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,
41 isFlexi, isIndirect, isRuntimeUnk, isUnk,
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 = ptext SLIT("is an unknown type variable") -- Unhelpful
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
560 isRuntimeUnk :: TyVar -> Bool
561 isRuntimeUnk x | isTcTyVar x
562 , SkolemTv RuntimeUnkSkol <- tcTyVarDetails x = True
565 isUnk :: TyVar -> Bool
566 isUnk x | isTcTyVar x
567 , SkolemTv UnkSkol <- tcTyVarDetails x = True
572 %************************************************************************
574 \subsection{Tau, sigma and rho}
576 %************************************************************************
579 mkSigmaTy :: [TyVar] -> [PredType] -> Type -> Type
580 mkSigmaTy tyvars theta tau = mkForAllTys tyvars (mkPhiTy theta tau)
582 mkPhiTy :: [PredType] -> Type -> Type
583 mkPhiTy theta ty = foldr (\p r -> mkFunTy (mkPredTy p) r) ty theta
586 @isTauTy@ tests for nested for-alls. It should not be called on a boxy type.
589 isTauTy :: Type -> Bool
590 isTauTy ty | Just ty' <- tcView ty = isTauTy ty'
591 isTauTy (TyVarTy tv) = ASSERT( not (isTcTyVar tv && isBoxyTyVar tv) )
593 isTauTy (TyConApp tc tys) = all isTauTy tys && isTauTyCon tc
594 isTauTy (AppTy a b) = isTauTy a && isTauTy b
595 isTauTy (FunTy a b) = isTauTy a && isTauTy b
596 isTauTy (PredTy p) = True -- Don't look through source types
597 isTauTy other = False
600 isTauTyCon :: TyCon -> Bool
601 -- Returns False for type synonyms whose expansion is a polytype
603 | isClosedSynTyCon tc = isTauTy (snd (synTyConDefn tc))
607 isBoxyTy :: TcType -> Bool
608 isBoxyTy ty = any isBoxyTyVar (varSetElems (tcTyVarsOfType ty))
610 isRigidTy :: TcType -> Bool
611 -- A type is rigid if it has no meta type variables in it
612 isRigidTy ty = all isImmutableTyVar (varSetElems (tcTyVarsOfType ty))
614 isRefineableTy :: TcType -> (Bool,Bool)
615 -- A type should have type refinements applied to it if it has
616 -- free type variables, and they are all rigid
617 isRefineableTy ty = (null tc_tvs, all isImmutableTyVar tc_tvs)
619 tc_tvs = varSetElems (tcTyVarsOfType ty)
621 isRefineablePred :: TcPredType -> Bool
622 isRefineablePred pred = not (null tc_tvs) && all isImmutableTyVar tc_tvs
624 tc_tvs = varSetElems (tcTyVarsOfPred pred)
627 getDFunTyKey :: Type -> OccName -- Get some string from a type, to be used to
628 -- construct a dictionary function name
629 getDFunTyKey ty | Just ty' <- tcView ty = getDFunTyKey ty'
630 getDFunTyKey (TyVarTy tv) = getOccName tv
631 getDFunTyKey (TyConApp tc _) = getOccName tc
632 getDFunTyKey (AppTy fun _) = getDFunTyKey fun
633 getDFunTyKey (FunTy arg _) = getOccName funTyCon
634 getDFunTyKey (ForAllTy _ t) = getDFunTyKey t
635 getDFunTyKey ty = pprPanic "getDFunTyKey" (pprType ty)
636 -- PredTy shouldn't happen
640 %************************************************************************
642 \subsection{Expanding and splitting}
644 %************************************************************************
646 These tcSplit functions are like their non-Tc analogues, but
647 a) they do not look through newtypes
648 b) they do not look through PredTys
649 c) [future] they ignore usage-type annotations
651 However, they are non-monadic and do not follow through mutable type
652 variables. It's up to you to make sure this doesn't matter.
