2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[TcType]{Types used in the typechecker}
6 This module provides the Type interface for front-end parts of the
9 * treat "source types" as opaque:
10 newtypes, and predicates are meaningful.
11 * look through usage types
13 The "tc" prefix is for "typechechecker", because the type checker
14 is the principal client.
18 --------------------------------
20 TcType, TcSigmaType, TcPhiType, TcTauType, TcPredType, TcThetaType,
21 TcTyVar, TcTyVarSet, TcKind,
23 --------------------------------
25 TyVarDetails(..), isUserTyVar, isSkolemTyVar, isHoleTyVar,
28 --------------------------------
32 --------------------------------
34 -- These are important because they do not look through newtypes
35 tcSplitForAllTys, tcSplitRhoTy,
36 tcSplitFunTy_maybe, tcSplitFunTys, tcFunArgTy, tcFunResultTy,
37 tcSplitTyConApp, tcSplitTyConApp_maybe, tcTyConAppTyCon, tcTyConAppArgs,
38 tcSplitAppTy_maybe, tcSplitAppTy, tcSplitSigmaTy,
39 tcSplitMethodTy, tcGetTyVar_maybe, tcGetTyVar,
41 ---------------------------------
43 -- Again, newtypes are opaque
44 tcEqType, tcEqTypes, tcEqPred, tcCmpType, tcCmpTypes, tcCmpPred,
45 isSigmaTy, isOverloadedTy,
46 isDoubleTy, isFloatTy, isIntTy,
47 isIntegerTy, isAddrTy, isBoolTy, isUnitTy, isForeignPtrTy,
48 isTauTy, tcIsTyVarTy, tcIsForAllTy,
51 ---------------------------------
52 -- Misc type manipulators
53 hoistForAllTys, deNoteType,
54 namesOfType, namesOfDFunHead,
57 ---------------------------------
59 PredType, getClassPredTys_maybe, getClassPredTys,
60 isPredTy, isClassPred, isTyVarClassPred, predHasFDs,
61 mkDictTy, tcSplitPredTy_maybe, predTyUnique,
62 isDictTy, tcSplitDFunTy, predTyUnique,
63 mkClassPred, isInheritablePred, isLinearPred, isIPPred, mkPredName,
65 ---------------------------------
66 -- Foreign import and export
67 isFFIArgumentTy, -- :: DynFlags -> Safety -> Type -> Bool
68 isFFIImportResultTy, -- :: DynFlags -> Type -> Bool
69 isFFIExportResultTy, -- :: Type -> Bool
70 isFFIExternalTy, -- :: Type -> Bool
71 isFFIDynArgumentTy, -- :: Type -> Bool
72 isFFIDynResultTy, -- :: Type -> Bool
73 isFFILabelTy, -- :: Type -> Bool
75 ---------------------------------
76 -- Unifier and matcher
77 unifyTysX, unifyTyListsX, unifyExtendTysX,
78 matchTy, matchTys, match,
80 --------------------------------
81 -- Rexported from Type
82 Kind, -- Stuff to do with kinds is insensitive to pre/post Tc
83 unliftedTypeKind, liftedTypeKind, openTypeKind, mkArrowKind, mkArrowKinds,
84 superBoxity, liftedBoxity, hasMoreBoxityInfo, defaultKind, superKind,
85 isTypeKind, isAnyTypeKind,
87 Type, SourceType(..), PredType, ThetaType,
88 mkForAllTy, mkForAllTys,
89 mkFunTy, mkFunTys, zipFunTys,
90 mkTyConApp, mkAppTy, mkAppTys, mkSynTy, applyTy, applyTys,
91 mkTyVarTy, mkTyVarTys, mkTyConTy, mkPredTy, mkPredTys,
93 isUnLiftedType, -- Source types are always lifted
94 isUnboxedTupleType, -- Ditto
97 tidyTopType, tidyType, tidyPred, tidyTypes, tidyFreeTyVars, tidyOpenType, tidyOpenTypes,
98 tidyTyVarBndr, tidyOpenTyVar, tidyOpenTyVars,
99 typeKind, eqKind, eqUsage,
101 tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tyVarsOfTheta
104 #include "HsVersions.h"
107 import {-# SOURCE #-} PprType( pprType )
110 import TypeRep ( Type(..), TyNote(..), funTyCon ) -- friend
112 import Type ( -- Re-exports
113 tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tyVarsOfTheta,
114 Kind, Type, SourceType(..), PredType, ThetaType,
115 unliftedTypeKind, liftedTypeKind, openTypeKind, mkArrowKind, mkArrowKinds,
116 mkForAllTy, mkForAllTys, defaultKind, isTypeKind, isAnyTypeKind,
117 mkFunTy, mkFunTys, zipFunTys,
118 mkTyConApp, mkAppTy, mkAppTys, mkSynTy, applyTy, applyTys,
119 mkTyVarTy, mkTyVarTys, mkTyConTy, mkPredTy, mkPredTys,
120 isUnLiftedType, isUnboxedTupleType, isPrimitiveType,
121 splitNewType_maybe, splitTyConApp_maybe,
122 tidyTopType, tidyType, tidyPred, tidyTypes, tidyFreeTyVars, tidyOpenType, tidyOpenTypes,
123 tidyTyVarBndr, tidyOpenTyVar, tidyOpenTyVars, eqKind, eqUsage,
124 hasMoreBoxityInfo, liftedBoxity, superBoxity, typeKind, superKind
126 import TyCon ( TyCon, isUnLiftedTyCon )
127 import Class ( classHasFDs, Class )
128 import Var ( TyVar, tyVarKind, isMutTyVar, mutTyVarDetails )
129 import ForeignCall ( Safety, playSafe )
134 import CmdLineOpts ( DynFlags, DynFlag( Opt_GlasgowExts ), dopt )
135 import Name ( Name, NamedThing(..), mkLocalName, getSrcLoc )
136 import OccName ( OccName, mkDictOcc )
138 import PrelNames -- Lots (e.g. in isFFIArgumentTy)
139 import TysWiredIn ( ptrTyCon, funPtrTyCon, addrTyCon, unitTyCon )
140 import BasicTypes ( IPName(..), ipNameName )
141 import Unique ( Unique, Uniquable(..) )
142 import SrcLoc ( SrcLoc )
143 import Util ( cmpList, thenCmp, equalLength )
144 import Maybes ( maybeToBool, expectJust )
149 %************************************************************************
153 %************************************************************************
155 The type checker divides the generic Type world into the
156 following more structured beasts:
158 sigma ::= forall tyvars. theta => phi
159 -- A sigma type is a qualified type
161 -- Note that even if 'tyvars' is empty, theta
162 -- may not be: e.g. (?x::Int) => Int
164 -- Note that 'sigma' is in prenex form:
165 -- all the foralls are at the front.
