2 % (c) The University of Glasgow 2006
3 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
5 \section[TcType]{Types used in the typechecker}
7 This module provides the Type interface for front-end parts of the
10 * treat "source types" as opaque:
11 newtypes, and predicates are meaningful.
12 * look through usage types
14 The "tc" prefix is for "TypeChecker", because the type checker
15 is the principal client.
19 --------------------------------
21 TcType, TcSigmaType, TcRhoType, TcTauType, TcPredType, TcThetaType,
22 TcTyVar, TcTyVarSet, TcKind,
24 BoxyTyVar, BoxySigmaType, BoxyRhoType, BoxyThetaType, BoxyType,
26 --------------------------------
28 UserTypeCtxt(..), pprUserTypeCtxt,
29 TcTyVarDetails(..), BoxInfo(..), pprTcTyVarDetails,
30 MetaDetails(Flexi, Indirect), SkolemInfo(..), pprSkolTvBinding, pprSkolInfo,
31 isImmutableTyVar, isSkolemTyVar, isMetaTyVar, isBoxyTyVar, isSigTyVar, isExistentialTyVar,
35 --------------------------------
39 --------------------------------
41 -- These are important because they do not look through newtypes
43 tcSplitForAllTys, tcSplitPhiTy,
44 tcSplitFunTy_maybe, tcSplitFunTys, tcFunArgTy, tcFunResultTy, tcSplitFunTysN,
45 tcSplitTyConApp, tcSplitTyConApp_maybe, tcTyConAppTyCon, tcTyConAppArgs,
46 tcSplitAppTy_maybe, tcSplitAppTy, tcSplitAppTys, repSplitAppTy_maybe,
47 tcValidInstHeadTy, tcGetTyVar_maybe, tcGetTyVar,
48 tcSplitSigmaTy, tcMultiSplitSigmaTy,
50 ---------------------------------
52 -- Again, newtypes are opaque
53 tcEqType, tcEqTypes, tcEqPred, tcCmpType, tcCmpTypes, tcCmpPred, tcEqTypeX,
55 isSigmaTy, isOverloadedTy, isRigidTy, isBoxyTy,
56 isDoubleTy, isFloatTy, isIntTy, isStringTy,
57 isIntegerTy, isBoolTy, isUnitTy,
58 isTauTy, isTauTyCon, tcIsTyVarTy, tcIsForAllTy,
60 ---------------------------------
61 -- Misc type manipulators
63 tyClsNamesOfType, tyClsNamesOfDFunHead,
66 ---------------------------------
68 getClassPredTys_maybe, getClassPredTys,
69 isClassPred, isTyVarClassPred, isEqPred,
70 mkDictTy, tcSplitPredTy_maybe,
71 isPredTy, isDictTy, tcSplitDFunTy, tcSplitDFunHead, predTyUnique,
72 mkClassPred, isInheritablePred, isIPPred,
73 dataConsStupidTheta, isRefineableTy, isRefineablePred,
75 ---------------------------------
76 -- Foreign import and export
77 isFFIArgumentTy, -- :: DynFlags -> Safety -> Type -> Bool
78 isFFIImportResultTy, -- :: DynFlags -> Type -> Bool
79 isFFIExportResultTy, -- :: Type -> Bool
80 isFFIExternalTy, -- :: Type -> Bool
81 isFFIDynArgumentTy, -- :: Type -> Bool
82 isFFIDynResultTy, -- :: Type -> Bool
83 isFFILabelTy, -- :: Type -> Bool
84 isFFIDotnetTy, -- :: DynFlags -> Type -> Bool
85 isFFIDotnetObjTy, -- :: Type -> Bool
86 isFFITy, -- :: Type -> Bool
87 tcSplitIOType_maybe, -- :: Type -> Maybe Type
88 toDNType, -- :: Type -> DNType
90 --------------------------------
91 -- Rexported from Type
92 Kind, -- Stuff to do with kinds is insensitive to pre/post Tc
93 unliftedTypeKind, liftedTypeKind, argTypeKind,
94 openTypeKind, mkArrowKind, mkArrowKinds,
95 isLiftedTypeKind, isUnliftedTypeKind, isSubOpenTypeKind,
96 isSubArgTypeKind, isSubKind, defaultKind,
97 kindVarRef, mkKindVar,
99 Type, PredType(..), ThetaType,
100 mkForAllTy, mkForAllTys,
101 mkFunTy, mkFunTys, zipFunTys,
102 mkTyConApp, mkAppTy, mkAppTys, applyTy, applyTys,
103 mkTyVarTy, mkTyVarTys, mkTyConTy, mkPredTy, mkPredTys,
105 -- Type substitutions
106 TvSubst(..), -- Representation visible to a few friends
107 TvSubstEnv, emptyTvSubst, substEqSpec,
108 mkOpenTvSubst, zipOpenTvSubst, zipTopTvSubst, mkTopTvSubst, notElemTvSubst,
109 getTvSubstEnv, setTvSubstEnv, getTvInScope, extendTvInScope, lookupTyVar,
110 extendTvSubst, extendTvSubstList, isInScope, mkTvSubst, zipTyEnv,
111 substTy, substTys, substTyWith, substTheta, substTyVar, substTyVars, substTyVarBndr,
113 isUnLiftedType, -- Source types are always lifted
114 isUnboxedTupleType, -- Ditto
117 tidyTopType, tidyType, tidyPred, tidyTypes, tidyFreeTyVars, tidyOpenType, tidyOpenTypes,
118 tidyTyVarBndr, tidyOpenTyVar, tidyOpenTyVars, tidySkolemTyVar,
121 tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tyVarsOfTheta,
122 tcTyVarsOfType, tcTyVarsOfTypes, exactTyVarsOfType, exactTyVarsOfTypes,
124 pprKind, pprParendKind,
125 pprType, pprParendType, pprTypeApp, pprTyThingCategory,
126 pprPred, pprTheta, pprThetaArrow, pprClassPred
130 #include "HsVersions.h"
163 %************************************************************************
167 %************************************************************************
169 The type checker divides the generic Type world into the
170 following more structured beasts:
172 sigma ::= forall tyvars. phi
173 -- A sigma type is a qualified type
175 -- Note that even if 'tyvars' is empty, theta
176 -- may not be: e.g. (?x::Int) => Int
178 -- Note that 'sigma' is in prenex form:
179 -- all the foralls are at the front.
