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, TcRhoType, TcTauType, TcPredType, TcThetaType,
21 TcTyVar, TcTyVarSet, TcKind,
23 --------------------------------
25 TyVarDetails(..), isUserTyVar, isSkolemTyVar,
28 --------------------------------
32 --------------------------------
34 -- These are important because they do not look through newtypes
35 tcSplitForAllTys, tcSplitPhiTy,
36 tcSplitFunTy_maybe, tcSplitFunTys, tcFunArgTy, tcFunResultTy,
37 tcSplitTyConApp, tcSplitTyConApp_maybe, tcTyConAppTyCon, tcTyConAppArgs,
38 tcSplitAppTy_maybe, tcSplitAppTy, tcSplitAppTys, 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,
48 isTauTy, tcIsTyVarTy, tcIsForAllTy,
51 ---------------------------------
52 -- Misc type manipulators
53 deNoteType, classesOfTheta,
54 tyClsNamesOfType, tyClsNamesOfDFunHead,
57 ---------------------------------
59 getClassPredTys_maybe, getClassPredTys,
60 isClassPred, isTyVarClassPred,
61 mkDictTy, tcSplitPredTy_maybe,
62 isPredTy, 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
74 isFFIDotnetTy, -- :: DynFlags -> Type -> Bool
75 isFFIDotnetObjTy, -- :: Type -> Bool
77 toDNType, -- :: Type -> DNType
79 ---------------------------------
80 -- Unifier and matcher
81 unifyTysX, unifyTyListsX, unifyExtendTysX,
82 matchTy, matchTys, match,
84 --------------------------------
85 -- Rexported from Type
86 Kind, -- Stuff to do with kinds is insensitive to pre/post Tc
87 unliftedTypeKind, liftedTypeKind, openTypeKind, mkArrowKind, mkArrowKinds,
88 superBoxity, liftedBoxity, hasMoreBoxityInfo, defaultKind, superKind,
89 isTypeKind, isAnyTypeKind,
91 Type, PredType(..), ThetaType,
92 mkForAllTy, mkForAllTys,
93 mkFunTy, mkFunTys, zipFunTys,
94 mkTyConApp, mkGenTyConApp, mkAppTy, mkAppTys, mkSynTy, applyTy, applyTys,
95 mkTyVarTy, mkTyVarTys, mkTyConTy, mkPredTy, mkPredTys,
97 isUnLiftedType, -- Source types are always lifted
98 isUnboxedTupleType, -- Ditto
101 tidyTopType, tidyType, tidyPred, tidyTypes, tidyFreeTyVars, tidyOpenType, tidyOpenTypes,
102 tidyTyVarBndr, tidyOpenTyVar, tidyOpenTyVars,
105 tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tyVarsOfTheta
108 #include "HsVersions.h"
111 import {-# SOURCE #-} PprType( pprType )
112 -- PprType imports TcType so that it can print intelligently
115 import TypeRep ( Type(..), TyNote(..), funTyCon ) -- friend
117 import Type ( -- Re-exports
118 tyVarsOfType, tyVarsOfTypes, tyVarsOfPred,
119 tyVarsOfTheta, Kind, Type, PredType(..),
120 ThetaType, unliftedTypeKind,
121 liftedTypeKind, openTypeKind, mkArrowKind,
122 mkArrowKinds, mkForAllTy, mkForAllTys,
123 defaultKind, isTypeKind, isAnyTypeKind,
124 mkFunTy, mkFunTys, zipFunTys, isTyVarTy,
125 mkTyConApp, mkGenTyConApp, mkAppTy,
126 mkAppTys, mkSynTy, applyTy, applyTys,
127 mkTyVarTy, mkTyVarTys, mkTyConTy, mkPredTy,
128 mkPredTys, isUnLiftedType,
129 isUnboxedTupleType, isPrimitiveType,
131 tidyTopType, tidyType, tidyPred, tidyTypes,
132 tidyFreeTyVars, tidyOpenType, tidyOpenTypes,
133 tidyTyVarBndr, tidyOpenTyVar,
134 tidyOpenTyVars, eqKind,
135 hasMoreBoxityInfo, liftedBoxity,
136 superBoxity, typeKind, superKind, repType
138 import TyCon ( TyCon, isUnLiftedTyCon, tyConUnique )
139 import Class ( Class )
140 import Var ( TyVar, tyVarKind, isMutTyVar, mutTyVarDetails )
141 import ForeignCall ( Safety, playSafe
148 import CmdLineOpts ( DynFlags, DynFlag( Opt_GlasgowExts ), dopt )
149 import Name ( Name, NamedThing(..), mkInternalName, getSrcLoc )
151 import OccName ( OccName, mkDictOcc )
152 import PrelNames -- Lots (e.g. in isFFIArgumentTy)
153 import TysWiredIn ( unitTyCon, charTyCon, listTyCon )
154 import BasicTypes ( IPName(..), ipNameName )
155 import Unique ( Unique, Uniquable(..) )
156 import SrcLoc ( SrcLoc )
157 import Util ( cmpList, thenCmp, equalLength, snocView )
158 import Maybes ( maybeToBool, expectJust )
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 -- Might be a mutable tyvar
200 type TcTyVarSet = TyVarSet
202 type TcType = Type -- A TcType can have mutable type variables
203 -- Invariant on ForAllTy in TcTypes:
205 -- a cannot occur inside a MutTyVar in T; that is,
206 -- T is "flattened" before quantifying over a
208 type TcPredType = PredType
209 type TcThetaType = ThetaType
210 type TcSigmaType = TcType
211 type TcRhoType = TcType
212 type TcTauType = TcType
217 %************************************************************************
219 \subsection{TyVarDetails}
221 %************************************************************************
223 TyVarDetails gives extra info about type variables, used during type
224 checking. It's attached to mutable type variables only.
