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, TcCoVar,
24 --------------------------------
26 UserTypeCtxt(..), pprUserTypeCtxt,
27 TcTyVarDetails(..), pprTcTyVarDetails,
28 MetaDetails(Flexi, Indirect), MetaInfo(..),
29 SkolemInfo(..), pprSkolTvBinding, pprSkolInfo,
30 isImmutableTyVar, isSkolemTyVar, isMetaTyVar, isMetaTyVarTy,
31 isSigTyVar, isExistentialTyVar, isTyConableTyVar,
33 isFlexi, isIndirect, isRuntimeUnk, isUnk,
35 --------------------------------
39 --------------------------------
41 -- These are important because they do not look through newtypes
43 tcSplitForAllTys, tcSplitPhiTy, tcSplitPredFunTy_maybe,
44 tcSplitFunTy_maybe, tcSplitFunTys, tcFunArgTy, tcFunResultTy, tcSplitFunTysN,
45 tcSplitTyConApp, tcSplitTyConApp_maybe, tcTyConAppTyCon, tcTyConAppArgs,
46 tcSplitAppTy_maybe, tcSplitAppTy, tcSplitAppTys, repSplitAppTy_maybe,
47 tcInstHeadTyNotSynonym, tcInstHeadTyAppAllTyVars,
48 tcGetTyVar_maybe, tcGetTyVar,
49 tcSplitSigmaTy, tcDeepSplitSigmaTy_maybe,
51 ---------------------------------
53 -- Again, newtypes are opaque
54 tcEqType, tcEqTypes, tcEqPred, tcCmpType, tcCmpTypes, tcCmpPred, tcEqTypeX,
56 isSigmaTy, isOverloadedTy, isRigidTy,
57 isDoubleTy, isFloatTy, isIntTy, isWordTy, isStringTy,
58 isIntegerTy, isBoolTy, isUnitTy, isCharTy,
59 isTauTy, isTauTyCon, tcIsTyVarTy, tcIsForAllTy,
62 ---------------------------------
63 -- Misc type manipulators
65 tyClsNamesOfType, tyClsNamesOfDFunHead,
68 ---------------------------------
70 getClassPredTys_maybe, getClassPredTys,
71 isClassPred, isTyVarClassPred, isEqPred,
72 mkClassPred, mkIPPred, tcSplitPredTy_maybe,
74 isPredTy, isDictTy, isDictLikeTy,
75 tcSplitDFunTy, tcSplitDFunHead, predTyUnique,
77 isRefineableTy, isRefineablePred,
79 -- * Tidying type related things up for printing
81 tidyOpenType, tidyOpenTypes,
82 tidyTyVarBndr, tidyFreeTyVars,
83 tidyOpenTyVar, tidyOpenTyVars,
84 tidyTopType, tidyPred,
85 tidyKind, tidySkolemTyVar,
87 ---------------------------------
88 -- Foreign import and export
89 isFFIArgumentTy, -- :: DynFlags -> Safety -> Type -> Bool
90 isFFIImportResultTy, -- :: DynFlags -> Type -> Bool
91 isFFIExportResultTy, -- :: Type -> Bool
92 isFFIExternalTy, -- :: Type -> Bool
93 isFFIDynArgumentTy, -- :: Type -> Bool
94 isFFIDynResultTy, -- :: Type -> Bool
95 isFFIPrimArgumentTy, -- :: DynFlags -> Type -> Bool
96 isFFIPrimResultTy, -- :: DynFlags -> Type -> Bool
97 isFFILabelTy, -- :: Type -> Bool
98 isFFIDotnetTy, -- :: DynFlags -> Type -> Bool
99 isFFIDotnetObjTy, -- :: Type -> Bool
100 isFFITy, -- :: Type -> Bool
101 isFunPtrTy, -- :: Type -> Bool
102 tcSplitIOType_maybe, -- :: Type -> Maybe Type
104 --------------------------------
105 -- Rexported from Coercion
108 --------------------------------
109 -- Rexported from Type
110 Kind, -- Stuff to do with kinds is insensitive to pre/post Tc
111 unliftedTypeKind, liftedTypeKind, argTypeKind,
112 openTypeKind, mkArrowKind, mkArrowKinds,
113 isLiftedTypeKind, isUnliftedTypeKind, isSubOpenTypeKind,
114 isSubArgTypeKind, isSubKind, splitKindFunTys, defaultKind,
115 kindVarRef, mkKindVar,
117 Type, PredType(..), ThetaType,
118 mkForAllTy, mkForAllTys,
119 mkFunTy, mkFunTys, zipFunTys,
120 mkTyConApp, mkAppTy, mkAppTys, applyTy, applyTys,
121 mkTyVarTy, mkTyVarTys, mkTyConTy, mkPredTy, mkPredTys,
123 -- Type substitutions
124 TvSubst(..), -- Representation visible to a few friends
125 TvSubstEnv, emptyTvSubst, substEqSpec,
126 mkOpenTvSubst, zipOpenTvSubst, zipTopTvSubst,
127 mkTopTvSubst, notElemTvSubst, unionTvSubst,
128 getTvSubstEnv, setTvSubstEnv, getTvInScope, extendTvInScope, lookupTyVar,
129 extendTvSubst, extendTvSubstList, isInScope, mkTvSubst, zipTyEnv,
130 substTy, substTys, substTyWith, substTheta, substTyVar, substTyVars, substTyVarBndr,
132 isUnLiftedType, -- Source types are always lifted
133 isUnboxedTupleType, -- Ditto
136 tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tyVarsOfTheta,
137 tcTyVarsOfType, tcTyVarsOfTypes, tcTyVarsOfPred, exactTyVarsOfType,
140 pprKind, pprParendKind,
141 pprType, pprParendType, pprTypeApp, pprTyThingCategory,
142 pprPred, pprTheta, pprThetaArrow, pprClassPred
146 #include "HsVersions.h"
158 import HsExpr( HsMatchContext )
174 import Data.List( mapAccumL )
178 %************************************************************************
182 %************************************************************************
184 The type checker divides the generic Type world into the
185 following more structured beasts:
187 sigma ::= forall tyvars. phi
188 -- A sigma type is a qualified type
190 -- Note that even if 'tyvars' is empty, theta
191 -- may not be: e.g. (?x::Int) => Int
193 -- Note that 'sigma' is in prenex form:
194 -- all the foralls are at the front.
195 -- A 'phi' type has no foralls to the right of
203 -- A 'tau' type has no quantification anywhere
204 -- Note that the args of a type constructor must be taus
206 | tycon tau_1 .. tau_n
210 -- In all cases, a (saturated) type synonym application is legal,
211 -- provided it expands to the required form.
214 type TcTyVar = TyVar -- Used only during type inference
215 type TcCoVar = CoVar -- Used only during type inference; mutable
216 type TcType = Type -- A TcType can have mutable type variables
217 -- Invariant on ForAllTy in TcTypes:
219 -- a cannot occur inside a MutTyVar in T; that is,
220 -- T is "flattened" before quantifying over a
222 -- These types do not have boxy type variables in them
223 type TcPredType = PredType
224 type TcThetaType = ThetaType
225 type TcSigmaType = TcType
226 type TcRhoType = TcType
227 type TcTauType = TcType
229 type TcTyVarSet = TyVarSet
233 %************************************************************************
235 \subsection{TyVarDetails}
237 %************************************************************************
239 TyVarDetails gives extra info about type variables, used during type
240 checking. It's attached to mutable type variables only.
