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 -- The above warning supression flag is a temporary kludge.
20 -- While working on this module you are encouraged to remove it and fix
21 -- any warnings in the module. See
22 -- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
26 --------------------------------
28 TcType, TcSigmaType, TcRhoType, TcTauType, TcPredType, TcThetaType,
29 TcTyVar, TcTyVarSet, TcKind,
31 BoxyTyVar, BoxySigmaType, BoxyRhoType, BoxyThetaType, BoxyType,
33 --------------------------------
35 UserTypeCtxt(..), pprUserTypeCtxt,
36 TcTyVarDetails(..), BoxInfo(..), pprTcTyVarDetails,
37 MetaDetails(Flexi, Indirect), SkolemInfo(..), pprSkolTvBinding, pprSkolInfo,
38 isImmutableTyVar, isSkolemTyVar, isMetaTyVar, isBoxyTyVar,
39 isSigTyVar, isExistentialTyVar, isTyConableTyVar,
43 --------------------------------
47 --------------------------------
49 -- These are important because they do not look through newtypes
51 tcSplitForAllTys, tcSplitPhiTy,
52 tcSplitFunTy_maybe, tcSplitFunTys, tcFunArgTy, tcFunResultTy, tcSplitFunTysN,
53 tcSplitTyConApp, tcSplitTyConApp_maybe, tcTyConAppTyCon, tcTyConAppArgs,
54 tcSplitAppTy_maybe, tcSplitAppTy, tcSplitAppTys, repSplitAppTy_maybe,
55 tcInstHeadTyNotSynonym, tcInstHeadTyAppAllTyVars,
56 tcGetTyVar_maybe, tcGetTyVar,
57 tcSplitSigmaTy, tcMultiSplitSigmaTy,
59 ---------------------------------
61 -- Again, newtypes are opaque
62 tcEqType, tcEqTypes, tcEqPred, tcCmpType, tcCmpTypes, tcCmpPred, tcEqTypeX,
64 isSigmaTy, isOverloadedTy, isRigidTy, isBoxyTy,
65 isDoubleTy, isFloatTy, isIntTy, isStringTy,
66 isIntegerTy, isBoolTy, isUnitTy, isCharTy,
67 isTauTy, isTauTyCon, tcIsTyVarTy, tcIsForAllTy,
70 ---------------------------------
71 -- Misc type manipulators
73 tyClsNamesOfType, tyClsNamesOfDFunHead,
76 ---------------------------------
78 getClassPredTys_maybe, getClassPredTys,
79 isClassPred, isTyVarClassPred, isEqPred,
80 mkDictTy, tcSplitPredTy_maybe,
81 isPredTy, isDictTy, tcSplitDFunTy, tcSplitDFunHead, predTyUnique,
82 mkClassPred, isInheritablePred, isIPPred,
83 dataConsStupidTheta, isRefineableTy, isRefineablePred,
85 ---------------------------------
86 -- Foreign import and export
87 isFFIArgumentTy, -- :: DynFlags -> Safety -> Type -> Bool
88 isFFIImportResultTy, -- :: DynFlags -> Type -> Bool
89 isFFIExportResultTy, -- :: Type -> Bool
90 isFFIExternalTy, -- :: Type -> Bool
91 isFFIDynArgumentTy, -- :: Type -> Bool
92 isFFIDynResultTy, -- :: Type -> Bool
93 isFFILabelTy, -- :: Type -> Bool
94 isFFIDotnetTy, -- :: DynFlags -> Type -> Bool
95 isFFIDotnetObjTy, -- :: Type -> Bool
96 isFFITy, -- :: Type -> Bool
97 tcSplitIOType_maybe, -- :: Type -> Maybe Type
98 toDNType, -- :: Type -> DNType
100 --------------------------------
101 -- Rexported from Type
102 Kind, -- Stuff to do with kinds is insensitive to pre/post Tc
103 unliftedTypeKind, liftedTypeKind, argTypeKind,
104 openTypeKind, mkArrowKind, mkArrowKinds,
105 isLiftedTypeKind, isUnliftedTypeKind, isSubOpenTypeKind,
106 isSubArgTypeKind, isSubKind, defaultKind,
107 kindVarRef, mkKindVar,
109 Type, PredType(..), ThetaType,
110 mkForAllTy, mkForAllTys,
111 mkFunTy, mkFunTys, zipFunTys,
112 mkTyConApp, mkAppTy, mkAppTys, applyTy, applyTys,
113 mkTyVarTy, mkTyVarTys, mkTyConTy, mkPredTy, mkPredTys,
115 -- Type substitutions
116 TvSubst(..), -- Representation visible to a few friends
117 TvSubstEnv, emptyTvSubst, substEqSpec,
118 mkOpenTvSubst, zipOpenTvSubst, zipTopTvSubst, mkTopTvSubst, notElemTvSubst,
119 getTvSubstEnv, setTvSubstEnv, getTvInScope, extendTvInScope, lookupTyVar,
120 extendTvSubst, extendTvSubstList, isInScope, mkTvSubst, zipTyEnv,
121 substTy, substTys, substTyWith, substTheta, substTyVar, substTyVars, substTyVarBndr,
123 isUnLiftedType, -- Source types are always lifted
124 isUnboxedTupleType, -- Ditto
127 tidyTopType, tidyType, tidyPred, tidyTypes, tidyFreeTyVars, tidyOpenType, tidyOpenTypes,
128 tidyTyVarBndr, tidyOpenTyVar, tidyOpenTyVars, tidySkolemTyVar,
131 tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tyVarsOfTheta,
132 tcTyVarsOfType, tcTyVarsOfTypes, exactTyVarsOfType, exactTyVarsOfTypes,
134 pprKind, pprParendKind,
135 pprType, pprParendType, pprTypeApp, pprTyThingCategory,
136 pprPred, pprTheta, pprThetaArrow, pprClassPred
140 #include "HsVersions.h"
173 %************************************************************************
177 %************************************************************************
179 The type checker divides the generic Type world into the
180 following more structured beasts:
182 sigma ::= forall tyvars. phi
183 -- A sigma type is a qualified type
185 -- Note that even if 'tyvars' is empty, theta
186 -- may not be: e.g. (?x::Int) => Int
188 -- Note that 'sigma' is in prenex form:
189 -- all the foralls are at the front.
190 -- A 'phi' type has no foralls to the right of
198 -- A 'tau' type has no quantification anywhere
199 -- Note that the args of a type constructor must be taus
201 | tycon tau_1 .. tau_n
205 -- In all cases, a (saturated) type synonym application is legal,
206 -- provided it expands to the required form.
