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 tcInstHeadTyNotSynonym, tcInstHeadTyAppAllTyVars,
49 tcGetTyVar_maybe, tcGetTyVar,
50 tcSplitSigmaTy, tcMultiSplitSigmaTy,
52 ---------------------------------
54 -- Again, newtypes are opaque
55 tcEqType, tcEqTypes, tcEqPred, tcCmpType, tcCmpTypes, tcCmpPred, tcEqTypeX,
57 isSigmaTy, isOverloadedTy, isRigidTy, isBoxyTy,
58 isDoubleTy, isFloatTy, isIntTy, isStringTy,
59 isIntegerTy, isBoolTy, isUnitTy, isCharTy,
60 isTauTy, isTauTyCon, tcIsTyVarTy, tcIsForAllTy,
62 ---------------------------------
63 -- Misc type manipulators
65 tyClsNamesOfType, tyClsNamesOfDFunHead,
68 ---------------------------------
70 getClassPredTys_maybe, getClassPredTys,
71 isClassPred, isTyVarClassPred, isEqPred,
72 mkDictTy, tcSplitPredTy_maybe,
73 isPredTy, isDictTy, tcSplitDFunTy, tcSplitDFunHead, predTyUnique,
74 mkClassPred, isInheritablePred, isIPPred,
75 dataConsStupidTheta, isRefineableTy, isRefineablePred,
77 ---------------------------------
78 -- Foreign import and export
79 isFFIArgumentTy, -- :: DynFlags -> Safety -> Type -> Bool
80 isFFIImportResultTy, -- :: DynFlags -> Type -> Bool
81 isFFIExportResultTy, -- :: Type -> Bool
82 isFFIExternalTy, -- :: Type -> Bool
83 isFFIDynArgumentTy, -- :: Type -> Bool
84 isFFIDynResultTy, -- :: Type -> Bool
85 isFFILabelTy, -- :: Type -> Bool
86 isFFIDotnetTy, -- :: DynFlags -> Type -> Bool
87 isFFIDotnetObjTy, -- :: Type -> Bool
88 isFFITy, -- :: Type -> Bool
89 tcSplitIOType_maybe, -- :: Type -> Maybe Type
90 toDNType, -- :: Type -> DNType
92 --------------------------------
93 -- Rexported from Type
94 Kind, -- Stuff to do with kinds is insensitive to pre/post Tc
95 unliftedTypeKind, liftedTypeKind, argTypeKind,
96 openTypeKind, mkArrowKind, mkArrowKinds,
97 isLiftedTypeKind, isUnliftedTypeKind, isSubOpenTypeKind,
98 isSubArgTypeKind, isSubKind, defaultKind,
99 kindVarRef, mkKindVar,
101 Type, PredType(..), ThetaType,
102 mkForAllTy, mkForAllTys,
103 mkFunTy, mkFunTys, zipFunTys,
104 mkTyConApp, mkAppTy, mkAppTys, applyTy, applyTys,
105 mkTyVarTy, mkTyVarTys, mkTyConTy, mkPredTy, mkPredTys,
107 -- Type substitutions
108 TvSubst(..), -- Representation visible to a few friends
109 TvSubstEnv, emptyTvSubst, substEqSpec,
110 mkOpenTvSubst, zipOpenTvSubst, zipTopTvSubst, mkTopTvSubst, notElemTvSubst,
111 getTvSubstEnv, setTvSubstEnv, getTvInScope, extendTvInScope, lookupTyVar,
112 extendTvSubst, extendTvSubstList, isInScope, mkTvSubst, zipTyEnv,
113 substTy, substTys, substTyWith, substTheta, substTyVar, substTyVars, substTyVarBndr,
115 isUnLiftedType, -- Source types are always lifted
116 isUnboxedTupleType, -- Ditto
119 tidyTopType, tidyType, tidyPred, tidyTypes, tidyFreeTyVars, tidyOpenType, tidyOpenTypes,
120 tidyTyVarBndr, tidyOpenTyVar, tidyOpenTyVars, tidySkolemTyVar,
123 tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tyVarsOfTheta,
124 tcTyVarsOfType, tcTyVarsOfTypes, exactTyVarsOfType, exactTyVarsOfTypes,
126 pprKind, pprParendKind,
127 pprType, pprParendType, pprTypeApp, pprTyThingCategory,
128 pprPred, pprTheta, pprThetaArrow, pprClassPred
132 #include "HsVersions.h"
166 %************************************************************************
170 %************************************************************************
172 The type checker divides the generic Type world into the
173 following more structured beasts:
175 sigma ::= forall tyvars. phi
176 -- A sigma type is a qualified type
178 -- Note that even if 'tyvars' is empty, theta
179 -- may not be: e.g. (?x::Int) => Int
181 -- Note that 'sigma' is in prenex form:
182 -- all the foralls are at the front.
183 -- A 'phi' type has no foralls to the right of
191 -- A 'tau' type has no quantification anywhere
192 -- Note that the args of a type constructor must be taus
194 | tycon tau_1 .. tau_n
198 -- In all cases, a (saturated) type synonym application is legal,
199 -- provided it expands to the required form.
202 type TcTyVar = TyVar -- Used only during type inference
203 type TcType = Type -- A TcType can have mutable type variables
204 -- Invariant on ForAllTy in TcTypes:
206 -- a cannot occur inside a MutTyVar in T; that is,
207 -- T is "flattened" before quantifying over a
209 -- These types do not have boxy type variables in them
210 type TcPredType = PredType
211 type TcThetaType = ThetaType
212 type TcSigmaType = TcType
213 type TcRhoType = TcType
214 type TcTauType = TcType
216 type TcTyVarSet = TyVarSet
218 -- These types may have boxy type variables in them
219 type BoxyTyVar = TcTyVar
220 type BoxyRhoType = TcType
221 type BoxyThetaType = TcThetaType
222 type BoxySigmaType = TcType
223 type BoxyType = TcType
227 %************************************************************************
229 \subsection{TyVarDetails}
231 %************************************************************************
233 TyVarDetails gives extra info about type variables, used during type
234 checking. It's attached to mutable type variables only.
235 It's knot-tied back to Var.lhs. There is no reason in principle
236 why Var.lhs shouldn't actually have the definition, but it "belongs" here.