655 tcSplitForAllTys :: Type -> ([TyVar], Type)
656 tcSplitForAllTys ty = split ty ty []
658 split orig_ty ty tvs | Just ty' <- tcView ty = split orig_ty ty' tvs
659 split orig_ty (ForAllTy tv ty) tvs
660 | not (isCoVar tv) = split ty ty (tv:tvs)
661 split orig_ty t tvs = (reverse tvs, orig_ty)
663 tcIsForAllTy ty | Just ty' <- tcView ty = tcIsForAllTy ty'
664 tcIsForAllTy (ForAllTy tv ty) = not (isCoVar tv)
665 tcIsForAllTy t = False
667 tcSplitPhiTy :: Type -> (ThetaType, Type)
668 tcSplitPhiTy ty = split ty ty []
670 split orig_ty ty tvs | Just ty' <- tcView ty = split orig_ty ty' tvs
672 split orig_ty (ForAllTy tv ty) ts
673 | isCoVar tv = split ty ty (coVarPred tv : ts)
674 split orig_ty (FunTy arg res) ts
675 | Just p <- tcSplitPredTy_maybe arg = split res res (p:ts)
676 split orig_ty ty ts = (reverse ts, orig_ty)
678 tcSplitSigmaTy :: Type -> ([TyVar], ThetaType, Type)
679 tcSplitSigmaTy ty = case tcSplitForAllTys ty of
680 (tvs, rho) -> case tcSplitPhiTy rho of
681 (theta, tau) -> (tvs, theta, tau)
683 -----------------------
686 -> ( [([TyVar], ThetaType)], -- forall as.C => forall bs.D
687 TcSigmaType) -- The rest of the type
689 -- We need a loop here because we are now prepared to entertain
691 -- f:: forall a. Eq a => forall b. Baz b => tau
692 -- We want to instantiate this to
693 -- f2::tau {f2 = f1 b (Baz b), f1 = f a (Eq a)}
695 tcMultiSplitSigmaTy sigma
696 = case (tcSplitSigmaTy sigma) of
697 ([],[],ty) -> ([], sigma)
698 (tvs, theta, ty) -> case tcMultiSplitSigmaTy ty of
699 (pairs, rest) -> ((tvs,theta):pairs, rest)
701 -----------------------
702 tcTyConAppTyCon :: Type -> TyCon
703 tcTyConAppTyCon ty = case tcSplitTyConApp_maybe ty of
705 Nothing -> pprPanic "tcTyConAppTyCon" (pprType ty)
707 tcTyConAppArgs :: Type -> [Type]
708 tcTyConAppArgs ty = case tcSplitTyConApp_maybe ty of
709 Just (_, args) -> args
710 Nothing -> pprPanic "tcTyConAppArgs" (pprType ty)
712 tcSplitTyConApp :: Type -> (TyCon, [Type])
713 tcSplitTyConApp ty = case tcSplitTyConApp_maybe ty of
715 Nothing -> pprPanic "tcSplitTyConApp" (pprType ty)
717 tcSplitTyConApp_maybe :: Type -> Maybe (TyCon, [Type])
718 tcSplitTyConApp_maybe ty | Just ty' <- tcView ty = tcSplitTyConApp_maybe ty'
719 tcSplitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
720 tcSplitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res])
721 -- Newtypes are opaque, so they may be split
722 -- However, predicates are not treated
723 -- as tycon applications by the type checker
724 tcSplitTyConApp_maybe other = Nothing
726 -----------------------
727 tcSplitFunTys :: Type -> ([Type], Type)
728 tcSplitFunTys ty = case tcSplitFunTy_maybe ty of
730 Just (arg,res) -> (arg:args, res')
732 (args,res') = tcSplitFunTys res
734 tcSplitFunTy_maybe :: Type -> Maybe (Type, Type)
735 tcSplitFunTy_maybe ty | Just ty' <- tcView ty = tcSplitFunTy_maybe ty'
736 tcSplitFunTy_maybe (FunTy arg res) | not (isPredTy arg) = Just (arg, res)
737 tcSplitFunTy_maybe other = Nothing
738 -- Note the (not (isPredTy arg)) guard
739 -- Consider (?x::Int) => Bool
740 -- We don't want to treat this as a function type!
