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, mkTopTvSubst, notElemTvSubst,
127 getTvSubstEnv, setTvSubstEnv, getTvInScope, extendTvInScope, lookupTyVar,
128 extendTvSubst, extendTvSubstList, isInScope, mkTvSubst, zipTyEnv,
129 substTy, substTys, substTyWith, substTheta, substTyVar, substTyVars, substTyVarBndr,
131 isUnLiftedType, -- Source types are always lifted
132 isUnboxedTupleType, -- Ditto
135 tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tyVarsOfTheta,
136 tcTyVarsOfType, tcTyVarsOfTypes, tcTyVarsOfPred, exactTyVarsOfType,
139 pprKind, pprParendKind,
140 pprType, pprParendType, pprTypeApp, pprTyThingCategory,
141 pprPred, pprTheta, pprThetaArrow, pprClassPred
145 #include "HsVersions.h"
157 import HsExpr( HsMatchContext )
173 import Data.List( mapAccumL )
177 %************************************************************************
181 %************************************************************************
183 The type checker divides the generic Type world into the
184 following more structured beasts:
186 sigma ::= forall tyvars. phi
187 -- A sigma type is a qualified type
189 -- Note that even if 'tyvars' is empty, theta
190 -- may not be: e.g. (?x::Int) => Int
192 -- Note that 'sigma' is in prenex form:
193 -- all the foralls are at the front.
194 -- A 'phi' type has no foralls to the right of
202 -- A 'tau' type has no quantification anywhere
203 -- Note that the args of a type constructor must be taus
205 | tycon tau_1 .. tau_n
209 -- In all cases, a (saturated) type synonym application is legal,
210 -- provided it expands to the required form.
213 type TcTyVar = TyVar -- Used only during type inference
214 type TcCoVar = CoVar -- Used only during type inference; mutable
215 type TcType = Type -- A TcType can have mutable type variables
216 -- Invariant on ForAllTy in TcTypes:
218 -- a cannot occur inside a MutTyVar in T; that is,
219 -- T is "flattened" before quantifying over a
221 -- These types do not have boxy type variables in them
222 type TcPredType = PredType
223 type TcThetaType = ThetaType
224 type TcSigmaType = TcType
225 type TcRhoType = TcType
226 type TcTauType = TcType
228 type TcTyVarSet = TyVarSet
232 %************************************************************************
234 \subsection{TyVarDetails}
236 %************************************************************************
238 TyVarDetails gives extra info about type variables, used during type
239 checking. It's attached to mutable type variables only.
240 It's knot-tied back to Var.lhs. There is no reason in principle
241 why Var.lhs shouldn't actually have the definition, but it "belongs" here.
244 Note [Signature skolems]
245 ~~~~~~~~~~~~~~~~~~~~~~~~
250 (x,y,z) = ([y,z], z, head x)
252 Here, x and y have type sigs, which go into the environment. We used to
253 instantiate their types with skolem constants, and push those types into
254 the RHS, so we'd typecheck the RHS with type
256 where a*, b* are skolem constants, and c is an ordinary meta type varible.
258 The trouble is that the occurrences of z in the RHS force a* and b* to
259 be the *same*, so we can't make them into skolem constants that don't unify
260 with each other. Alas.
262 One solution would be insist that in the above defn the programmer uses
263 the same type variable in both type signatures. But that takes explanation.
265 The alternative (currently implemented) is to have a special kind of skolem
266 constant, SigTv, which can unify with other SigTvs. These are *not* treated
267 as righd for the purposes of GADTs. And they are used *only* for pattern
268 bindings and mutually recursive function bindings. See the function
269 TcBinds.tcInstSig, and its use_skols parameter.
273 -- A TyVarDetails is inside a TyVar
275 = SkolemTv SkolemInfo -- A skolem constant
278 -- The "skolem" obtained by flattening during
279 -- constraint simplification
281 -- In comments we will use the notation alpha[flat = ty]
282 -- to represent a flattening skolem variable alpha
283 -- identified with type ty.
285 | MetaTv MetaInfo (IORef MetaDetails)
288 = Flexi -- Flexi type variables unify to become Indirects
292 = TauTv -- This MetaTv is an ordinary unification variable
293 -- A TauTv is always filled in with a tau-type, which
294 -- never contains any ForAlls
296 | SigTv Name -- A variant of TauTv, except that it should not be
297 -- unified with a type, only with a type variable
298 -- SigTvs are only distinguished to improve error messages
299 -- see Note [Signature skolems]
300 -- The MetaDetails, if filled in, will
301 -- always be another SigTv or a SkolemTv
302 -- The Name is the name of the function from whose
303 -- type signature we got this skolem
305 ----------------------------------
306 -- SkolemInfo describes a site where
307 -- a) type variables are skolemised
308 -- b) an implication constraint is generated
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 -- An existential type variable bound by a pattern for
319 DataCon -- a data constructor with an existential type.
320 (HsMatchContext Name)
321 -- e.g. data T = forall a. Eq a => MkT a
323 -- The pattern MkT x will allocate an existential type
326 | ArrowSkol -- An arrow form (see TcArrows)
328 | IPSkol [IPName Name] -- Binding site of an implicit parameter
330 | RuleSkol RuleName -- The LHS of a RULE
331 | GenSkol TcType -- Bound when doing a subsumption check for ty
332 | RuntimeUnkSkol -- a type variable used to represent an unknown
333 -- runtime type (used in the GHCi debugger)
335 | NoScSkol -- Used for the "self" superclass when solving
336 -- superclasses; don't generate superclasses of me
338 | UnkSkol -- Unhelpful info (until I improve it)
340 -------------------------------------
341 -- UserTypeCtxt describes the places where a
342 -- programmer-written type signature can occur
343 -- Like SkolemInfo, no location info
345 = FunSigCtxt Name -- Function type signature
346 -- Also used for types in SPECIALISE pragmas
347 | ExprSigCtxt -- Expression type signature
348 | ConArgCtxt Name -- Data constructor argument
349 | TySynCtxt Name -- RHS of a type synonym decl
350 | GenPatCtxt -- Pattern in generic decl
351 -- f{| a+b |} (Inl x) = ...
352 | LamPatSigCtxt -- Type sig in lambda pattern
354 | BindPatSigCtxt -- Type sig in pattern binding pattern
356 | ResSigCtxt -- Result type sig
358 | ForSigCtxt Name -- Foreign inport or export signature
359 | DefaultDeclCtxt -- Types in a default declaration
360 | SpecInstCtxt -- SPECIALISE instance pragma
361 | ThBrackCtxt -- Template Haskell type brackets [t| ... |]
363 -- Notes re TySynCtxt
364 -- We allow type synonyms that aren't types; e.g. type List = []
366 -- If the RHS mentions tyvars that aren't in scope, we'll
367 -- quantify over them:
368 -- e.g. type T = a->a
369 -- will become type T = forall a. a->a
371 -- With gla-exts that's right, but for H98 we should complain.