166 -- A 'phi' type has no foralls to the right of
172 -- A 'tau' type has no quantification anywhere
173 -- Note that the args of a type constructor must be taus
175 | tycon tau_1 .. tau_n
179 -- In all cases, a (saturated) type synonym application is legal,
180 -- provided it expands to the required form.
184 type SigmaType = Type
190 type TcTyVar = TyVar -- Might be a mutable tyvar
191 type TcTyVarSet = TyVarSet
193 type TcType = Type -- A TcType can have mutable type variables
194 -- Invariant on ForAllTy in TcTypes:
196 -- a cannot occur inside a MutTyVar in T; that is,
197 -- T is "flattened" before quantifying over a
199 type TcPredType = PredType
200 type TcThetaType = ThetaType
201 type TcSigmaType = TcType
202 type TcPhiType = TcType
203 type TcTauType = TcType
208 %************************************************************************
210 \subsection{TyVarDetails}
212 %************************************************************************
214 TyVarDetails gives extra info about type variables, used during type
215 checking. It's attached to mutable type variables only.
216 It's knot-tied back to Var.lhs. There is no reason in principle
217 why Var.lhs shouldn't actually have the definition, but it "belongs" here.
221 = HoleTv -- Used *only* by the type checker when passing in a type
222 -- variable that should be side-effected to the result type.
223 -- Always has kind openTypeKind.
224 -- Never appears in types
226 | SigTv -- Introduced when instantiating a type signature,
227 -- prior to checking that the defn of a fn does
228 -- have the expected type. Should not be instantiated.
230 -- f :: forall a. a -> a
232 -- When checking e, with expected type (a->a), we
233 -- should not instantiate a
235 | ClsTv -- Scoped type variable introduced by a class decl
236 -- class C a where ...
238 | InstTv -- Ditto, but instance decl
240 | PatSigTv -- Scoped type variable, introduced by a pattern
244 | VanillaTv -- Everything else
246 isUserTyVar :: TcTyVar -> Bool -- Avoid unifying these if possible
247 isUserTyVar tv = case mutTyVarDetails tv of
251 isSkolemTyVar :: TcTyVar -> Bool
252 isSkolemTyVar tv = case mutTyVarDetails tv of
256 isHoleTyVar :: TcTyVar -> Bool
257 -- NB: the hole might be filled in by now, and this
258 -- function does not check for that
259 isHoleTyVar tv = ASSERT( isMutTyVar tv )
260 case mutTyVarDetails tv of
264 tyVarBindingInfo :: TyVar -> SDoc -- Used in checkSigTyVars
267 = sep [ptext SLIT("is bound by the") <+> details (mutTyVarDetails tv),
268 ptext SLIT("at") <+> ppr (getSrcLoc tv)]
272 details SigTv = ptext SLIT("type signature")
273 details ClsTv = ptext SLIT("class declaration")
274 details InstTv = ptext SLIT("instance declaration")
275 details PatSigTv = ptext SLIT("pattern type signature")
276 details HoleTv = ptext SLIT("//hole//") -- Should not happen
277 details VanillaTv = ptext SLIT("//vanilla//") -- Ditto
281 %************************************************************************
283 \subsection{Tau, sigma and rho}
285 %************************************************************************
288 mkSigmaTy tyvars theta tau = mkForAllTys tyvars (mkRhoTy theta tau)
290 mkRhoTy :: [SourceType] -> Type -> Type
291 mkRhoTy theta ty = foldr (\p r -> FunTy (mkPredTy p) r) ty theta
295 @isTauTy@ tests for nested for-alls.
298 isTauTy :: Type -> Bool
299 isTauTy (TyVarTy v) = True
300 isTauTy (TyConApp _ tys) = all isTauTy tys
301 isTauTy (AppTy a b) = isTauTy a && isTauTy b
302 isTauTy (FunTy a b) = isTauTy a && isTauTy b
303 isTauTy (SourceTy p) = True -- Don't look through source types
304 isTauTy (NoteTy _ ty) = isTauTy ty
305 isTauTy other = False
309 getDFunTyKey :: Type -> OccName -- Get some string from a type, to be used to
310 -- construct a dictionary function name
311 getDFunTyKey (TyVarTy tv) = getOccName tv
312 getDFunTyKey (TyConApp tc _) = getOccName tc
313 getDFunTyKey (AppTy fun _) = getDFunTyKey fun
314 getDFunTyKey (NoteTy _ t) = getDFunTyKey t
315 getDFunTyKey (FunTy arg _) = getOccName funTyCon
316 getDFunTyKey (ForAllTy _ t) = getDFunTyKey t
317 getDFunTyKey (SourceTy (NType tc _)) = getOccName tc -- Newtypes are quite reasonable
318 getDFunTyKey ty = pprPanic "getDFunTyKey" (pprType ty)
319 -- SourceTy shouldn't happen
323 %************************************************************************
325 \subsection{Expanding and splitting}
327 %************************************************************************
329 These tcSplit functions are like their non-Tc analogues, but
330 a) they do not look through newtypes
331 b) they do not look through PredTys
332 c) [future] they ignore usage-type annotations
334 However, they are non-monadic and do not follow through mutable type
335 variables. It's up to you to make sure this doesn't matter.
