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, tcSplitPredFunTy_maybe,
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 isFunPtrTy, -- :: Type -> Bool
91 tcSplitIOType_maybe, -- :: Type -> Maybe Type
92 toDNType, -- :: Type -> DNType
94 --------------------------------
95 -- Rexported from Type
96 Kind, -- Stuff to do with kinds is insensitive to pre/post Tc
97 unliftedTypeKind, liftedTypeKind, argTypeKind,
98 openTypeKind, mkArrowKind, mkArrowKinds,
99 isLiftedTypeKind, isUnliftedTypeKind, isSubOpenTypeKind,
100 isSubArgTypeKind, isSubKind, defaultKind,
101 kindVarRef, mkKindVar,
103 Type, PredType(..), ThetaType,
104 mkForAllTy, mkForAllTys,
105 mkFunTy, mkFunTys, zipFunTys,
106 mkTyConApp, mkAppTy, mkAppTys, applyTy, applyTys,
107 mkTyVarTy, mkTyVarTys, mkTyConTy, mkPredTy, mkPredTys,
109 -- Type substitutions
110 TvSubst(..), -- Representation visible to a few friends
111 TvSubstEnv, emptyTvSubst, substEqSpec,
112 mkOpenTvSubst, zipOpenTvSubst, zipTopTvSubst, mkTopTvSubst, notElemTvSubst,
113 getTvSubstEnv, setTvSubstEnv, getTvInScope, extendTvInScope, lookupTyVar,
114 extendTvSubst, extendTvSubstList, isInScope, mkTvSubst, zipTyEnv,
115 substTy, substTys, substTyWith, substTheta, substTyVar, substTyVars, substTyVarBndr,
117 isUnLiftedType, -- Source types are always lifted
118 isUnboxedTupleType, -- Ditto
121 tidyTopType, tidyType, tidyPred, tidyTypes, tidyFreeTyVars, tidyOpenType, tidyOpenTypes,
122 tidyTyVarBndr, tidyOpenTyVar, tidyOpenTyVars, tidySkolemTyVar,
125 tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tyVarsOfTheta,
126 tcTyVarsOfType, tcTyVarsOfTypes, exactTyVarsOfType, exactTyVarsOfTypes,
128 pprKind, pprParendKind,
129 pprType, pprParendType, pprTypeApp, pprTyThingCategory,
130 pprPred, pprTheta, pprThetaArrow, pprClassPred
134 #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( isTcTyVar tv && (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 = ASSERT2( isTcTyVar tv, ppr 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 tcSplitPredFunTy_maybe :: Type -> Maybe (PredType, Type)
664 -- Split off the first predicate argument from a type
665 tcSplitPredFunTy_maybe ty | Just ty' <- tcView ty = tcSplitPredFunTy_maybe ty'
666 tcSplitPredFunTy_maybe (ForAllTy tv ty)
667 | isCoVar tv = Just (coVarPred tv, ty)
668 tcSplitPredFunTy_maybe (FunTy arg res)
669 | Just p <- tcSplitPredTy_maybe arg = Just (p, res)
670 tcSplitPredFunTy_maybe _
673 tcSplitPhiTy :: Type -> (ThetaType, Type)
678 = case tcSplitPredFunTy_maybe ty of
679 Just (pred, ty) -> split ty (pred:ts)
680 Nothing -> (reverse ts, ty)
682 tcSplitSigmaTy :: Type -> ([TyVar], ThetaType, Type)
683 tcSplitSigmaTy ty = case tcSplitForAllTys ty of
684 (tvs, rho) -> case tcSplitPhiTy rho of
685 (theta, tau) -> (tvs, theta, tau)
687 -----------------------
690 -> ( [([TyVar], ThetaType)], -- forall as.C => forall bs.D
691 TcSigmaType) -- The rest of the type
693 -- We need a loop here because we are now prepared to entertain
695 -- f:: forall a. Eq a => forall b. Baz b => tau
696 -- We want to instantiate this to
697 -- f2::tau {f2 = f1 b (Baz b), f1 = f a (Eq a)}
699 tcMultiSplitSigmaTy sigma
700 = case (tcSplitSigmaTy sigma) of
