2 % (c) The University of Glasgow 2006
3 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
5 \section[TcType]{Types used in the typechecker}
7 This module provides the Type interface for front-end parts of the
10 * treat "source types" as opaque:
11 newtypes, and predicates are meaningful.
12 * look through usage types
14 The "tc" prefix is for "TypeChecker", because the type checker
15 is the principal client.
19 --------------------------------
21 TcType, TcSigmaType, TcRhoType, TcTauType, TcPredType, TcThetaType,
22 TcTyVar, TcTyVarSet, TcKind,
24 BoxyTyVar, BoxySigmaType, BoxyRhoType, BoxyThetaType, BoxyType,
26 --------------------------------
28 UserTypeCtxt(..), pprUserTypeCtxt,
29 TcTyVarDetails(..), BoxInfo(..), pprTcTyVarDetails,
30 MetaDetails(Flexi, Indirect), SkolemInfo(..), pprSkolTvBinding, pprSkolInfo,
31 isImmutableTyVar, isSkolemTyVar, isMetaTyVar, isBoxyTyVar,
32 isSigTyVar, isExistentialTyVar, isTyConableTyVar,
34 isFlexi, isIndirect, isRuntimeUnk, isUnk,
36 --------------------------------
40 --------------------------------
42 -- These are important because they do not look through newtypes
44 tcSplitForAllTys, tcSplitPhiTy,
45 tcSplitFunTy_maybe, tcSplitFunTys, tcFunArgTy, tcFunResultTy, tcSplitFunTysN,
46 tcSplitTyConApp, tcSplitTyConApp_maybe, tcTyConAppTyCon, tcTyConAppArgs,
47 tcSplitAppTy_maybe, tcSplitAppTy, tcSplitAppTys, repSplitAppTy_maybe,
48 tcInstHeadTyNotSynonym, tcInstHeadTyAppAllTyVars,
49 tcGetTyVar_maybe, tcGetTyVar,
50 tcSplitSigmaTy, tcMultiSplitSigmaTy,
52 ---------------------------------
54 -- Again, newtypes are opaque
55 tcEqType, tcEqTypes, tcEqPred, tcCmpType, tcCmpTypes, tcCmpPred, tcEqTypeX,
57 isSigmaTy, isOverloadedTy, isRigidTy, isBoxyTy,
58 isDoubleTy, isFloatTy, isIntTy, isWordTy, isStringTy,
59 isIntegerTy, isBoolTy, isUnitTy, isCharTy,
60 isTauTy, isTauTyCon, tcIsTyVarTy, tcIsForAllTy,
63 ---------------------------------
64 -- Misc type manipulators
66 tyClsNamesOfType, tyClsNamesOfDFunHead,
69 ---------------------------------
71 getClassPredTys_maybe, getClassPredTys,
72 isClassPred, isTyVarClassPred, isEqPred,
73 mkDictTy, tcSplitPredTy_maybe,
74 isPredTy, isDictTy, tcSplitDFunTy, tcSplitDFunHead, predTyUnique,
75 mkClassPred, isInheritablePred, isIPPred,
76 dataConsStupidTheta, isRefineableTy, isRefineablePred,
78 ---------------------------------
79 -- Foreign import and export
80 isFFIArgumentTy, -- :: DynFlags -> Safety -> Type -> Bool
81 isFFIImportResultTy, -- :: DynFlags -> Type -> Bool
82 isFFIExportResultTy, -- :: Type -> Bool
83 isFFIExternalTy, -- :: Type -> Bool
84 isFFIDynArgumentTy, -- :: Type -> Bool
85 isFFIDynResultTy, -- :: Type -> Bool
86 isFFILabelTy, -- :: Type -> Bool
87 isFFIDotnetTy, -- :: DynFlags -> Type -> Bool
88 isFFIDotnetObjTy, -- :: Type -> Bool
89 isFFITy, -- :: Type -> Bool
90 tcSplitIOType_maybe, -- :: Type -> Maybe Type
91 toDNType, -- :: Type -> DNType
93 --------------------------------
94 -- Rexported from Type
95 Kind, -- Stuff to do with kinds is insensitive to pre/post Tc
96 unliftedTypeKind, liftedTypeKind, argTypeKind,
97 openTypeKind, mkArrowKind, mkArrowKinds,
98 isLiftedTypeKind, isUnliftedTypeKind, isSubOpenTypeKind,
99 isSubArgTypeKind, isSubKind, defaultKind,
100 kindVarRef, mkKindVar,
102 Type, PredType(..), ThetaType,
103 mkForAllTy, mkForAllTys,
104 mkFunTy, mkFunTys, zipFunTys,
105 mkTyConApp, mkAppTy, mkAppTys, applyTy, applyTys,
106 mkTyVarTy, mkTyVarTys, mkTyConTy, mkPredTy, mkPredTys,
108 -- Type substitutions
109 TvSubst(..), -- Representation visible to a few friends
110 TvSubstEnv, emptyTvSubst, substEqSpec,
111 mkOpenTvSubst, zipOpenTvSubst, zipTopTvSubst, mkTopTvSubst, notElemTvSubst,
112 getTvSubstEnv, setTvSubstEnv, getTvInScope, extendTvInScope, lookupTyVar,
113 extendTvSubst, extendTvSubstList, isInScope, mkTvSubst, zipTyEnv,
114 substTy, substTys, substTyWith, substTheta, substTyVar, substTyVars, substTyVarBndr,
116 isUnLiftedType, -- Source types are always lifted
117 isUnboxedTupleType, -- Ditto
120 tidyTopType, tidyType, tidyPred, tidyTypes, tidyFreeTyVars, tidyOpenType, tidyOpenTypes,
121 tidyTyVarBndr, tidyOpenTyVar, tidyOpenTyVars, tidySkolemTyVar,
124 tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tyVarsOfTheta,
125 tcTyVarsOfType, tcTyVarsOfTypes, exactTyVarsOfType, exactTyVarsOfTypes,
127 pprKind, pprParendKind,
128 pprType, pprParendType, pprTypeApp, pprTyThingCategory,
129 pprPred, pprTheta, pprThetaArrow, pprClassPred
133 #include "HsVersions.h"
167 %************************************************************************
171 %************************************************************************
173 The type checker divides the generic Type world into the
174 following more structured beasts:
176 sigma ::= forall tyvars. phi
177 -- A sigma type is a qualified type
179 -- Note that even if 'tyvars' is empty, theta
180 -- may not be: e.g. (?x::Int) => Int
182 -- Note that 'sigma' is in prenex form:
183 -- all the foralls are at the front.
