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"
174 %************************************************************************
178 %************************************************************************
180 The type checker divides the generic Type world into the
181 following more structured beasts:
183 sigma ::= forall tyvars. phi
184 -- A sigma type is a qualified type
186 -- Note that even if 'tyvars' is empty, theta
187 -- may not be: e.g. (?x::Int) => Int
189 -- Note that 'sigma' is in prenex form:
190 -- all the foralls are at the front.
191 -- A 'phi' type has no foralls to the right of
199 -- A 'tau' type has no quantification anywhere
200 -- Note that the args of a type constructor must be taus
202 | tycon tau_1 .. tau_n
206 -- In all cases, a (saturated) type synonym application is legal,
207 -- provided it expands to the required form.
210 type TcTyVar = TyVar -- Used only during type inference
211 type TcType = Type -- A TcType can have mutable type variables
212 -- Invariant on ForAllTy in TcTypes:
214 -- a cannot occur inside a MutTyVar in T; that is,
215 -- T is "flattened" before quantifying over a
217 -- These types do not have boxy type variables in them
218 type TcPredType = PredType
219 type TcThetaType = ThetaType
220 type TcSigmaType = TcType
221 type TcRhoType = TcType
222 type TcTauType = TcType
224 type TcTyVarSet = TyVarSet
226 -- These types may have boxy type variables in them
227 type BoxyTyVar = TcTyVar
228 type BoxyRhoType = TcType
229 type BoxyThetaType = TcThetaType
230 type BoxySigmaType = TcType
231 type BoxyType = TcType
235 %************************************************************************
237 \subsection{TyVarDetails}
239 %************************************************************************
241 TyVarDetails gives extra info about type variables, used during type
242 checking. It's attached to mutable type variables only.
243 It's knot-tied back to Var.lhs. There is no reason in principle
244 why Var.lhs shouldn't actually have the definition, but it "belongs" here.
247 Note [Signature skolems]
248 ~~~~~~~~~~~~~~~~~~~~~~~~
253 (x,y,z) = ([y,z], z, head x)
255 Here, x and y have type sigs, which go into the environment. We used to
256 instantiate their types with skolem constants, and push those types into
257 the RHS, so we'd typecheck the RHS with type
259 where a*, b* are skolem constants, and c is an ordinary meta type varible.
261 The trouble is that the occurrences of z in the RHS force a* and b* to
262 be the *same*, so we can't make them into skolem constants that don't unify
263 with each other. Alas.
265 One solution would be insist that in the above defn the programmer uses
266 the same type variable in both type signatures. But that takes explanation.
268 The alternative (currently implemented) is to have a special kind of skolem
269 constant, SigTv, which can unify with other SigTvs. These are *not* treated
270 as righd for the purposes of GADTs. And they are used *only* for pattern
271 bindings and mutually recursive function bindings. See the function
272 TcBinds.tcInstSig, and its use_skols parameter.
276 -- A TyVarDetails is inside a TyVar
278 = SkolemTv SkolemInfo -- A skolem constant
280 | MetaTv BoxInfo (IORef MetaDetails)
283 = BoxTv -- The contents is a (non-boxy) sigma-type
284 -- That is, this MetaTv is a "box"
286 | TauTv -- The contents is a (non-boxy) tau-type
287 -- That is, this MetaTv is an ordinary unification variable
289 | SigTv SkolemInfo -- A variant of TauTv, except that it should not be
290 -- unified with a type, only with a type variable
291 -- SigTvs are only distinguished to improve error messages
292 -- see Note [Signature skolems]
293 -- The MetaDetails, if filled in, will
294 -- always be another SigTv or a SkolemTv
297 -- A TauTv is always filled in with a tau-type, which
298 -- never contains any BoxTvs, nor any ForAlls
300 -- However, a BoxTv can contain a type that contains further BoxTvs
301 -- Notably, when typechecking an explicit list, say [e1,e2], with
302 -- expected type being a box b1, we fill in b1 with (List b2), where
303 -- b2 is another (currently empty) box.
306 = Flexi -- Flexi type variables unify to become
309 | Indirect TcType -- INVARIANT:
310 -- For a BoxTv, this type must be non-boxy
311 -- For a TauTv, this type must be a tau-type
313 -- Generally speaking, SkolemInfo should not contain location info
314 -- that is contained in the Name of the tyvar with this SkolemInfo
316 = SigSkol UserTypeCtxt -- A skolem that is created by instantiating
317 -- a programmer-supplied type signature
318 -- Location of the binding site is on the TyVar
320 -- The rest are for non-scoped skolems
321 | ClsSkol Class -- Bound at a class decl
322 | InstSkol -- Bound at an instance decl
323 | FamInstSkol -- Bound at a family instance decl
324 | PatSkol DataCon -- An existential type variable bound by a pattern for
325 -- a data constructor with an existential type. E.g.
326 -- data T = forall a. Eq a => MkT a
328 -- The pattern MkT x will allocate an existential type
330 | ArrowSkol -- An arrow form (see TcArrows)
332 | RuleSkol RuleName -- The LHS of a RULE
333 | GenSkol [TcTyVar] -- Bound when doing a subsumption check for
334 TcType -- (forall tvs. ty)
336 | RuntimeUnkSkol -- a type variable used to represent an unknown
337 -- runtime type (used in the GHCi debugger)
339 | UnkSkol -- Unhelpful info (until I improve it)
341 -------------------------------------
342 -- UserTypeCtxt describes the places where a
343 -- programmer-written type signature can occur
344 -- Like SkolemInfo, no location info
346 = FunSigCtxt Name -- Function type signature
347 -- Also used for types in SPECIALISE pragmas
348 | ExprSigCtxt -- Expression type signature
349 | ConArgCtxt Name -- Data constructor argument
350 | TySynCtxt Name -- RHS of a type synonym decl
351 | GenPatCtxt -- Pattern in generic decl
352 -- f{| a+b |} (Inl x) = ...