209 type TcTyVar = TyVar -- Used only during type inference
210 type TcType = Type -- A TcType can have mutable type variables
211 -- Invariant on ForAllTy in TcTypes:
213 -- a cannot occur inside a MutTyVar in T; that is,
214 -- T is "flattened" before quantifying over a
216 -- These types do not have boxy type variables in them
217 type TcPredType = PredType
218 type TcThetaType = ThetaType
219 type TcSigmaType = TcType
220 type TcRhoType = TcType
221 type TcTauType = TcType
223 type TcTyVarSet = TyVarSet
225 -- These types may have boxy type variables in them
226 type BoxyTyVar = TcTyVar
227 type BoxyRhoType = TcType
228 type BoxyThetaType = TcThetaType
229 type BoxySigmaType = TcType
230 type BoxyType = TcType
234 %************************************************************************
236 \subsection{TyVarDetails}
238 %************************************************************************
240 TyVarDetails gives extra info about type variables, used during type
241 checking. It's attached to mutable type variables only.
242 It's knot-tied back to Var.lhs. There is no reason in principle
243 why Var.lhs shouldn't actually have the definition, but it "belongs" here.
246 Note [Signature skolems]
247 ~~~~~~~~~~~~~~~~~~~~~~~~
252 (x,y,z) = ([y,z], z, head x)
254 Here, x and y have type sigs, which go into the environment. We used to
255 instantiate their types with skolem constants, and push those types into
256 the RHS, so we'd typecheck the RHS with type
258 where a*, b* are skolem constants, and c is an ordinary meta type varible.
260 The trouble is that the occurrences of z in the RHS force a* and b* to
261 be the *same*, so we can't make them into skolem constants that don't unify
262 with each other. Alas.
264 One solution would be insist that in the above defn the programmer uses
265 the same type variable in both type signatures. But that takes explanation.
267 The alternative (currently implemented) is to have a special kind of skolem
268 constant, SigTv, which can unify with other SigTvs. These are *not* treated
269 as righd for the purposes of GADTs. And they are used *only* for pattern
270 bindings and mutually recursive function bindings. See the function
271 TcBinds.tcInstSig, and its use_skols parameter.
275 -- A TyVarDetails is inside a TyVar
277 = SkolemTv SkolemInfo -- A skolem constant
279 | MetaTv BoxInfo (IORef MetaDetails)
282 = BoxTv -- The contents is a (non-boxy) sigma-type
283 -- That is, this MetaTv is a "box"
285 | TauTv -- The contents is a (non-boxy) tau-type
286 -- That is, this MetaTv is an ordinary unification variable
288 | SigTv SkolemInfo -- A variant of TauTv, except that it should not be
289 -- unified with a type, only with a type variable
290 -- SigTvs are only distinguished to improve error messages
291 -- see Note [Signature skolems]
292 -- The MetaDetails, if filled in, will
293 -- always be another SigTv or a SkolemTv
296 -- A TauTv is always filled in with a tau-type, which
297 -- never contains any BoxTvs, nor any ForAlls
299 -- However, a BoxTv can contain a type that contains further BoxTvs
300 -- Notably, when typechecking an explicit list, say [e1,e2], with
301 -- expected type being a box b1, we fill in b1 with (List b2), where
302 -- b2 is another (currently empty) box.
305 = Flexi -- Flexi type variables unify to become
308 | Indirect TcType -- INVARIANT:
309 -- For a BoxTv, this type must be non-boxy
310 -- For a TauTv, this type must be a tau-type
312 -- Generally speaking, SkolemInfo should not contain location info
313 -- that is contained in the Name of the tyvar with this SkolemInfo
315 = SigSkol UserTypeCtxt -- A skolem that is created by instantiating
316 -- a programmer-supplied type signature
317 -- Location of the binding site is on the TyVar
319 -- The rest are for non-scoped skolems
320 | ClsSkol Class -- Bound at a class decl
321 | InstSkol -- Bound at an instance decl
322 | FamInstSkol -- Bound at a family instance decl
323 | PatSkol DataCon -- An existential type variable bound by a pattern for
324 -- a data constructor with an existential type. E.g.
325 -- data T = forall a. Eq a => MkT a
327 -- The pattern MkT x will allocate an existential type
329 | ArrowSkol -- An arrow form (see TcArrows)
331 | RuleSkol RuleName -- The LHS of a RULE
332 | GenSkol [TcTyVar] -- Bound when doing a subsumption check for
333 TcType -- (forall tvs. ty)
335 | RuntimeUnkSkol -- a type variable used to represent an unknown
336 -- runtime type (used in the GHCi debugger)
338 | UnkSkol -- Unhelpful info (until I improve it)
340 -------------------------------------
341 -- UserTypeCtxt describes the places where a
342 -- programmer-written type signature can occur
343 -- Like SkolemInfo, no location info
345 = FunSigCtxt Name -- Function type signature
346 -- Also used for types in SPECIALISE pragmas
347 | ExprSigCtxt -- Expression type signature
348 | ConArgCtxt Name -- Data constructor argument
349 | TySynCtxt Name -- RHS of a type synonym decl
350 | GenPatCtxt -- Pattern in generic decl
351 -- f{| a+b |} (Inl x) = ...
352 | LamPatSigCtxt -- Type sig in lambda pattern
354 | BindPatSigCtxt -- Type sig in pattern binding pattern
356 | ResSigCtxt -- Result type sig
358 | ForSigCtxt Name -- Foreign inport or export signature
359 | DefaultDeclCtxt -- Types in a default declaration
360 | SpecInstCtxt -- SPECIALISE instance pragma
362 -- Notes re TySynCtxt
363 -- We allow type synonyms that aren't types; e.g. type List = []
365 -- If the RHS mentions tyvars that aren't in scope, we'll
366 -- quantify over them:
367 -- e.g. type T = a->a
368 -- will become type T = forall a. a->a
370 -- With gla-exts that's right, but for H98 we should complain.