184 -- A 'phi' type has no foralls to the right of
192 -- A 'tau' type has no quantification anywhere
193 -- Note that the args of a type constructor must be taus
195 | tycon tau_1 .. tau_n
199 -- In all cases, a (saturated) type synonym application is legal,
200 -- provided it expands to the required form.
203 type TcTyVar = TyVar -- Used only during type inference
204 type TcType = Type -- A TcType can have mutable type variables
205 -- Invariant on ForAllTy in TcTypes:
207 -- a cannot occur inside a MutTyVar in T; that is,
208 -- T is "flattened" before quantifying over a
210 -- These types do not have boxy type variables in them
211 type TcPredType = PredType
212 type TcThetaType = ThetaType
213 type TcSigmaType = TcType
214 type TcRhoType = TcType
215 type TcTauType = TcType
217 type TcTyVarSet = TyVarSet
219 -- These types may have boxy type variables in them
220 type BoxyTyVar = TcTyVar
221 type BoxyRhoType = TcType
222 type BoxyThetaType = TcThetaType
223 type BoxySigmaType = TcType
224 type BoxyType = TcType
228 %************************************************************************
230 \subsection{TyVarDetails}
232 %************************************************************************
234 TyVarDetails gives extra info about type variables, used during type
235 checking. It's attached to mutable type variables only.
236 It's knot-tied back to Var.lhs. There is no reason in principle
237 why Var.lhs shouldn't actually have the definition, but it "belongs" here.
240 Note [Signature skolems]
241 ~~~~~~~~~~~~~~~~~~~~~~~~
246 (x,y,z) = ([y,z], z, head x)
248 Here, x and y have type sigs, which go into the environment. We used to
249 instantiate their types with skolem constants, and push those types into
250 the RHS, so we'd typecheck the RHS with type
252 where a*, b* are skolem constants, and c is an ordinary meta type varible.
254 The trouble is that the occurrences of z in the RHS force a* and b* to
255 be the *same*, so we can't make them into skolem constants that don't unify
256 with each other. Alas.
258 One solution would be insist that in the above defn the programmer uses
259 the same type variable in both type signatures. But that takes explanation.
261 The alternative (currently implemented) is to have a special kind of skolem
262 constant, SigTv, which can unify with other SigTvs. These are *not* treated
263 as righd for the purposes of GADTs. And they are used *only* for pattern
264 bindings and mutually recursive function bindings. See the function
265 TcBinds.tcInstSig, and its use_skols parameter.
269 -- A TyVarDetails is inside a TyVar
271 = SkolemTv SkolemInfo -- A skolem constant
273 | MetaTv BoxInfo (IORef MetaDetails)
276 = BoxTv -- The contents is a (non-boxy) sigma-type
277 -- That is, this MetaTv is a "box"
279 | TauTv -- The contents is a (non-boxy) tau-type
280 -- That is, this MetaTv is an ordinary unification variable
282 | SigTv SkolemInfo -- A variant of TauTv, except that it should not be
283 -- unified with a type, only with a type variable
284 -- SigTvs are only distinguished to improve error messages
285 -- see Note [Signature skolems]
286 -- The MetaDetails, if filled in, will
287 -- always be another SigTv or a SkolemTv
290 -- A TauTv is always filled in with a tau-type, which
291 -- never contains any BoxTvs, nor any ForAlls
293 -- However, a BoxTv can contain a type that contains further BoxTvs
294 -- Notably, when typechecking an explicit list, say [e1,e2], with
295 -- expected type being a box b1, we fill in b1 with (List b2), where
296 -- b2 is another (currently empty) box.
299 = Flexi -- Flexi type variables unify to become
302 | Indirect TcType -- INVARIANT:
303 -- For a BoxTv, this type must be non-boxy
304 -- For a TauTv, this type must be a tau-type
306 -- Generally speaking, SkolemInfo should not contain location info
307 -- that is contained in the Name of the tyvar with this SkolemInfo
309 = SigSkol UserTypeCtxt -- A skolem that is created by instantiating
310 -- a programmer-supplied type signature
311 -- Location of the binding site is on the TyVar
313 -- The rest are for non-scoped skolems
314 | ClsSkol Class -- Bound at a class decl
315 | InstSkol -- Bound at an instance decl
316 | FamInstSkol -- Bound at a family instance decl
317 | PatSkol DataCon -- An existential type variable bound by a pattern for
318 -- a data constructor with an existential type. E.g.
319 -- data T = forall a. Eq a => MkT a
321 -- The pattern MkT x will allocate an existential type
323 | ArrowSkol -- An arrow form (see TcArrows)
325 | RuleSkol RuleName -- The LHS of a RULE
326 | GenSkol [TcTyVar] -- Bound when doing a subsumption check for
327 TcType -- (forall tvs. ty)
329 | RuntimeUnkSkol -- a type variable used to represent an unknown
330 -- runtime type (used in the GHCi debugger)
332 | UnkSkol -- Unhelpful info (until I improve it)
334 -------------------------------------
335 -- UserTypeCtxt describes the places where a
336 -- programmer-written type signature can occur
337 -- Like SkolemInfo, no location info
339 = FunSigCtxt Name -- Function type signature
340 -- Also used for types in SPECIALISE pragmas
341 | ExprSigCtxt -- Expression type signature
342 | ConArgCtxt Name -- Data constructor argument
343 | TySynCtxt Name -- RHS of a type synonym decl
344 | GenPatCtxt -- Pattern in generic decl
345 -- f{| a+b |} (Inl x) = ...
346 | LamPatSigCtxt -- Type sig in lambda pattern
348 | BindPatSigCtxt -- Type sig in pattern binding pattern
350 | ResSigCtxt -- Result type sig
352 | ForSigCtxt Name -- Foreign inport or export signature
353 | DefaultDeclCtxt -- Types in a default declaration
354 | SpecInstCtxt -- SPECIALISE instance pragma
356 -- Notes re TySynCtxt
357 -- We allow type synonyms that aren't types; e.g. type List = []
359 -- If the RHS mentions tyvars that aren't in scope, we'll
360 -- quantify over them:
361 -- e.g. type T = a->a
362 -- will become type T = forall a. a->a
364 -- With gla-exts that's right, but for H98 we should complain.
