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, isDictLikeTy,
75 tcSplitDFunTy, tcSplitDFunHead, predTyUnique,
76 mkClassPred, isInheritablePred, isIPPred,
77 isRefineableTy, isRefineablePred,
79 ---------------------------------
80 -- Foreign import and export
81 isFFIArgumentTy, -- :: DynFlags -> Safety -> Type -> Bool
82 isFFIImportResultTy, -- :: DynFlags -> Type -> Bool
83 isFFIExportResultTy, -- :: Type -> Bool
84 isFFIExternalTy, -- :: Type -> Bool
85 isFFIDynArgumentTy, -- :: Type -> Bool
86 isFFIDynResultTy, -- :: Type -> Bool
87 isFFILabelTy, -- :: Type -> Bool
88 isFFIDotnetTy, -- :: DynFlags -> Type -> Bool
89 isFFIDotnetObjTy, -- :: Type -> Bool
90 isFFITy, -- :: Type -> Bool
91 isFunPtrTy, -- :: Type -> Bool
92 tcSplitIOType_maybe, -- :: Type -> Maybe Type
93 toDNType, -- :: Type -> DNType
95 --------------------------------
96 -- Rexported from Type
97 Kind, -- Stuff to do with kinds is insensitive to pre/post Tc
98 unliftedTypeKind, liftedTypeKind, argTypeKind,
99 openTypeKind, mkArrowKind, mkArrowKinds,
100 isLiftedTypeKind, isUnliftedTypeKind, isSubOpenTypeKind,
101 isSubArgTypeKind, isSubKind, splitKindFunTys, defaultKind,
102 kindVarRef, mkKindVar,
104 Type, PredType(..), ThetaType,
105 mkForAllTy, mkForAllTys,
106 mkFunTy, mkFunTys, zipFunTys,
107 mkTyConApp, mkAppTy, mkAppTys, applyTy, applyTys,
108 mkTyVarTy, mkTyVarTys, mkTyConTy, mkPredTy, mkPredTys,
110 -- Type substitutions
111 TvSubst(..), -- Representation visible to a few friends
112 TvSubstEnv, emptyTvSubst, substEqSpec,
113 mkOpenTvSubst, zipOpenTvSubst, zipTopTvSubst, mkTopTvSubst, notElemTvSubst,
114 getTvSubstEnv, setTvSubstEnv, getTvInScope, extendTvInScope, lookupTyVar,
115 extendTvSubst, extendTvSubstList, isInScope, mkTvSubst, zipTyEnv,
116 substTy, substTys, substTyWith, substTheta, substTyVar, substTyVars, substTyVarBndr,
118 isUnLiftedType, -- Source types are always lifted
119 isUnboxedTupleType, -- Ditto
122 tidyTopType, tidyType, tidyPred, tidyTypes, tidyFreeTyVars, tidyOpenType, tidyOpenTypes,
123 tidyTyVarBndr, tidyOpenTyVar, tidyOpenTyVars, tidySkolemTyVar,
126 tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tyVarsOfTheta,
127 tcTyVarsOfType, tcTyVarsOfTypes, tcTyVarsOfPred, exactTyVarsOfType,
130 pprKind, pprParendKind,
131 pprType, pprParendType, pprTypeApp, pprTyThingCategory,
132 pprPred, pprTheta, pprThetaArrow, pprClassPred
136 #include "HsVersions.h"
168 %************************************************************************
172 %************************************************************************
174 The type checker divides the generic Type world into the
175 following more structured beasts:
177 sigma ::= forall tyvars. phi
178 -- A sigma type is a qualified type
180 -- Note that even if 'tyvars' is empty, theta
181 -- may not be: e.g. (?x::Int) => Int
183 -- Note that 'sigma' is in prenex form:
184 -- all the foralls are at the front.
185 -- A 'phi' type has no foralls to the right of
193 -- A 'tau' type has no quantification anywhere
194 -- Note that the args of a type constructor must be taus
196 | tycon tau_1 .. tau_n
200 -- In all cases, a (saturated) type synonym application is legal,
201 -- provided it expands to the required form.
204 type TcTyVar = TyVar -- Used only during type inference
205 type TcType = Type -- A TcType can have mutable type variables
206 -- Invariant on ForAllTy in TcTypes:
208 -- a cannot occur inside a MutTyVar in T; that is,
209 -- T is "flattened" before quantifying over a
211 -- These types do not have boxy type variables in them
212 type TcPredType = PredType
213 type TcThetaType = ThetaType
214 type TcSigmaType = TcType
215 type TcRhoType = TcType
216 type TcTauType = TcType
218 type TcTyVarSet = TyVarSet
220 -- These types may have boxy type variables in them
221 type BoxyTyVar = TcTyVar
222 type BoxyRhoType = TcType
223 type BoxyThetaType = TcThetaType
224 type BoxySigmaType = TcType
225 type BoxyType = TcType
229 %************************************************************************
231 \subsection{TyVarDetails}
233 %************************************************************************
235 TyVarDetails gives extra info about type variables, used during type
236 checking. It's attached to mutable type variables only.
237 It's knot-tied back to Var.lhs. There is no reason in principle
238 why Var.lhs shouldn't actually have the definition, but it "belongs" here.
241 Note [Signature skolems]
242 ~~~~~~~~~~~~~~~~~~~~~~~~
247 (x,y,z) = ([y,z], z, head x)
249 Here, x and y have type sigs, which go into the environment. We used to
250 instantiate their types with skolem constants, and push those types into
251 the RHS, so we'd typecheck the RHS with type
253 where a*, b* are skolem constants, and c is an ordinary meta type varible.
255 The trouble is that the occurrences of z in the RHS force a* and b* to
256 be the *same*, so we can't make them into skolem constants that don't unify
257 with each other. Alas.
259 One solution would be insist that in the above defn the programmer uses
260 the same type variable in both type signatures. But that takes explanation.