353 | LamPatSigCtxt -- Type sig in lambda pattern
355 | BindPatSigCtxt -- Type sig in pattern binding pattern
357 | ResSigCtxt -- Result type sig
359 | ForSigCtxt Name -- Foreign inport or export signature
360 | DefaultDeclCtxt -- Types in a default declaration
361 | SpecInstCtxt -- SPECIALISE instance pragma
363 -- Notes re TySynCtxt
364 -- We allow type synonyms that aren't types; e.g. type List = []
366 -- If the RHS mentions tyvars that aren't in scope, we'll
367 -- quantify over them:
368 -- e.g. type T = a->a
369 -- will become type T = forall a. a->a
371 -- With gla-exts that's right, but for H98 we should complain.
373 ---------------------------------
376 mkKindName :: Unique -> Name
377 mkKindName unique = mkSystemName unique kind_var_occ
379 kindVarRef :: KindVar -> IORef MetaDetails
381 ASSERT ( isTcTyVar tc )
382 case tcTyVarDetails tc of
383 MetaTv TauTv ref -> ref
384 other -> pprPanic "kindVarRef" (ppr tc)
386 mkKindVar :: Unique -> IORef MetaDetails -> KindVar
388 = mkTcTyVar (mkKindName u)
389 tySuperKind -- not sure this is right,
390 -- do we need kind vars for
394 kind_var_occ :: OccName -- Just one for all KindVars
395 -- They may be jiggled by tidying
396 kind_var_occ = mkOccName tvName "k"
399 %************************************************************************
403 %************************************************************************
406 pprTcTyVarDetails :: TcTyVarDetails -> SDoc
408 pprTcTyVarDetails (SkolemTv _) = ptext (sLit "sk")
409 pprTcTyVarDetails (MetaTv BoxTv _) = ptext (sLit "box")
410 pprTcTyVarDetails (MetaTv TauTv _) = ptext (sLit "tau")
411 pprTcTyVarDetails (MetaTv (SigTv _) _) = ptext (sLit "sig")
413 pprUserTypeCtxt :: UserTypeCtxt -> SDoc
414 pprUserTypeCtxt (FunSigCtxt n) = ptext (sLit "the type signature for") <+> quotes (ppr n)
415 pprUserTypeCtxt ExprSigCtxt = ptext (sLit "an expression type signature")
416 pprUserTypeCtxt (ConArgCtxt c) = ptext (sLit "the type of the constructor") <+> quotes (ppr c)
417 pprUserTypeCtxt (TySynCtxt c) = ptext (sLit "the RHS of the type synonym") <+> quotes (ppr c)
418 pprUserTypeCtxt GenPatCtxt = ptext (sLit "the type pattern of a generic definition")
419 pprUserTypeCtxt LamPatSigCtxt = ptext (sLit "a pattern type signature")
420 pprUserTypeCtxt BindPatSigCtxt = ptext (sLit "a pattern type signature")
421 pprUserTypeCtxt ResSigCtxt = ptext (sLit "a result type signature")
422 pprUserTypeCtxt (ForSigCtxt n) = ptext (sLit "the foreign declaration for") <+> quotes (ppr n)
423 pprUserTypeCtxt DefaultDeclCtxt = ptext (sLit "a type in a `default' declaration")
424 pprUserTypeCtxt SpecInstCtxt = ptext (sLit "a SPECIALISE instance pragma")
427 --------------------------------
428 tidySkolemTyVar :: TidyEnv -> TcTyVar -> (TidyEnv, TcTyVar)
429 -- Tidy the type inside a GenSkol, preparatory to printing it
430 tidySkolemTyVar env tv
431 = ASSERT( isSkolemTyVar tv || isSigTyVar tv )
432 (env1, mkTcTyVar (tyVarName tv) (tyVarKind tv) info1)
434 (env1, info1) = case tcTyVarDetails tv of
435 SkolemTv info -> (env1, SkolemTv info')
437 (env1, info') = tidy_skol_info env info
438 MetaTv (SigTv info) box -> (env1, MetaTv (SigTv info') box)
440 (env1, info') = tidy_skol_info env info
443 tidy_skol_info env (GenSkol tvs ty) = (env2, GenSkol tvs1 ty1)
445 (env1, tvs1) = tidyOpenTyVars env tvs
446 (env2, ty1) = tidyOpenType env1 ty
447 tidy_skol_info env info = (env, info)
449 pprSkolTvBinding :: TcTyVar -> SDoc
450 -- Print info about the binding of a skolem tyvar,
451 -- or nothing if we don't have anything useful to say
453 = ASSERT ( isTcTyVar tv )
454 quotes (ppr tv) <+> ppr_details (tcTyVarDetails tv)
456 ppr_details (MetaTv TauTv _) = ptext (sLit "is a meta type variable")
457 ppr_details (MetaTv BoxTv _) = ptext (sLit "is a boxy type variable")
458 ppr_details (MetaTv (SigTv info) _) = ppr_skol info
459 ppr_details (SkolemTv info) = ppr_skol info
461 ppr_skol UnkSkol = ptext (sLit "is an unknown type variable") -- Unhelpful
462 ppr_skol RuntimeUnkSkol = ptext (sLit "is an unknown runtime type")
463 ppr_skol info = sep [ptext (sLit "is a rigid type variable bound by"),
464 sep [pprSkolInfo info,
465 nest 2 (ptext (sLit "at") <+> ppr (getSrcLoc tv))]]
467 pprSkolInfo :: SkolemInfo -> SDoc
468 pprSkolInfo (SigSkol ctxt) = pprUserTypeCtxt ctxt
469 pprSkolInfo (ClsSkol cls) = ptext (sLit "the class declaration for") <+> quotes (ppr cls)
470 pprSkolInfo InstSkol = ptext (sLit "the instance declaration")
471 pprSkolInfo FamInstSkol = ptext (sLit "the family instance declaration")
472 pprSkolInfo (RuleSkol name) = ptext (sLit "the RULE") <+> doubleQuotes (ftext name)
473 pprSkolInfo ArrowSkol = ptext (sLit "the arrow form")
474 pprSkolInfo (PatSkol dc) = sep [ptext (sLit "the constructor") <+> quotes (ppr dc)]
475 pprSkolInfo (GenSkol tvs ty) = sep [ptext (sLit "the polymorphic type"),
476 nest 2 (quotes (ppr (mkForAllTys tvs ty)))]
479 -- For type variables the others are dealt with by pprSkolTvBinding.