366 ---------------------------------
369 mkKindName :: Unique -> Name
370 mkKindName unique = mkSystemName unique kind_var_occ
372 kindVarRef :: KindVar -> IORef MetaDetails
374 ASSERT ( isTcTyVar tc )
375 case tcTyVarDetails tc of
376 MetaTv TauTv ref -> ref
377 _ -> pprPanic "kindVarRef" (ppr tc)
379 mkKindVar :: Unique -> IORef MetaDetails -> KindVar
381 = mkTcTyVar (mkKindName u)
382 tySuperKind -- not sure this is right,
383 -- do we need kind vars for
387 kind_var_occ :: OccName -- Just one for all KindVars
388 -- They may be jiggled by tidying
389 kind_var_occ = mkOccName tvName "k"
392 %************************************************************************
396 %************************************************************************
399 pprTcTyVarDetails :: TcTyVarDetails -> SDoc
401 pprTcTyVarDetails (SkolemTv _) = ptext (sLit "sk")
402 pprTcTyVarDetails (MetaTv BoxTv _) = ptext (sLit "box")
403 pprTcTyVarDetails (MetaTv TauTv _) = ptext (sLit "tau")
404 pprTcTyVarDetails (MetaTv (SigTv _) _) = ptext (sLit "sig")
406 pprUserTypeCtxt :: UserTypeCtxt -> SDoc
407 pprUserTypeCtxt (FunSigCtxt n) = ptext (sLit "the type signature for") <+> quotes (ppr n)
408 pprUserTypeCtxt ExprSigCtxt = ptext (sLit "an expression type signature")
409 pprUserTypeCtxt (ConArgCtxt c) = ptext (sLit "the type of the constructor") <+> quotes (ppr c)
410 pprUserTypeCtxt (TySynCtxt c) = ptext (sLit "the RHS of the type synonym") <+> quotes (ppr c)
411 pprUserTypeCtxt GenPatCtxt = ptext (sLit "the type pattern of a generic definition")
412 pprUserTypeCtxt LamPatSigCtxt = ptext (sLit "a pattern type signature")
413 pprUserTypeCtxt BindPatSigCtxt = ptext (sLit "a pattern type signature")
414 pprUserTypeCtxt ResSigCtxt = ptext (sLit "a result type signature")
415 pprUserTypeCtxt (ForSigCtxt n) = ptext (sLit "the foreign declaration for") <+> quotes (ppr n)
416 pprUserTypeCtxt DefaultDeclCtxt = ptext (sLit "a type in a `default' declaration")
417 pprUserTypeCtxt SpecInstCtxt = ptext (sLit "a SPECIALISE instance pragma")
420 --------------------------------
421 tidySkolemTyVar :: TidyEnv -> TcTyVar -> (TidyEnv, TcTyVar)
422 -- Tidy the type inside a GenSkol, preparatory to printing it
423 tidySkolemTyVar env tv
424 = ASSERT( isSkolemTyVar tv || isSigTyVar tv )
425 (env1, mkTcTyVar (tyVarName tv) (tyVarKind tv) info1)
427 (env1, info1) = case tcTyVarDetails tv of
428 SkolemTv info -> (env1, SkolemTv info')
430 (env1, info') = tidy_skol_info env info
431 MetaTv (SigTv info) box -> (env1, MetaTv (SigTv info') box)
433 (env1, info') = tidy_skol_info env info
436 tidy_skol_info env (GenSkol tvs ty) = (env2, GenSkol tvs1 ty1)
438 (env1, tvs1) = tidyOpenTyVars env tvs
439 (env2, ty1) = tidyOpenType env1 ty
440 tidy_skol_info env info = (env, info)
442 pprSkolTvBinding :: TcTyVar -> SDoc
443 -- Print info about the binding of a skolem tyvar,
444 -- or nothing if we don't have anything useful to say
446 = ASSERT ( isTcTyVar tv )
447 quotes (ppr tv) <+> ppr_details (tcTyVarDetails tv)
449 ppr_details (MetaTv TauTv _) = ptext (sLit "is a meta type variable")
450 ppr_details (MetaTv BoxTv _) = ptext (sLit "is a boxy type variable")
451 ppr_details (MetaTv (SigTv info) _) = ppr_skol info
452 ppr_details (SkolemTv info) = ppr_skol info
454 ppr_skol UnkSkol = ptext (sLit "is an unknown type variable") -- Unhelpful
455 ppr_skol RuntimeUnkSkol = ptext (sLit "is an unknown runtime type")
456 ppr_skol info = sep [ptext (sLit "is a rigid type variable bound by"),
457 sep [pprSkolInfo info,
458 nest 2 (ptext (sLit "at") <+> ppr (getSrcLoc tv))]]
460 pprSkolInfo :: SkolemInfo -> SDoc
461 pprSkolInfo (SigSkol ctxt) = pprUserTypeCtxt ctxt
462 pprSkolInfo (ClsSkol cls) = ptext (sLit "the class declaration for") <+> quotes (ppr cls)
463 pprSkolInfo InstSkol = ptext (sLit "the instance declaration")
464 pprSkolInfo FamInstSkol = ptext (sLit "the family instance declaration")
465 pprSkolInfo (RuleSkol name) = ptext (sLit "the RULE") <+> doubleQuotes (ftext name)
466 pprSkolInfo ArrowSkol = ptext (sLit "the arrow form")
467 pprSkolInfo (PatSkol dc) = sep [ptext (sLit "the constructor") <+> quotes (ppr dc)]
468 pprSkolInfo (GenSkol tvs ty) = sep [ptext (sLit "the polymorphic type"),
469 nest 2 (quotes (ppr (mkForAllTys tvs ty)))]
472 -- For type variables the others are dealt with by pprSkolTvBinding.