180 -- A 'phi' type has no foralls to the right of
188 -- A 'tau' type has no quantification anywhere
189 -- Note that the args of a type constructor must be taus
191 | tycon tau_1 .. tau_n
195 -- In all cases, a (saturated) type synonym application is legal,
196 -- provided it expands to the required form.
199 type TcTyVar = TyVar -- Used only during type inference
200 type TcType = Type -- A TcType can have mutable type variables
201 -- Invariant on ForAllTy in TcTypes:
203 -- a cannot occur inside a MutTyVar in T; that is,
204 -- T is "flattened" before quantifying over a
206 -- These types do not have boxy type variables in them
207 type TcPredType = PredType
208 type TcThetaType = ThetaType
209 type TcSigmaType = TcType
210 type TcRhoType = TcType
211 type TcTauType = TcType
213 type TcTyVarSet = TyVarSet
215 -- These types may have boxy type variables in them
216 type BoxyTyVar = TcTyVar
217 type BoxyRhoType = TcType
218 type BoxyThetaType = TcThetaType
219 type BoxySigmaType = TcType
220 type BoxyType = TcType
224 %************************************************************************
226 \subsection{TyVarDetails}
228 %************************************************************************
230 TyVarDetails gives extra info about type variables, used during type
231 checking. It's attached to mutable type variables only.
232 It's knot-tied back to Var.lhs. There is no reason in principle
233 why Var.lhs shouldn't actually have the definition, but it "belongs" here.
236 Note [Signature skolems]
237 ~~~~~~~~~~~~~~~~~~~~~~~~
242 (x,y,z) = ([y,z], z, head x)
244 Here, x and y have type sigs, which go into the environment. We used to
245 instantiate their types with skolem constants, and push those types into
246 the RHS, so we'd typecheck the RHS with type
248 where a*, b* are skolem constants, and c is an ordinary meta type varible.
250 The trouble is that the occurrences of z in the RHS force a* and b* to
251 be the *same*, so we can't make them into skolem constants that don't unify
252 with each other. Alas.
254 One solution would be insist that in the above defn the programmer uses
255 the same type variable in both type signatures. But that takes explanation.
257 The alternative (currently implemented) is to have a special kind of skolem
258 constant, SigTv, which can unify with other SigTvs. These are *not* treated
259 as righd for the purposes of GADTs. And they are used *only* for pattern
260 bindings and mutually recursive function bindings. See the function
261 TcBinds.tcInstSig, and its use_skols parameter.
265 -- A TyVarDetails is inside a TyVar
267 = SkolemTv SkolemInfo -- A skolem constant
269 | MetaTv BoxInfo (IORef MetaDetails)
272 = BoxTv -- The contents is a (non-boxy) sigma-type
273 -- That is, this MetaTv is a "box"
275 | TauTv -- The contents is a (non-boxy) tau-type
276 -- That is, this MetaTv is an ordinary unification variable
278 | SigTv SkolemInfo -- A variant of TauTv, except that it should not be
279 -- unified with a type, only with a type variable
280 -- SigTvs are only distinguished to improve error messages
281 -- see Note [Signature skolems]
282 -- The MetaDetails, if filled in, will
283 -- always be another SigTv or a SkolemTv
286 -- A TauTv is always filled in with a tau-type, which
287 -- never contains any BoxTvs, nor any ForAlls
289 -- However, a BoxTv can contain a type that contains further BoxTvs
290 -- Notably, when typechecking an explicit list, say [e1,e2], with
291 -- expected type being a box b1, we fill in b1 with (List b2), where
292 -- b2 is another (currently empty) box.
295 = Flexi -- Flexi type variables unify to become
298 | Indirect TcType -- INVARIANT:
299 -- For a BoxTv, this type must be non-boxy
300 -- For a TauTv, this type must be a tau-type
302 -- Generally speaking, SkolemInfo should not contain location info
303 -- that is contained in the Name of the tyvar with this SkolemInfo
305 = SigSkol UserTypeCtxt -- A skolem that is created by instantiating
306 -- a programmer-supplied type signature
307 -- Location of the binding site is on the TyVar
309 -- The rest are for non-scoped skolems
310 | ClsSkol Class -- Bound at a class decl
311 | InstSkol -- Bound at an instance decl
312 | FamInstSkol -- Bound at a family instance decl
313 | PatSkol DataCon -- An existential type variable bound by a pattern for
314 -- a data constructor with an existential type. E.g.
315 -- data T = forall a. Eq a => MkT a
317 -- The pattern MkT x will allocate an existential type
319 | ArrowSkol -- An arrow form (see TcArrows)
321 | RuleSkol RuleName -- The LHS of a RULE
322 | GenSkol [TcTyVar] -- Bound when doing a subsumption check for
323 TcType -- (forall tvs. ty)
325 | UnkSkol -- Unhelpful info (until I improve it)
327 -------------------------------------
328 -- UserTypeCtxt describes the places where a
329 -- programmer-written type signature can occur
330 -- Like SkolemInfo, no location info
332 = FunSigCtxt Name -- Function type signature
333 -- Also used for types in SPECIALISE pragmas
334 | ExprSigCtxt -- Expression type signature
335 | ConArgCtxt Name -- Data constructor argument
336 | TySynCtxt Name -- RHS of a type synonym decl
337 | GenPatCtxt -- Pattern in generic decl
338 -- f{| a+b |} (Inl x) = ...
339 | LamPatSigCtxt -- Type sig in lambda pattern
341 | BindPatSigCtxt -- Type sig in pattern binding pattern
343 | ResSigCtxt -- Result type sig
345 | ForSigCtxt Name -- Foreign inport or export signature
346 | DefaultDeclCtxt -- Types in a default declaration
347 | SpecInstCtxt -- SPECIALISE instance pragma
349 -- Notes re TySynCtxt
350 -- We allow type synonyms that aren't types; e.g. type List = []
352 -- If the RHS mentions tyvars that aren't in scope, we'll
353 -- quantify over them:
354 -- e.g. type T = a->a
355 -- will become type T = forall a. a->a
357 -- With gla-exts that's right, but for H98 we should complain.
