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, isSigTyVar, isExistentialTyVar,
35 --------------------------------
39 --------------------------------
41 -- These are important because they do not look through newtypes
43 tcSplitForAllTys, tcSplitPhiTy,
44 tcSplitFunTy_maybe, tcSplitFunTys, tcFunArgTy, tcFunResultTy, tcSplitFunTysN,
45 tcSplitTyConApp, tcSplitTyConApp_maybe, tcTyConAppTyCon, tcTyConAppArgs,
46 tcSplitAppTy_maybe, tcSplitAppTy, tcSplitAppTys, repSplitAppTy_maybe,
47 tcValidInstHeadTy, tcGetTyVar_maybe, tcGetTyVar,
48 tcSplitSigmaTy, tcMultiSplitSigmaTy,
50 ---------------------------------
52 -- Again, newtypes are opaque
53 tcEqType, tcEqTypes, tcEqPred, tcCmpType, tcCmpTypes, tcCmpPred, tcEqTypeX,
55 isSigmaTy, isOverloadedTy, isRigidTy, isBoxyTy,
56 isDoubleTy, isFloatTy, isIntTy, isStringTy,
57 isIntegerTy, isBoolTy, isUnitTy,
58 isTauTy, isTauTyCon, tcIsTyVarTy, tcIsForAllTy,
60 ---------------------------------
61 -- Misc type manipulators
62 deNoteType, classesOfTheta,
63 tyClsNamesOfType, tyClsNamesOfDFunHead,
66 ---------------------------------
68 getClassPredTys_maybe, getClassPredTys,
69 isClassPred, isTyVarClassPred, isEqPred,
70 mkDictTy, tcSplitPredTy_maybe,
71 isPredTy, isDictTy, tcSplitDFunTy, tcSplitDFunHead, predTyUnique,
72 mkClassPred, isInheritablePred, isIPPred, mkPredName,
73 dataConsStupidTheta, isRefineableTy,
75 ---------------------------------
76 -- Foreign import and export
77 isFFIArgumentTy, -- :: DynFlags -> Safety -> Type -> Bool
78 isFFIImportResultTy, -- :: DynFlags -> Type -> Bool
79 isFFIExportResultTy, -- :: Type -> Bool
80 isFFIExternalTy, -- :: Type -> Bool
81 isFFIDynArgumentTy, -- :: Type -> Bool
82 isFFIDynResultTy, -- :: Type -> Bool
83 isFFILabelTy, -- :: Type -> Bool
84 isFFIDotnetTy, -- :: DynFlags -> Type -> Bool
85 isFFIDotnetObjTy, -- :: Type -> Bool
86 isFFITy, -- :: Type -> Bool
87 tcSplitIOType_maybe, -- :: Type -> Maybe Type
88 toDNType, -- :: Type -> DNType
90 --------------------------------
91 -- Rexported from Type
92 Kind, -- Stuff to do with kinds is insensitive to pre/post Tc
93 unliftedTypeKind, liftedTypeKind, argTypeKind,
94 openTypeKind, mkArrowKind, mkArrowKinds,
95 isLiftedTypeKind, isUnliftedTypeKind, isSubOpenTypeKind,
96 isSubArgTypeKind, isSubKind, defaultKind,
97 kindVarRef, mkKindVar,
99 Type, PredType(..), ThetaType,
100 mkForAllTy, mkForAllTys,
101 mkFunTy, mkFunTys, zipFunTys,
102 mkTyConApp, mkAppTy, mkAppTys, applyTy, applyTys,
103 mkTyVarTy, mkTyVarTys, mkTyConTy, mkPredTy, mkPredTys,
105 -- Type substitutions
106 TvSubst(..), -- Representation visible to a few friends
107 TvSubstEnv, emptyTvSubst, substEqSpec,
108 mkOpenTvSubst, zipOpenTvSubst, zipTopTvSubst, mkTopTvSubst, notElemTvSubst,
109 getTvSubstEnv, setTvSubstEnv, getTvInScope, extendTvInScope, lookupTyVar,
110 extendTvSubst, extendTvSubstList, isInScope, mkTvSubst, zipTyEnv,
111 substTy, substTys, substTyWith, substTheta, substTyVar, substTyVarBndr,
113 isUnLiftedType, -- Source types are always lifted
114 isUnboxedTupleType, -- Ditto
117 tidyTopType, tidyType, tidyPred, tidyTypes, tidyFreeTyVars, tidyOpenType, tidyOpenTypes,
118 tidyTyVarBndr, tidyOpenTyVar, tidyOpenTyVars, tidySkolemTyVar,
121 tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tyVarsOfTheta,
122 tcTyVarsOfType, tcTyVarsOfTypes, exactTyVarsOfType, exactTyVarsOfTypes,
124 pprKind, pprParendKind,
125 pprType, pprParendType, pprTyThingCategory,
126 pprPred, pprTheta, pprThetaArrow, pprClassPred
130 #include "HsVersions.h"
163 %************************************************************************
167 %************************************************************************
169 The type checker divides the generic Type world into the
170 following more structured beasts:
172 sigma ::= forall tyvars. phi
173 -- A sigma type is a qualified type
175 -- Note that even if 'tyvars' is empty, theta
176 -- may not be: e.g. (?x::Int) => Int
178 -- Note that 'sigma' is in prenex form:
179 -- all the foralls are at the front.
180 -- A 'phi' type has no foralls to the right of
188 -- A 'tau' type has no quantification anywhere
189 -- Note that the args of a type constructor must be taus
191 | tycon tau_1 .. tau_n
195 -- In all cases, a (saturated) type synonym application is legal,
196 -- provided it expands to the required form.
199 type TcTyVar = TyVar -- Used only during type inference
200 type TcType = Type -- A TcType can have mutable type variables
201 -- Invariant on ForAllTy in TcTypes:
203 -- a cannot occur inside a MutTyVar in T; that is,
204 -- T is "flattened" before quantifying over a
206 -- These types do not have boxy type variables in them
207 type TcPredType = PredType
208 type TcThetaType = ThetaType
209 type TcSigmaType = TcType
210 type TcRhoType = TcType
211 type TcTauType = TcType
213 type TcTyVarSet = TyVarSet
215 -- These types may have boxy type variables in them
216 type BoxyTyVar = TcTyVar
217 type BoxyRhoType = TcType
218 type BoxyThetaType = TcThetaType
219 type BoxySigmaType = TcType
220 type BoxyType = TcType
224 %************************************************************************
226 \subsection{TyVarDetails}
228 %************************************************************************
230 TyVarDetails gives extra info about type variables, used during type
231 checking. It's attached to mutable type variables only.