480 -- For Insts, these cases should not happen
481 pprSkolInfo UnkSkol = panic "UnkSkol"
482 pprSkolInfo RuntimeUnkSkol = panic "RuntimeUnkSkol"
484 instance Outputable MetaDetails where
485 ppr Flexi = ptext (sLit "Flexi")
486 ppr (Indirect ty) = ptext (sLit "Indirect") <+> ppr ty
490 %************************************************************************
494 %************************************************************************
497 isImmutableTyVar :: TyVar -> Bool
500 | isTcTyVar tv = isSkolemTyVar tv
503 isTyConableTyVar, isSkolemTyVar, isExistentialTyVar,
504 isBoxyTyVar, isMetaTyVar :: TcTyVar -> Bool
507 -- True of a meta-type variable that can be filled in
508 -- with a type constructor application; in particular,
510 = ASSERT( isTcTyVar tv)
511 case tcTyVarDetails tv of
512 MetaTv BoxTv _ -> True
513 MetaTv TauTv _ -> True
514 MetaTv (SigTv {}) _ -> False
518 = ASSERT( isTcTyVar tv )
519 case tcTyVarDetails tv of
523 isExistentialTyVar tv -- Existential type variable, bound by a pattern
524 = ASSERT( isTcTyVar tv )
525 case tcTyVarDetails tv of
526 SkolemTv (PatSkol {}) -> True
530 = ASSERT2( isTcTyVar tv, ppr tv )
531 case tcTyVarDetails tv of
536 = ASSERT( isTcTyVar tv )
537 case tcTyVarDetails tv of
538 MetaTv BoxTv _ -> True
542 = ASSERT( isTcTyVar tv )
543 case tcTyVarDetails tv of
544 MetaTv (SigTv _) _ -> True
547 metaTvRef :: TyVar -> IORef MetaDetails
549 = ASSERT2( isTcTyVar tv, ppr tv )
550 case tcTyVarDetails tv of
552 other -> pprPanic "metaTvRef" (ppr tv)
554 isFlexi, isIndirect :: MetaDetails -> Bool
556 isFlexi other = False
558 isIndirect (Indirect _) = True
559 isIndirect other = False
561 isRuntimeUnk :: TyVar -> Bool
562 isRuntimeUnk x | isTcTyVar x
563 , SkolemTv RuntimeUnkSkol <- tcTyVarDetails x = True
566 isUnk :: TyVar -> Bool
567 isUnk x | isTcTyVar x
568 , SkolemTv UnkSkol <- tcTyVarDetails x = True
573 %************************************************************************
575 \subsection{Tau, sigma and rho}
577 %************************************************************************
580 mkSigmaTy :: [TyVar] -> [PredType] -> Type -> Type
581 mkSigmaTy tyvars theta tau = mkForAllTys tyvars (mkPhiTy theta tau)
583 mkPhiTy :: [PredType] -> Type -> Type
584 mkPhiTy theta ty = foldr (\p r -> mkFunTy (mkPredTy p) r) ty theta
587 @isTauTy@ tests for nested for-alls. It should not be called on a boxy type.
590 isTauTy :: Type -> Bool
591 isTauTy ty | Just ty' <- tcView ty = isTauTy ty'
592 isTauTy (TyVarTy tv) = ASSERT( not (isTcTyVar tv && isBoxyTyVar tv) )
594 isTauTy (TyConApp tc tys) = all isTauTy tys && isTauTyCon tc
595 isTauTy (AppTy a b) = isTauTy a && isTauTy b
596 isTauTy (FunTy a b) = isTauTy a && isTauTy b
597 isTauTy (PredTy p) = True -- Don't look through source types
598 isTauTy other = False
601 isTauTyCon :: TyCon -> Bool
602 -- Returns False for type synonyms whose expansion is a polytype
604 | isClosedSynTyCon tc = isTauTy (snd (synTyConDefn tc))
608 isBoxyTy :: TcType -> Bool
609 isBoxyTy ty = any isBoxyTyVar (varSetElems (tcTyVarsOfType ty))
611 isRigidTy :: TcType -> Bool
612 -- A type is rigid if it has no meta type variables in it
613 isRigidTy ty = all isImmutableTyVar (varSetElems (tcTyVarsOfType ty))
615 isRefineableTy :: TcType -> (Bool,Bool)
616 -- A type should have type refinements applied to it if it has
617 -- free type variables, and they are all rigid
618 isRefineableTy ty = (null tc_tvs, all isImmutableTyVar tc_tvs)
620 tc_tvs = varSetElems (tcTyVarsOfType ty)
622 isRefineablePred :: TcPredType -> Bool
623 isRefineablePred pred = not (null tc_tvs) && all isImmutableTyVar tc_tvs
625 tc_tvs = varSetElems (tcTyVarsOfPred pred)
628 getDFunTyKey :: Type -> OccName -- Get some string from a type, to be used to
629 -- construct a dictionary function name
630 getDFunTyKey ty | Just ty' <- tcView ty = getDFunTyKey ty'
631 getDFunTyKey (TyVarTy tv) = getOccName tv
632 getDFunTyKey (TyConApp tc _) = getOccName tc
633 getDFunTyKey (AppTy fun _) = getDFunTyKey fun
634 getDFunTyKey (FunTy arg _) = getOccName funTyCon
635 getDFunTyKey (ForAllTy _ t) = getDFunTyKey t
636 getDFunTyKey ty = pprPanic "getDFunTyKey" (pprType ty)
637 -- PredTy shouldn't happen
641 %************************************************************************
643 \subsection{Expanding and splitting}
645 %************************************************************************
647 These tcSplit functions are like their non-Tc analogues, but
648 a) they do not look through newtypes
649 b) they do not look through PredTys
650 c) [future] they ignore usage-type annotations
652 However, they are non-monadic and do not follow through mutable type
653 variables. It's up to you to make sure this doesn't matter.