741 -- A concrete example is test tc230:
742 -- f :: () -> (?p :: ()) => () -> ()
748 -> Arity -- N: Number of desired args
749 -> ([TcSigmaType], -- Arg types (N or fewer)
750 TcSigmaType) -- The rest of the type
752 tcSplitFunTysN ty n_args
755 | Just (arg,res) <- tcSplitFunTy_maybe ty
756 = case tcSplitFunTysN res (n_args - 1) of
757 (args, res) -> (arg:args, res)
761 tcSplitFunTy ty = expectJust "tcSplitFunTy" (tcSplitFunTy_maybe ty)
762 tcFunArgTy ty = fst (tcSplitFunTy ty)
763 tcFunResultTy ty = snd (tcSplitFunTy ty)
765 -----------------------
766 tcSplitAppTy_maybe :: Type -> Maybe (Type, Type)
767 tcSplitAppTy_maybe ty | Just ty' <- tcView ty = tcSplitAppTy_maybe ty'
768 tcSplitAppTy_maybe ty = repSplitAppTy_maybe ty
770 tcSplitAppTy :: Type -> (Type, Type)
771 tcSplitAppTy ty = case tcSplitAppTy_maybe ty of
773 Nothing -> pprPanic "tcSplitAppTy" (pprType ty)
775 tcSplitAppTys :: Type -> (Type, [Type])
779 go ty args = case tcSplitAppTy_maybe ty of
780 Just (ty', arg) -> go ty' (arg:args)
783 -----------------------
784 tcGetTyVar_maybe :: Type -> Maybe TyVar
785 tcGetTyVar_maybe ty | Just ty' <- tcView ty = tcGetTyVar_maybe ty'
786 tcGetTyVar_maybe (TyVarTy tv) = Just tv
787 tcGetTyVar_maybe other = Nothing
789 tcGetTyVar :: String -> Type -> TyVar
790 tcGetTyVar msg ty = expectJust msg (tcGetTyVar_maybe ty)
792 tcIsTyVarTy :: Type -> Bool
793 tcIsTyVarTy ty = maybeToBool (tcGetTyVar_maybe ty)
795 -----------------------
796 tcSplitDFunTy :: Type -> ([TyVar], [PredType], Class, [Type])
797 -- Split the type of a dictionary function
799 = case tcSplitSigmaTy ty of { (tvs, theta, tau) ->
800 case tcSplitDFunHead tau of { (clas, tys) ->
801 (tvs, theta, clas, tys) }}
803 tcSplitDFunHead :: Type -> (Class, [Type])
805 = case tcSplitPredTy_maybe tau of
806 Just (ClassP clas tys) -> (clas, tys)
807 other -> panic "tcSplitDFunHead"
809 tcInstHeadTyNotSynonym :: Type -> Bool
810 -- Used in Haskell-98 mode, for the argument types of an instance head
811 -- These must not be type synonyms, but everywhere else type synonyms
812 -- are transparent, so we need a special function here
813 tcInstHeadTyNotSynonym ty
815 TyConApp tc tys -> not (isSynTyCon tc)
818 tcInstHeadTyAppAllTyVars :: Type -> Bool
819 -- Used in Haskell-98 mode, for the argument types of an instance head
820 -- These must be a constructor applied to type variable arguments
821 tcInstHeadTyAppAllTyVars ty
823 TyConApp _ tys -> ok tys
824 FunTy arg res -> ok [arg, res]
827 -- Check that all the types are type variables,
828 -- and that each is distinct
829 ok tys = equalLength tvs tys && hasNoDups tvs
831 tvs = mapCatMaybes get_tv tys
833 get_tv (TyVarTy tv) = Just tv -- through synonyms
834 get_tv other = Nothing
839 %************************************************************************
841 \subsection{Predicate types}
843 %************************************************************************
846 tcSplitPredTy_maybe :: Type -> Maybe PredType
847 -- Returns Just for predicates only
848 tcSplitPredTy_maybe ty | Just ty' <- tcView ty = tcSplitPredTy_maybe ty'
849 tcSplitPredTy_maybe (PredTy p) = Just p
850 tcSplitPredTy_maybe other = Nothing
852 predTyUnique :: PredType -> Unique
853 predTyUnique (IParam n _) = getUnique (ipNameName n)