232 It's knot-tied back to Var.lhs. There is no reason in principle
233 why Var.lhs shouldn't actually have the definition, but it "belongs" here.
236 Note [Signature skolems]
237 ~~~~~~~~~~~~~~~~~~~~~~~~
242 (x,y,z) = ([y,z], z, head x)
244 Here, x and y have type sigs, which go into the environment. We used to
245 instantiate their types with skolem constants, and push those types into
246 the RHS, so we'd typecheck the RHS with type
248 where a*, b* are skolem constants, and c is an ordinary meta type varible.
250 The trouble is that the occurrences of z in the RHS force a* and b* to
251 be the *same*, so we can't make them into skolem constants that don't unify
252 with each other. Alas.
254 One solution would be insist that in the above defn the programmer uses
255 the same type variable in both type signatures. But that takes explanation.
257 The alternative (currently implemented) is to have a special kind of skolem
258 constant, SigTv, which can unify with other SigTvs. These are *not* treated
259 as righd for the purposes of GADTs. And they are used *only* for pattern
260 bindings and mutually recursive function bindings. See the function
261 TcBinds.tcInstSig, and its use_skols parameter.
265 -- A TyVarDetails is inside a TyVar
267 = SkolemTv SkolemInfo -- A skolem constant
269 | MetaTv BoxInfo (IORef MetaDetails)
272 = BoxTv -- The contents is a (non-boxy) sigma-type
273 -- That is, this MetaTv is a "box"
275 | TauTv -- The contents is a (non-boxy) tau-type
276 -- That is, this MetaTv is an ordinary unification variable
278 | SigTv SkolemInfo -- A variant of TauTv, except that it should not be
279 -- unified with a type, only with a type variable
280 -- SigTvs are only distinguished to improve error messages
281 -- see Note [Signature skolems]
282 -- The MetaDetails, if filled in, will
283 -- always be another SigTv or a SkolemTv
286 -- A TauTv is always filled in with a tau-type, which
287 -- never contains any BoxTvs, nor any ForAlls
289 -- However, a BoxTv can contain a type that contains further BoxTvs
290 -- Notably, when typechecking an explicit list, say [e1,e2], with
291 -- expected type being a box b1, we fill in b1 with (List b2), where
292 -- b2 is another (currently empty) box.
295 = Flexi -- Flexi type variables unify to become
298 | Indirect TcType -- INVARIANT:
299 -- For a BoxTv, this type must be non-boxy
300 -- For a TauTv, this type must be a tau-type
303 = SigSkol UserTypeCtxt -- A skolem that is created by instantiating
304 -- a programmer-supplied type signature
305 -- Location of the binding site is on the TyVar
307 -- The rest are for non-scoped skolems
308 | ClsSkol Class -- Bound at a class decl
309 | InstSkol Id -- Bound at an instance decl
310 | FamInstSkol TyCon -- Bound at a family instance decl
311 | PatSkol DataCon -- An existential type variable bound by a pattern for
312 SrcSpan -- a data constructor with an existential type. E.g.
313 -- data T = forall a. Eq a => MkT a
315 -- The pattern MkT x will allocate an existential type
317 | ArrowSkol SrcSpan -- An arrow form (see TcArrows)
319 | GenSkol [TcTyVar] -- Bound when doing a subsumption check for
320 TcType -- (forall tvs. ty)
323 | UnkSkol -- Unhelpful info (until I improve it)
325 -------------------------------------
326 -- UserTypeCtxt describes the places where a
327 -- programmer-written type signature can occur
329 = FunSigCtxt Name -- Function type signature
330 -- Also used for types in SPECIALISE pragmas
331 | ExprSigCtxt -- Expression type signature
332 | ConArgCtxt Name -- Data constructor argument
333 | TySynCtxt Name -- RHS of a type synonym decl
334 | GenPatCtxt -- Pattern in generic decl
335 -- f{| a+b |} (Inl x) = ...
336 | LamPatSigCtxt -- Type sig in lambda pattern
338 | BindPatSigCtxt -- Type sig in pattern binding pattern
340 | ResSigCtxt -- Result type sig
342 | ForSigCtxt Name -- Foreign inport or export signature
343 | RuleSigCtxt Name -- Signature on a forall'd variable in a RULE
344 | DefaultDeclCtxt -- Types in a default declaration
345 | SpecInstCtxt -- SPECIALISE instance pragma
347 -- Notes re TySynCtxt
348 -- We allow type synonyms that aren't types; e.g. type List = []
350 -- If the RHS mentions tyvars that aren't in scope, we'll
351 -- quantify over them:
352 -- e.g. type T = a->a
353 -- will become type T = forall a. a->a
355 -- With gla-exts that's right, but for H98 we should complain.