338 tcSplitForAllTys :: Type -> ([TyVar], Type)
339 tcSplitForAllTys ty = split ty ty []
341 split orig_ty (ForAllTy tv ty) tvs = split ty ty (tv:tvs)
342 split orig_ty (NoteTy n ty) tvs = split orig_ty ty tvs
343 split orig_ty t tvs = (reverse tvs, orig_ty)
345 tcIsForAllTy (ForAllTy tv ty) = True
346 tcIsForAllTy (NoteTy n ty) = tcIsForAllTy ty
347 tcIsForAllTy t = False
349 tcSplitRhoTy :: Type -> ([PredType], Type)
350 tcSplitRhoTy ty = split ty ty []
352 split orig_ty (FunTy arg res) ts = case tcSplitPredTy_maybe arg of
353 Just p -> split res res (p:ts)
354 Nothing -> (reverse ts, orig_ty)
355 split orig_ty (NoteTy n ty) ts = split orig_ty ty ts
356 split orig_ty ty ts = (reverse ts, orig_ty)
358 tcSplitSigmaTy ty = case tcSplitForAllTys ty of
359 (tvs, rho) -> case tcSplitRhoTy rho of
360 (theta, tau) -> (tvs, theta, tau)
362 tcTyConAppTyCon :: Type -> TyCon
363 tcTyConAppTyCon ty = fst (tcSplitTyConApp ty)
365 tcTyConAppArgs :: Type -> [Type]
366 tcTyConAppArgs ty = snd (tcSplitTyConApp ty)
368 tcSplitTyConApp :: Type -> (TyCon, [Type])
369 tcSplitTyConApp ty = case tcSplitTyConApp_maybe ty of
371 Nothing -> pprPanic "tcSplitTyConApp" (pprType ty)
373 tcSplitTyConApp_maybe :: Type -> Maybe (TyCon, [Type])
374 -- Newtypes are opaque, so they may be split
375 tcSplitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
376 tcSplitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res])
377 tcSplitTyConApp_maybe (NoteTy n ty) = tcSplitTyConApp_maybe ty
378 tcSplitTyConApp_maybe (SourceTy (NType tc tys)) = Just (tc,tys)
379 -- However, predicates are not treated
380 -- as tycon applications by the type checker
381 tcSplitTyConApp_maybe other = Nothing
383 tcSplitFunTys :: Type -> ([Type], Type)
384 tcSplitFunTys ty = case tcSplitFunTy_maybe ty of
386 Just (arg,res) -> (arg:args, res')
388 (args,res') = tcSplitFunTys res
390 tcSplitFunTy_maybe :: Type -> Maybe (Type, Type)
391 tcSplitFunTy_maybe (FunTy arg res) = Just (arg, res)
392 tcSplitFunTy_maybe (NoteTy n ty) = tcSplitFunTy_maybe ty
393 tcSplitFunTy_maybe other = Nothing
395 tcFunArgTy ty = case tcSplitFunTy_maybe ty of { Just (arg,res) -> arg }
396 tcFunResultTy ty = case tcSplitFunTy_maybe ty of { Just (arg,res) -> res }
399 tcSplitAppTy_maybe :: Type -> Maybe (Type, Type)
400 tcSplitAppTy_maybe (FunTy ty1 ty2) = Just (TyConApp funTyCon [ty1], ty2)
401 tcSplitAppTy_maybe (AppTy ty1 ty2) = Just (ty1, ty2)
402 tcSplitAppTy_maybe (NoteTy n ty) = tcSplitAppTy_maybe ty
403 tcSplitAppTy_maybe (SourceTy (NType tc tys)) = tc_split_app tc tys
404 --- Don't forget that newtype!
405 tcSplitAppTy_maybe (TyConApp tc tys) = tc_split_app tc tys
406 tcSplitAppTy_maybe other = Nothing
408 tc_split_app tc [] = Nothing
409 tc_split_app tc tys = split tys []
411 split [ty2] acc = Just (TyConApp tc (reverse acc), ty2)
412 split (ty:tys) acc = split tys (ty:acc)
414 tcSplitAppTy ty = case tcSplitAppTy_maybe ty of
416 Nothing -> pprPanic "tcSplitAppTy" (pprType ty)
418 tcGetTyVar_maybe :: Type -> Maybe TyVar
419 tcGetTyVar_maybe (TyVarTy tv) = Just tv
420 tcGetTyVar_maybe (NoteTy _ t) = tcGetTyVar_maybe t
421 tcGetTyVar_maybe other = Nothing
423 tcGetTyVar :: String -> Type -> TyVar
424 tcGetTyVar msg ty = expectJust msg (tcGetTyVar_maybe ty)
426 tcIsTyVarTy :: Type -> Bool
427 tcIsTyVarTy ty = maybeToBool (tcGetTyVar_maybe ty)
430 The type of a method for class C is always of the form:
431 Forall a1..an. C a1..an => sig_ty
432 where sig_ty is the type given by the method's signature, and thus in general
433 is a ForallTy. At the point that splitMethodTy is called, it is expected
434 that the outer Forall has already been stripped off. splitMethodTy then
435 returns (C a1..an, sig_ty') where sig_ty' is sig_ty with any Notes or
439 tcSplitMethodTy :: Type -> (PredType, Type)
440 tcSplitMethodTy ty = split ty
442 split (FunTy arg res) = case tcSplitPredTy_maybe arg of
444 Nothing -> panic "splitMethodTy"
445 split (NoteTy n ty) = split ty
446 split _ = panic "splitMethodTy"
448 tcSplitDFunTy :: Type -> ([TyVar], [SourceType], Class, [Type])
449 -- Split the type of a dictionary function
451 = case tcSplitSigmaTy ty of { (tvs, theta, tau) ->
452 case tcSplitPredTy_maybe tau of { Just (ClassP clas tys) ->
453 (tvs, theta, clas, tys) }}
456 (allDistinctTyVars tys tvs) = True
458 all the types tys are type variables,
459 distinct from each other and from tvs.