854 predTyUnique (ClassP clas tys) = getUnique clas
855 predTyUnique (EqPred a b) = pprPanic "predTyUnique" (ppr (EqPred a b))
859 --------------------- Dictionary types ---------------------------------
862 mkClassPred clas tys = ClassP clas tys
864 isClassPred :: PredType -> Bool
865 isClassPred (ClassP clas tys) = True
866 isClassPred other = False
868 isTyVarClassPred (ClassP clas tys) = all tcIsTyVarTy tys
869 isTyVarClassPred other = False
871 getClassPredTys_maybe :: PredType -> Maybe (Class, [Type])
872 getClassPredTys_maybe (ClassP clas tys) = Just (clas, tys)
873 getClassPredTys_maybe _ = Nothing
875 getClassPredTys :: PredType -> (Class, [Type])
876 getClassPredTys (ClassP clas tys) = (clas, tys)
877 getClassPredTys other = panic "getClassPredTys"
879 mkDictTy :: Class -> [Type] -> Type
880 mkDictTy clas tys = mkPredTy (ClassP clas tys)
882 isDictTy :: Type -> Bool
883 isDictTy ty | Just ty' <- tcView ty = isDictTy ty'
884 isDictTy (PredTy p) = isClassPred p
885 isDictTy other = False
888 --------------------- Implicit parameters ---------------------------------
891 isIPPred :: PredType -> Bool
892 isIPPred (IParam _ _) = True
893 isIPPred other = False
895 isInheritablePred :: PredType -> Bool
896 -- Can be inherited by a context. For example, consider
897 -- f x = let g y = (?v, y+x)
898 -- in (g 3 with ?v = 8,
900 -- The point is that g's type must be quantifed over ?v:
901 -- g :: (?v :: a) => a -> a
902 -- but it doesn't need to be quantified over the Num a dictionary
903 -- which can be free in g's rhs, and shared by both calls to g
904 isInheritablePred (ClassP _ _) = True
905 isInheritablePred (EqPred _ _) = True
906 isInheritablePred other = False
909 --------------------- Equality predicates ---------------------------------
911 substEqSpec :: TvSubst -> [(TyVar,Type)] -> [(TcType,TcType)]
912 substEqSpec subst eq_spec = [ (substTyVar subst tv, substTy subst ty)
913 | (tv,ty) <- eq_spec]
916 --------------------- The stupid theta (sigh) ---------------------------------
919 dataConsStupidTheta :: [DataCon] -> ThetaType
920 -- Union the stupid thetas from all the specified constructors (non-empty)
921 -- All the constructors should have the same result type, modulo alpha conversion
922 -- The resulting ThetaType uses type variables from the *first* constructor in the list
924 -- It's here because it's used in MkId.mkRecordSelId, and in TcExpr
925 dataConsStupidTheta (con1:cons)
926 = nubBy tcEqPred all_preds
928 all_preds = dataConStupidTheta con1 ++ other_stupids
929 res_ty1 = dataConOrigResTy con1
930 other_stupids = [ substPred subst pred
932 , let (tvs, _, _, res_ty) = dataConSig con
933 Just subst = tcMatchTy (mkVarSet tvs) res_ty res_ty1
934 , pred <- dataConStupidTheta con ]
935 dataConsStupidTheta [] = panic "dataConsStupidTheta"
939 %************************************************************************
941 \subsection{Predicates}
943 %************************************************************************
945 isSigmaTy returns true of any qualified type. It doesn't *necessarily* have
947 f :: (?x::Int) => Int -> Int
950 isSigmaTy :: Type -> Bool
951 isSigmaTy ty | Just ty' <- tcView ty = isSigmaTy ty'
952 isSigmaTy (ForAllTy tyvar ty) = True
953 isSigmaTy (FunTy a b) = isPredTy a