357 ---------------------------------
360 mkKindName :: Unique -> Name
361 mkKindName unique = mkSystemName unique kind_var_occ
363 kindVarRef :: KindVar -> IORef MetaDetails
365 ASSERT ( isTcTyVar tc )
366 case tcTyVarDetails tc of
367 MetaTv TauTv ref -> ref
368 other -> pprPanic "kindVarRef" (ppr tc)
370 mkKindVar :: Unique -> IORef MetaDetails -> KindVar
372 = mkTcTyVar (mkKindName u)
373 tySuperKind -- not sure this is right,
374 -- do we need kind vars for
378 kind_var_occ :: OccName -- Just one for all KindVars
379 -- They may be jiggled by tidying
380 kind_var_occ = mkOccName tvName "k"
384 %************************************************************************
388 %************************************************************************
391 pprTcTyVarDetails :: TcTyVarDetails -> SDoc
393 pprTcTyVarDetails (SkolemTv _) = ptext SLIT("sk")
394 pprTcTyVarDetails (MetaTv BoxTv _) = ptext SLIT("box")
395 pprTcTyVarDetails (MetaTv TauTv _) = ptext SLIT("tau")
396 pprTcTyVarDetails (MetaTv (SigTv _) _) = ptext SLIT("sig")
398 pprUserTypeCtxt :: UserTypeCtxt -> SDoc
399 pprUserTypeCtxt (FunSigCtxt n) = ptext SLIT("the type signature for") <+> quotes (ppr n)
400 pprUserTypeCtxt ExprSigCtxt = ptext SLIT("an expression type signature")
401 pprUserTypeCtxt (ConArgCtxt c) = ptext SLIT("the type of the constructor") <+> quotes (ppr c)
402 pprUserTypeCtxt (TySynCtxt c) = ptext SLIT("the RHS of the type synonym") <+> quotes (ppr c)
403 pprUserTypeCtxt GenPatCtxt = ptext SLIT("the type pattern of a generic definition")
404 pprUserTypeCtxt LamPatSigCtxt = ptext SLIT("a pattern type signature")
405 pprUserTypeCtxt BindPatSigCtxt = ptext SLIT("a pattern type signature")
406 pprUserTypeCtxt ResSigCtxt = ptext SLIT("a result type signature")
407 pprUserTypeCtxt (ForSigCtxt n) = ptext SLIT("the foreign declaration for") <+> quotes (ppr n)
408 pprUserTypeCtxt (RuleSigCtxt n) = ptext SLIT("the type signature for") <+> quotes (ppr n)
409 pprUserTypeCtxt DefaultDeclCtxt = ptext SLIT("a type in a `default' declaration")
410 pprUserTypeCtxt SpecInstCtxt = ptext SLIT("a SPECIALISE instance pragma")
413 --------------------------------
414 tidySkolemTyVar :: TidyEnv -> TcTyVar -> (TidyEnv, TcTyVar)
415 -- Tidy the type inside a GenSkol, preparatory to printing it
416 tidySkolemTyVar env tv
417 = ASSERT( isSkolemTyVar tv || isSigTyVar tv )
418 (env1, mkTcTyVar (tyVarName tv) (tyVarKind tv) info1)
420 (env1, info1) = case tcTyVarDetails tv of
421 SkolemTv info -> (env1, SkolemTv info')
423 (env1, info') = tidy_skol_info env info
424 MetaTv (SigTv info) box -> (env1, MetaTv (SigTv info') box)
426 (env1, info') = tidy_skol_info env info
429 tidy_skol_info env (GenSkol tvs ty loc) = (env2, GenSkol tvs1 ty1 loc)
431 (env1, tvs1) = tidyOpenTyVars env tvs
432 (env2, ty1) = tidyOpenType env1 ty
433 tidy_skol_info env info = (env, info)
435 pprSkolTvBinding :: TcTyVar -> SDoc
436 -- Print info about the binding of a skolem tyvar,
437 -- or nothing if we don't have anything useful to say
439 = ASSERT ( isTcTyVar tv )
440 ppr_details (tcTyVarDetails tv)
442 ppr_details (MetaTv TauTv _) = quotes (ppr tv) <+> ptext SLIT("is a meta type variable")
443 ppr_details (MetaTv BoxTv _) = quotes (ppr tv) <+> ptext SLIT("is a boxy type variable")
444 ppr_details (MetaTv (SigTv info) _) = ppr_skol info
445 ppr_details (SkolemTv info) = ppr_skol info
447 ppr_skol UnkSkol = empty -- Unhelpful; omit
448 ppr_skol (SigSkol ctxt) = sep [quotes (ppr tv) <+> ptext SLIT("is bound by") <+> pprUserTypeCtxt ctxt,
449 nest 2 (ptext SLIT("at") <+> ppr (getSrcLoc tv))]
450 ppr_skol info = quotes (ppr tv) <+> pprSkolInfo info
452 pprSkolInfo :: SkolemInfo -> SDoc
453 pprSkolInfo (SigSkol ctxt) = ptext SLIT("is bound by") <+> pprUserTypeCtxt ctxt
454 pprSkolInfo (ClsSkol cls) = ptext SLIT("is bound by the class declaration for") <+> quotes (ppr cls)
455 pprSkolInfo (InstSkol df) =
456 ptext SLIT("is bound by the instance declaration at") <+> ppr (getSrcLoc df)
457 pprSkolInfo (FamInstSkol tc) =
458 ptext SLIT("is bound by the family instance declaration at") <+>
460 pprSkolInfo (ArrowSkol loc) =
461 ptext SLIT("is bound by the arrow form at") <+> ppr loc
462 pprSkolInfo (PatSkol dc loc) = sep [ptext SLIT("is bound by the pattern for") <+> quotes (ppr dc),
463 nest 2 (ptext SLIT("at") <+> ppr loc)]
464 pprSkolInfo (GenSkol tvs ty loc) = sep [sep [ptext SLIT("is bound by the polymorphic type"),
465 nest 2 (quotes (ppr (mkForAllTys tvs ty)))],
466 nest 2 (ptext SLIT("at") <+> ppr loc)]
468 -- For type variables the others are dealt with by pprSkolTvBinding.