239 Note [Signature skolems]
240 ~~~~~~~~~~~~~~~~~~~~~~~~
245 (x,y,z) = ([y,z], z, head x)
247 Here, x and y have type sigs, which go into the environment. We used to
248 instantiate their types with skolem constants, and push those types into
249 the RHS, so we'd typecheck the RHS with type
251 where a*, b* are skolem constants, and c is an ordinary meta type varible.
253 The trouble is that the occurrences of z in the RHS force a* and b* to
254 be the *same*, so we can't make them into skolem constants that don't unify
255 with each other. Alas.
257 One solution would be insist that in the above defn the programmer uses
258 the same type variable in both type signatures. But that takes explanation.
260 The alternative (currently implemented) is to have a special kind of skolem
261 constant, SigTv, which can unify with other SigTvs. These are *not* treated
262 as righd for the purposes of GADTs. And they are used *only* for pattern
263 bindings and mutually recursive function bindings. See the function
264 TcBinds.tcInstSig, and its use_skols parameter.
268 -- A TyVarDetails is inside a TyVar
270 = SkolemTv SkolemInfo -- A skolem constant
272 | MetaTv BoxInfo (IORef MetaDetails)
275 = BoxTv -- The contents is a (non-boxy) sigma-type
276 -- That is, this MetaTv is a "box"
278 | TauTv -- The contents is a (non-boxy) tau-type
279 -- That is, this MetaTv is an ordinary unification variable
281 | SigTv SkolemInfo -- A variant of TauTv, except that it should not be
282 -- unified with a type, only with a type variable
283 -- SigTvs are only distinguished to improve error messages
284 -- see Note [Signature skolems]
285 -- The MetaDetails, if filled in, will
286 -- always be another SigTv or a SkolemTv
289 -- A TauTv is always filled in with a tau-type, which
290 -- never contains any BoxTvs, nor any ForAlls
292 -- However, a BoxTv can contain a type that contains further BoxTvs
293 -- Notably, when typechecking an explicit list, say [e1,e2], with
294 -- expected type being a box b1, we fill in b1 with (List b2), where
295 -- b2 is another (currently empty) box.
298 = Flexi -- Flexi type variables unify to become
301 | Indirect TcType -- INVARIANT:
302 -- For a BoxTv, this type must be non-boxy
303 -- For a TauTv, this type must be a tau-type
305 -- Generally speaking, SkolemInfo should not contain location info
306 -- that is contained in the Name of the tyvar with this SkolemInfo
308 = SigSkol UserTypeCtxt -- A skolem that is created by instantiating
309 -- a programmer-supplied type signature
310 -- Location of the binding site is on the TyVar
312 -- The rest are for non-scoped skolems
313 | ClsSkol Class -- Bound at a class decl
314 | InstSkol -- Bound at an instance decl
315 | FamInstSkol -- Bound at a family instance decl
316 | PatSkol DataCon -- An existential type variable bound by a pattern for
317 -- a data constructor with an existential type. E.g.
318 -- data T = forall a. Eq a => MkT a
320 -- The pattern MkT x will allocate an existential type
322 | ArrowSkol -- An arrow form (see TcArrows)
324 | RuleSkol RuleName -- The LHS of a RULE
325 | GenSkol [TcTyVar] -- Bound when doing a subsumption check for
326 TcType -- (forall tvs. ty)
328 | RuntimeUnkSkol -- a type variable used to represent an unknown
329 -- runtime type (used in the GHCi debugger)
331 | UnkSkol -- Unhelpful info (until I improve it)
333 -------------------------------------
334 -- UserTypeCtxt describes the places where a
335 -- programmer-written type signature can occur
336 -- Like SkolemInfo, no location info
338 = FunSigCtxt Name -- Function type signature
339 -- Also used for types in SPECIALISE pragmas
340 | ExprSigCtxt -- Expression type signature
341 | ConArgCtxt Name -- Data constructor argument
342 | TySynCtxt Name -- RHS of a type synonym decl
343 | GenPatCtxt -- Pattern in generic decl
344 -- f{| a+b |} (Inl x) = ...
345 | LamPatSigCtxt -- Type sig in lambda pattern
347 | BindPatSigCtxt -- Type sig in pattern binding pattern
349 | ResSigCtxt -- Result type sig
351 | ForSigCtxt Name -- Foreign inport or export signature
352 | DefaultDeclCtxt -- Types in a default declaration
353 | SpecInstCtxt -- SPECIALISE instance pragma
355 -- Notes re TySynCtxt
356 -- We allow type synonyms that aren't types; e.g. type List = []
358 -- If the RHS mentions tyvars that aren't in scope, we'll
359 -- quantify over them:
360 -- e.g. type T = a->a
361 -- will become type T = forall a. a->a
363 -- With gla-exts that's right, but for H98 we should complain.