359 ---------------------------------
362 mkKindName :: Unique -> Name
363 mkKindName unique = mkSystemName unique kind_var_occ
365 kindVarRef :: KindVar -> IORef MetaDetails
367 ASSERT ( isTcTyVar tc )
368 case tcTyVarDetails tc of
369 MetaTv TauTv ref -> ref
370 other -> pprPanic "kindVarRef" (ppr tc)
372 mkKindVar :: Unique -> IORef MetaDetails -> KindVar
374 = mkTcTyVar (mkKindName u)
375 tySuperKind -- not sure this is right,
376 -- do we need kind vars for
380 kind_var_occ :: OccName -- Just one for all KindVars
381 -- They may be jiggled by tidying
382 kind_var_occ = mkOccName tvName "k"
386 %************************************************************************
390 %************************************************************************
393 pprTcTyVarDetails :: TcTyVarDetails -> SDoc
395 pprTcTyVarDetails (SkolemTv _) = ptext SLIT("sk")
396 pprTcTyVarDetails (MetaTv BoxTv _) = ptext SLIT("box")
397 pprTcTyVarDetails (MetaTv TauTv _) = ptext SLIT("tau")
398 pprTcTyVarDetails (MetaTv (SigTv _) _) = ptext SLIT("sig")
400 pprUserTypeCtxt :: UserTypeCtxt -> SDoc
401 pprUserTypeCtxt (FunSigCtxt n) = ptext SLIT("the type signature for") <+> quotes (ppr n)
402 pprUserTypeCtxt ExprSigCtxt = ptext SLIT("an expression type signature")
403 pprUserTypeCtxt (ConArgCtxt c) = ptext SLIT("the type of the constructor") <+> quotes (ppr c)
404 pprUserTypeCtxt (TySynCtxt c) = ptext SLIT("the RHS of the type synonym") <+> quotes (ppr c)
405 pprUserTypeCtxt GenPatCtxt = ptext SLIT("the type pattern of a generic definition")
406 pprUserTypeCtxt LamPatSigCtxt = ptext SLIT("a pattern type signature")
407 pprUserTypeCtxt BindPatSigCtxt = ptext SLIT("a pattern type signature")
408 pprUserTypeCtxt ResSigCtxt = ptext SLIT("a result type signature")
409 pprUserTypeCtxt (ForSigCtxt n) = ptext SLIT("the foreign declaration for") <+> quotes (ppr n)
410 pprUserTypeCtxt DefaultDeclCtxt = ptext SLIT("a type in a `default' declaration")
411 pprUserTypeCtxt SpecInstCtxt = ptext SLIT("a SPECIALISE instance pragma")
414 --------------------------------
415 tidySkolemTyVar :: TidyEnv -> TcTyVar -> (TidyEnv, TcTyVar)
416 -- Tidy the type inside a GenSkol, preparatory to printing it
417 tidySkolemTyVar env tv
418 = ASSERT( isSkolemTyVar tv || isSigTyVar tv )
419 (env1, mkTcTyVar (tyVarName tv) (tyVarKind tv) info1)
421 (env1, info1) = case tcTyVarDetails tv of
422 SkolemTv info -> (env1, SkolemTv info')
424 (env1, info') = tidy_skol_info env info
425 MetaTv (SigTv info) box -> (env1, MetaTv (SigTv info') box)
427 (env1, info') = tidy_skol_info env info
430 tidy_skol_info env (GenSkol tvs ty) = (env2, GenSkol tvs1 ty1)
432 (env1, tvs1) = tidyOpenTyVars env tvs
433 (env2, ty1) = tidyOpenType env1 ty
434 tidy_skol_info env info = (env, info)
436 pprSkolTvBinding :: TcTyVar -> SDoc
437 -- Print info about the binding of a skolem tyvar,
438 -- or nothing if we don't have anything useful to say
440 = ASSERT ( isTcTyVar tv )
441 ppr_details (tcTyVarDetails tv)
443 ppr_details (MetaTv TauTv _) = quotes (ppr tv) <+> ptext SLIT("is a meta type variable")
444 ppr_details (MetaTv BoxTv _) = quotes (ppr tv) <+> ptext SLIT("is a boxy type variable")
445 ppr_details (MetaTv (SigTv info) _) = ppr_skol info
446 ppr_details (SkolemTv info) = ppr_skol info
448 ppr_skol UnkSkol = empty -- Unhelpful; omit
449 ppr_skol info = quotes (ppr tv) <+> ptext SLIT("is bound by")
450 <+> sep [pprSkolInfo info, nest 2 (ptext SLIT("at") <+> ppr (getSrcLoc tv))]
452 pprSkolInfo :: SkolemInfo -> SDoc
453 pprSkolInfo (SigSkol ctxt) = pprUserTypeCtxt ctxt
454 pprSkolInfo (ClsSkol cls) = ptext SLIT("the class declaration for") <+> quotes (ppr cls)
455 pprSkolInfo InstSkol = ptext SLIT("the instance declaration")
456 pprSkolInfo FamInstSkol = ptext SLIT("the family instance declaration")
457 pprSkolInfo (RuleSkol name) = ptext SLIT("the RULE") <+> doubleQuotes (ftext name)
458 pprSkolInfo ArrowSkol = ptext SLIT("the arrow form")
459 pprSkolInfo (PatSkol dc) = sep [ptext SLIT("the constructor") <+> quotes (ppr dc)]
460 pprSkolInfo (GenSkol tvs ty) = sep [ptext SLIT("the polymorphic type"),
461 nest 2 (quotes (ppr (mkForAllTys tvs ty)))]
464 -- For type variables the others are dealt with by pprSkolTvBinding.