469 -- For Insts, these cases should not happen
470 pprSkolInfo UnkSkol = panic "UnkSkol"
472 instance Outputable MetaDetails where
473 ppr Flexi = ptext SLIT("Flexi")
474 ppr (Indirect ty) = ptext SLIT("Indirect") <+> ppr ty
478 %************************************************************************
482 %************************************************************************
485 isImmutableTyVar, isSkolemTyVar, isExistentialTyVar, isBoxyTyVar, isMetaTyVar :: TyVar -> Bool
487 | isTcTyVar tv = isSkolemTyVar tv
491 = ASSERT( isTcTyVar tv )
492 case tcTyVarDetails tv of
496 isExistentialTyVar tv -- Existential type variable, bound by a pattern
497 = ASSERT( isTcTyVar tv )
498 case tcTyVarDetails tv of
499 SkolemTv (PatSkol _ _) -> True
503 = ASSERT2( isTcTyVar tv, ppr tv )
504 case tcTyVarDetails tv of
509 = ASSERT( isTcTyVar tv )
510 case tcTyVarDetails tv of
511 MetaTv BoxTv _ -> True
515 = ASSERT( isTcTyVar tv )
516 case tcTyVarDetails tv of
517 MetaTv (SigTv _) _ -> True
520 metaTvRef :: TyVar -> IORef MetaDetails
522 = ASSERT( isTcTyVar tv )
523 case tcTyVarDetails tv of
525 other -> pprPanic "metaTvRef" (ppr tv)
527 isFlexi, isIndirect :: MetaDetails -> Bool
529 isFlexi other = False
531 isIndirect (Indirect _) = True
532 isIndirect other = False
536 %************************************************************************
538 \subsection{Tau, sigma and rho}
540 %************************************************************************
543 mkSigmaTy :: [TyVar] -> [PredType] -> Type -> Type
544 mkSigmaTy tyvars theta tau = mkForAllTys tyvars (mkPhiTy theta tau)
546 mkPhiTy :: [PredType] -> Type -> Type
547 mkPhiTy theta ty = foldr (\p r -> FunTy (mkPredTy p) r) ty theta
550 @isTauTy@ tests for nested for-alls. It should not be called on a boxy type.
553 isTauTy :: Type -> Bool
554 isTauTy ty | Just ty' <- tcView ty = isTauTy ty'
555 isTauTy (TyVarTy tv) = ASSERT( not (isTcTyVar tv && isBoxyTyVar tv) )
557 isTauTy (TyConApp tc tys) = all isTauTy tys && isTauTyCon tc
558 isTauTy (AppTy a b) = isTauTy a && isTauTy b
559 isTauTy (FunTy a b) = isTauTy a && isTauTy b
560 isTauTy (PredTy p) = True -- Don't look through source types
561 isTauTy other = False
564 isTauTyCon :: TyCon -> Bool
565 -- Returns False for type synonyms whose expansion is a polytype
567 | isSynTyCon tc && not (isOpenTyCon tc) = isTauTy (snd (synTyConDefn tc))
571 isBoxyTy :: TcType -> Bool
572 isBoxyTy ty = any isBoxyTyVar (varSetElems (tcTyVarsOfType ty))
574 isRigidTy :: TcType -> Bool
575 -- A type is rigid if it has no meta type variables in it
576 isRigidTy ty = all isSkolemTyVar (varSetElems (tcTyVarsOfType ty))
578 isRefineableTy :: TcType -> Bool
579 -- A type should have type refinements applied to it if it has
580 -- free type variables, and they are all rigid
581 isRefineableTy ty = not (null tc_tvs) && all isSkolemTyVar tc_tvs
583 tc_tvs = varSetElems (tcTyVarsOfType ty)
586 getDFunTyKey :: Type -> OccName -- Get some string from a type, to be used to
587 -- construct a dictionary function name
588 getDFunTyKey ty | Just ty' <- tcView ty = getDFunTyKey ty'
589 getDFunTyKey (TyVarTy tv) = getOccName tv
590 getDFunTyKey (TyConApp tc _) = getOccName tc
591 getDFunTyKey (AppTy fun _) = getDFunTyKey fun
592 getDFunTyKey (FunTy arg _) = getOccName funTyCon
593 getDFunTyKey (ForAllTy _ t) = getDFunTyKey t
594 getDFunTyKey ty = pprPanic "getDFunTyKey" (pprType ty)
595 -- PredTy shouldn't happen
599 %************************************************************************
601 \subsection{Expanding and splitting}
603 %************************************************************************
605 These tcSplit functions are like their non-Tc analogues, but
606 a) they do not look through newtypes
607 b) they do not look through PredTys
608 c) [future] they ignore usage-type annotations
610 However, they are non-monadic and do not follow through mutable type
611 variables. It's up to you to make sure this doesn't matter.
614 tcSplitForAllTys :: Type -> ([TyVar], Type)
615 tcSplitForAllTys ty = split ty ty []
617 split orig_ty ty tvs | Just ty' <- tcView ty = split orig_ty ty' tvs
618 split orig_ty (ForAllTy tv ty) tvs
619 | not (isCoVar tv) = split ty ty (tv:tvs)
620 split orig_ty t tvs = (reverse tvs, orig_ty)
622 tcIsForAllTy ty | Just ty' <- tcView ty = tcIsForAllTy ty'
623 tcIsForAllTy (ForAllTy tv ty) = not (isCoVar tv)
624 tcIsForAllTy t = False
626 tcSplitPhiTy :: Type -> (ThetaType, Type)
627 tcSplitPhiTy ty = split ty ty []
629 split orig_ty ty tvs | Just ty' <- tcView ty = split orig_ty ty' tvs
631 split orig_ty (ForAllTy tv ty) ts
632 | isCoVar tv = split ty ty (eq_pred:ts)
634 PredTy eq_pred = tyVarKind tv
635 split orig_ty (FunTy arg res) ts
636 | Just p <- tcSplitPredTy_maybe arg = split res res (p:ts)
637 split orig_ty ty ts = (reverse ts, orig_ty)
639 tcSplitSigmaTy :: Type -> ([TyVar], ThetaType, Type)
640 tcSplitSigmaTy ty = case tcSplitForAllTys ty of
641 (tvs, rho) -> case tcSplitPhiTy rho of
642 (theta, tau) -> (tvs, theta, tau)
644 -----------------------
647 -> ( [([TyVar], ThetaType)], -- forall as.C => forall bs.D
648 TcSigmaType) -- The rest of the type
650 -- We need a loop here because we are now prepared to entertain