461 This is useful when checking that unification hasn't unified signature
462 type variables. For example, if the type sig is
463 f :: forall a b. a -> b -> b
464 we want to check that 'a' and 'b' havn't
465 (a) been unified with a non-tyvar type
466 (b) been unified with each other (all distinct)
467 (c) been unified with a variable free in the environment
470 allDistinctTyVars :: [Type] -> TyVarSet -> Bool
472 allDistinctTyVars [] acc
474 allDistinctTyVars (ty:tys) acc
475 = case tcGetTyVar_maybe ty of
476 Nothing -> False -- (a)
477 Just tv | tv `elemVarSet` acc -> False -- (b) or (c)
478 | otherwise -> allDistinctTyVars tys (acc `extendVarSet` tv)
482 %************************************************************************
484 \subsection{Predicate types}
486 %************************************************************************
488 "Predicates" are particular source types, namelyClassP or IParams
491 isPred :: SourceType -> Bool
492 isPred (ClassP _ _) = True
493 isPred (IParam _ _) = True
494 isPred (NType _ _) = False
496 isPredTy :: Type -> Bool
497 isPredTy (NoteTy _ ty) = isPredTy ty
498 isPredTy (SourceTy sty) = isPred sty
501 tcSplitPredTy_maybe :: Type -> Maybe PredType
502 -- Returns Just for predicates only
503 tcSplitPredTy_maybe (NoteTy _ ty) = tcSplitPredTy_maybe ty
504 tcSplitPredTy_maybe (SourceTy p) | isPred p = Just p
505 tcSplitPredTy_maybe other = Nothing
507 predTyUnique :: PredType -> Unique
508 predTyUnique (IParam n _) = getUnique (ipNameName n)
509 predTyUnique (ClassP clas tys) = getUnique clas
511 predHasFDs :: PredType -> Bool
512 -- True if the predicate has functional depenencies;
513 -- I.e. should participate in improvement
514 predHasFDs (IParam _ _) = True
515 predHasFDs (ClassP cls _) = classHasFDs cls
517 mkPredName :: Unique -> SrcLoc -> SourceType -> Name
518 mkPredName uniq loc (ClassP cls tys) = mkLocalName uniq (mkDictOcc (getOccName cls)) loc
519 mkPredName uniq loc (IParam ip ty) = mkLocalName uniq (getOccName (ipNameName ip)) loc
523 --------------------- Dictionary types ---------------------------------
526 mkClassPred clas tys = ClassP clas tys
528 isClassPred :: SourceType -> Bool
529 isClassPred (ClassP clas tys) = True
530 isClassPred other = False
532 isTyVarClassPred (ClassP clas tys) = all tcIsTyVarTy tys
533 isTyVarClassPred other = False
535 getClassPredTys_maybe :: SourceType -> Maybe (Class, [Type])
536 getClassPredTys_maybe (ClassP clas tys) = Just (clas, tys)
537 getClassPredTys_maybe _ = Nothing
539 getClassPredTys :: PredType -> (Class, [Type])
540 getClassPredTys (ClassP clas tys) = (clas, tys)
542 mkDictTy :: Class -> [Type] -> Type
543 mkDictTy clas tys = mkPredTy (ClassP clas tys)
545 isDictTy :: Type -> Bool
546 isDictTy (SourceTy p) = isClassPred p
547 isDictTy (NoteTy _ ty) = isDictTy ty
548 isDictTy other = False
551 --------------------- Implicit parameters ---------------------------------
554 isIPPred :: SourceType -> Bool
555 isIPPred (IParam _ _) = True
556 isIPPred other = False
558 isInheritablePred :: PredType -> Bool
559 -- Can be inherited by a context. For example, consider
560 -- f x = let g y = (?v, y+x)
561 -- in (g 3 with ?v = 8,
563 -- The point is that g's type must be quantifed over ?v:
564 -- g :: (?v :: a) => a -> a
565 -- but it doesn't need to be quantified over the Num a dictionary
566 -- which can be free in g's rhs, and shared by both calls to g
567 isInheritablePred (ClassP _ _) = True
568 isInheritablePred other = False
570 isLinearPred :: TcPredType -> Bool
571 isLinearPred (IParam (Linear n) _) = True
572 isLinearPred other = False
576 %************************************************************************
578 \subsection{Comparison}
580 %************************************************************************
582 Comparison, taking note of newtypes, predicates, etc,
583 But ignoring usage types
586 tcEqType :: Type -> Type -> Bool
587 tcEqType ty1 ty2 = case ty1 `tcCmpType` ty2 of { EQ -> True; other -> False }
589 tcEqTypes :: [Type] -> [Type] -> Bool
590 tcEqTypes ty1 ty2 = case ty1 `tcCmpTypes` ty2 of { EQ -> True; other -> False }
592 tcEqPred :: PredType -> PredType -> Bool
593 tcEqPred p1 p2 = case p1 `tcCmpPred` p2 of { EQ -> True; other -> False }
596 tcCmpType :: Type -> Type -> Ordering
597 tcCmpType ty1 ty2 = cmpTy emptyVarEnv ty1 ty2
599 tcCmpTypes tys1 tys2 = cmpTys emptyVarEnv tys1 tys2
601 tcCmpPred p1 p2 = cmpSourceTy emptyVarEnv p1 p2
603 cmpTys env tys1 tys2 = cmpList (cmpTy env) tys1 tys2
606 cmpTy :: TyVarEnv TyVar -> Type -> Type -> Ordering
607 -- The "env" maps type variables in ty1 to type variables in ty2
608 -- So when comparing for-alls.. (forall tv1 . t1) (forall tv2 . t2)
609 -- we in effect substitute tv2 for tv1 in t1 before continuing
611 -- Look through NoteTy
612 cmpTy env (NoteTy _ ty1) ty2 = cmpTy env ty1 ty2
613 cmpTy env ty1 (NoteTy _ ty2) = cmpTy env ty1 ty2
615 -- Deal with equal constructors
616 cmpTy env (TyVarTy tv1) (TyVarTy tv2) = case lookupVarEnv env tv1 of
617 Just tv1a -> tv1a `compare` tv2
618 Nothing -> tv1 `compare` tv2
620 cmpTy env (SourceTy p1) (SourceTy p2) = cmpSourceTy env p1 p2
621 cmpTy env (AppTy f1 a1) (AppTy f2 a2) = cmpTy env f1 f2 `thenCmp` cmpTy env a1 a2
622 cmpTy env (FunTy f1 a1) (FunTy f2 a2) = cmpTy env f1 f2 `thenCmp` cmpTy env a1 a2
623 cmpTy env (TyConApp tc1 tys1) (TyConApp tc2 tys2) = (tc1 `compare` tc2) `thenCmp` (cmpTys env tys1 tys2)
624 cmpTy env (ForAllTy tv1 t1) (ForAllTy tv2 t2) = cmpTy (extendVarEnv env tv1 tv2) t1 t2
626 -- Deal with the rest: TyVarTy < AppTy < FunTy < TyConApp < ForAllTy < SourceTy