465 -- For Insts, these cases should not happen
466 pprSkolInfo UnkSkol = panic "UnkSkol"
468 instance Outputable MetaDetails where
469 ppr Flexi = ptext SLIT("Flexi")
470 ppr (Indirect ty) = ptext SLIT("Indirect") <+> ppr ty
474 %************************************************************************
478 %************************************************************************
481 isImmutableTyVar, isSkolemTyVar, isExistentialTyVar, isBoxyTyVar, isMetaTyVar :: TyVar -> Bool
483 | isTcTyVar tv = isSkolemTyVar tv
487 = ASSERT( isTcTyVar tv )
488 case tcTyVarDetails tv of
492 isExistentialTyVar tv -- Existential type variable, bound by a pattern
493 = ASSERT( isTcTyVar tv )
494 case tcTyVarDetails tv of
495 SkolemTv (PatSkol {}) -> True
499 = ASSERT2( isTcTyVar tv, ppr tv )
500 case tcTyVarDetails tv of
505 = ASSERT( isTcTyVar tv )
506 case tcTyVarDetails tv of
507 MetaTv BoxTv _ -> True
511 = ASSERT( isTcTyVar tv )
512 case tcTyVarDetails tv of
513 MetaTv (SigTv _) _ -> True
516 metaTvRef :: TyVar -> IORef MetaDetails
518 = ASSERT( isTcTyVar tv )
519 case tcTyVarDetails tv of
521 other -> pprPanic "metaTvRef" (ppr tv)
523 isFlexi, isIndirect :: MetaDetails -> Bool
525 isFlexi other = False
527 isIndirect (Indirect _) = True
528 isIndirect other = False
532 %************************************************************************
534 \subsection{Tau, sigma and rho}
536 %************************************************************************
539 mkSigmaTy :: [TyVar] -> [PredType] -> Type -> Type
540 mkSigmaTy tyvars theta tau = mkForAllTys tyvars (mkPhiTy theta tau)
542 mkPhiTy :: [PredType] -> Type -> Type
543 mkPhiTy theta ty = foldr (\p r -> mkFunTy (mkPredTy p) r) ty theta
546 @isTauTy@ tests for nested for-alls. It should not be called on a boxy type.
549 isTauTy :: Type -> Bool
550 isTauTy ty | Just ty' <- tcView ty = isTauTy ty'
551 isTauTy (TyVarTy tv) = ASSERT( not (isTcTyVar tv && isBoxyTyVar tv) )
553 isTauTy (TyConApp tc tys) = all isTauTy tys && isTauTyCon tc
554 isTauTy (AppTy a b) = isTauTy a && isTauTy b
555 isTauTy (FunTy a b) = isTauTy a && isTauTy b
556 isTauTy (PredTy p) = True -- Don't look through source types
557 isTauTy other = False
560 isTauTyCon :: TyCon -> Bool
561 -- Returns False for type synonyms whose expansion is a polytype
563 | isClosedSynTyCon tc = isTauTy (snd (synTyConDefn tc))
567 isBoxyTy :: TcType -> Bool
568 isBoxyTy ty = any isBoxyTyVar (varSetElems (tcTyVarsOfType ty))
570 isRigidTy :: TcType -> Bool
571 -- A type is rigid if it has no meta type variables in it
572 isRigidTy ty = all isImmutableTyVar (varSetElems (tcTyVarsOfType ty))
574 isRefineableTy :: TcType -> Bool
575 -- A type should have type refinements applied to it if it has
576 -- free type variables, and they are all rigid
577 isRefineableTy ty = not (null tc_tvs) && all isImmutableTyVar tc_tvs
579 tc_tvs = varSetElems (tcTyVarsOfType ty)
581 isRefineablePred :: TcPredType -> Bool
582 isRefineablePred pred = not (null tc_tvs) && all isImmutableTyVar tc_tvs
584 tc_tvs = varSetElems (tcTyVarsOfPred pred)
587 getDFunTyKey :: Type -> OccName -- Get some string from a type, to be used to
588 -- construct a dictionary function name
589 getDFunTyKey ty | Just ty' <- tcView ty = getDFunTyKey ty'
590 getDFunTyKey (TyVarTy tv) = getOccName tv
591 getDFunTyKey (TyConApp tc _) = getOccName tc
592 getDFunTyKey (AppTy fun _) = getDFunTyKey fun
593 getDFunTyKey (FunTy arg _) = getOccName funTyCon
594 getDFunTyKey (ForAllTy _ t) = getDFunTyKey t
595 getDFunTyKey ty = pprPanic "getDFunTyKey" (pprType ty)
596 -- PredTy shouldn't happen
600 %************************************************************************
602 \subsection{Expanding and splitting}
604 %************************************************************************
606 These tcSplit functions are like their non-Tc analogues, but
607 a) they do not look through newtypes
608 b) they do not look through PredTys
609 c) [future] they ignore usage-type annotations
611 However, they are non-monadic and do not follow through mutable type
612 variables. It's up to you to make sure this doesn't matter.