241 It's knot-tied back to Var.lhs. There is no reason in principle
242 why Var.lhs shouldn't actually have the definition, but it "belongs" here.
245 Note [Signature skolems]
246 ~~~~~~~~~~~~~~~~~~~~~~~~
251 (x,y,z) = ([y,z], z, head x)
253 Here, x and y have type sigs, which go into the environment. We used to
254 instantiate their types with skolem constants, and push those types into
255 the RHS, so we'd typecheck the RHS with type
257 where a*, b* are skolem constants, and c is an ordinary meta type varible.
259 The trouble is that the occurrences of z in the RHS force a* and b* to
260 be the *same*, so we can't make them into skolem constants that don't unify
261 with each other. Alas.
263 One solution would be insist that in the above defn the programmer uses
264 the same type variable in both type signatures. But that takes explanation.
266 The alternative (currently implemented) is to have a special kind of skolem
267 constant, SigTv, which can unify with other SigTvs. These are *not* treated
268 as righd for the purposes of GADTs. And they are used *only* for pattern
269 bindings and mutually recursive function bindings. See the function
270 TcBinds.tcInstSig, and its use_skols parameter.
274 -- A TyVarDetails is inside a TyVar
276 = SkolemTv SkolemInfo -- A skolem constant
279 -- The "skolem" obtained by flattening during
280 -- constraint simplification
282 -- In comments we will use the notation alpha[flat = ty]
283 -- to represent a flattening skolem variable alpha
284 -- identified with type ty.
286 | MetaTv MetaInfo (IORef MetaDetails)
289 = Flexi -- Flexi type variables unify to become Indirects
293 = TauTv -- This MetaTv is an ordinary unification variable
294 -- A TauTv is always filled in with a tau-type, which
295 -- never contains any ForAlls
297 | SigTv Name -- A variant of TauTv, except that it should not be
298 -- unified with a type, only with a type variable
299 -- SigTvs are only distinguished to improve error messages
300 -- see Note [Signature skolems]
301 -- The MetaDetails, if filled in, will
302 -- always be another SigTv or a SkolemTv
303 -- The Name is the name of the function from whose
304 -- type signature we got this skolem
306 | TcsTv -- A MetaTv allocated by the constraint solver
307 -- Its particular property is that it is always "touchable"
308 -- Nevertheless, the constraint solver has to try to guess
309 -- what type to instantiate it to
311 ----------------------------------
312 -- SkolemInfo describes a site where
313 -- a) type variables are skolemised
314 -- b) an implication constraint is generated
316 = SigSkol UserTypeCtxt -- A skolem that is created by instantiating
317 -- a programmer-supplied type signature
318 -- Location of the binding site is on the TyVar
320 -- The rest are for non-scoped skolems
321 | ClsSkol Class -- Bound at a class decl
322 | InstSkol -- Bound at an instance decl
323 | FamInstSkol -- Bound at a family instance decl
324 | PatSkol -- An existential type variable bound by a pattern for
325 DataCon -- a data constructor with an existential type.
326 (HsMatchContext Name)
327 -- e.g. data T = forall a. Eq a => MkT a
329 -- The pattern MkT x will allocate an existential type
332 | ArrowSkol -- An arrow form (see TcArrows)
334 | IPSkol [IPName Name] -- Binding site of an implicit parameter
336 | RuleSkol RuleName -- The LHS of a RULE
337 | GenSkol TcType -- Bound when doing a subsumption check for ty
338 | RuntimeUnkSkol -- a type variable used to represent an unknown
339 -- runtime type (used in the GHCi debugger)
341 | NoScSkol -- Used for the "self" superclass when solving
342 -- superclasses; don't generate superclasses of me
344 | UnkSkol -- Unhelpful info (until I improve it)
346 -------------------------------------
347 -- UserTypeCtxt describes the places where a
348 -- programmer-written type signature can occur
349 -- Like SkolemInfo, no location info
351 = FunSigCtxt Name -- Function type signature
352 -- Also used for types in SPECIALISE pragmas
353 | ExprSigCtxt -- Expression type signature
354 | ConArgCtxt Name -- Data constructor argument
355 | TySynCtxt Name -- RHS of a type synonym decl
356 | GenPatCtxt -- Pattern in generic decl
357 -- f{| a+b |} (Inl x) = ...
358 | LamPatSigCtxt -- Type sig in lambda pattern
360 | BindPatSigCtxt -- Type sig in pattern binding pattern
362 | ResSigCtxt -- Result type sig
364 | ForSigCtxt Name -- Foreign inport or export signature
365 | DefaultDeclCtxt -- Types in a default declaration
366 | SpecInstCtxt -- SPECIALISE instance pragma
367 | ThBrackCtxt -- Template Haskell type brackets [t| ... |]
369 -- Notes re TySynCtxt
370 -- We allow type synonyms that aren't types; e.g. type List = []
372 -- If the RHS mentions tyvars that aren't in scope, we'll
373 -- quantify over them:
374 -- e.g. type T = a->a
375 -- will become type T = forall a. a->a
377 -- With gla-exts that's right, but for H98 we should complain.
379 ---------------------------------
382 mkKindName :: Unique -> Name
383 mkKindName unique = mkSystemName unique kind_var_occ
385 kindVarRef :: KindVar -> IORef MetaDetails
387 ASSERT ( isTcTyVar tc )
388 case tcTyVarDetails tc of
389 MetaTv TauTv ref -> ref
390 _ -> pprPanic "kindVarRef" (ppr tc)
392 mkKindVar :: Unique -> IORef MetaDetails -> KindVar
394 = mkTcTyVar (mkKindName u)
395 tySuperKind -- not sure this is right,
396 -- do we need kind vars for
400 kind_var_occ :: OccName -- Just one for all KindVars
401 -- They may be jiggled by tidying
402 kind_var_occ = mkOccName tvName "k"
405 %************************************************************************
409 %************************************************************************
412 pprTcTyVarDetails :: TcTyVarDetails -> SDoc
414 pprTcTyVarDetails (SkolemTv _) = ptext (sLit "sk")
415 pprTcTyVarDetails (FlatSkol {}) = ptext (sLit "fsk")
416 pprTcTyVarDetails (MetaTv TauTv _) = ptext (sLit "tau")
417 pprTcTyVarDetails (MetaTv TcsTv _) = ptext (sLit "tcs")
418 pprTcTyVarDetails (MetaTv (SigTv _) _) = ptext (sLit "sig")
420 pprUserTypeCtxt :: UserTypeCtxt -> SDoc
421 pprUserTypeCtxt (FunSigCtxt n) = ptext (sLit "the type signature for") <+> quotes (ppr n)
422 pprUserTypeCtxt ExprSigCtxt = ptext (sLit "an expression type signature")
423 pprUserTypeCtxt (ConArgCtxt c) = ptext (sLit "the type of the constructor") <+> quotes (ppr c)
424 pprUserTypeCtxt (TySynCtxt c) = ptext (sLit "the RHS of the type synonym") <+> quotes (ppr c)
425 pprUserTypeCtxt GenPatCtxt = ptext (sLit "the type pattern of a generic definition")
426 pprUserTypeCtxt ThBrackCtxt = ptext (sLit "a Template Haskell quotation [t|...|]")
427 pprUserTypeCtxt LamPatSigCtxt = ptext (sLit "a pattern type signature")
428 pprUserTypeCtxt BindPatSigCtxt = ptext (sLit "a pattern type signature")
429 pprUserTypeCtxt ResSigCtxt = ptext (sLit "a result type signature")
430 pprUserTypeCtxt (ForSigCtxt n) = ptext (sLit "the foreign declaration for") <+> quotes (ppr n)
431 pprUserTypeCtxt DefaultDeclCtxt = ptext (sLit "a type in a `default' declaration")
432 pprUserTypeCtxt SpecInstCtxt = ptext (sLit "a SPECIALISE instance pragma")
434 pprSkolTvBinding :: TcTyVar -> SDoc
435 -- Print info about the binding of a skolem tyvar,
436 -- or nothing if we don't have anything useful to say
438 = ASSERT ( isTcTyVar tv )
439 quotes (ppr tv) <+> ppr_details (tcTyVarDetails tv)
441 ppr_details (SkolemTv info) = ppr_skol info
442 ppr_details (FlatSkol {}) = ptext (sLit "is a flattening type variable")
443 ppr_details (MetaTv (SigTv n) _) = ptext (sLit "is bound by the type signature for")
445 ppr_details (MetaTv _ _) = ptext (sLit "is a meta type variable")
447 ppr_skol UnkSkol = ptext (sLit "is an unknown type variable") -- Unhelpful
448 ppr_skol RuntimeUnkSkol = ptext (sLit "is an unknown runtime type")
449 ppr_skol info = sep [ptext (sLit "is a rigid type variable bound by"),
450 sep [pprSkolInfo info,
451 nest 2 (ptext (sLit "at") <+> ppr (getSrcLoc tv))]]
453 pprSkolInfo :: SkolemInfo -> SDoc
454 -- Complete the sentence "is a rigid type variable bound by..."