373 ---------------------------------
376 mkKindName :: Unique -> Name
377 mkKindName unique = mkSystemName unique kind_var_occ
379 kindVarRef :: KindVar -> IORef MetaDetails
381 ASSERT ( isTcTyVar tc )
382 case tcTyVarDetails tc of
383 MetaTv TauTv ref -> ref
384 _ -> pprPanic "kindVarRef" (ppr tc)
386 mkKindVar :: Unique -> IORef MetaDetails -> KindVar
388 = mkTcTyVar (mkKindName u)
389 tySuperKind -- not sure this is right,
390 -- do we need kind vars for
394 kind_var_occ :: OccName -- Just one for all KindVars
395 -- They may be jiggled by tidying
396 kind_var_occ = mkOccName tvName "k"
399 %************************************************************************
403 %************************************************************************
406 pprTcTyVarDetails :: TcTyVarDetails -> SDoc
408 pprTcTyVarDetails (SkolemTv _) = ptext (sLit "sk")
409 pprTcTyVarDetails (FlatSkol {}) = ptext (sLit "fsk")
410 pprTcTyVarDetails (MetaTv TauTv _) = ptext (sLit "tau")
411 pprTcTyVarDetails (MetaTv (SigTv _) _) = ptext (sLit "sig")
413 pprUserTypeCtxt :: UserTypeCtxt -> SDoc
414 pprUserTypeCtxt (FunSigCtxt n) = ptext (sLit "the type signature for") <+> quotes (ppr n)
415 pprUserTypeCtxt ExprSigCtxt = ptext (sLit "an expression type signature")
416 pprUserTypeCtxt (ConArgCtxt c) = ptext (sLit "the type of the constructor") <+> quotes (ppr c)
417 pprUserTypeCtxt (TySynCtxt c) = ptext (sLit "the RHS of the type synonym") <+> quotes (ppr c)
418 pprUserTypeCtxt GenPatCtxt = ptext (sLit "the type pattern of a generic definition")
419 pprUserTypeCtxt ThBrackCtxt = ptext (sLit "a Template Haskell quotation [t|...|]")
420 pprUserTypeCtxt LamPatSigCtxt = ptext (sLit "a pattern type signature")
421 pprUserTypeCtxt BindPatSigCtxt = ptext (sLit "a pattern type signature")
422 pprUserTypeCtxt ResSigCtxt = ptext (sLit "a result type signature")
423 pprUserTypeCtxt (ForSigCtxt n) = ptext (sLit "the foreign declaration for") <+> quotes (ppr n)
424 pprUserTypeCtxt DefaultDeclCtxt = ptext (sLit "a type in a `default' declaration")
425 pprUserTypeCtxt SpecInstCtxt = ptext (sLit "a SPECIALISE instance pragma")
427 pprSkolTvBinding :: TcTyVar -> SDoc
428 -- Print info about the binding of a skolem tyvar,
429 -- or nothing if we don't have anything useful to say
431 = ASSERT ( isTcTyVar tv )
432 quotes (ppr tv) <+> ppr_details (tcTyVarDetails tv)
434 ppr_details (SkolemTv info) = ppr_skol info
435 ppr_details (FlatSkol {}) = ptext (sLit "is a flattening type variable")
436 ppr_details (MetaTv TauTv _) = ptext (sLit "is a meta type variable")
437 ppr_details (MetaTv (SigTv n) _) = ptext (sLit "is bound by the type signature for") <+> quotes (ppr n)
439 ppr_skol UnkSkol = ptext (sLit "is an unknown type variable") -- Unhelpful
440 ppr_skol RuntimeUnkSkol = ptext (sLit "is an unknown runtime type")
441 ppr_skol info = sep [ptext (sLit "is a rigid type variable bound by"),
442 sep [pprSkolInfo info,
443 nest 2 (ptext (sLit "at") <+> ppr (getSrcLoc tv))]]
445 pprSkolInfo :: SkolemInfo -> SDoc
446 -- Complete the sentence "is a rigid type variable bound by..."
447 pprSkolInfo (SigSkol ctxt) = pprUserTypeCtxt ctxt
448 pprSkolInfo (IPSkol ips) = ptext (sLit "the implicit-parameter bindings for")
449 <+> pprWithCommas ppr ips
450 pprSkolInfo (ClsSkol cls) = ptext (sLit "the class declaration for") <+> quotes (ppr cls)
451 pprSkolInfo InstSkol = ptext (sLit "the instance declaration")
452 pprSkolInfo NoScSkol = ptext (sLit "the instance declaration (self)")
453 pprSkolInfo FamInstSkol = ptext (sLit "the family instance declaration")
454 pprSkolInfo (RuleSkol name) = ptext (sLit "the RULE") <+> doubleQuotes (ftext name)
455 pprSkolInfo ArrowSkol = ptext (sLit "the arrow form")
456 pprSkolInfo (PatSkol dc _) = sep [ ptext (sLit "a pattern with constructor")
457 , ppr dc <+> dcolon <+> ppr (dataConUserType dc) ]
458 pprSkolInfo (GenSkol ty) = sep [ ptext (sLit "the polymorphic type")
462 -- For type variables the others are dealt with by pprSkolTvBinding.
463 -- For Insts, these cases should not happen
464 pprSkolInfo UnkSkol = WARN( True, text "pprSkolInfo: UnkSkol" ) ptext (sLit "UnkSkol")
465 pprSkolInfo RuntimeUnkSkol = WARN( True, text "pprSkolInfo: RuntimeUnkSkol" ) ptext (sLit "RuntimeUnkSkol")
467 instance Outputable MetaDetails where
468 ppr Flexi = ptext (sLit "Flexi")
469 ppr (Indirect ty) = ptext (sLit "Indirect") <+> ppr ty
473 %************************************************************************
475 \subsection{TidyType}
477 %************************************************************************
480 -- | This tidies up a type for printing in an error message, or in
481 -- an interface file.
483 -- It doesn't change the uniques at all, just the print names.
484 tidyTyVarBndr :: TidyEnv -> TyVar -> (TidyEnv, TyVar)
485 tidyTyVarBndr env@(tidy_env, subst) tyvar
486 = case tidyOccName tidy_env (getOccName name) of
487 (tidy', occ') -> ((tidy', subst'), tyvar'')
489 subst' = extendVarEnv subst tyvar tyvar''
490 tyvar' = setTyVarName tyvar name'
491 name' = tidyNameOcc name occ'
492 -- Don't forget to tidy the kind for coercions!