372 ---------------------------------
375 mkKindName :: Unique -> Name
376 mkKindName unique = mkSystemName unique kind_var_occ
378 kindVarRef :: KindVar -> IORef MetaDetails
380 ASSERT ( isTcTyVar tc )
381 case tcTyVarDetails tc of
382 MetaTv TauTv ref -> ref
383 other -> pprPanic "kindVarRef" (ppr tc)
385 mkKindVar :: Unique -> IORef MetaDetails -> KindVar
387 = mkTcTyVar (mkKindName u)
388 tySuperKind -- not sure this is right,
389 -- do we need kind vars for
393 kind_var_occ :: OccName -- Just one for all KindVars
394 -- They may be jiggled by tidying
395 kind_var_occ = mkOccName tvName "k"
398 %************************************************************************
402 %************************************************************************
405 pprTcTyVarDetails :: TcTyVarDetails -> SDoc
407 pprTcTyVarDetails (SkolemTv _) = ptext SLIT("sk")
408 pprTcTyVarDetails (MetaTv BoxTv _) = ptext SLIT("box")
409 pprTcTyVarDetails (MetaTv TauTv _) = ptext SLIT("tau")
410 pprTcTyVarDetails (MetaTv (SigTv _) _) = ptext SLIT("sig")
412 pprUserTypeCtxt :: UserTypeCtxt -> SDoc
413 pprUserTypeCtxt (FunSigCtxt n) = ptext SLIT("the type signature for") <+> quotes (ppr n)
414 pprUserTypeCtxt ExprSigCtxt = ptext SLIT("an expression type signature")
415 pprUserTypeCtxt (ConArgCtxt c) = ptext SLIT("the type of the constructor") <+> quotes (ppr c)
416 pprUserTypeCtxt (TySynCtxt c) = ptext SLIT("the RHS of the type synonym") <+> quotes (ppr c)
417 pprUserTypeCtxt GenPatCtxt = ptext SLIT("the type pattern of a generic definition")
418 pprUserTypeCtxt LamPatSigCtxt = ptext SLIT("a pattern type signature")
419 pprUserTypeCtxt BindPatSigCtxt = ptext SLIT("a pattern type signature")
420 pprUserTypeCtxt ResSigCtxt = ptext SLIT("a result type signature")
421 pprUserTypeCtxt (ForSigCtxt n) = ptext SLIT("the foreign declaration for") <+> quotes (ppr n)
422 pprUserTypeCtxt DefaultDeclCtxt = ptext SLIT("a type in a `default' declaration")
423 pprUserTypeCtxt SpecInstCtxt = ptext SLIT("a SPECIALISE instance pragma")
426 --------------------------------
427 tidySkolemTyVar :: TidyEnv -> TcTyVar -> (TidyEnv, TcTyVar)
428 -- Tidy the type inside a GenSkol, preparatory to printing it
429 tidySkolemTyVar env tv
430 = ASSERT( isSkolemTyVar tv || isSigTyVar tv )
431 (env1, mkTcTyVar (tyVarName tv) (tyVarKind tv) info1)
433 (env1, info1) = case tcTyVarDetails tv of
434 SkolemTv info -> (env1, SkolemTv info')
436 (env1, info') = tidy_skol_info env info
437 MetaTv (SigTv info) box -> (env1, MetaTv (SigTv info') box)
439 (env1, info') = tidy_skol_info env info
442 tidy_skol_info env (GenSkol tvs ty) = (env2, GenSkol tvs1 ty1)
444 (env1, tvs1) = tidyOpenTyVars env tvs
445 (env2, ty1) = tidyOpenType env1 ty
446 tidy_skol_info env info = (env, info)
448 pprSkolTvBinding :: TcTyVar -> SDoc
449 -- Print info about the binding of a skolem tyvar,
450 -- or nothing if we don't have anything useful to say
452 = ASSERT ( isTcTyVar tv )
453 quotes (ppr tv) <+> ppr_details (tcTyVarDetails tv)
455 ppr_details (MetaTv TauTv _) = ptext SLIT("is a meta type variable")
456 ppr_details (MetaTv BoxTv _) = ptext SLIT("is a boxy type variable")
457 ppr_details (MetaTv (SigTv info) _) = ppr_skol info
458 ppr_details (SkolemTv info) = ppr_skol info
460 ppr_skol UnkSkol = empty -- Unhelpful; omit
461 ppr_skol RuntimeUnkSkol = ptext SLIT("is an unknown runtime type")
462 ppr_skol info = sep [ptext SLIT("is a rigid type variable bound by"),
463 sep [pprSkolInfo info,
464 nest 2 (ptext SLIT("at") <+> ppr (getSrcLoc tv))]]
466 pprSkolInfo :: SkolemInfo -> SDoc
467 pprSkolInfo (SigSkol ctxt) = pprUserTypeCtxt ctxt
468 pprSkolInfo (ClsSkol cls) = ptext SLIT("the class declaration for") <+> quotes (ppr cls)
469 pprSkolInfo InstSkol = ptext SLIT("the instance declaration")
470 pprSkolInfo FamInstSkol = ptext SLIT("the family instance declaration")
471 pprSkolInfo (RuleSkol name) = ptext SLIT("the RULE") <+> doubleQuotes (ftext name)
472 pprSkolInfo ArrowSkol = ptext SLIT("the arrow form")
473 pprSkolInfo (PatSkol dc) = sep [ptext SLIT("the constructor") <+> quotes (ppr dc)]
474 pprSkolInfo (GenSkol tvs ty) = sep [ptext SLIT("the polymorphic type"),
475 nest 2 (quotes (ppr (mkForAllTys tvs ty)))]
478 -- For type variables the others are dealt with by pprSkolTvBinding.
479 -- For Insts, these cases should not happen
480 pprSkolInfo UnkSkol = panic "UnkSkol"
481 pprSkolInfo RuntimeUnkSkol = panic "RuntimeUnkSkol"
483 instance Outputable MetaDetails where
484 ppr Flexi = ptext SLIT("Flexi")
485 ppr (Indirect ty) = ptext SLIT("Indirect") <+> ppr ty
489 %************************************************************************
493 %************************************************************************
496 isImmutableTyVar :: TyVar -> Bool
499 | isTcTyVar tv = isSkolemTyVar tv
502 isTyConableTyVar, isSkolemTyVar, isExistentialTyVar,
503 isBoxyTyVar, isMetaTyVar :: TcTyVar -> Bool
506 -- True of a meta-type variable that can be filled in
507 -- with a type constructor application; in particular,
509 = ASSERT( isTcTyVar tv)
510 case tcTyVarDetails tv of
511 MetaTv BoxTv _ -> True
512 MetaTv TauTv _ -> True
513 MetaTv (SigTv {}) _ -> False
517 = ASSERT( isTcTyVar tv )
518 case tcTyVarDetails tv of
522 isExistentialTyVar tv -- Existential type variable, bound by a pattern
523 = ASSERT( isTcTyVar tv )
524 case tcTyVarDetails tv of
525 SkolemTv (PatSkol {}) -> True
529 = ASSERT2( isTcTyVar tv, ppr tv )
530 case tcTyVarDetails tv of
535 = ASSERT( isTcTyVar tv )
536 case tcTyVarDetails tv of
537 MetaTv BoxTv _ -> True
541 = ASSERT( isTcTyVar tv )
542 case tcTyVarDetails tv of
543 MetaTv (SigTv _) _ -> True
546 metaTvRef :: TyVar -> IORef MetaDetails
548 = ASSERT2( isTcTyVar tv, ppr tv )
549 case tcTyVarDetails tv of
551 other -> pprPanic "metaTvRef" (ppr tv)
553 isFlexi, isIndirect :: MetaDetails -> Bool
555 isFlexi other = False
557 isIndirect (Indirect _) = True
558 isIndirect other = False
562 %************************************************************************
564 \subsection{Tau, sigma and rho}
566 %************************************************************************
569 mkSigmaTy :: [TyVar] -> [PredType] -> Type -> Type
570 mkSigmaTy tyvars theta tau = mkForAllTys tyvars (mkPhiTy theta tau)
572 mkPhiTy :: [PredType] -> Type -> Type
573 mkPhiTy theta ty = foldr (\p r -> mkFunTy (mkPredTy p) r) ty theta
576 @isTauTy@ tests for nested for-alls. It should not be called on a boxy type.