365 ---------------------------------
368 mkKindName :: Unique -> Name
369 mkKindName unique = mkSystemName unique kind_var_occ
371 kindVarRef :: KindVar -> IORef MetaDetails
373 ASSERT ( isTcTyVar tc )
374 case tcTyVarDetails tc of
375 MetaTv TauTv ref -> ref
376 other -> pprPanic "kindVarRef" (ppr tc)
378 mkKindVar :: Unique -> IORef MetaDetails -> KindVar
380 = mkTcTyVar (mkKindName u)
381 tySuperKind -- not sure this is right,
382 -- do we need kind vars for
386 kind_var_occ :: OccName -- Just one for all KindVars
387 -- They may be jiggled by tidying
388 kind_var_occ = mkOccName tvName "k"
392 %************************************************************************
396 %************************************************************************
399 pprTcTyVarDetails :: TcTyVarDetails -> SDoc
401 pprTcTyVarDetails (SkolemTv _) = ptext SLIT("sk")
402 pprTcTyVarDetails (MetaTv BoxTv _) = ptext SLIT("box")
403 pprTcTyVarDetails (MetaTv TauTv _) = ptext SLIT("tau")
404 pprTcTyVarDetails (MetaTv (SigTv _) _) = ptext SLIT("sig")
406 pprUserTypeCtxt :: UserTypeCtxt -> SDoc
407 pprUserTypeCtxt (FunSigCtxt n) = ptext SLIT("the type signature for") <+> quotes (ppr n)
408 pprUserTypeCtxt ExprSigCtxt = ptext SLIT("an expression type signature")
409 pprUserTypeCtxt (ConArgCtxt c) = ptext SLIT("the type of the constructor") <+> quotes (ppr c)
410 pprUserTypeCtxt (TySynCtxt c) = ptext SLIT("the RHS of the type synonym") <+> quotes (ppr c)
411 pprUserTypeCtxt GenPatCtxt = ptext SLIT("the type pattern of a generic definition")
412 pprUserTypeCtxt LamPatSigCtxt = ptext SLIT("a pattern type signature")
413 pprUserTypeCtxt BindPatSigCtxt = ptext SLIT("a pattern type signature")
414 pprUserTypeCtxt ResSigCtxt = ptext SLIT("a result type signature")
415 pprUserTypeCtxt (ForSigCtxt n) = ptext SLIT("the foreign declaration for") <+> quotes (ppr n)
416 pprUserTypeCtxt DefaultDeclCtxt = ptext SLIT("a type in a `default' declaration")
417 pprUserTypeCtxt SpecInstCtxt = ptext SLIT("a SPECIALISE instance pragma")
420 --------------------------------
421 tidySkolemTyVar :: TidyEnv -> TcTyVar -> (TidyEnv, TcTyVar)
422 -- Tidy the type inside a GenSkol, preparatory to printing it
423 tidySkolemTyVar env tv
424 = ASSERT( isSkolemTyVar tv || isSigTyVar tv )
425 (env1, mkTcTyVar (tyVarName tv) (tyVarKind tv) info1)
427 (env1, info1) = case tcTyVarDetails tv of
428 SkolemTv info -> (env1, SkolemTv info')
430 (env1, info') = tidy_skol_info env info
431 MetaTv (SigTv info) box -> (env1, MetaTv (SigTv info') box)
433 (env1, info') = tidy_skol_info env info
436 tidy_skol_info env (GenSkol tvs ty) = (env2, GenSkol tvs1 ty1)
438 (env1, tvs1) = tidyOpenTyVars env tvs
439 (env2, ty1) = tidyOpenType env1 ty
440 tidy_skol_info env info = (env, info)
442 pprSkolTvBinding :: TcTyVar -> SDoc
443 -- Print info about the binding of a skolem tyvar,
444 -- or nothing if we don't have anything useful to say
446 = ASSERT ( isTcTyVar tv )
447 quotes (ppr tv) <+> ppr_details (tcTyVarDetails tv)
449 ppr_details (MetaTv TauTv _) = ptext SLIT("is a meta type variable")
450 ppr_details (MetaTv BoxTv _) = ptext SLIT("is a boxy type variable")
451 ppr_details (MetaTv (SigTv info) _) = ppr_skol info
452 ppr_details (SkolemTv info) = ppr_skol info
454 ppr_skol UnkSkol = empty -- Unhelpful; omit
455 ppr_skol RuntimeUnkSkol = ptext SLIT("is an unknown runtime type")
456 ppr_skol info = sep [ptext SLIT("is a rigid type variable bound by"),
457 sep [pprSkolInfo info,
458 nest 2 (ptext SLIT("at") <+> ppr (getSrcLoc tv))]]
460 pprSkolInfo :: SkolemInfo -> SDoc
461 pprSkolInfo (SigSkol ctxt) = pprUserTypeCtxt ctxt
462 pprSkolInfo (ClsSkol cls) = ptext SLIT("the class declaration for") <+> quotes (ppr cls)
463 pprSkolInfo InstSkol = ptext SLIT("the instance declaration")
464 pprSkolInfo FamInstSkol = ptext SLIT("the family instance declaration")
465 pprSkolInfo (RuleSkol name) = ptext SLIT("the RULE") <+> doubleQuotes (ftext name)
466 pprSkolInfo ArrowSkol = ptext SLIT("the arrow form")
467 pprSkolInfo (PatSkol dc) = sep [ptext SLIT("the constructor") <+> quotes (ppr dc)]
468 pprSkolInfo (GenSkol tvs ty) = sep [ptext SLIT("the polymorphic type"),
469 nest 2 (quotes (ppr (mkForAllTys tvs ty)))]
472 -- For type variables the others are dealt with by pprSkolTvBinding.
473 -- For Insts, these cases should not happen
474 pprSkolInfo UnkSkol = panic "UnkSkol"
475 pprSkolInfo RuntimeUnkSkol = panic "RuntimeUnkSkol"
477 instance Outputable MetaDetails where
478 ppr Flexi = ptext SLIT("Flexi")
479 ppr (Indirect ty) = ptext SLIT("Indirect") <+> ppr ty
483 %************************************************************************
487 %************************************************************************
490 isImmutableTyVar :: TyVar -> Bool
493 | isTcTyVar tv = isSkolemTyVar tv
496 isTyConableTyVar, isSkolemTyVar, isExistentialTyVar,
497 isBoxyTyVar, isMetaTyVar :: TcTyVar -> Bool
500 -- True of a meta-type variable tha can be filled in
501 -- with a type constructor application; in particular,
503 = ASSERT( isTcTyVar tv)
504 case tcTyVarDetails tv of
505 MetaTv BoxTv _ -> True
506 MetaTv TauTv _ -> True
507 MetaTv (SigTv {}) _ -> False
511 = ASSERT( isTcTyVar tv )
512 case tcTyVarDetails tv of
516 isExistentialTyVar tv -- Existential type variable, bound by a pattern
517 = ASSERT( isTcTyVar tv )
518 case tcTyVarDetails tv of
519 SkolemTv (PatSkol {}) -> True
523 = ASSERT2( isTcTyVar tv, ppr tv )
524 case tcTyVarDetails tv of
529 = ASSERT( isTcTyVar tv )
530 case tcTyVarDetails tv of
531 MetaTv BoxTv _ -> True
535 = ASSERT( isTcTyVar tv )
536 case tcTyVarDetails tv of
537 MetaTv (SigTv _) _ -> True
540 metaTvRef :: TyVar -> IORef MetaDetails
542 = ASSERT( isTcTyVar tv )
543 case tcTyVarDetails tv of
545 other -> pprPanic "metaTvRef" (ppr tv)
547 isFlexi, isIndirect :: MetaDetails -> Bool
549 isFlexi other = False
551 isIndirect (Indirect _) = True
552 isIndirect other = False
556 %************************************************************************
558 \subsection{Tau, sigma and rho}
560 %************************************************************************
563 mkSigmaTy :: [TyVar] -> [PredType] -> Type -> Type
564 mkSigmaTy tyvars theta tau = mkForAllTys tyvars (mkPhiTy theta tau)
566 mkPhiTy :: [PredType] -> Type -> Type
567 mkPhiTy theta ty = foldr (\p r -> mkFunTy (mkPredTy p) r) ty theta
570 @isTauTy@ tests for nested for-alls. It should not be called on a boxy type.