455 pprSkolInfo (SigSkol ctxt) = pprUserTypeCtxt ctxt
456 pprSkolInfo (IPSkol ips) = ptext (sLit "the implicit-parameter bindings for")
457 <+> pprWithCommas ppr ips
458 pprSkolInfo (ClsSkol cls) = ptext (sLit "the class declaration for") <+> quotes (ppr cls)
459 pprSkolInfo InstSkol = ptext (sLit "the instance declaration")
460 pprSkolInfo NoScSkol = ptext (sLit "the instance declaration (self)")
461 pprSkolInfo FamInstSkol = ptext (sLit "the family instance declaration")
462 pprSkolInfo (RuleSkol name) = ptext (sLit "the RULE") <+> doubleQuotes (ftext name)
463 pprSkolInfo ArrowSkol = ptext (sLit "the arrow form")
464 pprSkolInfo (PatSkol dc _) = sep [ ptext (sLit "a pattern with constructor")
465 , ppr dc <+> dcolon <+> ppr (dataConUserType dc) ]
466 pprSkolInfo (GenSkol ty) = sep [ ptext (sLit "the polymorphic type")
470 -- For type variables the others are dealt with by pprSkolTvBinding.
471 -- For Insts, these cases should not happen
472 pprSkolInfo UnkSkol = WARN( True, text "pprSkolInfo: UnkSkol" ) ptext (sLit "UnkSkol")
473 pprSkolInfo RuntimeUnkSkol = WARN( True, text "pprSkolInfo: RuntimeUnkSkol" ) ptext (sLit "RuntimeUnkSkol")
475 instance Outputable MetaDetails where
476 ppr Flexi = ptext (sLit "Flexi")
477 ppr (Indirect ty) = ptext (sLit "Indirect") <+> ppr ty
481 %************************************************************************
483 \subsection{TidyType}
485 %************************************************************************
488 -- | This tidies up a type for printing in an error message, or in
489 -- an interface file.
491 -- It doesn't change the uniques at all, just the print names.
492 tidyTyVarBndr :: TidyEnv -> TyVar -> (TidyEnv, TyVar)
493 tidyTyVarBndr env@(tidy_env, subst) tyvar
494 = case tidyOccName tidy_env (getOccName name) of
495 (tidy', occ') -> ((tidy', subst'), tyvar'')
497 subst' = extendVarEnv subst tyvar tyvar''
498 tyvar' = setTyVarName tyvar name'
499 name' = tidyNameOcc name occ'
500 -- Don't forget to tidy the kind for coercions!
501 tyvar'' | isCoVar tyvar = setTyVarKind tyvar' kind'
503 kind' = tidyType env (tyVarKind tyvar)
505 name = tyVarName tyvar
508 tidyFreeTyVars :: TidyEnv -> TyVarSet -> TidyEnv
509 -- ^ Add the free 'TyVar's to the env in tidy form,
510 -- so that we can tidy the type they are free in
511 tidyFreeTyVars env tyvars = fst (tidyOpenTyVars env (varSetElems tyvars))
514 tidyOpenTyVars :: TidyEnv -> [TyVar] -> (TidyEnv, [TyVar])
515 tidyOpenTyVars env tyvars = mapAccumL tidyOpenTyVar env tyvars
518 tidyOpenTyVar :: TidyEnv -> TyVar -> (TidyEnv, TyVar)
519 -- ^ Treat a new 'TyVar' as a binder, and give it a fresh tidy name
520 -- using the environment if one has not already been allocated. See
521 -- also 'tidyTyVarBndr'
522 tidyOpenTyVar env@(_, subst) tyvar
523 = case lookupVarEnv subst tyvar of
524 Just tyvar' -> (env, tyvar') -- Already substituted
525 Nothing -> tidyTyVarBndr env tyvar -- Treat it as a binder
528 tidyType :: TidyEnv -> Type -> Type
529 tidyType env@(_, subst) ty
532 go (TyVarTy tv) = case lookupVarEnv subst tv of
534 Just tv' -> expand tv'
535 go (TyConApp tycon tys) = let args = map go tys
536 in args `seqList` TyConApp tycon args
537 go (PredTy sty) = PredTy (tidyPred env sty)
538 go (AppTy fun arg) = (AppTy $! (go fun)) $! (go arg)
539 go (FunTy fun arg) = (FunTy $! (go fun)) $! (go arg)
540 go (ForAllTy tv ty) = ForAllTy tvp $! (tidyType envp ty)
542 (envp, tvp) = tidyTyVarBndr env tv
544 -- Expand FlatSkols, the skolems introduced by flattening process
545 -- We don't want to show them in type error messages
546 expand tv | isTcTyVar tv
547 , FlatSkol ty <- tcTyVarDetails tv
553 tidyTypes :: TidyEnv -> [Type] -> [Type]
554 tidyTypes env tys = map (tidyType env) tys
557 tidyPred :: TidyEnv -> PredType -> PredType
558 tidyPred env (IParam n ty) = IParam n (tidyType env ty)
559 tidyPred env (ClassP clas tys) = ClassP clas (tidyTypes env tys)
560 tidyPred env (EqPred ty1 ty2) = EqPred (tidyType env ty1) (tidyType env ty2)
563 -- | Grabs the free type variables, tidies them
564 -- and then uses 'tidyType' to work over the type itself
565 tidyOpenType :: TidyEnv -> Type -> (TidyEnv, Type)
567 = (env', tidyType env' ty)
569 env' = tidyFreeTyVars env (tyVarsOfType ty)
572 tidyOpenTypes :: TidyEnv -> [Type] -> (TidyEnv, [Type])
573 tidyOpenTypes env tys = mapAccumL tidyOpenType env tys
576 -- | Calls 'tidyType' on a top-level type (i.e. with an empty tidying environment)
577 tidyTopType :: Type -> Type
578 tidyTopType ty = tidyType emptyTidyEnv ty
581 tidySkolemTyVar :: TidyEnv -> TcTyVar -> (TidyEnv, TcTyVar)
582 -- Tidy the type inside a GenSkol, preparatory to printing it