652 -- f:: forall a. Eq a => forall b. Baz b => tau
653 -- We want to instantiate this to
654 -- f2::tau {f2 = f1 b (Baz b), f1 = f a (Eq a)}
656 tcMultiSplitSigmaTy sigma
657 = case (tcSplitSigmaTy sigma) of
658 ([],[],ty) -> ([], sigma)
659 (tvs, theta, ty) -> case tcMultiSplitSigmaTy ty of
660 (pairs, rest) -> ((tvs,theta):pairs, rest)
662 -----------------------
663 tcTyConAppTyCon :: Type -> TyCon
664 tcTyConAppTyCon ty = case tcSplitTyConApp_maybe ty of
666 Nothing -> pprPanic "tcTyConAppTyCon" (pprType ty)
668 tcTyConAppArgs :: Type -> [Type]
669 tcTyConAppArgs ty = case tcSplitTyConApp_maybe ty of
670 Just (_, args) -> args
671 Nothing -> pprPanic "tcTyConAppArgs" (pprType ty)
673 tcSplitTyConApp :: Type -> (TyCon, [Type])
674 tcSplitTyConApp ty = case tcSplitTyConApp_maybe ty of
676 Nothing -> pprPanic "tcSplitTyConApp" (pprType ty)
678 tcSplitTyConApp_maybe :: Type -> Maybe (TyCon, [Type])
679 tcSplitTyConApp_maybe ty | Just ty' <- tcView ty = tcSplitTyConApp_maybe ty'
680 tcSplitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
681 tcSplitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res])
682 -- Newtypes are opaque, so they may be split
683 -- However, predicates are not treated
684 -- as tycon applications by the type checker
685 tcSplitTyConApp_maybe other = Nothing
687 -----------------------
688 tcSplitFunTys :: Type -> ([Type], Type)
689 tcSplitFunTys ty = case tcSplitFunTy_maybe ty of
691 Just (arg,res) -> (arg:args, res')
693 (args,res') = tcSplitFunTys res
695 tcSplitFunTy_maybe :: Type -> Maybe (Type, Type)
696 tcSplitFunTy_maybe ty | Just ty' <- tcView ty = tcSplitFunTy_maybe ty'
697 tcSplitFunTy_maybe (FunTy arg res) = Just (arg, res)
698 tcSplitFunTy_maybe other = Nothing
702 -> Arity -- N: Number of desired args
703 -> ([TcSigmaType], -- Arg types (N or fewer)
704 TcSigmaType) -- The rest of the type
706 tcSplitFunTysN ty n_args
709 | Just (arg,res) <- tcSplitFunTy_maybe ty
710 = case tcSplitFunTysN res (n_args - 1) of
711 (args, res) -> (arg:args, res)
715 tcSplitFunTy ty = expectJust "tcSplitFunTy" (tcSplitFunTy_maybe ty)
716 tcFunArgTy ty = fst (tcSplitFunTy ty)
717 tcFunResultTy ty = snd (tcSplitFunTy ty)
719 -----------------------
720 tcSplitAppTy_maybe :: Type -> Maybe (Type, Type)
721 tcSplitAppTy_maybe ty | Just ty' <- tcView ty = tcSplitAppTy_maybe ty'
722 tcSplitAppTy_maybe ty = repSplitAppTy_maybe ty
724 tcSplitAppTy :: Type -> (Type, Type)
725 tcSplitAppTy ty = case tcSplitAppTy_maybe ty of
727 Nothing -> pprPanic "tcSplitAppTy" (pprType ty)
729 tcSplitAppTys :: Type -> (Type, [Type])
733 go ty args = case tcSplitAppTy_maybe ty of
734 Just (ty', arg) -> go ty' (arg:args)
737 -----------------------
738 tcGetTyVar_maybe :: Type -> Maybe TyVar
739 tcGetTyVar_maybe ty | Just ty' <- tcView ty = tcGetTyVar_maybe ty'
740 tcGetTyVar_maybe (TyVarTy tv) = Just tv
741 tcGetTyVar_maybe other = Nothing
743 tcGetTyVar :: String -> Type -> TyVar
744 tcGetTyVar msg ty = expectJust msg (tcGetTyVar_maybe ty)
746 tcIsTyVarTy :: Type -> Bool
747 tcIsTyVarTy ty = maybeToBool (tcGetTyVar_maybe ty)
749 -----------------------
750 tcSplitDFunTy :: Type -> ([TyVar], [PredType], Class, [Type])
751 -- Split the type of a dictionary function
753 = case tcSplitSigmaTy ty of { (tvs, theta, tau) ->
754 case tcSplitDFunHead tau of { (clas, tys) ->
755 (tvs, theta, clas, tys) }}
757 tcSplitDFunHead :: Type -> (Class, [Type])
759 = case tcSplitPredTy_maybe tau of
760 Just (ClassP clas tys) -> (clas, tys)
761 other -> panic "tcSplitDFunHead"
763 tcValidInstHeadTy :: Type -> Bool
764 -- Used in Haskell-98 mode, for the argument types of an instance head
765 -- These must not be type synonyms, but everywhere else type synonyms
766 -- are transparent, so we need a special function here
769 NoteTy _ ty -> tcValidInstHeadTy ty
770 TyConApp tc tys -> not (isSynTyCon tc) && ok tys
771 FunTy arg res -> ok [arg, res]
774 -- Check that all the types are type variables,
775 -- and that each is distinct
776 ok tys = equalLength tvs tys && hasNoDups tvs
778 tvs = mapCatMaybes get_tv tys
780 get_tv (NoteTy _ ty) = get_tv ty -- Again, do not look
781 get_tv (TyVarTy tv) = Just tv -- through synonyms
782 get_tv other = Nothing
787 %************************************************************************
789 \subsection{Predicate types}
791 %************************************************************************
794 tcSplitPredTy_maybe :: Type -> Maybe PredType
795 -- Returns Just for predicates only
796 tcSplitPredTy_maybe ty | Just ty' <- tcView ty = tcSplitPredTy_maybe ty'
797 tcSplitPredTy_maybe (PredTy p) = Just p
798 tcSplitPredTy_maybe other = Nothing
800 predTyUnique :: PredType -> Unique
801 predTyUnique (IParam n _) = getUnique (ipNameName n)
802 predTyUnique (ClassP clas tys) = getUnique clas
804 mkPredName :: Unique -> SrcLoc -> PredType -> Name
805 mkPredName uniq loc (ClassP cls tys) = mkInternalName uniq (mkDictOcc (getOccName cls)) loc
806 mkPredName uniq loc (IParam ip ty) = mkInternalName uniq (getOccName (ipNameName ip)) loc
810 --------------------- Dictionary types ---------------------------------
813 mkClassPred clas tys = ClassP clas tys
815 isClassPred :: PredType -> Bool
816 isClassPred (ClassP clas tys) = True
817 isClassPred other = False