627 cmpTy env (AppTy _ _) (TyVarTy _) = GT
629 cmpTy env (FunTy _ _) (TyVarTy _) = GT
630 cmpTy env (FunTy _ _) (AppTy _ _) = GT
632 cmpTy env (TyConApp _ _) (TyVarTy _) = GT
633 cmpTy env (TyConApp _ _) (AppTy _ _) = GT
634 cmpTy env (TyConApp _ _) (FunTy _ _) = GT
636 cmpTy env (ForAllTy _ _) (TyVarTy _) = GT
637 cmpTy env (ForAllTy _ _) (AppTy _ _) = GT
638 cmpTy env (ForAllTy _ _) (FunTy _ _) = GT
639 cmpTy env (ForAllTy _ _) (TyConApp _ _) = GT
641 cmpTy env (SourceTy _) t2 = GT
647 cmpSourceTy :: TyVarEnv TyVar -> SourceType -> SourceType -> Ordering
648 cmpSourceTy env (IParam n1 ty1) (IParam n2 ty2) = (n1 `compare` n2) `thenCmp` (cmpTy env ty1 ty2)
649 -- Compare types as well as names for implicit parameters
650 -- This comparison is used exclusively (I think) for the
651 -- finite map built in TcSimplify
652 cmpSourceTy env (IParam _ _) sty = LT
654 cmpSourceTy env (ClassP _ _) (IParam _ _) = GT
655 cmpSourceTy env (ClassP c1 tys1) (ClassP c2 tys2) = (c1 `compare` c2) `thenCmp` (cmpTys env tys1 tys2)
656 cmpSourceTy env (ClassP _ _) (NType _ _) = LT
658 cmpSourceTy env (NType tc1 tys1) (NType tc2 tys2) = (tc1 `compare` tc2) `thenCmp` (cmpTys env tys1 tys2)
659 cmpSourceTy env (NType _ _) sty = GT
662 PredTypes are used as a FM key in TcSimplify,
663 so we take the easy path and make them an instance of Ord
666 instance Eq SourceType where { (==) = tcEqPred }
667 instance Ord SourceType where { compare = tcCmpPred }
671 %************************************************************************
673 \subsection{Predicates}
675 %************************************************************************
677 isSigmaTy returns true of any qualified type. It doesn't *necessarily* have
679 f :: (?x::Int) => Int -> Int
682 isSigmaTy :: Type -> Bool
683 isSigmaTy (ForAllTy tyvar ty) = True
684 isSigmaTy (FunTy a b) = isPredTy a
685 isSigmaTy (NoteTy n ty) = isSigmaTy ty
688 isOverloadedTy :: Type -> Bool
689 isOverloadedTy (ForAllTy tyvar ty) = isOverloadedTy ty
690 isOverloadedTy (FunTy a b) = isPredTy a
691 isOverloadedTy (NoteTy n ty) = isOverloadedTy ty
692 isOverloadedTy _ = False
696 isFloatTy = is_tc floatTyConKey
697 isDoubleTy = is_tc doubleTyConKey
698 isForeignPtrTy = is_tc foreignPtrTyConKey
699 isIntegerTy = is_tc integerTyConKey
700 isIntTy = is_tc intTyConKey
701 isAddrTy = is_tc addrTyConKey
702 isBoolTy = is_tc boolTyConKey
703 isUnitTy = is_tc unitTyConKey
705 is_tc :: Unique -> Type -> Bool
706 -- Newtypes are opaque to this
707 is_tc uniq ty = case tcSplitTyConApp_maybe ty of
708 Just (tc, _) -> uniq == getUnique tc
713 %************************************************************************
717 %************************************************************************
720 hoistForAllTys :: Type -> Type
721 -- Used for user-written type signatures only
722 -- Move all the foralls and constraints to the top
723 -- e.g. T -> forall a. a ==> forall a. T -> a
724 -- T -> (?x::Int) -> Int ==> (?x::Int) -> T -> Int
726 -- We want to 'look through' type synonyms when doing this
727 -- so it's better done on the Type than the HsType
730 = case hoist ty ty of
731 (tvs, theta, body) -> mkForAllTys tvs (mkFunTys theta body)
733 hoist orig_ty (ForAllTy tv ty) = case hoist ty ty of
734 (tvs,theta,tau) -> (tv:tvs,theta,tau)
735 hoist orig_ty (FunTy arg res)
736 | isPredTy arg = case hoist res res of
737 (tvs,theta,tau) -> (tvs,arg:theta,tau)
738 | otherwise = case hoist res res of
739 (tvs,theta,tau) -> (tvs,theta,mkFunTy arg tau)
741 hoist orig_ty (NoteTy _ ty) = hoist orig_ty ty
742 hoist orig_ty ty = ([], [], orig_ty)
747 deNoteType :: Type -> Type
748 -- Remove synonyms, but not source types
749 deNoteType ty@(TyVarTy tyvar) = ty
750 deNoteType (TyConApp tycon tys) = TyConApp tycon (map deNoteType tys)
751 deNoteType (SourceTy p) = SourceTy (deNoteSourceType p)
752 deNoteType (NoteTy _ ty) = deNoteType ty
753 deNoteType (AppTy fun arg) = AppTy (deNoteType fun) (deNoteType arg)
754 deNoteType (FunTy fun arg) = FunTy (deNoteType fun) (deNoteType arg)
755 deNoteType (ForAllTy tv ty) = ForAllTy tv (deNoteType ty)
757 deNoteSourceType :: SourceType -> SourceType
758 deNoteSourceType (ClassP c tys) = ClassP c (map deNoteType tys)
759 deNoteSourceType (IParam n ty) = IParam n (deNoteType ty)
760 deNoteSourceType (NType tc tys) = NType tc (map deNoteType tys)
763 Find the free names of a type, including the type constructors and classes it mentions
764 This is used in the front end of the compiler
767 namesOfType :: Type -> NameSet
768 namesOfType (TyVarTy tv) = unitNameSet (getName tv)
769 namesOfType (TyConApp tycon tys) = unitNameSet (getName tycon) `unionNameSets` namesOfTypes tys
770 namesOfType (NoteTy (SynNote ty1) ty2) = namesOfType ty1
771 namesOfType (NoteTy other_note ty2) = namesOfType ty2
772 namesOfType (SourceTy (IParam n ty)) = namesOfType ty
773 namesOfType (SourceTy (ClassP cl tys)) = unitNameSet (getName cl) `unionNameSets` namesOfTypes tys
774 namesOfType (SourceTy (NType tc tys)) = unitNameSet (getName tc) `unionNameSets` namesOfTypes tys
775 namesOfType (FunTy arg res) = namesOfType arg `unionNameSets` namesOfType res
776 namesOfType (AppTy fun arg) = namesOfType fun `unionNameSets` namesOfType arg
777 namesOfType (ForAllTy tyvar ty) = namesOfType ty `delFromNameSet` getName tyvar
779 namesOfTypes tys = foldr (unionNameSets . namesOfType) emptyNameSet tys
781 namesOfDFunHead :: Type -> NameSet
782 -- Find the free type constructors and classes
783 -- of the head of the dfun instance type
784 -- The 'dfun_head_type' is because of
785 -- instance Foo a => Baz T where ...