701 ([], [], _) -> ([], sigma)
702 (tvs, theta, ty) -> case tcMultiSplitSigmaTy ty of
703 (pairs, rest) -> ((tvs,theta):pairs, rest)
705 -----------------------
706 tcTyConAppTyCon :: Type -> TyCon
707 tcTyConAppTyCon ty = case tcSplitTyConApp_maybe ty of
709 Nothing -> pprPanic "tcTyConAppTyCon" (pprType ty)
711 tcTyConAppArgs :: Type -> [Type]
712 tcTyConAppArgs ty = case tcSplitTyConApp_maybe ty of
713 Just (_, args) -> args
714 Nothing -> pprPanic "tcTyConAppArgs" (pprType ty)
716 tcSplitTyConApp :: Type -> (TyCon, [Type])
717 tcSplitTyConApp ty = case tcSplitTyConApp_maybe ty of
719 Nothing -> pprPanic "tcSplitTyConApp" (pprType ty)
721 tcSplitTyConApp_maybe :: Type -> Maybe (TyCon, [Type])
722 tcSplitTyConApp_maybe ty | Just ty' <- tcView ty = tcSplitTyConApp_maybe ty'
723 tcSplitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
724 tcSplitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res])
725 -- Newtypes are opaque, so they may be split
726 -- However, predicates are not treated
727 -- as tycon applications by the type checker
728 tcSplitTyConApp_maybe _ = Nothing
730 -----------------------
731 tcSplitFunTys :: Type -> ([Type], Type)
732 tcSplitFunTys ty = case tcSplitFunTy_maybe ty of
734 Just (arg,res) -> (arg:args, res')
736 (args,res') = tcSplitFunTys res
738 tcSplitFunTy_maybe :: Type -> Maybe (Type, Type)
739 tcSplitFunTy_maybe ty | Just ty' <- tcView ty = tcSplitFunTy_maybe ty'
740 tcSplitFunTy_maybe (FunTy arg res) | not (isPredTy arg) = Just (arg, res)
741 tcSplitFunTy_maybe _ = Nothing
742 -- Note the (not (isPredTy arg)) guard
743 -- Consider (?x::Int) => Bool
744 -- We don't want to treat this as a function type!
745 -- A concrete example is test tc230:
746 -- f :: () -> (?p :: ()) => () -> ()
752 -> Arity -- N: Number of desired args
753 -> ([TcSigmaType], -- Arg types (N or fewer)
754 TcSigmaType) -- The rest of the type
756 tcSplitFunTysN ty n_args
759 | Just (arg,res) <- tcSplitFunTy_maybe ty
760 = case tcSplitFunTysN res (n_args - 1) of
761 (args, res) -> (arg:args, res)
765 tcSplitFunTy :: Type -> (Type, Type)
766 tcSplitFunTy ty = expectJust "tcSplitFunTy" (tcSplitFunTy_maybe ty)
768 tcFunArgTy :: Type -> Type
769 tcFunArgTy ty = fst (tcSplitFunTy ty)
771 tcFunResultTy :: Type -> Type
772 tcFunResultTy ty = snd (tcSplitFunTy ty)
774 -----------------------
775 tcSplitAppTy_maybe :: Type -> Maybe (Type, Type)
776 tcSplitAppTy_maybe ty | Just ty' <- tcView ty = tcSplitAppTy_maybe ty'
777 tcSplitAppTy_maybe ty = repSplitAppTy_maybe ty
779 tcSplitAppTy :: Type -> (Type, Type)
780 tcSplitAppTy ty = case tcSplitAppTy_maybe ty of
782 Nothing -> pprPanic "tcSplitAppTy" (pprType ty)
784 tcSplitAppTys :: Type -> (Type, [Type])
788 go ty args = case tcSplitAppTy_maybe ty of
789 Just (ty', arg) -> go ty' (arg:args)
792 -----------------------
793 tcGetTyVar_maybe :: Type -> Maybe TyVar
794 tcGetTyVar_maybe ty | Just ty' <- tcView ty = tcGetTyVar_maybe ty'
795 tcGetTyVar_maybe (TyVarTy tv) = Just tv
796 tcGetTyVar_maybe _ = Nothing
798 tcGetTyVar :: String -> Type -> TyVar
799 tcGetTyVar msg ty = expectJust msg (tcGetTyVar_maybe ty)
801 tcIsTyVarTy :: Type -> Bool
802 tcIsTyVarTy ty = maybeToBool (tcGetTyVar_maybe ty)