225 It's knot-tied back to Var.lhs. There is no reason in principle
226 why Var.lhs shouldn't actually have the definition, but it "belongs" here.
230 = SigTv -- Introduced when instantiating a type signature,
231 -- prior to checking that the defn of a fn does
232 -- have the expected type. Should not be instantiated.
234 -- f :: forall a. a -> a
236 -- When checking e, with expected type (a->a), we
237 -- should not instantiate a
239 | ClsTv -- Scoped type variable introduced by a class decl
240 -- class C a where ...
242 | InstTv -- Ditto, but instance decl
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
258 tyVarBindingInfo :: TyVar -> SDoc -- Used in checkSigTyVars
261 = sep [ptext SLIT("is bound by the") <+> details (mutTyVarDetails tv),
262 ptext SLIT("at") <+> ppr (getSrcLoc tv)]
266 details SigTv = ptext SLIT("type signature")
267 details ClsTv = ptext SLIT("class declaration")
268 details InstTv = ptext SLIT("instance declaration")
269 details VanillaTv = ptext SLIT("//vanilla//") -- Ditto
273 %************************************************************************
275 \subsection{Tau, sigma and rho}
277 %************************************************************************
280 mkSigmaTy tyvars theta tau = mkForAllTys tyvars (mkPhiTy theta tau)
282 mkPhiTy :: [PredType] -> Type -> Type
283 mkPhiTy theta ty = foldr (\p r -> FunTy (mkPredTy p) r) ty theta
286 @isTauTy@ tests for nested for-alls.
289 isTauTy :: Type -> Bool
290 isTauTy (TyVarTy v) = True
291 isTauTy (TyConApp _ tys) = all isTauTy tys
292 isTauTy (NewTcApp _ tys) = all isTauTy tys
293 isTauTy (AppTy a b) = isTauTy a && isTauTy b
294 isTauTy (FunTy a b) = isTauTy a && isTauTy b
295 isTauTy (PredTy p) = True -- Don't look through source types
296 isTauTy (NoteTy _ ty) = isTauTy ty
297 isTauTy other = False
301 getDFunTyKey :: Type -> OccName -- Get some string from a type, to be used to
302 -- construct a dictionary function name
303 getDFunTyKey (TyVarTy tv) = getOccName tv
304 getDFunTyKey (TyConApp tc _) = getOccName tc
305 getDFunTyKey (NewTcApp tc _) = getOccName tc
306 getDFunTyKey (AppTy fun _) = getDFunTyKey fun
307 getDFunTyKey (NoteTy _ t) = getDFunTyKey t
308 getDFunTyKey (FunTy arg _) = getOccName funTyCon
309 getDFunTyKey (ForAllTy _ t) = getDFunTyKey t
310 getDFunTyKey ty = pprPanic "getDFunTyKey" (pprType ty)
311 -- PredTy shouldn't happen
315 %************************************************************************
317 \subsection{Expanding and splitting}
319 %************************************************************************
321 These tcSplit functions are like their non-Tc analogues, but
322 a) they do not look through newtypes
323 b) they do not look through PredTys
324 c) [future] they ignore usage-type annotations
326 However, they are non-monadic and do not follow through mutable type
327 variables. It's up to you to make sure this doesn't matter.
330 tcSplitForAllTys :: Type -> ([TyVar], Type)
331 tcSplitForAllTys ty = split ty ty []
333 split orig_ty (ForAllTy tv ty) tvs = split ty ty (tv:tvs)
334 split orig_ty (NoteTy n ty) tvs = split orig_ty ty tvs
335 split orig_ty t tvs = (reverse tvs, orig_ty)
337 tcIsForAllTy (ForAllTy tv ty) = True
338 tcIsForAllTy (NoteTy n ty) = tcIsForAllTy ty
339 tcIsForAllTy t = False
341 tcSplitPhiTy :: Type -> ([PredType], Type)
342 tcSplitPhiTy ty = split ty ty []
344 split orig_ty (FunTy arg res) ts = case tcSplitPredTy_maybe arg of
345 Just p -> split res res (p:ts)
346 Nothing -> (reverse ts, orig_ty)
347 split orig_ty (NoteTy n ty) ts = split orig_ty ty ts
348 split orig_ty ty ts = (reverse ts, orig_ty)
350 tcSplitSigmaTy ty = case tcSplitForAllTys ty of
351 (tvs, rho) -> case tcSplitPhiTy rho of
352 (theta, tau) -> (tvs, theta, tau)
354 tcTyConAppTyCon :: Type -> TyCon
355 tcTyConAppTyCon ty = fst (tcSplitTyConApp ty)
357 tcTyConAppArgs :: Type -> [Type]
358 tcTyConAppArgs ty = snd (tcSplitTyConApp ty)
360 tcSplitTyConApp :: Type -> (TyCon, [Type])
361 tcSplitTyConApp ty = case tcSplitTyConApp_maybe ty of
363 Nothing -> pprPanic "tcSplitTyConApp" (pprType ty)
365 tcSplitTyConApp_maybe :: Type -> Maybe (TyCon, [Type])
366 tcSplitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
367 tcSplitTyConApp_maybe (NewTcApp tc tys) = Just (tc, tys)
368 tcSplitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res])
369 tcSplitTyConApp_maybe (NoteTy n ty) = tcSplitTyConApp_maybe ty
370 -- Newtypes are opaque, so they may be split
371 -- However, predicates are not treated
372 -- as tycon applications by the type checker
373 tcSplitTyConApp_maybe other = Nothing
375 tcSplitFunTys :: Type -> ([Type], Type)
376 tcSplitFunTys ty = case tcSplitFunTy_maybe ty of
378 Just (arg,res) -> (arg:args, res')