262 The alternative (currently implemented) is to have a special kind of skolem
263 constant, SigTv, which can unify with other SigTvs. These are *not* treated
264 as righd for the purposes of GADTs. And they are used *only* for pattern
265 bindings and mutually recursive function bindings. See the function
266 TcBinds.tcInstSig, and its use_skols parameter.
270 -- A TyVarDetails is inside a TyVar
272 = SkolemTv SkolemInfo -- A skolem constant
274 | MetaTv BoxInfo (IORef MetaDetails)
277 = BoxTv -- The contents is a (non-boxy) sigma-type
278 -- That is, this MetaTv is a "box"
280 | TauTv -- The contents is a (non-boxy) tau-type
281 -- That is, this MetaTv is an ordinary unification variable
283 | SigTv SkolemInfo -- A variant of TauTv, except that it should not be
284 -- unified with a type, only with a type variable
285 -- SigTvs are only distinguished to improve error messages
286 -- see Note [Signature skolems]
287 -- The MetaDetails, if filled in, will
288 -- always be another SigTv or a SkolemTv
291 -- A TauTv is always filled in with a tau-type, which
292 -- never contains any BoxTvs, nor any ForAlls
294 -- However, a BoxTv can contain a type that contains further BoxTvs
295 -- Notably, when typechecking an explicit list, say [e1,e2], with
296 -- expected type being a box b1, we fill in b1 with (List b2), where
297 -- b2 is another (currently empty) box.
300 = Flexi -- Flexi type variables unify to become
303 | Indirect TcType -- INVARIANT:
304 -- For a BoxTv, this type must be non-boxy
305 -- For a TauTv, this type must be a tau-type
307 -- Generally speaking, SkolemInfo should not contain location info
308 -- that is contained in the Name of the tyvar with this SkolemInfo
310 = SigSkol UserTypeCtxt -- A skolem that is created by instantiating
311 -- a programmer-supplied type signature
312 -- Location of the binding site is on the TyVar
314 -- The rest are for non-scoped skolems
315 | ClsSkol Class -- Bound at a class decl
316 | InstSkol -- Bound at an instance decl
317 | FamInstSkol -- Bound at a family instance decl
318 | PatSkol DataCon -- An existential type variable bound by a pattern for
319 -- a data constructor with an existential type. E.g.
320 -- data T = forall a. Eq a => MkT a
322 -- The pattern MkT x will allocate an existential type
324 | ArrowSkol -- An arrow form (see TcArrows)
326 | RuleSkol RuleName -- The LHS of a RULE
327 | GenSkol [TcTyVar] -- Bound when doing a subsumption check for
328 TcType -- (forall tvs. ty)
330 | RuntimeUnkSkol -- a type variable used to represent an unknown
331 -- runtime type (used in the GHCi debugger)
333 | UnkSkol -- Unhelpful info (until I improve it)
335 -------------------------------------
336 -- UserTypeCtxt describes the places where a
337 -- programmer-written type signature can occur
338 -- Like SkolemInfo, no location info
340 = FunSigCtxt Name -- Function type signature
341 -- Also used for types in SPECIALISE pragmas
342 | ExprSigCtxt -- Expression type signature
343 | ConArgCtxt Name -- Data constructor argument
344 | TySynCtxt Name -- RHS of a type synonym decl
345 | GenPatCtxt -- Pattern in generic decl
346 -- f{| a+b |} (Inl x) = ...
347 | LamPatSigCtxt -- Type sig in lambda pattern
349 | BindPatSigCtxt -- Type sig in pattern binding pattern
351 | ResSigCtxt -- Result type sig
353 | ForSigCtxt Name -- Foreign inport or export signature
354 | DefaultDeclCtxt -- Types in a default declaration
355 | SpecInstCtxt -- SPECIALISE instance pragma
357 -- Notes re TySynCtxt
358 -- We allow type synonyms that aren't types; e.g. type List = []
360 -- If the RHS mentions tyvars that aren't in scope, we'll
361 -- quantify over them:
362 -- e.g. type T = a->a
363 -- will become type T = forall a. a->a
365 -- With gla-exts that's right, but for H98 we should complain.
367 ---------------------------------
370 mkKindName :: Unique -> Name
371 mkKindName unique = mkSystemName unique kind_var_occ
373 kindVarRef :: KindVar -> IORef MetaDetails
375 ASSERT ( isTcTyVar tc )
376 case tcTyVarDetails tc of
377 MetaTv TauTv ref -> ref
378 _ -> pprPanic "kindVarRef" (ppr tc)
380 mkKindVar :: Unique -> IORef MetaDetails -> KindVar
382 = mkTcTyVar (mkKindName u)
383 tySuperKind -- not sure this is right,
384 -- do we need kind vars for
388 kind_var_occ :: OccName -- Just one for all KindVars
389 -- They may be jiggled by tidying
390 kind_var_occ = mkOccName tvName "k"
393 %************************************************************************
397 %************************************************************************
400 pprTcTyVarDetails :: TcTyVarDetails -> SDoc
402 pprTcTyVarDetails (SkolemTv _) = ptext (sLit "sk")
403 pprTcTyVarDetails (MetaTv BoxTv _) = ptext (sLit "box")
404 pprTcTyVarDetails (MetaTv TauTv _) = ptext (sLit "tau")
405 pprTcTyVarDetails (MetaTv (SigTv _) _) = ptext (sLit "sig")
407 pprUserTypeCtxt :: UserTypeCtxt -> SDoc
408 pprUserTypeCtxt (FunSigCtxt n) = ptext (sLit "the type signature for") <+> quotes (ppr n)
409 pprUserTypeCtxt ExprSigCtxt = ptext (sLit "an expression type signature")
410 pprUserTypeCtxt (ConArgCtxt c) = ptext (sLit "the type of the constructor") <+> quotes (ppr c)
411 pprUserTypeCtxt (TySynCtxt c) = ptext (sLit "the RHS of the type synonym") <+> quotes (ppr c)