615 tcSplitForAllTys :: Type -> ([TyVar], Type)
616 tcSplitForAllTys ty = split ty ty []
618 split orig_ty ty tvs | Just ty' <- tcView ty = split orig_ty ty' tvs
619 split orig_ty (ForAllTy tv ty) tvs
620 | not (isCoVar tv) = split ty ty (tv:tvs)
621 split orig_ty t tvs = (reverse tvs, orig_ty)
623 tcIsForAllTy ty | Just ty' <- tcView ty = tcIsForAllTy ty'
624 tcIsForAllTy (ForAllTy tv ty) = not (isCoVar tv)
625 tcIsForAllTy t = False
627 tcSplitPhiTy :: Type -> (ThetaType, Type)
628 tcSplitPhiTy ty = split ty ty []
630 split orig_ty ty tvs | Just ty' <- tcView ty = split orig_ty ty' tvs
632 split orig_ty (ForAllTy tv ty) ts
633 | isCoVar tv = split ty ty (eq_pred:ts)
635 PredTy eq_pred = tyVarKind tv
636 split orig_ty (FunTy arg res) ts
637 | Just p <- tcSplitPredTy_maybe arg = split res res (p:ts)
638 split orig_ty ty ts = (reverse ts, orig_ty)
640 tcSplitSigmaTy :: Type -> ([TyVar], ThetaType, Type)
641 tcSplitSigmaTy ty = case tcSplitForAllTys ty of
642 (tvs, rho) -> case tcSplitPhiTy rho of
643 (theta, tau) -> (tvs, theta, tau)
645 -----------------------
648 -> ( [([TyVar], ThetaType)], -- forall as.C => forall bs.D
649 TcSigmaType) -- The rest of the type
651 -- We need a loop here because we are now prepared to entertain
653 -- f:: forall a. Eq a => forall b. Baz b => tau
654 -- We want to instantiate this to
655 -- f2::tau {f2 = f1 b (Baz b), f1 = f a (Eq a)}
657 tcMultiSplitSigmaTy sigma
658 = case (tcSplitSigmaTy sigma) of
659 ([],[],ty) -> ([], sigma)
660 (tvs, theta, ty) -> case tcMultiSplitSigmaTy ty of
661 (pairs, rest) -> ((tvs,theta):pairs, rest)
663 -----------------------
664 tcTyConAppTyCon :: Type -> TyCon
665 tcTyConAppTyCon ty = case tcSplitTyConApp_maybe ty of
667 Nothing -> pprPanic "tcTyConAppTyCon" (pprType ty)
669 tcTyConAppArgs :: Type -> [Type]
670 tcTyConAppArgs ty = case tcSplitTyConApp_maybe ty of
671 Just (_, args) -> args
672 Nothing -> pprPanic "tcTyConAppArgs" (pprType ty)
674 tcSplitTyConApp :: Type -> (TyCon, [Type])
675 tcSplitTyConApp ty = case tcSplitTyConApp_maybe ty of
677 Nothing -> pprPanic "tcSplitTyConApp" (pprType ty)
679 tcSplitTyConApp_maybe :: Type -> Maybe (TyCon, [Type])
680 tcSplitTyConApp_maybe ty | Just ty' <- tcView ty = tcSplitTyConApp_maybe ty'
681 tcSplitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
682 tcSplitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res])
683 -- Newtypes are opaque, so they may be split
684 -- However, predicates are not treated
685 -- as tycon applications by the type checker
686 tcSplitTyConApp_maybe other = Nothing
688 -----------------------
689 tcSplitFunTys :: Type -> ([Type], Type)
690 tcSplitFunTys ty = case tcSplitFunTy_maybe ty of
692 Just (arg,res) -> (arg:args, res')
694 (args,res') = tcSplitFunTys res
696 tcSplitFunTy_maybe :: Type -> Maybe (Type, Type)
697 tcSplitFunTy_maybe ty | Just ty' <- tcView ty = tcSplitFunTy_maybe ty'
698 tcSplitFunTy_maybe (FunTy arg res) = Just (arg, res)
699 tcSplitFunTy_maybe other = Nothing
703 -> Arity -- N: Number of desired args
704 -> ([TcSigmaType], -- Arg types (N or fewer)
705 TcSigmaType) -- The rest of the type
707 tcSplitFunTysN ty n_args
710 | Just (arg,res) <- tcSplitFunTy_maybe ty
711 = case tcSplitFunTysN res (n_args - 1) of
712 (args, res) -> (arg:args, res)
716 tcSplitFunTy ty = expectJust "tcSplitFunTy" (tcSplitFunTy_maybe ty)
717 tcFunArgTy ty = fst (tcSplitFunTy ty)
718 tcFunResultTy ty = snd (tcSplitFunTy ty)
720 -----------------------
721 tcSplitAppTy_maybe :: Type -> Maybe (Type, Type)
722 tcSplitAppTy_maybe ty | Just ty' <- tcView ty = tcSplitAppTy_maybe ty'
723 tcSplitAppTy_maybe ty = repSplitAppTy_maybe ty
725 tcSplitAppTy :: Type -> (Type, Type)
726 tcSplitAppTy ty = case tcSplitAppTy_maybe ty of
728 Nothing -> pprPanic "tcSplitAppTy" (pprType ty)
730 tcSplitAppTys :: Type -> (Type, [Type])
734 go ty args = case tcSplitAppTy_maybe ty of
735 Just (ty', arg) -> go ty' (arg:args)
738 -----------------------
739 tcGetTyVar_maybe :: Type -> Maybe TyVar
740 tcGetTyVar_maybe ty | Just ty' <- tcView ty = tcGetTyVar_maybe ty'
741 tcGetTyVar_maybe (TyVarTy tv) = Just tv
742 tcGetTyVar_maybe other = Nothing
744 tcGetTyVar :: String -> Type -> TyVar
745 tcGetTyVar msg ty = expectJust msg (tcGetTyVar_maybe ty)
747 tcIsTyVarTy :: Type -> Bool
748 tcIsTyVarTy ty = maybeToBool (tcGetTyVar_maybe ty)
750 -----------------------
751 tcSplitDFunTy :: Type -> ([TyVar], [PredType], Class, [Type])
752 -- Split the type of a dictionary function
754 = case tcSplitSigmaTy ty of { (tvs, theta, tau) ->
755 case tcSplitDFunHead tau of { (clas, tys) ->
756 (tvs, theta, clas, tys) }}
758 tcSplitDFunHead :: Type -> (Class, [Type])
760 = case tcSplitPredTy_maybe tau of
761 Just (ClassP clas tys) -> (clas, tys)
762 other -> panic "tcSplitDFunHead"
764 tcValidInstHeadTy :: Type -> Bool
765 -- Used in Haskell-98 mode, for the argument types of an instance head
766 -- These must not be type synonyms, but everywhere else type synonyms
767 -- are transparent, so we need a special function here
770 NoteTy _ ty -> tcValidInstHeadTy ty
771 TyConApp tc tys -> not (isSynTyCon tc) && ok tys
772 FunTy arg res -> ok [arg, res]
775 -- Check that all the types are type variables,
776 -- and that each is distinct
777 ok tys = equalLength tvs tys && hasNoDups tvs
779 tvs = mapCatMaybes get_tv tys
781 get_tv (NoteTy _ ty) = get_tv ty -- Again, do not look
782 get_tv (TyVarTy tv) = Just tv -- through synonyms
783 get_tv other = Nothing
788 %************************************************************************
790 \subsection{Predicate types}
792 %************************************************************************
795 tcSplitPredTy_maybe :: Type -> Maybe PredType
796 -- Returns Just for predicates only