819 isTyVarClassPred (ClassP clas tys) = all tcIsTyVarTy tys
820 isTyVarClassPred other = False
822 getClassPredTys_maybe :: PredType -> Maybe (Class, [Type])
823 getClassPredTys_maybe (ClassP clas tys) = Just (clas, tys)
824 getClassPredTys_maybe _ = Nothing
826 getClassPredTys :: PredType -> (Class, [Type])
827 getClassPredTys (ClassP clas tys) = (clas, tys)
828 getClassPredTys other = panic "getClassPredTys"
830 mkDictTy :: Class -> [Type] -> Type
831 mkDictTy clas tys = mkPredTy (ClassP clas tys)
833 isDictTy :: Type -> Bool
834 isDictTy ty | Just ty' <- tcView ty = isDictTy ty'
835 isDictTy (PredTy p) = isClassPred p
836 isDictTy other = False
839 --------------------- Implicit parameters ---------------------------------
842 isIPPred :: PredType -> Bool
843 isIPPred (IParam _ _) = True
844 isIPPred other = False
846 isInheritablePred :: PredType -> Bool
847 -- Can be inherited by a context. For example, consider
848 -- f x = let g y = (?v, y+x)
849 -- in (g 3 with ?v = 8,
851 -- The point is that g's type must be quantifed over ?v:
852 -- g :: (?v :: a) => a -> a
853 -- but it doesn't need to be quantified over the Num a dictionary
854 -- which can be free in g's rhs, and shared by both calls to g
855 isInheritablePred (ClassP _ _) = True
856 isInheritablePred other = False
859 --------------------- Equality predicates ---------------------------------
861 substEqSpec :: TvSubst -> [(TyVar,Type)] -> [(TcType,TcType)]
862 substEqSpec subst eq_spec = [ (substTyVar subst tv, substTy subst ty)
863 | (tv,ty) <- eq_spec]
866 --------------------- The stupid theta (sigh) ---------------------------------
869 dataConsStupidTheta :: [DataCon] -> ThetaType
870 -- Union the stupid thetas from all the specified constructors (non-empty)
871 -- All the constructors should have the same result type, modulo alpha conversion
872 -- The resulting ThetaType uses type variables from the *first* constructor in the list
874 -- It's here because it's used in MkId.mkRecordSelId, and in TcExpr
875 dataConsStupidTheta (con1:cons)
876 = nubBy tcEqPred all_preds
878 all_preds = dataConStupidTheta con1 ++ other_stupids
879 res_tys1 = dataConResTys con1
880 tvs1 = tyVarsOfTypes res_tys1
881 other_stupids = [ substPred subst pred
883 , let Just subst = tcMatchTys tvs1 res_tys1 (dataConResTys con)
884 , pred <- dataConStupidTheta con ]
885 dataConsStupidTheta [] = panic "dataConsStupidTheta"
889 %************************************************************************
891 \subsection{Predicates}
893 %************************************************************************
895 isSigmaTy returns true of any qualified type. It doesn't *necessarily* have
897 f :: (?x::Int) => Int -> Int
900 isSigmaTy :: Type -> Bool
901 isSigmaTy ty | Just ty' <- tcView ty = isSigmaTy ty'
902 isSigmaTy (ForAllTy tyvar ty) = True
903 isSigmaTy (FunTy a b) = isPredTy a
906 isOverloadedTy :: Type -> Bool
907 isOverloadedTy ty | Just ty' <- tcView ty = isOverloadedTy ty'
908 isOverloadedTy (ForAllTy tyvar ty) = isOverloadedTy ty
909 isOverloadedTy (FunTy a b) = isPredTy a
910 isOverloadedTy _ = False
912 isPredTy :: Type -> Bool -- Belongs in TcType because it does
913 -- not look through newtypes, or predtypes (of course)
914 isPredTy ty | Just ty' <- tcView ty = isPredTy ty'
915 isPredTy (PredTy sty) = True
920 isFloatTy = is_tc floatTyConKey
921 isDoubleTy = is_tc doubleTyConKey
922 isIntegerTy = is_tc integerTyConKey
923 isIntTy = is_tc intTyConKey
924 isBoolTy = is_tc boolTyConKey
925 isUnitTy = is_tc unitTyConKey
927 is_tc :: Unique -> Type -> Bool
928 -- Newtypes are opaque to this
929 is_tc uniq ty = case tcSplitTyConApp_maybe ty of
930 Just (tc, _) -> uniq == getUnique tc
935 %************************************************************************
939 %************************************************************************
942 deNoteType :: Type -> Type
943 -- Remove all *outermost* type synonyms and other notes
944 deNoteType ty | Just ty' <- tcView ty = deNoteType ty'
949 tcTyVarsOfType :: Type -> TcTyVarSet
950 -- Just the *TcTyVars* free in the type
951 -- (Types.tyVarsOfTypes finds all free TyVars)
952 tcTyVarsOfType (TyVarTy tv) = if isTcTyVar tv then unitVarSet tv
954 tcTyVarsOfType (TyConApp tycon tys) = tcTyVarsOfTypes tys
955 tcTyVarsOfType (NoteTy _ ty) = tcTyVarsOfType ty
956 tcTyVarsOfType (PredTy sty) = tcTyVarsOfPred sty
957 tcTyVarsOfType (FunTy arg res) = tcTyVarsOfType arg `unionVarSet` tcTyVarsOfType res
958 tcTyVarsOfType (AppTy fun arg) = tcTyVarsOfType fun `unionVarSet` tcTyVarsOfType arg
959 tcTyVarsOfType (ForAllTy tyvar ty) = (tcTyVarsOfType ty `delVarSet` tyvar)
960 `unionVarSet` tcTyVarsOfTyVar tyvar
961 -- We do sometimes quantify over skolem TcTyVars
963 tcTyVarsOfTyVar :: TcTyVar -> TyVarSet
964 tcTyVarsOfTyVar tv | isCoVar tv = tcTyVarsOfType (tyVarKind tv)
965 | otherwise = emptyVarSet
967 tcTyVarsOfTypes :: [Type] -> TyVarSet
968 tcTyVarsOfTypes tys = foldr (unionVarSet.tcTyVarsOfType) emptyVarSet tys
970 tcTyVarsOfPred :: PredType -> TyVarSet
971 tcTyVarsOfPred (IParam _ ty) = tcTyVarsOfType ty
972 tcTyVarsOfPred (ClassP _ tys) = tcTyVarsOfTypes tys
973 tcTyVarsOfPred (EqPred ty1 ty2) = tcTyVarsOfType ty1 `unionVarSet` tcTyVarsOfType ty2