573 isTauTy :: Type -> Bool
574 isTauTy ty | Just ty' <- tcView ty = isTauTy ty'
575 isTauTy (TyVarTy tv) = ASSERT( not (isTcTyVar tv && isBoxyTyVar tv) )
577 isTauTy (TyConApp tc tys) = all isTauTy tys && isTauTyCon tc
578 isTauTy (AppTy a b) = isTauTy a && isTauTy b
579 isTauTy (FunTy a b) = isTauTy a && isTauTy b
580 isTauTy (PredTy p) = True -- Don't look through source types
581 isTauTy other = False
584 isTauTyCon :: TyCon -> Bool
585 -- Returns False for type synonyms whose expansion is a polytype
587 | isClosedSynTyCon tc = isTauTy (snd (synTyConDefn tc))
591 isBoxyTy :: TcType -> Bool
592 isBoxyTy ty = any isBoxyTyVar (varSetElems (tcTyVarsOfType ty))
594 isRigidTy :: TcType -> Bool
595 -- A type is rigid if it has no meta type variables in it
596 isRigidTy ty = all isImmutableTyVar (varSetElems (tcTyVarsOfType ty))
598 isRefineableTy :: TcType -> Bool
599 -- A type should have type refinements applied to it if it has
600 -- free type variables, and they are all rigid
601 isRefineableTy ty = not (null tc_tvs) && all isImmutableTyVar tc_tvs
603 tc_tvs = varSetElems (tcTyVarsOfType ty)
605 isRefineablePred :: TcPredType -> Bool
606 isRefineablePred pred = not (null tc_tvs) && all isImmutableTyVar tc_tvs
608 tc_tvs = varSetElems (tcTyVarsOfPred pred)
611 getDFunTyKey :: Type -> OccName -- Get some string from a type, to be used to
612 -- construct a dictionary function name
613 getDFunTyKey ty | Just ty' <- tcView ty = getDFunTyKey ty'
614 getDFunTyKey (TyVarTy tv) = getOccName tv
615 getDFunTyKey (TyConApp tc _) = getOccName tc
616 getDFunTyKey (AppTy fun _) = getDFunTyKey fun
617 getDFunTyKey (FunTy arg _) = getOccName funTyCon
618 getDFunTyKey (ForAllTy _ t) = getDFunTyKey t
619 getDFunTyKey ty = pprPanic "getDFunTyKey" (pprType ty)
620 -- PredTy shouldn't happen
624 %************************************************************************
626 \subsection{Expanding and splitting}
628 %************************************************************************
630 These tcSplit functions are like their non-Tc analogues, but
631 a) they do not look through newtypes
632 b) they do not look through PredTys
633 c) [future] they ignore usage-type annotations
635 However, they are non-monadic and do not follow through mutable type
636 variables. It's up to you to make sure this doesn't matter.
639 tcSplitForAllTys :: Type -> ([TyVar], Type)
640 tcSplitForAllTys ty = split ty ty []
642 split orig_ty ty tvs | Just ty' <- tcView ty = split orig_ty ty' tvs
643 split orig_ty (ForAllTy tv ty) tvs
644 | not (isCoVar tv) = split ty ty (tv:tvs)
645 split orig_ty t tvs = (reverse tvs, orig_ty)
647 tcIsForAllTy ty | Just ty' <- tcView ty = tcIsForAllTy ty'
648 tcIsForAllTy (ForAllTy tv ty) = not (isCoVar tv)
649 tcIsForAllTy t = False
651 tcSplitPhiTy :: Type -> (ThetaType, Type)
652 tcSplitPhiTy ty = split ty ty []
654 split orig_ty ty tvs | Just ty' <- tcView ty = split orig_ty ty' tvs
656 split orig_ty (ForAllTy tv ty) ts
657 | isCoVar tv = split ty ty (eq_pred:ts)
659 PredTy eq_pred = tyVarKind tv
660 split orig_ty (FunTy arg res) ts
661 | Just p <- tcSplitPredTy_maybe arg = split res res (p:ts)
662 split orig_ty ty ts = (reverse ts, orig_ty)
664 tcSplitSigmaTy :: Type -> ([TyVar], ThetaType, Type)
665 tcSplitSigmaTy ty = case tcSplitForAllTys ty of
666 (tvs, rho) -> case tcSplitPhiTy rho of
667 (theta, tau) -> (tvs, theta, tau)
669 -----------------------
672 -> ( [([TyVar], ThetaType)], -- forall as.C => forall bs.D
673 TcSigmaType) -- The rest of the type
675 -- We need a loop here because we are now prepared to entertain
677 -- f:: forall a. Eq a => forall b. Baz b => tau
678 -- We want to instantiate this to
679 -- f2::tau {f2 = f1 b (Baz b), f1 = f a (Eq a)}
681 tcMultiSplitSigmaTy sigma
682 = case (tcSplitSigmaTy sigma) of
683 ([],[],ty) -> ([], sigma)
684 (tvs, theta, ty) -> case tcMultiSplitSigmaTy ty of
685 (pairs, rest) -> ((tvs,theta):pairs, rest)
687 -----------------------
688 tcTyConAppTyCon :: Type -> TyCon
689 tcTyConAppTyCon ty = case tcSplitTyConApp_maybe ty of
691 Nothing -> pprPanic "tcTyConAppTyCon" (pprType ty)
693 tcTyConAppArgs :: Type -> [Type]
694 tcTyConAppArgs ty = case tcSplitTyConApp_maybe ty of
695 Just (_, args) -> args
696 Nothing -> pprPanic "tcTyConAppArgs" (pprType ty)
698 tcSplitTyConApp :: Type -> (TyCon, [Type])
699 tcSplitTyConApp ty = case tcSplitTyConApp_maybe ty of
701 Nothing -> pprPanic "tcSplitTyConApp" (pprType ty)
703 tcSplitTyConApp_maybe :: Type -> Maybe (TyCon, [Type])
704 tcSplitTyConApp_maybe ty | Just ty' <- tcView ty = tcSplitTyConApp_maybe ty'
705 tcSplitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
706 tcSplitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res])
707 -- Newtypes are opaque, so they may be split
708 -- However, predicates are not treated
709 -- as tycon applications by the type checker
710 tcSplitTyConApp_maybe other = Nothing
712 -----------------------
713 tcSplitFunTys :: Type -> ([Type], Type)
714 tcSplitFunTys ty = case tcSplitFunTy_maybe ty of
716 Just (arg,res) -> (arg:args, res')
718 (args,res') = tcSplitFunTys res
720 tcSplitFunTy_maybe :: Type -> Maybe (Type, Type)
721 tcSplitFunTy_maybe ty | Just ty' <- tcView ty = tcSplitFunTy_maybe ty'
722 tcSplitFunTy_maybe (FunTy arg res) | not (isPredTy arg) = Just (arg, res)
723 tcSplitFunTy_maybe other = Nothing
724 -- Note the (not (isPredTy arg)) guard
725 -- Consider (?x::Int) => Bool
726 -- We don't want to treat this as a function type!