380 (args,res') = tcSplitFunTys res
382 tcSplitFunTy_maybe :: Type -> Maybe (Type, Type)
383 tcSplitFunTy_maybe (FunTy arg res) = Just (arg, res)
384 tcSplitFunTy_maybe (NoteTy n ty) = tcSplitFunTy_maybe ty
385 tcSplitFunTy_maybe other = Nothing
387 tcFunArgTy ty = case tcSplitFunTy_maybe ty of { Just (arg,res) -> arg }
388 tcFunResultTy ty = case tcSplitFunTy_maybe ty of { Just (arg,res) -> res }
391 tcSplitAppTy_maybe :: Type -> Maybe (Type, Type)
392 tcSplitAppTy_maybe (FunTy ty1 ty2) = Just (TyConApp funTyCon [ty1], ty2)
393 tcSplitAppTy_maybe (AppTy ty1 ty2) = Just (ty1, ty2)
394 tcSplitAppTy_maybe (NoteTy n ty) = tcSplitAppTy_maybe ty
395 tcSplitAppTy_maybe (TyConApp tc tys) = case snocView tys of
396 Just (tys', ty') -> Just (TyConApp tc tys', ty')
398 tcSplitAppTy_maybe (NewTcApp tc tys) = case snocView tys of
399 Just (tys', ty') -> Just (NewTcApp tc tys', ty')
401 tcSplitAppTy_maybe other = Nothing
403 tcSplitAppTy ty = case tcSplitAppTy_maybe ty of
405 Nothing -> pprPanic "tcSplitAppTy" (pprType ty)
407 tcSplitAppTys :: Type -> (Type, [Type])
411 go ty args = case tcSplitAppTy_maybe ty of
412 Just (ty', arg) -> go ty' (arg:args)
415 tcGetTyVar_maybe :: Type -> Maybe TyVar
416 tcGetTyVar_maybe (TyVarTy tv) = Just tv
417 tcGetTyVar_maybe (NoteTy _ t) = tcGetTyVar_maybe t
418 tcGetTyVar_maybe other = Nothing
420 tcGetTyVar :: String -> Type -> TyVar
421 tcGetTyVar msg ty = expectJust msg (tcGetTyVar_maybe ty)
423 tcIsTyVarTy :: Type -> Bool
424 tcIsTyVarTy ty = maybeToBool (tcGetTyVar_maybe ty)
427 The type of a method for class C is always of the form:
428 Forall a1..an. C a1..an => sig_ty
429 where sig_ty is the type given by the method's signature, and thus in general
430 is a ForallTy. At the point that splitMethodTy is called, it is expected
431 that the outer Forall has already been stripped off. splitMethodTy then
432 returns (C a1..an, sig_ty') where sig_ty' is sig_ty with any Notes stripped off.
435 tcSplitMethodTy :: Type -> (PredType, Type)
436 tcSplitMethodTy ty = split ty
438 split (FunTy arg res) = case tcSplitPredTy_maybe arg of
440 Nothing -> panic "splitMethodTy"
441 split (NoteTy n ty) = split ty
442 split _ = panic "splitMethodTy"
444 tcSplitDFunTy :: Type -> ([TyVar], [PredType], Class, [Type])
445 -- Split the type of a dictionary function
447 = case tcSplitSigmaTy ty of { (tvs, theta, tau) ->
448 case tcSplitPredTy_maybe tau of { Just (ClassP clas tys) ->
449 (tvs, theta, clas, tys) }}
452 (allDistinctTyVars tys tvs) = True
454 all the types tys are type variables,
455 distinct from each other and from tvs.
457 This is useful when checking that unification hasn't unified signature
458 type variables. For example, if the type sig is
459 f :: forall a b. a -> b -> b
460 we want to check that 'a' and 'b' havn't
461 (a) been unified with a non-tyvar type
462 (b) been unified with each other (all distinct)
463 (c) been unified with a variable free in the environment
466 allDistinctTyVars :: [Type] -> TyVarSet -> Bool
468 allDistinctTyVars [] acc
470 allDistinctTyVars (ty:tys) acc
471 = case tcGetTyVar_maybe ty of
472 Nothing -> False -- (a)
473 Just tv | tv `elemVarSet` acc -> False -- (b) or (c)
474 | otherwise -> allDistinctTyVars tys (acc `extendVarSet` tv)
478 %************************************************************************
480 \subsection{Predicate types}
482 %************************************************************************
485 tcSplitPredTy_maybe :: Type -> Maybe PredType
486 -- Returns Just for predicates only
487 tcSplitPredTy_maybe (NoteTy _ ty) = tcSplitPredTy_maybe ty
488 tcSplitPredTy_maybe (PredTy p) = Just p
489 tcSplitPredTy_maybe other = Nothing
491 predTyUnique :: PredType -> Unique
492 predTyUnique (IParam n _) = getUnique (ipNameName n)
493 predTyUnique (ClassP clas tys) = getUnique clas
495 mkPredName :: Unique -> SrcLoc -> PredType -> Name
496 mkPredName uniq loc (ClassP cls tys) = mkInternalName uniq (mkDictOcc (getOccName cls)) loc
497 mkPredName uniq loc (IParam ip ty) = mkInternalName uniq (getOccName (ipNameName ip)) loc
501 --------------------- Dictionary types ---------------------------------
504 mkClassPred clas tys = ClassP clas tys
506 isClassPred :: PredType -> Bool
507 isClassPred (ClassP clas tys) = True
508 isClassPred other = False
510 isTyVarClassPred (ClassP clas tys) = all tcIsTyVarTy tys
511 isTyVarClassPred other = False
513 getClassPredTys_maybe :: PredType -> Maybe (Class, [Type])
514 getClassPredTys_maybe (ClassP clas tys) = Just (clas, tys)
515 getClassPredTys_maybe _ = Nothing
517 getClassPredTys :: PredType -> (Class, [Type])
518 getClassPredTys (ClassP clas tys) = (clas, tys)
520 mkDictTy :: Class -> [Type] -> Type
