2 % (c) The University of Glasgow 2006
3 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
5 \section[TcType]{Types used in the typechecker}
7 This module provides the Type interface for front-end parts of the
10 * treat "source types" as opaque:
11 newtypes, and predicates are meaningful.
12 * look through usage types
14 The "tc" prefix is for "TypeChecker", because the type checker
15 is the principal client.
19 --------------------------------
21 TcType, TcSigmaType, TcRhoType, TcTauType, TcPredType, TcThetaType,
22 TcTyVar, TcTyVarSet, TcKind,
24 BoxyTyVar, BoxySigmaType, BoxyRhoType, BoxyThetaType, BoxyType,
26 --------------------------------
28 UserTypeCtxt(..), pprUserTypeCtxt,
29 TcTyVarDetails(..), BoxInfo(..), pprTcTyVarDetails,
30 MetaDetails(Flexi, Indirect), SkolemInfo(..), pprSkolTvBinding, pprSkolInfo,
31 isImmutableTyVar, isSkolemTyVar, isMetaTyVar, isBoxyTyVar,
32 isSigTyVar, isExistentialTyVar, isTyConableTyVar,
36 --------------------------------
40 --------------------------------
42 -- These are important because they do not look through newtypes
44 tcSplitForAllTys, tcSplitPhiTy,
45 tcSplitFunTy_maybe, tcSplitFunTys, tcFunArgTy, tcFunResultTy, tcSplitFunTysN,
46 tcSplitTyConApp, tcSplitTyConApp_maybe, tcTyConAppTyCon, tcTyConAppArgs,
47 tcSplitAppTy_maybe, tcSplitAppTy, tcSplitAppTys, repSplitAppTy_maybe,
48 tcValidInstHeadTy, tcGetTyVar_maybe, tcGetTyVar,
49 tcSplitSigmaTy, tcMultiSplitSigmaTy,
51 ---------------------------------
53 -- Again, newtypes are opaque
54 tcEqType, tcEqTypes, tcEqPred, tcCmpType, tcCmpTypes, tcCmpPred, tcEqTypeX,
56 isSigmaTy, isOverloadedTy, isRigidTy, isBoxyTy,
57 isDoubleTy, isFloatTy, isIntTy, isStringTy,
58 isIntegerTy, isBoolTy, isUnitTy,
59 isTauTy, isTauTyCon, tcIsTyVarTy, tcIsForAllTy,
61 ---------------------------------
62 -- Misc type manipulators
64 tyClsNamesOfType, tyClsNamesOfDFunHead,
67 ---------------------------------
69 getClassPredTys_maybe, getClassPredTys,
70 isClassPred, isTyVarClassPred, isEqPred,
71 mkDictTy, tcSplitPredTy_maybe,
72 isPredTy, isDictTy, tcSplitDFunTy, tcSplitDFunHead, predTyUnique,
73 mkClassPred, isInheritablePred, isIPPred,
74 dataConsStupidTheta, isRefineableTy, isRefineablePred,
76 ---------------------------------
77 -- Foreign import and export
78 isFFIArgumentTy, -- :: DynFlags -> Safety -> Type -> Bool
79 isFFIImportResultTy, -- :: DynFlags -> Type -> Bool
80 isFFIExportResultTy, -- :: Type -> Bool
81 isFFIExternalTy, -- :: Type -> Bool
82 isFFIDynArgumentTy, -- :: Type -> Bool
83 isFFIDynResultTy, -- :: Type -> Bool
84 isFFILabelTy, -- :: Type -> Bool
85 isFFIDotnetTy, -- :: DynFlags -> Type -> Bool
86 isFFIDotnetObjTy, -- :: Type -> Bool
87 isFFITy, -- :: Type -> Bool
88 tcSplitIOType_maybe, -- :: Type -> Maybe Type
89 toDNType, -- :: Type -> DNType
91 --------------------------------
92 -- Rexported from Type
93 Kind, -- Stuff to do with kinds is insensitive to pre/post Tc
94 unliftedTypeKind, liftedTypeKind, argTypeKind,
95 openTypeKind, mkArrowKind, mkArrowKinds,
96 isLiftedTypeKind, isUnliftedTypeKind, isSubOpenTypeKind,
97 isSubArgTypeKind, isSubKind, defaultKind,
98 kindVarRef, mkKindVar,
100 Type, PredType(..), ThetaType,
101 mkForAllTy, mkForAllTys,
102 mkFunTy, mkFunTys, zipFunTys,
103 mkTyConApp, mkAppTy, mkAppTys, applyTy, applyTys,
104 mkTyVarTy, mkTyVarTys, mkTyConTy, mkPredTy, mkPredTys,
106 -- Type substitutions
107 TvSubst(..), -- Representation visible to a few friends
108 TvSubstEnv, emptyTvSubst, substEqSpec,
109 mkOpenTvSubst, zipOpenTvSubst, zipTopTvSubst, mkTopTvSubst, notElemTvSubst,
110 getTvSubstEnv, setTvSubstEnv, getTvInScope, extendTvInScope, lookupTyVar,
111 extendTvSubst, extendTvSubstList, isInScope, mkTvSubst, zipTyEnv,
112 substTy, substTys, substTyWith, substTheta, substTyVar, substTyVars, substTyVarBndr,
114 isUnLiftedType, -- Source types are always lifted
115 isUnboxedTupleType, -- Ditto
118 tidyTopType, tidyType, tidyPred, tidyTypes, tidyFreeTyVars, tidyOpenType, tidyOpenTypes,
119 tidyTyVarBndr, tidyOpenTyVar, tidyOpenTyVars, tidySkolemTyVar,
122 tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tyVarsOfTheta,
123 tcTyVarsOfType, tcTyVarsOfTypes, exactTyVarsOfType, exactTyVarsOfTypes,
125 pprKind, pprParendKind,
126 pprType, pprParendType, pprTypeApp, pprTyThingCategory,
127 pprPred, pprTheta, pprThetaArrow, pprClassPred
131 #include "HsVersions.h"
164 %************************************************************************
168 %************************************************************************
170 The type checker divides the generic Type world into the
171 following more structured beasts:
173 sigma ::= forall tyvars. phi
174 -- A sigma type is a qualified type
176 -- Note that even if 'tyvars' is empty, theta
177 -- may not be: e.g. (?x::Int) => Int
179 -- Note that 'sigma' is in prenex form:
180 -- all the foralls are at the front.