579 isTauTy :: Type -> Bool
580 isTauTy ty | Just ty' <- tcView ty = isTauTy ty'
581 isTauTy (TyVarTy tv) = ASSERT( not (isTcTyVar tv && isBoxyTyVar tv) )
583 isTauTy (TyConApp tc tys) = all isTauTy tys && isTauTyCon tc
584 isTauTy (AppTy a b) = isTauTy a && isTauTy b
585 isTauTy (FunTy a b) = isTauTy a && isTauTy b
586 isTauTy (PredTy p) = True -- Don't look through source types
587 isTauTy other = False
590 isTauTyCon :: TyCon -> Bool
591 -- Returns False for type synonyms whose expansion is a polytype
593 | isClosedSynTyCon tc = isTauTy (snd (synTyConDefn tc))
597 isBoxyTy :: TcType -> Bool
598 isBoxyTy ty = any isBoxyTyVar (varSetElems (tcTyVarsOfType ty))
600 isRigidTy :: TcType -> Bool
601 -- A type is rigid if it has no meta type variables in it
602 isRigidTy ty = all isImmutableTyVar (varSetElems (tcTyVarsOfType ty))
604 isRefineableTy :: TcType -> (Bool,Bool)
605 -- A type should have type refinements applied to it if it has
606 -- free type variables, and they are all rigid
607 isRefineableTy ty = (null tc_tvs, all isImmutableTyVar tc_tvs)
609 tc_tvs = varSetElems (tcTyVarsOfType ty)
611 isRefineablePred :: TcPredType -> Bool
612 isRefineablePred pred = not (null tc_tvs) && all isImmutableTyVar tc_tvs
614 tc_tvs = varSetElems (tcTyVarsOfPred pred)
617 getDFunTyKey :: Type -> OccName -- Get some string from a type, to be used to
618 -- construct a dictionary function name
619 getDFunTyKey ty | Just ty' <- tcView ty = getDFunTyKey ty'
620 getDFunTyKey (TyVarTy tv) = getOccName tv
621 getDFunTyKey (TyConApp tc _) = getOccName tc
622 getDFunTyKey (AppTy fun _) = getDFunTyKey fun
623 getDFunTyKey (FunTy arg _) = getOccName funTyCon
624 getDFunTyKey (ForAllTy _ t) = getDFunTyKey t
625 getDFunTyKey ty = pprPanic "getDFunTyKey" (pprType ty)
626 -- PredTy shouldn't happen
630 %************************************************************************
632 \subsection{Expanding and splitting}
634 %************************************************************************
636 These tcSplit functions are like their non-Tc analogues, but
637 a) they do not look through newtypes
638 b) they do not look through PredTys
639 c) [future] they ignore usage-type annotations
641 However, they are non-monadic and do not follow through mutable type
642 variables. It's up to you to make sure this doesn't matter.
645 tcSplitForAllTys :: Type -> ([TyVar], Type)
646 tcSplitForAllTys ty = split ty ty []
648 split orig_ty ty tvs | Just ty' <- tcView ty = split orig_ty ty' tvs
649 split orig_ty (ForAllTy tv ty) tvs
650 | not (isCoVar tv) = split ty ty (tv:tvs)
651 split orig_ty t tvs = (reverse tvs, orig_ty)
653 tcIsForAllTy ty | Just ty' <- tcView ty = tcIsForAllTy ty'
654 tcIsForAllTy (ForAllTy tv ty) = not (isCoVar tv)
655 tcIsForAllTy t = False
657 tcSplitPhiTy :: Type -> (ThetaType, Type)
658 tcSplitPhiTy ty = split ty ty []
660 split orig_ty ty tvs | Just ty' <- tcView ty = split orig_ty ty' tvs
662 split orig_ty (ForAllTy tv ty) ts
663 | isCoVar tv = split ty ty (eq_pred:ts)
665 PredTy eq_pred = tyVarKind tv
666 split orig_ty (FunTy arg res) ts
667 | Just p <- tcSplitPredTy_maybe arg = split res res (p:ts)
668 split orig_ty ty ts = (reverse ts, orig_ty)
670 tcSplitSigmaTy :: Type -> ([TyVar], ThetaType, Type)
671 tcSplitSigmaTy ty = case tcSplitForAllTys ty of
672 (tvs, rho) -> case tcSplitPhiTy rho of
673 (theta, tau) -> (tvs, theta, tau)
675 -----------------------
678 -> ( [([TyVar], ThetaType)], -- forall as.C => forall bs.D
679 TcSigmaType) -- The rest of the type
681 -- We need a loop here because we are now prepared to entertain
683 -- f:: forall a. Eq a => forall b. Baz b => tau
684 -- We want to instantiate this to
685 -- f2::tau {f2 = f1 b (Baz b), f1 = f a (Eq a)}
687 tcMultiSplitSigmaTy sigma
688 = case (tcSplitSigmaTy sigma) of
689 ([],[],ty) -> ([], sigma)
690 (tvs, theta, ty) -> case tcMultiSplitSigmaTy ty of
691 (pairs, rest) -> ((tvs,theta):pairs, rest)
693 -----------------------
694 tcTyConAppTyCon :: Type -> TyCon
695 tcTyConAppTyCon ty = case tcSplitTyConApp_maybe ty of
697 Nothing -> pprPanic "tcTyConAppTyCon" (pprType ty)
699 tcTyConAppArgs :: Type -> [Type]
700 tcTyConAppArgs ty = case tcSplitTyConApp_maybe ty of
701 Just (_, args) -> args
702 Nothing -> pprPanic "tcTyConAppArgs" (pprType ty)
704 tcSplitTyConApp :: Type -> (TyCon, [Type])
705 tcSplitTyConApp ty = case tcSplitTyConApp_maybe ty of
707 Nothing -> pprPanic "tcSplitTyConApp" (pprType ty)
709 tcSplitTyConApp_maybe :: Type -> Maybe (TyCon, [Type])
710 tcSplitTyConApp_maybe ty | Just ty' <- tcView ty = tcSplitTyConApp_maybe ty'
711 tcSplitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
712 tcSplitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res])
713 -- Newtypes are opaque, so they may be split
714 -- However, predicates are not treated
715 -- as tycon applications by the type checker
716 tcSplitTyConApp_maybe other = Nothing
718 -----------------------
719 tcSplitFunTys :: Type -> ([Type], Type)
720 tcSplitFunTys ty = case tcSplitFunTy_maybe ty of
722 Just (arg,res) -> (arg:args, res')
724 (args,res') = tcSplitFunTys res
726 tcSplitFunTy_maybe :: Type -> Maybe (Type, Type)
727 tcSplitFunTy_maybe ty | Just ty' <- tcView ty = tcSplitFunTy_maybe ty'
728 tcSplitFunTy_maybe (FunTy arg res) | not (isPredTy arg) = Just (arg, res)
729 tcSplitFunTy_maybe other = Nothing
730 -- Note the (not (isPredTy arg)) guard
731 -- Consider (?x::Int) => Bool
732 -- We don't want to treat this as a function type!