412 pprUserTypeCtxt GenPatCtxt = ptext (sLit "the type pattern of a generic definition")
413 pprUserTypeCtxt LamPatSigCtxt = ptext (sLit "a pattern type signature")
414 pprUserTypeCtxt BindPatSigCtxt = ptext (sLit "a pattern type signature")
415 pprUserTypeCtxt ResSigCtxt = ptext (sLit "a result type signature")
416 pprUserTypeCtxt (ForSigCtxt n) = ptext (sLit "the foreign declaration for") <+> quotes (ppr n)
417 pprUserTypeCtxt DefaultDeclCtxt = ptext (sLit "a type in a `default' declaration")
418 pprUserTypeCtxt SpecInstCtxt = ptext (sLit "a SPECIALISE instance pragma")
421 --------------------------------
422 tidySkolemTyVar :: TidyEnv -> TcTyVar -> (TidyEnv, TcTyVar)
423 -- Tidy the type inside a GenSkol, preparatory to printing it
424 tidySkolemTyVar env tv
425 = ASSERT( isTcTyVar tv && (isSkolemTyVar tv || isSigTyVar tv ) )
426 (env1, mkTcTyVar (tyVarName tv) (tyVarKind tv) info1)
428 (env1, info1) = case tcTyVarDetails tv of
429 SkolemTv info -> (env1, SkolemTv info')
431 (env1, info') = tidy_skol_info env info
432 MetaTv (SigTv info) box -> (env1, MetaTv (SigTv info') box)
434 (env1, info') = tidy_skol_info env info
437 tidy_skol_info env (GenSkol tvs ty) = (env2, GenSkol tvs1 ty1)
439 (env1, tvs1) = tidyOpenTyVars env tvs
440 (env2, ty1) = tidyOpenType env1 ty
441 tidy_skol_info env info = (env, info)
443 pprSkolTvBinding :: TcTyVar -> SDoc
444 -- Print info about the binding of a skolem tyvar,
445 -- or nothing if we don't have anything useful to say
447 = ASSERT ( isTcTyVar tv )
448 quotes (ppr tv) <+> ppr_details (tcTyVarDetails tv)
450 ppr_details (MetaTv TauTv _) = ptext (sLit "is a meta type variable")
451 ppr_details (MetaTv BoxTv _) = ptext (sLit "is a boxy type variable")
452 ppr_details (MetaTv (SigTv info) _) = ppr_skol info
453 ppr_details (SkolemTv info) = ppr_skol info
455 ppr_skol UnkSkol = ptext (sLit "is an unknown type variable") -- Unhelpful
456 ppr_skol RuntimeUnkSkol = ptext (sLit "is an unknown runtime type")
457 ppr_skol info = sep [ptext (sLit "is a rigid type variable bound by"),
458 sep [pprSkolInfo info,
459 nest 2 (ptext (sLit "at") <+> ppr (getSrcLoc tv))]]
461 pprSkolInfo :: SkolemInfo -> SDoc
462 pprSkolInfo (SigSkol ctxt) = pprUserTypeCtxt ctxt
463 pprSkolInfo (ClsSkol cls) = ptext (sLit "the class declaration for") <+> quotes (ppr cls)
464 pprSkolInfo InstSkol = ptext (sLit "the instance declaration")
465 pprSkolInfo FamInstSkol = ptext (sLit "the family instance declaration")
466 pprSkolInfo (RuleSkol name) = ptext (sLit "the RULE") <+> doubleQuotes (ftext name)
467 pprSkolInfo ArrowSkol = ptext (sLit "the arrow form")
468 pprSkolInfo (PatSkol dc) = sep [ptext (sLit "the constructor") <+> quotes (ppr dc)]
469 pprSkolInfo (GenSkol tvs ty) = sep [ptext (sLit "the polymorphic type"),
470 nest 2 (quotes (ppr (mkForAllTys tvs ty)))]
473 -- For type variables the others are dealt with by pprSkolTvBinding.
474 -- For Insts, these cases should not happen
475 pprSkolInfo UnkSkol = panic "UnkSkol"
476 pprSkolInfo RuntimeUnkSkol = panic "RuntimeUnkSkol"
478 instance Outputable MetaDetails where
479 ppr Flexi = ptext (sLit "Flexi")
480 ppr (Indirect ty) = ptext (sLit "Indirect") <+> ppr ty
484 %************************************************************************
488 %************************************************************************
491 isImmutableTyVar :: TyVar -> Bool
494 | isTcTyVar tv = isSkolemTyVar tv
497 isTyConableTyVar, isSkolemTyVar, isExistentialTyVar,
498 isBoxyTyVar, isMetaTyVar :: TcTyVar -> Bool
501 -- True of a meta-type variable that can be filled in
502 -- with a type constructor application; in particular,
504 = ASSERT( isTcTyVar tv)
505 case tcTyVarDetails tv of
506 MetaTv BoxTv _ -> True
507 MetaTv TauTv _ -> True
508 MetaTv (SigTv {}) _ -> False
512 = ASSERT2( isTcTyVar tv, ppr tv )
513 case tcTyVarDetails tv of
517 isExistentialTyVar tv -- Existential type variable, bound by a pattern
518 = ASSERT( isTcTyVar tv )
519 case tcTyVarDetails tv of
520 SkolemTv (PatSkol {}) -> True
524 = ASSERT2( isTcTyVar tv, ppr tv )
525 case tcTyVarDetails tv of
530 = ASSERT( isTcTyVar tv )
531 case tcTyVarDetails tv of
532 MetaTv BoxTv _ -> True
535 isSigTyVar :: Var -> Bool
537 = ASSERT( isTcTyVar tv )
538 case tcTyVarDetails tv of
539 MetaTv (SigTv _) _ -> True
542 metaTvRef :: TyVar -> IORef MetaDetails
544 = ASSERT2( isTcTyVar tv, ppr tv )
545 case tcTyVarDetails tv of
547 _ -> pprPanic "metaTvRef" (ppr tv)
549 isFlexi, isIndirect :: MetaDetails -> Bool
553 isIndirect (Indirect _) = True
556 isRuntimeUnk :: TyVar -> Bool
557 isRuntimeUnk x | isTcTyVar x
558 , SkolemTv RuntimeUnkSkol <- tcTyVarDetails x = True
561 isUnk :: TyVar -> Bool
562 isUnk x | isTcTyVar x
563 , SkolemTv UnkSkol <- tcTyVarDetails x = True
568 %************************************************************************
570 \subsection{Tau, sigma and rho}
572 %************************************************************************
575 mkSigmaTy :: [TyVar] -> [PredType] -> Type -> Type
576 mkSigmaTy tyvars theta tau = mkForAllTys tyvars (mkPhiTy theta tau)
578 mkPhiTy :: [PredType] -> Type -> Type
579 mkPhiTy theta ty = foldr (\p r -> mkFunTy (mkPredTy p) r) ty theta
582 @isTauTy@ tests for nested for-alls. It should not be called on a boxy type.