181 -- A 'phi' type has no foralls to the right of
189 -- A 'tau' type has no quantification anywhere
190 -- Note that the args of a type constructor must be taus
192 | tycon tau_1 .. tau_n
196 -- In all cases, a (saturated) type synonym application is legal,
197 -- provided it expands to the required form.
200 type TcTyVar = TyVar -- Used only during type inference
201 type TcType = Type -- A TcType can have mutable type variables
202 -- Invariant on ForAllTy in TcTypes:
204 -- a cannot occur inside a MutTyVar in T; that is,
205 -- T is "flattened" before quantifying over a
207 -- These types do not have boxy type variables in them
208 type TcPredType = PredType
209 type TcThetaType = ThetaType
210 type TcSigmaType = TcType
211 type TcRhoType = TcType
212 type TcTauType = TcType
214 type TcTyVarSet = TyVarSet
216 -- These types may have boxy type variables in them
217 type BoxyTyVar = TcTyVar
218 type BoxyRhoType = TcType
219 type BoxyThetaType = TcThetaType
220 type BoxySigmaType = TcType
221 type BoxyType = TcType
225 %************************************************************************
227 \subsection{TyVarDetails}
229 %************************************************************************
231 TyVarDetails gives extra info about type variables, used during type
232 checking. It's attached to mutable type variables only.
233 It's knot-tied back to Var.lhs. There is no reason in principle
234 why Var.lhs shouldn't actually have the definition, but it "belongs" here.
237 Note [Signature skolems]
238 ~~~~~~~~~~~~~~~~~~~~~~~~
243 (x,y,z) = ([y,z], z, head x)
245 Here, x and y have type sigs, which go into the environment. We used to
246 instantiate their types with skolem constants, and push those types into
247 the RHS, so we'd typecheck the RHS with type
249 where a*, b* are skolem constants, and c is an ordinary meta type varible.
251 The trouble is that the occurrences of z in the RHS force a* and b* to
252 be the *same*, so we can't make them into skolem constants that don't unify
253 with each other. Alas.
255 One solution would be insist that in the above defn the programmer uses
256 the same type variable in both type signatures. But that takes explanation.
258 The alternative (currently implemented) is to have a special kind of skolem
259 constant, SigTv, which can unify with other SigTvs. These are *not* treated
260 as righd for the purposes of GADTs. And they are used *only* for pattern
261 bindings and mutually recursive function bindings. See the function
262 TcBinds.tcInstSig, and its use_skols parameter.
266 -- A TyVarDetails is inside a TyVar
268 = SkolemTv SkolemInfo -- A skolem constant
270 | MetaTv BoxInfo (IORef MetaDetails)
273 = BoxTv -- The contents is a (non-boxy) sigma-type
274 -- That is, this MetaTv is a "box"
276 | TauTv -- The contents is a (non-boxy) tau-type
277 -- That is, this MetaTv is an ordinary unification variable
279 | SigTv SkolemInfo -- A variant of TauTv, except that it should not be
280 -- unified with a type, only with a type variable
281 -- SigTvs are only distinguished to improve error messages
282 -- see Note [Signature skolems]
283 -- The MetaDetails, if filled in, will
284 -- always be another SigTv or a SkolemTv
287 -- A TauTv is always filled in with a tau-type, which
288 -- never contains any BoxTvs, nor any ForAlls
290 -- However, a BoxTv can contain a type that contains further BoxTvs
291 -- Notably, when typechecking an explicit list, say [e1,e2], with
292 -- expected type being a box b1, we fill in b1 with (List b2), where
293 -- b2 is another (currently empty) box.
296 = Flexi -- Flexi type variables unify to become
299 | Indirect TcType -- INVARIANT:
300 -- For a BoxTv, this type must be non-boxy
301 -- For a TauTv, this type must be a tau-type
303 -- Generally speaking, SkolemInfo should not contain location info
304 -- that is contained in the Name of the tyvar with this SkolemInfo
306 = SigSkol UserTypeCtxt -- A skolem that is created by instantiating
307 -- a programmer-supplied type signature
308 -- Location of the binding site is on the TyVar
310 -- The rest are for non-scoped skolems
311 | ClsSkol Class -- Bound at a class decl
312 | InstSkol -- Bound at an instance decl
313 | FamInstSkol -- Bound at a family instance decl
314 | PatSkol DataCon -- An existential type variable bound by a pattern for
315 -- a data constructor with an existential type. E.g.
316 -- data T = forall a. Eq a => MkT a
318 -- The pattern MkT x will allocate an existential type
320 | ArrowSkol -- An arrow form (see TcArrows)
322 | RuleSkol RuleName -- The LHS of a RULE
323 | GenSkol [TcTyVar] -- Bound when doing a subsumption check for
324 TcType -- (forall tvs. ty)
326 | UnkSkol -- Unhelpful info (until I improve it)
328 -------------------------------------
329 -- UserTypeCtxt describes the places where a
330 -- programmer-written type signature can occur
331 -- Like SkolemInfo, no location info
333 = FunSigCtxt Name -- Function type signature
334 -- Also used for types in SPECIALISE pragmas
335 | ExprSigCtxt -- Expression type signature
336 | ConArgCtxt Name -- Data constructor argument
337 | TySynCtxt Name -- RHS of a type synonym decl
338 | GenPatCtxt -- Pattern in generic decl
339 -- f{| a+b |} (Inl x) = ...
340 | LamPatSigCtxt -- Type sig in lambda pattern
342 | BindPatSigCtxt -- Type sig in pattern binding pattern
344 | ResSigCtxt -- Result type sig
346 | ForSigCtxt Name -- Foreign inport or export signature
347 | DefaultDeclCtxt -- Types in a default declaration
348 | SpecInstCtxt -- SPECIALISE instance pragma
350 -- Notes re TySynCtxt
351 -- We allow type synonyms that aren't types; e.g. type List = []
353 -- If the RHS mentions tyvars that aren't in scope, we'll
354 -- quantify over them:
355 -- e.g. type T = a->a
356 -- will become type T = forall a. a->a
358 -- With gla-exts that's right, but for H98 we should complain.