656 tcSplitForAllTys :: Type -> ([TyVar], Type)
657 tcSplitForAllTys ty = split ty ty []
659 split orig_ty ty tvs | Just ty' <- tcView ty = split orig_ty ty' tvs
660 split orig_ty (ForAllTy tv ty) tvs
661 | not (isCoVar tv) = split ty ty (tv:tvs)
662 split orig_ty t tvs = (reverse tvs, orig_ty)
664 tcIsForAllTy ty | Just ty' <- tcView ty = tcIsForAllTy ty'
665 tcIsForAllTy (ForAllTy tv ty) = not (isCoVar tv)
666 tcIsForAllTy t = False
668 tcSplitPhiTy :: Type -> (ThetaType, Type)
669 tcSplitPhiTy ty = split ty ty []
671 split orig_ty ty tvs | Just ty' <- tcView ty = split orig_ty ty' tvs
673 split orig_ty (ForAllTy tv ty) ts
674 | isCoVar tv = split ty ty (coVarPred tv : ts)
675 split orig_ty (FunTy arg res) ts
676 | Just p <- tcSplitPredTy_maybe arg = split res res (p:ts)
677 split orig_ty ty ts = (reverse ts, orig_ty)
679 tcSplitSigmaTy :: Type -> ([TyVar], ThetaType, Type)
680 tcSplitSigmaTy ty = case tcSplitForAllTys ty of
681 (tvs, rho) -> case tcSplitPhiTy rho of
682 (theta, tau) -> (tvs, theta, tau)
684 -----------------------
687 -> ( [([TyVar], ThetaType)], -- forall as.C => forall bs.D
688 TcSigmaType) -- The rest of the type
690 -- We need a loop here because we are now prepared to entertain
692 -- f:: forall a. Eq a => forall b. Baz b => tau
693 -- We want to instantiate this to
694 -- f2::tau {f2 = f1 b (Baz b), f1 = f a (Eq a)}
696 tcMultiSplitSigmaTy sigma
697 = case (tcSplitSigmaTy sigma) of
698 ([],[],ty) -> ([], sigma)
699 (tvs, theta, ty) -> case tcMultiSplitSigmaTy ty of
700 (pairs, rest) -> ((tvs,theta):pairs, rest)
702 -----------------------
703 tcTyConAppTyCon :: Type -> TyCon
704 tcTyConAppTyCon ty = case tcSplitTyConApp_maybe ty of
706 Nothing -> pprPanic "tcTyConAppTyCon" (pprType ty)
708 tcTyConAppArgs :: Type -> [Type]
709 tcTyConAppArgs ty = case tcSplitTyConApp_maybe ty of
710 Just (_, args) -> args
711 Nothing -> pprPanic "tcTyConAppArgs" (pprType ty)
713 tcSplitTyConApp :: Type -> (TyCon, [Type])
714 tcSplitTyConApp ty = case tcSplitTyConApp_maybe ty of
716 Nothing -> pprPanic "tcSplitTyConApp" (pprType ty)
718 tcSplitTyConApp_maybe :: Type -> Maybe (TyCon, [Type])
719 tcSplitTyConApp_maybe ty | Just ty' <- tcView ty = tcSplitTyConApp_maybe ty'
720 tcSplitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
721 tcSplitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res])
722 -- Newtypes are opaque, so they may be split
723 -- However, predicates are not treated
724 -- as tycon applications by the type checker
725 tcSplitTyConApp_maybe other = Nothing
727 -----------------------
728 tcSplitFunTys :: Type -> ([Type], Type)
729 tcSplitFunTys ty = case tcSplitFunTy_maybe ty of
731 Just (arg,res) -> (arg:args, res')
733 (args,res') = tcSplitFunTys res
735 tcSplitFunTy_maybe :: Type -> Maybe (Type, Type)
736 tcSplitFunTy_maybe ty | Just ty' <- tcView ty = tcSplitFunTy_maybe ty'
737 tcSplitFunTy_maybe (FunTy arg res) | not (isPredTy arg) = Just (arg, res)
738 tcSplitFunTy_maybe other = Nothing
739 -- Note the (not (isPredTy arg)) guard
740 -- Consider (?x::Int) => Bool
741 -- We don't want to treat this as a function type!