804 -----------------------
805 tcSplitDFunTy :: Type -> ([TyVar], [PredType], Class, [Type])
806 -- Split the type of a dictionary function
808 = case tcSplitSigmaTy ty of { (tvs, theta, tau) ->
809 case tcSplitDFunHead tau of { (clas, tys) ->
810 (tvs, theta, clas, tys) }}
812 tcSplitDFunHead :: Type -> (Class, [Type])
814 = case tcSplitPredTy_maybe tau of
815 Just (ClassP clas tys) -> (clas, tys)
816 _ -> panic "tcSplitDFunHead"
818 tcInstHeadTyNotSynonym :: Type -> Bool
819 -- Used in Haskell-98 mode, for the argument types of an instance head
820 -- These must not be type synonyms, but everywhere else type synonyms
821 -- are transparent, so we need a special function here
822 tcInstHeadTyNotSynonym ty
824 TyConApp tc _ -> not (isSynTyCon tc)
827 tcInstHeadTyAppAllTyVars :: Type -> Bool
828 -- Used in Haskell-98 mode, for the argument types of an instance head
829 -- These must be a constructor applied to type variable arguments
830 tcInstHeadTyAppAllTyVars ty
832 TyConApp _ tys -> ok tys
833 FunTy arg res -> ok [arg, res]
836 -- Check that all the types are type variables,
837 -- and that each is distinct
838 ok tys = equalLength tvs tys && hasNoDups tvs
840 tvs = mapCatMaybes get_tv tys
842 get_tv (TyVarTy tv) = Just tv -- through synonyms
848 %************************************************************************
850 \subsection{Predicate types}
852 %************************************************************************
855 tcSplitPredTy_maybe :: Type -> Maybe PredType
856 -- Returns Just for predicates only
857 tcSplitPredTy_maybe ty | Just ty' <- tcView ty = tcSplitPredTy_maybe ty'
858 tcSplitPredTy_maybe (PredTy p) = Just p
859 tcSplitPredTy_maybe _ = Nothing
861 predTyUnique :: PredType -> Unique
862 predTyUnique (IParam n _) = getUnique (ipNameName n)
863 predTyUnique (ClassP clas _) = getUnique clas
864 predTyUnique (EqPred a b) = pprPanic "predTyUnique" (ppr (EqPred a b))
868 --------------------- Dictionary types ---------------------------------
871 mkClassPred :: Class -> [Type] -> PredType
872 mkClassPred clas tys = ClassP clas tys
874 isClassPred :: PredType -> Bool
875 isClassPred (ClassP _ _) = True
876 isClassPred _ = False
878 isTyVarClassPred :: PredType -> Bool
879 isTyVarClassPred (ClassP _ tys) = all tcIsTyVarTy tys
880 isTyVarClassPred _ = False
882 getClassPredTys_maybe :: PredType -> Maybe (Class, [Type])
883 getClassPredTys_maybe (ClassP clas tys) = Just (clas, tys)
884 getClassPredTys_maybe _ = Nothing
886 getClassPredTys :: PredType -> (Class, [Type])
887 getClassPredTys (ClassP clas tys) = (clas, tys)
888 getClassPredTys _ = panic "getClassPredTys"
890 mkDictTy :: Class -> [Type] -> Type
891 mkDictTy clas tys = mkPredTy (ClassP clas tys)
893 isDictTy :: Type -> Bool
894 isDictTy ty | Just ty' <- tcView ty = isDictTy ty'
895 isDictTy (PredTy p) = isClassPred p
899 --------------------- Implicit parameters ---------------------------------
902 isIPPred :: PredType -> Bool
903 isIPPred (IParam _ _) = True
906 isInheritablePred :: PredType -> Bool
907 -- Can be inherited by a context. For example, consider
908 -- f x = let g y = (?v, y+x)
909 -- in (g 3 with ?v = 8,