585 isTauTy :: Type -> Bool
586 isTauTy ty | Just ty' <- tcView ty = isTauTy ty'
587 isTauTy (TyVarTy tv) = ASSERT( not (isTcTyVar tv && isBoxyTyVar tv) )
589 isTauTy (TyConApp tc tys) = all isTauTy tys && isTauTyCon tc
590 isTauTy (AppTy a b) = isTauTy a && isTauTy b
591 isTauTy (FunTy a b) = isTauTy a && isTauTy b
592 isTauTy (PredTy _) = True -- Don't look through source types
596 isTauTyCon :: TyCon -> Bool
597 -- Returns False for type synonyms whose expansion is a polytype
599 | isClosedSynTyCon tc = isTauTy (snd (synTyConDefn tc))
603 isBoxyTy :: TcType -> Bool
604 isBoxyTy ty = any isBoxyTyVar (varSetElems (tcTyVarsOfType ty))
606 isRigidTy :: TcType -> Bool
607 -- A type is rigid if it has no meta type variables in it
608 isRigidTy ty = all isImmutableTyVar (varSetElems (tcTyVarsOfType ty))
610 isRefineableTy :: TcType -> (Bool,Bool)
611 -- A type should have type refinements applied to it if it has
612 -- free type variables, and they are all rigid
613 isRefineableTy ty = (null tc_tvs, all isImmutableTyVar tc_tvs)
615 tc_tvs = varSetElems (tcTyVarsOfType ty)
617 isRefineablePred :: TcPredType -> Bool
618 isRefineablePred pred = not (null tc_tvs) && all isImmutableTyVar tc_tvs
620 tc_tvs = varSetElems (tcTyVarsOfPred pred)
623 getDFunTyKey :: Type -> OccName -- Get some string from a type, to be used to
624 -- construct a dictionary function name
625 getDFunTyKey ty | Just ty' <- tcView ty = getDFunTyKey ty'
626 getDFunTyKey (TyVarTy tv) = getOccName tv
627 getDFunTyKey (TyConApp tc _) = getOccName tc
628 getDFunTyKey (AppTy fun _) = getDFunTyKey fun
629 getDFunTyKey (FunTy _ _) = getOccName funTyCon
630 getDFunTyKey (ForAllTy _ t) = getDFunTyKey t
631 getDFunTyKey ty = pprPanic "getDFunTyKey" (pprType ty)
632 -- PredTy shouldn't happen
636 %************************************************************************
638 \subsection{Expanding and splitting}
640 %************************************************************************
642 These tcSplit functions are like their non-Tc analogues, but
643 a) they do not look through newtypes
644 b) they do not look through PredTys
645 c) [future] they ignore usage-type annotations
647 However, they are non-monadic and do not follow through mutable type
648 variables. It's up to you to make sure this doesn't matter.
651 tcSplitForAllTys :: Type -> ([TyVar], Type)
652 tcSplitForAllTys ty = split ty ty []
654 split orig_ty ty tvs | Just ty' <- tcView ty = split orig_ty ty' tvs
655 split _ (ForAllTy tv ty) tvs
656 | not (isCoVar tv) = split ty ty (tv:tvs)
657 split orig_ty _ tvs = (reverse tvs, orig_ty)
659 tcIsForAllTy :: Type -> Bool
660 tcIsForAllTy ty | Just ty' <- tcView ty = tcIsForAllTy ty'
661 tcIsForAllTy (ForAllTy tv _) = not (isCoVar tv)
662 tcIsForAllTy _ = False
664 tcSplitPredFunTy_maybe :: Type -> Maybe (PredType, Type)
665 -- Split off the first predicate argument from a type
666 tcSplitPredFunTy_maybe ty | Just ty' <- tcView ty = tcSplitPredFunTy_maybe ty'
667 tcSplitPredFunTy_maybe (ForAllTy tv ty)
668 | isCoVar tv = Just (coVarPred tv, ty)
669 tcSplitPredFunTy_maybe (FunTy arg res)
670 | Just p <- tcSplitPredTy_maybe arg = Just (p, res)
671 tcSplitPredFunTy_maybe _
674 tcSplitPhiTy :: Type -> (ThetaType, Type)
679 = case tcSplitPredFunTy_maybe ty of
680 Just (pred, ty) -> split ty (pred:ts)
681 Nothing -> (reverse ts, ty)
683 tcSplitSigmaTy :: Type -> ([TyVar], ThetaType, Type)
684 tcSplitSigmaTy ty = case tcSplitForAllTys ty of
685 (tvs, rho) -> case tcSplitPhiTy rho of
686 (theta, tau) -> (tvs, theta, tau)
688 -----------------------
691 -> ( [([TyVar], ThetaType)], -- forall as.C => forall bs.D
692 TcSigmaType) -- The rest of the type
694 -- We need a loop here because we are now prepared to entertain
696 -- f:: forall a. Eq a => forall b. Baz b => tau
697 -- We want to instantiate this to
698 -- f2::tau {f2 = f1 b (Baz b), f1 = f a (Eq a)}
700 tcMultiSplitSigmaTy sigma
701 = case (tcSplitSigmaTy sigma) of
702 ([], [], _) -> ([], sigma)
703 (tvs, theta, ty) -> case tcMultiSplitSigmaTy ty of
704 (pairs, rest) -> ((tvs,theta):pairs, rest)
706 -----------------------
707 tcTyConAppTyCon :: Type -> TyCon
708 tcTyConAppTyCon ty = case tcSplitTyConApp_maybe ty of
710 Nothing -> pprPanic "tcTyConAppTyCon" (pprType ty)
712 tcTyConAppArgs :: Type -> [Type]
713 tcTyConAppArgs ty = case tcSplitTyConApp_maybe ty of
714 Just (_, args) -> args
715 Nothing -> pprPanic "tcTyConAppArgs" (pprType ty)
717 tcSplitTyConApp :: Type -> (TyCon, [Type])
718 tcSplitTyConApp ty = case tcSplitTyConApp_maybe ty of
720 Nothing -> pprPanic "tcSplitTyConApp" (pprType ty)
722 tcSplitTyConApp_maybe :: Type -> Maybe (TyCon, [Type])
723 tcSplitTyConApp_maybe ty | Just ty' <- tcView ty = tcSplitTyConApp_maybe ty'
724 tcSplitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
725 tcSplitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res])
726 -- Newtypes are opaque, so they may be split
727 -- However, predicates are not treated
728 -- as tycon applications by the type checker
729 tcSplitTyConApp_maybe _ = Nothing
731 -----------------------
732 tcSplitFunTys :: Type -> ([Type], Type)
733 tcSplitFunTys ty = case tcSplitFunTy_maybe ty of
735 Just (arg,res) -> (arg:args, res')
737 (args,res') = tcSplitFunTys res
739 tcSplitFunTy_maybe :: Type -> Maybe (Type, Type)
740 tcSplitFunTy_maybe ty | Just ty' <- tcView ty = tcSplitFunTy_maybe ty'
741 tcSplitFunTy_maybe (FunTy arg res) | not (isPredTy arg) = Just (arg, res)
742 tcSplitFunTy_maybe _ = Nothing
743 -- Note the (not (isPredTy arg)) guard
744 -- Consider (?x::Int) => Bool
745 -- We don't want to treat this as a function type!