742 -- A concrete example is test tc230:
743 -- f :: () -> (?p :: ()) => () -> ()
749 -> Arity -- N: Number of desired args
750 -> ([TcSigmaType], -- Arg types (N or fewer)
751 TcSigmaType) -- The rest of the type
753 tcSplitFunTysN ty n_args
756 | Just (arg,res) <- tcSplitFunTy_maybe ty
757 = case tcSplitFunTysN res (n_args - 1) of
758 (args, res) -> (arg:args, res)
762 tcSplitFunTy ty = expectJust "tcSplitFunTy" (tcSplitFunTy_maybe ty)
763 tcFunArgTy ty = fst (tcSplitFunTy ty)
764 tcFunResultTy ty = snd (tcSplitFunTy ty)
766 -----------------------
767 tcSplitAppTy_maybe :: Type -> Maybe (Type, Type)
768 tcSplitAppTy_maybe ty | Just ty' <- tcView ty = tcSplitAppTy_maybe ty'
769 tcSplitAppTy_maybe ty = repSplitAppTy_maybe ty
771 tcSplitAppTy :: Type -> (Type, Type)
772 tcSplitAppTy ty = case tcSplitAppTy_maybe ty of
774 Nothing -> pprPanic "tcSplitAppTy" (pprType ty)
776 tcSplitAppTys :: Type -> (Type, [Type])
780 go ty args = case tcSplitAppTy_maybe ty of
781 Just (ty', arg) -> go ty' (arg:args)
784 -----------------------
785 tcGetTyVar_maybe :: Type -> Maybe TyVar
786 tcGetTyVar_maybe ty | Just ty' <- tcView ty = tcGetTyVar_maybe ty'
787 tcGetTyVar_maybe (TyVarTy tv) = Just tv
788 tcGetTyVar_maybe other = Nothing
790 tcGetTyVar :: String -> Type -> TyVar
791 tcGetTyVar msg ty = expectJust msg (tcGetTyVar_maybe ty)
793 tcIsTyVarTy :: Type -> Bool
794 tcIsTyVarTy ty = maybeToBool (tcGetTyVar_maybe ty)
796 -----------------------
797 tcSplitDFunTy :: Type -> ([TyVar], [PredType], Class, [Type])
798 -- Split the type of a dictionary function
800 = case tcSplitSigmaTy ty of { (tvs, theta, tau) ->
801 case tcSplitDFunHead tau of { (clas, tys) ->
802 (tvs, theta, clas, tys) }}
804 tcSplitDFunHead :: Type -> (Class, [Type])
806 = case tcSplitPredTy_maybe tau of
807 Just (ClassP clas tys) -> (clas, tys)
808 other -> panic "tcSplitDFunHead"
810 tcInstHeadTyNotSynonym :: Type -> Bool
811 -- Used in Haskell-98 mode, for the argument types of an instance head
812 -- These must not be type synonyms, but everywhere else type synonyms
813 -- are transparent, so we need a special function here
814 tcInstHeadTyNotSynonym ty
816 TyConApp tc tys -> not (isSynTyCon tc)
819 tcInstHeadTyAppAllTyVars :: Type -> Bool
820 -- Used in Haskell-98 mode, for the argument types of an instance head
821 -- These must be a constructor applied to type variable arguments
822 tcInstHeadTyAppAllTyVars ty
824 TyConApp _ tys -> ok tys
825 FunTy arg res -> ok [arg, res]
828 -- Check that all the types are type variables,
829 -- and that each is distinct
830 ok tys = equalLength tvs tys && hasNoDups tvs
832 tvs = mapCatMaybes get_tv tys
834 get_tv (TyVarTy tv) = Just tv -- through synonyms
835 get_tv other = Nothing
840 %************************************************************************
842 \subsection{Predicate types}
844 %************************************************************************
847 tcSplitPredTy_maybe :: Type -> Maybe PredType
848 -- Returns Just for predicates only
849 tcSplitPredTy_maybe ty | Just ty' <- tcView ty = tcSplitPredTy_maybe ty'
850 tcSplitPredTy_maybe (PredTy p) = Just p
851 tcSplitPredTy_maybe other = Nothing
853 predTyUnique :: PredType -> Unique
854 predTyUnique (IParam n _) = getUnique (ipNameName n)
855 predTyUnique (ClassP clas tys) = getUnique clas
856 predTyUnique (EqPred a b) = pprPanic "predTyUnique" (ppr (EqPred a b))
860 --------------------- Dictionary types ---------------------------------
863 mkClassPred clas tys = ClassP clas tys
865 isClassPred :: PredType -> Bool
866 isClassPred (ClassP clas tys) = True
867 isClassPred other = False
869 isTyVarClassPred (ClassP clas tys) = all tcIsTyVarTy tys
870 isTyVarClassPred other = False
872 getClassPredTys_maybe :: PredType -> Maybe (Class, [Type])
873 getClassPredTys_maybe (ClassP clas tys) = Just (clas, tys)
874 getClassPredTys_maybe _ = Nothing
876 getClassPredTys :: PredType -> (Class, [Type])
877 getClassPredTys (ClassP clas tys) = (clas, tys)
878 getClassPredTys other = panic "getClassPredTys"
880 mkDictTy :: Class -> [Type] -> Type
881 mkDictTy clas tys = mkPredTy (ClassP clas tys)
883 isDictTy :: Type -> Bool
884 isDictTy ty | Just ty' <- tcView ty = isDictTy ty'
885 isDictTy (PredTy p) = isClassPred p
886 isDictTy other = False
889 --------------------- Implicit parameters ---------------------------------
892 isIPPred :: PredType -> Bool
893 isIPPred (IParam _ _) = True
894 isIPPred other = False
896 isInheritablePred :: PredType -> Bool
897 -- Can be inherited by a context. For example, consider
898 -- f x = let g y = (?v, y+x)
899 -- in (g 3 with ?v = 8,
901 -- The point is that g's type must be quantifed over ?v:
902 -- g :: (?v :: a) => a -> a
903 -- but it doesn't need to be quantified over the Num a dictionary
904 -- which can be free in g's rhs, and shared by both calls to g
905 isInheritablePred (ClassP _ _) = True
