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 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
99 isPrimitiveType, isTyVarTy, isPredTy,
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, isPredTy,
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
675 isFloatTy = is_tc floatTyConKey
676 isDoubleTy = is_tc doubleTyConKey
677 isIntegerTy = is_tc integerTyConKey
678 isIntTy = is_tc intTyConKey
679 isAddrTy = is_tc addrTyConKey
680 isBoolTy = is_tc boolTyConKey
681 isUnitTy = is_tc unitTyConKey
683 is_tc :: Unique -> Type -> Bool
684 -- Newtypes are opaque to this
685 is_tc uniq ty = case tcSplitTyConApp_maybe ty of
686 Just (tc, _) -> uniq == getUnique tc
691 %************************************************************************
695 %************************************************************************
698 deNoteType :: Type -> Type
699 -- Remove synonyms, but not predicate types
700 deNoteType ty@(TyVarTy tyvar) = ty
701 deNoteType (TyConApp tycon tys) = TyConApp tycon (map deNoteType tys)
702 deNoteType (NewTcApp tycon tys) = NewTcApp tycon (map deNoteType tys)
703 deNoteType (PredTy p) = PredTy (deNotePredType p)
704 deNoteType (NoteTy _ ty) = deNoteType ty
705 deNoteType (AppTy fun arg) = AppTy (deNoteType fun) (deNoteType arg)
706 deNoteType (FunTy fun arg) = FunTy (deNoteType fun) (deNoteType arg)
707 deNoteType (ForAllTy tv ty) = ForAllTy tv (deNoteType ty)
709 deNotePredType :: PredType -> PredType
710 deNotePredType (ClassP c tys) = ClassP c (map deNoteType tys)
711 deNotePredType (IParam n ty) = IParam n (deNoteType ty)
714 Find the free tycons and classes of a type. This is used in the front
718 tyClsNamesOfType :: Type -> NameSet
719 tyClsNamesOfType (TyVarTy tv) = emptyNameSet
720 tyClsNamesOfType (TyConApp tycon tys) = unitNameSet (getName tycon) `unionNameSets` tyClsNamesOfTypes tys
721 tyClsNamesOfType (NewTcApp tycon tys) = unitNameSet (getName tycon) `unionNameSets` tyClsNamesOfTypes tys
722 tyClsNamesOfType (NoteTy (SynNote ty1) ty2) = tyClsNamesOfType ty1
723 tyClsNamesOfType (NoteTy other_note ty2) = tyClsNamesOfType ty2
724 tyClsNamesOfType (PredTy (IParam n ty)) = tyClsNamesOfType ty
725 tyClsNamesOfType (PredTy (ClassP cl tys)) = unitNameSet (getName cl) `unionNameSets` tyClsNamesOfTypes tys
726 tyClsNamesOfType (FunTy arg res) = tyClsNamesOfType arg `unionNameSets` tyClsNamesOfType res
727 tyClsNamesOfType (AppTy fun arg) = tyClsNamesOfType fun `unionNameSets` tyClsNamesOfType arg
728 tyClsNamesOfType (ForAllTy tyvar ty) = tyClsNamesOfType ty
730 tyClsNamesOfTypes tys = foldr (unionNameSets . tyClsNamesOfType) emptyNameSet tys
732 tyClsNamesOfDFunHead :: Type -> NameSet
733 -- Find the free type constructors and classes
734 -- of the head of the dfun instance type
735 -- The 'dfun_head_type' is because of
736 -- instance Foo a => Baz T where ...
737 -- The decl is an orphan if Baz and T are both not locally defined,
738 -- even if Foo *is* locally defined
739 tyClsNamesOfDFunHead dfun_ty
740 = case tcSplitSigmaTy dfun_ty of
741 (tvs,_,head_ty) -> tyClsNamesOfType head_ty
743 classesOfTheta :: ThetaType -> [Class]
744 -- Looks just for ClassP things; maybe it should check
745 classesOfTheta preds = [ c | ClassP c _ <- preds ]
749 %************************************************************************
751 \subsection[TysWiredIn-ext-type]{External types}
753 %************************************************************************
755 The compiler's foreign function interface supports the passing of a
756 restricted set of types as arguments and results (the restricting factor
760 isFFIArgumentTy :: DynFlags -> Safety -> Type -> Bool
761 -- Checks for valid argument type for a 'foreign import'
762 isFFIArgumentTy dflags safety ty
763 = checkRepTyCon (legalOutgoingTyCon dflags safety) ty
765 isFFIExternalTy :: Type -> Bool
766 -- Types that are allowed as arguments of a 'foreign export'
767 isFFIExternalTy ty = checkRepTyCon legalFEArgTyCon ty
769 isFFIImportResultTy :: DynFlags -> Type -> Bool
770 isFFIImportResultTy dflags ty
771 = checkRepTyCon (legalFIResultTyCon dflags) ty
773 isFFIExportResultTy :: Type -> Bool
774 isFFIExportResultTy ty = checkRepTyCon legalFEResultTyCon ty
776 isFFIDynArgumentTy :: Type -> Bool
777 -- The argument type of a foreign import dynamic must be Ptr, FunPtr, Addr,
778 -- or a newtype of either.