727 -- A concrete example is test tc230:
728 -- f :: () -> (?p :: ()) => () -> ()
734 -> Arity -- N: Number of desired args
735 -> ([TcSigmaType], -- Arg types (N or fewer)
736 TcSigmaType) -- The rest of the type
738 tcSplitFunTysN ty n_args
741 | Just (arg,res) <- tcSplitFunTy_maybe ty
742 = case tcSplitFunTysN res (n_args - 1) of
743 (args, res) -> (arg:args, res)
747 tcSplitFunTy ty = expectJust "tcSplitFunTy" (tcSplitFunTy_maybe ty)
748 tcFunArgTy ty = fst (tcSplitFunTy ty)
749 tcFunResultTy ty = snd (tcSplitFunTy ty)
751 -----------------------
752 tcSplitAppTy_maybe :: Type -> Maybe (Type, Type)
753 tcSplitAppTy_maybe ty | Just ty' <- tcView ty = tcSplitAppTy_maybe ty'
754 tcSplitAppTy_maybe ty = repSplitAppTy_maybe ty
756 tcSplitAppTy :: Type -> (Type, Type)
757 tcSplitAppTy ty = case tcSplitAppTy_maybe ty of
759 Nothing -> pprPanic "tcSplitAppTy" (pprType ty)
761 tcSplitAppTys :: Type -> (Type, [Type])
765 go ty args = case tcSplitAppTy_maybe ty of
766 Just (ty', arg) -> go ty' (arg:args)
769 -----------------------
770 tcGetTyVar_maybe :: Type -> Maybe TyVar
771 tcGetTyVar_maybe ty | Just ty' <- tcView ty = tcGetTyVar_maybe ty'
772 tcGetTyVar_maybe (TyVarTy tv) = Just tv
773 tcGetTyVar_maybe other = Nothing
775 tcGetTyVar :: String -> Type -> TyVar
776 tcGetTyVar msg ty = expectJust msg (tcGetTyVar_maybe ty)
778 tcIsTyVarTy :: Type -> Bool
779 tcIsTyVarTy ty = maybeToBool (tcGetTyVar_maybe ty)
781 -----------------------
782 tcSplitDFunTy :: Type -> ([TyVar], [PredType], Class, [Type])
783 -- Split the type of a dictionary function
785 = case tcSplitSigmaTy ty of { (tvs, theta, tau) ->
786 case tcSplitDFunHead tau of { (clas, tys) ->
787 (tvs, theta, clas, tys) }}
789 tcSplitDFunHead :: Type -> (Class, [Type])
791 = case tcSplitPredTy_maybe tau of
792 Just (ClassP clas tys) -> (clas, tys)
793 other -> panic "tcSplitDFunHead"
795 tcInstHeadTyNotSynonym :: Type -> Bool
796 -- Used in Haskell-98 mode, for the argument types of an instance head
797 -- These must not be type synonyms, but everywhere else type synonyms
798 -- are transparent, so we need a special function here
799 tcInstHeadTyNotSynonym ty
801 NoteTy _ ty -> tcInstHeadTyNotSynonym ty
802 TyConApp tc tys -> not (isSynTyCon tc)
805 tcInstHeadTyAppAllTyVars :: Type -> Bool
806 -- Used in Haskell-98 mode, for the argument types of an instance head
807 -- These must be a constructor applied to type variable arguments
808 tcInstHeadTyAppAllTyVars ty
810 NoteTy _ ty -> tcInstHeadTyAppAllTyVars ty
811 TyConApp _ tys -> ok tys
812 FunTy arg res -> ok [arg, res]
815 -- Check that all the types are type variables,
816 -- and that each is distinct
817 ok tys = equalLength tvs tys && hasNoDups tvs
819 tvs = mapCatMaybes get_tv tys
821 get_tv (NoteTy _ ty) = get_tv ty -- Again, do not look
822 get_tv (TyVarTy tv) = Just tv -- through synonyms
823 get_tv other = Nothing
828 %************************************************************************
830 \subsection{Predicate types}
832 %************************************************************************
835 tcSplitPredTy_maybe :: Type -> Maybe PredType
836 -- Returns Just for predicates only
837 tcSplitPredTy_maybe ty | Just ty' <- tcView ty = tcSplitPredTy_maybe ty'
838 tcSplitPredTy_maybe (PredTy p) = Just p
839 tcSplitPredTy_maybe other = Nothing
841 predTyUnique :: PredType -> Unique
842 predTyUnique (IParam n _) = getUnique (ipNameName n)
843 predTyUnique (ClassP clas tys) = getUnique clas
844 predTyUnique (EqPred a b) = pprPanic "predTyUnique" (ppr (EqPred a b))
848 --------------------- Dictionary types ---------------------------------
851 mkClassPred clas tys = ClassP clas tys
853 isClassPred :: PredType -> Bool
854 isClassPred (ClassP clas tys) = True
855 isClassPred other = False
857 isTyVarClassPred (ClassP clas tys) = all tcIsTyVarTy tys
858 isTyVarClassPred other = False
860 getClassPredTys_maybe :: PredType -> Maybe (Class, [Type])
861 getClassPredTys_maybe (ClassP clas tys) = Just (clas, tys)
862 getClassPredTys_maybe _ = Nothing
864 getClassPredTys :: PredType -> (Class, [Type])
865 getClassPredTys (ClassP clas tys) = (clas, tys)
866 getClassPredTys other = panic "getClassPredTys"
868 mkDictTy :: Class -> [Type] -> Type
869 mkDictTy clas tys = mkPredTy (ClassP clas tys)
871 isDictTy :: Type -> Bool
872 isDictTy ty | Just ty' <- tcView ty = isDictTy ty'
873 isDictTy (PredTy p) = isClassPred p
874 isDictTy other = False
877 --------------------- Implicit parameters ---------------------------------
880 isIPPred :: PredType -> Bool
881 isIPPred (IParam _ _) = True
882 isIPPred other = False
884 isInheritablePred :: PredType -> Bool
885 -- Can be inherited by a context. For example, consider
886 -- f x = let g y = (?v, y+x)
887 -- in (g 3 with ?v = 8,
889 -- The point is that g's type must be quantifed over ?v:
890 -- g :: (?v :: a) => a -> a