493 tyvar'' | isCoVar tyvar = setTyVarKind tyvar' kind'
495 kind' = tidyType env (tyVarKind tyvar)
497 name = tyVarName tyvar
500 tidyFreeTyVars :: TidyEnv -> TyVarSet -> TidyEnv
501 -- ^ Add the free 'TyVar's to the env in tidy form,
502 -- so that we can tidy the type they are free in
503 tidyFreeTyVars env tyvars = fst (tidyOpenTyVars env (varSetElems tyvars))
506 tidyOpenTyVars :: TidyEnv -> [TyVar] -> (TidyEnv, [TyVar])
507 tidyOpenTyVars env tyvars = mapAccumL tidyOpenTyVar env tyvars
510 tidyOpenTyVar :: TidyEnv -> TyVar -> (TidyEnv, TyVar)
511 -- ^ Treat a new 'TyVar' as a binder, and give it a fresh tidy name
512 -- using the environment if one has not already been allocated. See
513 -- also 'tidyTyVarBndr'
514 tidyOpenTyVar env@(_, subst) tyvar
515 = case lookupVarEnv subst tyvar of
516 Just tyvar' -> (env, tyvar') -- Already substituted
517 Nothing -> tidyTyVarBndr env tyvar -- Treat it as a binder
520 tidyType :: TidyEnv -> Type -> Type
521 tidyType env@(_, subst) ty
524 go (TyVarTy tv) = case lookupVarEnv subst tv of
526 Just tv' -> expand tv'
527 go (TyConApp tycon tys) = let args = map go tys
528 in args `seqList` TyConApp tycon args
529 go (PredTy sty) = PredTy (tidyPred env sty)
530 go (AppTy fun arg) = (AppTy $! (go fun)) $! (go arg)
531 go (FunTy fun arg) = (FunTy $! (go fun)) $! (go arg)
532 go (ForAllTy tv ty) = ForAllTy tvp $! (tidyType envp ty)
534 (envp, tvp) = tidyTyVarBndr env tv
536 -- Expand FlatSkols, the skolems introduced by flattening process
537 -- We don't want to show them in type error messages
538 expand tv | isTcTyVar tv
539 , FlatSkol ty <- tcTyVarDetails tv
545 tidyTypes :: TidyEnv -> [Type] -> [Type]
546 tidyTypes env tys = map (tidyType env) tys
549 tidyPred :: TidyEnv -> PredType -> PredType
550 tidyPred env (IParam n ty) = IParam n (tidyType env ty)
551 tidyPred env (ClassP clas tys) = ClassP clas (tidyTypes env tys)
552 tidyPred env (EqPred ty1 ty2) = EqPred (tidyType env ty1) (tidyType env ty2)
555 -- | Grabs the free type variables, tidies them
556 -- and then uses 'tidyType' to work over the type itself
557 tidyOpenType :: TidyEnv -> Type -> (TidyEnv, Type)
559 = (env', tidyType env' ty)
561 env' = tidyFreeTyVars env (tyVarsOfType ty)
564 tidyOpenTypes :: TidyEnv -> [Type] -> (TidyEnv, [Type])
565 tidyOpenTypes env tys = mapAccumL tidyOpenType env tys
568 -- | Calls 'tidyType' on a top-level type (i.e. with an empty tidying environment)
569 tidyTopType :: Type -> Type
570 tidyTopType ty = tidyType emptyTidyEnv ty
573 tidySkolemTyVar :: TidyEnv -> TcTyVar -> (TidyEnv, TcTyVar)
574 -- Tidy the type inside a GenSkol, preparatory to printing it
575 tidySkolemTyVar env tv
576 = ASSERT( isTcTyVar tv && (isSkolemTyVar tv || isSigTyVar tv ) )
577 (env1, mkTcTyVar (tyVarName tv) (tyVarKind tv) info1)
579 (env1, info1) = case tcTyVarDetails tv of
580 SkolemTv info -> (env1, SkolemTv info')
582 (env1, info') = tidy_skol_info env info
585 tidy_skol_info env (GenSkol ty) = (env1, GenSkol ty1)
587 (env1, ty1) = tidyOpenType env ty
588 tidy_skol_info env info = (env, info)
591 tidyKind :: TidyEnv -> Kind -> (TidyEnv, Kind)
592 tidyKind env k = tidyOpenType env k
596 %************************************************************************
600 %************************************************************************
603 isImmutableTyVar :: TyVar -> Bool
606 | isTcTyVar tv = isSkolemTyVar tv
609 isTyConableTyVar, isSkolemTyVar, isExistentialTyVar,
610 isMetaTyVar :: TcTyVar -> Bool
613 -- True of a meta-type variable that can be filled in
614 -- with a type constructor application; in particular,
616 = ASSERT( isTcTyVar tv)
617 case tcTyVarDetails tv of
618 MetaTv TauTv _ -> True
622 = ASSERT2( isTcTyVar tv, ppr tv )
623 case tcTyVarDetails tv of
628 isExistentialTyVar tv -- Existential type variable, bound by a pattern
629 = ASSERT( isTcTyVar tv )
630 case tcTyVarDetails tv of
631 SkolemTv (PatSkol {}) -> True
635 = ASSERT2( isTcTyVar tv, ppr tv )
636 case tcTyVarDetails tv of
640 isMetaTyVarTy :: TcType -> Bool
641 isMetaTyVarTy (TyVarTy tv) = isMetaTyVar tv
642 isMetaTyVarTy _ = False
644 isSigTyVar :: Var -> Bool
646 = ASSERT( isTcTyVar tv )
647 case tcTyVarDetails tv of
648 MetaTv (SigTv _) _ -> True
651 metaTvRef :: TyVar -> IORef MetaDetails
653 = ASSERT2( isTcTyVar tv, ppr tv )
654 case tcTyVarDetails tv of
656 _ -> pprPanic "metaTvRef" (ppr tv)
658 isFlexi, isIndirect :: MetaDetails -> Bool
662 isIndirect (Indirect _) = True
665 isRuntimeUnk :: TyVar -> Bool
666 isRuntimeUnk x | isTcTyVar x
667 , SkolemTv RuntimeUnkSkol <- tcTyVarDetails x = True
670 isUnk :: TyVar -> Bool
671 isUnk x | isTcTyVar x
672 , SkolemTv UnkSkol <- tcTyVarDetails x = True
677 %************************************************************************
679 \subsection{Tau, sigma and rho}
681 %************************************************************************
684 mkSigmaTy :: [TyVar] -> [PredType] -> Type -> Type
685 mkSigmaTy tyvars theta tau = mkForAllTys tyvars (mkPhiTy theta tau)
687 mkPhiTy :: [PredType] -> Type -> Type
688 mkPhiTy theta ty = foldr (\p r -> mkFunTy (mkPredTy p) r) ty theta
691 @isTauTy@ tests for nested for-alls. It should not be called on a boxy type.