473 -- For Insts, these cases should not happen
474 pprSkolInfo UnkSkol = panic "UnkSkol"
475 pprSkolInfo RuntimeUnkSkol = panic "RuntimeUnkSkol"
477 instance Outputable MetaDetails where
478 ppr Flexi = ptext (sLit "Flexi")
479 ppr (Indirect ty) = ptext (sLit "Indirect") <+> ppr ty
483 %************************************************************************
487 %************************************************************************
490 isImmutableTyVar :: TyVar -> Bool
493 | isTcTyVar tv = isSkolemTyVar tv
496 isTyConableTyVar, isSkolemTyVar, isExistentialTyVar,
497 isBoxyTyVar, isMetaTyVar :: TcTyVar -> Bool
500 -- True of a meta-type variable that can be filled in
501 -- with a type constructor application; in particular,
503 = ASSERT( isTcTyVar tv)
504 case tcTyVarDetails tv of
505 MetaTv BoxTv _ -> True
506 MetaTv TauTv _ -> True
507 MetaTv (SigTv {}) _ -> False
511 = ASSERT( isTcTyVar tv )
512 case tcTyVarDetails tv of
516 isExistentialTyVar tv -- Existential type variable, bound by a pattern
517 = ASSERT( isTcTyVar tv )
518 case tcTyVarDetails tv of
519 SkolemTv (PatSkol {}) -> True
523 = ASSERT2( isTcTyVar tv, ppr tv )
524 case tcTyVarDetails tv of
529 = ASSERT( isTcTyVar tv )
530 case tcTyVarDetails tv of
531 MetaTv BoxTv _ -> True
534 isSigTyVar :: Var -> Bool
536 = ASSERT( isTcTyVar tv )
537 case tcTyVarDetails tv of
538 MetaTv (SigTv _) _ -> True
541 metaTvRef :: TyVar -> IORef MetaDetails
543 = ASSERT2( isTcTyVar tv, ppr tv )
544 case tcTyVarDetails tv of
546 _ -> pprPanic "metaTvRef" (ppr tv)
548 isFlexi, isIndirect :: MetaDetails -> Bool
552 isIndirect (Indirect _) = True
555 isRuntimeUnk :: TyVar -> Bool
556 isRuntimeUnk x | isTcTyVar x
557 , SkolemTv RuntimeUnkSkol <- tcTyVarDetails x = True
560 isUnk :: TyVar -> Bool
561 isUnk x | isTcTyVar x
562 , SkolemTv UnkSkol <- tcTyVarDetails x = True
567 %************************************************************************
569 \subsection{Tau, sigma and rho}
571 %************************************************************************
574 mkSigmaTy :: [TyVar] -> [PredType] -> Type -> Type
575 mkSigmaTy tyvars theta tau = mkForAllTys tyvars (mkPhiTy theta tau)
577 mkPhiTy :: [PredType] -> Type -> Type
578 mkPhiTy theta ty = foldr (\p r -> mkFunTy (mkPredTy p) r) ty theta
581 @isTauTy@ tests for nested for-alls. It should not be called on a boxy type.
584 isTauTy :: Type -> Bool
585 isTauTy ty | Just ty' <- tcView ty = isTauTy ty'
586 isTauTy (TyVarTy tv) = ASSERT( not (isTcTyVar tv && isBoxyTyVar tv) )
588 isTauTy (TyConApp tc tys) = all isTauTy tys && isTauTyCon tc
589 isTauTy (AppTy a b) = isTauTy a && isTauTy b
590 isTauTy (FunTy a b) = isTauTy a && isTauTy b
591 isTauTy (PredTy _) = True -- Don't look through source types
595 isTauTyCon :: TyCon -> Bool
596 -- Returns False for type synonyms whose expansion is a polytype
598 | isClosedSynTyCon tc = isTauTy (snd (synTyConDefn tc))
602 isBoxyTy :: TcType -> Bool
603 isBoxyTy ty = any isBoxyTyVar (varSetElems (tcTyVarsOfType ty))
605 isRigidTy :: TcType -> Bool
606 -- A type is rigid if it has no meta type variables in it
607 isRigidTy ty = all isImmutableTyVar (varSetElems (tcTyVarsOfType ty))
609 isRefineableTy :: TcType -> (Bool,Bool)
610 -- A type should have type refinements applied to it if it has
611 -- free type variables, and they are all rigid
612 isRefineableTy ty = (null tc_tvs, all isImmutableTyVar tc_tvs)
614 tc_tvs = varSetElems (tcTyVarsOfType ty)
616 isRefineablePred :: TcPredType -> Bool
617 isRefineablePred pred = not (null tc_tvs) && all isImmutableTyVar tc_tvs
619 tc_tvs = varSetElems (tcTyVarsOfPred pred)
622 getDFunTyKey :: Type -> OccName -- Get some string from a type, to be used to
623 -- construct a dictionary function name
624 getDFunTyKey ty | Just ty' <- tcView ty = getDFunTyKey ty'
625 getDFunTyKey (TyVarTy tv) = getOccName tv
626 getDFunTyKey (TyConApp tc _) = getOccName tc
627 getDFunTyKey (AppTy fun _) = getDFunTyKey fun
628 getDFunTyKey (FunTy _ _) = getOccName funTyCon
629 getDFunTyKey (ForAllTy _ t) = getDFunTyKey t
630 getDFunTyKey ty = pprPanic "getDFunTyKey" (pprType ty)
631 -- PredTy shouldn't happen
635 %************************************************************************
637 \subsection{Expanding and splitting}
639 %************************************************************************
641 These tcSplit functions are like their non-Tc analogues, but
642 a) they do not look through newtypes
643 b) they do not look through PredTys
644 c) [future] they ignore usage-type annotations
646 However, they are non-monadic and do not follow through mutable type
647 variables. It's up to you to make sure this doesn't matter.