779 isFFIDynArgumentTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey, addrTyConKey]
781 isFFIDynResultTy :: Type -> Bool
782 -- The result type of a foreign export dynamic must be Ptr, FunPtr, Addr,
783 -- or a newtype of either.
784 isFFIDynResultTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey, addrTyConKey]
786 isFFILabelTy :: Type -> Bool
787 -- The type of a foreign label must be Ptr, FunPtr, Addr,
788 -- or a newtype of either.
789 isFFILabelTy = checkRepTyConKey [ptrTyConKey, funPtrTyConKey, addrTyConKey]
791 isFFIDotnetTy :: DynFlags -> Type -> Bool
792 isFFIDotnetTy dflags ty
793 = checkRepTyCon (\ tc -> not (isByteArrayLikeTyCon tc) &&
794 (legalFIResultTyCon dflags tc ||
795 isFFIDotnetObjTy ty || isStringTy ty)) ty
797 -- Support String as an argument or result from a .NET FFI call.
799 case tcSplitTyConApp_maybe (repType ty) of
802 case tcSplitTyConApp_maybe (repType arg_ty) of
803 Just (cc,[]) -> cc == charTyCon
807 -- Support String as an argument or result from a .NET FFI call.
808 isFFIDotnetObjTy ty =
810 (_, t_ty) = tcSplitForAllTys ty
812 case tcSplitTyConApp_maybe (repType t_ty) of
813 Just (tc, [arg_ty]) | getName tc == objectTyConName -> True
816 toDNType :: Type -> DNType
818 | isStringTy ty = DNString
819 | isFFIDotnetObjTy ty = DNObject
820 | Just (tc,argTys) <- tcSplitTyConApp_maybe ty =
821 case lookup (getUnique tc) dn_assoc of
824 | tc `hasKey` ioTyConKey -> toDNType (head argTys)
825 | otherwise -> pprPanic ("toDNType: unsupported .NET type") (pprType ty <+> parens (hcat (map pprType argTys)) <+> ppr tc)
827 dn_assoc :: [ (Unique, DNType) ]
828 dn_assoc = [ (unitTyConKey, DNUnit)
829 , (intTyConKey, DNInt)
830 , (int8TyConKey, DNInt8)
831 , (int16TyConKey, DNInt16)
832 , (int32TyConKey, DNInt32)
833 , (int64TyConKey, DNInt64)
834 , (wordTyConKey, DNInt)
835 , (word8TyConKey, DNWord8)
836 , (word16TyConKey, DNWord16)
837 , (word32TyConKey, DNWord32)
838 , (word64TyConKey, DNWord64)
839 , (floatTyConKey, DNFloat)
840 , (doubleTyConKey, DNDouble)
841 , (addrTyConKey, DNPtr)
842 , (ptrTyConKey, DNPtr)
843 , (funPtrTyConKey, DNPtr)
844 , (charTyConKey, DNChar)
845 , (boolTyConKey, DNBool)
848 checkRepTyCon :: (TyCon -> Bool) -> Type -> Bool
849 -- Look through newtypes
850 -- Non-recursive ones are transparent to splitTyConApp,
851 -- but recursive ones aren't
852 checkRepTyCon check_tc ty
853 | Just (tc,_) <- splitTyConApp_maybe (repType ty) = check_tc tc
856 checkRepTyConKey :: [Unique] -> Type -> Bool
857 -- Like checkRepTyCon, but just looks at the TyCon key
858 checkRepTyConKey keys
859 = checkRepTyCon (\tc -> tyConUnique tc `elem` keys)
862 ----------------------------------------------
863 These chaps do the work; they are not exported
864 ----------------------------------------------
867 legalFEArgTyCon :: TyCon -> Bool
868 -- It's illegal to return foreign objects and (mutable)
869 -- bytearrays from a _ccall_ / foreign declaration
870 -- (or be passed them as arguments in foreign exported functions).