694 isTauTy :: Type -> Bool
695 isTauTy ty | Just ty' <- tcView ty = isTauTy ty'
696 isTauTy (TyVarTy _) = True
697 isTauTy (TyConApp tc tys) = all isTauTy tys && isTauTyCon tc
698 isTauTy (AppTy a b) = isTauTy a && isTauTy b
699 isTauTy (FunTy a b) = isTauTy a && isTauTy b
700 isTauTy (PredTy _) = True -- Don't look through source types
704 isTauTyCon :: TyCon -> Bool
705 -- Returns False for type synonyms whose expansion is a polytype
707 | isClosedSynTyCon tc = isTauTy (snd (synTyConDefn tc))
711 isRigidTy :: TcType -> Bool
712 -- A type is rigid if it has no meta type variables in it
713 isRigidTy ty = all isImmutableTyVar (varSetElems (tcTyVarsOfType ty))
715 isRefineableTy :: TcType -> (Bool,Bool)
716 -- A type should have type refinements applied to it if it has
717 -- free type variables, and they are all rigid
718 isRefineableTy ty = (null tc_tvs, all isImmutableTyVar tc_tvs)
720 tc_tvs = varSetElems (tcTyVarsOfType ty)
722 isRefineablePred :: TcPredType -> Bool
723 isRefineablePred pred = not (null tc_tvs) && all isImmutableTyVar tc_tvs
725 tc_tvs = varSetElems (tcTyVarsOfPred pred)
728 getDFunTyKey :: Type -> OccName -- Get some string from a type, to be used to
729 -- construct a dictionary function name
730 getDFunTyKey ty | Just ty' <- tcView ty = getDFunTyKey ty'
731 getDFunTyKey (TyVarTy tv) = getOccName tv
732 getDFunTyKey (TyConApp tc _) = getOccName tc
733 getDFunTyKey (AppTy fun _) = getDFunTyKey fun
734 getDFunTyKey (FunTy _ _) = getOccName funTyCon
735 getDFunTyKey (ForAllTy _ t) = getDFunTyKey t
736 getDFunTyKey ty = pprPanic "getDFunTyKey" (pprType ty)
737 -- PredTy shouldn't happen
741 %************************************************************************
743 \subsection{Expanding and splitting}
745 %************************************************************************
747 These tcSplit functions are like their non-Tc analogues, but
748 a) they do not look through newtypes
749 b) they do not look through PredTys
751 However, they are non-monadic and do not follow through mutable type
752 variables. It's up to you to make sure this doesn't matter.
755 tcSplitForAllTys :: Type -> ([TyVar], Type)
756 tcSplitForAllTys ty = split ty ty []
758 split orig_ty ty tvs | Just ty' <- tcView ty = split orig_ty ty' tvs
759 split _ (ForAllTy tv ty) tvs
760 | not (isCoVar tv) = split ty ty (tv:tvs)
761 split orig_ty _ tvs = (reverse tvs, orig_ty)
763 tcIsForAllTy :: Type -> Bool
764 tcIsForAllTy ty | Just ty' <- tcView ty = tcIsForAllTy ty'
765 tcIsForAllTy (ForAllTy tv _) = not (isCoVar tv)
766 tcIsForAllTy _ = False
768 tcSplitPredFunTy_maybe :: Type -> Maybe (PredType, Type)
769 -- Split off the first predicate argument from a type
770 tcSplitPredFunTy_maybe ty | Just ty' <- tcView ty = tcSplitPredFunTy_maybe ty'
771 tcSplitPredFunTy_maybe (ForAllTy tv ty)
772 | isCoVar tv = Just (coVarPred tv, ty)
773 tcSplitPredFunTy_maybe (FunTy arg res)
774 | Just p <- tcSplitPredTy_maybe arg = Just (p, res)
775 tcSplitPredFunTy_maybe _
778 tcSplitPhiTy :: Type -> (ThetaType, Type)
783 = case tcSplitPredFunTy_maybe ty of
784 Just (pred, ty) -> split ty (pred:ts)
785 Nothing -> (reverse ts, ty)
787 tcSplitSigmaTy :: Type -> ([TyVar], ThetaType, Type)
788 tcSplitSigmaTy ty = case tcSplitForAllTys ty of
789 (tvs, rho) -> case tcSplitPhiTy rho of
790 (theta, tau) -> (tvs, theta, tau)
792 -----------------------
793 tcDeepSplitSigmaTy_maybe
794 :: TcSigmaType -> Maybe ([TcType], [TyVar], ThetaType, TcSigmaType)
795 -- Looks for a *non-trivial* quantified type, under zero or more function arrows
796 -- By "non-trivial" we mean either tyvars or constraints are non-empty
798 tcDeepSplitSigmaTy_maybe ty
799 | Just (arg_ty, res_ty) <- tcSplitFunTy_maybe ty
800 , Just (arg_tys, tvs, theta, rho) <- tcDeepSplitSigmaTy_maybe res_ty
801 = Just (arg_ty:arg_tys, tvs, theta, rho)
803 | (tvs, theta, rho) <- tcSplitSigmaTy ty
804 , not (null tvs && null theta)
805 = Just ([], tvs, theta, rho)
807 | otherwise = Nothing
809 -----------------------
810 tcTyConAppTyCon :: Type -> TyCon
811 tcTyConAppTyCon ty = case tcSplitTyConApp_maybe ty of
813 Nothing -> pprPanic "tcTyConAppTyCon" (pprType ty)
815 tcTyConAppArgs :: Type -> [Type]
816 tcTyConAppArgs ty = case tcSplitTyConApp_maybe ty of
817 Just (_, args) -> args
818 Nothing -> pprPanic "tcTyConAppArgs" (pprType ty)
820 tcSplitTyConApp :: Type -> (TyCon, [Type])
821 tcSplitTyConApp ty = case tcSplitTyConApp_maybe ty of
823 Nothing -> pprPanic "tcSplitTyConApp" (pprType ty)
825 tcSplitTyConApp_maybe :: Type -> Maybe (TyCon, [Type])
826 tcSplitTyConApp_maybe ty | Just ty' <- tcView ty = tcSplitTyConApp_maybe ty'
827 tcSplitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
828 tcSplitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res])
829 -- Newtypes are opaque, so they may be split
830 -- However, predicates are not treated
831 -- as tycon applications by the type checker
832 tcSplitTyConApp_maybe _ = Nothing
834 -----------------------
835 tcSplitFunTys :: Type -> ([Type], Type)
836 tcSplitFunTys ty = case tcSplitFunTy_maybe ty of
838 Just (arg,res) -> (arg:args, res')
840 (args,res') = tcSplitFunTys res
842 tcSplitFunTy_maybe :: Type -> Maybe (Type, Type)
843 tcSplitFunTy_maybe ty | Just ty' <- tcView ty = tcSplitFunTy_maybe ty'
844 tcSplitFunTy_maybe (FunTy arg res) | not (isPredTy arg) = Just (arg, res)
845 tcSplitFunTy_maybe _ = Nothing
846 -- Note the (not (isPredTy arg)) guard
847 -- Consider (?x::Int) => Bool
848 -- We don't want to treat this as a function type!