650 tcSplitForAllTys :: Type -> ([TyVar], Type)
651 tcSplitForAllTys ty = split ty ty []
653 split orig_ty ty tvs | Just ty' <- tcView ty = split orig_ty ty' tvs
654 split _ (ForAllTy tv ty) tvs
655 | not (isCoVar tv) = split ty ty (tv:tvs)
656 split orig_ty _ tvs = (reverse tvs, orig_ty)
658 tcIsForAllTy :: Type -> Bool
659 tcIsForAllTy ty | Just ty' <- tcView ty = tcIsForAllTy ty'
660 tcIsForAllTy (ForAllTy tv _) = not (isCoVar tv)
661 tcIsForAllTy _ = False
663 tcSplitPhiTy :: Type -> (ThetaType, Type)
664 tcSplitPhiTy ty = split ty ty []
666 split orig_ty ty tvs | Just ty' <- tcView ty = split orig_ty ty' tvs
668 split _ (ForAllTy tv ty) ts
669 | isCoVar tv = split ty ty (coVarPred tv : ts)
670 split _ (FunTy arg res) ts
671 | Just p <- tcSplitPredTy_maybe arg = split res res (p:ts)
672 split orig_ty _ ts = (reverse ts, orig_ty)
674 tcSplitSigmaTy :: Type -> ([TyVar], ThetaType, Type)
675 tcSplitSigmaTy ty = case tcSplitForAllTys ty of
676 (tvs, rho) -> case tcSplitPhiTy rho of
677 (theta, tau) -> (tvs, theta, tau)
679 -----------------------
682 -> ( [([TyVar], ThetaType)], -- forall as.C => forall bs.D
683 TcSigmaType) -- The rest of the type
685 -- We need a loop here because we are now prepared to entertain
687 -- f:: forall a. Eq a => forall b. Baz b => tau
688 -- We want to instantiate this to
689 -- f2::tau {f2 = f1 b (Baz b), f1 = f a (Eq a)}
691 tcMultiSplitSigmaTy sigma
692 = case (tcSplitSigmaTy sigma) of
693 ([], [], _) -> ([], sigma)
694 (tvs, theta, ty) -> case tcMultiSplitSigmaTy ty of
695 (pairs, rest) -> ((tvs,theta):pairs, rest)
697 -----------------------
698 tcTyConAppTyCon :: Type -> TyCon
699 tcTyConAppTyCon ty = case tcSplitTyConApp_maybe ty of
701 Nothing -> pprPanic "tcTyConAppTyCon" (pprType ty)
703 tcTyConAppArgs :: Type -> [Type]
704 tcTyConAppArgs ty = case tcSplitTyConApp_maybe ty of
705 Just (_, args) -> args
706 Nothing -> pprPanic "tcTyConAppArgs" (pprType ty)
708 tcSplitTyConApp :: Type -> (TyCon, [Type])
709 tcSplitTyConApp ty = case tcSplitTyConApp_maybe ty of
711 Nothing -> pprPanic "tcSplitTyConApp" (pprType ty)
713 tcSplitTyConApp_maybe :: Type -> Maybe (TyCon, [Type])
714 tcSplitTyConApp_maybe ty | Just ty' <- tcView ty = tcSplitTyConApp_maybe ty'
715 tcSplitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
716 tcSplitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res])
717 -- Newtypes are opaque, so they may be split
718 -- However, predicates are not treated
719 -- as tycon applications by the type checker
720 tcSplitTyConApp_maybe _ = Nothing
722 -----------------------
723 tcSplitFunTys :: Type -> ([Type], Type)
724 tcSplitFunTys ty = case tcSplitFunTy_maybe ty of
726 Just (arg,res) -> (arg:args, res')
728 (args,res') = tcSplitFunTys res
730 tcSplitFunTy_maybe :: Type -> Maybe (Type, Type)
731 tcSplitFunTy_maybe ty | Just ty' <- tcView ty = tcSplitFunTy_maybe ty'
732 tcSplitFunTy_maybe (FunTy arg res) | not (isPredTy arg) = Just (arg, res)
733 tcSplitFunTy_maybe _ = Nothing
734 -- Note the (not (isPredTy arg)) guard
735 -- Consider (?x::Int) => Bool
736 -- We don't want to treat this as a function type!
737 -- A concrete example is test tc230:
738 -- f :: () -> (?p :: ()) => () -> ()
744 -> Arity -- N: Number of desired args
745 -> ([TcSigmaType], -- Arg types (N or fewer)
746 TcSigmaType) -- The rest of the type
748 tcSplitFunTysN ty n_args
751 | Just (arg,res) <- tcSplitFunTy_maybe ty
752 = case tcSplitFunTysN res (n_args - 1) of
753 (args, res) -> (arg:args, res)
757 tcSplitFunTy :: Type -> (Type, Type)
758 tcSplitFunTy ty = expectJust "tcSplitFunTy" (tcSplitFunTy_maybe ty)
760 tcFunArgTy :: Type -> Type
761 tcFunArgTy ty = fst (tcSplitFunTy ty)
763 tcFunResultTy :: Type -> Type
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 _ = 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 _ -> 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 _ -> 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
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 _ = Nothing
853 predTyUnique :: PredType -> Unique
854 predTyUnique (IParam n _) = getUnique (ipNameName n)
855 predTyUnique (ClassP clas _) = getUnique clas
856 predTyUnique (EqPred a b) = pprPanic "predTyUnique" (ppr (EqPred a b))
860 --------------------- Dictionary types ---------------------------------
863 mkClassPred :: Class -> [Type] -> PredType
864 mkClassPred clas tys = ClassP clas tys
866 isClassPred :: PredType -> Bool
867 isClassPred (ClassP _ _) = True
868 isClassPred _ = False
870 isTyVarClassPred :: PredType -> Bool
871 isTyVarClassPred (ClassP _ tys) = all tcIsTyVarTy tys
872 isTyVarClassPred _ = False
874 getClassPredTys_maybe :: PredType -> Maybe (Class, [Type])
875 getClassPredTys_maybe (ClassP clas tys) = Just (clas, tys)
876 getClassPredTys_maybe _ = Nothing
878 getClassPredTys :: PredType -> (Class, [Type])
879 getClassPredTys (ClassP clas tys) = (clas, tys)
880 getClassPredTys _ = panic "getClassPredTys"
882 mkDictTy :: Class -> [Type] -> Type
883 mkDictTy clas tys = mkPredTy (ClassP clas tys)
885 isDictTy :: Type -> Bool
886 isDictTy ty | Just ty' <- tcView ty = isDictTy ty'
887 isDictTy (PredTy p) = isClassPred p
891 --------------------- Implicit parameters ---------------------------------
894 isIPPred :: PredType -> Bool
895 isIPPred (IParam _ _) = True
898 isInheritablePred :: PredType -> Bool
899 -- Can be inherited by a context. For example, consider