911 -- The point is that g's type must be quantifed over ?v:
912 -- g :: (?v :: a) => a -> a
913 -- but it doesn't need to be quantified over the Num a dictionary
914 -- which can be free in g's rhs, and shared by both calls to g
915 isInheritablePred (ClassP _ _) = True
916 isInheritablePred (EqPred _ _) = True
917 isInheritablePred _ = False
920 --------------------- Equality predicates ---------------------------------
922 substEqSpec :: TvSubst -> [(TyVar,Type)] -> [(TcType,TcType)]
923 substEqSpec subst eq_spec = [ (substTyVar subst tv, substTy subst ty)
924 | (tv,ty) <- eq_spec]
927 --------------------- The stupid theta (sigh) ---------------------------------
930 dataConsStupidTheta :: [DataCon] -> ThetaType
931 -- Union the stupid thetas from all the specified constructors (non-empty)
932 -- All the constructors should have the same result type, modulo alpha conversion
933 -- The resulting ThetaType uses type variables from the *first* constructor in the list
935 -- It's here because it's used in MkId.mkRecordSelId, and in TcExpr
936 dataConsStupidTheta (con1:cons)
937 = nubBy tcEqPred all_preds
939 all_preds = dataConStupidTheta con1 ++ other_stupids
940 res_ty1 = dataConOrigResTy con1
941 other_stupids = [ substPred subst pred
943 , let (tvs, _, _, res_ty) = dataConSig con
944 Just subst = tcMatchTy (mkVarSet tvs) res_ty res_ty1
945 , pred <- dataConStupidTheta con ]
946 dataConsStupidTheta [] = panic "dataConsStupidTheta"
950 %************************************************************************
952 \subsection{Predicates}
954 %************************************************************************
956 isSigmaTy returns true of any qualified type. It doesn't *necessarily* have
958 f :: (?x::Int) => Int -> Int
961 isSigmaTy :: Type -> Bool
962 isSigmaTy ty | Just ty' <- tcView ty = isSigmaTy ty'
963 isSigmaTy (ForAllTy _ _) = True
964 isSigmaTy (FunTy a _) = isPredTy a
967 isOverloadedTy :: Type -> Bool
968 -- Yes for a type of a function that might require evidence-passing
969 -- Used only by bindInstsOfLocalFuns/Pats
970 -- NB: be sure to check for type with an equality predicate; hence isCoVar
971 isOverloadedTy ty | Just ty' <- tcView ty = isOverloadedTy ty'
972 isOverloadedTy (ForAllTy tv ty) = isCoVar tv || isOverloadedTy ty
973 isOverloadedTy (FunTy a _) = isPredTy a
974 isOverloadedTy _ = False
976 isPredTy :: Type -> Bool -- Belongs in TcType because it does
977 -- not look through newtypes, or predtypes (of course)
978 isPredTy ty | Just ty' <- tcView ty = isPredTy ty'
979 isPredTy (PredTy _) = True
984 isFloatTy, isDoubleTy, isIntegerTy, isIntTy, isWordTy, isBoolTy,
985 isUnitTy, isCharTy :: Type -> Bool
986 isFloatTy = is_tc floatTyConKey
987 isDoubleTy = is_tc doubleTyConKey
988 isIntegerTy = is_tc integerTyConKey
989 isIntTy = is_tc intTyConKey
990 isWordTy = is_tc wordTyConKey
991 isBoolTy = is_tc boolTyConKey
992 isUnitTy = is_tc unitTyConKey
993 isCharTy = is_tc charTyConKey
995 isStringTy :: Type -> Bool
997 = case tcSplitTyConApp_maybe ty of
998 Just (tc, [arg_ty]) -> tc == listTyCon && isCharTy arg_ty
1001 is_tc :: Unique -> Type -> Bool
1002 -- Newtypes are opaque to this
1003 is_tc uniq ty = case tcSplitTyConApp_maybe ty of