583 tidySkolemTyVar env tv
584 = ASSERT( isTcTyVar tv && (isSkolemTyVar tv || isSigTyVar tv ) )
585 (env1, mkTcTyVar (tyVarName tv) (tyVarKind tv) info1)
587 (env1, info1) = case tcTyVarDetails tv of
588 SkolemTv info -> (env1, SkolemTv info')
590 (env1, info') = tidy_skol_info env info
593 tidy_skol_info env (GenSkol ty) = (env1, GenSkol ty1)
595 (env1, ty1) = tidyOpenType env ty
596 tidy_skol_info env info = (env, info)
599 tidyKind :: TidyEnv -> Kind -> (TidyEnv, Kind)
600 tidyKind env k = tidyOpenType env k
604 %************************************************************************
608 %************************************************************************
611 isImmutableTyVar :: TyVar -> Bool
614 | isTcTyVar tv = isSkolemTyVar tv
617 isTyConableTyVar, isSkolemTyVar, isExistentialTyVar,
618 isMetaTyVar :: TcTyVar -> Bool
621 -- True of a meta-type variable that can be filled in
622 -- with a type constructor application; in particular,
624 = ASSERT( isTcTyVar tv)
625 case tcTyVarDetails tv of
626 MetaTv (SigTv _) _ -> False
630 = ASSERT2( isTcTyVar tv, ppr tv )
631 case tcTyVarDetails tv of
636 isExistentialTyVar tv -- Existential type variable, bound by a pattern
637 = ASSERT( isTcTyVar tv )
638 case tcTyVarDetails tv of
639 SkolemTv (PatSkol {}) -> True
643 = ASSERT2( isTcTyVar tv, ppr tv )
644 case tcTyVarDetails tv of
648 isMetaTyVarTy :: TcType -> Bool
649 isMetaTyVarTy (TyVarTy tv) = isMetaTyVar tv
650 isMetaTyVarTy _ = False
652 isSigTyVar :: Var -> Bool
654 = ASSERT( isTcTyVar tv )
655 case tcTyVarDetails tv of
656 MetaTv (SigTv _) _ -> True
659 metaTvRef :: TyVar -> IORef MetaDetails
661 = ASSERT2( isTcTyVar tv, ppr tv )
662 case tcTyVarDetails tv of
664 _ -> pprPanic "metaTvRef" (ppr tv)
666 isFlexi, isIndirect :: MetaDetails -> Bool
670 isIndirect (Indirect _) = True
673 isRuntimeUnk :: TyVar -> Bool
674 isRuntimeUnk x | isTcTyVar x
675 , SkolemTv RuntimeUnkSkol <- tcTyVarDetails x = True
678 isUnk :: TyVar -> Bool
679 isUnk x | isTcTyVar x
680 , SkolemTv UnkSkol <- tcTyVarDetails x = True
685 %************************************************************************
687 \subsection{Tau, sigma and rho}
689 %************************************************************************
692 mkSigmaTy :: [TyVar] -> [PredType] -> Type -> Type
693 mkSigmaTy tyvars theta tau = mkForAllTys tyvars (mkPhiTy theta tau)
695 mkPhiTy :: [PredType] -> Type -> Type
696 mkPhiTy theta ty = foldr (\p r -> mkFunTy (mkPredTy p) r) ty theta
699 @isTauTy@ tests for nested for-alls. It should not be called on a boxy type.
702 isTauTy :: Type -> Bool
703 isTauTy ty | Just ty' <- tcView ty = isTauTy ty'
704 isTauTy (TyVarTy _) = True
705 isTauTy (TyConApp tc tys) = all isTauTy tys && isTauTyCon tc
706 isTauTy (AppTy a b) = isTauTy a && isTauTy b
707 isTauTy (FunTy a b) = isTauTy a && isTauTy b
708 isTauTy (PredTy _) = True -- Don't look through source types
712 isTauTyCon :: TyCon -> Bool
713 -- Returns False for type synonyms whose expansion is a polytype
715 | isClosedSynTyCon tc = isTauTy (snd (synTyConDefn tc))
719 isRigidTy :: TcType -> Bool
720 -- A type is rigid if it has no meta type variables in it
721 isRigidTy ty = all isImmutableTyVar (varSetElems (tcTyVarsOfType ty))
723 isRefineableTy :: TcType -> (Bool,Bool)
724 -- A type should have type refinements applied to it if it has
725 -- free type variables, and they are all rigid
726 isRefineableTy ty = (null tc_tvs, all isImmutableTyVar tc_tvs)
728 tc_tvs = varSetElems (tcTyVarsOfType ty)
730 isRefineablePred :: TcPredType -> Bool
731 isRefineablePred pred = not (null tc_tvs) && all isImmutableTyVar tc_tvs
733 tc_tvs = varSetElems (tcTyVarsOfPred pred)
736 getDFunTyKey :: Type -> OccName -- Get some string from a type, to be used to
737 -- construct a dictionary function name
738 getDFunTyKey ty | Just ty' <- tcView ty = getDFunTyKey ty'
739 getDFunTyKey (TyVarTy tv) = getOccName tv
740 getDFunTyKey (TyConApp tc _) = getOccName tc
741 getDFunTyKey (AppTy fun _) = getDFunTyKey fun
742 getDFunTyKey (FunTy _ _) = getOccName funTyCon
743 getDFunTyKey (ForAllTy _ t) = getDFunTyKey t
744 getDFunTyKey ty = pprPanic "getDFunTyKey" (pprType ty)
745 -- PredTy shouldn't happen
749 %************************************************************************
751 \subsection{Expanding and splitting}
753 %************************************************************************
755 These tcSplit functions are like their non-Tc analogues, but
756 a) they do not look through newtypes
757 b) they do not look through PredTys
759 However, they are non-monadic and do not follow through mutable type
760 variables. It's up to you to make sure this doesn't matter.