976 Note [Silly type synonym]
977 ~~~~~~~~~~~~~~~~~~~~~~~~~
980 What are the free tyvars of (T x)? Empty, of course!
981 Here's the example that Ralf Laemmel showed me:
982 foo :: (forall a. C u a -> C u a) -> u
983 mappend :: Monoid u => u -> u -> u
986 bar = foo (\t -> t `mappend` t)
987 We have to generalise at the arg to f, and we don't
988 want to capture the constraint (Monad (C u a)) because
989 it appears to mention a. Pretty silly, but it was useful to him.
991 exactTyVarsOfType is used by the type checker to figure out exactly
992 which type variables are mentioned in a type. It's also used in the
993 smart-app checking code --- see TcExpr.tcIdApp
996 exactTyVarsOfType :: TcType -> TyVarSet
997 -- Find the free type variables (of any kind)
998 -- but *expand* type synonyms. See Note [Silly type synonym] above.
1002 go ty | Just ty' <- tcView ty = go ty' -- This is the key line
1003 go (TyVarTy tv) = unitVarSet tv
1004 go (TyConApp tycon tys) = exactTyVarsOfTypes tys
1005 go (PredTy ty) = go_pred ty
1006 go (FunTy arg res) = go arg `unionVarSet` go res
1007 go (AppTy fun arg) = go fun `unionVarSet` go arg
1008 go (ForAllTy tyvar ty) = delVarSet (go ty) tyvar
1009 `unionVarSet` go_tv tyvar
1011 go_pred (IParam _ ty) = go ty
1012 go_pred (ClassP _ tys) = exactTyVarsOfTypes tys
1013 go_pred (EqPred ty1 ty2) = go ty1 `unionVarSet` go ty2
1015 go_tv tyvar | isCoVar tyvar = go (tyVarKind tyvar)
1016 | otherwise = emptyVarSet
1018 exactTyVarsOfTypes :: [TcType] -> TyVarSet
1019 exactTyVarsOfTypes tys = foldr (unionVarSet . exactTyVarsOfType) emptyVarSet tys
1022 Find the free tycons and classes of a type. This is used in the front
1023 end of the compiler.
1026 tyClsNamesOfType :: Type -> NameSet
1027 tyClsNamesOfType (TyVarTy tv) = emptyNameSet
1028 tyClsNamesOfType (TyConApp tycon tys) = unitNameSet (getName tycon) `unionNameSets` tyClsNamesOfTypes tys
1029 tyClsNamesOfType (NoteTy _ ty2) = tyClsNamesOfType ty2
1030 tyClsNamesOfType (PredTy (IParam n ty)) = tyClsNamesOfType ty
1031 tyClsNamesOfType (PredTy (ClassP cl tys)) = unitNameSet (getName cl) `unionNameSets` tyClsNamesOfTypes tys
1032 tyClsNamesOfType (PredTy (EqPred ty1 ty2)) = tyClsNamesOfType ty1 `unionNameSets` tyClsNamesOfType ty2
1033 tyClsNamesOfType (FunTy arg res) = tyClsNamesOfType arg `unionNameSets` tyClsNamesOfType res
1034 tyClsNamesOfType (AppTy fun arg) = tyClsNamesOfType fun `unionNameSets` tyClsNamesOfType arg
1035 tyClsNamesOfType (ForAllTy tyvar ty) = tyClsNamesOfType ty
1037 tyClsNamesOfTypes tys = foldr (unionNameSets . tyClsNamesOfType) emptyNameSet tys
1039 tyClsNamesOfDFunHead :: Type -> NameSet
1040 -- Find the free type constructors and classes
1041 -- of the head of the dfun instance type
1042 -- The 'dfun_head_type' is because of
1043 -- instance Foo a => Baz T where ...
1044 -- The decl is an orphan if Baz and T are both not locally defined,
1045 -- even if Foo *is* locally defined
1046 tyClsNamesOfDFunHead dfun_ty
1047 = case tcSplitSigmaTy dfun_ty of
1048 (tvs,_,head_ty) -> tyClsNamesOfType head_ty
1050 classesOfTheta :: ThetaType -> [Class]
1051 -- Looks just for ClassP things; maybe it should check
1052 classesOfTheta preds = [ c | ClassP c _ <- preds ]
1056 %************************************************************************
1058 \subsection[TysWiredIn-ext-type]{External types}
1060 %************************************************************************
1062 The compiler's foreign function interface supports the passing of a
1063 restricted set of types as arguments and results (the restricting factor
1067 tcSplitIOType_maybe :: Type -> Maybe (TyCon, Type)
1068 -- (isIOType t) returns (Just (IO,t')) if t is of the form (IO t'), or
1069 -- some newtype wrapping thereof
1070 -- returns Nothing otherwise
1071 tcSplitIOType_maybe ty
1072 | Just (io_tycon, [io_res_ty]) <- tcSplitTyConApp_maybe ty,
1073 -- This split absolutely has to be a tcSplit, because we must
1074 -- see the IO type; and it's a newtype which is transparent to splitTyConApp.
1075 io_tycon `hasKey` ioTyConKey
1076 = Just (io_tycon, io_res_ty)
1078 | Just ty' <- coreView ty -- Look through non-recursive newtypes
1079 = tcSplitIOType_maybe ty'
1084 isFFITy :: Type -> Bool
1085 -- True for any TyCon that can possibly be an arg or result of an FFI call
1086 isFFITy ty = checkRepTyCon legalFFITyCon ty
1088 isFFIArgumentTy :: DynFlags -> Safety -> Type -> Bool
1089 -- Checks for valid argument type for a 'foreign import'
1090 isFFIArgumentTy dflags safety ty
1091 = checkRepTyCon (legalOutgoingTyCon dflags safety) ty
1093 isFFIExternalTy :: Type -> Bool
1094 -- Types that are allowed as arguments of a 'foreign export'
1095 isFFIExternalTy ty = checkRepTyCon legalFEArgTyCon ty
1097 isFFIImportResultTy :: DynFlags -> Type -> Bool
1098 isFFIImportResultTy dflags ty
1099 = checkRepTyCon (legalFIResultTyCon dflags) ty
1101 isFFIExportResultTy :: Type -> Bool
1102 isFFIExportResultTy ty = checkRepTyCon legalFEResultTyCon ty
1104 isFFIDynArgumentTy :: Type -> Bool
1105 -- The argument type of a foreign import dynamic must be Ptr, FunPtr, Addr,
1106 -- or a newtype of either.