956 isOverloadedTy :: Type -> Bool
957 isOverloadedTy ty | Just ty' <- tcView ty = isOverloadedTy ty'
958 isOverloadedTy (ForAllTy tyvar ty) = isOverloadedTy ty
959 isOverloadedTy (FunTy a b) = isPredTy a
960 isOverloadedTy _ = False
962 isPredTy :: Type -> Bool -- Belongs in TcType because it does
963 -- not look through newtypes, or predtypes (of course)
964 isPredTy ty | Just ty' <- tcView ty = isPredTy ty'
965 isPredTy (PredTy sty) = True
970 isFloatTy = is_tc floatTyConKey
971 isDoubleTy = is_tc doubleTyConKey
972 isIntegerTy = is_tc integerTyConKey
973 isIntTy = is_tc intTyConKey
974 isBoolTy = is_tc boolTyConKey
975 isUnitTy = is_tc unitTyConKey
976 isCharTy = is_tc charTyConKey
979 = case tcSplitTyConApp_maybe ty of
980 Just (tc, [arg_ty]) -> tc == listTyCon && isCharTy arg_ty
983 is_tc :: Unique -> Type -> Bool
984 -- Newtypes are opaque to this
985 is_tc uniq ty = case tcSplitTyConApp_maybe ty of
986 Just (tc, _) -> uniq == getUnique tc
991 -- NB: Currently used in places where we have already expanded type synonyms;
992 -- hence no 'coreView'. This could, however, be changed without breaking
994 isOpenSynTyConApp :: TcTauType -> Bool
995 isOpenSynTyConApp (TyConApp tc _) = isOpenSynTyCon tc
996 isOpenSynTyConApp _other = False
1000 %************************************************************************
1004 %************************************************************************
1007 deNoteType :: Type -> Type
1008 -- Remove all *outermost* type synonyms and other notes
1009 deNoteType ty | Just ty' <- tcView ty = deNoteType ty'
1014 tcTyVarsOfType :: Type -> TcTyVarSet
1015 -- Just the *TcTyVars* free in the type
1016 -- (Types.tyVarsOfTypes finds all free TyVars)
1017 tcTyVarsOfType (TyVarTy tv) = if isTcTyVar tv then unitVarSet tv
1019 tcTyVarsOfType (TyConApp tycon tys) = tcTyVarsOfTypes tys
1020 tcTyVarsOfType (PredTy sty) = tcTyVarsOfPred sty
1021 tcTyVarsOfType (FunTy arg res) = tcTyVarsOfType arg `unionVarSet` tcTyVarsOfType res
1022 tcTyVarsOfType (AppTy fun arg) = tcTyVarsOfType fun `unionVarSet` tcTyVarsOfType arg
1023 tcTyVarsOfType (ForAllTy tyvar ty) = (tcTyVarsOfType ty `delVarSet` tyvar)
1024 `unionVarSet` tcTyVarsOfTyVar tyvar
1025 -- We do sometimes quantify over skolem TcTyVars
1027 tcTyVarsOfTyVar :: TcTyVar -> TyVarSet
1028 tcTyVarsOfTyVar tv | isCoVar tv = tcTyVarsOfType (tyVarKind tv)
1029 | otherwise = emptyVarSet
1031 tcTyVarsOfTypes :: [Type] -> TyVarSet
1032 tcTyVarsOfTypes tys = foldr (unionVarSet.tcTyVarsOfType) emptyVarSet tys
1034 tcTyVarsOfPred :: PredType -> TyVarSet
1035 tcTyVarsOfPred (IParam _ ty) = tcTyVarsOfType ty
1036 tcTyVarsOfPred (ClassP _ tys) = tcTyVarsOfTypes tys
1037 tcTyVarsOfPred (EqPred ty1 ty2) = tcTyVarsOfType ty1 `unionVarSet` tcTyVarsOfType ty2
1040 Note [Silly type synonym]
1041 ~~~~~~~~~~~~~~~~~~~~~~~~~
1044 What are the free tyvars of (T x)? Empty, of course!
1045 Here's the example that Ralf Laemmel showed me:
1046 foo :: (forall a. C u a -> C u a) -> u
1047 mappend :: Monoid u => u -> u -> u
1049 bar :: Monoid u => u
1050 bar = foo (\t -> t `mappend` t)
1051 We have to generalise at the arg to f, and we don't
1052 want to capture the constraint (Monad (C u a)) because
1053 it appears to mention a. Pretty silly, but it was useful to him.