360 ---------------------------------
363 mkKindName :: Unique -> Name
364 mkKindName unique = mkSystemName unique kind_var_occ
366 kindVarRef :: KindVar -> IORef MetaDetails
368 ASSERT ( isTcTyVar tc )
369 case tcTyVarDetails tc of
370 MetaTv TauTv ref -> ref
371 other -> pprPanic "kindVarRef" (ppr tc)
373 mkKindVar :: Unique -> IORef MetaDetails -> KindVar
375 = mkTcTyVar (mkKindName u)
376 tySuperKind -- not sure this is right,
377 -- do we need kind vars for
381 kind_var_occ :: OccName -- Just one for all KindVars
382 -- They may be jiggled by tidying
383 kind_var_occ = mkOccName tvName "k"
387 %************************************************************************
391 %************************************************************************
394 pprTcTyVarDetails :: TcTyVarDetails -> SDoc
396 pprTcTyVarDetails (SkolemTv _) = ptext SLIT("sk")
397 pprTcTyVarDetails (MetaTv BoxTv _) = ptext SLIT("box")
398 pprTcTyVarDetails (MetaTv TauTv _) = ptext SLIT("tau")
399 pprTcTyVarDetails (MetaTv (SigTv _) _) = ptext SLIT("sig")
401 pprUserTypeCtxt :: UserTypeCtxt -> SDoc
402 pprUserTypeCtxt (FunSigCtxt n) = ptext SLIT("the type signature for") <+> quotes (ppr n)
403 pprUserTypeCtxt ExprSigCtxt = ptext SLIT("an expression type signature")
404 pprUserTypeCtxt (ConArgCtxt c) = ptext SLIT("the type of the constructor") <+> quotes (ppr c)
405 pprUserTypeCtxt (TySynCtxt c) = ptext SLIT("the RHS of the type synonym") <+> quotes (ppr c)
406 pprUserTypeCtxt GenPatCtxt = ptext SLIT("the type pattern of a generic definition")
407 pprUserTypeCtxt LamPatSigCtxt = ptext SLIT("a pattern type signature")
408 pprUserTypeCtxt BindPatSigCtxt = ptext SLIT("a pattern type signature")
409 pprUserTypeCtxt ResSigCtxt = ptext SLIT("a result type signature")
410 pprUserTypeCtxt (ForSigCtxt n) = ptext SLIT("the foreign declaration for") <+> quotes (ppr n)
411 pprUserTypeCtxt DefaultDeclCtxt = ptext SLIT("a type in a `default' declaration")
412 pprUserTypeCtxt SpecInstCtxt = ptext SLIT("a SPECIALISE instance pragma")
415 --------------------------------
416 tidySkolemTyVar :: TidyEnv -> TcTyVar -> (TidyEnv, TcTyVar)
417 -- Tidy the type inside a GenSkol, preparatory to printing it
418 tidySkolemTyVar env tv
419 = ASSERT( isSkolemTyVar tv || isSigTyVar tv )
420 (env1, mkTcTyVar (tyVarName tv) (tyVarKind tv) info1)
422 (env1, info1) = case tcTyVarDetails tv of
423 SkolemTv info -> (env1, SkolemTv info')
425 (env1, info') = tidy_skol_info env info
426 MetaTv (SigTv info) box -> (env1, MetaTv (SigTv info') box)
428 (env1, info') = tidy_skol_info env info
431 tidy_skol_info env (GenSkol tvs ty) = (env2, GenSkol tvs1 ty1)
433 (env1, tvs1) = tidyOpenTyVars env tvs
434 (env2, ty1) = tidyOpenType env1 ty
435 tidy_skol_info env info = (env, info)
437 pprSkolTvBinding :: TcTyVar -> SDoc
438 -- Print info about the binding of a skolem tyvar,
439 -- or nothing if we don't have anything useful to say
441 = ASSERT ( isTcTyVar tv )
442 ppr_details (tcTyVarDetails tv)
444 ppr_details (MetaTv TauTv _) = quotes (ppr tv) <+> ptext SLIT("is a meta type variable")
445 ppr_details (MetaTv BoxTv _) = quotes (ppr tv) <+> ptext SLIT("is a boxy type variable")
446 ppr_details (MetaTv (SigTv info) _) = ppr_skol info
447 ppr_details (SkolemTv info) = ppr_skol info
449 ppr_skol UnkSkol = empty -- Unhelpful; omit
450 ppr_skol info = quotes (ppr tv) <+> ptext SLIT("is bound by")
451 <+> sep [pprSkolInfo info, nest 2 (ptext SLIT("at") <+> ppr (getSrcLoc tv))]
453 pprSkolInfo :: SkolemInfo -> SDoc
454 pprSkolInfo (SigSkol ctxt) = pprUserTypeCtxt ctxt
455 pprSkolInfo (ClsSkol cls) = ptext SLIT("the class declaration for") <+> quotes (ppr cls)
456 pprSkolInfo InstSkol = ptext SLIT("the instance declaration")
457 pprSkolInfo FamInstSkol = ptext SLIT("the family instance declaration")
458 pprSkolInfo (RuleSkol name) = ptext SLIT("the RULE") <+> doubleQuotes (ftext name)
459 pprSkolInfo ArrowSkol = ptext SLIT("the arrow form")
460 pprSkolInfo (PatSkol dc) = sep [ptext SLIT("the constructor") <+> quotes (ppr dc)]
461 pprSkolInfo (GenSkol tvs ty) = sep [ptext SLIT("the polymorphic type"),
462 nest 2 (quotes (ppr (mkForAllTys tvs ty)))]
465 -- For type variables the others are dealt with by pprSkolTvBinding.