1107 isFFIDynArgumentTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1109 isFFIDynResultTy :: Type -> Bool
1110 -- The result type of a foreign export dynamic must be Ptr, FunPtr, Addr,
1111 -- or a newtype of either.
1112 isFFIDynResultTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1114 isFFILabelTy :: Type -> Bool
1115 -- The type of a foreign label must be Ptr, FunPtr, Addr,
1116 -- or a newtype of either.
1117 isFFILabelTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1119 isFFIDotnetTy :: DynFlags -> Type -> Bool
1120 isFFIDotnetTy dflags ty
1121 = checkRepTyCon (\ tc -> (legalFIResultTyCon dflags tc ||
1122 isFFIDotnetObjTy ty || isStringTy ty)) ty
1124 -- Support String as an argument or result from a .NET FFI call.
1126 case tcSplitTyConApp_maybe (repType ty) of
1128 | tc == listTyCon ->
1129 case tcSplitTyConApp_maybe (repType arg_ty) of
1130 Just (cc,[]) -> cc == charTyCon
1134 -- Support String as an argument or result from a .NET FFI call.
1135 isFFIDotnetObjTy ty =
1137 (_, t_ty) = tcSplitForAllTys ty
1139 case tcSplitTyConApp_maybe (repType t_ty) of
1140 Just (tc, [arg_ty]) | getName tc == objectTyConName -> True
1143 toDNType :: Type -> DNType
1145 | isStringTy ty = DNString
1146 | isFFIDotnetObjTy ty = DNObject
1147 | Just (tc,argTys) <- tcSplitTyConApp_maybe ty
1148 = case lookup (getUnique tc) dn_assoc of
1151 | tc `hasKey` ioTyConKey -> toDNType (head argTys)
1152 | otherwise -> pprPanic ("toDNType: unsupported .NET type")
1153 (pprType ty <+> parens (hcat (map pprType argTys)) <+> ppr tc)
1154 | otherwise = panic "toDNType" -- Is this right?
1156 dn_assoc :: [ (Unique, DNType) ]
1157 dn_assoc = [ (unitTyConKey, DNUnit)
1158 , (intTyConKey, DNInt)
1159 , (int8TyConKey, DNInt8)
1160 , (int16TyConKey, DNInt16)
1161 , (int32TyConKey, DNInt32)
1162 , (int64TyConKey, DNInt64)
1163 , (wordTyConKey, DNInt)
1164 , (word8TyConKey, DNWord8)
1165 , (word16TyConKey, DNWord16)
1166 , (word32TyConKey, DNWord32)
1167 , (word64TyConKey, DNWord64)
1168 , (floatTyConKey, DNFloat)
1169 , (doubleTyConKey, DNDouble)
1170 , (ptrTyConKey, DNPtr)
1171 , (funPtrTyConKey, DNPtr)
1172 , (charTyConKey, DNChar)
1173 , (boolTyConKey, DNBool)
1176 checkRepTyCon :: (TyCon -> Bool) -> Type -> Bool
1177 -- Look through newtypes
1178 -- Non-recursive ones are transparent to splitTyConApp,
1179 -- but recursive ones aren't. Manuel had:
1180 -- newtype T = MkT (Ptr T)
1181 -- and wanted it to work...
1182 checkRepTyCon check_tc ty
1183 | Just (tc,_) <- splitTyConApp_maybe (repType ty) = check_tc tc
1186 checkRepTyConKey :: [Unique] -> Type -> Bool
1187 -- Like checkRepTyCon, but just looks at the TyCon key
1188 checkRepTyConKey keys
1189 = checkRepTyCon (\tc -> tyConUnique tc `elem` keys)
1192 ----------------------------------------------
1193 These chaps do the work; they are not exported
1194 ----------------------------------------------
1197 legalFEArgTyCon :: TyCon -> Bool
1199 -- It's illegal to make foreign exports that take unboxed
1200 -- arguments. The RTS API currently can't invoke such things. --SDM 7/2000
1201 = boxedMarshalableTyCon tc
1203 legalFIResultTyCon :: DynFlags -> TyCon -> Bool
1204 legalFIResultTyCon dflags tc
1205 | tc == unitTyCon = True
1206 | otherwise = marshalableTyCon dflags tc
1208 legalFEResultTyCon :: TyCon -> Bool
1209 legalFEResultTyCon tc
1210 | tc == unitTyCon = True
1211 | otherwise = boxedMarshalableTyCon tc
1213 legalOutgoingTyCon :: DynFlags -> Safety -> TyCon -> Bool
1214 -- Checks validity of types going from Haskell -> external world
1215 legalOutgoingTyCon dflags safety tc
1216 = marshalableTyCon dflags tc
1218 legalFFITyCon :: TyCon -> Bool
1219 -- True for any TyCon that can possibly be an arg or result of an FFI call
1221 = isUnLiftedTyCon tc || boxedMarshalableTyCon tc || tc == unitTyCon
1223 marshalableTyCon dflags tc
1224 = (dopt Opt_GlasgowExts dflags && isUnLiftedTyCon tc)
1225 || boxedMarshalableTyCon tc
1227 boxedMarshalableTyCon tc
1228 = getUnique tc `elem` [ intTyConKey, int8TyConKey, int16TyConKey
1229 , int32TyConKey, int64TyConKey
1230 , wordTyConKey, word8TyConKey, word16TyConKey
1231 , word32TyConKey, word64TyConKey
1232 , floatTyConKey, doubleTyConKey
1233 , ptrTyConKey, funPtrTyConKey