733 -- A concrete example is test tc230:
734 -- f :: () -> (?p :: ()) => () -> ()
740 -> Arity -- N: Number of desired args
741 -> ([TcSigmaType], -- Arg types (N or fewer)
742 TcSigmaType) -- The rest of the type
744 tcSplitFunTysN ty n_args
747 | Just (arg,res) <- tcSplitFunTy_maybe ty
748 = case tcSplitFunTysN res (n_args - 1) of
749 (args, res) -> (arg:args, res)
753 tcSplitFunTy ty = expectJust "tcSplitFunTy" (tcSplitFunTy_maybe ty)
754 tcFunArgTy ty = fst (tcSplitFunTy ty)
755 tcFunResultTy ty = snd (tcSplitFunTy ty)
757 -----------------------
758 tcSplitAppTy_maybe :: Type -> Maybe (Type, Type)
759 tcSplitAppTy_maybe ty | Just ty' <- tcView ty = tcSplitAppTy_maybe ty'
760 tcSplitAppTy_maybe ty = repSplitAppTy_maybe ty
762 tcSplitAppTy :: Type -> (Type, Type)
763 tcSplitAppTy ty = case tcSplitAppTy_maybe ty of
765 Nothing -> pprPanic "tcSplitAppTy" (pprType ty)
767 tcSplitAppTys :: Type -> (Type, [Type])
771 go ty args = case tcSplitAppTy_maybe ty of
772 Just (ty', arg) -> go ty' (arg:args)
775 -----------------------
776 tcGetTyVar_maybe :: Type -> Maybe TyVar
777 tcGetTyVar_maybe ty | Just ty' <- tcView ty = tcGetTyVar_maybe ty'
778 tcGetTyVar_maybe (TyVarTy tv) = Just tv
779 tcGetTyVar_maybe other = Nothing
781 tcGetTyVar :: String -> Type -> TyVar
782 tcGetTyVar msg ty = expectJust msg (tcGetTyVar_maybe ty)
784 tcIsTyVarTy :: Type -> Bool
785 tcIsTyVarTy ty = maybeToBool (tcGetTyVar_maybe ty)
787 -----------------------
788 tcSplitDFunTy :: Type -> ([TyVar], [PredType], Class, [Type])
789 -- Split the type of a dictionary function
791 = case tcSplitSigmaTy ty of { (tvs, theta, tau) ->
792 case tcSplitDFunHead tau of { (clas, tys) ->
793 (tvs, theta, clas, tys) }}
795 tcSplitDFunHead :: Type -> (Class, [Type])
797 = case tcSplitPredTy_maybe tau of
798 Just (ClassP clas tys) -> (clas, tys)
799 other -> panic "tcSplitDFunHead"
801 tcInstHeadTyNotSynonym :: Type -> Bool
802 -- Used in Haskell-98 mode, for the argument types of an instance head
803 -- These must not be type synonyms, but everywhere else type synonyms
804 -- are transparent, so we need a special function here
805 tcInstHeadTyNotSynonym ty
807 NoteTy _ ty -> tcInstHeadTyNotSynonym ty
808 TyConApp tc tys -> not (isSynTyCon tc)
811 tcInstHeadTyAppAllTyVars :: Type -> Bool
812 -- Used in Haskell-98 mode, for the argument types of an instance head
813 -- These must be a constructor applied to type variable arguments
814 tcInstHeadTyAppAllTyVars ty
816 NoteTy _ ty -> tcInstHeadTyAppAllTyVars ty
817 TyConApp _ tys -> ok tys
818 FunTy arg res -> ok [arg, res]
821 -- Check that all the types are type variables,
822 -- and that each is distinct
823 ok tys = equalLength tvs tys && hasNoDups tvs
825 tvs = mapCatMaybes get_tv tys
827 get_tv (NoteTy _ ty) = get_tv ty -- Again, do not look
828 get_tv (TyVarTy tv) = Just tv -- through synonyms
829 get_tv other = Nothing
834 %************************************************************************
836 \subsection{Predicate types}
838 %************************************************************************
841 tcSplitPredTy_maybe :: Type -> Maybe PredType
842 -- Returns Just for predicates only
843 tcSplitPredTy_maybe ty | Just ty' <- tcView ty = tcSplitPredTy_maybe ty'
844 tcSplitPredTy_maybe (PredTy p) = Just p
845 tcSplitPredTy_maybe other = Nothing
847 predTyUnique :: PredType -> Unique
848 predTyUnique (IParam n _) = getUnique (ipNameName n)
849 predTyUnique (ClassP clas tys) = getUnique clas
850 predTyUnique (EqPred a b) = pprPanic "predTyUnique" (ppr (EqPred a b))
854 --------------------- Dictionary types ---------------------------------
857 mkClassPred clas tys = ClassP clas tys
859 isClassPred :: PredType -> Bool
860 isClassPred (ClassP clas tys) = True
861 isClassPred other = False
863 isTyVarClassPred (ClassP clas tys) = all tcIsTyVarTy tys
864 isTyVarClassPred other = False
866 getClassPredTys_maybe :: PredType -> Maybe (Class, [Type])
867 getClassPredTys_maybe (ClassP clas tys) = Just (clas, tys)
868 getClassPredTys_maybe _ = Nothing
870 getClassPredTys :: PredType -> (Class, [Type])
871 getClassPredTys (ClassP clas tys) = (clas, tys)
872 getClassPredTys other = panic "getClassPredTys"
874 mkDictTy :: Class -> [Type] -> Type
875 mkDictTy clas tys = mkPredTy (ClassP clas tys)
877 isDictTy :: Type -> Bool
878 isDictTy ty | Just ty' <- tcView ty = isDictTy ty'
879 isDictTy (PredTy p) = isClassPred p
880 isDictTy other = False
883 --------------------- Implicit parameters ---------------------------------
886 isIPPred :: PredType -> Bool
887 isIPPred (IParam _ _) = True
888 isIPPred other = False
890 isInheritablePred :: PredType -> Bool
891 -- Can be inherited by a context. For example, consider
892 -- f x = let g y = (?v, y+x)
893 -- in (g 3 with ?v = 8,