466 -- For Insts, these cases should not happen
467 pprSkolInfo UnkSkol = panic "UnkSkol"
469 instance Outputable MetaDetails where
470 ppr Flexi = ptext SLIT("Flexi")
471 ppr (Indirect ty) = ptext SLIT("Indirect") <+> ppr ty
475 %************************************************************************
479 %************************************************************************
482 isImmutableTyVar :: TyVar -> Bool
485 | isTcTyVar tv = isSkolemTyVar tv
488 isTyConableTyVar, isSkolemTyVar, isExistentialTyVar,
489 isBoxyTyVar, isMetaTyVar :: TcTyVar -> Bool
492 -- True of a meta-type variable tha can be filled in
493 -- with a type constructor application; in particular,
495 = ASSERT( isTcTyVar tv)
496 case tcTyVarDetails tv of
497 MetaTv BoxTv _ -> True
498 MetaTv TauTv _ -> True
499 MetaTv (SigTv {}) _ -> False
503 = ASSERT( isTcTyVar tv )
504 case tcTyVarDetails tv of
508 isExistentialTyVar tv -- Existential type variable, bound by a pattern
509 = ASSERT( isTcTyVar tv )
510 case tcTyVarDetails tv of
511 SkolemTv (PatSkol {}) -> True
515 = ASSERT2( isTcTyVar tv, ppr tv )
516 case tcTyVarDetails tv of
521 = ASSERT( isTcTyVar tv )
522 case tcTyVarDetails tv of
523 MetaTv BoxTv _ -> True
527 = ASSERT( isTcTyVar tv )
528 case tcTyVarDetails tv of
529 MetaTv (SigTv _) _ -> True
532 metaTvRef :: TyVar -> IORef MetaDetails
534 = ASSERT( isTcTyVar tv )
535 case tcTyVarDetails tv of
537 other -> pprPanic "metaTvRef" (ppr tv)
539 isFlexi, isIndirect :: MetaDetails -> Bool
541 isFlexi other = False
543 isIndirect (Indirect _) = True
544 isIndirect other = False
548 %************************************************************************
550 \subsection{Tau, sigma and rho}
552 %************************************************************************
555 mkSigmaTy :: [TyVar] -> [PredType] -> Type -> Type
556 mkSigmaTy tyvars theta tau = mkForAllTys tyvars (mkPhiTy theta tau)
558 mkPhiTy :: [PredType] -> Type -> Type
559 mkPhiTy theta ty = foldr (\p r -> mkFunTy (mkPredTy p) r) ty theta
562 @isTauTy@ tests for nested for-alls. It should not be called on a boxy type.
565 isTauTy :: Type -> Bool
566 isTauTy ty | Just ty' <- tcView ty = isTauTy ty'
567 isTauTy (TyVarTy tv) = ASSERT( not (isTcTyVar tv && isBoxyTyVar tv) )
569 isTauTy (TyConApp tc tys) = all isTauTy tys && isTauTyCon tc
570 isTauTy (AppTy a b) = isTauTy a && isTauTy b
571 isTauTy (FunTy a b) = isTauTy a && isTauTy b
572 isTauTy (PredTy p) = True -- Don't look through source types
573 isTauTy other = False
576 isTauTyCon :: TyCon -> Bool
577 -- Returns False for type synonyms whose expansion is a polytype
579 | isClosedSynTyCon tc = isTauTy (snd (synTyConDefn tc))
583 isBoxyTy :: TcType -> Bool
584 isBoxyTy ty = any isBoxyTyVar (varSetElems (tcTyVarsOfType ty))
586 isRigidTy :: TcType -> Bool
587 -- A type is rigid if it has no meta type variables in it
588 isRigidTy ty = all isImmutableTyVar (varSetElems (tcTyVarsOfType ty))
590 isRefineableTy :: TcType -> Bool
591 -- A type should have type refinements applied to it if it has
592 -- free type variables, and they are all rigid
593 isRefineableTy ty = not (null tc_tvs) && all isImmutableTyVar tc_tvs
595 tc_tvs = varSetElems (tcTyVarsOfType ty)
597 isRefineablePred :: TcPredType -> Bool
598 isRefineablePred pred = not (null tc_tvs) && all isImmutableTyVar tc_tvs
600 tc_tvs = varSetElems (tcTyVarsOfPred pred)
603 getDFunTyKey :: Type -> OccName -- Get some string from a type, to be used to
604 -- construct a dictionary function name
605 getDFunTyKey ty | Just ty' <- tcView ty = getDFunTyKey ty'
606 getDFunTyKey (TyVarTy tv) = getOccName tv
607 getDFunTyKey (TyConApp tc _) = getOccName tc
608 getDFunTyKey (AppTy fun _) = getDFunTyKey fun
609 getDFunTyKey (FunTy arg _) = getOccName funTyCon
610 getDFunTyKey (ForAllTy _ t) = getDFunTyKey t
611 getDFunTyKey ty = pprPanic "getDFunTyKey" (pprType ty)
612 -- PredTy shouldn't happen
616 %************************************************************************
618 \subsection{Expanding and splitting}
620 %************************************************************************
622 These tcSplit functions are like their non-Tc analogues, but
623 a) they do not look through newtypes
624 b) they do not look through PredTys
625 c) [future] they ignore usage-type annotations
627 However, they are non-monadic and do not follow through mutable type
628 variables. It's up to you to make sure this doesn't matter.