746 -- A concrete example is test tc230:
747 -- f :: () -> (?p :: ()) => () -> ()
753 -> Arity -- N: Number of desired args
754 -> ([TcSigmaType], -- Arg types (N or fewer)
755 TcSigmaType) -- The rest of the type
757 tcSplitFunTysN ty n_args
760 | Just (arg,res) <- tcSplitFunTy_maybe ty
761 = case tcSplitFunTysN res (n_args - 1) of
762 (args, res) -> (arg:args, res)
766 tcSplitFunTy :: Type -> (Type, Type)
767 tcSplitFunTy ty = expectJust "tcSplitFunTy" (tcSplitFunTy_maybe ty)
769 tcFunArgTy :: Type -> Type
770 tcFunArgTy ty = fst (tcSplitFunTy ty)
772 tcFunResultTy :: Type -> Type
773 tcFunResultTy ty = snd (tcSplitFunTy ty)
775 -----------------------
776 tcSplitAppTy_maybe :: Type -> Maybe (Type, Type)
777 tcSplitAppTy_maybe ty | Just ty' <- tcView ty = tcSplitAppTy_maybe ty'
778 tcSplitAppTy_maybe ty = repSplitAppTy_maybe ty
780 tcSplitAppTy :: Type -> (Type, Type)
781 tcSplitAppTy ty = case tcSplitAppTy_maybe ty of
783 Nothing -> pprPanic "tcSplitAppTy" (pprType ty)
785 tcSplitAppTys :: Type -> (Type, [Type])
789 go ty args = case tcSplitAppTy_maybe ty of
790 Just (ty', arg) -> go ty' (arg:args)
793 -----------------------
794 tcGetTyVar_maybe :: Type -> Maybe TyVar
795 tcGetTyVar_maybe ty | Just ty' <- tcView ty = tcGetTyVar_maybe ty'
796 tcGetTyVar_maybe (TyVarTy tv) = Just tv
797 tcGetTyVar_maybe _ = Nothing
799 tcGetTyVar :: String -> Type -> TyVar
800 tcGetTyVar msg ty = expectJust msg (tcGetTyVar_maybe ty)
802 tcIsTyVarTy :: Type -> Bool
803 tcIsTyVarTy ty = maybeToBool (tcGetTyVar_maybe ty)
805 -----------------------
806 tcSplitDFunTy :: Type -> ([TyVar], [PredType], Class, [Type])
807 -- Split the type of a dictionary function
809 = case tcSplitSigmaTy ty of { (tvs, theta, tau) ->
810 case tcSplitDFunHead tau of { (clas, tys) ->
811 (tvs, theta, clas, tys) }}
813 tcSplitDFunHead :: Type -> (Class, [Type])
815 = case tcSplitPredTy_maybe tau of
816 Just (ClassP clas tys) -> (clas, tys)
817 _ -> panic "tcSplitDFunHead"
819 tcInstHeadTyNotSynonym :: Type -> Bool
820 -- Used in Haskell-98 mode, for the argument types of an instance head
821 -- These must not be type synonyms, but everywhere else type synonyms
822 -- are transparent, so we need a special function here
823 tcInstHeadTyNotSynonym ty
825 TyConApp tc _ -> not (isSynTyCon tc)
828 tcInstHeadTyAppAllTyVars :: Type -> Bool
829 -- Used in Haskell-98 mode, for the argument types of an instance head
830 -- These must be a constructor applied to type variable arguments
831 tcInstHeadTyAppAllTyVars ty
833 TyConApp _ tys -> ok tys
834 FunTy arg res -> ok [arg, res]
837 -- Check that all the types are type variables,
838 -- and that each is distinct
839 ok tys = equalLength tvs tys && hasNoDups tvs
841 tvs = mapCatMaybes get_tv tys
843 get_tv (TyVarTy tv) = Just tv -- through synonyms
849 %************************************************************************
851 \subsection{Predicate types}
853 %************************************************************************
856 tcSplitPredTy_maybe :: Type -> Maybe PredType
857 -- Returns Just for predicates only
858 tcSplitPredTy_maybe ty | Just ty' <- tcView ty = tcSplitPredTy_maybe ty'
859 tcSplitPredTy_maybe (PredTy p) = Just p
860 tcSplitPredTy_maybe _ = Nothing
862 predTyUnique :: PredType -> Unique
863 predTyUnique (IParam n _) = getUnique (ipNameName n)
864 predTyUnique (ClassP clas _) = getUnique clas
865 predTyUnique (EqPred a b) = pprPanic "predTyUnique" (ppr (EqPred a b))
869 --------------------- Dictionary types ---------------------------------
872 mkClassPred :: Class -> [Type] -> PredType
873 mkClassPred clas tys = ClassP clas tys
875 isClassPred :: PredType -> Bool
876 isClassPred (ClassP _ _) = True
877 isClassPred _ = False
879 isTyVarClassPred :: PredType -> Bool
880 isTyVarClassPred (ClassP _ tys) = all tcIsTyVarTy tys
881 isTyVarClassPred _ = False
883 getClassPredTys_maybe :: PredType -> Maybe (Class, [Type])
884 getClassPredTys_maybe (ClassP clas tys) = Just (clas, tys)
885 getClassPredTys_maybe _ = Nothing
887 getClassPredTys :: PredType -> (Class, [Type])
888 getClassPredTys (ClassP clas tys) = (clas, tys)
889 getClassPredTys _ = panic "getClassPredTys"
891 mkDictTy :: Class -> [Type] -> Type
892 mkDictTy clas tys = mkPredTy (ClassP clas tys)
894 isDictTy :: Type -> Bool
895 isDictTy ty | Just ty' <- tcView ty = isDictTy ty'
896 isDictTy (PredTy p) = isClassPred p
899 isDictLikeTy :: Type -> Bool
900 -- Note [Dictionary-like types]
901 isDictLikeTy ty | Just ty' <- tcView ty = isDictTy ty'
902 isDictLikeTy (PredTy p) = isClassPred p
903 isDictLikeTy (TyConApp tc tys)
904 | isTupleTyCon tc = all isDictLikeTy tys
905 isDictLikeTy _ = False
908 Note [Dictionary-like types]
909 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
910 Being "dictionary-like" means either a dictionary type or a tuple thereof.
911 In GHC 6.10 we build implication constraints which construct such tuples,
912 and if we land up with a binding
915 then we want to treat t as cheap under "-fdicts-cheap" for example.