895 -- The point is that g's type must be quantifed over ?v:
896 -- g :: (?v :: a) => a -> a
897 -- but it doesn't need to be quantified over the Num a dictionary
898 -- which can be free in g's rhs, and shared by both calls to g
899 isInheritablePred (ClassP _ _) = True
900 isInheritablePred (EqPred _ _) = True
901 isInheritablePred other = False
904 --------------------- Equality predicates ---------------------------------
906 substEqSpec :: TvSubst -> [(TyVar,Type)] -> [(TcType,TcType)]
907 substEqSpec subst eq_spec = [ (substTyVar subst tv, substTy subst ty)
908 | (tv,ty) <- eq_spec]
911 --------------------- The stupid theta (sigh) ---------------------------------
914 dataConsStupidTheta :: [DataCon] -> ThetaType
915 -- Union the stupid thetas from all the specified constructors (non-empty)
916 -- All the constructors should have the same result type, modulo alpha conversion
917 -- The resulting ThetaType uses type variables from the *first* constructor in the list
919 -- It's here because it's used in MkId.mkRecordSelId, and in TcExpr
920 dataConsStupidTheta (con1:cons)
921 = nubBy tcEqPred all_preds
923 all_preds = dataConStupidTheta con1 ++ other_stupids
924 res_ty1 = dataConOrigResTy con1
925 other_stupids = [ substPred subst pred
927 , let (tvs, _, _, res_ty) = dataConSig con
928 Just subst = tcMatchTy (mkVarSet tvs) res_ty res_ty1
929 , pred <- dataConStupidTheta con ]
930 dataConsStupidTheta [] = panic "dataConsStupidTheta"
934 %************************************************************************
936 \subsection{Predicates}
938 %************************************************************************
940 isSigmaTy returns true of any qualified type. It doesn't *necessarily* have
942 f :: (?x::Int) => Int -> Int
945 isSigmaTy :: Type -> Bool
946 isSigmaTy ty | Just ty' <- tcView ty = isSigmaTy ty'
947 isSigmaTy (ForAllTy tyvar ty) = True
948 isSigmaTy (FunTy a b) = isPredTy a
951 isOverloadedTy :: Type -> Bool
952 isOverloadedTy ty | Just ty' <- tcView ty = isOverloadedTy ty'
953 isOverloadedTy (ForAllTy tyvar ty) = isOverloadedTy ty
954 isOverloadedTy (FunTy a b) = isPredTy a
955 isOverloadedTy _ = False
957 isPredTy :: Type -> Bool -- Belongs in TcType because it does
958 -- not look through newtypes, or predtypes (of course)
959 isPredTy ty | Just ty' <- tcView ty = isPredTy ty'
960 isPredTy (PredTy sty) = True
965 isFloatTy = is_tc floatTyConKey
966 isDoubleTy = is_tc doubleTyConKey
967 isIntegerTy = is_tc integerTyConKey
968 isIntTy = is_tc intTyConKey
969 isBoolTy = is_tc boolTyConKey
970 isUnitTy = is_tc unitTyConKey
971 isCharTy = is_tc charTyConKey
974 = case tcSplitTyConApp_maybe ty of
975 Just (tc, [arg_ty]) -> tc == listTyCon && isCharTy arg_ty
978 is_tc :: Unique -> Type -> Bool
979 -- Newtypes are opaque to this
980 is_tc uniq ty = case tcSplitTyConApp_maybe ty of
981 Just (tc, _) -> uniq == getUnique tc
986 -- NB: Currently used in places where we have already expanded type synonyms;
987 -- hence no 'coreView'. This could, however, be changed without breaking
989 isOpenSynTyConApp :: TcTauType -> Bool
990 isOpenSynTyConApp (TyConApp tc _) = isOpenSynTyCon tc
991 isOpenSynTyConApp _other = False
995 %************************************************************************
999 %************************************************************************
1002 deNoteType :: Type -> Type
1003 -- Remove all *outermost* type synonyms and other notes
1004 deNoteType ty | Just ty' <- tcView ty = deNoteType ty'
1009 tcTyVarsOfType :: Type -> TcTyVarSet
1010 -- Just the *TcTyVars* free in the type
1011 -- (Types.tyVarsOfTypes finds all free TyVars)
1012 tcTyVarsOfType (TyVarTy tv) = if isTcTyVar tv then unitVarSet tv
1014 tcTyVarsOfType (TyConApp tycon tys) = tcTyVarsOfTypes tys
1015 tcTyVarsOfType (NoteTy _ ty) = tcTyVarsOfType ty
1016 tcTyVarsOfType (PredTy sty) = tcTyVarsOfPred sty
1017 tcTyVarsOfType (FunTy arg res) = tcTyVarsOfType arg `unionVarSet` tcTyVarsOfType res
1018 tcTyVarsOfType (AppTy fun arg) = tcTyVarsOfType fun `unionVarSet` tcTyVarsOfType arg
1019 tcTyVarsOfType (ForAllTy tyvar ty) = (tcTyVarsOfType ty `delVarSet` tyvar)
1020 `unionVarSet` tcTyVarsOfTyVar tyvar
1021 -- We do sometimes quantify over skolem TcTyVars
1023 tcTyVarsOfTyVar :: TcTyVar -> TyVarSet
1024 tcTyVarsOfTyVar tv | isCoVar tv = tcTyVarsOfType (tyVarKind tv)
1025 | otherwise = emptyVarSet
1027 tcTyVarsOfTypes :: [Type] -> TyVarSet
1028 tcTyVarsOfTypes tys = foldr (unionVarSet.tcTyVarsOfType) emptyVarSet tys
1030 tcTyVarsOfPred :: PredType -> TyVarSet
1031 tcTyVarsOfPred (IParam _ ty) = tcTyVarsOfType ty
1032 tcTyVarsOfPred (ClassP _ tys) = tcTyVarsOfTypes tys
1033 tcTyVarsOfPred (EqPred ty1 ty2) = tcTyVarsOfType ty1 `unionVarSet` tcTyVarsOfType ty2