872 | isByteArrayLikeTyCon tc
874 -- It's also illegal to make foreign exports that take unboxed
875 -- arguments. The RTS API currently can't invoke such things. --SDM 7/2000
877 = boxedMarshalableTyCon tc
879 legalFIResultTyCon :: DynFlags -> TyCon -> Bool
880 legalFIResultTyCon dflags tc
881 | isByteArrayLikeTyCon tc = False
882 | tc == unitTyCon = True
883 | otherwise = marshalableTyCon dflags tc
885 legalFEResultTyCon :: TyCon -> Bool
886 legalFEResultTyCon tc
887 | isByteArrayLikeTyCon tc = False
888 | tc == unitTyCon = True
889 | otherwise = boxedMarshalableTyCon tc
891 legalOutgoingTyCon :: DynFlags -> Safety -> TyCon -> Bool
892 -- Checks validity of types going from Haskell -> external world
893 legalOutgoingTyCon dflags safety tc
894 | playSafe safety && isByteArrayLikeTyCon tc
897 = marshalableTyCon dflags tc
899 marshalableTyCon dflags tc
900 = (dopt Opt_GlasgowExts dflags && isUnLiftedTyCon tc)
901 || boxedMarshalableTyCon tc
903 boxedMarshalableTyCon tc
904 = getUnique tc `elem` [ intTyConKey, int8TyConKey, int16TyConKey
905 , int32TyConKey, int64TyConKey
906 , wordTyConKey, word8TyConKey, word16TyConKey
907 , word32TyConKey, word64TyConKey
908 , floatTyConKey, doubleTyConKey
909 , addrTyConKey, ptrTyConKey, funPtrTyConKey
912 , byteArrayTyConKey, mutableByteArrayTyConKey
916 isByteArrayLikeTyCon :: TyCon -> Bool
917 isByteArrayLikeTyCon tc =
918 getUnique tc `elem` [byteArrayTyConKey, mutableByteArrayTyConKey]
922 %************************************************************************
924 \subsection{Unification with an explicit substitution}
926 %************************************************************************
928 Unify types with an explicit substitution and no monad.
929 Ignore usage annotations.
933 = (TyVarSet, -- Set of template tyvars
934 TyVarSubstEnv) -- Not necessarily idempotent
936 unifyTysX :: TyVarSet -- Template tyvars
939 -> Maybe TyVarSubstEnv
940 unifyTysX tmpl_tyvars ty1 ty2
941 = uTysX ty1 ty2 (\(_,s) -> Just s) (tmpl_tyvars, emptySubstEnv)
943 unifyExtendTysX :: TyVarSet -- Template tyvars
944 -> TyVarSubstEnv -- Substitution to start with
947 -> Maybe TyVarSubstEnv -- Extended substitution
948 unifyExtendTysX tmpl_tyvars subst ty1 ty2
949 = uTysX ty1 ty2 (\(_,s) -> Just s) (tmpl_tyvars, subst)
951 unifyTyListsX :: TyVarSet -> [Type] -> [Type]
952 -> Maybe TyVarSubstEnv
953 unifyTyListsX tmpl_tyvars tys1 tys2
954 = uTyListsX tys1 tys2 (\(_,s) -> Just s) (tmpl_tyvars, emptySubstEnv)
959 -> (MySubst -> Maybe result)
963 uTysX (NoteTy _ ty1) ty2 k subst = uTysX ty1 ty2 k subst
964 uTysX ty1 (NoteTy _ ty2) k subst = uTysX ty1 ty2 k subst
966 -- Variables; go for uVar
967 uTysX (TyVarTy tyvar1) (TyVarTy tyvar2) k subst
970 uTysX (TyVarTy tyvar1) ty2 k subst@(tmpls,_)
971 | tyvar1 `elemVarSet` tmpls
972 = uVarX tyvar1 ty2 k subst
973 uTysX ty1 (TyVarTy tyvar2) k subst@(tmpls,_)
974 | tyvar2 `elemVarSet` tmpls
975 = uVarX tyvar2 ty1 k subst
978 uTysX (PredTy (IParam n1 t1)) (PredTy (IParam n2 t2)) k subst
979 | n1 == n2 = uTysX t1 t2 k subst
980 uTysX (PredTy (ClassP c1 tys1)) (PredTy (ClassP c2 tys2)) k subst
981 | c1 == c2 = uTyListsX tys1 tys2 k subst
983 -- Functions; just check the two parts
984 uTysX (FunTy fun1 arg1) (FunTy fun2 arg2) k subst
985 = uTysX fun1 fun2 (uTysX arg1 arg2 k) subst
987 -- Type constructors must match
988 uTysX (NewTcApp tc1 tys1) (NewTcApp tc2 tys2) k subst
989 | tc1 == tc2 = uTyListsX tys1 tys2 k subst
990 uTysX (TyConApp con1 tys1) (TyConApp con2 tys2) k subst
991 | (con1 == con2 && equalLength tys1 tys2)
992 = uTyListsX tys1 tys2 k subst
994 -- Applications need a bit of care!