631 tcSplitForAllTys :: Type -> ([TyVar], Type)
632 tcSplitForAllTys ty = split ty ty []
634 split orig_ty ty tvs | Just ty' <- tcView ty = split orig_ty ty' tvs
635 split orig_ty (ForAllTy tv ty) tvs
636 | not (isCoVar tv) = split ty ty (tv:tvs)
637 split orig_ty t tvs = (reverse tvs, orig_ty)
639 tcIsForAllTy ty | Just ty' <- tcView ty = tcIsForAllTy ty'
640 tcIsForAllTy (ForAllTy tv ty) = not (isCoVar tv)
641 tcIsForAllTy t = False
643 tcSplitPhiTy :: Type -> (ThetaType, Type)
644 tcSplitPhiTy ty = split ty ty []
646 split orig_ty ty tvs | Just ty' <- tcView ty = split orig_ty ty' tvs
648 split orig_ty (ForAllTy tv ty) ts
649 | isCoVar tv = split ty ty (eq_pred:ts)
651 PredTy eq_pred = tyVarKind tv
652 split orig_ty (FunTy arg res) ts
653 | Just p <- tcSplitPredTy_maybe arg = split res res (p:ts)
654 split orig_ty ty ts = (reverse ts, orig_ty)
656 tcSplitSigmaTy :: Type -> ([TyVar], ThetaType, Type)
657 tcSplitSigmaTy ty = case tcSplitForAllTys ty of
658 (tvs, rho) -> case tcSplitPhiTy rho of
659 (theta, tau) -> (tvs, theta, tau)
661 -----------------------
664 -> ( [([TyVar], ThetaType)], -- forall as.C => forall bs.D
665 TcSigmaType) -- The rest of the type
667 -- We need a loop here because we are now prepared to entertain
669 -- f:: forall a. Eq a => forall b. Baz b => tau
670 -- We want to instantiate this to
671 -- f2::tau {f2 = f1 b (Baz b), f1 = f a (Eq a)}
673 tcMultiSplitSigmaTy sigma
674 = case (tcSplitSigmaTy sigma) of
675 ([],[],ty) -> ([], sigma)
676 (tvs, theta, ty) -> case tcMultiSplitSigmaTy ty of
677 (pairs, rest) -> ((tvs,theta):pairs, rest)
679 -----------------------
680 tcTyConAppTyCon :: Type -> TyCon
681 tcTyConAppTyCon ty = case tcSplitTyConApp_maybe ty of
683 Nothing -> pprPanic "tcTyConAppTyCon" (pprType ty)
685 tcTyConAppArgs :: Type -> [Type]
686 tcTyConAppArgs ty = case tcSplitTyConApp_maybe ty of
687 Just (_, args) -> args
688 Nothing -> pprPanic "tcTyConAppArgs" (pprType ty)
690 tcSplitTyConApp :: Type -> (TyCon, [Type])
691 tcSplitTyConApp ty = case tcSplitTyConApp_maybe ty of
693 Nothing -> pprPanic "tcSplitTyConApp" (pprType ty)
695 tcSplitTyConApp_maybe :: Type -> Maybe (TyCon, [Type])
696 tcSplitTyConApp_maybe ty | Just ty' <- tcView ty = tcSplitTyConApp_maybe ty'
697 tcSplitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
698 tcSplitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res])
699 -- Newtypes are opaque, so they may be split
700 -- However, predicates are not treated
701 -- as tycon applications by the type checker
702 tcSplitTyConApp_maybe other = Nothing
704 -----------------------
705 tcSplitFunTys :: Type -> ([Type], Type)
706 tcSplitFunTys ty = case tcSplitFunTy_maybe ty of
708 Just (arg,res) -> (arg:args, res')
710 (args,res') = tcSplitFunTys res
712 tcSplitFunTy_maybe :: Type -> Maybe (Type, Type)
713 tcSplitFunTy_maybe ty | Just ty' <- tcView ty = tcSplitFunTy_maybe ty'
714 tcSplitFunTy_maybe (FunTy arg res) = Just (arg, res)
715 tcSplitFunTy_maybe other = Nothing
719 -> Arity -- N: Number of desired args
720 -> ([TcSigmaType], -- Arg types (N or fewer)
721 TcSigmaType) -- The rest of the type
723 tcSplitFunTysN ty n_args
726 | Just (arg,res) <- tcSplitFunTy_maybe ty
727 = case tcSplitFunTysN res (n_args - 1) of
728 (args, res) -> (arg:args, res)
732 tcSplitFunTy ty = expectJust "tcSplitFunTy" (tcSplitFunTy_maybe ty)
733 tcFunArgTy ty = fst (tcSplitFunTy ty)
734 tcFunResultTy ty = snd (tcSplitFunTy ty)
736 -----------------------
737 tcSplitAppTy_maybe :: Type -> Maybe (Type, Type)
738 tcSplitAppTy_maybe ty | Just ty' <- tcView ty = tcSplitAppTy_maybe ty'
739 tcSplitAppTy_maybe ty = repSplitAppTy_maybe ty
741 tcSplitAppTy :: Type -> (Type, Type)
742 tcSplitAppTy ty = case tcSplitAppTy_maybe ty of
744 Nothing -> pprPanic "tcSplitAppTy" (pprType ty)
746 tcSplitAppTys :: Type -> (Type, [Type])
750 go ty args = case tcSplitAppTy_maybe ty of
751 Just (ty', arg) -> go ty' (arg:args)
754 -----------------------
755 tcGetTyVar_maybe :: Type -> Maybe TyVar
756 tcGetTyVar_maybe ty | Just ty' <- tcView ty = tcGetTyVar_maybe ty'
757 tcGetTyVar_maybe (TyVarTy tv) = Just tv
758 tcGetTyVar_maybe other = Nothing
760 tcGetTyVar :: String -> Type -> TyVar
761 tcGetTyVar msg ty = expectJust msg (tcGetTyVar_maybe ty)
763 tcIsTyVarTy :: Type -> Bool
764 tcIsTyVarTy ty = maybeToBool (tcGetTyVar_maybe ty)
766 -----------------------
767 tcSplitDFunTy :: Type -> ([TyVar], [PredType], Class, [Type])
768 -- Split the type of a dictionary function
770 = case tcSplitSigmaTy ty of { (tvs, theta, tau) ->
771 case tcSplitDFunHead tau of { (clas, tys) ->
772 (tvs, theta, clas, tys) }}
774 tcSplitDFunHead :: Type -> (Class, [Type])
776 = case tcSplitPredTy_maybe tau of
777 Just (ClassP clas tys) -> (clas, tys)
778 other -> panic "tcSplitDFunHead"
780 tcValidInstHeadTy :: Type -> Bool
781 -- Used in Haskell-98 mode, for the argument types of an instance head
782 -- These must not be type synonyms, but everywhere else type synonyms
783 -- are transparent, so we need a special function here
786 NoteTy _ ty -> tcValidInstHeadTy ty
787 TyConApp tc tys -> not (isSynTyCon tc) && ok tys
788 FunTy arg res -> ok [arg, res]
791 -- Check that all the types are type variables,
792 -- and that each is distinct
793 ok tys = equalLength tvs tys && hasNoDups tvs
795 tvs = mapCatMaybes get_tv tys
797 get_tv (NoteTy _ ty) = get_tv ty -- Again, do not look
798 get_tv (TyVarTy tv) = Just tv -- through synonyms
799 get_tv other = Nothing
804 %************************************************************************
806 \subsection{Predicate types}
808 %************************************************************************
811 tcSplitPredTy_maybe :: Type -> Maybe PredType
812 -- Returns Just for predicates only