900 -- f x = let g y = (?v, y+x)
901 -- in (g 3 with ?v = 8,
903 -- The point is that g's type must be quantifed over ?v:
904 -- g :: (?v :: a) => a -> a
905 -- but it doesn't need to be quantified over the Num a dictionary
906 -- which can be free in g's rhs, and shared by both calls to g
907 isInheritablePred (ClassP _ _) = True
908 isInheritablePred (EqPred _ _) = True
909 isInheritablePred _ = False
912 --------------------- Equality predicates ---------------------------------
914 substEqSpec :: TvSubst -> [(TyVar,Type)] -> [(TcType,TcType)]
915 substEqSpec subst eq_spec = [ (substTyVar subst tv, substTy subst ty)
916 | (tv,ty) <- eq_spec]
919 --------------------- The stupid theta (sigh) ---------------------------------
922 dataConsStupidTheta :: [DataCon] -> ThetaType
923 -- Union the stupid thetas from all the specified constructors (non-empty)
924 -- All the constructors should have the same result type, modulo alpha conversion
925 -- The resulting ThetaType uses type variables from the *first* constructor in the list
927 -- It's here because it's used in MkId.mkRecordSelId, and in TcExpr
928 dataConsStupidTheta (con1:cons)
929 = nubBy tcEqPred all_preds
931 all_preds = dataConStupidTheta con1 ++ other_stupids
932 res_ty1 = dataConOrigResTy con1
933 other_stupids = [ substPred subst pred
935 , let (tvs, _, _, res_ty) = dataConSig con
936 Just subst = tcMatchTy (mkVarSet tvs) res_ty res_ty1
937 , pred <- dataConStupidTheta con ]
938 dataConsStupidTheta [] = panic "dataConsStupidTheta"
942 %************************************************************************
944 \subsection{Predicates}
946 %************************************************************************
948 isSigmaTy returns true of any qualified type. It doesn't *necessarily* have
950 f :: (?x::Int) => Int -> Int
953 isSigmaTy :: Type -> Bool
954 isSigmaTy ty | Just ty' <- tcView ty = isSigmaTy ty'
955 isSigmaTy (ForAllTy _ _) = True
956 isSigmaTy (FunTy a _) = isPredTy a
959 isOverloadedTy :: Type -> Bool
960 isOverloadedTy ty | Just ty' <- tcView ty = isOverloadedTy ty'
961 isOverloadedTy (ForAllTy _ ty) = isOverloadedTy ty
962 isOverloadedTy (FunTy a _) = isPredTy a
963 isOverloadedTy _ = False
965 isPredTy :: Type -> Bool -- Belongs in TcType because it does
966 -- not look through newtypes, or predtypes (of course)
967 isPredTy ty | Just ty' <- tcView ty = isPredTy ty'
968 isPredTy (PredTy _) = True
973 isFloatTy, isDoubleTy, isIntegerTy, isIntTy, isWordTy, isBoolTy,
974 isUnitTy, isCharTy :: Type -> Bool
975 isFloatTy = is_tc floatTyConKey
976 isDoubleTy = is_tc doubleTyConKey
977 isIntegerTy = is_tc integerTyConKey
978 isIntTy = is_tc intTyConKey
979 isWordTy = is_tc wordTyConKey
980 isBoolTy = is_tc boolTyConKey
981 isUnitTy = is_tc unitTyConKey
982 isCharTy = is_tc charTyConKey
984 isStringTy :: Type -> Bool
986 = case tcSplitTyConApp_maybe ty of
987 Just (tc, [arg_ty]) -> tc == listTyCon && isCharTy arg_ty
990 is_tc :: Unique -> Type -> Bool
991 -- Newtypes are opaque to this
992 is_tc uniq ty = case tcSplitTyConApp_maybe ty of
993 Just (tc, _) -> uniq == getUnique tc
998 -- NB: Currently used in places where we have already expanded type synonyms;
999 -- hence no 'coreView'. This could, however, be changed without breaking
1001 isOpenSynTyConApp :: TcTauType -> Bool
1002 isOpenSynTyConApp (TyConApp tc _) = isOpenSynTyCon tc
1003 isOpenSynTyConApp _other = False
1007 %************************************************************************
1011 %************************************************************************
1014 deNoteType :: Type -> Type
1015 -- Remove all *outermost* type synonyms and other notes
1016 deNoteType ty | Just ty' <- tcView ty = deNoteType ty'
1021 tcTyVarsOfType :: Type -> TcTyVarSet
1022 -- Just the *TcTyVars* free in the type
1023 -- (Types.tyVarsOfTypes finds all free TyVars)
1024 tcTyVarsOfType (TyVarTy tv) = if isTcTyVar tv then unitVarSet tv
1026 tcTyVarsOfType (TyConApp _ tys) = tcTyVarsOfTypes tys
1027 tcTyVarsOfType (PredTy sty) = tcTyVarsOfPred sty
1028 tcTyVarsOfType (FunTy arg res) = tcTyVarsOfType arg `unionVarSet` tcTyVarsOfType res
1029 tcTyVarsOfType (AppTy fun arg) = tcTyVarsOfType fun `unionVarSet` tcTyVarsOfType arg
1030 tcTyVarsOfType (ForAllTy tyvar ty) = (tcTyVarsOfType ty `delVarSet` tyvar)
1031 `unionVarSet` tcTyVarsOfTyVar tyvar
1032 -- We do sometimes quantify over skolem TcTyVars
1034 tcTyVarsOfTyVar :: TcTyVar -> TyVarSet
1035 tcTyVarsOfTyVar tv | isCoVar tv = tcTyVarsOfType (tyVarKind tv)
1036 | otherwise = emptyVarSet
1038 tcTyVarsOfTypes :: [Type] -> TyVarSet
1039 tcTyVarsOfTypes tys = foldr (unionVarSet.tcTyVarsOfType) emptyVarSet tys
1041 tcTyVarsOfPred :: PredType -> TyVarSet
1042 tcTyVarsOfPred (IParam _ ty) = tcTyVarsOfType ty
1043 tcTyVarsOfPred (ClassP _ tys) = tcTyVarsOfTypes tys
1044 tcTyVarsOfPred (EqPred ty1 ty2) = tcTyVarsOfType ty1 `unionVarSet` tcTyVarsOfType ty2
1047 Note [Silly type synonym]
1048 ~~~~~~~~~~~~~~~~~~~~~~~~~
1051 What are the free tyvars of (T x)? Empty, of course!
1052 Here's the example that Ralf Laemmel showed me:
1053 foo :: (forall a. C u a -> C u a) -> u
1054 mappend :: Monoid u => u -> u -> u
1056 bar :: Monoid u => u
1057 bar = foo (\t -> t `mappend` t)
1058 We have to generalise at the arg to f, and we don't
1059 want to capture the constraint (Monad (C u a)) because
1060 it appears to mention a. Pretty silly, but it was useful to him.