763 tcSplitForAllTys :: Type -> ([TyVar], Type)
764 tcSplitForAllTys ty = split ty ty []
766 split orig_ty ty tvs | Just ty' <- tcView ty = split orig_ty ty' tvs
767 split _ (ForAllTy tv ty) tvs
768 | not (isCoVar tv) = split ty ty (tv:tvs)
769 split orig_ty _ tvs = (reverse tvs, orig_ty)
771 tcIsForAllTy :: Type -> Bool
772 tcIsForAllTy ty | Just ty' <- tcView ty = tcIsForAllTy ty'
773 tcIsForAllTy (ForAllTy tv _) = not (isCoVar tv)
774 tcIsForAllTy _ = False
776 tcSplitPredFunTy_maybe :: Type -> Maybe (PredType, Type)
777 -- Split off the first predicate argument from a type
778 tcSplitPredFunTy_maybe ty | Just ty' <- tcView ty = tcSplitPredFunTy_maybe ty'
779 tcSplitPredFunTy_maybe (ForAllTy tv ty)
780 | isCoVar tv = Just (coVarPred tv, ty)
781 tcSplitPredFunTy_maybe (FunTy arg res)
782 | Just p <- tcSplitPredTy_maybe arg = Just (p, res)
783 tcSplitPredFunTy_maybe _
786 tcSplitPhiTy :: Type -> (ThetaType, Type)
791 = case tcSplitPredFunTy_maybe ty of
792 Just (pred, ty) -> split ty (pred:ts)
793 Nothing -> (reverse ts, ty)
795 tcSplitSigmaTy :: Type -> ([TyVar], ThetaType, Type)
796 tcSplitSigmaTy ty = case tcSplitForAllTys ty of
797 (tvs, rho) -> case tcSplitPhiTy rho of
798 (theta, tau) -> (tvs, theta, tau)
800 -----------------------
801 tcDeepSplitSigmaTy_maybe
802 :: TcSigmaType -> Maybe ([TcType], [TyVar], ThetaType, TcSigmaType)
803 -- Looks for a *non-trivial* quantified type, under zero or more function arrows
804 -- By "non-trivial" we mean either tyvars or constraints are non-empty
806 tcDeepSplitSigmaTy_maybe ty
807 | Just (arg_ty, res_ty) <- tcSplitFunTy_maybe ty
808 , Just (arg_tys, tvs, theta, rho) <- tcDeepSplitSigmaTy_maybe res_ty
809 = Just (arg_ty:arg_tys, tvs, theta, rho)
811 | (tvs, theta, rho) <- tcSplitSigmaTy ty
812 , not (null tvs && null theta)
813 = Just ([], tvs, theta, rho)
815 | otherwise = Nothing
817 -----------------------
818 tcTyConAppTyCon :: Type -> TyCon
819 tcTyConAppTyCon ty = case tcSplitTyConApp_maybe ty of
821 Nothing -> pprPanic "tcTyConAppTyCon" (pprType ty)
823 tcTyConAppArgs :: Type -> [Type]
824 tcTyConAppArgs ty = case tcSplitTyConApp_maybe ty of
825 Just (_, args) -> args
826 Nothing -> pprPanic "tcTyConAppArgs" (pprType ty)
828 tcSplitTyConApp :: Type -> (TyCon, [Type])
829 tcSplitTyConApp ty = case tcSplitTyConApp_maybe ty of
831 Nothing -> pprPanic "tcSplitTyConApp" (pprType ty)
833 tcSplitTyConApp_maybe :: Type -> Maybe (TyCon, [Type])
834 tcSplitTyConApp_maybe ty | Just ty' <- tcView ty = tcSplitTyConApp_maybe ty'
835 tcSplitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
836 tcSplitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res])
837 -- Newtypes are opaque, so they may be split
838 -- However, predicates are not treated
839 -- as tycon applications by the type checker
840 tcSplitTyConApp_maybe _ = Nothing
842 -----------------------
843 tcSplitFunTys :: Type -> ([Type], Type)
844 tcSplitFunTys ty = case tcSplitFunTy_maybe ty of
846 Just (arg,res) -> (arg:args, res')
848 (args,res') = tcSplitFunTys res
850 tcSplitFunTy_maybe :: Type -> Maybe (Type, Type)
851 tcSplitFunTy_maybe ty | Just ty' <- tcView ty = tcSplitFunTy_maybe ty'
852 tcSplitFunTy_maybe (FunTy arg res) | not (isPredTy arg) = Just (arg, res)
853 tcSplitFunTy_maybe _ = Nothing
854 -- Note the (not (isPredTy arg)) guard
855 -- Consider (?x::Int) => Bool
856 -- We don't want to treat this as a function type!
857 -- A concrete example is test tc230:
858 -- f :: () -> (?p :: ()) => () -> ()
864 -> Arity -- N: Number of desired args
865 -> ([TcSigmaType], -- Arg types (N or fewer)
866 TcSigmaType) -- The rest of the type
868 tcSplitFunTysN ty n_args
871 | Just (arg,res) <- tcSplitFunTy_maybe ty
872 = case tcSplitFunTysN res (n_args - 1) of
873 (args, res) -> (arg:args, res)
877 tcSplitFunTy :: Type -> (Type, Type)
878 tcSplitFunTy ty = expectJust "tcSplitFunTy" (tcSplitFunTy_maybe ty)
880 tcFunArgTy :: Type -> Type
881 tcFunArgTy ty = fst (tcSplitFunTy ty)
883 tcFunResultTy :: Type -> Type
884 tcFunResultTy ty = snd (tcSplitFunTy ty)
886 -----------------------
887 tcSplitAppTy_maybe :: Type -> Maybe (Type, Type)
888 tcSplitAppTy_maybe ty | Just ty' <- tcView ty = tcSplitAppTy_maybe ty'
889 tcSplitAppTy_maybe ty = repSplitAppTy_maybe ty
891 tcSplitAppTy :: Type -> (Type, Type)
892 tcSplitAppTy ty = case tcSplitAppTy_maybe ty of
894 Nothing -> pprPanic "tcSplitAppTy" (pprType ty)
896 tcSplitAppTys :: Type -> (Type, [Type])
900 go ty args = case tcSplitAppTy_maybe ty of
901 Just (ty', arg) -> go ty' (arg:args)
904 -----------------------
905 tcGetTyVar_maybe :: Type -> Maybe TyVar
906 tcGetTyVar_maybe ty | Just ty' <- tcView ty = tcGetTyVar_maybe ty'
907 tcGetTyVar_maybe (TyVarTy tv) = Just tv
908 tcGetTyVar_maybe _ = Nothing
910 tcGetTyVar :: String -> Type -> TyVar
911 tcGetTyVar msg ty = expectJust msg (tcGetTyVar_maybe ty)
913 tcIsTyVarTy :: Type -> Bool
914 tcIsTyVarTy ty = maybeToBool (tcGetTyVar_maybe ty)
916 -----------------------
917 tcSplitDFunTy :: Type -> ([TyVar], Class, [Type])
918 -- Split the type of a dictionary function
919 -- We don't use tcSplitSigmaTy, because a DFun may (with NDP)
920 -- have non-Pred arguments, such as
921 -- df :: forall m. (forall b. Eq b => Eq (m b)) -> C m
923 = case tcSplitForAllTys ty of { (tvs, rho) ->
924 case tcSplitDFunHead (drop_pred_tys rho) of { (clas, tys) ->
927 -- Discard the context of the dfun. This can be a mix of
928 -- coercion and class constraints; or (in the general NDP case)
929 -- some other function argument
930 drop_pred_tys ty | Just ty' <- tcView ty = drop_pred_tys ty'
931 drop_pred_tys (ForAllTy tv ty) = ASSERT( isCoVar tv ) drop_pred_tys ty
932 drop_pred_tys (FunTy _ ty) = drop_pred_tys ty
933 drop_pred_tys ty = ty
935 tcSplitDFunHead :: Type -> (Class, [Type])
937 = case tcSplitPredTy_maybe tau of
938 Just (ClassP clas tys) -> (clas, tys)
939 _ -> pprPanic "tcSplitDFunHead" (ppr tau)
941 tcInstHeadTyNotSynonym :: Type -> Bool
942 -- Used in Haskell-98 mode, for the argument types of an instance head
943 -- These must not be type synonyms, but everywhere else type synonyms
944 -- are transparent, so we need a special function here
945 tcInstHeadTyNotSynonym ty
947 TyConApp tc _ -> not (isSynTyCon tc)
950 tcInstHeadTyAppAllTyVars :: Type -> Bool
951 -- Used in Haskell-98 mode, for the argument types of an instance head
952 -- These must be a constructor applied to type variable arguments
953 tcInstHeadTyAppAllTyVars ty
955 TyConApp _ tys -> ok tys
956 FunTy arg res -> ok [arg, res]
959 -- Check that all the types are type variables,
960 -- and that each is distinct
961 ok tys = equalLength tvs tys && hasNoDups tvs
963 tvs = mapCatMaybes get_tv tys
965 get_tv (TyVarTy tv) = Just tv -- through synonyms
971 %************************************************************************
973 \subsection{Predicate types}
975 %************************************************************************
978 evVarPred :: EvVar -> PredType