813 tcSplitPredTy_maybe ty | Just ty' <- tcView ty = tcSplitPredTy_maybe ty'
814 tcSplitPredTy_maybe (PredTy p) = Just p
815 tcSplitPredTy_maybe other = Nothing
817 predTyUnique :: PredType -> Unique
818 predTyUnique (IParam n _) = getUnique (ipNameName n)
819 predTyUnique (ClassP clas tys) = getUnique clas
823 --------------------- Dictionary types ---------------------------------
826 mkClassPred clas tys = ClassP clas tys
828 isClassPred :: PredType -> Bool
829 isClassPred (ClassP clas tys) = True
830 isClassPred other = False
832 isTyVarClassPred (ClassP clas tys) = all tcIsTyVarTy tys
833 isTyVarClassPred other = False
835 getClassPredTys_maybe :: PredType -> Maybe (Class, [Type])
836 getClassPredTys_maybe (ClassP clas tys) = Just (clas, tys)
837 getClassPredTys_maybe _ = Nothing
839 getClassPredTys :: PredType -> (Class, [Type])
840 getClassPredTys (ClassP clas tys) = (clas, tys)
841 getClassPredTys other = panic "getClassPredTys"
843 mkDictTy :: Class -> [Type] -> Type
844 mkDictTy clas tys = mkPredTy (ClassP clas tys)
846 isDictTy :: Type -> Bool
847 isDictTy ty | Just ty' <- tcView ty = isDictTy ty'
848 isDictTy (PredTy p) = isClassPred p
849 isDictTy other = False
852 --------------------- Implicit parameters ---------------------------------
855 isIPPred :: PredType -> Bool
856 isIPPred (IParam _ _) = True
857 isIPPred other = False
859 isInheritablePred :: PredType -> Bool
860 -- Can be inherited by a context. For example, consider
861 -- f x = let g y = (?v, y+x)
862 -- in (g 3 with ?v = 8,
864 -- The point is that g's type must be quantifed over ?v:
865 -- g :: (?v :: a) => a -> a
866 -- but it doesn't need to be quantified over the Num a dictionary
867 -- which can be free in g's rhs, and shared by both calls to g
868 isInheritablePred (ClassP _ _) = True
869 isInheritablePred (EqPred _ _) = True
870 isInheritablePred other = False
873 --------------------- Equality predicates ---------------------------------
875 substEqSpec :: TvSubst -> [(TyVar,Type)] -> [(TcType,TcType)]
876 substEqSpec subst eq_spec = [ (substTyVar subst tv, substTy subst ty)
877 | (tv,ty) <- eq_spec]
880 --------------------- The stupid theta (sigh) ---------------------------------
883 dataConsStupidTheta :: [DataCon] -> ThetaType
884 -- Union the stupid thetas from all the specified constructors (non-empty)
885 -- All the constructors should have the same result type, modulo alpha conversion
886 -- The resulting ThetaType uses type variables from the *first* constructor in the list
888 -- It's here because it's used in MkId.mkRecordSelId, and in TcExpr
889 dataConsStupidTheta (con1:cons)
890 = nubBy tcEqPred all_preds
892 all_preds = dataConStupidTheta con1 ++ other_stupids
893 res_tys1 = dataConResTys con1
894 tvs1 = tyVarsOfTypes res_tys1
895 other_stupids = [ substPred subst pred
897 , let Just subst = tcMatchTys tvs1 res_tys1 (dataConResTys con)
898 , pred <- dataConStupidTheta con ]
899 dataConsStupidTheta [] = panic "dataConsStupidTheta"
903 %************************************************************************
905 \subsection{Predicates}
907 %************************************************************************
909 isSigmaTy returns true of any qualified type. It doesn't *necessarily* have
911 f :: (?x::Int) => Int -> Int
914 isSigmaTy :: Type -> Bool
915 isSigmaTy ty | Just ty' <- tcView ty = isSigmaTy ty'
916 isSigmaTy (ForAllTy tyvar ty) = True
917 isSigmaTy (FunTy a b) = isPredTy a
920 isOverloadedTy :: Type -> Bool
921 isOverloadedTy ty | Just ty' <- tcView ty = isOverloadedTy ty'
922 isOverloadedTy (ForAllTy tyvar ty) = isOverloadedTy ty
923 isOverloadedTy (FunTy a b) = isPredTy a
924 isOverloadedTy _ = False
926 isPredTy :: Type -> Bool -- Belongs in TcType because it does
927 -- not look through newtypes, or predtypes (of course)
928 isPredTy ty | Just ty' <- tcView ty = isPredTy ty'
929 isPredTy (PredTy sty) = True
934 isFloatTy = is_tc floatTyConKey
935 isDoubleTy = is_tc doubleTyConKey
936 isIntegerTy = is_tc integerTyConKey
937 isIntTy = is_tc intTyConKey
938 isBoolTy = is_tc boolTyConKey
939 isUnitTy = is_tc unitTyConKey
941 is_tc :: Unique -> Type -> Bool
942 -- Newtypes are opaque to this
943 is_tc uniq ty = case tcSplitTyConApp_maybe ty of
944 Just (tc, _) -> uniq == getUnique tc
949 %************************************************************************
953 %************************************************************************
956 deNoteType :: Type -> Type
957 -- Remove all *outermost* type synonyms and other notes
958 deNoteType ty | Just ty' <- tcView ty = deNoteType ty'
963 tcTyVarsOfType :: Type -> TcTyVarSet
964 -- Just the *TcTyVars* free in the type
965 -- (Types.tyVarsOfTypes finds all free TyVars)
966 tcTyVarsOfType (TyVarTy tv) = if isTcTyVar tv then unitVarSet tv
968 tcTyVarsOfType (TyConApp tycon tys) = tcTyVarsOfTypes tys
969 tcTyVarsOfType (NoteTy _ ty) = tcTyVarsOfType ty
970 tcTyVarsOfType (PredTy sty) = tcTyVarsOfPred sty
971 tcTyVarsOfType (FunTy arg res) = tcTyVarsOfType arg `unionVarSet` tcTyVarsOfType res
972 tcTyVarsOfType (AppTy fun arg) = tcTyVarsOfType fun `unionVarSet` tcTyVarsOfType arg
973 tcTyVarsOfType (ForAllTy tyvar ty) = (tcTyVarsOfType ty `delVarSet` tyvar)
974 `unionVarSet` tcTyVarsOfTyVar tyvar
975 -- We do sometimes quantify over skolem TcTyVars
977 tcTyVarsOfTyVar :: TcTyVar -> TyVarSet
978 tcTyVarsOfTyVar tv | isCoVar tv = tcTyVarsOfType (tyVarKind tv)
979 | otherwise = emptyVarSet
981 tcTyVarsOfTypes :: [Type] -> TyVarSet
982 tcTyVarsOfTypes tys = foldr (unionVarSet.tcTyVarsOfType) emptyVarSet tys
984 tcTyVarsOfPred :: PredType -> TyVarSet
985 tcTyVarsOfPred (IParam _ ty) = tcTyVarsOfType ty
986 tcTyVarsOfPred (ClassP _ tys) = tcTyVarsOfTypes tys
987 tcTyVarsOfPred (EqPred ty1 ty2) = tcTyVarsOfType ty1 `unionVarSet` tcTyVarsOfType ty2