521 mkDictTy clas tys = mkPredTy (ClassP clas tys)
523 isDictTy :: Type -> Bool
524 isDictTy (PredTy p) = isClassPred p
525 isDictTy (NoteTy _ ty) = isDictTy ty
526 isDictTy other = False
529 --------------------- Implicit parameters ---------------------------------
532 isIPPred :: PredType -> Bool
533 isIPPred (IParam _ _) = True
534 isIPPred other = False
536 isInheritablePred :: PredType -> Bool
537 -- Can be inherited by a context. For example, consider
538 -- f x = let g y = (?v, y+x)
539 -- in (g 3 with ?v = 8,
541 -- The point is that g's type must be quantifed over ?v:
542 -- g :: (?v :: a) => a -> a
543 -- but it doesn't need to be quantified over the Num a dictionary
544 -- which can be free in g's rhs, and shared by both calls to g
545 isInheritablePred (ClassP _ _) = True
546 isInheritablePred other = False
548 isLinearPred :: TcPredType -> Bool
549 isLinearPred (IParam (Linear n) _) = True
550 isLinearPred other = False
554 %************************************************************************
556 \subsection{Comparison}
558 %************************************************************************
560 Comparison, taking note of newtypes, predicates, etc,
563 tcEqType :: Type -> Type -> Bool
564 tcEqType ty1 ty2 = case ty1 `tcCmpType` ty2 of { EQ -> True; other -> False }
566 tcEqTypes :: [Type] -> [Type] -> Bool
567 tcEqTypes ty1 ty2 = case ty1 `tcCmpTypes` ty2 of { EQ -> True; other -> False }
569 tcEqPred :: PredType -> PredType -> Bool
570 tcEqPred p1 p2 = case p1 `tcCmpPred` p2 of { EQ -> True; other -> False }
573 tcCmpType :: Type -> Type -> Ordering
574 tcCmpType ty1 ty2 = cmpTy emptyVarEnv ty1 ty2
576 tcCmpTypes tys1 tys2 = cmpTys emptyVarEnv tys1 tys2
578 tcCmpPred p1 p2 = cmpPredTy emptyVarEnv p1 p2
580 cmpTys env tys1 tys2 = cmpList (cmpTy env) tys1 tys2
583 cmpTy :: TyVarEnv TyVar -> Type -> Type -> Ordering
584 -- The "env" maps type variables in ty1 to type variables in ty2
585 -- So when comparing for-alls.. (forall tv1 . t1) (forall tv2 . t2)
586 -- we in effect substitute tv2 for tv1 in t1 before continuing
588 -- Look through NoteTy
589 cmpTy env (NoteTy _ ty1) ty2 = cmpTy env ty1 ty2
590 cmpTy env ty1 (NoteTy _ ty2) = cmpTy env ty1 ty2
592 -- Deal with equal constructors
593 cmpTy env (TyVarTy tv1) (TyVarTy tv2) = case lookupVarEnv env tv1 of
594 Just tv1a -> tv1a `compare` tv2
595 Nothing -> tv1 `compare` tv2
597 cmpTy env (PredTy p1) (PredTy p2) = cmpPredTy env p1 p2
598 cmpTy env (AppTy f1 a1) (AppTy f2 a2) = cmpTy env f1 f2 `thenCmp` cmpTy env a1 a2
599 cmpTy env (FunTy f1 a1) (FunTy f2 a2) = cmpTy env f1 f2 `thenCmp` cmpTy env a1 a2
600 cmpTy env (TyConApp tc1 tys1) (TyConApp tc2 tys2) = (tc1 `compare` tc2) `thenCmp` (cmpTys env tys1 tys2)
601 cmpTy env (NewTcApp tc1 tys1) (NewTcApp tc2 tys2) = (tc1 `compare` tc2) `thenCmp` (cmpTys env tys1 tys2)
602 cmpTy env (ForAllTy tv1 t1) (ForAllTy tv2 t2) = cmpTy (extendVarEnv env tv1 tv2) t1 t2
604 -- Deal with the rest: TyVarTy < AppTy < FunTy < TyConApp < NewTcApp < ForAllTy < PredTy
605 cmpTy env (AppTy _ _) (TyVarTy _) = GT
607 cmpTy env (FunTy _ _) (TyVarTy _) = GT
608 cmpTy env (FunTy _ _) (AppTy _ _) = GT
610 cmpTy env (TyConApp _ _) (TyVarTy _) = GT
611 cmpTy env (TyConApp _ _) (AppTy _ _) = GT
612 cmpTy env (TyConApp _ _) (FunTy _ _) = GT
614 cmpTy env (NewTcApp _ _) (TyVarTy _) = GT
615 cmpTy env (NewTcApp _ _) (AppTy _ _) = GT
616 cmpTy env (NewTcApp _ _) (FunTy _ _) = GT
617 cmpTy env (NewTcApp _ _) (TyConApp _ _) = GT
619 cmpTy env (ForAllTy _ _) (TyVarTy _) = GT
620 cmpTy env (ForAllTy _ _) (AppTy _ _) = GT
621 cmpTy env (ForAllTy _ _) (FunTy _ _) = GT
622 cmpTy env (ForAllTy _ _) (TyConApp _ _) = GT
623 cmpTy env (ForAllTy _ _) (NewTcApp _ _) = GT
625 cmpTy env (PredTy _) t2 = GT
631 cmpPredTy :: TyVarEnv TyVar -> PredType -> PredType -> Ordering
632 cmpPredTy env (IParam n1 ty1) (IParam n2 ty2) = (n1 `compare` n2) `thenCmp` (cmpTy env ty1 ty2)
633 -- Compare types as well as names for implicit parameters
634 -- This comparison is used exclusively (I think) for the
635 -- finite map built in TcSimplify
636 cmpPredTy env (IParam _ _) (ClassP _ _) = LT
637 cmpPredTy env (ClassP _ _) (IParam _ _) = GT
638 cmpPredTy env (ClassP c1 tys1) (ClassP c2 tys2) = (c1 `compare` c2) `thenCmp` (cmpTys env tys1 tys2)
641 PredTypes are used as a FM key in TcSimplify,
642 so we take the easy path and make them an instance of Ord
645 instance Eq PredType where { (==) = tcEqPred }
646 instance Ord PredType where { compare = tcCmpPred }
650 %************************************************************************
652 \subsection{Predicates}
654 %************************************************************************
656 isSigmaTy returns true of any qualified type. It doesn't *necessarily* have