891 -- but it doesn't need to be quantified over the Num a dictionary
892 -- which can be free in g's rhs, and shared by both calls to g
893 isInheritablePred (ClassP _ _) = True
894 isInheritablePred (EqPred _ _) = True
895 isInheritablePred other = False
898 --------------------- Equality predicates ---------------------------------
900 substEqSpec :: TvSubst -> [(TyVar,Type)] -> [(TcType,TcType)]
901 substEqSpec subst eq_spec = [ (substTyVar subst tv, substTy subst ty)
902 | (tv,ty) <- eq_spec]
905 --------------------- The stupid theta (sigh) ---------------------------------
908 dataConsStupidTheta :: [DataCon] -> ThetaType
909 -- Union the stupid thetas from all the specified constructors (non-empty)
910 -- All the constructors should have the same result type, modulo alpha conversion
911 -- The resulting ThetaType uses type variables from the *first* constructor in the list
913 -- It's here because it's used in MkId.mkRecordSelId, and in TcExpr
914 dataConsStupidTheta (con1:cons)
915 = nubBy tcEqPred all_preds
917 all_preds = dataConStupidTheta con1 ++ other_stupids
918 res_ty1 = dataConOrigResTy con1
919 other_stupids = [ substPred subst pred
921 , let (tvs, _, _, res_ty) = dataConSig con
922 Just subst = tcMatchTy (mkVarSet tvs) res_ty res_ty1
923 , pred <- dataConStupidTheta con ]
924 dataConsStupidTheta [] = panic "dataConsStupidTheta"
928 %************************************************************************
930 \subsection{Predicates}
932 %************************************************************************
934 isSigmaTy returns true of any qualified type. It doesn't *necessarily* have
936 f :: (?x::Int) => Int -> Int
939 isSigmaTy :: Type -> Bool
940 isSigmaTy ty | Just ty' <- tcView ty = isSigmaTy ty'
941 isSigmaTy (ForAllTy tyvar ty) = True
942 isSigmaTy (FunTy a b) = isPredTy a
945 isOverloadedTy :: Type -> Bool
946 isOverloadedTy ty | Just ty' <- tcView ty = isOverloadedTy ty'
947 isOverloadedTy (ForAllTy tyvar ty) = isOverloadedTy ty
948 isOverloadedTy (FunTy a b) = isPredTy a
949 isOverloadedTy _ = False
951 isPredTy :: Type -> Bool -- Belongs in TcType because it does
952 -- not look through newtypes, or predtypes (of course)
953 isPredTy ty | Just ty' <- tcView ty = isPredTy ty'
954 isPredTy (PredTy sty) = True
959 isFloatTy = is_tc floatTyConKey
960 isDoubleTy = is_tc doubleTyConKey
961 isIntegerTy = is_tc integerTyConKey
962 isIntTy = is_tc intTyConKey
963 isBoolTy = is_tc boolTyConKey
964 isUnitTy = is_tc unitTyConKey
965 isCharTy = is_tc charTyConKey
968 = case tcSplitTyConApp_maybe ty of
969 Just (tc, [arg_ty]) -> tc == listTyCon && isCharTy arg_ty
972 is_tc :: Unique -> Type -> Bool
973 -- Newtypes are opaque to this
974 is_tc uniq ty = case tcSplitTyConApp_maybe ty of
975 Just (tc, _) -> uniq == getUnique tc
980 %************************************************************************
984 %************************************************************************
987 deNoteType :: Type -> Type
988 -- Remove all *outermost* type synonyms and other notes
989 deNoteType ty | Just ty' <- tcView ty = deNoteType ty'
994 tcTyVarsOfType :: Type -> TcTyVarSet
995 -- Just the *TcTyVars* free in the type
996 -- (Types.tyVarsOfTypes finds all free TyVars)
997 tcTyVarsOfType (TyVarTy tv) = if isTcTyVar tv then unitVarSet tv
999 tcTyVarsOfType (TyConApp tycon tys) = tcTyVarsOfTypes tys
1000 tcTyVarsOfType (NoteTy _ ty) = tcTyVarsOfType ty
1001 tcTyVarsOfType (PredTy sty) = tcTyVarsOfPred sty
1002 tcTyVarsOfType (FunTy arg res) = tcTyVarsOfType arg `unionVarSet` tcTyVarsOfType res
1003 tcTyVarsOfType (AppTy fun arg) = tcTyVarsOfType fun `unionVarSet` tcTyVarsOfType arg
1004 tcTyVarsOfType (ForAllTy tyvar ty) = (tcTyVarsOfType ty `delVarSet` tyvar)
1005 `unionVarSet` tcTyVarsOfTyVar tyvar
1006 -- We do sometimes quantify over skolem TcTyVars
1008 tcTyVarsOfTyVar :: TcTyVar -> TyVarSet
1009 tcTyVarsOfTyVar tv | isCoVar tv = tcTyVarsOfType (tyVarKind tv)
1010 | otherwise = emptyVarSet
1012 tcTyVarsOfTypes :: [Type] -> TyVarSet
1013 tcTyVarsOfTypes tys = foldr (unionVarSet.tcTyVarsOfType) emptyVarSet tys
1015 tcTyVarsOfPred :: PredType -> TyVarSet
1016 tcTyVarsOfPred (IParam _ ty) = tcTyVarsOfType ty
1017 tcTyVarsOfPred (ClassP _ tys) = tcTyVarsOfTypes tys
1018 tcTyVarsOfPred (EqPred ty1 ty2) = tcTyVarsOfType ty1 `unionVarSet` tcTyVarsOfType ty2
1021 Note [Silly type synonym]
1022 ~~~~~~~~~~~~~~~~~~~~~~~~~
1025 What are the free tyvars of (T x)? Empty, of course!
1026 Here's the example that Ralf Laemmel showed me:
1027 foo :: (forall a. C u a -> C u a) -> u
1028 mappend :: Monoid u => u -> u -> u
1030 bar :: Monoid u => u
1031 bar = foo (\t -> t `mappend` t)
1032 We have to generalise at the arg to f, and we don't
1033 want to capture the constraint (Monad (C u a)) because
1034 it appears to mention a. Pretty silly, but it was useful to him.