990 Note [Silly type synonym]
991 ~~~~~~~~~~~~~~~~~~~~~~~~~
994 What are the free tyvars of (T x)? Empty, of course!
995 Here's the example that Ralf Laemmel showed me:
996 foo :: (forall a. C u a -> C u a) -> u
997 mappend :: Monoid u => u -> u -> u
1000 bar = foo (\t -> t `mappend` t)
1001 We have to generalise at the arg to f, and we don't
1002 want to capture the constraint (Monad (C u a)) because
1003 it appears to mention a. Pretty silly, but it was useful to him.
1005 exactTyVarsOfType is used by the type checker to figure out exactly
1006 which type variables are mentioned in a type. It's also used in the
1007 smart-app checking code --- see TcExpr.tcIdApp
1010 exactTyVarsOfType :: TcType -> TyVarSet
1011 -- Find the free type variables (of any kind)
1012 -- but *expand* type synonyms. See Note [Silly type synonym] above.
1013 exactTyVarsOfType ty
1016 go ty | Just ty' <- tcView ty = go ty' -- This is the key line
1017 go (TyVarTy tv) = unitVarSet tv
1018 go (TyConApp tycon tys) = exactTyVarsOfTypes tys
1019 go (PredTy ty) = go_pred ty
1020 go (FunTy arg res) = go arg `unionVarSet` go res
1021 go (AppTy fun arg) = go fun `unionVarSet` go arg
1022 go (ForAllTy tyvar ty) = delVarSet (go ty) tyvar
1023 `unionVarSet` go_tv tyvar
1025 go_pred (IParam _ ty) = go ty
1026 go_pred (ClassP _ tys) = exactTyVarsOfTypes tys
1027 go_pred (EqPred ty1 ty2) = go ty1 `unionVarSet` go ty2
1029 go_tv tyvar | isCoVar tyvar = go (tyVarKind tyvar)
1030 | otherwise = emptyVarSet
1032 exactTyVarsOfTypes :: [TcType] -> TyVarSet
1033 exactTyVarsOfTypes tys = foldr (unionVarSet . exactTyVarsOfType) emptyVarSet tys
1036 Find the free tycons and classes of a type. This is used in the front
1037 end of the compiler.
1040 tyClsNamesOfType :: Type -> NameSet
1041 tyClsNamesOfType (TyVarTy tv) = emptyNameSet
1042 tyClsNamesOfType (TyConApp tycon tys) = unitNameSet (getName tycon) `unionNameSets` tyClsNamesOfTypes tys
1043 tyClsNamesOfType (NoteTy _ ty2) = tyClsNamesOfType ty2
1044 tyClsNamesOfType (PredTy (IParam n ty)) = tyClsNamesOfType ty
1045 tyClsNamesOfType (PredTy (ClassP cl tys)) = unitNameSet (getName cl) `unionNameSets` tyClsNamesOfTypes tys
1046 tyClsNamesOfType (PredTy (EqPred ty1 ty2)) = tyClsNamesOfType ty1 `unionNameSets` tyClsNamesOfType ty2
1047 tyClsNamesOfType (FunTy arg res) = tyClsNamesOfType arg `unionNameSets` tyClsNamesOfType res
1048 tyClsNamesOfType (AppTy fun arg) = tyClsNamesOfType fun `unionNameSets` tyClsNamesOfType arg
1049 tyClsNamesOfType (ForAllTy tyvar ty) = tyClsNamesOfType ty
1051 tyClsNamesOfTypes tys = foldr (unionNameSets . tyClsNamesOfType) emptyNameSet tys
1053 tyClsNamesOfDFunHead :: Type -> NameSet
1054 -- Find the free type constructors and classes
1055 -- of the head of the dfun instance type
1056 -- The 'dfun_head_type' is because of
1057 -- instance Foo a => Baz T where ...
1058 -- The decl is an orphan if Baz and T are both not locally defined,
1059 -- even if Foo *is* locally defined
1060 tyClsNamesOfDFunHead dfun_ty
1061 = case tcSplitSigmaTy dfun_ty of
1062 (tvs,_,head_ty) -> tyClsNamesOfType head_ty
1066 %************************************************************************
1068 \subsection[TysWiredIn-ext-type]{External types}
1070 %************************************************************************
1072 The compiler's foreign function interface supports the passing of a
1073 restricted set of types as arguments and results (the restricting factor
1077 tcSplitIOType_maybe :: Type -> Maybe (TyCon, Type)
1078 -- (isIOType t) returns (Just (IO,t')) if t is of the form (IO t'), or
1079 -- some newtype wrapping thereof
1080 -- returns Nothing otherwise
1081 tcSplitIOType_maybe ty
1082 | Just (io_tycon, [io_res_ty]) <- tcSplitTyConApp_maybe ty,
1083 -- This split absolutely has to be a tcSplit, because we must
1084 -- see the IO type; and it's a newtype which is transparent to splitTyConApp.