797 tcSplitPredTy_maybe ty | Just ty' <- tcView ty = tcSplitPredTy_maybe ty'
798 tcSplitPredTy_maybe (PredTy p) = Just p
799 tcSplitPredTy_maybe other = Nothing
801 predTyUnique :: PredType -> Unique
802 predTyUnique (IParam n _) = getUnique (ipNameName n)
803 predTyUnique (ClassP clas tys) = getUnique clas
807 --------------------- Dictionary types ---------------------------------
810 mkClassPred clas tys = ClassP clas tys
812 isClassPred :: PredType -> Bool
813 isClassPred (ClassP clas tys) = True
814 isClassPred other = False
816 isTyVarClassPred (ClassP clas tys) = all tcIsTyVarTy tys
817 isTyVarClassPred other = False
819 getClassPredTys_maybe :: PredType -> Maybe (Class, [Type])
820 getClassPredTys_maybe (ClassP clas tys) = Just (clas, tys)
821 getClassPredTys_maybe _ = Nothing
823 getClassPredTys :: PredType -> (Class, [Type])
824 getClassPredTys (ClassP clas tys) = (clas, tys)
825 getClassPredTys other = panic "getClassPredTys"
827 mkDictTy :: Class -> [Type] -> Type
828 mkDictTy clas tys = mkPredTy (ClassP clas tys)
830 isDictTy :: Type -> Bool
831 isDictTy ty | Just ty' <- tcView ty = isDictTy ty'
832 isDictTy (PredTy p) = isClassPred p
833 isDictTy other = False
836 --------------------- Implicit parameters ---------------------------------
839 isIPPred :: PredType -> Bool
840 isIPPred (IParam _ _) = True
841 isIPPred other = False
843 isInheritablePred :: PredType -> Bool
844 -- Can be inherited by a context. For example, consider
845 -- f x = let g y = (?v, y+x)
846 -- in (g 3 with ?v = 8,
848 -- The point is that g's type must be quantifed over ?v:
849 -- g :: (?v :: a) => a -> a
850 -- but it doesn't need to be quantified over the Num a dictionary
851 -- which can be free in g's rhs, and shared by both calls to g
852 isInheritablePred (ClassP _ _) = True
853 isInheritablePred (EqPred _ _) = True
854 isInheritablePred other = False
857 --------------------- Equality predicates ---------------------------------
859 substEqSpec :: TvSubst -> [(TyVar,Type)] -> [(TcType,TcType)]
860 substEqSpec subst eq_spec = [ (substTyVar subst tv, substTy subst ty)
861 | (tv,ty) <- eq_spec]
864 --------------------- The stupid theta (sigh) ---------------------------------
867 dataConsStupidTheta :: [DataCon] -> ThetaType
868 -- Union the stupid thetas from all the specified constructors (non-empty)
869 -- All the constructors should have the same result type, modulo alpha conversion
870 -- The resulting ThetaType uses type variables from the *first* constructor in the list
872 -- It's here because it's used in MkId.mkRecordSelId, and in TcExpr
873 dataConsStupidTheta (con1:cons)
874 = nubBy tcEqPred all_preds
876 all_preds = dataConStupidTheta con1 ++ other_stupids
877 res_tys1 = dataConResTys con1
878 tvs1 = tyVarsOfTypes res_tys1
879 other_stupids = [ substPred subst pred
881 , let Just subst = tcMatchTys tvs1 res_tys1 (dataConResTys con)
882 , pred <- dataConStupidTheta con ]
883 dataConsStupidTheta [] = panic "dataConsStupidTheta"
887 %************************************************************************
889 \subsection{Predicates}
891 %************************************************************************
893 isSigmaTy returns true of any qualified type. It doesn't *necessarily* have
895 f :: (?x::Int) => Int -> Int
898 isSigmaTy :: Type -> Bool
899 isSigmaTy ty | Just ty' <- tcView ty = isSigmaTy ty'
900 isSigmaTy (ForAllTy tyvar ty) = True
901 isSigmaTy (FunTy a b) = isPredTy a
904 isOverloadedTy :: Type -> Bool
905 isOverloadedTy ty | Just ty' <- tcView ty = isOverloadedTy ty'
906 isOverloadedTy (ForAllTy tyvar ty) = isOverloadedTy ty
907 isOverloadedTy (FunTy a b) = isPredTy a
908 isOverloadedTy _ = False
910 isPredTy :: Type -> Bool -- Belongs in TcType because it does
911 -- not look through newtypes, or predtypes (of course)
912 isPredTy ty | Just ty' <- tcView ty = isPredTy ty'
913 isPredTy (PredTy sty) = True
918 isFloatTy = is_tc floatTyConKey
919 isDoubleTy = is_tc doubleTyConKey
920 isIntegerTy = is_tc integerTyConKey
921 isIntTy = is_tc intTyConKey
922 isBoolTy = is_tc boolTyConKey
923 isUnitTy = is_tc unitTyConKey
925 is_tc :: Unique -> Type -> Bool
926 -- Newtypes are opaque to this
927 is_tc uniq ty = case tcSplitTyConApp_maybe ty of
928 Just (tc, _) -> uniq == getUnique tc
933 %************************************************************************
937 %************************************************************************
940 deNoteType :: Type -> Type
941 -- Remove all *outermost* type synonyms and other notes
942 deNoteType ty | Just ty' <- tcView ty = deNoteType ty'
947 tcTyVarsOfType :: Type -> TcTyVarSet
948 -- Just the *TcTyVars* free in the type
949 -- (Types.tyVarsOfTypes finds all free TyVars)
950 tcTyVarsOfType (TyVarTy tv) = if isTcTyVar tv then unitVarSet tv
952 tcTyVarsOfType (TyConApp tycon tys) = tcTyVarsOfTypes tys
953 tcTyVarsOfType (NoteTy _ ty) = tcTyVarsOfType ty
954 tcTyVarsOfType (PredTy sty) = tcTyVarsOfPred sty
955 tcTyVarsOfType (FunTy arg res) = tcTyVarsOfType arg `unionVarSet` tcTyVarsOfType res
956 tcTyVarsOfType (AppTy fun arg) = tcTyVarsOfType fun `unionVarSet` tcTyVarsOfType arg
957 tcTyVarsOfType (ForAllTy tyvar ty) = (tcTyVarsOfType ty `delVarSet` tyvar)
958 `unionVarSet` tcTyVarsOfTyVar tyvar
959 -- We do sometimes quantify over skolem TcTyVars
961 tcTyVarsOfTyVar :: TcTyVar -> TyVarSet
962 tcTyVarsOfTyVar tv | isCoVar tv = tcTyVarsOfType (tyVarKind tv)
963 | otherwise = emptyVarSet
965 tcTyVarsOfTypes :: [Type] -> TyVarSet
966 tcTyVarsOfTypes tys = foldr (unionVarSet.tcTyVarsOfType) emptyVarSet tys
968 tcTyVarsOfPred :: PredType -> TyVarSet
969 tcTyVarsOfPred (IParam _ ty) = tcTyVarsOfType ty
970 tcTyVarsOfPred (ClassP _ tys) = tcTyVarsOfTypes tys
971 tcTyVarsOfPred (EqPred ty1 ty2) = tcTyVarsOfType ty1 `unionVarSet` tcTyVarsOfType ty2