1004 Just (tc, _) -> uniq == getUnique tc
1009 -- NB: Currently used in places where we have already expanded type synonyms;
1010 -- hence no 'coreView'. This could, however, be changed without breaking
1012 isOpenSynTyConApp :: TcTauType -> Bool
1013 isOpenSynTyConApp (TyConApp tc tys) = isOpenSynTyCon tc &&
1014 length tys == tyConArity tc
1015 isOpenSynTyConApp _other = False
1019 %************************************************************************
1023 %************************************************************************
1026 deNoteType :: Type -> Type
1027 -- Remove all *outermost* type synonyms and other notes
1028 deNoteType ty | Just ty' <- tcView ty = deNoteType ty'
1033 tcTyVarsOfType :: Type -> TcTyVarSet
1034 -- Just the *TcTyVars* free in the type
1035 -- (Types.tyVarsOfTypes finds all free TyVars)
1036 tcTyVarsOfType (TyVarTy tv) = if isTcTyVar tv then unitVarSet tv
1038 tcTyVarsOfType (TyConApp _ tys) = tcTyVarsOfTypes tys
1039 tcTyVarsOfType (PredTy sty) = tcTyVarsOfPred sty
1040 tcTyVarsOfType (FunTy arg res) = tcTyVarsOfType arg `unionVarSet` tcTyVarsOfType res
1041 tcTyVarsOfType (AppTy fun arg) = tcTyVarsOfType fun `unionVarSet` tcTyVarsOfType arg
1042 tcTyVarsOfType (ForAllTy tyvar ty) = (tcTyVarsOfType ty `delVarSet` tyvar)
1043 `unionVarSet` tcTyVarsOfTyVar tyvar
1044 -- We do sometimes quantify over skolem TcTyVars
1046 tcTyVarsOfTyVar :: TcTyVar -> TyVarSet
1047 tcTyVarsOfTyVar tv | isCoVar tv = tcTyVarsOfType (tyVarKind tv)
1048 | otherwise = emptyVarSet
1050 tcTyVarsOfTypes :: [Type] -> TyVarSet
1051 tcTyVarsOfTypes tys = foldr (unionVarSet.tcTyVarsOfType) emptyVarSet tys
1053 tcTyVarsOfPred :: PredType -> TyVarSet
1054 tcTyVarsOfPred (IParam _ ty) = tcTyVarsOfType ty
1055 tcTyVarsOfPred (ClassP _ tys) = tcTyVarsOfTypes tys
1056 tcTyVarsOfPred (EqPred ty1 ty2) = tcTyVarsOfType ty1 `unionVarSet` tcTyVarsOfType ty2
1059 Note [Silly type synonym]
1060 ~~~~~~~~~~~~~~~~~~~~~~~~~
1063 What are the free tyvars of (T x)? Empty, of course!
1064 Here's the example that Ralf Laemmel showed me:
1065 foo :: (forall a. C u a -> C u a) -> u
1066 mappend :: Monoid u => u -> u -> u
1068 bar :: Monoid u => u
1069 bar = foo (\t -> t `mappend` t)
1070 We have to generalise at the arg to f, and we don't
1071 want to capture the constraint (Monad (C u a)) because
1072 it appears to mention a. Pretty silly, but it was useful to him.
1074 exactTyVarsOfType is used by the type checker to figure out exactly
1075 which type variables are mentioned in a type. It's also used in the
1076 smart-app checking code --- see TcExpr.tcIdApp
1078 On the other hand, consider a *top-level* definition
1079 f = (\x -> x) :: T a -> T a
1080 If we don't abstract over 'a' it'll get fixed to GHC.Prim.Any, and then
1081 if we have an application like (f "x") we get a confusing error message
1082 involving Any. So the conclusion is this: when generalising
1083 - at top level use tyVarsOfType
1084 - in nested bindings use exactTyVarsOfType
1085 See Trac #1813 for example.
1088 exactTyVarsOfType :: TcType -> TyVarSet
1089 -- Find the free type variables (of any kind)
1090 -- but *expand* type synonyms. See Note [Silly type synonym] above.