1055 exactTyVarsOfType is used by the type checker to figure out exactly
1056 which type variables are mentioned in a type. It's also used in the
1057 smart-app checking code --- see TcExpr.tcIdApp
1059 On the other hand, consider a *top-level* definition
1060 f = (\x -> x) :: T a -> T a
1061 If we don't abstract over 'a' it'll get fixed to GHC.Prim.Any, and then
1062 if we have an application like (f "x") we get a confusing error message
1063 involving Any. So the conclusion is this: when generalising
1064 - at top level use tyVarsOfType
1065 - in nested bindings use exactTyVarsOfType
1066 See Trac #1813 for example.
1069 exactTyVarsOfType :: TcType -> TyVarSet
1070 -- Find the free type variables (of any kind)
1071 -- but *expand* type synonyms. See Note [Silly type synonym] above.
1072 exactTyVarsOfType ty
1075 go ty | Just ty' <- tcView ty = go ty' -- This is the key line
1076 go (TyVarTy tv) = unitVarSet tv
1077 go (TyConApp tycon tys) = exactTyVarsOfTypes tys
1078 go (PredTy ty) = go_pred ty
1079 go (FunTy arg res) = go arg `unionVarSet` go res
1080 go (AppTy fun arg) = go fun `unionVarSet` go arg
1081 go (ForAllTy tyvar ty) = delVarSet (go ty) tyvar
1082 `unionVarSet` go_tv tyvar
1084 go_pred (IParam _ ty) = go ty
1085 go_pred (ClassP _ tys) = exactTyVarsOfTypes tys
1086 go_pred (EqPred ty1 ty2) = go ty1 `unionVarSet` go ty2
1088 go_tv tyvar | isCoVar tyvar = go (tyVarKind tyvar)
1089 | otherwise = emptyVarSet
1091 exactTyVarsOfTypes :: [TcType] -> TyVarSet
1092 exactTyVarsOfTypes tys = foldr (unionVarSet . exactTyVarsOfType) emptyVarSet tys
1095 Find the free tycons and classes of a type. This is used in the front
1096 end of the compiler.
1099 tyClsNamesOfType :: Type -> NameSet
1100 tyClsNamesOfType (TyVarTy tv) = emptyNameSet
1101 tyClsNamesOfType (TyConApp tycon tys) = unitNameSet (getName tycon) `unionNameSets` tyClsNamesOfTypes tys
1102 tyClsNamesOfType (PredTy (IParam n ty)) = tyClsNamesOfType ty
1103 tyClsNamesOfType (PredTy (ClassP cl tys)) = unitNameSet (getName cl) `unionNameSets` tyClsNamesOfTypes tys
1104 tyClsNamesOfType (PredTy (EqPred ty1 ty2)) = tyClsNamesOfType ty1 `unionNameSets` tyClsNamesOfType ty2
1105 tyClsNamesOfType (FunTy arg res) = tyClsNamesOfType arg `unionNameSets` tyClsNamesOfType res
1106 tyClsNamesOfType (AppTy fun arg) = tyClsNamesOfType fun `unionNameSets` tyClsNamesOfType arg
1107 tyClsNamesOfType (ForAllTy tyvar ty) = tyClsNamesOfType ty
1109 tyClsNamesOfTypes tys = foldr (unionNameSets . tyClsNamesOfType) emptyNameSet tys
1111 tyClsNamesOfDFunHead :: Type -> NameSet
1112 -- Find the free type constructors and classes
1113 -- of the head of the dfun instance type
1114 -- The 'dfun_head_type' is because of
1115 -- instance Foo a => Baz T where ...