786 -- The decl is an orphan if Baz and T are both not locally defined,
787 -- even if Foo *is* locally defined
788 namesOfDFunHead dfun_ty = case tcSplitSigmaTy dfun_ty of
789 (tvs,_,head_ty) -> delListFromNameSet (namesOfType head_ty)
794 %************************************************************************
796 \subsection[TysWiredIn-ext-type]{External types}
798 %************************************************************************
800 The compiler's foreign function interface supports the passing of a
801 restricted set of types as arguments and results (the restricting factor
805 isFFIArgumentTy :: DynFlags -> Safety -> Type -> Bool
806 -- Checks for valid argument type for a 'foreign import'
807 isFFIArgumentTy dflags safety ty
808 = checkRepTyCon (legalOutgoingTyCon dflags safety) ty
810 isFFIExternalTy :: Type -> Bool
811 -- Types that are allowed as arguments of a 'foreign export'
812 isFFIExternalTy ty = checkRepTyCon legalFEArgTyCon ty
814 isFFIImportResultTy :: DynFlags -> Type -> Bool
815 isFFIImportResultTy dflags ty
816 = checkRepTyCon (legalFIResultTyCon dflags) ty
818 isFFIExportResultTy :: Type -> Bool
819 isFFIExportResultTy ty = checkRepTyCon legalFEResultTyCon ty
821 isFFIDynArgumentTy :: Type -> Bool
822 -- The argument type of a foreign import dynamic must be Ptr, FunPtr, Addr,
823 -- or a newtype of either.
824 isFFIDynArgumentTy = checkRepTyCon (\tc -> tc == ptrTyCon || tc == funPtrTyCon || tc == addrTyCon)
826 isFFIDynResultTy :: Type -> Bool
827 -- The result type of a foreign export dynamic must be Ptr, FunPtr, Addr,
828 -- or a newtype of either.
829 isFFIDynResultTy = checkRepTyCon (\tc -> tc == ptrTyCon || tc == funPtrTyCon || tc == addrTyCon)
831 isFFILabelTy :: Type -> Bool
832 -- The type of a foreign label must be Ptr, FunPtr, Addr,
833 -- or a newtype of either.
834 isFFILabelTy = checkRepTyCon (\tc -> tc == ptrTyCon || tc == funPtrTyCon || tc == addrTyCon)
836 checkRepTyCon :: (TyCon -> Bool) -> Type -> Bool
837 -- Look through newtypes
838 -- Non-recursive ones are transparent to splitTyConApp,
839 -- but recursive ones aren't; hence the splitNewType_maybe
840 checkRepTyCon check_tc ty
841 | Just ty' <- splitNewType_maybe ty = checkRepTyCon check_tc ty'
842 | Just (tc,_) <- splitTyConApp_maybe ty = check_tc tc
846 ----------------------------------------------
847 These chaps do the work; they are not exported
848 ----------------------------------------------
851 legalFEArgTyCon :: TyCon -> Bool
852 -- It's illegal to return foreign objects and (mutable)
853 -- bytearrays from a _ccall_ / foreign declaration
854 -- (or be passed them as arguments in foreign exported functions).
856 | getUnique tc `elem` [ foreignObjTyConKey, foreignPtrTyConKey,
857 byteArrayTyConKey, mutableByteArrayTyConKey ]
859 -- It's also illegal to make foreign exports that take unboxed
860 -- arguments. The RTS API currently can't invoke such things. --SDM 7/2000
862 = boxedMarshalableTyCon tc
864 legalFIResultTyCon :: DynFlags -> TyCon -> Bool
865 legalFIResultTyCon dflags tc
866 | getUnique tc `elem`
867 [ foreignObjTyConKey, foreignPtrTyConKey,
868 byteArrayTyConKey, mutableByteArrayTyConKey ] = False
869 | tc == unitTyCon = True
870 | otherwise = marshalableTyCon dflags tc
872 legalFEResultTyCon :: TyCon -> Bool
873 legalFEResultTyCon tc
874 | getUnique tc `elem`
875 [ foreignObjTyConKey, foreignPtrTyConKey,
876 byteArrayTyConKey, mutableByteArrayTyConKey ] = False
877 | tc == unitTyCon = True
878 | otherwise = boxedMarshalableTyCon tc
880 legalOutgoingTyCon :: DynFlags -> Safety -> TyCon -> Bool
881 -- Checks validity of types going from Haskell -> external world
882 legalOutgoingTyCon dflags safety tc
883 | playSafe safety && getUnique tc `elem` [byteArrayTyConKey, mutableByteArrayTyConKey]
886 = marshalableTyCon dflags tc
888 marshalableTyCon dflags tc
889 = (dopt Opt_GlasgowExts dflags && isUnLiftedTyCon tc)