658 f :: (?x::Int) => Int -> Int
661 isSigmaTy :: Type -> Bool
662 isSigmaTy (ForAllTy tyvar ty) = True
663 isSigmaTy (FunTy a b) = isPredTy a
664 isSigmaTy (NoteTy n ty) = isSigmaTy ty
667 isOverloadedTy :: Type -> Bool
668 isOverloadedTy (ForAllTy tyvar ty) = isOverloadedTy ty
669 isOverloadedTy (FunTy a b) = isPredTy a
670 isOverloadedTy (NoteTy n ty) = isOverloadedTy ty
671 isOverloadedTy _ = False
673 isPredTy :: Type -> Bool -- Belongs in TcType because it does
674 -- not look through newtypes, or predtypes (of course)
675 isPredTy (NoteTy _ ty) = isPredTy ty
676 isPredTy (PredTy sty) = True
681 isFloatTy = is_tc floatTyConKey
682 isDoubleTy = is_tc doubleTyConKey
683 isIntegerTy = is_tc integerTyConKey
684 isIntTy = is_tc intTyConKey
685 isAddrTy = is_tc addrTyConKey
686 isBoolTy = is_tc boolTyConKey
687 isUnitTy = is_tc unitTyConKey
689 is_tc :: Unique -> Type -> Bool
690 -- Newtypes are opaque to this
691 is_tc uniq ty = case tcSplitTyConApp_maybe ty of
692 Just (tc, _) -> uniq == getUnique tc
697 %************************************************************************
701 %************************************************************************
704 deNoteType :: Type -> Type
705 -- Remove synonyms, but not predicate types
706 deNoteType ty@(TyVarTy tyvar) = ty
707 deNoteType (TyConApp tycon tys) = TyConApp tycon (map deNoteType tys)
708 deNoteType (NewTcApp tycon tys) = NewTcApp tycon (map deNoteType tys)
709 deNoteType (PredTy p) = PredTy (deNotePredType p)
710 deNoteType (NoteTy _ ty) = deNoteType ty
711 deNoteType (AppTy fun arg) = AppTy (deNoteType fun) (deNoteType arg)
712 deNoteType (FunTy fun arg) = FunTy (deNoteType fun) (deNoteType arg)
713 deNoteType (ForAllTy tv ty) = ForAllTy tv (deNoteType ty)
715 deNotePredType :: PredType -> PredType
716 deNotePredType (ClassP c tys) = ClassP c (map deNoteType tys)
717 deNotePredType (IParam n ty) = IParam n (deNoteType ty)
720 Find the free tycons and classes of a type. This is used in the front
724 tyClsNamesOfType :: Type -> NameSet
725 tyClsNamesOfType (TyVarTy tv) = emptyNameSet
726 tyClsNamesOfType (TyConApp tycon tys) = unitNameSet (getName tycon) `unionNameSets` tyClsNamesOfTypes tys
727 tyClsNamesOfType (NewTcApp tycon tys) = unitNameSet (getName tycon) `unionNameSets` tyClsNamesOfTypes tys
728 tyClsNamesOfType (NoteTy (SynNote ty1) ty2) = tyClsNamesOfType ty1
729 tyClsNamesOfType (NoteTy other_note ty2) = tyClsNamesOfType ty2
730 tyClsNamesOfType (PredTy (IParam n ty)) = tyClsNamesOfType ty
731 tyClsNamesOfType (PredTy (ClassP cl tys)) = unitNameSet (getName cl) `unionNameSets` tyClsNamesOfTypes tys
732 tyClsNamesOfType (FunTy arg res) = tyClsNamesOfType arg `unionNameSets` tyClsNamesOfType res
733 tyClsNamesOfType (AppTy fun arg) = tyClsNamesOfType fun `unionNameSets` tyClsNamesOfType arg
734 tyClsNamesOfType (ForAllTy tyvar ty) = tyClsNamesOfType ty
736 tyClsNamesOfTypes tys = foldr (unionNameSets . tyClsNamesOfType) emptyNameSet tys
738 tyClsNamesOfDFunHead :: Type -> NameSet
739 -- Find the free type constructors and classes
740 -- of the head of the dfun instance type
741 -- The 'dfun_head_type' is because of
742 -- instance Foo a => Baz T where ...
743 -- The decl is an orphan if Baz and T are both not locally defined,
744 -- even if Foo *is* locally defined
745 tyClsNamesOfDFunHead dfun_ty
746 = case tcSplitSigmaTy dfun_ty of
747 (tvs,_,head_ty) -> tyClsNamesOfType head_ty
749 classesOfTheta :: ThetaType -> [Class]
750 -- Looks just for ClassP things; maybe it should check
751 classesOfTheta preds = [ c | ClassP c _ <- preds ]
755 %************************************************************************
757 \subsection[TysWiredIn-ext-type]{External types}
759 %************************************************************************
761 The compiler's foreign function interface supports the passing of a
762 restricted set of types as arguments and results (the restricting factor
766 isFFIArgumentTy :: DynFlags -> Safety -> Type -> Bool
767 -- Checks for valid argument type for a 'foreign import'
768 isFFIArgumentTy dflags safety ty
769 = checkRepTyCon (legalOutgoingTyCon dflags safety) ty
771 isFFIExternalTy :: Type -> Bool
772 -- Types that are allowed as arguments of a 'foreign export'
773 isFFIExternalTy ty = checkRepTyCon legalFEArgTyCon ty
775 isFFIImportResultTy :: DynFlags -> Type -> Bool
776 isFFIImportResultTy dflags ty
777 = checkRepTyCon (legalFIResultTyCon dflags) ty
779 isFFIExportResultTy :: Type -> Bool
780 isFFIExportResultTy ty = checkRepTyCon legalFEResultTyCon ty
782 isFFIDynArgumentTy :: Type -> Bool
783 -- The argument type of a foreign import dynamic must be Ptr, FunPtr, Addr,
784 -- or a newtype of either.