906 isInheritablePred (EqPred _ _) = True
907 isInheritablePred other = False
910 --------------------- Equality predicates ---------------------------------
912 substEqSpec :: TvSubst -> [(TyVar,Type)] -> [(TcType,TcType)]
913 substEqSpec subst eq_spec = [ (substTyVar subst tv, substTy subst ty)
914 | (tv,ty) <- eq_spec]
917 --------------------- The stupid theta (sigh) ---------------------------------
920 dataConsStupidTheta :: [DataCon] -> ThetaType
921 -- Union the stupid thetas from all the specified constructors (non-empty)
922 -- All the constructors should have the same result type, modulo alpha conversion
923 -- The resulting ThetaType uses type variables from the *first* constructor in the list
925 -- It's here because it's used in MkId.mkRecordSelId, and in TcExpr
926 dataConsStupidTheta (con1:cons)
927 = nubBy tcEqPred all_preds
929 all_preds = dataConStupidTheta con1 ++ other_stupids
930 res_ty1 = dataConOrigResTy con1
931 other_stupids = [ substPred subst pred
933 , let (tvs, _, _, res_ty) = dataConSig con
934 Just subst = tcMatchTy (mkVarSet tvs) res_ty res_ty1
935 , pred <- dataConStupidTheta con ]
936 dataConsStupidTheta [] = panic "dataConsStupidTheta"
940 %************************************************************************
942 \subsection{Predicates}
944 %************************************************************************
946 isSigmaTy returns true of any qualified type. It doesn't *necessarily* have
948 f :: (?x::Int) => Int -> Int
951 isSigmaTy :: Type -> Bool
952 isSigmaTy ty | Just ty' <- tcView ty = isSigmaTy ty'
953 isSigmaTy (ForAllTy tyvar ty) = True
954 isSigmaTy (FunTy a b) = isPredTy a
957 isOverloadedTy :: Type -> Bool
958 isOverloadedTy ty | Just ty' <- tcView ty = isOverloadedTy ty'
959 isOverloadedTy (ForAllTy tyvar ty) = isOverloadedTy ty
960 isOverloadedTy (FunTy a b) = isPredTy a
961 isOverloadedTy _ = False
963 isPredTy :: Type -> Bool -- Belongs in TcType because it does
964 -- not look through newtypes, or predtypes (of course)
965 isPredTy ty | Just ty' <- tcView ty = isPredTy ty'
966 isPredTy (PredTy sty) = True
971 isFloatTy = is_tc floatTyConKey
972 isDoubleTy = is_tc doubleTyConKey
973 isIntegerTy = is_tc integerTyConKey
974 isIntTy = is_tc intTyConKey
975 isBoolTy = is_tc boolTyConKey
976 isUnitTy = is_tc unitTyConKey
977 isCharTy = is_tc charTyConKey
980 = case tcSplitTyConApp_maybe ty of
981 Just (tc, [arg_ty]) -> tc == listTyCon && isCharTy arg_ty
984 is_tc :: Unique -> Type -> Bool
985 -- Newtypes are opaque to this
986 is_tc uniq ty = case tcSplitTyConApp_maybe ty of
987 Just (tc, _) -> uniq == getUnique tc
992 -- NB: Currently used in places where we have already expanded type synonyms;
993 -- hence no 'coreView'. This could, however, be changed without breaking
995 isOpenSynTyConApp :: TcTauType -> Bool
996 isOpenSynTyConApp (TyConApp tc _) = isOpenSynTyCon tc
997 isOpenSynTyConApp _other = False
1001 %************************************************************************
1005 %************************************************************************
1008 deNoteType :: Type -> Type
1009 -- Remove all *outermost* type synonyms and other notes
1010 deNoteType ty | Just ty' <- tcView ty = deNoteType ty'
1015 tcTyVarsOfType :: Type -> TcTyVarSet
1016 -- Just the *TcTyVars* free in the type
1017 -- (Types.tyVarsOfTypes finds all free TyVars)
1018 tcTyVarsOfType (TyVarTy tv) = if isTcTyVar tv then unitVarSet tv
1020 tcTyVarsOfType (TyConApp tycon tys) = tcTyVarsOfTypes tys
1021 tcTyVarsOfType (PredTy sty) = tcTyVarsOfPred sty
1022 tcTyVarsOfType (FunTy arg res) = tcTyVarsOfType arg `unionVarSet` tcTyVarsOfType res
1023 tcTyVarsOfType (AppTy fun arg) = tcTyVarsOfType fun `unionVarSet` tcTyVarsOfType arg
1024 tcTyVarsOfType (ForAllTy tyvar ty) = (tcTyVarsOfType ty `delVarSet` tyvar)
1025 `unionVarSet` tcTyVarsOfTyVar tyvar
1026 -- We do sometimes quantify over skolem TcTyVars
1028 tcTyVarsOfTyVar :: TcTyVar -> TyVarSet
1029 tcTyVarsOfTyVar tv | isCoVar tv = tcTyVarsOfType (tyVarKind tv)
1030 | otherwise = emptyVarSet
1032 tcTyVarsOfTypes :: [Type] -> TyVarSet
1033 tcTyVarsOfTypes tys = foldr (unionVarSet.tcTyVarsOfType) emptyVarSet tys
1035 tcTyVarsOfPred :: PredType -> TyVarSet
1036 tcTyVarsOfPred (IParam _ ty) = tcTyVarsOfType ty
1037 tcTyVarsOfPred (ClassP _ tys) = tcTyVarsOfTypes tys
1038 tcTyVarsOfPred (EqPred ty1 ty2) = tcTyVarsOfType ty1 `unionVarSet` tcTyVarsOfType ty2
1041 Note [Silly type synonym]
1042 ~~~~~~~~~~~~~~~~~~~~~~~~~
1045 What are the free tyvars of (T x)? Empty, of course!
1046 Here's the example that Ralf Laemmel showed me:
1047 foo :: (forall a. C u a -> C u a) -> u
1048 mappend :: Monoid u => u -> u -> u
1050 bar :: Monoid u => u
1051 bar = foo (\t -> t `mappend` t)
1052 We have to generalise at the arg to f, and we don't
1053 want to capture the constraint (Monad (C u a)) because
1054 it appears to mention a. Pretty silly, but it was useful to him.