980 = case tcSplitPredTy_maybe (varType var) of
982 Nothing -> pprPanic "evVarPred" (ppr var <+> ppr (varType var))
984 tcSplitPredTy_maybe :: Type -> Maybe PredType
985 -- Returns Just for predicates only
986 tcSplitPredTy_maybe ty | Just ty' <- tcView ty = tcSplitPredTy_maybe ty'
987 tcSplitPredTy_maybe (PredTy p) = Just p
988 tcSplitPredTy_maybe _ = Nothing
990 predTyUnique :: PredType -> Unique
991 predTyUnique (IParam n _) = getUnique (ipNameName n)
992 predTyUnique (ClassP clas _) = getUnique clas
993 predTyUnique (EqPred a b) = pprPanic "predTyUnique" (ppr (EqPred a b))
997 --------------------- Dictionary types ---------------------------------
1000 mkClassPred :: Class -> [Type] -> PredType
1001 mkClassPred clas tys = ClassP clas tys
1003 isClassPred :: PredType -> Bool
1004 isClassPred (ClassP _ _) = True
1005 isClassPred _ = False
1007 isTyVarClassPred :: PredType -> Bool
1008 isTyVarClassPred (ClassP _ tys) = all tcIsTyVarTy tys
1009 isTyVarClassPred _ = False
1011 getClassPredTys_maybe :: PredType -> Maybe (Class, [Type])
1012 getClassPredTys_maybe (ClassP clas tys) = Just (clas, tys)
1013 getClassPredTys_maybe _ = Nothing
1015 getClassPredTys :: PredType -> (Class, [Type])
1016 getClassPredTys (ClassP clas tys) = (clas, tys)
1017 getClassPredTys _ = panic "getClassPredTys"
1019 mkDictTy :: Class -> [Type] -> Type
1020 mkDictTy clas tys = mkPredTy (ClassP clas tys)
1024 isDictLikeTy :: Type -> Bool
1025 -- Note [Dictionary-like types]
1026 isDictLikeTy ty | Just ty' <- tcView ty = isDictTy ty'
1027 isDictLikeTy (PredTy p) = isClassPred p
1028 isDictLikeTy (TyConApp tc tys)
1029 | isTupleTyCon tc = all isDictLikeTy tys
1030 isDictLikeTy _ = False
1033 Note [Dictionary-like types]
1034 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1035 Being "dictionary-like" means either a dictionary type or a tuple thereof.
1036 In GHC 6.10 we build implication constraints which construct such tuples,
1037 and if we land up with a binding
1038 t :: (C [a], Eq [a])
1040 then we want to treat t as cheap under "-fdicts-cheap" for example.
1041 (Implication constraints are normally inlined, but sadly not if the
1042 occurrence is itself inside an INLINE function! Until we revise the
1043 handling of implication constraints, that is.) This turned out to
1044 be important in getting good arities in DPH code. Example:
1047 class D a where { foo :: a -> a }
1048 instance C a => D (Maybe a) where { foo x = x }
1050 bar :: (C a, C b) => a -> b -> (Maybe a, Maybe b)
1052 bar x y = (foo (Just x), foo (Just y))
1054 Then 'bar' should jolly well have arity 4 (two dicts, two args), but
1055 we ended up with something like
1056 bar = __inline_me__ (\d1,d2. let t :: (D (Maybe a), D (Maybe b)) = ...
1059 This is all a bit ad-hoc; eg it relies on knowing that implication
1060 constraints build tuples.
1062 --------------------- Implicit parameters ---------------------------------
1065 mkIPPred :: IPName Name -> Type -> PredType
1066 mkIPPred ip ty = IParam ip ty
1068 isIPPred :: PredType -> Bool
1069 isIPPred (IParam _ _) = True
1073 --------------------- Equality predicates ---------------------------------
1075 substEqSpec :: TvSubst -> [(TyVar,Type)] -> [(TcType,TcType)]
1076 substEqSpec subst eq_spec = [ (substTyVar subst tv, substTy subst ty)
1077 | (tv,ty) <- eq_spec]
1081 %************************************************************************
1083 \subsection{Predicates}
1085 %************************************************************************
1087 isSigmaTy returns true of any qualified type. It doesn't *necessarily* have
1089 f :: (?x::Int) => Int -> Int
1092 isSigmaTy :: Type -> Bool
1093 isSigmaTy ty | Just ty' <- tcView ty = isSigmaTy ty'
1094 isSigmaTy (ForAllTy _ _) = True
1095 isSigmaTy (FunTy a _) = isPredTy a
1098 isOverloadedTy :: Type -> Bool
1099 -- Yes for a type of a function that might require evidence-passing
1100 -- Used only by bindLocalMethods
1101 -- NB: be sure to check for type with an equality predicate; hence isCoVar
1102 isOverloadedTy ty | Just ty' <- tcView ty = isOverloadedTy ty'
1103 isOverloadedTy (ForAllTy tv ty) = isCoVar tv || isOverloadedTy ty
1104 isOverloadedTy (FunTy a _) = isPredTy a
1105 isOverloadedTy _ = False
1107 isPredTy :: Type -> Bool -- Belongs in TcType because it does
1108 -- not look through newtypes, or predtypes (of course)
1109 isPredTy ty | Just ty' <- tcView ty = isPredTy ty'
1110 isPredTy (PredTy _) = True
1115 isFloatTy, isDoubleTy, isIntegerTy, isIntTy, isWordTy, isBoolTy,
1116 isUnitTy, isCharTy :: Type -> Bool
1117 isFloatTy = is_tc floatTyConKey
1118 isDoubleTy = is_tc doubleTyConKey
1119 isIntegerTy = is_tc integerTyConKey
1120 isIntTy = is_tc intTyConKey
1121 isWordTy = is_tc wordTyConKey
1122 isBoolTy = is_tc boolTyConKey
1123 isUnitTy = is_tc unitTyConKey
1124 isCharTy = is_tc charTyConKey
1126 isStringTy :: Type -> Bool
1128 = case tcSplitTyConApp_maybe ty of
1129 Just (tc, [arg_ty]) -> tc == listTyCon && isCharTy arg_ty
1132 is_tc :: Unique -> Type -> Bool
1133 -- Newtypes are opaque to this
1134 is_tc uniq ty = case tcSplitTyConApp_maybe ty of
1135 Just (tc, _) -> uniq == getUnique tc
1140 -- NB: Currently used in places where we have already expanded type synonyms;
1141 -- hence no 'coreView'. This could, however, be changed without breaking
1143 isSynFamilyTyConApp :: TcTauType -> Bool
1144 isSynFamilyTyConApp (TyConApp tc tys) = isSynFamilyTyCon tc &&
1145 length tys == tyConArity tc
1146 isSynFamilyTyConApp _other = False
1150 %************************************************************************
1154 %************************************************************************
1157 deNoteType :: Type -> Type
1158 -- Remove all *outermost* type synonyms and other notes
1159 deNoteType ty | Just ty' <- tcView ty = deNoteType ty'
1164 tcTyVarsOfType :: Type -> TcTyVarSet
1165 -- Just the *TcTyVars* free in the type
1166 -- (Types.tyVarsOfTypes finds all free TyVars)
1167 tcTyVarsOfType (TyVarTy tv) = if isTcTyVar tv then unitVarSet tv
1169 tcTyVarsOfType (TyConApp _ tys) = tcTyVarsOfTypes tys
1170 tcTyVarsOfType (PredTy sty) = tcTyVarsOfPred sty
1171 tcTyVarsOfType (FunTy arg res) = tcTyVarsOfType arg `unionVarSet` tcTyVarsOfType res
1172 tcTyVarsOfType (AppTy fun arg) = tcTyVarsOfType fun `unionVarSet` tcTyVarsOfType arg
1173 tcTyVarsOfType (ForAllTy tyvar ty) = (tcTyVarsOfType ty `delVarSet` tyvar)
1174 `unionVarSet` tcTyVarsOfTyVar tyvar
1175 -- We do sometimes quantify over skolem TcTyVars
1177 tcTyVarsOfTyVar :: TcTyVar -> TyVarSet
1178 tcTyVarsOfTyVar tv | isCoVar tv = tcTyVarsOfType (tyVarKind tv)
1179 | otherwise = emptyVarSet
1181 tcTyVarsOfTypes :: [Type] -> TyVarSet
1182 tcTyVarsOfTypes tys = foldr (unionVarSet.tcTyVarsOfType) emptyVarSet tys
1184 tcTyVarsOfPred :: PredType -> TyVarSet
1185 tcTyVarsOfPred (IParam _ ty) = tcTyVarsOfType ty
1186 tcTyVarsOfPred (ClassP _ tys) = tcTyVarsOfTypes tys
1187 tcTyVarsOfPred (EqPred ty1 ty2) = tcTyVarsOfType ty1 `unionVarSet` tcTyVarsOfType ty2