1062 exactTyVarsOfType is used by the type checker to figure out exactly
1063 which type variables are mentioned in a type. It's also used in the
1064 smart-app checking code --- see TcExpr.tcIdApp
1066 On the other hand, consider a *top-level* definition
1067 f = (\x -> x) :: T a -> T a
1068 If we don't abstract over 'a' it'll get fixed to GHC.Prim.Any, and then
1069 if we have an application like (f "x") we get a confusing error message
1070 involving Any. So the conclusion is this: when generalising
1071 - at top level use tyVarsOfType
1072 - in nested bindings use exactTyVarsOfType
1073 See Trac #1813 for example.
1076 exactTyVarsOfType :: TcType -> TyVarSet
1077 -- Find the free type variables (of any kind)
1078 -- but *expand* type synonyms. See Note [Silly type synonym] above.
1079 exactTyVarsOfType ty
1082 go ty | Just ty' <- tcView ty = go ty' -- This is the key line
1083 go (TyVarTy tv) = unitVarSet tv
1084 go (TyConApp _ tys) = exactTyVarsOfTypes tys
1085 go (PredTy ty) = go_pred ty
1086 go (FunTy arg res) = go arg `unionVarSet` go res
1087 go (AppTy fun arg) = go fun `unionVarSet` go arg
1088 go (ForAllTy tyvar ty) = delVarSet (go ty) tyvar
1089 `unionVarSet` go_tv tyvar
1091 go_pred (IParam _ ty) = go ty
1092 go_pred (ClassP _ tys) = exactTyVarsOfTypes tys
1093 go_pred (EqPred ty1 ty2) = go ty1 `unionVarSet` go ty2
1095 go_tv tyvar | isCoVar tyvar = go (tyVarKind tyvar)
1096 | otherwise = emptyVarSet
1098 exactTyVarsOfTypes :: [TcType] -> TyVarSet
1099 exactTyVarsOfTypes tys = foldr (unionVarSet . exactTyVarsOfType) emptyVarSet tys
1102 Find the free tycons and classes of a type. This is used in the front
1103 end of the compiler.
1106 tyClsNamesOfType :: Type -> NameSet
1107 tyClsNamesOfType (TyVarTy _) = emptyNameSet
1108 tyClsNamesOfType (TyConApp tycon tys) = unitNameSet (getName tycon) `unionNameSets` tyClsNamesOfTypes tys
1109 tyClsNamesOfType (PredTy (IParam _ ty)) = tyClsNamesOfType ty
1110 tyClsNamesOfType (PredTy (ClassP cl tys)) = unitNameSet (getName cl) `unionNameSets` tyClsNamesOfTypes tys
1111 tyClsNamesOfType (PredTy (EqPred ty1 ty2)) = tyClsNamesOfType ty1 `unionNameSets` tyClsNamesOfType ty2
1112 tyClsNamesOfType (FunTy arg res) = tyClsNamesOfType arg `unionNameSets` tyClsNamesOfType res
1113 tyClsNamesOfType (AppTy fun arg) = tyClsNamesOfType fun `unionNameSets` tyClsNamesOfType arg
1114 tyClsNamesOfType (ForAllTy _ ty) = tyClsNamesOfType ty
1116 tyClsNamesOfTypes :: [Type] -> NameSet
1117 tyClsNamesOfTypes tys = foldr (unionNameSets . tyClsNamesOfType) emptyNameSet tys
1119 tyClsNamesOfDFunHead :: Type -> NameSet
1120 -- Find the free type constructors and classes
1121 -- of the head of the dfun instance type
1122 -- The 'dfun_head_type' is because of
1123 -- instance Foo a => Baz T where ...
1124 -- The decl is an orphan if Baz and T are both not locally defined,
1125 -- even if Foo *is* locally defined
1126 tyClsNamesOfDFunHead dfun_ty
1127 = case tcSplitSigmaTy dfun_ty of
1128 (_, _, head_ty) -> tyClsNamesOfType head_ty
1132 %************************************************************************
1134 \subsection[TysWiredIn-ext-type]{External types}
1136 %************************************************************************
1138 The compiler's foreign function interface supports the passing of a
1139 restricted set of types as arguments and results (the restricting factor
1143 tcSplitIOType_maybe :: Type -> Maybe (TyCon, Type, CoercionI)
1144 -- (isIOType t) returns Just (IO,t',co)
1145 -- if co : t ~ IO t'
1146 -- returns Nothing otherwise
1147 tcSplitIOType_maybe ty
1148 = case tcSplitTyConApp_maybe ty of
1149 -- This split absolutely has to be a tcSplit, because we must
1150 -- see the IO type; and it's a newtype which is transparent to splitTyConApp.
1152 Just (io_tycon, [io_res_ty])
1153 | io_tycon `hasKey` ioTyConKey
1154 -> Just (io_tycon, io_res_ty, IdCo)
1157 | not (isRecursiveTyCon tc)
1158 , Just (ty, co1) <- instNewTyCon_maybe tc tys
1159 -- Newtypes that require a coercion are ok
1160 -> case tcSplitIOType_maybe ty of
1162 Just (tc, ty', co2) -> Just (tc, ty', co1 `mkTransCoI` co2)
1166 isFFITy :: Type -> Bool
1167 -- True for any TyCon that can possibly be an arg or result of an FFI call
1168 isFFITy ty = checkRepTyCon legalFFITyCon ty
1170 isFFIArgumentTy :: DynFlags -> Safety -> Type -> Bool
1171 -- Checks for valid argument type for a 'foreign import'
1172 isFFIArgumentTy dflags safety ty
1173 = checkRepTyCon (legalOutgoingTyCon dflags safety) ty
1175 isFFIExternalTy :: Type -> Bool
1176 -- Types that are allowed as arguments of a 'foreign export'
1177 isFFIExternalTy ty = checkRepTyCon legalFEArgTyCon ty
1179 isFFIImportResultTy :: DynFlags -> Type -> Bool
1180 isFFIImportResultTy dflags ty
1181 = checkRepTyCon (legalFIResultTyCon dflags) ty
1183 isFFIExportResultTy :: Type -> Bool
1184 isFFIExportResultTy ty = checkRepTyCon legalFEResultTyCon ty
1186 isFFIDynArgumentTy :: Type -> Bool
1187 -- The argument type of a foreign import dynamic must be Ptr, FunPtr, Addr,
1188 -- or a newtype of either.