1056 exactTyVarsOfType is used by the type checker to figure out exactly
1057 which type variables are mentioned in a type. It's also used in the
1058 smart-app checking code --- see TcExpr.tcIdApp
1060 On the other hand, consider a *top-level* definition
1061 f = (\x -> x) :: T a -> T a
1062 If we don't abstract over 'a' it'll get fixed to GHC.Prim.Any, and then
1063 if we have an application like (f "x") we get a confusing error message
1064 involving Any. So the conclusion is this: when generalising
1065 - at top level use tyVarsOfType
1066 - in nested bindings use exactTyVarsOfType
1067 See Trac #1813 for example.
1070 exactTyVarsOfType :: TcType -> TyVarSet
1071 -- Find the free type variables (of any kind)
1072 -- but *expand* type synonyms. See Note [Silly type synonym] above.
1073 exactTyVarsOfType ty
1076 go ty | Just ty' <- tcView ty = go ty' -- This is the key line
1077 go (TyVarTy tv) = unitVarSet tv
1078 go (TyConApp tycon tys) = exactTyVarsOfTypes tys
1079 go (PredTy ty) = go_pred ty
1080 go (FunTy arg res) = go arg `unionVarSet` go res
1081 go (AppTy fun arg) = go fun `unionVarSet` go arg
1082 go (ForAllTy tyvar ty) = delVarSet (go ty) tyvar
1083 `unionVarSet` go_tv tyvar
1085 go_pred (IParam _ ty) = go ty
1086 go_pred (ClassP _ tys) = exactTyVarsOfTypes tys
1087 go_pred (EqPred ty1 ty2) = go ty1 `unionVarSet` go ty2
1089 go_tv tyvar | isCoVar tyvar = go (tyVarKind tyvar)
1090 | otherwise = emptyVarSet
1092 exactTyVarsOfTypes :: [TcType] -> TyVarSet
1093 exactTyVarsOfTypes tys = foldr (unionVarSet . exactTyVarsOfType) emptyVarSet tys
1096 Find the free tycons and classes of a type. This is used in the front
1097 end of the compiler.
1100 tyClsNamesOfType :: Type -> NameSet
1101 tyClsNamesOfType (TyVarTy tv) = emptyNameSet
1102 tyClsNamesOfType (TyConApp tycon tys) = unitNameSet (getName tycon) `unionNameSets` tyClsNamesOfTypes tys
1103 tyClsNamesOfType (PredTy (IParam n ty)) = tyClsNamesOfType ty
1104 tyClsNamesOfType (PredTy (ClassP cl tys)) = unitNameSet (getName cl) `unionNameSets` tyClsNamesOfTypes tys
1105 tyClsNamesOfType (PredTy (EqPred ty1 ty2)) = tyClsNamesOfType ty1 `unionNameSets` tyClsNamesOfType ty2
1106 tyClsNamesOfType (FunTy arg res) = tyClsNamesOfType arg `unionNameSets` tyClsNamesOfType res
1107 tyClsNamesOfType (AppTy fun arg) = tyClsNamesOfType fun `unionNameSets` tyClsNamesOfType arg
1108 tyClsNamesOfType (ForAllTy tyvar ty) = tyClsNamesOfType ty
1110 tyClsNamesOfTypes tys = foldr (unionNameSets . tyClsNamesOfType) emptyNameSet tys
1112 tyClsNamesOfDFunHead :: Type -> NameSet
1113 -- Find the free type constructors and classes
1114 -- of the head of the dfun instance type
1115 -- The 'dfun_head_type' is because of
1116 -- instance Foo a => Baz T where ...
1117 -- The decl is an orphan if Baz and T are both not locally defined,
1118 -- even if Foo *is* locally defined
1119 tyClsNamesOfDFunHead dfun_ty
1120 = case tcSplitSigmaTy dfun_ty of
1121 (tvs,_,head_ty) -> tyClsNamesOfType head_ty
1125 %************************************************************************
1127 \subsection[TysWiredIn-ext-type]{External types}
1129 %************************************************************************
1131 The compiler's foreign function interface supports the passing of a
1132 restricted set of types as arguments and results (the restricting factor
1136 tcSplitIOType_maybe :: Type -> Maybe (TyCon, Type, CoercionI)
1137 -- (isIOType t) returns Just (IO,t',co)
1138 -- if co : t ~ IO t'
1139 -- returns Nothing otherwise
1140 tcSplitIOType_maybe ty
1141 = case tcSplitTyConApp_maybe ty of
1142 -- This split absolutely has to be a tcSplit, because we must
1143 -- see the IO type; and it's a newtype which is transparent to splitTyConApp.
1145 Just (io_tycon, [io_res_ty])
1146 | io_tycon `hasKey` ioTyConKey
1147 -> Just (io_tycon, io_res_ty, IdCo)
1150 | not (isRecursiveTyCon tc)
1151 , Just (ty, co1) <- instNewTyCon_maybe tc tys
1152 -- Newtypes that require a coercion are ok
1153 -> case tcSplitIOType_maybe ty of
1155 Just (tc, ty', co2) -> Just (tc, ty', co1 `mkTransCoI` co2)
1159 isFFITy :: Type -> Bool
1160 -- True for any TyCon that can possibly be an arg or result of an FFI call
1161 isFFITy ty = checkRepTyCon legalFFITyCon ty
1163 isFFIArgumentTy :: DynFlags -> Safety -> Type -> Bool
1164 -- Checks for valid argument type for a 'foreign import'
1165 isFFIArgumentTy dflags safety ty
1166 = checkRepTyCon (legalOutgoingTyCon dflags safety) ty
1168 isFFIExternalTy :: Type -> Bool
1169 -- Types that are allowed as arguments of a 'foreign export'
1170 isFFIExternalTy ty = checkRepTyCon legalFEArgTyCon ty
1172 isFFIImportResultTy :: DynFlags -> Type -> Bool
1173 isFFIImportResultTy dflags ty
1174 = checkRepTyCon (legalFIResultTyCon dflags) ty
1176 isFFIExportResultTy :: Type -> Bool
1177 isFFIExportResultTy ty = checkRepTyCon legalFEResultTyCon ty
1179 isFFIDynArgumentTy :: Type -> Bool
1180 -- The argument type of a foreign import dynamic must be Ptr, FunPtr, Addr,
1181 -- or a newtype of either.