785 isFFIDynArgumentTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey, addrTyConKey]
787 isFFIDynResultTy :: Type -> Bool
788 -- The result type of a foreign export dynamic must be Ptr, FunPtr, Addr,
789 -- or a newtype of either.
790 isFFIDynResultTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey, addrTyConKey]
792 isFFILabelTy :: Type -> Bool
793 -- The type of a foreign label must be Ptr, FunPtr, Addr,
794 -- or a newtype of either.
795 isFFILabelTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey, addrTyConKey]
797 isFFIDotnetTy :: DynFlags -> Type -> Bool
798 isFFIDotnetTy dflags ty
799 = checkRepTyCon (\ tc -> not (isByteArrayLikeTyCon tc) &&
800 (legalFIResultTyCon dflags tc ||
801 isFFIDotnetObjTy ty || isStringTy ty)) ty
803 -- Support String as an argument or result from a .NET FFI call.
805 case tcSplitTyConApp_maybe (repType ty) of
808 case tcSplitTyConApp_maybe (repType arg_ty) of
809 Just (cc,[]) -> cc == charTyCon
813 -- Support String as an argument or result from a .NET FFI call.
814 isFFIDotnetObjTy ty =
816 (_, t_ty) = tcSplitForAllTys ty
818 case tcSplitTyConApp_maybe (repType t_ty) of
819 Just (tc, [arg_ty]) | getName tc == objectTyConName -> True
822 toDNType :: Type -> DNType
824 | isStringTy ty = DNString
825 | isFFIDotnetObjTy ty = DNObject
826 | Just (tc,argTys) <- tcSplitTyConApp_maybe ty =
827 case lookup (getUnique tc) dn_assoc of
830 | tc `hasKey` ioTyConKey -> toDNType (head argTys)
831 | otherwise -> pprPanic ("toDNType: unsupported .NET type") (pprType ty <+> parens (hcat (map pprType argTys)) <+> ppr tc)
833 dn_assoc :: [ (Unique, DNType) ]
834 dn_assoc = [ (unitTyConKey, DNUnit)
835 , (intTyConKey, DNInt)
836 , (int8TyConKey, DNInt8)
837 , (int16TyConKey, DNInt16)
838 , (int32TyConKey, DNInt32)
839 , (int64TyConKey, DNInt64)
840 , (wordTyConKey, DNInt)
841 , (word8TyConKey, DNWord8)
842 , (word16TyConKey, DNWord16)
843 , (word32TyConKey, DNWord32)
844 , (word64TyConKey, DNWord64)
845 , (floatTyConKey, DNFloat)
846 , (doubleTyConKey, DNDouble)
847 , (addrTyConKey, DNPtr)
848 , (ptrTyConKey, DNPtr)
849 , (funPtrTyConKey, DNPtr)
850 , (charTyConKey, DNChar)
851 , (boolTyConKey, DNBool)
854 checkRepTyCon :: (TyCon -> Bool) -> Type -> Bool
855 -- Look through newtypes
856 -- Non-recursive ones are transparent to splitTyConApp,
857 -- but recursive ones aren't
858 checkRepTyCon check_tc ty
859 | Just (tc,_) <- splitTyConApp_maybe (repType ty) = check_tc tc
862 checkRepTyConKey :: [Unique] -> Type -> Bool
863 -- Like checkRepTyCon, but just looks at the TyCon key
864 checkRepTyConKey keys
865 = checkRepTyCon (\tc -> tyConUnique tc `elem` keys)
868 ----------------------------------------------
869 These chaps do the work; they are not exported
870 ----------------------------------------------
873 legalFEArgTyCon :: TyCon -> Bool
874 -- It's illegal to return foreign objects and (mutable)
875 -- bytearrays from a _ccall_ / foreign declaration
876 -- (or be passed them as arguments in foreign exported functions).
878 | isByteArrayLikeTyCon tc
880 -- It's also illegal to make foreign exports that take unboxed
881 -- arguments. The RTS API currently can't invoke such things. --SDM 7/2000
883 = boxedMarshalableTyCon tc
885 legalFIResultTyCon :: DynFlags -> TyCon -> Bool
886 legalFIResultTyCon dflags tc
887 | isByteArrayLikeTyCon tc = False
888 | tc == unitTyCon = True
889 | otherwise = marshalableTyCon dflags tc
891 legalFEResultTyCon :: TyCon -> Bool
892 legalFEResultTyCon tc
893 | isByteArrayLikeTyCon tc = False
894 | tc == unitTyCon = True
895 | otherwise = boxedMarshalableTyCon tc
897 legalOutgoingTyCon :: DynFlags -> Safety -> TyCon -> Bool
898 -- Checks validity of types going from Haskell -> external world
899 legalOutgoingTyCon dflags safety tc
900 | playSafe safety && isByteArrayLikeTyCon tc
903 = marshalableTyCon dflags tc
905 marshalableTyCon dflags tc
906 = (dopt Opt_GlasgowExts dflags && isUnLiftedTyCon tc)
907 || boxedMarshalableTyCon tc
909 boxedMarshalableTyCon tc
910 = getUnique tc `elem` [ intTyConKey, int8TyConKey, int16TyConKey
911 , int32TyConKey, int64TyConKey
912 , wordTyConKey, word8TyConKey, word16TyConKey
913 , word32TyConKey, word64TyConKey
914 , floatTyConKey, doubleTyConKey
915 , addrTyConKey, ptrTyConKey, funPtrTyConKey
918 , byteArrayTyConKey, mutableByteArrayTyConKey
922 isByteArrayLikeTyCon :: TyCon -> Bool
923 isByteArrayLikeTyCon tc =
924 getUnique tc `elem` [byteArrayTyConKey, mutableByteArrayTyConKey]