1036 Note [Silly type synonym]
1037 ~~~~~~~~~~~~~~~~~~~~~~~~~
1040 What are the free tyvars of (T x)? Empty, of course!
1041 Here's the example that Ralf Laemmel showed me:
1042 foo :: (forall a. C u a -> C u a) -> u
1043 mappend :: Monoid u => u -> u -> u
1045 bar :: Monoid u => u
1046 bar = foo (\t -> t `mappend` t)
1047 We have to generalise at the arg to f, and we don't
1048 want to capture the constraint (Monad (C u a)) because
1049 it appears to mention a. Pretty silly, but it was useful to him.
1051 exactTyVarsOfType is used by the type checker to figure out exactly
1052 which type variables are mentioned in a type. It's also used in the
1053 smart-app checking code --- see TcExpr.tcIdApp
1056 exactTyVarsOfType :: TcType -> TyVarSet
1057 -- Find the free type variables (of any kind)
1058 -- but *expand* type synonyms. See Note [Silly type synonym] above.
1059 exactTyVarsOfType ty
1062 go ty | Just ty' <- tcView ty = go ty' -- This is the key line
1063 go (TyVarTy tv) = unitVarSet tv
1064 go (TyConApp tycon tys) = exactTyVarsOfTypes tys
1065 go (PredTy ty) = go_pred ty
1066 go (FunTy arg res) = go arg `unionVarSet` go res
1067 go (AppTy fun arg) = go fun `unionVarSet` go arg
1068 go (ForAllTy tyvar ty) = delVarSet (go ty) tyvar
1069 `unionVarSet` go_tv tyvar
1070 go (NoteTy _ _) = panic "exactTyVarsOfType" -- Handled by tcView
1072 go_pred (IParam _ ty) = go ty
1073 go_pred (ClassP _ tys) = exactTyVarsOfTypes tys
1074 go_pred (EqPred ty1 ty2) = go ty1 `unionVarSet` go ty2
1076 go_tv tyvar | isCoVar tyvar = go (tyVarKind tyvar)
1077 | otherwise = emptyVarSet
1079 exactTyVarsOfTypes :: [TcType] -> TyVarSet
1080 exactTyVarsOfTypes tys = foldr (unionVarSet . exactTyVarsOfType) emptyVarSet tys
1083 Find the free tycons and classes of a type. This is used in the front
1084 end of the compiler.
1087 tyClsNamesOfType :: Type -> NameSet
1088 tyClsNamesOfType (TyVarTy tv) = emptyNameSet
1089 tyClsNamesOfType (TyConApp tycon tys) = unitNameSet (getName tycon) `unionNameSets` tyClsNamesOfTypes tys
1090 tyClsNamesOfType (NoteTy _ ty2) = tyClsNamesOfType ty2
1091 tyClsNamesOfType (PredTy (IParam n ty)) = tyClsNamesOfType ty
1092 tyClsNamesOfType (PredTy (ClassP cl tys)) = unitNameSet (getName cl) `unionNameSets` tyClsNamesOfTypes tys
1093 tyClsNamesOfType (PredTy (EqPred ty1 ty2)) = tyClsNamesOfType ty1 `unionNameSets` tyClsNamesOfType ty2
1094 tyClsNamesOfType (FunTy arg res) = tyClsNamesOfType arg `unionNameSets` tyClsNamesOfType res
1095 tyClsNamesOfType (AppTy fun arg) = tyClsNamesOfType fun `unionNameSets` tyClsNamesOfType arg
1096 tyClsNamesOfType (ForAllTy tyvar ty) = tyClsNamesOfType ty
1098 tyClsNamesOfTypes tys = foldr (unionNameSets . tyClsNamesOfType) emptyNameSet tys
1100 tyClsNamesOfDFunHead :: Type -> NameSet
1101 -- Find the free type constructors and classes
1102 -- of the head of the dfun instance type
1103 -- The 'dfun_head_type' is because of
1104 -- instance Foo a => Baz T where ...
1105 -- The decl is an orphan if Baz and T are both not locally defined,
1106 -- even if Foo *is* locally defined
1107 tyClsNamesOfDFunHead dfun_ty
1108 = case tcSplitSigmaTy dfun_ty of
1109 (tvs,_,head_ty) -> tyClsNamesOfType head_ty
1113 %************************************************************************
1115 \subsection[TysWiredIn-ext-type]{External types}
1117 %************************************************************************
1119 The compiler's foreign function interface supports the passing of a
1120 restricted set of types as arguments and results (the restricting factor
1124 tcSplitIOType_maybe :: Type -> Maybe (TyCon, Type, CoercionI)
1125 -- (isIOType t) returns Just (IO,t',co)
1126 -- if co : t ~ IO t'
1127 -- returns Nothing otherwise
1128 tcSplitIOType_maybe ty
1129 = case tcSplitTyConApp_maybe ty of
1130 -- This split absolutely has to be a tcSplit, because we must
1131 -- see the IO type; and it's a newtype which is transparent to splitTyConApp.
1133 Just (io_tycon, [io_res_ty])
1134 | io_tycon `hasKey` ioTyConKey
1135 -> Just (io_tycon, io_res_ty, IdCo)
1138 | not (isRecursiveTyCon tc)
1139 , Just (ty, co1) <- instNewTyCon_maybe tc tys
1140 -- Newtypes that require a coercion are ok
1141 -> case tcSplitIOType_maybe ty of
1143 Just (tc, ty', co2) -> Just (tc, ty', co1 `mkTransCoI` co2)
1147 isFFITy :: Type -> Bool
1148 -- True for any TyCon that can possibly be an arg or result of an FFI call
1149 isFFITy ty = checkRepTyCon legalFFITyCon ty
1151 isFFIArgumentTy :: DynFlags -> Safety -> Type -> Bool
1152 -- Checks for valid argument type for a 'foreign import'
1153 isFFIArgumentTy dflags safety ty
1154 = checkRepTyCon (legalOutgoingTyCon dflags safety) ty
1156 isFFIExternalTy :: Type -> Bool
1157 -- Types that are allowed as arguments of a 'foreign export'
1158 isFFIExternalTy ty = checkRepTyCon legalFEArgTyCon ty
1160 isFFIImportResultTy :: DynFlags -> Type -> Bool
1161 isFFIImportResultTy dflags ty
1162 = checkRepTyCon (legalFIResultTyCon dflags) ty
1164 isFFIExportResultTy :: Type -> Bool
1165 isFFIExportResultTy ty = checkRepTyCon legalFEResultTyCon ty
1167 isFFIDynArgumentTy :: Type -> Bool
1168 -- The argument type of a foreign import dynamic must be Ptr, FunPtr, Addr,
1169 -- or a newtype of either.
