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,
50 ---------------------------------
51 -- Misc type manipulators
52 hoistForAllTys, deNoteType,
53 namesOfType, namesOfDFunHead,
56 ---------------------------------
58 PredType, getClassPredTys_maybe, getClassPredTys,
59 isPredTy, isClassPred, isTyVarClassPred, predHasFDs,
60 mkDictTy, tcSplitPredTy_maybe, predTyUnique,
61 isDictTy, tcSplitDFunTy, predTyUnique,
62 mkClassPred, inheritablePred, isIPPred, mkPredName,
64 ---------------------------------
65 -- Foreign import and export
66 isFFIArgumentTy, -- :: DynFlags -> Safety -> Type -> Bool
67 isFFIImportResultTy, -- :: DynFlags -> Type -> Bool
68 isFFIExportResultTy, -- :: Type -> Bool
69 isFFIExternalTy, -- :: Type -> Bool
70 isFFIDynArgumentTy, -- :: Type -> Bool
71 isFFIDynResultTy, -- :: Type -> Bool
72 isFFILabelTy, -- :: Type -> Bool
74 ---------------------------------
75 -- Unifier and matcher
76 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,
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
111 import Type ( mkUTyM, unUTy ) -- Used locally
113 import Type ( -- Re-exports
114 tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tyVarsOfTheta,
115 Kind, Type, SourceType(..), PredType, ThetaType,
116 unliftedTypeKind, liftedTypeKind, openTypeKind, mkArrowKind, mkArrowKinds,
117 mkForAllTy, mkForAllTys, defaultKind, isTypeKind,
118 mkFunTy, mkFunTys, zipFunTys,
119 mkTyConApp, mkAppTy, mkAppTys, mkSynTy, applyTy, applyTys,
120 mkTyVarTy, mkTyVarTys, mkTyConTy, mkPredTy, mkPredTys,
121 isUnLiftedType, isUnboxedTupleType, isPrimitiveType,
122 splitNewType_maybe, splitTyConApp_maybe,
123 tidyTopType, tidyType, tidyPred, tidyTypes, tidyFreeTyVars, tidyOpenType, tidyOpenTypes,
124 tidyTyVarBndr, tidyOpenTyVar, tidyOpenTyVars, eqKind, eqUsage,
125 hasMoreBoxityInfo, liftedBoxity, superBoxity, typeKind, superKind
127 import TyCon ( TyCon, isUnLiftedTyCon )
128 import Class ( classHasFDs, Class )
129 import Var ( TyVar, tyVarKind, isMutTyVar, mutTyVarDetails )
130 import ForeignCall ( Safety, playSafe )
135 import CmdLineOpts ( DynFlags, DynFlag( Opt_GlasgowExts ), dopt )
136 import Name ( Name, NamedThing(..), mkLocalName, getSrcLoc )
137 import OccName ( OccName, mkDictOcc )
139 import PrelNames -- Lots (e.g. in isFFIArgumentTy)
140 import TysWiredIn ( ptrTyCon, funPtrTyCon, addrTyCon, unitTyCon )
141 import BasicTypes ( ipNameName )
142 import Unique ( Unique, Uniquable(..) )
143 import SrcLoc ( SrcLoc )
144 import Util ( cmpList, thenCmp, equalLength )
145 import Maybes ( maybeToBool, expectJust )
150 %************************************************************************
154 %************************************************************************
156 The type checker divides the generic Type world into the
157 following more structured beasts:
159 sigma ::= forall tyvars. theta => phi
160 -- A sigma type is a qualified type
162 -- Note that even if 'tyvars' is empty, theta
163 -- may not be: e.g. (?x::Int) => Int
165 -- Note that 'sigma' is in prenex form:
166 -- all the foralls are at the front.
167 -- A 'phi' type has no foralls to the right of
173 -- A 'tau' type has no quantification anywhere
174 -- Note that the args of a type constructor must be taus
176 | tycon tau_1 .. tau_n
180 -- In all cases, a (saturated) type synonym application is legal,
181 -- provided it expands to the required form.
185 type SigmaType = Type
191 type TcTyVar = TyVar -- Might be a mutable tyvar
192 type TcTyVarSet = TyVarSet
194 type TcType = Type -- A TcType can have mutable type variables
195 -- Invariant on ForAllTy in TcTypes:
197 -- a cannot occur inside a MutTyVar in T; that is,
198 -- T is "flattened" before quantifying over a
200 type TcPredType = PredType
201 type TcThetaType = ThetaType
202 type TcSigmaType = TcType
203 type TcPhiType = TcType
204 type TcTauType = TcType
209 %************************************************************************
211 \subsection{TyVarDetails}
213 %************************************************************************
215 TyVarDetails gives extra info about type variables, used during type
216 checking. It's attached to mutable type variables only.
