ _) ty2 k subst = panic "Unify.uTysX subst:ForAllTy (1st arg)"
974 uTysX ty1 (ForAllTy _ _) k subst = panic "Unify.uTysX subst:ForAllTy (2nd arg)"
977 -- Anything else fails
978 uTysX ty1 ty2 k subst = Nothing
981 uTyListsX [] [] k subst = k subst
982 uTyListsX (ty1:tys1) (ty2:tys2) k subst = uTysX ty1 ty2 (uTyListsX tys1 tys2 k) subst
983 uTyListsX tys1 tys2 k subst = Nothing -- Fail if the lists are different lengths
987 -- Invariant: tv1 is a unifiable variable
988 uVarX tv1 ty2 k subst@(tmpls, env)
989 = case lookupSubstEnv env tv1 of
990 Just (DoneTy ty1) -> -- Already bound
991 uTysX ty1 ty2 k subst
993 Nothing -- Not already bound
994 | typeKind ty2 `eqKind` tyVarKind tv1
995 && occur_check_ok ty2
996 -> -- No kind mismatch nor occur check
997 k (tmpls, extendSubstEnv env tv1 (DoneTy ty2))
999 | otherwise -> Nothing -- Fail if kind mis-match or occur check
1001 occur_check_ok ty = all occur_check_ok_tv (varSetElems (tyVarsOfType ty))
1002 occur_check_ok_tv tv | tv1 == tv = False
1003 | otherwise = case lookupSubstEnv env tv of
1005 Just (DoneTy ty) -> occur_check_ok ty
1010 %************************************************************************
1012 \subsection{Matching on types}
1014 %************************************************************************
1016 Matching is a {\em unidirectional} process, matching a type against a
1017 template (which is just a type with type variables in it). The
1018 matcher assumes that there are no repeated type variables in the
1019 template, so that it simply returns a mapping of type variables to
1020 types. It also fails on nested foralls.
1022 @matchTys@ matches corresponding elements of a list of templates and
1023 types. It and @matchTy@ both ignore usage annotations, unlike the
1024 main function @match@.
1027 matchTy :: TyVarSet -- Template tyvars
1029 -> Type -- Proposed instance of template
1030 -> Maybe TyVarSubstEnv -- Matching substitution
1033 matchTys :: TyVarSet -- Template tyvars
1034 -> [Type] -- Templates
1035 -> [Type] -- Proposed instance of template
1036 -> Maybe (TyVarSubstEnv, -- Matching substitution
1037 [Type]) -- Left over instance types
1039 matchTy tmpls ty1 ty2 = match ty1 ty2 tmpls (\ senv -> Just senv) emptySubstEnv
1041 matchTys tmpls tys1 tys2 = match_list tys1 tys2 tmpls
1042 (\ (senv,tys) -> Just (senv,tys))
1046 @match@ is the main function. It takes a flag indicating whether
1047 usage annotations are to be respected.
1050 match :: Type -> Type -- Current match pair
1051 -> TyVarSet -- Template vars
1052 -> (TyVarSubstEnv -> Maybe result) -- Continuation
1053 -> TyVarSubstEnv -- Current subst
1056 -- When matching against a type variable, see if the variable
1057 -- has already been bound. If so, check that what it's bound to
1058 -- is the same as ty; if not, bind it and carry on.
1060 match (TyVarTy v) ty tmpls k senv
1061 | v `elemVarSet` tmpls
1062 = -- v is a template variable
1063 case lookupSubstEnv senv v of
1064 Nothing | typeKind ty `eqKind` tyVarKind v
1065 -- We do a kind check, just as in the uVarX above
1066 -- The kind check is needed to avoid bogus matches
1067 -- of (a b) with (c d), where the kinds don't match
1068 -- An occur check isn't needed when matching.
1069 -> k (extendSubstEnv senv v (DoneTy ty))
1071 | otherwise -> Nothing -- Fails
1073 Just (DoneTy ty') | ty' `tcEqType` ty -> k senv -- Succeeds
1074 | otherwise -> Nothing -- Fails
1077 = -- v is not a template variable; ty had better match
1078 -- Can't use (==) because types differ
1079 case tcGetTyVar_maybe ty of
1080 Just v' | v == v' -> k senv -- Success
1081 other -> Nothing -- Failure
1082 -- This tcGetTyVar_maybe is *required* because it must strip Notes.
1083 -- I guess the reason the Note-stripping case is *last* rather than first
1084 -- is to preserve type synonyms etc., so I'm not moving it to the
1085 -- top; but this means that (without the deNotetype) a type
1086 -- variable may not match the pattern (TyVarTy v') as one would
1087 -- expect, due to an intervening Note. KSW 2000-06.
1090 match (SourceTy (IParam n1 t1)) (SourceTy (IParam n2 t2)) tmpls k senv
1091 | n1 == n2 = match t1 t2 tmpls k senv
1092 match (SourceTy (ClassP c1 tys1)) (SourceTy (ClassP c2 tys2)) tmpls k senv
1093 | c1 == c2 = match_list_exactly tys1 tys2 tmpls k senv
1094 match (SourceTy (NType tc1 tys1)) (SourceTy (NType tc2 tys2)) tmpls k senv
1095 | tc1 == tc2 = match_list_exactly tys1 tys2 tmpls k senv
1097 -- Functions; just check the two parts
1098 match (FunTy arg1 res1) (FunTy arg2 res2) tmpls k senv
1099 = match arg1 arg2 tmpls (match res1 res2 tmpls k) senv
1101 match (AppTy fun1 arg1) ty2 tmpls k senv
1102 = case tcSplitAppTy_maybe ty2 of
1103 Just (fun2,arg2) -> match fun1 fun2 tmpls (match arg1 arg2 tmpls k) senv
1104 Nothing -> Nothing -- Fail
1106 match (TyConApp tc1 tys1) (TyConApp tc2 tys2) tmpls k senv
1107 | tc1 == tc2 = match_list_exactly tys1 tys2 tmpls k senv
1109 -- Newtypes are opaque; other source types should not happen
1110 match (SourceTy (NType tc1 tys1)) (SourceTy (NType tc2 tys2)) tmpls k senv
1111 | tc1 == tc2 = match_list_exactly tys1 tys2 tmpls k senv
1113 -- With type synonyms, we have to be careful for the exact
1114 -- same reasons as in the unifier. Please see the
1115 -- considerable commentary there before changing anything
1116 -- here! (WDP 95/05)
1117 match (NoteTy n1 ty1) ty2 tmpls k senv = match ty1 ty2 tmpls k senv
1118 match ty1 (NoteTy n2 ty2) tmpls k senv = match ty1 ty2 tmpls k senv
1121 match _ _ _ _ _ = Nothing
1123 match_list_exactly tys1 tys2 tmpls k senv
1124 = match_list tys1 tys2 tmpls k' senv
1126 k' (senv', tys2') | null tys2' = k senv' -- Succeed
1127 | otherwise = Nothing -- Fail
1129 match_list [] tys2 tmpls k senv = k (senv, tys2)
1130 match_list (ty1:tys1) [] tmpls k senv = Nothing -- Not enough arg tys => failure
1131 match_list (ty1:tys1) (ty2:tys2) tmpls k senv
1132 = match ty1 ty2 tmpls (match_list tys1 tys2 tmpls k) senv