1170 isFFIDynArgumentTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1172 isFFIDynResultTy :: Type -> Bool
1173 -- The result type of a foreign export dynamic must be Ptr, FunPtr, Addr,
1174 -- or a newtype of either.
1175 isFFIDynResultTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1177 isFFILabelTy :: Type -> Bool
1178 -- The type of a foreign label must be Ptr, FunPtr, Addr,
1179 -- or a newtype of either.
1180 isFFILabelTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1182 isFFIDotnetTy :: DynFlags -> Type -> Bool
1183 isFFIDotnetTy dflags ty
1184 = checkRepTyCon (\ tc -> (legalFIResultTyCon dflags tc ||
1185 isFFIDotnetObjTy ty || isStringTy ty)) ty
1186 -- NB: isStringTy used to look through newtypes, but
1187 -- it no longer does so. May need to adjust isFFIDotNetTy
1188 -- if we do want to look through newtypes.
1191 = checkRepTyCon check_tc t_ty
1193 (_, t_ty) = tcSplitForAllTys ty
1194 check_tc tc = getName tc == objectTyConName
1196 toDNType :: Type -> DNType
1198 | isStringTy ty = DNString
1199 | isFFIDotnetObjTy ty = DNObject
1200 | Just (tc,argTys) <- tcSplitTyConApp_maybe ty
1201 = case lookup (getUnique tc) dn_assoc of
1204 | tc `hasKey` ioTyConKey -> toDNType (head argTys)
1205 | otherwise -> pprPanic ("toDNType: unsupported .NET type")
1206 (pprType ty <+> parens (hcat (map pprType argTys)) <+> ppr tc)
1207 | otherwise = panic "toDNType" -- Is this right?
1209 dn_assoc :: [ (Unique, DNType) ]
1210 dn_assoc = [ (unitTyConKey, DNUnit)
1211 , (intTyConKey, DNInt)
1212 , (int8TyConKey, DNInt8)
1213 , (int16TyConKey, DNInt16)
1214 , (int32TyConKey, DNInt32)
1215 , (int64TyConKey, DNInt64)
1216 , (wordTyConKey, DNInt)
1217 , (word8TyConKey, DNWord8)
1218 , (word16TyConKey, DNWord16)
1219 , (word32TyConKey, DNWord32)
1220 , (word64TyConKey, DNWord64)
1221 , (floatTyConKey, DNFloat)
1222 , (doubleTyConKey, DNDouble)
1223 , (ptrTyConKey, DNPtr)
1224 , (funPtrTyConKey, DNPtr)
1225 , (charTyConKey, DNChar)
1226 , (boolTyConKey, DNBool)
1229 checkRepTyCon :: (TyCon -> Bool) -> Type -> Bool
1230 -- Look through newtypes
1231 -- Non-recursive ones are transparent to splitTyConApp,
1232 -- but recursive ones aren't. Manuel had:
1233 -- newtype T = MkT (Ptr T)
1234 -- and wanted it to work...
1235 checkRepTyCon check_tc ty
1236 | Just (tc,_) <- splitTyConApp_maybe (repType ty) = check_tc tc
1239 checkRepTyConKey :: [Unique] -> Type -> Bool
1240 -- Like checkRepTyCon, but just looks at the TyCon key
1241 checkRepTyConKey keys
1242 = checkRepTyCon (\tc -> tyConUnique tc `elem` keys)
1245 ----------------------------------------------
1246 These chaps do the work; they are not exported
1247 ----------------------------------------------
1250 legalFEArgTyCon :: TyCon -> Bool
1252 -- It's illegal to make foreign exports that take unboxed
1253 -- arguments. The RTS API currently can't invoke such things. --SDM 7/2000
1254 = boxedMarshalableTyCon tc
1256 legalFIResultTyCon :: DynFlags -> TyCon -> Bool
1257 legalFIResultTyCon dflags tc
1258 | tc == unitTyCon = True
1259 | otherwise = marshalableTyCon dflags tc
1261 legalFEResultTyCon :: TyCon -> Bool
1262 legalFEResultTyCon tc
1263 | tc == unitTyCon = True
1264 | otherwise = boxedMarshalableTyCon tc
1266 legalOutgoingTyCon :: DynFlags -> Safety -> TyCon -> Bool
1267 -- Checks validity of types going from Haskell -> external world
1268 legalOutgoingTyCon dflags safety tc
1269 = marshalableTyCon dflags tc
1271 legalFFITyCon :: TyCon -> Bool
1272 -- True for any TyCon that can possibly be an arg or result of an FFI call
1274 = isUnLiftedTyCon tc || boxedMarshalableTyCon tc || tc == unitTyCon
1276 marshalableTyCon dflags tc
1277 = (dopt Opt_UnliftedFFITypes dflags
1278 && isUnLiftedTyCon tc
1279 && not (isUnboxedTupleTyCon tc)
1280 && case tyConPrimRep tc of -- Note [Marshalling VoidRep]
1283 || boxedMarshalableTyCon tc
1285 boxedMarshalableTyCon tc
1286 = getUnique tc `elem` [ intTyConKey, int8TyConKey, int16TyConKey
1287 , int32TyConKey, int64TyConKey
1288 , wordTyConKey, word8TyConKey, word16TyConKey
1289 , word32TyConKey, word64TyConKey
1290 , floatTyConKey, doubleTyConKey
1291 , ptrTyConKey, funPtrTyConKey
1298 Note [Marshalling VoidRep]
1299 ~~~~~~~~~~~~~~~~~~~~~~~~~~
1300 We don't treat State# (whose PrimRep is VoidRep) as marshalable.
1301 In turn that means you can't write
1302 foreign import foo :: Int -> State# RealWorld
1304 Reason: the back end falls over with panic "primRepHint:VoidRep";
1305 and there is no compelling reason to permit it