1116 -- The decl is an orphan if Baz and T are both not locally defined,
1117 -- even if Foo *is* locally defined
1118 tyClsNamesOfDFunHead dfun_ty
1119 = case tcSplitSigmaTy dfun_ty of
1120 (tvs,_,head_ty) -> tyClsNamesOfType head_ty
1124 %************************************************************************
1126 \subsection[TysWiredIn-ext-type]{External types}
1128 %************************************************************************
1130 The compiler's foreign function interface supports the passing of a
1131 restricted set of types as arguments and results (the restricting factor
1135 tcSplitIOType_maybe :: Type -> Maybe (TyCon, Type, CoercionI)
1136 -- (isIOType t) returns Just (IO,t',co)
1137 -- if co : t ~ IO t'
1138 -- returns Nothing otherwise
1139 tcSplitIOType_maybe ty
1140 = case tcSplitTyConApp_maybe ty of
1141 -- This split absolutely has to be a tcSplit, because we must
1142 -- see the IO type; and it's a newtype which is transparent to splitTyConApp.
1144 Just (io_tycon, [io_res_ty])
1145 | io_tycon `hasKey` ioTyConKey
1146 -> Just (io_tycon, io_res_ty, IdCo)
1149 | not (isRecursiveTyCon tc)
1150 , Just (ty, co1) <- instNewTyCon_maybe tc tys
1151 -- Newtypes that require a coercion are ok
1152 -> case tcSplitIOType_maybe ty of
1154 Just (tc, ty', co2) -> Just (tc, ty', co1 `mkTransCoI` co2)
1158 isFFITy :: Type -> Bool
1159 -- True for any TyCon that can possibly be an arg or result of an FFI call
1160 isFFITy ty = checkRepTyCon legalFFITyCon ty
1162 isFFIArgumentTy :: DynFlags -> Safety -> Type -> Bool
1163 -- Checks for valid argument type for a 'foreign import'
1164 isFFIArgumentTy dflags safety ty
1165 = checkRepTyCon (legalOutgoingTyCon dflags safety) ty
1167 isFFIExternalTy :: Type -> Bool
1168 -- Types that are allowed as arguments of a 'foreign export'
1169 isFFIExternalTy ty = checkRepTyCon legalFEArgTyCon ty
1171 isFFIImportResultTy :: DynFlags -> Type -> Bool
1172 isFFIImportResultTy dflags ty
1173 = checkRepTyCon (legalFIResultTyCon dflags) ty
1175 isFFIExportResultTy :: Type -> Bool
1176 isFFIExportResultTy ty = checkRepTyCon legalFEResultTyCon ty
1178 isFFIDynArgumentTy :: Type -> Bool
1179 -- The argument type of a foreign import dynamic must be Ptr, FunPtr, Addr,
1180 -- or a newtype of either.
1181 isFFIDynArgumentTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1183 isFFIDynResultTy :: Type -> Bool
1184 -- The result type of a foreign export dynamic must be Ptr, FunPtr, Addr,
1185 -- or a newtype of either.
1186 isFFIDynResultTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1188 isFFILabelTy :: Type -> Bool
1189 -- The type of a foreign label must be Ptr, FunPtr, Addr,
1190 -- or a newtype of either.
1191 isFFILabelTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1193 isFFIDotnetTy :: DynFlags -> Type -> Bool
1194 isFFIDotnetTy dflags ty
1195 = checkRepTyCon (\ tc -> (legalFIResultTyCon dflags tc ||
1196 isFFIDotnetObjTy ty || isStringTy ty)) ty
1197 -- NB: isStringTy used to look through newtypes, but
1198 -- it no longer does so. May need to adjust isFFIDotNetTy
1199 -- if we do want to look through newtypes.
1202 = checkRepTyCon check_tc t_ty
1204 (_, t_ty) = tcSplitForAllTys ty
1205 check_tc tc = getName tc == objectTyConName
1207 toDNType :: Type -> DNType
1209 | isStringTy ty = DNString
1210 | isFFIDotnetObjTy ty = DNObject
1211 | Just (tc,argTys) <- tcSplitTyConApp_maybe ty
1212 = case lookup (getUnique tc) dn_assoc of
1215 | tc `hasKey` ioTyConKey -> toDNType (head argTys)
1216 | otherwise -> pprPanic ("toDNType: unsupported .NET type")
1217 (pprType ty <+> parens (hcat (map pprType argTys)) <+> ppr tc)
1218 | otherwise = panic "toDNType" -- Is this right?