974 Note [Silly type synonym]
975 ~~~~~~~~~~~~~~~~~~~~~~~~~
978 What are the free tyvars of (T x)? Empty, of course!
979 Here's the example that Ralf Laemmel showed me:
980 foo :: (forall a. C u a -> C u a) -> u
981 mappend :: Monoid u => u -> u -> u
984 bar = foo (\t -> t `mappend` t)
985 We have to generalise at the arg to f, and we don't
986 want to capture the constraint (Monad (C u a)) because
987 it appears to mention a. Pretty silly, but it was useful to him.
989 exactTyVarsOfType is used by the type checker to figure out exactly
990 which type variables are mentioned in a type. It's also used in the
991 smart-app checking code --- see TcExpr.tcIdApp
994 exactTyVarsOfType :: TcType -> TyVarSet
995 -- Find the free type variables (of any kind)
996 -- but *expand* type synonyms. See Note [Silly type synonym] above.
1000 go ty | Just ty' <- tcView ty = go ty' -- This is the key line
1001 go (TyVarTy tv) = unitVarSet tv
1002 go (TyConApp tycon tys) = exactTyVarsOfTypes tys
1003 go (PredTy ty) = go_pred ty
1004 go (FunTy arg res) = go arg `unionVarSet` go res
1005 go (AppTy fun arg) = go fun `unionVarSet` go arg
1006 go (ForAllTy tyvar ty) = delVarSet (go ty) tyvar
1007 `unionVarSet` go_tv tyvar
1009 go_pred (IParam _ ty) = go ty
1010 go_pred (ClassP _ tys) = exactTyVarsOfTypes tys
1011 go_pred (EqPred ty1 ty2) = go ty1 `unionVarSet` go ty2
1013 go_tv tyvar | isCoVar tyvar = go (tyVarKind tyvar)
1014 | otherwise = emptyVarSet
1016 exactTyVarsOfTypes :: [TcType] -> TyVarSet
1017 exactTyVarsOfTypes tys = foldr (unionVarSet . exactTyVarsOfType) emptyVarSet tys
1020 Find the free tycons and classes of a type. This is used in the front
1021 end of the compiler.
1024 tyClsNamesOfType :: Type -> NameSet
1025 tyClsNamesOfType (TyVarTy tv) = emptyNameSet
1026 tyClsNamesOfType (TyConApp tycon tys) = unitNameSet (getName tycon) `unionNameSets` tyClsNamesOfTypes tys
1027 tyClsNamesOfType (NoteTy _ ty2) = tyClsNamesOfType ty2
1028 tyClsNamesOfType (PredTy (IParam n ty)) = tyClsNamesOfType ty
1029 tyClsNamesOfType (PredTy (ClassP cl tys)) = unitNameSet (getName cl) `unionNameSets` tyClsNamesOfTypes tys
1030 tyClsNamesOfType (PredTy (EqPred ty1 ty2)) = tyClsNamesOfType ty1 `unionNameSets` tyClsNamesOfType ty2
1031 tyClsNamesOfType (FunTy arg res) = tyClsNamesOfType arg `unionNameSets` tyClsNamesOfType res
1032 tyClsNamesOfType (AppTy fun arg) = tyClsNamesOfType fun `unionNameSets` tyClsNamesOfType arg
1033 tyClsNamesOfType (ForAllTy tyvar ty) = tyClsNamesOfType ty
1035 tyClsNamesOfTypes tys = foldr (unionNameSets . tyClsNamesOfType) emptyNameSet tys
1037 tyClsNamesOfDFunHead :: Type -> NameSet
1038 -- Find the free type constructors and classes
1039 -- of the head of the dfun instance type
1040 -- The 'dfun_head_type' is because of
1041 -- instance Foo a => Baz T where ...
1042 -- The decl is an orphan if Baz and T are both not locally defined,
1043 -- even if Foo *is* locally defined
1044 tyClsNamesOfDFunHead dfun_ty
1045 = case tcSplitSigmaTy dfun_ty of
1046 (tvs,_,head_ty) -> tyClsNamesOfType head_ty
1050 %************************************************************************
1052 \subsection[TysWiredIn-ext-type]{External types}
1054 %************************************************************************
1056 The compiler's foreign function interface supports the passing of a
1057 restricted set of types as arguments and results (the restricting factor
1061 tcSplitIOType_maybe :: Type -> Maybe (TyCon, Type)
1062 -- (isIOType t) returns (Just (IO,t')) if t is of the form (IO t'), or
1063 -- some newtype wrapping thereof
1064 -- returns Nothing otherwise
1065 tcSplitIOType_maybe ty
1066 | Just (io_tycon, [io_res_ty]) <- tcSplitTyConApp_maybe ty,
1067 -- This split absolutely has to be a tcSplit, because we must
1068 -- see the IO type; and it's a newtype which is transparent to splitTyConApp.
1069 io_tycon `hasKey` ioTyConKey
1070 = Just (io_tycon, io_res_ty)
1072 | Just ty' <- coreView ty -- Look through non-recursive newtypes
1073 = tcSplitIOType_maybe ty'
1078 isFFITy :: Type -> Bool
1079 -- True for any TyCon that can possibly be an arg or result of an FFI call
1080 isFFITy ty = checkRepTyCon legalFFITyCon ty
1082 isFFIArgumentTy :: DynFlags -> Safety -> Type -> Bool
1083 -- Checks for valid argument type for a 'foreign import'
1084 isFFIArgumentTy dflags safety ty
1085 = checkRepTyCon (legalOutgoingTyCon dflags safety) ty
1087 isFFIExternalTy :: Type -> Bool
1088 -- Types that are allowed as arguments of a 'foreign export'
1089 isFFIExternalTy ty = checkRepTyCon legalFEArgTyCon ty
1091 isFFIImportResultTy :: DynFlags -> Type -> Bool
1092 isFFIImportResultTy dflags ty
1093 = checkRepTyCon (legalFIResultTyCon dflags) ty
1095 isFFIExportResultTy :: Type -> Bool
1096 isFFIExportResultTy ty = checkRepTyCon legalFEResultTyCon ty
1098 isFFIDynArgumentTy :: Type -> Bool
1099 -- The argument type of a foreign import dynamic must be Ptr, FunPtr, Addr,
1100 -- or a newtype of either.