995 -- They can match FunTy and TyConApp, so use splitAppTy_maybe
996 -- NB: we've already dealt with type variables and Notes,
997 -- so if one type is an App the other one jolly well better be too
998 uTysX (AppTy s1 t1) ty2 k subst
999 = case tcSplitAppTy_maybe ty2 of
1000 Just (s2, t2) -> uTysX s1 s2 (uTysX t1 t2 k) subst
1001 Nothing -> Nothing -- Fail
1003 uTysX ty1 (AppTy s2 t2) k subst
1004 = case tcSplitAppTy_maybe ty1 of
1005 Just (s1, t1) -> uTysX s1 s2 (uTysX t1 t2 k) subst
1006 Nothing -> Nothing -- Fail
1008 -- Not expecting for-alls in unification
1010 uTysX (ForAllTy _ _) ty2 k subst = panic "Unify.uTysX subst:ForAllTy (1st arg)"
1011 uTysX ty1 (ForAllTy _ _) k subst = panic "Unify.uTysX subst:ForAllTy (2nd arg)"
1014 -- Anything else fails
1015 uTysX ty1 ty2 k subst = Nothing
1018 uTyListsX [] [] k subst = k subst
1019 uTyListsX (ty1:tys1) (ty2:tys2) k subst = uTysX ty1 ty2 (uTyListsX tys1 tys2 k) subst
1020 uTyListsX tys1 tys2 k subst = Nothing -- Fail if the lists are different lengths
1024 -- Invariant: tv1 is a unifiable variable
1025 uVarX tv1 ty2 k subst@(tmpls, env)
1026 = case lookupSubstEnv env tv1 of
1027 Just (DoneTy ty1) -> -- Already bound
1028 uTysX ty1 ty2 k subst
1030 Nothing -- Not already bound
1031 | typeKind ty2 `eqKind` tyVarKind tv1
1032 && occur_check_ok ty2
1033 -> -- No kind mismatch nor occur check
1034 k (tmpls, extendSubstEnv env tv1 (DoneTy ty2))
1036 | otherwise -> Nothing -- Fail if kind mis-match or occur check
1038 occur_check_ok ty = all occur_check_ok_tv (varSetElems (tyVarsOfType ty))
1039 occur_check_ok_tv tv | tv1 == tv = False
1040 | otherwise = case lookupSubstEnv env tv of
1042 Just (DoneTy ty) -> occur_check_ok ty
1047 %************************************************************************
1049 \subsection{Matching on types}
1051 %************************************************************************
1053 Matching is a {\em unidirectional} process, matching a type against a
1054 template (which is just a type with type variables in it). The
1055 matcher assumes that there are no repeated type variables in the
1056 template, so that it simply returns a mapping of type variables to
1057 types. It also fails on nested foralls.
1059 @matchTys@ matches corresponding elements of a list of templates and
1060 types. It and @matchTy@ both ignore usage annotations, unlike the
1061 main function @match@.
1064 matchTy :: TyVarSet -- Template tyvars
1066 -> Type -- Proposed instance of template
1067 -> Maybe TyVarSubstEnv -- Matching substitution
1070 matchTys :: TyVarSet -- Template tyvars
1071 -> [Type] -- Templates
1072 -> [Type] -- Proposed instance of template
1073 -> Maybe (TyVarSubstEnv, -- Matching substitution
1074 [Type]) -- Left over instance types
1076 matchTy tmpls ty1 ty2 = match ty1 ty2 tmpls (\ senv -> Just senv) emptySubstEnv
1078 matchTys tmpls tys1 tys2 = match_list tys1 tys2 tmpls
1079 (\ (senv,tys) -> Just (senv,tys))
1083 @match@ is the main function. It takes a flag indicating whether
1084 usage annotations are to be respected.