1220 dn_assoc :: [ (Unique, DNType) ]
1221 dn_assoc = [ (unitTyConKey, DNUnit)
1222 , (intTyConKey, DNInt)
1223 , (int8TyConKey, DNInt8)
1224 , (int16TyConKey, DNInt16)
1225 , (int32TyConKey, DNInt32)
1226 , (int64TyConKey, DNInt64)
1227 , (wordTyConKey, DNInt)
1228 , (word8TyConKey, DNWord8)
1229 , (word16TyConKey, DNWord16)
1230 , (word32TyConKey, DNWord32)
1231 , (word64TyConKey, DNWord64)
1232 , (floatTyConKey, DNFloat)
1233 , (doubleTyConKey, DNDouble)
1234 , (ptrTyConKey, DNPtr)
1235 , (funPtrTyConKey, DNPtr)
1236 , (charTyConKey, DNChar)
1237 , (boolTyConKey, DNBool)
1240 checkRepTyCon :: (TyCon -> Bool) -> Type -> Bool
1241 -- Look through newtypes
1242 -- Non-recursive ones are transparent to splitTyConApp,
1243 -- but recursive ones aren't. Manuel had:
1244 -- newtype T = MkT (Ptr T)
1245 -- and wanted it to work...
1246 checkRepTyCon check_tc ty
1247 | Just (tc,_) <- splitTyConApp_maybe (repType ty) = check_tc tc
1250 checkRepTyConKey :: [Unique] -> Type -> Bool
1251 -- Like checkRepTyCon, but just looks at the TyCon key
1252 checkRepTyConKey keys
1253 = checkRepTyCon (\tc -> tyConUnique tc `elem` keys)
1256 ----------------------------------------------
1257 These chaps do the work; they are not exported
1258 ----------------------------------------------
1261 legalFEArgTyCon :: TyCon -> Bool
1263 -- It's illegal to make foreign exports that take unboxed
1264 -- arguments. The RTS API currently can't invoke such things. --SDM 7/2000
1265 = boxedMarshalableTyCon tc
1267 legalFIResultTyCon :: DynFlags -> TyCon -> Bool
1268 legalFIResultTyCon dflags tc
1269 | tc == unitTyCon = True
1270 | otherwise = marshalableTyCon dflags tc
1272 legalFEResultTyCon :: TyCon -> Bool
1273 legalFEResultTyCon tc
1274 | tc == unitTyCon = True
1275 | otherwise = boxedMarshalableTyCon tc
1277 legalOutgoingTyCon :: DynFlags -> Safety -> TyCon -> Bool
1278 -- Checks validity of types going from Haskell -> external world
1279 legalOutgoingTyCon dflags safety tc
1280 = marshalableTyCon dflags tc
1282 legalFFITyCon :: TyCon -> Bool
1283 -- True for any TyCon that can possibly be an arg or result of an FFI call
1285 = isUnLiftedTyCon tc || boxedMarshalableTyCon tc || tc == unitTyCon
1287 marshalableTyCon dflags tc
1288 = (dopt Opt_UnliftedFFITypes dflags
1289 && isUnLiftedTyCon tc
1290 && not (isUnboxedTupleTyCon tc)
1291 && case tyConPrimRep tc of -- Note [Marshalling VoidRep]
1294 || boxedMarshalableTyCon tc
1296 boxedMarshalableTyCon tc
1297 = getUnique tc `elem` [ intTyConKey, int8TyConKey, int16TyConKey
1298 , int32TyConKey, int64TyConKey
1299 , wordTyConKey, word8TyConKey, word16TyConKey
1300 , word32TyConKey, word64TyConKey
1301 , floatTyConKey, doubleTyConKey
1302 , ptrTyConKey, funPtrTyConKey
1309 Note [Marshalling VoidRep]
1310 ~~~~~~~~~~~~~~~~~~~~~~~~~~
1311 We don't treat State# (whose PrimRep is VoidRep) as marshalable.
1312 In turn that means you can't write
1313 foreign import foo :: Int -> State# RealWorld
1315 Reason: the back end falls over with panic "primRepHint:VoidRep";
1316 and there is no compelling reason to permit it