849 -- A concrete example is test tc230:
850 -- f :: () -> (?p :: ()) => () -> ()
856 -> Arity -- N: Number of desired args
857 -> ([TcSigmaType], -- Arg types (N or fewer)
858 TcSigmaType) -- The rest of the type
860 tcSplitFunTysN ty n_args
863 | Just (arg,res) <- tcSplitFunTy_maybe ty
864 = case tcSplitFunTysN res (n_args - 1) of
865 (args, res) -> (arg:args, res)
869 tcSplitFunTy :: Type -> (Type, Type)
870 tcSplitFunTy ty = expectJust "tcSplitFunTy" (tcSplitFunTy_maybe ty)
872 tcFunArgTy :: Type -> Type
873 tcFunArgTy ty = fst (tcSplitFunTy ty)
875 tcFunResultTy :: Type -> Type
876 tcFunResultTy ty = snd (tcSplitFunTy ty)
878 -----------------------
879 tcSplitAppTy_maybe :: Type -> Maybe (Type, Type)
880 tcSplitAppTy_maybe ty | Just ty' <- tcView ty = tcSplitAppTy_maybe ty'
881 tcSplitAppTy_maybe ty = repSplitAppTy_maybe ty
883 tcSplitAppTy :: Type -> (Type, Type)
884 tcSplitAppTy ty = case tcSplitAppTy_maybe ty of
886 Nothing -> pprPanic "tcSplitAppTy" (pprType ty)
888 tcSplitAppTys :: Type -> (Type, [Type])
892 go ty args = case tcSplitAppTy_maybe ty of
893 Just (ty', arg) -> go ty' (arg:args)
896 -----------------------
897 tcGetTyVar_maybe :: Type -> Maybe TyVar
898 tcGetTyVar_maybe ty | Just ty' <- tcView ty = tcGetTyVar_maybe ty'
899 tcGetTyVar_maybe (TyVarTy tv) = Just tv
900 tcGetTyVar_maybe _ = Nothing
902 tcGetTyVar :: String -> Type -> TyVar
903 tcGetTyVar msg ty = expectJust msg (tcGetTyVar_maybe ty)
905 tcIsTyVarTy :: Type -> Bool
906 tcIsTyVarTy ty = maybeToBool (tcGetTyVar_maybe ty)
908 -----------------------
909 tcSplitDFunTy :: Type -> ([TyVar], Class, [Type])
910 -- Split the type of a dictionary function
911 -- We don't use tcSplitSigmaTy, because a DFun may (with NDP)
912 -- have non-Pred arguments, such as
913 -- df :: forall m. (forall b. Eq b => Eq (m b)) -> C m
915 = case tcSplitForAllTys ty of { (tvs, rho) ->
916 case tcSplitDFunHead (drop_pred_tys rho) of { (clas, tys) ->
919 -- Discard the context of the dfun. This can be a mix of
920 -- coercion and class constraints; or (in the general NDP case)
921 -- some other function argument
922 drop_pred_tys ty | Just ty' <- tcView ty = drop_pred_tys ty'
923 drop_pred_tys (ForAllTy tv ty) = ASSERT( isCoVar tv ) drop_pred_tys ty
924 drop_pred_tys (FunTy _ ty) = drop_pred_tys ty
925 drop_pred_tys ty = ty
927 tcSplitDFunHead :: Type -> (Class, [Type])
929 = case tcSplitPredTy_maybe tau of
930 Just (ClassP clas tys) -> (clas, tys)
931 _ -> pprPanic "tcSplitDFunHead" (ppr tau)
933 tcInstHeadTyNotSynonym :: Type -> Bool
934 -- Used in Haskell-98 mode, for the argument types of an instance head
935 -- These must not be type synonyms, but everywhere else type synonyms
936 -- are transparent, so we need a special function here
937 tcInstHeadTyNotSynonym ty
939 TyConApp tc _ -> not (isSynTyCon tc)
942 tcInstHeadTyAppAllTyVars :: Type -> Bool
943 -- Used in Haskell-98 mode, for the argument types of an instance head
944 -- These must be a constructor applied to type variable arguments
945 tcInstHeadTyAppAllTyVars ty
947 TyConApp _ tys -> ok tys
948 FunTy arg res -> ok [arg, res]
951 -- Check that all the types are type variables,
952 -- and that each is distinct
953 ok tys = equalLength tvs tys && hasNoDups tvs
955 tvs = mapCatMaybes get_tv tys
957 get_tv (TyVarTy tv) = Just tv -- through synonyms
963 %************************************************************************
965 \subsection{Predicate types}
967 %************************************************************************
970 evVarPred :: EvVar -> PredType
972 = case tcSplitPredTy_maybe (varType var) of
974 Nothing -> pprPanic "evVarPred" (ppr var <+> ppr (varType var))
976 tcSplitPredTy_maybe :: Type -> Maybe PredType
977 -- Returns Just for predicates only
978 tcSplitPredTy_maybe ty | Just ty' <- tcView ty = tcSplitPredTy_maybe ty'
979 tcSplitPredTy_maybe (PredTy p) = Just p
980 tcSplitPredTy_maybe _ = Nothing
982 predTyUnique :: PredType -> Unique
983 predTyUnique (IParam n _) = getUnique (ipNameName n)
984 predTyUnique (ClassP clas _) = getUnique clas
985 predTyUnique (EqPred a b) = pprPanic "predTyUnique" (ppr (EqPred a b))
989 --------------------- Dictionary types ---------------------------------
992 mkClassPred :: Class -> [Type] -> PredType
993 mkClassPred clas tys = ClassP clas tys
995 isClassPred :: PredType -> Bool
996 isClassPred (ClassP _ _) = True
997 isClassPred _ = False
999 isTyVarClassPred :: PredType -> Bool
1000 isTyVarClassPred (ClassP _ tys) = all tcIsTyVarTy tys
1001 isTyVarClassPred _ = False
1003 getClassPredTys_maybe :: PredType -> Maybe (Class, [Type])
1004 getClassPredTys_maybe (ClassP clas tys) = Just (clas, tys)
1005 getClassPredTys_maybe _ = Nothing
1007 getClassPredTys :: PredType -> (Class, [Type])
1008 getClassPredTys (ClassP clas tys) = (clas, tys)
1009 getClassPredTys _ = panic "getClassPredTys"
1011 mkDictTy :: Class -> [Type] -> Type
1012 mkDictTy clas tys = mkPredTy (ClassP clas tys)
1016 isDictLikeTy :: Type -> Bool
1017 -- Note [Dictionary-like types]
1018 isDictLikeTy ty | Just ty' <- tcView ty = isDictTy ty'
1019 isDictLikeTy (PredTy p) = isClassPred p
1020 isDictLikeTy (TyConApp tc tys)
1021 | isTupleTyCon tc = all isDictLikeTy tys
1022 isDictLikeTy _ = False
1025 Note [Dictionary-like types]
1026 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1027 Being "dictionary-like" means either a dictionary type or a tuple thereof.