1091 exactTyVarsOfType ty
1094 go ty | Just ty' <- tcView ty = go ty' -- This is the key line
1095 go (TyVarTy tv) = unitVarSet tv
1096 go (TyConApp _ tys) = exactTyVarsOfTypes tys
1097 go (PredTy ty) = go_pred ty
1098 go (FunTy arg res) = go arg `unionVarSet` go res
1099 go (AppTy fun arg) = go fun `unionVarSet` go arg
1100 go (ForAllTy tyvar ty) = delVarSet (go ty) tyvar
1101 `unionVarSet` go_tv tyvar
1103 go_pred (IParam _ ty) = go ty
1104 go_pred (ClassP _ tys) = exactTyVarsOfTypes tys
1105 go_pred (EqPred ty1 ty2) = go ty1 `unionVarSet` go ty2
1107 go_tv tyvar | isCoVar tyvar = go (tyVarKind tyvar)
1108 | otherwise = emptyVarSet
1110 exactTyVarsOfTypes :: [TcType] -> TyVarSet
1111 exactTyVarsOfTypes tys = foldr (unionVarSet . exactTyVarsOfType) emptyVarSet tys
1114 Find the free tycons and classes of a type. This is used in the front
1115 end of the compiler.
1118 tyClsNamesOfType :: Type -> NameSet
1119 tyClsNamesOfType (TyVarTy _) = emptyNameSet
1120 tyClsNamesOfType (TyConApp tycon tys) = unitNameSet (getName tycon) `unionNameSets` tyClsNamesOfTypes tys
1121 tyClsNamesOfType (PredTy (IParam _ ty)) = tyClsNamesOfType ty
1122 tyClsNamesOfType (PredTy (ClassP cl tys)) = unitNameSet (getName cl) `unionNameSets` tyClsNamesOfTypes tys
1123 tyClsNamesOfType (PredTy (EqPred ty1 ty2)) = tyClsNamesOfType ty1 `unionNameSets` tyClsNamesOfType ty2
1124 tyClsNamesOfType (FunTy arg res) = tyClsNamesOfType arg `unionNameSets` tyClsNamesOfType res
1125 tyClsNamesOfType (AppTy fun arg) = tyClsNamesOfType fun `unionNameSets` tyClsNamesOfType arg
1126 tyClsNamesOfType (ForAllTy _ ty) = tyClsNamesOfType ty
1128 tyClsNamesOfTypes :: [Type] -> NameSet
1129 tyClsNamesOfTypes tys = foldr (unionNameSets . tyClsNamesOfType) emptyNameSet tys
1131 tyClsNamesOfDFunHead :: Type -> NameSet
1132 -- Find the free type constructors and classes
1133 -- of the head of the dfun instance type
1134 -- The 'dfun_head_type' is because of
1135 -- instance Foo a => Baz T where ...
1136 -- The decl is an orphan if Baz and T are both not locally defined,
1137 -- even if Foo *is* locally defined
1138 tyClsNamesOfDFunHead dfun_ty
1139 = case tcSplitSigmaTy dfun_ty of
1140 (_, _, head_ty) -> tyClsNamesOfType head_ty
1144 %************************************************************************
1146 \subsection[TysWiredIn-ext-type]{External types}
1148 %************************************************************************
1150 The compiler's foreign function interface supports the passing of a
1151 restricted set of types as arguments and results (the restricting factor
1155 tcSplitIOType_maybe :: Type -> Maybe (TyCon, Type, CoercionI)
1156 -- (isIOType t) returns Just (IO,t',co)
1157 -- if co : t ~ IO t'
1158 -- returns Nothing otherwise
1159 tcSplitIOType_maybe ty
1160 = case tcSplitTyConApp_maybe ty of
1161 -- This split absolutely has to be a tcSplit, because we must
1162 -- see the IO type; and it's a newtype which is transparent to splitTyConApp.