890 || boxedMarshalableTyCon tc
892 boxedMarshalableTyCon tc
893 = getUnique tc `elem` [ intTyConKey, int8TyConKey, int16TyConKey
894 , int32TyConKey, int64TyConKey
895 , wordTyConKey, word8TyConKey, word16TyConKey
896 , word32TyConKey, word64TyConKey
897 , floatTyConKey, doubleTyConKey
898 , addrTyConKey, ptrTyConKey, funPtrTyConKey
899 , charTyConKey, foreignObjTyConKey
902 , byteArrayTyConKey, mutableByteArrayTyConKey
908 %************************************************************************
910 \subsection{Unification with an explicit substitution}
912 %************************************************************************
914 Unify types with an explicit substitution and no monad.
915 Ignore usage annotations.
919 = (TyVarSet, -- Set of template tyvars
920 TyVarSubstEnv) -- Not necessarily idempotent
922 unifyTysX :: TyVarSet -- Template tyvars
925 -> Maybe TyVarSubstEnv
926 unifyTysX tmpl_tyvars ty1 ty2
927 = uTysX ty1 ty2 (\(_,s) -> Just s) (tmpl_tyvars, emptySubstEnv)
929 unifyExtendTysX :: TyVarSet -- Template tyvars
930 -> TyVarSubstEnv -- Substitution to start with
933 -> Maybe TyVarSubstEnv -- Extended substitution
934 unifyExtendTysX tmpl_tyvars subst ty1 ty2
935 = uTysX ty1 ty2 (\(_,s) -> Just s) (tmpl_tyvars, subst)
937 unifyTyListsX :: TyVarSet -> [Type] -> [Type]
938 -> Maybe TyVarSubstEnv
939 unifyTyListsX tmpl_tyvars tys1 tys2
940 = uTyListsX tys1 tys2 (\(_,s) -> Just s) (tmpl_tyvars, emptySubstEnv)
945 -> (MySubst -> Maybe result)
949 uTysX (NoteTy _ ty1) ty2 k subst = uTysX ty1 ty2 k subst
950 uTysX ty1 (NoteTy _ ty2) k subst = uTysX ty1 ty2 k subst
952 -- Variables; go for uVar
953 uTysX (TyVarTy tyvar1) (TyVarTy tyvar2) k subst
956 uTysX (TyVarTy tyvar1) ty2 k subst@(tmpls,_)
957 | tyvar1 `elemVarSet` tmpls
958 = uVarX tyvar1 ty2 k subst
959 uTysX ty1 (TyVarTy tyvar2) k subst@(tmpls,_)
960 | tyvar2 `elemVarSet` tmpls
961 = uVarX tyvar2 ty1 k subst
964 uTysX (SourceTy (IParam n1 t1)) (SourceTy (IParam n2 t2)) k subst
965 | n1 == n2 = uTysX t1 t2 k subst
966 uTysX (SourceTy (ClassP c1 tys1)) (SourceTy (ClassP c2 tys2)) k subst
967 | c1 == c2 = uTyListsX tys1 tys2 k subst
968 uTysX (SourceTy (NType tc1 tys1)) (SourceTy (NType tc2 tys2)) k subst
969 | tc1 == tc2 = uTyListsX tys1 tys2 k subst
971 -- Functions; just check the two parts
972 uTysX (FunTy fun1 arg1) (FunTy fun2 arg2) k subst
973 = uTysX fun1 fun2 (uTysX arg1 arg2 k) subst
975 -- Type constructors must match
976 uTysX (TyConApp con1 tys1) (TyConApp con2 tys2) k subst
977 | (con1 == con2 && equalLength tys1 tys2)
978 = uTyListsX tys1 tys2 k subst
980 -- Applications need a bit of care!
981 -- They can match FunTy and TyConApp, so use splitAppTy_maybe
982 -- NB: we've already dealt with type variables and Notes,
983 -- so if one type is an App the other one jolly well better be too
984 uTysX (AppTy s1 t1) ty2 k subst
985 = case tcSplitAppTy_maybe ty2 of
986 Just (s2, t2) -> uTysX s1 s2 (uTysX t1 t2 k) subst
987 Nothing -> Nothing -- Fail
989 uTysX ty1 (AppTy s2 t2) k subst
990 = case tcSplitAppTy_maybe ty1 of
991 Just (s1, t1) -> uTysX s1 s2 (uTysX t1 t2 k) subst
992 Nothing -> Nothing -- Fail
994 -- Not expecting for-alls in unification
996 uTysX (ForAllTy _ _) ty2 k subst = panic "Unify.uTysX subst:ForAllTy (1st arg)"
997 uTysX ty1 (ForAllTy _ _) k subst = panic "Unify.uTysX subst:ForAllTy (2nd arg)"
1000 -- Anything else fails
1001 uTysX ty1 ty2 k subst = Nothing
1004 uTyListsX [] [] k subst = k subst
1005 uTyListsX (ty1:tys1) (ty2:tys2) k subst = uTysX ty1 ty2 (uTyListsX tys1 tys2 k) subst
1006 uTyListsX tys1 tys2 k subst = Nothing -- Fail if the lists are different lengths
1010 -- Invariant: tv1 is a unifiable variable
1011 uVarX tv1 ty2 k subst@(tmpls, env)
1012 = case lookupSubstEnv env tv1 of
1013 Just (DoneTy ty1) -> -- Already bound
1014 uTysX ty1 ty2 k subst
1016 Nothing -- Not already bound
1017 | typeKind ty2 `eqKind` tyVarKind tv1
1018 && occur_check_ok ty2
1019 -> -- No kind mismatch nor occur check
1020 k (tmpls, extendSubstEnv env tv1 (DoneTy ty2))
1022 | otherwise -> Nothing -- Fail if kind mis-match or occur check
1024 occur_check_ok ty = all occur_check_ok_tv (varSetElems (tyVarsOfType ty))
1025 occur_check_ok_tv tv | tv1 == tv = False
1026 | otherwise = case lookupSubstEnv env tv of
1028 Just (DoneTy ty) -> occur_check_ok ty
1033 %************************************************************************
1035 \subsection{Matching on types}
1037 %************************************************************************
1039 Matching is a {\em unidirectional} process, matching a type against a
1040 template (which is just a type with type variables in it). The
1041 matcher assumes that there are no repeated type variables in the
1042 template, so that it simply returns a mapping of type variables to
1043 types. It also fails on nested foralls.