1189 isFFIDynArgumentTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1191 isFFIDynResultTy :: Type -> Bool
1192 -- The result type of a foreign export dynamic must be Ptr, FunPtr, Addr,
1193 -- or a newtype of either.
1194 isFFIDynResultTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1196 isFFILabelTy :: Type -> Bool
1197 -- The type of a foreign label must be Ptr, FunPtr, Addr,
1198 -- or a newtype of either.
1199 isFFILabelTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1201 isFFIDotnetTy :: DynFlags -> Type -> Bool
1202 isFFIDotnetTy dflags ty
1203 = checkRepTyCon (\ tc -> (legalFIResultTyCon dflags tc ||
1204 isFFIDotnetObjTy ty || isStringTy ty)) ty
1205 -- NB: isStringTy used to look through newtypes, but
1206 -- it no longer does so. May need to adjust isFFIDotNetTy
1207 -- if we do want to look through newtypes.
1209 isFFIDotnetObjTy :: Type -> Bool
1211 = checkRepTyCon check_tc t_ty
1213 (_, t_ty) = tcSplitForAllTys ty
1214 check_tc tc = getName tc == objectTyConName
1216 toDNType :: Type -> DNType
1218 | isStringTy ty = DNString
1219 | isFFIDotnetObjTy ty = DNObject
1220 | Just (tc,argTys) <- tcSplitTyConApp_maybe ty
1221 = case lookup (getUnique tc) dn_assoc of
1224 | tc `hasKey` ioTyConKey -> toDNType (head argTys)
1225 | otherwise -> pprPanic ("toDNType: unsupported .NET type")
1226 (pprType ty <+> parens (hcat (map pprType argTys)) <+> ppr tc)
1227 | otherwise = panic "toDNType" -- Is this right?
1229 dn_assoc :: [ (Unique, DNType) ]
1230 dn_assoc = [ (unitTyConKey, DNUnit)
1231 , (intTyConKey, DNInt)
1232 , (int8TyConKey, DNInt8)
1233 , (int16TyConKey, DNInt16)
1234 , (int32TyConKey, DNInt32)
1235 , (int64TyConKey, DNInt64)
1236 , (wordTyConKey, DNInt)
1237 , (word8TyConKey, DNWord8)
1238 , (word16TyConKey, DNWord16)
1239 , (word32TyConKey, DNWord32)
1240 , (word64TyConKey, DNWord64)
1241 , (floatTyConKey, DNFloat)
1242 , (doubleTyConKey, DNDouble)
1243 , (ptrTyConKey, DNPtr)
1244 , (funPtrTyConKey, DNPtr)
1245 , (charTyConKey, DNChar)
1246 , (boolTyConKey, DNBool)
1249 checkRepTyCon :: (TyCon -> Bool) -> Type -> Bool
1250 -- Look through newtypes
1251 -- Non-recursive ones are transparent to splitTyConApp,
1252 -- but recursive ones aren't. Manuel had:
1253 -- newtype T = MkT (Ptr T)
1254 -- and wanted it to work...
1255 checkRepTyCon check_tc ty
1256 | Just (tc,_) <- splitTyConApp_maybe (repType ty) = check_tc tc
1259 checkRepTyConKey :: [Unique] -> Type -> Bool
1260 -- Like checkRepTyCon, but just looks at the TyCon key
1261 checkRepTyConKey keys
1262 = checkRepTyCon (\tc -> tyConUnique tc `elem` keys)
1265 ----------------------------------------------
1266 These chaps do the work; they are not exported
1267 ----------------------------------------------
1270 legalFEArgTyCon :: TyCon -> Bool
1272 -- It's illegal to make foreign exports that take unboxed
1273 -- arguments. The RTS API currently can't invoke such things. --SDM 7/2000
1274 = boxedMarshalableTyCon tc
1276 legalFIResultTyCon :: DynFlags -> TyCon -> Bool
1277 legalFIResultTyCon dflags tc
1278 | tc == unitTyCon = True
1279 | otherwise = marshalableTyCon dflags tc
1281 legalFEResultTyCon :: TyCon -> Bool
1282 legalFEResultTyCon tc
1283 | tc == unitTyCon = True
1284 | otherwise = boxedMarshalableTyCon tc
1286 legalOutgoingTyCon :: DynFlags -> Safety -> TyCon -> Bool
1287 -- Checks validity of types going from Haskell -> external world
1288 legalOutgoingTyCon dflags _ tc
1289 = marshalableTyCon dflags tc
1291 legalFFITyCon :: TyCon -> Bool
1292 -- True for any TyCon that can possibly be an arg or result of an FFI call
1294 = isUnLiftedTyCon tc || boxedMarshalableTyCon tc || tc == unitTyCon
1296 marshalableTyCon :: DynFlags -> TyCon -> Bool
1297 marshalableTyCon dflags tc
1298 = (dopt Opt_UnliftedFFITypes dflags
1299 && isUnLiftedTyCon tc
1300 && not (isUnboxedTupleTyCon tc)
1301 && case tyConPrimRep tc of -- Note [Marshalling VoidRep]
1304 || boxedMarshalableTyCon tc
1306 boxedMarshalableTyCon :: TyCon -> Bool
1307 boxedMarshalableTyCon tc
1308 = getUnique tc `elem` [ intTyConKey, int8TyConKey, int16TyConKey
1309 , int32TyConKey, int64TyConKey
1310 , wordTyConKey, word8TyConKey, word16TyConKey
1311 , word32TyConKey, word64TyConKey
1312 , floatTyConKey, doubleTyConKey
1313 , ptrTyConKey, funPtrTyConKey
1320 Note [Marshalling VoidRep]
1321 ~~~~~~~~~~~~~~~~~~~~~~~~~~
1322 We don't treat State# (whose PrimRep is VoidRep) as marshalable.
1323 In turn that means you can't write
1324 foreign import foo :: Int -> State# RealWorld
1326 Reason: the back end falls over with panic "primRepHint:VoidRep";
1327 and there is no compelling reason to permit it