1164 Just (io_tycon, [io_res_ty])
1165 | io_tycon `hasKey` ioTyConKey
1166 -> Just (io_tycon, io_res_ty, IdCo)
1169 | not (isRecursiveTyCon tc)
1170 , Just (ty, co1) <- instNewTyCon_maybe tc tys
1171 -- Newtypes that require a coercion are ok
1172 -> case tcSplitIOType_maybe ty of
1174 Just (tc, ty', co2) -> Just (tc, ty', co1 `mkTransCoI` co2)
1178 isFFITy :: Type -> Bool
1179 -- True for any TyCon that can possibly be an arg or result of an FFI call
1180 isFFITy ty = checkRepTyCon legalFFITyCon ty
1182 isFFIArgumentTy :: DynFlags -> Safety -> Type -> Bool
1183 -- Checks for valid argument type for a 'foreign import'
1184 isFFIArgumentTy dflags safety ty
1185 = checkRepTyCon (legalOutgoingTyCon dflags safety) ty
1187 isFFIExternalTy :: Type -> Bool
1188 -- Types that are allowed as arguments of a 'foreign export'
1189 isFFIExternalTy ty = checkRepTyCon legalFEArgTyCon ty
1191 isFFIImportResultTy :: DynFlags -> Type -> Bool
1192 isFFIImportResultTy dflags ty
1193 = checkRepTyCon (legalFIResultTyCon dflags) ty
1195 isFFIExportResultTy :: Type -> Bool
1196 isFFIExportResultTy ty = checkRepTyCon legalFEResultTyCon ty
1198 isFFIDynArgumentTy :: Type -> Bool
1199 -- The argument type of a foreign import dynamic must be Ptr, FunPtr, Addr,
1200 -- or a newtype of either.
1201 isFFIDynArgumentTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1203 isFFIDynResultTy :: Type -> Bool
1204 -- The result type of a foreign export dynamic must be Ptr, FunPtr, Addr,
1205 -- or a newtype of either.
1206 isFFIDynResultTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1208 isFFILabelTy :: Type -> Bool
1209 -- The type of a foreign label must be Ptr, FunPtr, Addr,
1210 -- or a newtype of either.
1211 isFFILabelTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1213 isFFIDotnetTy :: DynFlags -> Type -> Bool
1214 isFFIDotnetTy dflags ty
1215 = checkRepTyCon (\ tc -> (legalFIResultTyCon dflags tc ||
1216 isFFIDotnetObjTy ty || isStringTy ty)) ty
1217 -- NB: isStringTy used to look through newtypes, but
1218 -- it no longer does so. May need to adjust isFFIDotNetTy
1219 -- if we do want to look through newtypes.
1221 isFFIDotnetObjTy :: Type -> Bool
1223 = checkRepTyCon check_tc t_ty
1225 (_, t_ty) = tcSplitForAllTys ty
1226 check_tc tc = getName tc == objectTyConName
1228 isFunPtrTy :: Type -> Bool
1229 isFunPtrTy = checkRepTyConKey [funPtrTyConKey]
1231 toDNType :: Type -> DNType
1233 | isStringTy ty = DNString
1234 | isFFIDotnetObjTy ty = DNObject
1235 | Just (tc,argTys) <- tcSplitTyConApp_maybe ty
1236 = case lookup (getUnique tc) dn_assoc of
1239 | tc `hasKey` ioTyConKey -> toDNType (head argTys)
1240 | otherwise -> pprPanic ("toDNType: unsupported .NET type")
1241 (pprType ty <+> parens (hcat (map pprType argTys)) <+> ppr tc)
1242 | otherwise = panic "toDNType" -- Is this right?