1087 match :: Type -> Type -- Current match pair
1088 -> TyVarSet -- Template vars
1089 -> (TyVarSubstEnv -> Maybe result) -- Continuation
1090 -> TyVarSubstEnv -- Current subst
1093 -- When matching against a type variable, see if the variable
1094 -- has already been bound. If so, check that what it's bound to
1095 -- is the same as ty; if not, bind it and carry on.
1097 match (TyVarTy v) ty tmpls k senv
1098 | v `elemVarSet` tmpls
1099 = -- v is a template variable
1100 case lookupSubstEnv senv v of
1101 Nothing | typeKind ty `eqKind` tyVarKind v
1102 -- We do a kind check, just as in the uVarX above
1103 -- The kind check is needed to avoid bogus matches
1104 -- of (a b) with (c d), where the kinds don't match
1105 -- An occur check isn't needed when matching.
1106 -> k (extendSubstEnv senv v (DoneTy ty))
1108 | otherwise -> Nothing -- Fails
1110 Just (DoneTy ty') | ty' `tcEqType` ty -> k senv -- Succeeds
1111 | otherwise -> Nothing -- Fails
1114 = -- v is not a template variable; ty had better match
1115 -- Can't use (==) because types differ
1116 case tcGetTyVar_maybe ty of
1117 Just v' | v == v' -> k senv -- Success
1118 other -> Nothing -- Failure
1119 -- This tcGetTyVar_maybe is *required* because it must strip Notes.
1120 -- I guess the reason the Note-stripping case is *last* rather than first
1121 -- is to preserve type synonyms etc., so I'm not moving it to the
1122 -- top; but this means that (without the deNotetype) a type
1123 -- variable may not match the pattern (TyVarTy v') as one would
1124 -- expect, due to an intervening Note. KSW 2000-06.
1127 match (PredTy (IParam n1 t1)) (PredTy (IParam n2 t2)) tmpls k senv
1128 | n1 == n2 = match t1 t2 tmpls k senv
1129 match (PredTy (ClassP c1 tys1)) (PredTy (ClassP c2 tys2)) tmpls k senv
1130 | c1 == c2 = match_list_exactly tys1 tys2 tmpls k senv
1132 -- Functions; just check the two parts
1133 match (FunTy arg1 res1) (FunTy arg2 res2) tmpls k senv
1134 = match arg1 arg2 tmpls (match res1 res2 tmpls k) senv
1136 match (AppTy fun1 arg1) ty2 tmpls k senv
1137 = case tcSplitAppTy_maybe ty2 of
1138 Just (fun2,arg2) -> match fun1 fun2 tmpls (match arg1 arg2 tmpls k) senv
1139 Nothing -> Nothing -- Fail
1141 -- Newtypes are opaque; predicate types should not happen
1142 match (NewTcApp tc1 tys1) (NewTcApp tc2 tys2) tmpls k senv
1143 | tc1 == tc2 = match_list_exactly tys1 tys2 tmpls k senv
1144 match (TyConApp tc1 tys1) (TyConApp tc2 tys2) tmpls k senv
1145 | tc1 == tc2 = match_list_exactly tys1 tys2 tmpls k senv
1147 -- With type synonyms, we have to be careful for the exact
1148 -- same reasons as in the unifier. Please see the
1149 -- considerable commentary there before changing anything
1150 -- here! (WDP 95/05)
1151 match (NoteTy n1 ty1) ty2 tmpls k senv = match ty1 ty2 tmpls k senv
1152 match ty1 (NoteTy n2 ty2) tmpls k senv = match ty1 ty2 tmpls k senv
1155 match _ _ _ _ _ = Nothing
1157 match_list_exactly tys1 tys2 tmpls k senv
1158 = match_list tys1 tys2 tmpls k' senv
1160 k' (senv', tys2') | null tys2' = k senv' -- Succeed
1161 | otherwise = Nothing -- Fail
1163 match_list [] tys2 tmpls k senv = k (senv, tys2)
1164 match_list (ty1:tys1) [] tmpls k senv = Nothing -- Not enough arg tys => failure
1165 match_list (ty1:tys1) (ty2:tys2) tmpls k senv
1166 = match ty1 ty2 tmpls (match_list tys1 tys2 tmpls k) senv