916 (Implication constraints are normally inlined, but sadly not if the
917 occurrence is itself inside an INLINE function! Until we revise the
918 handling of implication constraints, that is.) This turned out to
919 be important in getting good arities in DPH code. Example:
922 class D a where { foo :: a -> a }
923 instance C a => D (Maybe a) where { foo x = x }
925 bar :: (C a, C b) => a -> b -> (Maybe a, Maybe b)
927 bar x y = (foo (Just x), foo (Just y))
929 Then 'bar' should jolly well have arity 4 (two dicts, two args), but
930 we ended up with something like
931 bar = __inline_me__ (\d1,d2. let t :: (D (Maybe a), D (Maybe b)) = ...
934 This is all a bit ad-hoc; eg it relies on knowing that implication
935 constraints build tuples.
937 --------------------- Implicit parameters ---------------------------------
940 isIPPred :: PredType -> Bool
941 isIPPred (IParam _ _) = True
944 isInheritablePred :: PredType -> Bool
945 -- Can be inherited by a context. For example, consider
946 -- f x = let g y = (?v, y+x)
947 -- in (g 3 with ?v = 8,
949 -- The point is that g's type must be quantifed over ?v:
950 -- g :: (?v :: a) => a -> a
951 -- but it doesn't need to be quantified over the Num a dictionary
952 -- which can be free in g's rhs, and shared by both calls to g
953 isInheritablePred (ClassP _ _) = True
954 isInheritablePred (EqPred _ _) = True
955 isInheritablePred _ = False
958 --------------------- Equality predicates ---------------------------------
960 substEqSpec :: TvSubst -> [(TyVar,Type)] -> [(TcType,TcType)]
961 substEqSpec subst eq_spec = [ (substTyVar subst tv, substTy subst ty)
962 | (tv,ty) <- eq_spec]
966 %************************************************************************
968 \subsection{Predicates}
970 %************************************************************************
972 isSigmaTy returns true of any qualified type. It doesn't *necessarily* have
974 f :: (?x::Int) => Int -> Int
977 isSigmaTy :: Type -> Bool
978 isSigmaTy ty | Just ty' <- tcView ty = isSigmaTy ty'
979 isSigmaTy (ForAllTy _ _) = True
980 isSigmaTy (FunTy a _) = isPredTy a
983 isOverloadedTy :: Type -> Bool
984 -- Yes for a type of a function that might require evidence-passing
985 -- Used only by bindInstsOfLocalFuns/Pats
986 -- NB: be sure to check for type with an equality predicate; hence isCoVar
987 isOverloadedTy ty | Just ty' <- tcView ty = isOverloadedTy ty'
988 isOverloadedTy (ForAllTy tv ty) = isCoVar tv || isOverloadedTy ty
989 isOverloadedTy (FunTy a _) = isPredTy a
990 isOverloadedTy _ = False
992 isPredTy :: Type -> Bool -- Belongs in TcType because it does
993 -- not look through newtypes, or predtypes (of course)
994 isPredTy ty | Just ty' <- tcView ty = isPredTy ty'
995 isPredTy (PredTy _) = True
1000 isFloatTy, isDoubleTy, isIntegerTy, isIntTy, isWordTy, isBoolTy,
1001 isUnitTy, isCharTy :: Type -> Bool
1002 isFloatTy = is_tc floatTyConKey
1003 isDoubleTy = is_tc doubleTyConKey
1004 isIntegerTy = is_tc integerTyConKey
1005 isIntTy = is_tc intTyConKey
1006 isWordTy = is_tc wordTyConKey
1007 isBoolTy = is_tc boolTyConKey
1008 isUnitTy = is_tc unitTyConKey
1009 isCharTy = is_tc charTyConKey
1011 isStringTy :: Type -> Bool
1013 = case tcSplitTyConApp_maybe ty of
1014 Just (tc, [arg_ty]) -> tc == listTyCon && isCharTy arg_ty
1017 is_tc :: Unique -> Type -> Bool
1018 -- Newtypes are opaque to this
1019 is_tc uniq ty = case tcSplitTyConApp_maybe ty of
1020 Just (tc, _) -> uniq == getUnique tc
1025 -- NB: Currently used in places where we have already expanded type synonyms;
1026 -- hence no 'coreView'. This could, however, be changed without breaking
1028 isOpenSynTyConApp :: TcTauType -> Bool
1029 isOpenSynTyConApp (TyConApp tc tys) = isOpenSynTyCon tc &&
1030 length tys == tyConArity tc
1031 isOpenSynTyConApp _other = False
1035 %************************************************************************
1039 %************************************************************************
1042 deNoteType :: Type -> Type
1043 -- Remove all *outermost* type synonyms and other notes
1044 deNoteType ty | Just ty' <- tcView ty = deNoteType ty'
1049 tcTyVarsOfType :: Type -> TcTyVarSet
1050 -- Just the *TcTyVars* free in the type
1051 -- (Types.tyVarsOfTypes finds all free TyVars)
1052 tcTyVarsOfType (TyVarTy tv) = if isTcTyVar tv then unitVarSet tv
1054 tcTyVarsOfType (TyConApp _ tys) = tcTyVarsOfTypes tys
1055 tcTyVarsOfType (PredTy sty) = tcTyVarsOfPred sty
1056 tcTyVarsOfType (FunTy arg res) = tcTyVarsOfType arg `unionVarSet` tcTyVarsOfType res
1057 tcTyVarsOfType (AppTy fun arg) = tcTyVarsOfType fun `unionVarSet` tcTyVarsOfType arg
1058 tcTyVarsOfType (ForAllTy tyvar ty) = (tcTyVarsOfType ty `delVarSet` tyvar)
1059 `unionVarSet` tcTyVarsOfTyVar tyvar
1060 -- We do sometimes quantify over skolem TcTyVars
1062 tcTyVarsOfTyVar :: TcTyVar -> TyVarSet
1063 tcTyVarsOfTyVar tv | isCoVar tv = tcTyVarsOfType (tyVarKind tv)
1064 | otherwise = emptyVarSet
1066 tcTyVarsOfTypes :: [Type] -> TyVarSet
1067 tcTyVarsOfTypes tys = foldr (unionVarSet.tcTyVarsOfType) emptyVarSet tys
1069 tcTyVarsOfPred :: PredType -> TyVarSet
1070 tcTyVarsOfPred (IParam _ ty) = tcTyVarsOfType ty
1071 tcTyVarsOfPred (ClassP _ tys) = tcTyVarsOfTypes tys
1072 tcTyVarsOfPred (EqPred ty1 ty2) = tcTyVarsOfType ty1 `unionVarSet` tcTyVarsOfType ty2
1075 Note [Silly type synonym]
1076 ~~~~~~~~~~~~~~~~~~~~~~~~~
1079 What are the free tyvars of (T x)? Empty, of course!
1080 Here's the example that Ralf Laemmel showed me:
1081 foo :: (forall a. C u a -> C u a) -> u
1082 mappend :: Monoid u => u -> u -> u
1084 bar :: Monoid u => u
1085 bar = foo (\t -> t `mappend` t)
1086 We have to generalise at the arg to f, and we don't
1087 want to capture the constraint (Monad (C u a)) because
1088 it appears to mention a. Pretty silly, but it was useful to him.