1182 isFFIDynArgumentTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1184 isFFIDynResultTy :: Type -> Bool
1185 -- The result type of a foreign export dynamic must be Ptr, FunPtr, Addr,
1186 -- or a newtype of either.
1187 isFFIDynResultTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1189 isFFILabelTy :: Type -> Bool
1190 -- The type of a foreign label must be Ptr, FunPtr, Addr,
1191 -- or a newtype of either.
1192 isFFILabelTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1194 isFFIDotnetTy :: DynFlags -> Type -> Bool
1195 isFFIDotnetTy dflags ty
1196 = checkRepTyCon (\ tc -> (legalFIResultTyCon dflags tc ||
1197 isFFIDotnetObjTy ty || isStringTy ty)) ty
1198 -- NB: isStringTy used to look through newtypes, but
1199 -- it no longer does so. May need to adjust isFFIDotNetTy
1200 -- if we do want to look through newtypes.
1203 = checkRepTyCon check_tc t_ty
1205 (_, t_ty) = tcSplitForAllTys ty
1206 check_tc tc = getName tc == objectTyConName
1208 toDNType :: Type -> DNType
1210 | isStringTy ty = DNString
1211 | isFFIDotnetObjTy ty = DNObject
1212 | Just (tc,argTys) <- tcSplitTyConApp_maybe ty
1213 = case lookup (getUnique tc) dn_assoc of
1216 | tc `hasKey` ioTyConKey -> toDNType (head argTys)
1217 | otherwise -> pprPanic ("toDNType: unsupported .NET type")
1218 (pprType ty <+> parens (hcat (map pprType argTys)) <+> ppr tc)
1219 | otherwise = panic "toDNType" -- Is this right?
1221 dn_assoc :: [ (Unique, DNType) ]
1222 dn_assoc = [ (unitTyConKey, DNUnit)
1223 , (intTyConKey, DNInt)
1224 , (int8TyConKey, DNInt8)
1225 , (int16TyConKey, DNInt16)
1226 , (int32TyConKey, DNInt32)
1227 , (int64TyConKey, DNInt64)
1228 , (wordTyConKey, DNInt)
1229 , (word8TyConKey, DNWord8)
1230 , (word16TyConKey, DNWord16)
1231 , (word32TyConKey, DNWord32)
1232 , (word64TyConKey, DNWord64)
1233 , (floatTyConKey, DNFloat)
1234 , (doubleTyConKey, DNDouble)
1235 , (ptrTyConKey, DNPtr)
1236 , (funPtrTyConKey, DNPtr)
1237 , (charTyConKey, DNChar)
1238 , (boolTyConKey, DNBool)
1241 checkRepTyCon :: (TyCon -> Bool) -> Type -> Bool
1242 -- Look through newtypes
1243 -- Non-recursive ones are transparent to splitTyConApp,
1244 -- but recursive ones aren't. Manuel had:
1245 -- newtype T = MkT (Ptr T)
1246 -- and wanted it to work...
1247 checkRepTyCon check_tc ty
1248 | Just (tc,_) <- splitTyConApp_maybe (repType ty) = check_tc tc
1251 checkRepTyConKey :: [Unique] -> Type -> Bool
1252 -- Like checkRepTyCon, but just looks at the TyCon key
1253 checkRepTyConKey keys
1254 = checkRepTyCon (\tc -> tyConUnique tc `elem` keys)
1257 ----------------------------------------------
1258 These chaps do the work; they are not exported
1259 ----------------------------------------------
1262 legalFEArgTyCon :: TyCon -> Bool
1264 -- It's illegal to make foreign exports that take unboxed
1265 -- arguments. The RTS API currently can't invoke such things. --SDM 7/2000
1266 = boxedMarshalableTyCon tc
1268 legalFIResultTyCon :: DynFlags -> TyCon -> Bool
1269 legalFIResultTyCon dflags tc
1270 | tc == unitTyCon = True
1271 | otherwise = marshalableTyCon dflags tc
1273 legalFEResultTyCon :: TyCon -> Bool
1274 legalFEResultTyCon tc
1275 | tc == unitTyCon = True
1276 | otherwise = boxedMarshalableTyCon tc
1278 legalOutgoingTyCon :: DynFlags -> Safety -> TyCon -> Bool
1279 -- Checks validity of types going from Haskell -> external world
1280 legalOutgoingTyCon dflags safety tc
1281 = marshalableTyCon dflags tc
1283 legalFFITyCon :: TyCon -> Bool
1284 -- True for any TyCon that can possibly be an arg or result of an FFI call
1286 = isUnLiftedTyCon tc || boxedMarshalableTyCon tc || tc == unitTyCon
1288 marshalableTyCon dflags tc
1289 = (dopt Opt_UnliftedFFITypes dflags
1290 && isUnLiftedTyCon tc
1291 && not (isUnboxedTupleTyCon tc)
1292 && case tyConPrimRep tc of -- Note [Marshalling VoidRep]
1295 || boxedMarshalableTyCon tc
1297 boxedMarshalableTyCon tc
1298 = getUnique tc `elem` [ intTyConKey, int8TyConKey, int16TyConKey
1299 , int32TyConKey, int64TyConKey
1300 , wordTyConKey, word8TyConKey, word16TyConKey
1301 , word32TyConKey, word64TyConKey
1302 , floatTyConKey, doubleTyConKey
1303 , ptrTyConKey, funPtrTyConKey
1310 Note [Marshalling VoidRep]
1311 ~~~~~~~~~~~~~~~~~~~~~~~~~~
1312 We don't treat State# (whose PrimRep is VoidRep) as marshalable.
1313 In turn that means you can't write
1314 foreign import foo :: Int -> State# RealWorld
1316 Reason: the back end falls over with panic "primRepHint:VoidRep";
1317 and there is no compelling reason to permit it