1028 In GHC 6.10 we build implication constraints which construct such tuples,
1029 and if we land up with a binding
1030 t :: (C [a], Eq [a])
1032 then we want to treat t as cheap under "-fdicts-cheap" for example.
1033 (Implication constraints are normally inlined, but sadly not if the
1034 occurrence is itself inside an INLINE function! Until we revise the
1035 handling of implication constraints, that is.) This turned out to
1036 be important in getting good arities in DPH code. Example:
1039 class D a where { foo :: a -> a }
1040 instance C a => D (Maybe a) where { foo x = x }
1042 bar :: (C a, C b) => a -> b -> (Maybe a, Maybe b)
1044 bar x y = (foo (Just x), foo (Just y))
1046 Then 'bar' should jolly well have arity 4 (two dicts, two args), but
1047 we ended up with something like
1048 bar = __inline_me__ (\d1,d2. let t :: (D (Maybe a), D (Maybe b)) = ...
1051 This is all a bit ad-hoc; eg it relies on knowing that implication
1052 constraints build tuples.
1054 --------------------- Implicit parameters ---------------------------------
1057 mkIPPred :: IPName Name -> Type -> PredType
1058 mkIPPred ip ty = IParam ip ty
1060 isIPPred :: PredType -> Bool
1061 isIPPred (IParam _ _) = True
1065 --------------------- Equality predicates ---------------------------------
1067 substEqSpec :: TvSubst -> [(TyVar,Type)] -> [(TcType,TcType)]
1068 substEqSpec subst eq_spec = [ (substTyVar subst tv, substTy subst ty)
1069 | (tv,ty) <- eq_spec]
1073 %************************************************************************
1075 \subsection{Predicates}
1077 %************************************************************************
1079 isSigmaTy returns true of any qualified type. It doesn't *necessarily* have
1081 f :: (?x::Int) => Int -> Int
1084 isSigmaTy :: Type -> Bool
1085 isSigmaTy ty | Just ty' <- tcView ty = isSigmaTy ty'
1086 isSigmaTy (ForAllTy _ _) = True
1087 isSigmaTy (FunTy a _) = isPredTy a
1090 isOverloadedTy :: Type -> Bool
1091 -- Yes for a type of a function that might require evidence-passing
1092 -- Used only by bindLocalMethods
1093 -- NB: be sure to check for type with an equality predicate; hence isCoVar
1094 isOverloadedTy ty | Just ty' <- tcView ty = isOverloadedTy ty'
1095 isOverloadedTy (ForAllTy tv ty) = isCoVar tv || isOverloadedTy ty
1096 isOverloadedTy (FunTy a _) = isPredTy a
1097 isOverloadedTy _ = False
1099 isPredTy :: Type -> Bool -- Belongs in TcType because it does
1100 -- not look through newtypes, or predtypes (of course)
1101 isPredTy ty | Just ty' <- tcView ty = isPredTy ty'
1102 isPredTy (PredTy _) = True
1107 isFloatTy, isDoubleTy, isIntegerTy, isIntTy, isWordTy, isBoolTy,
1108 isUnitTy, isCharTy :: Type -> Bool
1109 isFloatTy = is_tc floatTyConKey
1110 isDoubleTy = is_tc doubleTyConKey
1111 isIntegerTy = is_tc integerTyConKey
1112 isIntTy = is_tc intTyConKey
1113 isWordTy = is_tc wordTyConKey
1114 isBoolTy = is_tc boolTyConKey
1115 isUnitTy = is_tc unitTyConKey
1116 isCharTy = is_tc charTyConKey
1118 isStringTy :: Type -> Bool
1120 = case tcSplitTyConApp_maybe ty of
1121 Just (tc, [arg_ty]) -> tc == listTyCon && isCharTy arg_ty
1124 is_tc :: Unique -> Type -> Bool
1125 -- Newtypes are opaque to this
1126 is_tc uniq ty = case tcSplitTyConApp_maybe ty of
1127 Just (tc, _) -> uniq == getUnique tc
1132 -- NB: Currently used in places where we have already expanded type synonyms;
1133 -- hence no 'coreView'. This could, however, be changed without breaking
1135 isSynFamilyTyConApp :: TcTauType -> Bool
1136 isSynFamilyTyConApp (TyConApp tc tys) = isSynFamilyTyCon tc &&
1137 length tys == tyConArity tc
1138 isSynFamilyTyConApp _other = False
1142 %************************************************************************
1146 %************************************************************************
1149 deNoteType :: Type -> Type
1150 -- Remove all *outermost* type synonyms and other notes
1151 deNoteType ty | Just ty' <- tcView ty = deNoteType ty'
1156 tcTyVarsOfType :: Type -> TcTyVarSet
1157 -- Just the *TcTyVars* free in the type
1158 -- (Types.tyVarsOfTypes finds all free TyVars)
1159 tcTyVarsOfType (TyVarTy tv) = if isTcTyVar tv then unitVarSet tv
1161 tcTyVarsOfType (TyConApp _ tys) = tcTyVarsOfTypes tys
1162 tcTyVarsOfType (PredTy sty) = tcTyVarsOfPred sty
1163 tcTyVarsOfType (FunTy arg res) = tcTyVarsOfType arg `unionVarSet` tcTyVarsOfType res
1164 tcTyVarsOfType (AppTy fun arg) = tcTyVarsOfType fun `unionVarSet` tcTyVarsOfType arg
1165 tcTyVarsOfType (ForAllTy tyvar ty) = (tcTyVarsOfType ty `delVarSet` tyvar)
1166 `unionVarSet` tcTyVarsOfTyVar tyvar
1167 -- We do sometimes quantify over skolem TcTyVars
1169 tcTyVarsOfTyVar :: TcTyVar -> TyVarSet
1170 tcTyVarsOfTyVar tv | isCoVar tv = tcTyVarsOfType (tyVarKind tv)
1171 | otherwise = emptyVarSet
1173 tcTyVarsOfTypes :: [Type] -> TyVarSet
1174 tcTyVarsOfTypes tys = foldr (unionVarSet.tcTyVarsOfType) emptyVarSet tys
1176 tcTyVarsOfPred :: PredType -> TyVarSet
1177 tcTyVarsOfPred (IParam _ ty) = tcTyVarsOfType ty
1178 tcTyVarsOfPred (ClassP _ tys) = tcTyVarsOfTypes tys
1179 tcTyVarsOfPred (EqPred ty1 ty2) = tcTyVarsOfType ty1 `unionVarSet` tcTyVarsOfType ty2
1182 Note [Silly type synonym]
1183 ~~~~~~~~~~~~~~~~~~~~~~~~~
1186 What are the free tyvars of (T x)? Empty, of course!
1187 Here's the example that Ralf Laemmel showed me:
1188 foo :: (forall a. C u a -> C u a) -> u
1189 mappend :: Monoid u => u -> u -> u
1191 bar :: Monoid u => u
1192 bar = foo (\t -> t `mappend` t)
1193 We have to generalise at the arg to f, and we don't
1194 want to capture the constraint (Monad (C u a)) because
1195 it appears to mention a. Pretty silly, but it was useful to him.