1090 exactTyVarsOfType is used by the type checker to figure out exactly
1091 which type variables are mentioned in a type. It's also used in the
1092 smart-app checking code --- see TcExpr.tcIdApp
1094 On the other hand, consider a *top-level* definition
1095 f = (\x -> x) :: T a -> T a
1096 If we don't abstract over 'a' it'll get fixed to GHC.Prim.Any, and then
1097 if we have an application like (f "x") we get a confusing error message
1098 involving Any. So the conclusion is this: when generalising
1099 - at top level use tyVarsOfType
1100 - in nested bindings use exactTyVarsOfType
1101 See Trac #1813 for example.
1104 exactTyVarsOfType :: TcType -> TyVarSet
1105 -- Find the free type variables (of any kind)
1106 -- but *expand* type synonyms. See Note [Silly type synonym] above.
1107 exactTyVarsOfType ty
1110 go ty | Just ty' <- tcView ty = go ty' -- This is the key line
1111 go (TyVarTy tv) = unitVarSet tv
1112 go (TyConApp _ tys) = exactTyVarsOfTypes tys
1113 go (PredTy ty) = go_pred ty
1114 go (FunTy arg res) = go arg `unionVarSet` go res
1115 go (AppTy fun arg) = go fun `unionVarSet` go arg
1116 go (ForAllTy tyvar ty) = delVarSet (go ty) tyvar
1117 `unionVarSet` go_tv tyvar
1119 go_pred (IParam _ ty) = go ty
1120 go_pred (ClassP _ tys) = exactTyVarsOfTypes tys
1121 go_pred (EqPred ty1 ty2) = go ty1 `unionVarSet` go ty2
1123 go_tv tyvar | isCoVar tyvar = go (tyVarKind tyvar)
1124 | otherwise = emptyVarSet
1126 exactTyVarsOfTypes :: [TcType] -> TyVarSet
1127 exactTyVarsOfTypes tys = foldr (unionVarSet . exactTyVarsOfType) emptyVarSet tys
1130 Find the free tycons and classes of a type. This is used in the front
1131 end of the compiler.
1134 tyClsNamesOfType :: Type -> NameSet
1135 tyClsNamesOfType (TyVarTy _) = emptyNameSet
1136 tyClsNamesOfType (TyConApp tycon tys) = unitNameSet (getName tycon) `unionNameSets` tyClsNamesOfTypes tys
1137 tyClsNamesOfType (PredTy (IParam _ ty)) = tyClsNamesOfType ty
1138 tyClsNamesOfType (PredTy (ClassP cl tys)) = unitNameSet (getName cl) `unionNameSets` tyClsNamesOfTypes tys
1139 tyClsNamesOfType (PredTy (EqPred ty1 ty2)) = tyClsNamesOfType ty1 `unionNameSets` tyClsNamesOfType ty2
1140 tyClsNamesOfType (FunTy arg res) = tyClsNamesOfType arg `unionNameSets` tyClsNamesOfType res
1141 tyClsNamesOfType (AppTy fun arg) = tyClsNamesOfType fun `unionNameSets` tyClsNamesOfType arg
1142 tyClsNamesOfType (ForAllTy _ ty) = tyClsNamesOfType ty
1144 tyClsNamesOfTypes :: [Type] -> NameSet
1145 tyClsNamesOfTypes tys = foldr (unionNameSets . tyClsNamesOfType) emptyNameSet tys
1147 tyClsNamesOfDFunHead :: Type -> NameSet
1148 -- Find the free type constructors and classes
1149 -- of the head of the dfun instance type
1150 -- The 'dfun_head_type' is because of
1151 -- instance Foo a => Baz T where ...
1152 -- The decl is an orphan if Baz and T are both not locally defined,
1153 -- even if Foo *is* locally defined
1154 tyClsNamesOfDFunHead dfun_ty
1155 = case tcSplitSigmaTy dfun_ty of
1156 (_, _, head_ty) -> tyClsNamesOfType head_ty
1160 %************************************************************************
1162 \subsection[TysWiredIn-ext-type]{External types}
1164 %************************************************************************
1166 The compiler's foreign function interface supports the passing of a
1167 restricted set of types as arguments and results (the restricting factor
1171 tcSplitIOType_maybe :: Type -> Maybe (TyCon, Type, CoercionI)
1172 -- (isIOType t) returns Just (IO,t',co)
1173 -- if co : t ~ IO t'
1174 -- returns Nothing otherwise
1175 tcSplitIOType_maybe ty
1176 = case tcSplitTyConApp_maybe ty of
1177 -- This split absolutely has to be a tcSplit, because we must
1178 -- see the IO type; and it's a newtype which is transparent to splitTyConApp.
1180 Just (io_tycon, [io_res_ty])
1181 | io_tycon `hasKey` ioTyConKey
1182 -> Just (io_tycon, io_res_ty, IdCo)
1185 | not (isRecursiveTyCon tc)
1186 , Just (ty, co1) <- instNewTyCon_maybe tc tys
1187 -- Newtypes that require a coercion are ok
1188 -> case tcSplitIOType_maybe ty of
1190 Just (tc, ty', co2) -> Just (tc, ty', co1 `mkTransCoI` co2)
1194 isFFITy :: Type -> Bool
1195 -- True for any TyCon that can possibly be an arg or result of an FFI call
1196 isFFITy ty = checkRepTyCon legalFFITyCon ty
1198 isFFIArgumentTy :: DynFlags -> Safety -> Type -> Bool
1199 -- Checks for valid argument type for a 'foreign import'
1200 isFFIArgumentTy dflags safety ty
1201 = checkRepTyCon (legalOutgoingTyCon dflags safety) ty
1203 isFFIExternalTy :: Type -> Bool
1204 -- Types that are allowed as arguments of a 'foreign export'
1205 isFFIExternalTy ty = checkRepTyCon legalFEArgTyCon ty
1207 isFFIImportResultTy :: DynFlags -> Type -> Bool
1208 isFFIImportResultTy dflags ty
1209 = checkRepTyCon (legalFIResultTyCon dflags) ty
1211 isFFIExportResultTy :: Type -> Bool
1212 isFFIExportResultTy ty = checkRepTyCon legalFEResultTyCon ty
1214 isFFIDynArgumentTy :: Type -> Bool
1215 -- The argument type of a foreign import dynamic must be Ptr, FunPtr, Addr,
1216 -- or a newtype of either.