1190 Note [Silly type synonym]
1191 ~~~~~~~~~~~~~~~~~~~~~~~~~
1194 What are the free tyvars of (T x)? Empty, of course!
1195 Here's the example that Ralf Laemmel showed me:
1196 foo :: (forall a. C u a -> C u a) -> u
1197 mappend :: Monoid u => u -> u -> u
1199 bar :: Monoid u => u
1200 bar = foo (\t -> t `mappend` t)
1201 We have to generalise at the arg to f, and we don't
1202 want to capture the constraint (Monad (C u a)) because
1203 it appears to mention a. Pretty silly, but it was useful to him.
1205 exactTyVarsOfType is used by the type checker to figure out exactly
1206 which type variables are mentioned in a type. It's also used in the
1207 smart-app checking code --- see TcExpr.tcIdApp
1209 On the other hand, consider a *top-level* definition
1210 f = (\x -> x) :: T a -> T a
1211 If we don't abstract over 'a' it'll get fixed to GHC.Prim.Any, and then
1212 if we have an application like (f "x") we get a confusing error message
1213 involving Any. So the conclusion is this: when generalising
1214 - at top level use tyVarsOfType
1215 - in nested bindings use exactTyVarsOfType
1216 See Trac #1813 for example.
1219 exactTyVarsOfType :: TcType -> TyVarSet
1220 -- Find the free type variables (of any kind)
1221 -- but *expand* type synonyms. See Note [Silly type synonym] above.
1222 exactTyVarsOfType ty
1225 go ty | Just ty' <- tcView ty = go ty' -- This is the key line
1226 go (TyVarTy tv) = unitVarSet tv
1227 go (TyConApp _ tys) = exactTyVarsOfTypes tys
1228 go (PredTy ty) = go_pred ty
1229 go (FunTy arg res) = go arg `unionVarSet` go res
1230 go (AppTy fun arg) = go fun `unionVarSet` go arg
1231 go (ForAllTy tyvar ty) = delVarSet (go ty) tyvar
1232 `unionVarSet` go_tv tyvar
1234 go_pred (IParam _ ty) = go ty
1235 go_pred (ClassP _ tys) = exactTyVarsOfTypes tys
1236 go_pred (EqPred ty1 ty2) = go ty1 `unionVarSet` go ty2
1238 go_tv tyvar | isCoVar tyvar = go (tyVarKind tyvar)
1239 | otherwise = emptyVarSet
1241 exactTyVarsOfTypes :: [TcType] -> TyVarSet
1242 exactTyVarsOfTypes tys = foldr (unionVarSet . exactTyVarsOfType) emptyVarSet tys
1245 Find the free tycons and classes of a type. This is used in the front
1246 end of the compiler.
1249 tyClsNamesOfType :: Type -> NameSet
1250 tyClsNamesOfType (TyVarTy _) = emptyNameSet
1251 tyClsNamesOfType (TyConApp tycon tys) = unitNameSet (getName tycon) `unionNameSets` tyClsNamesOfTypes tys
1252 tyClsNamesOfType (PredTy (IParam _ ty)) = tyClsNamesOfType ty
1253 tyClsNamesOfType (PredTy (ClassP cl tys)) = unitNameSet (getName cl) `unionNameSets` tyClsNamesOfTypes tys
1254 tyClsNamesOfType (PredTy (EqPred ty1 ty2)) = tyClsNamesOfType ty1 `unionNameSets` tyClsNamesOfType ty2
1255 tyClsNamesOfType (FunTy arg res) = tyClsNamesOfType arg `unionNameSets` tyClsNamesOfType res
1256 tyClsNamesOfType (AppTy fun arg) = tyClsNamesOfType fun `unionNameSets` tyClsNamesOfType arg
1257 tyClsNamesOfType (ForAllTy _ ty) = tyClsNamesOfType ty
1259 tyClsNamesOfTypes :: [Type] -> NameSet
1260 tyClsNamesOfTypes tys = foldr (unionNameSets . tyClsNamesOfType) emptyNameSet tys
1262 tyClsNamesOfDFunHead :: Type -> NameSet
1263 -- Find the free type constructors and classes
1264 -- of the head of the dfun instance type
1265 -- The 'dfun_head_type' is because of
1266 -- instance Foo a => Baz T where ...
1267 -- The decl is an orphan if Baz and T are both not locally defined,
1268 -- even if Foo *is* locally defined
1269 tyClsNamesOfDFunHead dfun_ty
1270 = case tcSplitSigmaTy dfun_ty of
1271 (_, _, head_ty) -> tyClsNamesOfType head_ty
1275 %************************************************************************
1277 \subsection[TysWiredIn-ext-type]{External types}
1279 %************************************************************************
1281 The compiler's foreign function interface supports the passing of a
1282 restricted set of types as arguments and results (the restricting factor
1286 tcSplitIOType_maybe :: Type -> Maybe (TyCon, Type, CoercionI)
1287 -- (isIOType t) returns Just (IO,t',co)
1288 -- if co : t ~ IO t'
1289 -- returns Nothing otherwise
1290 tcSplitIOType_maybe ty
1291 = case tcSplitTyConApp_maybe ty of
1292 -- This split absolutely has to be a tcSplit, because we must
1293 -- see the IO type; and it's a newtype which is transparent to splitTyConApp.