1085 io_tycon `hasKey` ioTyConKey
1086 = Just (io_tycon, io_res_ty)
1088 | Just ty' <- coreView ty -- Look through non-recursive newtypes
1089 = tcSplitIOType_maybe ty'
1094 isFFITy :: Type -> Bool
1095 -- True for any TyCon that can possibly be an arg or result of an FFI call
1096 isFFITy ty = checkRepTyCon legalFFITyCon ty
1098 isFFIArgumentTy :: DynFlags -> Safety -> Type -> Bool
1099 -- Checks for valid argument type for a 'foreign import'
1100 isFFIArgumentTy dflags safety ty
1101 = checkRepTyCon (legalOutgoingTyCon dflags safety) ty
1103 isFFIExternalTy :: Type -> Bool
1104 -- Types that are allowed as arguments of a 'foreign export'
1105 isFFIExternalTy ty = checkRepTyCon legalFEArgTyCon ty
1107 isFFIImportResultTy :: DynFlags -> Type -> Bool
1108 isFFIImportResultTy dflags ty
1109 = checkRepTyCon (legalFIResultTyCon dflags) ty
1111 isFFIExportResultTy :: Type -> Bool
1112 isFFIExportResultTy ty = checkRepTyCon legalFEResultTyCon ty
1114 isFFIDynArgumentTy :: Type -> Bool
1115 -- The argument type of a foreign import dynamic must be Ptr, FunPtr, Addr,
1116 -- or a newtype of either.
1117 isFFIDynArgumentTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1119 isFFIDynResultTy :: Type -> Bool
1120 -- The result type of a foreign export dynamic must be Ptr, FunPtr, Addr,
1121 -- or a newtype of either.
1122 isFFIDynResultTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1124 isFFILabelTy :: Type -> Bool
1125 -- The type of a foreign label must be Ptr, FunPtr, Addr,
1126 -- or a newtype of either.
1127 isFFILabelTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1129 isFFIDotnetTy :: DynFlags -> Type -> Bool
1130 isFFIDotnetTy dflags ty
1131 = checkRepTyCon (\ tc -> (legalFIResultTyCon dflags tc ||
1132 isFFIDotnetObjTy ty || isStringTy ty)) ty
1134 -- Support String as an argument or result from a .NET FFI call.
1136 case tcSplitTyConApp_maybe (repType ty) of
1138 | tc == listTyCon ->
1139 case tcSplitTyConApp_maybe (repType arg_ty) of
1140 Just (cc,[]) -> cc == charTyCon
1144 -- Support String as an argument or result from a .NET FFI call.
1145 isFFIDotnetObjTy ty =
1147 (_, t_ty) = tcSplitForAllTys ty
1149 case tcSplitTyConApp_maybe (repType t_ty) of
1150 Just (tc, [arg_ty]) | getName tc == objectTyConName -> True
1153 toDNType :: Type -> DNType
1155 | isStringTy ty = DNString
1156 | isFFIDotnetObjTy ty = DNObject
1157 | Just (tc,argTys) <- tcSplitTyConApp_maybe ty
1158 = case lookup (getUnique tc) dn_assoc of
1161 | tc `hasKey` ioTyConKey -> toDNType (head argTys)
1162 | otherwise -> pprPanic ("toDNType: unsupported .NET type")
1163 (pprType ty <+> parens (hcat (map pprType argTys)) <+> ppr tc)
1164 | otherwise = panic "toDNType" -- Is this right?
1166 dn_assoc :: [ (Unique, DNType) ]
1167 dn_assoc = [ (unitTyConKey, DNUnit)
1168 , (intTyConKey, DNInt)
1169 , (int8TyConKey, DNInt8)
1170 , (int16TyConKey, DNInt16)
1171 , (int32TyConKey, DNInt32)
1172 , (int64TyConKey, DNInt64)
1173 , (wordTyConKey, DNInt)
1174 , (word8TyConKey, DNWord8)
1175 , (word16TyConKey, DNWord16)
1176 , (word32TyConKey, DNWord32)
1177 , (word64TyConKey, DNWord64)
1178 , (floatTyConKey, DNFloat)
1179 , (doubleTyConKey, DNDouble)
1180 , (ptrTyConKey, DNPtr)
1181 , (funPtrTyConKey, DNPtr)
1182 , (charTyConKey, DNChar)
1183 , (boolTyConKey, DNBool)
1186 checkRepTyCon :: (TyCon -> Bool) -> Type -> Bool
1187 -- Look through newtypes
1188 -- Non-recursive ones are transparent to splitTyConApp,
1189 -- but recursive ones aren't. Manuel had:
1190 -- newtype T = MkT (Ptr T)
1191 -- and wanted it to work...
1192 checkRepTyCon check_tc ty
1193 | Just (tc,_) <- splitTyConApp_maybe (repType ty) = check_tc tc
1196 checkRepTyConKey :: [Unique] -> Type -> Bool
1197 -- Like checkRepTyCon, but just looks at the TyCon key
1198 checkRepTyConKey keys
1199 = checkRepTyCon (\tc -> tyConUnique tc `elem` keys)
1202 ----------------------------------------------
1203 These chaps do the work; they are not exported
1204 ----------------------------------------------
1207 legalFEArgTyCon :: TyCon -> Bool
1209 -- It's illegal to make foreign exports that take unboxed
1210 -- arguments. The RTS API currently can't invoke such things. --SDM 7/2000
1211 = boxedMarshalableTyCon tc
1213 legalFIResultTyCon :: DynFlags -> TyCon -> Bool
1214 legalFIResultTyCon dflags tc
1215 | tc == unitTyCon = True
1216 | otherwise = marshalableTyCon dflags tc
1218 legalFEResultTyCon :: TyCon -> Bool
1219 legalFEResultTyCon tc
1220 | tc == unitTyCon = True
1221 | otherwise = boxedMarshalableTyCon tc
1223 legalOutgoingTyCon :: DynFlags -> Safety -> TyCon -> Bool
1224 -- Checks validity of types going from Haskell -> external world
1225 legalOutgoingTyCon dflags safety tc
1226 = marshalableTyCon dflags tc
1228 legalFFITyCon :: TyCon -> Bool
1229 -- True for any TyCon that can possibly be an arg or result of an FFI call
1231 = isUnLiftedTyCon tc || boxedMarshalableTyCon tc || tc == unitTyCon
1233 marshalableTyCon dflags tc
1234 = (dopt Opt_GlasgowExts dflags && isUnLiftedTyCon tc)
1235 || boxedMarshalableTyCon tc
1237 boxedMarshalableTyCon tc
1238 = getUnique tc `elem` [ intTyConKey, int8TyConKey, int16TyConKey
1239 , int32TyConKey, int64TyConKey
1240 , wordTyConKey, word8TyConKey, word16TyConKey
1241 , word32TyConKey, word64TyConKey
1242 , floatTyConKey, doubleTyConKey
1243 , ptrTyConKey, funPtrTyConKey