1036 exactTyVarsOfType is used by the type checker to figure out exactly
1037 which type variables are mentioned in a type. It's also used in the
1038 smart-app checking code --- see TcExpr.tcIdApp
1041 exactTyVarsOfType :: TcType -> TyVarSet
1042 -- Find the free type variables (of any kind)
1043 -- but *expand* type synonyms. See Note [Silly type synonym] above.
1044 exactTyVarsOfType ty
1047 go ty | Just ty' <- tcView ty = go ty' -- This is the key line
1048 go (TyVarTy tv) = unitVarSet tv
1049 go (TyConApp tycon tys) = exactTyVarsOfTypes tys
1050 go (PredTy ty) = go_pred ty
1051 go (FunTy arg res) = go arg `unionVarSet` go res
1052 go (AppTy fun arg) = go fun `unionVarSet` go arg
1053 go (ForAllTy tyvar ty) = delVarSet (go ty) tyvar
1054 `unionVarSet` go_tv tyvar
1055 go (NoteTy _ _) = panic "exactTyVarsOfType" -- Handled by tcView
1057 go_pred (IParam _ ty) = go ty
1058 go_pred (ClassP _ tys) = exactTyVarsOfTypes tys
1059 go_pred (EqPred ty1 ty2) = go ty1 `unionVarSet` go ty2
1061 go_tv tyvar | isCoVar tyvar = go (tyVarKind tyvar)
1062 | otherwise = emptyVarSet
1064 exactTyVarsOfTypes :: [TcType] -> TyVarSet
1065 exactTyVarsOfTypes tys = foldr (unionVarSet . exactTyVarsOfType) emptyVarSet tys
1068 Find the free tycons and classes of a type. This is used in the front
1069 end of the compiler.
1072 tyClsNamesOfType :: Type -> NameSet
1073 tyClsNamesOfType (TyVarTy tv) = emptyNameSet
1074 tyClsNamesOfType (TyConApp tycon tys) = unitNameSet (getName tycon) `unionNameSets` tyClsNamesOfTypes tys
1075 tyClsNamesOfType (NoteTy _ ty2) = tyClsNamesOfType ty2
1076 tyClsNamesOfType (PredTy (IParam n ty)) = tyClsNamesOfType ty
1077 tyClsNamesOfType (PredTy (ClassP cl tys)) = unitNameSet (getName cl) `unionNameSets` tyClsNamesOfTypes tys
1078 tyClsNamesOfType (PredTy (EqPred ty1 ty2)) = tyClsNamesOfType ty1 `unionNameSets` tyClsNamesOfType ty2
1079 tyClsNamesOfType (FunTy arg res) = tyClsNamesOfType arg `unionNameSets` tyClsNamesOfType res
1080 tyClsNamesOfType (AppTy fun arg) = tyClsNamesOfType fun `unionNameSets` tyClsNamesOfType arg
1081 tyClsNamesOfType (ForAllTy tyvar ty) = tyClsNamesOfType ty
1083 tyClsNamesOfTypes tys = foldr (unionNameSets . tyClsNamesOfType) emptyNameSet tys
1085 tyClsNamesOfDFunHead :: Type -> NameSet
1086 -- Find the free type constructors and classes
1087 -- of the head of the dfun instance type
1088 -- The 'dfun_head_type' is because of
1089 -- instance Foo a => Baz T where ...
1090 -- The decl is an orphan if Baz and T are both not locally defined,
1091 -- even if Foo *is* locally defined
1092 tyClsNamesOfDFunHead dfun_ty
1093 = case tcSplitSigmaTy dfun_ty of
1094 (tvs,_,head_ty) -> tyClsNamesOfType head_ty
1098 %************************************************************************
1100 \subsection[TysWiredIn-ext-type]{External types}
1102 %************************************************************************
1104 The compiler's foreign function interface supports the passing of a
1105 restricted set of types as arguments and results (the restricting factor
1109 tcSplitIOType_maybe :: Type -> Maybe (TyCon, Type, CoercionI)
1110 -- (isIOType t) returns Just (IO,t',co)
1111 -- if co : t ~ IO t'
1112 -- returns Nothing otherwise
1113 tcSplitIOType_maybe ty
1114 = case tcSplitTyConApp_maybe ty of
1115 -- This split absolutely has to be a tcSplit, because we must
1116 -- see the IO type; and it's a newtype which is transparent to splitTyConApp.
1118 Just (io_tycon, [io_res_ty])
1119 | io_tycon `hasKey` ioTyConKey
1120 -> Just (io_tycon, io_res_ty, IdCo)
1123 | not (isRecursiveTyCon tc)
1124 , Just (ty, co1) <- instNewTyCon_maybe tc tys
1125 -- Newtypes that require a coercion are ok
1126 -> case tcSplitIOType_maybe ty of
1128 Just (tc, ty', co2) -> Just (tc, ty', co1 `mkTransCoI` co2)
1132 isFFITy :: Type -> Bool
1133 -- True for any TyCon that can possibly be an arg or result of an FFI call
1134 isFFITy ty = checkRepTyCon legalFFITyCon ty
1136 isFFIArgumentTy :: DynFlags -> Safety -> Type -> Bool
1137 -- Checks for valid argument type for a 'foreign import'
1138 isFFIArgumentTy dflags safety ty
1139 = checkRepTyCon (legalOutgoingTyCon dflags safety) ty
1141 isFFIExternalTy :: Type -> Bool
1142 -- Types that are allowed as arguments of a 'foreign export'
1143 isFFIExternalTy ty = checkRepTyCon legalFEArgTyCon ty
1145 isFFIImportResultTy :: DynFlags -> Type -> Bool
1146 isFFIImportResultTy dflags ty
1147 = checkRepTyCon (legalFIResultTyCon dflags) ty
1149 isFFIExportResultTy :: Type -> Bool
1150 isFFIExportResultTy ty = checkRepTyCon legalFEResultTyCon ty
1152 isFFIDynArgumentTy :: Type -> Bool
1153 -- The argument type of a foreign import dynamic must be Ptr, FunPtr, Addr,
1154 -- or a newtype of either.