928 %************************************************************************
930 \subsection{Unification with an explicit substitution}
932 %************************************************************************
934 Unify types with an explicit substitution and no monad.
935 Ignore usage annotations.
939 = (TyVarSet, -- Set of template tyvars
940 TyVarSubstEnv) -- Not necessarily idempotent
942 unifyTysX :: TyVarSet -- Template tyvars
945 -> Maybe TyVarSubstEnv
946 unifyTysX tmpl_tyvars ty1 ty2
947 = uTysX ty1 ty2 (\(_,s) -> Just s) (tmpl_tyvars, emptySubstEnv)
949 unifyExtendTysX :: TyVarSet -- Template tyvars
950 -> TyVarSubstEnv -- Substitution to start with
953 -> Maybe TyVarSubstEnv -- Extended substitution
954 unifyExtendTysX tmpl_tyvars subst ty1 ty2
955 = uTysX ty1 ty2 (\(_,s) -> Just s) (tmpl_tyvars, subst)
957 unifyTyListsX :: TyVarSet -> [Type] -> [Type]
958 -> Maybe TyVarSubstEnv
959 unifyTyListsX tmpl_tyvars tys1 tys2
960 = uTyListsX tys1 tys2 (\(_,s) -> Just s) (tmpl_tyvars, emptySubstEnv)
965 -> (MySubst -> Maybe result)
969 uTysX (NoteTy _ ty1) ty2 k subst = uTysX ty1 ty2 k subst
970 uTysX ty1 (NoteTy _ ty2) k subst = uTysX ty1 ty2 k subst
972 -- Variables; go for uVar
973 uTysX (TyVarTy tyvar1) (TyVarTy tyvar2) k subst
976 uTysX (TyVarTy tyvar1) ty2 k subst@(tmpls,_)
977 | tyvar1 `elemVarSet` tmpls
978 = uVarX tyvar1 ty2 k subst
979 uTysX ty1 (TyVarTy tyvar2) k subst@(tmpls,_)
980 | tyvar2 `elemVarSet` tmpls
981 = uVarX tyvar2 ty1 k subst
984 uTysX (PredTy (IParam n1 t1)) (PredTy (IParam n2 t2)) k subst
985 | n1 == n2 = uTysX t1 t2 k subst
986 uTysX (PredTy (ClassP c1 tys1)) (PredTy (ClassP c2 tys2)) k subst
987 | c1 == c2 = uTyListsX tys1 tys2 k subst
989 -- Functions; just check the two parts
990 uTysX (FunTy fun1 arg1) (FunTy fun2 arg2) k subst
991 = uTysX fun1 fun2 (uTysX arg1 arg2 k) subst
993 -- Type constructors must match
994 uTysX (NewTcApp tc1 tys1) (NewTcApp tc2 tys2) k subst
995 | tc1 == tc2 = uTyListsX tys1 tys2 k subst
996 uTysX (TyConApp con1 tys1) (TyConApp con2 tys2) k subst
997 | (con1 == con2 && equalLength tys1 tys2)
998 = uTyListsX tys1 tys2 k subst
1000 -- Applications need a bit of care!
1001 -- They can match FunTy and TyConApp, so use splitAppTy_maybe
1002 -- NB: we've already dealt with type variables and Notes,
1003 -- so if one type is an App the other one jolly well better be too
1004 uTysX (AppTy s1 t1) ty2 k subst
1005 = case tcSplitAppTy_maybe ty2 of
1006 Just (s2, t2) -> uTysX s1 s2 (uTysX t1 t2 k) subst
1007 Nothing -> Nothing -- Fail
1009 uTysX ty1 (AppTy s2 t2) k subst
1010 = case tcSplitAppTy_maybe ty1 of
1011 Just (s1, t1) -> uTysX s1 s2 (uTysX t1 t2 k) subst
1012 Nothing -> Nothing -- Fail
1014 -- Not expecting for-alls in unification
1016 uTysX (ForAllTy _ _) ty2 k subst = panic "Unify.uTysX subst:ForAllTy (1st arg)"
1017 uTysX ty1 (ForAllTy _ _) k subst = panic "Unify.uTysX subst:ForAllTy (2nd arg)"
1020 -- Anything else fails
1021 uTysX ty1 ty2 k subst = Nothing
1024 uTyListsX [] [] k subst = k subst
1025 uTyListsX (ty1:tys1) (ty2:tys2) k subst = uTysX ty1 ty2 (uTyListsX tys1 tys2 k) subst
1026 uTyListsX tys1 tys2 k subst = Nothing -- Fail if the lists are different lengths
1030 -- Invariant: tv1 is a unifiable variable
1031 uVarX tv1 ty2 k subst@(tmpls, env)
1032 = case lookupSubstEnv env tv1 of
1033 Just (DoneTy ty1) -> -- Already bound
1034 uTysX ty1 ty2 k subst
1036 Nothing -- Not already bound
1037 | typeKind ty2 `eqKind` tyVarKind tv1
1038 && occur_check_ok ty2
1039 -> -- No kind mismatch nor occur check
1040 k (tmpls, extendSubstEnv env tv1 (DoneTy ty2))
1042 | otherwise -> Nothing -- Fail if kind mis-match or occur check
1044 occur_check_ok ty = all occur_check_ok_tv (varSetElems (tyVarsOfType ty))
1045 occur_check_ok_tv tv | tv1 == tv = False
1046 | otherwise = case lookupSubstEnv env tv of
1048 Just (DoneTy ty) -> occur_check_ok ty
1053 %************************************************************************
1055 \subsection{Matching on types}
1057 %************************************************************************
1059 Matching is a {\em unidirectional} process, matching a type against a
1060 template (which is just a type with type variables in it). The
1061 matcher assumes that there are no repeated type variables in the
1062 template, so that it simply returns a mapping of type variables to
1063 types. It also fails on nested foralls.