1197 exactTyVarsOfType is used by the type checker to figure out exactly
1198 which type variables are mentioned in a type. It's also used in the
1199 smart-app checking code --- see TcExpr.tcIdApp
1201 On the other hand, consider a *top-level* definition
1202 f = (\x -> x) :: T a -> T a
1203 If we don't abstract over 'a' it'll get fixed to GHC.Prim.Any, and then
1204 if we have an application like (f "x") we get a confusing error message
1205 involving Any. So the conclusion is this: when generalising
1206 - at top level use tyVarsOfType
1207 - in nested bindings use exactTyVarsOfType
1208 See Trac #1813 for example.
1211 exactTyVarsOfType :: TcType -> TyVarSet
1212 -- Find the free type variables (of any kind)
1213 -- but *expand* type synonyms. See Note [Silly type synonym] above.
1214 exactTyVarsOfType ty
1217 go ty | Just ty' <- tcView ty = go ty' -- This is the key line
1218 go (TyVarTy tv) = unitVarSet tv
1219 go (TyConApp _ tys) = exactTyVarsOfTypes tys
1220 go (PredTy ty) = go_pred ty
1221 go (FunTy arg res) = go arg `unionVarSet` go res
1222 go (AppTy fun arg) = go fun `unionVarSet` go arg
1223 go (ForAllTy tyvar ty) = delVarSet (go ty) tyvar
1224 `unionVarSet` go_tv tyvar
1226 go_pred (IParam _ ty) = go ty
1227 go_pred (ClassP _ tys) = exactTyVarsOfTypes tys
1228 go_pred (EqPred ty1 ty2) = go ty1 `unionVarSet` go ty2
1230 go_tv tyvar | isCoVar tyvar = go (tyVarKind tyvar)
1231 | otherwise = emptyVarSet
1233 exactTyVarsOfTypes :: [TcType] -> TyVarSet
1234 exactTyVarsOfTypes tys = foldr (unionVarSet . exactTyVarsOfType) emptyVarSet tys
1237 Find the free tycons and classes of a type. This is used in the front
1238 end of the compiler.
1241 tyClsNamesOfType :: Type -> NameSet
1242 tyClsNamesOfType (TyVarTy _) = emptyNameSet
1243 tyClsNamesOfType (TyConApp tycon tys) = unitNameSet (getName tycon) `unionNameSets` tyClsNamesOfTypes tys
1244 tyClsNamesOfType (PredTy (IParam _ ty)) = tyClsNamesOfType ty
1245 tyClsNamesOfType (PredTy (ClassP cl tys)) = unitNameSet (getName cl) `unionNameSets` tyClsNamesOfTypes tys
1246 tyClsNamesOfType (PredTy (EqPred ty1 ty2)) = tyClsNamesOfType ty1 `unionNameSets` tyClsNamesOfType ty2
1247 tyClsNamesOfType (FunTy arg res) = tyClsNamesOfType arg `unionNameSets` tyClsNamesOfType res
1248 tyClsNamesOfType (AppTy fun arg) = tyClsNamesOfType fun `unionNameSets` tyClsNamesOfType arg
1249 tyClsNamesOfType (ForAllTy _ ty) = tyClsNamesOfType ty
1251 tyClsNamesOfTypes :: [Type] -> NameSet
1252 tyClsNamesOfTypes tys = foldr (unionNameSets . tyClsNamesOfType) emptyNameSet tys
1254 tyClsNamesOfDFunHead :: Type -> NameSet
1255 -- Find the free type constructors and classes
1256 -- of the head of the dfun instance type
1257 -- The 'dfun_head_type' is because of
1258 -- instance Foo a => Baz T where ...
1259 -- The decl is an orphan if Baz and T are both not locally defined,
1260 -- even if Foo *is* locally defined
1261 tyClsNamesOfDFunHead dfun_ty
1262 = case tcSplitSigmaTy dfun_ty of
1263 (_, _, head_ty) -> tyClsNamesOfType head_ty
1267 %************************************************************************
1269 \subsection[TysWiredIn-ext-type]{External types}
1271 %************************************************************************
1273 The compiler's foreign function interface supports the passing of a
1274 restricted set of types as arguments and results (the restricting factor
1278 tcSplitIOType_maybe :: Type -> Maybe (TyCon, Type, CoercionI)
1279 -- (isIOType t) returns Just (IO,t',co)
1280 -- if co : t ~ IO t'
1281 -- returns Nothing otherwise
1282 tcSplitIOType_maybe ty
1283 = case tcSplitTyConApp_maybe ty of
1284 -- This split absolutely has to be a tcSplit, because we must
1285 -- see the IO type; and it's a newtype which is transparent to splitTyConApp.
1287 Just (io_tycon, [io_res_ty])
1288 | io_tycon `hasKey` ioTyConKey
1289 -> Just (io_tycon, io_res_ty, IdCo ty)
1292 | not (isRecursiveTyCon tc)
1293 , Just (ty, co1) <- instNewTyCon_maybe tc tys
1294 -- Newtypes that require a coercion are ok
1295 -> case tcSplitIOType_maybe ty of
1297 Just (tc, ty', co2) -> Just (tc, ty', co1 `mkTransCoI` co2)
1301 isFFITy :: Type -> Bool
1302 -- True for any TyCon that can possibly be an arg or result of an FFI call
1303 isFFITy ty = checkRepTyCon legalFFITyCon ty
1305 isFFIArgumentTy :: DynFlags -> Safety -> Type -> Bool
1306 -- Checks for valid argument type for a 'foreign import'
1307 isFFIArgumentTy dflags safety ty
1308 = checkRepTyCon (legalOutgoingTyCon dflags safety) ty
1310 isFFIExternalTy :: Type -> Bool
1311 -- Types that are allowed as arguments of a 'foreign export'
1312 isFFIExternalTy ty = checkRepTyCon legalFEArgTyCon ty
1314 isFFIImportResultTy :: DynFlags -> Type -> Bool
1315 isFFIImportResultTy dflags ty
1316 = checkRepTyCon (legalFIResultTyCon dflags) ty
1318 isFFIExportResultTy :: Type -> Bool
1319 isFFIExportResultTy ty = checkRepTyCon legalFEResultTyCon ty
1321 isFFIDynArgumentTy :: Type -> Bool
1322 -- The argument type of a foreign import dynamic must be Ptr, FunPtr, Addr,
1323 -- or a newtype of either.