1295 Just (io_tycon, [io_res_ty])
1296 | io_tycon `hasKey` ioTyConKey
1297 -> Just (io_tycon, io_res_ty, IdCo ty)
1300 | not (isRecursiveTyCon tc)
1301 , Just (ty, co1) <- instNewTyCon_maybe tc tys
1302 -- Newtypes that require a coercion are ok
1303 -> case tcSplitIOType_maybe ty of
1305 Just (tc, ty', co2) -> Just (tc, ty', co1 `mkTransCoI` co2)
1309 isFFITy :: Type -> Bool
1310 -- True for any TyCon that can possibly be an arg or result of an FFI call
1311 isFFITy ty = checkRepTyCon legalFFITyCon ty
1313 isFFIArgumentTy :: DynFlags -> Safety -> Type -> Bool
1314 -- Checks for valid argument type for a 'foreign import'
1315 isFFIArgumentTy dflags safety ty
1316 = checkRepTyCon (legalOutgoingTyCon dflags safety) ty
1318 isFFIExternalTy :: Type -> Bool
1319 -- Types that are allowed as arguments of a 'foreign export'
1320 isFFIExternalTy ty = checkRepTyCon legalFEArgTyCon ty
1322 isFFIImportResultTy :: DynFlags -> Type -> Bool
1323 isFFIImportResultTy dflags ty
1324 = checkRepTyCon (legalFIResultTyCon dflags) ty
1326 isFFIExportResultTy :: Type -> Bool
1327 isFFIExportResultTy ty = checkRepTyCon legalFEResultTyCon ty
1329 isFFIDynArgumentTy :: Type -> Bool
1330 -- The argument type of a foreign import dynamic must be Ptr, FunPtr, Addr,
1331 -- or a newtype of either.
1332 isFFIDynArgumentTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1334 isFFIDynResultTy :: Type -> Bool
1335 -- The result type of a foreign export dynamic must be Ptr, FunPtr, Addr,
1336 -- or a newtype of either.
1337 isFFIDynResultTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1339 isFFILabelTy :: Type -> Bool
1340 -- The type of a foreign label must be Ptr, FunPtr, Addr,
1341 -- or a newtype of either.
1342 isFFILabelTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1344 isFFIPrimArgumentTy :: DynFlags -> Type -> Bool
1345 -- Checks for valid argument type for a 'foreign import prim'
1346 -- Currently they must all be simple unlifted types.
1347 isFFIPrimArgumentTy dflags ty
1348 = checkRepTyCon (legalFIPrimArgTyCon dflags) ty
1350 isFFIPrimResultTy :: DynFlags -> Type -> Bool
1351 -- Checks for valid result type for a 'foreign import prim'
1352 -- Currently it must be an unlifted type, including unboxed tuples.
1353 isFFIPrimResultTy dflags ty
1354 = checkRepTyCon (legalFIPrimResultTyCon dflags) ty
1356 isFFIDotnetTy :: DynFlags -> Type -> Bool
1357 isFFIDotnetTy dflags ty
1358 = checkRepTyCon (\ tc -> (legalFIResultTyCon dflags tc ||
1359 isFFIDotnetObjTy ty || isStringTy ty)) ty
1360 -- NB: isStringTy used to look through newtypes, but
1361 -- it no longer does so. May need to adjust isFFIDotNetTy
1362 -- if we do want to look through newtypes.
1364 isFFIDotnetObjTy :: Type -> Bool
1366 = checkRepTyCon check_tc t_ty
1368 (_, t_ty) = tcSplitForAllTys ty
1369 check_tc tc = getName tc == objectTyConName
1371 isFunPtrTy :: Type -> Bool
1372 isFunPtrTy = checkRepTyConKey [funPtrTyConKey]
1374 checkRepTyCon :: (TyCon -> Bool) -> Type -> Bool
1375 -- Look through newtypes, but *not* foralls
1376 -- Should work even for recursive newtypes
1377 -- eg Manuel had: newtype T = MkT (Ptr T)
1378 checkRepTyCon check_tc ty
1382 | Just (tc,tys) <- splitTyConApp_maybe ty
1383 = case carefullySplitNewType_maybe rec_nts tc tys of
1384 Just (rec_nts', ty') -> go rec_nts' ty'
1385 Nothing -> check_tc tc
1389 checkRepTyConKey :: [Unique] -> Type -> Bool
1390 -- Like checkRepTyCon, but just looks at the TyCon key
1391 checkRepTyConKey keys
1392 = checkRepTyCon (\tc -> tyConUnique tc `elem` keys)
1395 ----------------------------------------------
1396 These chaps do the work; they are not exported
1397 ----------------------------------------------
1400 legalFEArgTyCon :: TyCon -> Bool
1402 -- It's illegal to make foreign exports that take unboxed
1403 -- arguments. The RTS API currently can't invoke such things. --SDM 7/2000
1404 = boxedMarshalableTyCon tc
1406 legalFIResultTyCon :: DynFlags -> TyCon -> Bool
1407 legalFIResultTyCon dflags tc
1408 | tc == unitTyCon = True
1409 | otherwise = marshalableTyCon dflags tc
1411 legalFEResultTyCon :: TyCon -> Bool
1412 legalFEResultTyCon tc
1413 | tc == unitTyCon = True
1414 | otherwise = boxedMarshalableTyCon tc
1416 legalOutgoingTyCon :: DynFlags -> Safety -> TyCon -> Bool
1417 -- Checks validity of types going from Haskell -> external world
1418 legalOutgoingTyCon dflags _ tc
1419 = marshalableTyCon dflags tc
1421 legalFFITyCon :: TyCon -> Bool
1422 -- True for any TyCon that can possibly be an arg or result of an FFI call
1424 = isUnLiftedTyCon tc || boxedMarshalableTyCon tc || tc == unitTyCon
1426 marshalableTyCon :: DynFlags -> TyCon -> Bool
1427 marshalableTyCon dflags tc
1428 = (xopt Opt_UnliftedFFITypes dflags
1429 && isUnLiftedTyCon tc
1430 && not (isUnboxedTupleTyCon tc)
1431 && case tyConPrimRep tc of -- Note [Marshalling VoidRep]
1434 || boxedMarshalableTyCon tc
1436 boxedMarshalableTyCon :: TyCon -> Bool
1437 boxedMarshalableTyCon tc
1438 = getUnique tc `elem` [ intTyConKey, int8TyConKey, int16TyConKey
1439 , int32TyConKey, int64TyConKey
1440 , wordTyConKey, word8TyConKey, word16TyConKey
1441 , word32TyConKey, word64TyConKey
1442 , floatTyConKey, doubleTyConKey
1443 , ptrTyConKey, funPtrTyConKey
1449 legalFIPrimArgTyCon :: DynFlags -> TyCon -> Bool
1450 -- Check args of 'foreign import prim', only allow simple unlifted types.
1451 -- Strictly speaking it is unnecessary to ban unboxed tuples here since
1452 -- currently they're of the wrong kind to use in function args anyway.
1453 legalFIPrimArgTyCon dflags tc
1454 = xopt Opt_UnliftedFFITypes dflags
1455 && isUnLiftedTyCon tc
1456 && not (isUnboxedTupleTyCon tc)
1458 legalFIPrimResultTyCon :: DynFlags -> TyCon -> Bool
1459 -- Check result type of 'foreign import prim'. Allow simple unlifted
1460 -- types and also unboxed tuple result types '... -> (# , , #)'
1461 legalFIPrimResultTyCon dflags tc
1462 = xopt Opt_UnliftedFFITypes dflags
1463 && isUnLiftedTyCon tc
1464 && (isUnboxedTupleTyCon tc
1465 || case tyConPrimRep tc of -- Note [Marshalling VoidRep]
1470 Note [Marshalling VoidRep]
1471 ~~~~~~~~~~~~~~~~~~~~~~~~~~
1472 We don't treat State# (whose PrimRep is VoidRep) as marshalable.
1473 In turn that means you can't write
1474 foreign import foo :: Int -> State# RealWorld
1476 Reason: the back end falls over with panic "primRepHint:VoidRep";
1477 and there is no compelling reason to permit it