1065 @matchTys@ matches corresponding elements of a list of templates and
1066 types. It and @matchTy@ both ignore usage annotations, unlike the
1067 main function @match@.
1070 matchTy :: TyVarSet -- Template tyvars
1072 -> Type -- Proposed instance of template
1073 -> Maybe TyVarSubstEnv -- Matching substitution
1076 matchTys :: TyVarSet -- Template tyvars
1077 -> [Type] -- Templates
1078 -> [Type] -- Proposed instance of template
1079 -> Maybe (TyVarSubstEnv, -- Matching substitution
1080 [Type]) -- Left over instance types
1082 matchTy tmpls ty1 ty2 = match ty1 ty2 tmpls (\ senv -> Just senv) emptySubstEnv
1084 matchTys tmpls tys1 tys2 = match_list tys1 tys2 tmpls
1085 (\ (senv,tys) -> Just (senv,tys))
1089 @match@ is the main function. It takes a flag indicating whether
1090 usage annotations are to be respected.
1093 match :: Type -> Type -- Current match pair
1094 -> TyVarSet -- Template vars
1095 -> (TyVarSubstEnv -> Maybe result) -- Continuation
1096 -> TyVarSubstEnv -- Current subst
1099 -- When matching against a type variable, see if the variable
1100 -- has already been bound. If so, check that what it's bound to
1101 -- is the same as ty; if not, bind it and carry on.
1103 match (TyVarTy v) ty tmpls k senv
1104 | v `elemVarSet` tmpls
1105 = -- v is a template variable
1106 case lookupSubstEnv senv v of
1107 Nothing | typeKind ty `eqKind` tyVarKind v
1108 -- We do a kind check, just as in the uVarX above
1109 -- The kind check is needed to avoid bogus matches
1110 -- of (a b) with (c d), where the kinds don't match
1111 -- An occur check isn't needed when matching.
1112 -> k (extendSubstEnv senv v (DoneTy ty))
1114 | otherwise -> Nothing -- Fails
1116 Just (DoneTy ty') | ty' `tcEqType` ty -> k senv -- Succeeds
1117 | otherwise -> Nothing -- Fails
1120 = -- v is not a template variable; ty had better match
1121 -- Can't use (==) because types differ
1122 case tcGetTyVar_maybe ty of
1123 Just v' | v == v' -> k senv -- Success
1124 other -> Nothing -- Failure
1125 -- This tcGetTyVar_maybe is *required* because it must strip Notes.
1126 -- I guess the reason the Note-stripping case is *last* rather than first
1127 -- is to preserve type synonyms etc., so I'm not moving it to the
1128 -- top; but this means that (without the deNotetype) a type
1129 -- variable may not match the pattern (TyVarTy v') as one would
1130 -- expect, due to an intervening Note. KSW 2000-06.
1133 match (PredTy (IParam n1 t1)) (PredTy (IParam n2 t2)) tmpls k senv
1134 | n1 == n2 = match t1 t2 tmpls k senv
1135 match (PredTy (ClassP c1 tys1)) (PredTy (ClassP c2 tys2)) tmpls k senv
1136 | c1 == c2 = match_list_exactly tys1 tys2 tmpls k senv
1138 -- Functions; just check the two parts
1139 match (FunTy arg1 res1) (FunTy arg2 res2) tmpls k senv
1140 = match arg1 arg2 tmpls (match res1 res2 tmpls k) senv
1142 match (AppTy fun1 arg1) ty2 tmpls k senv
1143 = case tcSplitAppTy_maybe ty2 of
1144 Just (fun2,arg2) -> match fun1 fun2 tmpls (match arg1 arg2 tmpls k) senv
1145 Nothing -> Nothing -- Fail
1147 -- Newtypes are opaque; predicate types should not happen
1148 match (NewTcApp tc1 tys1) (NewTcApp tc2 tys2) tmpls k senv
1149 | tc1 == tc2 = match_list_exactly tys1 tys2 tmpls k senv
1150 match (TyConApp tc1 tys1) (TyConApp tc2 tys2) tmpls k senv
1151 | tc1 == tc2 = match_list_exactly tys1 tys2 tmpls k senv
1153 -- With type synonyms, we have to be careful for the exact
1154 -- same reasons as in the unifier. Please see the
1155 -- considerable commentary there before changing anything
1156 -- here! (WDP 95/05)
1157 match (NoteTy n1 ty1) ty2 tmpls k senv = match ty1 ty2 tmpls k senv
1158 match ty1 (NoteTy n2 ty2) tmpls k senv = match ty1 ty2 tmpls k senv
1161 match _ _ _ _ _ = Nothing
1163 match_list_exactly tys1 tys2 tmpls k senv
1164 = match_list tys1 tys2 tmpls k' senv
1166 k' (senv', tys2') | null tys2' = k senv' -- Succeed
1167 | otherwise = Nothing -- Fail
1169 match_list [] tys2 tmpls k senv = k (senv, tys2)
1170 match_list (ty1:tys1) [] tmpls k senv = Nothing -- Not enough arg tys => failure
1171 match_list (ty1:tys1) (ty2:tys2) tmpls k senv
1172 = match ty1 ty2 tmpls (match_list tys1 tys2 tmpls k) senv