1324 isFFIDynArgumentTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1326 isFFIDynResultTy :: Type -> Bool
1327 -- The result type of a foreign export dynamic must be Ptr, FunPtr, Addr,
1328 -- or a newtype of either.
1329 isFFIDynResultTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1331 isFFILabelTy :: Type -> Bool
1332 -- The type of a foreign label must be Ptr, FunPtr, Addr,
1333 -- or a newtype of either.
1334 isFFILabelTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1336 isFFIPrimArgumentTy :: DynFlags -> Type -> Bool
1337 -- Checks for valid argument type for a 'foreign import prim'
1338 -- Currently they must all be simple unlifted types.
1339 isFFIPrimArgumentTy dflags ty
1340 = checkRepTyCon (legalFIPrimArgTyCon dflags) ty
1342 isFFIPrimResultTy :: DynFlags -> Type -> Bool
1343 -- Checks for valid result type for a 'foreign import prim'
1344 -- Currently it must be an unlifted type, including unboxed tuples.
1345 isFFIPrimResultTy dflags ty
1346 = checkRepTyCon (legalFIPrimResultTyCon dflags) ty
1348 isFFIDotnetTy :: DynFlags -> Type -> Bool
1349 isFFIDotnetTy dflags ty
1350 = checkRepTyCon (\ tc -> (legalFIResultTyCon dflags tc ||
1351 isFFIDotnetObjTy ty || isStringTy ty)) ty
1352 -- NB: isStringTy used to look through newtypes, but
1353 -- it no longer does so. May need to adjust isFFIDotNetTy
1354 -- if we do want to look through newtypes.
1356 isFFIDotnetObjTy :: Type -> Bool
1358 = checkRepTyCon check_tc t_ty
1360 (_, t_ty) = tcSplitForAllTys ty
1361 check_tc tc = getName tc == objectTyConName
1363 isFunPtrTy :: Type -> Bool
1364 isFunPtrTy = checkRepTyConKey [funPtrTyConKey]
1366 checkRepTyCon :: (TyCon -> Bool) -> Type -> Bool
1367 -- Look through newtypes, but *not* foralls
1368 -- Should work even for recursive newtypes
1369 -- eg Manuel had: newtype T = MkT (Ptr T)
1370 checkRepTyCon check_tc ty
1374 | Just (tc,tys) <- splitTyConApp_maybe ty
1375 = case carefullySplitNewType_maybe rec_nts tc tys of
1376 Just (rec_nts', ty') -> go rec_nts' ty'
1377 Nothing -> check_tc tc
1381 checkRepTyConKey :: [Unique] -> Type -> Bool
1382 -- Like checkRepTyCon, but just looks at the TyCon key
1383 checkRepTyConKey keys
1384 = checkRepTyCon (\tc -> tyConUnique tc `elem` keys)
1387 ----------------------------------------------
1388 These chaps do the work; they are not exported
1389 ----------------------------------------------
1392 legalFEArgTyCon :: TyCon -> Bool
1394 -- It's illegal to make foreign exports that take unboxed
1395 -- arguments. The RTS API currently can't invoke such things. --SDM 7/2000
1396 = boxedMarshalableTyCon tc
1398 legalFIResultTyCon :: DynFlags -> TyCon -> Bool
1399 legalFIResultTyCon dflags tc
1400 | tc == unitTyCon = True
1401 | otherwise = marshalableTyCon dflags tc
1403 legalFEResultTyCon :: TyCon -> Bool
1404 legalFEResultTyCon tc
1405 | tc == unitTyCon = True
1406 | otherwise = boxedMarshalableTyCon tc
1408 legalOutgoingTyCon :: DynFlags -> Safety -> TyCon -> Bool
1409 -- Checks validity of types going from Haskell -> external world
1410 legalOutgoingTyCon dflags _ tc
1411 = marshalableTyCon dflags tc
1413 legalFFITyCon :: TyCon -> Bool
1414 -- True for any TyCon that can possibly be an arg or result of an FFI call
1416 = isUnLiftedTyCon tc || boxedMarshalableTyCon tc || tc == unitTyCon
1418 marshalableTyCon :: DynFlags -> TyCon -> Bool
1419 marshalableTyCon dflags tc
1420 = (xopt Opt_UnliftedFFITypes dflags
1421 && isUnLiftedTyCon tc
1422 && not (isUnboxedTupleTyCon tc)
1423 && case tyConPrimRep tc of -- Note [Marshalling VoidRep]
1426 || boxedMarshalableTyCon tc
1428 boxedMarshalableTyCon :: TyCon -> Bool
1429 boxedMarshalableTyCon tc
1430 = getUnique tc `elem` [ intTyConKey, int8TyConKey, int16TyConKey
1431 , int32TyConKey, int64TyConKey
1432 , wordTyConKey, word8TyConKey, word16TyConKey
1433 , word32TyConKey, word64TyConKey
1434 , floatTyConKey, doubleTyConKey
1435 , ptrTyConKey, funPtrTyConKey
1441 legalFIPrimArgTyCon :: DynFlags -> TyCon -> Bool
1442 -- Check args of 'foreign import prim', only allow simple unlifted types.
1443 -- Strictly speaking it is unnecessary to ban unboxed tuples here since
1444 -- currently they're of the wrong kind to use in function args anyway.
1445 legalFIPrimArgTyCon dflags tc
1446 = xopt Opt_UnliftedFFITypes dflags
1447 && isUnLiftedTyCon tc
1448 && not (isUnboxedTupleTyCon tc)
1450 legalFIPrimResultTyCon :: DynFlags -> TyCon -> Bool
1451 -- Check result type of 'foreign import prim'. Allow simple unlifted
1452 -- types and also unboxed tuple result types '... -> (# , , #)'
1453 legalFIPrimResultTyCon dflags tc
1454 = xopt Opt_UnliftedFFITypes dflags
1455 && isUnLiftedTyCon tc
1456 && (isUnboxedTupleTyCon tc
1457 || case tyConPrimRep tc of -- Note [Marshalling VoidRep]
1462 Note [Marshalling VoidRep]
1463 ~~~~~~~~~~~~~~~~~~~~~~~~~~
1464 We don't treat State# (whose PrimRep is VoidRep) as marshalable.
1465 In turn that means you can't write
1466 foreign import foo :: Int -> State# RealWorld
1468 Reason: the back end falls over with panic "primRepHint:VoidRep";
1469 and there is no compelling reason to permit it