1155 isFFIDynArgumentTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1157 isFFIDynResultTy :: Type -> Bool
1158 -- The result type of a foreign export dynamic must be Ptr, FunPtr, Addr,
1159 -- or a newtype of either.
1160 isFFIDynResultTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1162 isFFILabelTy :: Type -> Bool
1163 -- The type of a foreign label must be Ptr, FunPtr, Addr,
1164 -- or a newtype of either.
1165 isFFILabelTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1167 isFFIDotnetTy :: DynFlags -> Type -> Bool
1168 isFFIDotnetTy dflags ty
1169 = checkRepTyCon (\ tc -> (legalFIResultTyCon dflags tc ||
1170 isFFIDotnetObjTy ty || isStringTy ty)) ty
1171 -- NB: isStringTy used to look through newtypes, but
1172 -- it no longer does so. May need to adjust isFFIDotNetTy
1173 -- if we do want to look through newtypes.
1176 = checkRepTyCon check_tc t_ty
1178 (_, t_ty) = tcSplitForAllTys ty
1179 check_tc tc = getName tc == objectTyConName
1181 toDNType :: Type -> DNType
1183 | isStringTy ty = DNString
1184 | isFFIDotnetObjTy ty = DNObject
1185 | Just (tc,argTys) <- tcSplitTyConApp_maybe ty
1186 = case lookup (getUnique tc) dn_assoc of
1189 | tc `hasKey` ioTyConKey -> toDNType (head argTys)
1190 | otherwise -> pprPanic ("toDNType: unsupported .NET type")
1191 (pprType ty <+> parens (hcat (map pprType argTys)) <+> ppr tc)
1192 | otherwise = panic "toDNType" -- Is this right?
1194 dn_assoc :: [ (Unique, DNType) ]
1195 dn_assoc = [ (unitTyConKey, DNUnit)
1196 , (intTyConKey, DNInt)
1197 , (int8TyConKey, DNInt8)
1198 , (int16TyConKey, DNInt16)
1199 , (int32TyConKey, DNInt32)
1200 , (int64TyConKey, DNInt64)
1201 , (wordTyConKey, DNInt)
1202 , (word8TyConKey, DNWord8)
1203 , (word16TyConKey, DNWord16)
1204 , (word32TyConKey, DNWord32)
1205 , (word64TyConKey, DNWord64)
1206 , (floatTyConKey, DNFloat)
1207 , (doubleTyConKey, DNDouble)
1208 , (ptrTyConKey, DNPtr)
1209 , (funPtrTyConKey, DNPtr)
1210 , (charTyConKey, DNChar)
1211 , (boolTyConKey, DNBool)
1214 checkRepTyCon :: (TyCon -> Bool) -> Type -> Bool
1215 -- Look through newtypes
1216 -- Non-recursive ones are transparent to splitTyConApp,
1217 -- but recursive ones aren't. Manuel had:
1218 -- newtype T = MkT (Ptr T)
1219 -- and wanted it to work...
1220 checkRepTyCon check_tc ty
1221 | Just (tc,_) <- splitTyConApp_maybe (repType ty) = check_tc tc
1224 checkRepTyConKey :: [Unique] -> Type -> Bool
1225 -- Like checkRepTyCon, but just looks at the TyCon key
1226 checkRepTyConKey keys
1227 = checkRepTyCon (\tc -> tyConUnique tc `elem` keys)
1230 ----------------------------------------------
1231 These chaps do the work; they are not exported
1232 ----------------------------------------------
1235 legalFEArgTyCon :: TyCon -> Bool
1237 -- It's illegal to make foreign exports that take unboxed
1238 -- arguments. The RTS API currently can't invoke such things. --SDM 7/2000
1239 = boxedMarshalableTyCon tc
1241 legalFIResultTyCon :: DynFlags -> TyCon -> Bool
1242 legalFIResultTyCon dflags tc
1243 | tc == unitTyCon = True
1244 | otherwise = marshalableTyCon dflags tc
1246 legalFEResultTyCon :: TyCon -> Bool
1247 legalFEResultTyCon tc
1248 | tc == unitTyCon = True
1249 | otherwise = boxedMarshalableTyCon tc
1251 legalOutgoingTyCon :: DynFlags -> Safety -> TyCon -> Bool
1252 -- Checks validity of types going from Haskell -> external world
1253 legalOutgoingTyCon dflags safety tc
1254 = marshalableTyCon dflags tc
1256 legalFFITyCon :: TyCon -> Bool
1257 -- True for any TyCon that can possibly be an arg or result of an FFI call
1259 = isUnLiftedTyCon tc || boxedMarshalableTyCon tc || tc == unitTyCon
1261 marshalableTyCon dflags tc
1262 = (dopt Opt_UnliftedFFITypes dflags
1263 && isUnLiftedTyCon tc
1264 && case tyConPrimRep tc of -- Note [Marshalling VoidRep]
1267 || boxedMarshalableTyCon tc
1269 boxedMarshalableTyCon tc
1270 = getUnique tc `elem` [ intTyConKey, int8TyConKey, int16TyConKey
1271 , int32TyConKey, int64TyConKey
1272 , wordTyConKey, word8TyConKey, word16TyConKey
1273 , word32TyConKey, word64TyConKey
1274 , floatTyConKey, doubleTyConKey
1275 , ptrTyConKey, funPtrTyConKey
1282 Note [Marshalling VoidRep]
1283 ~~~~~~~~~~~~~~~~~~~~~~~~~~
1284 We don't treat State# (whose PrimRep is VoidRep) as marshalable.
1285 In turn that means you can't write
1286 foreign import foo :: Int -> State# RealWorld
1288 Reason: the back end falls over with panic "primRepHint:VoidRep";
1289 and there is no compelling reason to permit it