1101 isFFIDynArgumentTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1103 isFFIDynResultTy :: Type -> Bool
1104 -- The result type of a foreign export dynamic must be Ptr, FunPtr, Addr,
1105 -- or a newtype of either.
1106 isFFIDynResultTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1108 isFFILabelTy :: Type -> Bool
1109 -- The type of a foreign label must be Ptr, FunPtr, Addr,
1110 -- or a newtype of either.
1111 isFFILabelTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey]
1113 isFFIDotnetTy :: DynFlags -> Type -> Bool
1114 isFFIDotnetTy dflags ty
1115 = checkRepTyCon (\ tc -> (legalFIResultTyCon dflags tc ||
1116 isFFIDotnetObjTy ty || isStringTy ty)) ty
1118 -- Support String as an argument or result from a .NET FFI call.
1120 case tcSplitTyConApp_maybe (repType ty) of
1122 | tc == listTyCon ->
1123 case tcSplitTyConApp_maybe (repType arg_ty) of
1124 Just (cc,[]) -> cc == charTyCon
1128 -- Support String as an argument or result from a .NET FFI call.
1129 isFFIDotnetObjTy ty =
1131 (_, t_ty) = tcSplitForAllTys ty
1133 case tcSplitTyConApp_maybe (repType t_ty) of
1134 Just (tc, [arg_ty]) | getName tc == objectTyConName -> True
1137 toDNType :: Type -> DNType
1139 | isStringTy ty = DNString
1140 | isFFIDotnetObjTy ty = DNObject
1141 | Just (tc,argTys) <- tcSplitTyConApp_maybe ty
1142 = case lookup (getUnique tc) dn_assoc of
1145 | tc `hasKey` ioTyConKey -> toDNType (head argTys)
1146 | otherwise -> pprPanic ("toDNType: unsupported .NET type")
1147 (pprType ty <+> parens (hcat (map pprType argTys)) <+> ppr tc)
1148 | otherwise = panic "toDNType" -- Is this right?
1150 dn_assoc :: [ (Unique, DNType) ]
1151 dn_assoc = [ (unitTyConKey, DNUnit)
1152 , (intTyConKey, DNInt)
1153 , (int8TyConKey, DNInt8)
1154 , (int16TyConKey, DNInt16)
1155 , (int32TyConKey, DNInt32)
1156 , (int64TyConKey, DNInt64)
1157 , (wordTyConKey, DNInt)
1158 , (word8TyConKey, DNWord8)
1159 , (word16TyConKey, DNWord16)
1160 , (word32TyConKey, DNWord32)
1161 , (word64TyConKey, DNWord64)
1162 , (floatTyConKey, DNFloat)
1163 , (doubleTyConKey, DNDouble)
1164 , (ptrTyConKey, DNPtr)
1165 , (funPtrTyConKey, DNPtr)
1166 , (charTyConKey, DNChar)
1167 , (boolTyConKey, DNBool)
1170 checkRepTyCon :: (TyCon -> Bool) -> Type -> Bool
1171 -- Look through newtypes
1172 -- Non-recursive ones are transparent to splitTyConApp,
1173 -- but recursive ones aren't. Manuel had:
1174 -- newtype T = MkT (Ptr T)
1175 -- and wanted it to work...
1176 checkRepTyCon check_tc ty
1177 | Just (tc,_) <- splitTyConApp_maybe (repType ty) = check_tc tc
1180 checkRepTyConKey :: [Unique] -> Type -> Bool
1181 -- Like checkRepTyCon, but just looks at the TyCon key
1182 checkRepTyConKey keys
1183 = checkRepTyCon (\tc -> tyConUnique tc `elem` keys)
1186 ----------------------------------------------
1187 These chaps do the work; they are not exported
1188 ----------------------------------------------
1191 legalFEArgTyCon :: TyCon -> Bool
1193 -- It's illegal to make foreign exports that take unboxed
1194 -- arguments. The RTS API currently can't invoke such things. --SDM 7/2000
1195 = boxedMarshalableTyCon tc
1197 legalFIResultTyCon :: DynFlags -> TyCon -> Bool
1198 legalFIResultTyCon dflags tc
1199 | tc == unitTyCon = True
1200 | otherwise = marshalableTyCon dflags tc
1202 legalFEResultTyCon :: TyCon -> Bool
1203 legalFEResultTyCon tc
1204 | tc == unitTyCon = True
1205 | otherwise = boxedMarshalableTyCon tc
1207 legalOutgoingTyCon :: DynFlags -> Safety -> TyCon -> Bool
1208 -- Checks validity of types going from Haskell -> external world
1209 legalOutgoingTyCon dflags safety tc
1210 = marshalableTyCon dflags tc
1212 legalFFITyCon :: TyCon -> Bool
1213 -- True for any TyCon that can possibly be an arg or result of an FFI call
1215 = isUnLiftedTyCon tc || boxedMarshalableTyCon tc || tc == unitTyCon
1217 marshalableTyCon dflags tc
1218 = (dopt Opt_GlasgowExts dflags && isUnLiftedTyCon tc)
1219 || boxedMarshalableTyCon tc
1221 boxedMarshalableTyCon tc
1222 = getUnique tc `elem` [ intTyConKey, int8TyConKey, int16TyConKey
1223 , int32TyConKey, int64TyConKey
1224 , wordTyConKey, word8TyConKey, word16TyConKey
1225 , word32TyConKey, word64TyConKey
1226 , floatTyConKey, doubleTyConKey
1227 , ptrTyConKey, funPtrTyConKey