1244 dn_assoc :: [ (Unique, DNType) ]
1245 dn_assoc = [ (unitTyConKey, DNUnit)
1246 , (intTyConKey, DNInt)
1247 , (int8TyConKey, DNInt8)
1248 , (int16TyConKey, DNInt16)
1249 , (int32TyConKey, DNInt32)
1250 , (int64TyConKey, DNInt64)
1251 , (wordTyConKey, DNInt)
1252 , (word8TyConKey, DNWord8)
1253 , (word16TyConKey, DNWord16)
1254 , (word32TyConKey, DNWord32)
1255 , (word64TyConKey, DNWord64)
1256 , (floatTyConKey, DNFloat)
1257 , (doubleTyConKey, DNDouble)
1258 , (ptrTyConKey, DNPtr)
1259 , (funPtrTyConKey, DNPtr)
1260 , (charTyConKey, DNChar)
1261 , (boolTyConKey, DNBool)
1264 checkRepTyCon :: (TyCon -> Bool) -> Type -> Bool
1265 -- Look through newtypes
1266 -- Non-recursive ones are transparent to splitTyConApp,
1267 -- but recursive ones aren't. Manuel had:
1268 -- newtype T = MkT (Ptr T)
1269 -- and wanted it to work...
1270 checkRepTyCon check_tc ty
1271 | Just (tc,_) <- splitTyConApp_maybe (repType ty) = check_tc tc
1274 checkRepTyConKey :: [Unique] -> Type -> Bool
1275 -- Like checkRepTyCon, but just looks at the TyCon key
1276 checkRepTyConKey keys
1277 = checkRepTyCon (\tc -> tyConUnique tc `elem` keys)
1280 ----------------------------------------------
1281 These chaps do the work; they are not exported
1282 ----------------------------------------------
1285 legalFEArgTyCon :: TyCon -> Bool
1287 -- It's illegal to make foreign exports that take unboxed
1288 -- arguments. The RTS API currently can't invoke such things. --SDM 7/2000
1289 = boxedMarshalableTyCon tc
1291 legalFIResultTyCon :: DynFlags -> TyCon -> Bool
1292 legalFIResultTyCon dflags tc
1293 | tc == unitTyCon = True
1294 | otherwise = marshalableTyCon dflags tc
1296 legalFEResultTyCon :: TyCon -> Bool
1297 legalFEResultTyCon tc
1298 | tc == unitTyCon = True
1299 | otherwise = boxedMarshalableTyCon tc
1301 legalOutgoingTyCon :: DynFlags -> Safety -> TyCon -> Bool
1302 -- Checks validity of types going from Haskell -> external world
1303 legalOutgoingTyCon dflags _ tc
1304 = marshalableTyCon dflags tc
1306 legalFFITyCon :: TyCon -> Bool
1307 -- True for any TyCon that can possibly be an arg or result of an FFI call
1309 = isUnLiftedTyCon tc || boxedMarshalableTyCon tc || tc == unitTyCon
1311 marshalableTyCon :: DynFlags -> TyCon -> Bool
1312 marshalableTyCon dflags tc
1313 = (dopt Opt_UnliftedFFITypes dflags
1314 && isUnLiftedTyCon tc
1315 && not (isUnboxedTupleTyCon tc)
1316 && case tyConPrimRep tc of -- Note [Marshalling VoidRep]
1319 || boxedMarshalableTyCon tc
1321 boxedMarshalableTyCon :: TyCon -> Bool
1322 boxedMarshalableTyCon tc
1323 = getUnique tc `elem` [ intTyConKey, int8TyConKey, int16TyConKey
1324 , int32TyConKey, int64TyConKey
1325 , wordTyConKey, word8TyConKey, word16TyConKey
1326 , word32TyConKey, word64TyConKey
1327 , floatTyConKey, doubleTyConKey
1328 , ptrTyConKey, funPtrTyConKey
1335 Note [Marshalling VoidRep]
1336 ~~~~~~~~~~~~~~~~~~~~~~~~~~
1337 We don't treat State# (whose PrimRep is VoidRep) as marshalable.
1338 In turn that means you can't write
1339 foreign import foo :: Int -> State# RealWorld
1341 Reason: the back end falls over with panic "primRepHint:VoidRep";
1342 and there is no compelling reason to permit it