1045 @matchTys@ matches corresponding elements of a list of templates and
1046 types. It and @matchTy@ both ignore usage annotations, unlike the
1047 main function @match@.
1050 matchTy :: TyVarSet -- Template tyvars
1052 -> Type -- Proposed instance of template
1053 -> Maybe TyVarSubstEnv -- Matching substitution
1056 matchTys :: TyVarSet -- Template tyvars
1057 -> [Type] -- Templates
1058 -> [Type] -- Proposed instance of template
1059 -> Maybe (TyVarSubstEnv, -- Matching substitution
1060 [Type]) -- Left over instance types
1062 matchTy tmpls ty1 ty2 = match ty1 ty2 tmpls (\ senv -> Just senv) emptySubstEnv
1064 matchTys tmpls tys1 tys2 = match_list tys1 tys2 tmpls
1065 (\ (senv,tys) -> Just (senv,tys))
1069 @match@ is the main function. It takes a flag indicating whether
1070 usage annotations are to be respected.
1073 match :: Type -> Type -- Current match pair
1074 -> TyVarSet -- Template vars
1075 -> (TyVarSubstEnv -> Maybe result) -- Continuation
1076 -> TyVarSubstEnv -- Current subst
1079 -- When matching against a type variable, see if the variable
1080 -- has already been bound. If so, check that what it's bound to
1081 -- is the same as ty; if not, bind it and carry on.
1083 match (TyVarTy v) ty tmpls k senv
1084 | v `elemVarSet` tmpls
1085 = -- v is a template variable
1086 case lookupSubstEnv senv v of
1087 Nothing | typeKind ty `eqKind` tyVarKind v
1088 -- We do a kind check, just as in the uVarX above
1089 -- The kind check is needed to avoid bogus matches
1090 -- of (a b) with (c d), where the kinds don't match
1091 -- An occur check isn't needed when matching.
1092 -> k (extendSubstEnv senv v (DoneTy ty))
1094 | otherwise -> Nothing -- Fails
1096 Just (DoneTy ty') | ty' `tcEqType` ty -> k senv -- Succeeds
1097 | otherwise -> Nothing -- Fails
1100 = -- v is not a template variable; ty had better match
1101 -- Can't use (==) because types differ
1102 case tcGetTyVar_maybe ty of
1103 Just v' | v == v' -> k senv -- Success
1104 other -> Nothing -- Failure
1105 -- This tcGetTyVar_maybe is *required* because it must strip Notes.
1106 -- I guess the reason the Note-stripping case is *last* rather than first
1107 -- is to preserve type synonyms etc., so I'm not moving it to the
1108 -- top; but this means that (without the deNotetype) a type
1109 -- variable may not match the pattern (TyVarTy v') as one would
1110 -- expect, due to an intervening Note. KSW 2000-06.
1113 match (SourceTy (IParam n1 t1)) (SourceTy (IParam n2 t2)) tmpls k senv
1114 | n1 == n2 = match t1 t2 tmpls k senv
1115 match (SourceTy (ClassP c1 tys1)) (SourceTy (ClassP c2 tys2)) tmpls k senv
1116 | c1 == c2 = match_list_exactly tys1 tys2 tmpls k senv
1117 match (SourceTy (NType tc1 tys1)) (SourceTy (NType tc2 tys2)) tmpls k senv
1118 | tc1 == tc2 = match_list_exactly tys1 tys2 tmpls k senv
1120 -- Functions; just check the two parts
1121 match (FunTy arg1 res1) (FunTy arg2 res2) tmpls k senv
1122 = match arg1 arg2 tmpls (match res1 res2 tmpls k) senv
1124 match (AppTy fun1 arg1) ty2 tmpls k senv
1125 = case tcSplitAppTy_maybe ty2 of
1126 Just (fun2,arg2) -> match fun1 fun2 tmpls (match arg1 arg2 tmpls k) senv
1127 Nothing -> Nothing -- Fail
1129 match (TyConApp tc1 tys1) (TyConApp tc2 tys2) tmpls k senv
1130 | tc1 == tc2 = match_list_exactly tys1 tys2 tmpls k senv
1132 -- Newtypes are opaque; other source types should not happen
1133 match (SourceTy (NType tc1 tys1)) (SourceTy (NType tc2 tys2)) tmpls k senv
1134 | tc1 == tc2 = match_list_exactly tys1 tys2 tmpls k senv
1136 -- With type synonyms, we have to be careful for the exact
1137 -- same reasons as in the unifier. Please see the
1138 -- considerable commentary there before changing anything
1139 -- here! (WDP 95/05)
1140 match (NoteTy n1 ty1) ty2 tmpls k senv = match ty1 ty2 tmpls k senv
1141 match ty1 (NoteTy n2 ty2) tmpls k senv = match ty1 ty2 tmpls k senv
1144 match _ _ _ _ _ = Nothing
1146 match_list_exactly tys1 tys2 tmpls k senv
1147 = match_list tys1 tys2 tmpls k' senv
1149 k' (senv', tys2') | null tys2' = k senv' -- Succeed
1150 | otherwise = Nothing -- Fail
1152 match_list [] tys2 tmpls k senv = k (senv, tys2)
1153 match_list (ty1:tys1) [] tmpls k senv = Nothing -- Not enough arg tys => failure
1154 match_list (ty1:tys1) (ty2:tys2) tmpls k senv
1155 = match ty1 ty2 tmpls (match_list tys1 tys2 tmpls k) senv