1217 isFFIDynArgumentTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1219 isFFIDynResultTy :: Type -> Bool
1220 -- The result type of a foreign export dynamic must be Ptr, FunPtr, Addr,
1221 -- or a newtype of either.
1222 isFFIDynResultTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1224 isFFILabelTy :: Type -> Bool
1225 -- The type of a foreign label must be Ptr, FunPtr, Addr,
1226 -- or a newtype of either.
1227 isFFILabelTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1229 isFFIDotnetTy :: DynFlags -> Type -> Bool
1230 isFFIDotnetTy dflags ty
1231 = checkRepTyCon (\ tc -> (legalFIResultTyCon dflags tc ||
1232 isFFIDotnetObjTy ty || isStringTy ty)) ty
1233 -- NB: isStringTy used to look through newtypes, but
1234 -- it no longer does so. May need to adjust isFFIDotNetTy
1235 -- if we do want to look through newtypes.
1237 isFFIDotnetObjTy :: Type -> Bool
1239 = checkRepTyCon check_tc t_ty
1241 (_, t_ty) = tcSplitForAllTys ty
1242 check_tc tc = getName tc == objectTyConName
1244 isFunPtrTy :: Type -> Bool
1245 isFunPtrTy = checkRepTyConKey [funPtrTyConKey]
1247 toDNType :: Type -> DNType
1249 | isStringTy ty = DNString
1250 | isFFIDotnetObjTy ty = DNObject
1251 | Just (tc,argTys) <- tcSplitTyConApp_maybe ty
1252 = case lookup (getUnique tc) dn_assoc of
1255 | tc `hasKey` ioTyConKey -> toDNType (head argTys)
1256 | otherwise -> pprPanic ("toDNType: unsupported .NET type")
1257 (pprType ty <+> parens (hcat (map pprType argTys)) <+> ppr tc)
1258 | otherwise = panic "toDNType" -- Is this right?
1260 dn_assoc :: [ (Unique, DNType) ]
1261 dn_assoc = [ (unitTyConKey, DNUnit)
1262 , (intTyConKey, DNInt)
1263 , (int8TyConKey, DNInt8)
1264 , (int16TyConKey, DNInt16)
1265 , (int32TyConKey, DNInt32)
1266 , (int64TyConKey, DNInt64)
1267 , (wordTyConKey, DNInt)
1268 , (word8TyConKey, DNWord8)
1269 , (word16TyConKey, DNWord16)
1270 , (word32TyConKey, DNWord32)
1271 , (word64TyConKey, DNWord64)
1272 , (floatTyConKey, DNFloat)
1273 , (doubleTyConKey, DNDouble)
1274 , (ptrTyConKey, DNPtr)
1275 , (funPtrTyConKey, DNPtr)
1276 , (charTyConKey, DNChar)
1277 , (boolTyConKey, DNBool)
1280 checkRepTyCon :: (TyCon -> Bool) -> Type -> Bool
1281 -- Look through newtypes, but *not* foralls
1282 -- Should work even for recursive newtypes
1283 -- eg Manuel had: newtype T = MkT (Ptr T)
1284 checkRepTyCon check_tc ty
1288 | Just (tc,tys) <- splitTyConApp_maybe ty
1289 = case carefullySplitNewType_maybe rec_nts tc tys of
1290 Just (rec_nts', ty') -> go rec_nts' ty'
1291 Nothing -> check_tc tc
1295 checkRepTyConKey :: [Unique] -> Type -> Bool
1296 -- Like checkRepTyCon, but just looks at the TyCon key
1297 checkRepTyConKey keys
1298 = checkRepTyCon (\tc -> tyConUnique tc `elem` keys)
1301 ----------------------------------------------
1302 These chaps do the work; they are not exported
1303 ----------------------------------------------
1306 legalFEArgTyCon :: TyCon -> Bool
1308 -- It's illegal to make foreign exports that take unboxed
1309 -- arguments. The RTS API currently can't invoke such things. --SDM 7/2000
1310 = boxedMarshalableTyCon tc
1312 legalFIResultTyCon :: DynFlags -> TyCon -> Bool
1313 legalFIResultTyCon dflags tc
1314 | tc == unitTyCon = True
1315 | otherwise = marshalableTyCon dflags tc
1317 legalFEResultTyCon :: TyCon -> Bool
1318 legalFEResultTyCon tc
1319 | tc == unitTyCon = True
1320 | otherwise = boxedMarshalableTyCon tc
1322 legalOutgoingTyCon :: DynFlags -> Safety -> TyCon -> Bool
1323 -- Checks validity of types going from Haskell -> external world
1324 legalOutgoingTyCon dflags _ tc
1325 = marshalableTyCon dflags tc
1327 legalFFITyCon :: TyCon -> Bool
1328 -- True for any TyCon that can possibly be an arg or result of an FFI call
1330 = isUnLiftedTyCon tc || boxedMarshalableTyCon tc || tc == unitTyCon
1332 marshalableTyCon :: DynFlags -> TyCon -> Bool
1333 marshalableTyCon dflags tc
1334 = (dopt Opt_UnliftedFFITypes dflags
1335 && isUnLiftedTyCon tc
1336 && not (isUnboxedTupleTyCon tc)
1337 && case tyConPrimRep tc of -- Note [Marshalling VoidRep]
1340 || boxedMarshalableTyCon tc
1342 boxedMarshalableTyCon :: TyCon -> Bool
1343 boxedMarshalableTyCon tc
1344 = getUnique tc `elem` [ intTyConKey, int8TyConKey, int16TyConKey
1345 , int32TyConKey, int64TyConKey
1346 , wordTyConKey, word8TyConKey, word16TyConKey
1347 , word32TyConKey, word64TyConKey
1348 , floatTyConKey, doubleTyConKey
1349 , ptrTyConKey, funPtrTyConKey
1356 Note [Marshalling VoidRep]
1357 ~~~~~~~~~~~~~~~~~~~~~~~~~~
1358 We don't treat State# (whose PrimRep is VoidRep) as marshalable.
1359 In turn that means you can't write
1360 foreign import foo :: Int -> State# RealWorld
1362 Reason: the back end falls over with panic "primRepHint:VoidRep";
1363 and there is no compelling reason to permit it