217 It's knot-tied back to Var.lhs. There is no reason in principle
218 why Var.lhs shouldn't actually have the definition, but it "belongs" here.
222 = HoleTv -- Used *only* by the type checker when passing in a type
223 -- variable that should be side-effected to the result type.
224 -- Always has kind openTypeKind.
225 -- Never appears in types
227 | SigTv -- Introduced when instantiating a type signature,
228 -- prior to checking that the defn of a fn does
229 -- have the expected type. Should not be instantiated.
231 -- f :: forall a. a -> a
233 -- When checking e, with expected type (a->a), we
234 -- should not instantiate a
236 | ClsTv -- Scoped type variable introduced by a class decl
237 -- class C a where ...
239 | InstTv -- Ditto, but instance decl
241 | PatSigTv -- Scoped type variable, introduced by a pattern
245 | VanillaTv -- Everything else
247 isUserTyVar :: TcTyVar -> Bool -- Avoid unifying these if possible
248 isUserTyVar tv = case mutTyVarDetails tv of
252 isSkolemTyVar :: TcTyVar -> Bool
253 isSkolemTyVar tv = case mutTyVarDetails tv of
257 isHoleTyVar :: TcTyVar -> Bool
258 -- NB: the hole might be filled in by now, and this
259 -- function does not check for that
260 isHoleTyVar tv = ASSERT( isMutTyVar tv )
261 case mutTyVarDetails tv of
265 tyVarBindingInfo :: TyVar -> SDoc -- Used in checkSigTyVars
268 = sep [ptext SLIT("is bound by the") <+> details (mutTyVarDetails tv),
269 ptext SLIT("at") <+> ppr (getSrcLoc tv)]
273 details SigTv = ptext SLIT("type signature")
274 details ClsTv = ptext SLIT("class declaration")
275 details InstTv = ptext SLIT("instance declaration")
276 details PatSigTv = ptext SLIT("pattern type signature")
277 details HoleTv = ptext SLIT("//hole//") -- Should not happen
278 details VanillaTv = ptext SLIT("//vanilla//") -- Ditto
282 %************************************************************************
284 \subsection{Tau, sigma and rho}
286 %************************************************************************
289 mkSigmaTy tyvars theta tau = mkForAllTys tyvars (mkRhoTy theta tau)
291 mkRhoTy :: [SourceType] -> Type -> Type
292 mkRhoTy theta ty = UASSERT2( not (isUTy ty), pprType ty )
293 foldr (\p r -> FunTy (mkUTyM (mkPredTy p)) (mkUTyM r)) ty theta
298 @isTauTy@ tests for nested for-alls.
301 isTauTy :: Type -> Bool
302 isTauTy (TyVarTy v) = True
303 isTauTy (TyConApp _ tys) = all isTauTy tys
304 isTauTy (AppTy a b) = isTauTy a && isTauTy b
305 isTauTy (FunTy a b) = isTauTy a && isTauTy b
306 isTauTy (SourceTy p) = True -- Don't look through source types
307 isTauTy (NoteTy _ ty) = isTauTy ty
308 isTauTy (UsageTy _ ty) = isTauTy ty
309 isTauTy other = False
313 getDFunTyKey :: Type -> OccName -- Get some string from a type, to be used to
314 -- construct a dictionary function name
315 getDFunTyKey (TyVarTy tv) = getOccName tv
316 getDFunTyKey (TyConApp tc _) = getOccName tc
317 getDFunTyKey (AppTy fun _) = getDFunTyKey fun
318 getDFunTyKey (NoteTy _ t) = getDFunTyKey t
319 getDFunTyKey (FunTy arg _) = getOccName funTyCon
320 getDFunTyKey (ForAllTy _ t) = getDFunTyKey t
321 getDFunTyKey (UsageTy _ t) = getDFunTyKey t
322 getDFunTyKey (SourceTy (NType tc _)) = getOccName tc -- Newtypes are quite reasonable
323 getDFunTyKey ty = pprPanic "getDFunTyKey" (pprType ty)
324 -- SourceTy shouldn't happen
328 %************************************************************************
330 \subsection{Expanding and splitting}
332 %************************************************************************
334 These tcSplit functions are like their non-Tc analogues, but
335 a) they do not look through newtypes
336 b) they do not look through PredTys
337 c) [future] they ignore usage-type annotations
339 However, they are non-monadic and do not follow through mutable type
340 variables. It's up to you to make sure this doesn't matter.
343 tcSplitForAllTys :: Type -> ([TyVar], Type)
344 tcSplitForAllTys ty = split ty ty []
346 split orig_ty (ForAllTy tv ty) tvs = split ty ty (tv:tvs)
347 split orig_ty (NoteTy n ty) tvs = split orig_ty ty tvs
348 split orig_ty (UsageTy _ ty) tvs = split orig_ty ty tvs
349 split orig_ty t tvs = (reverse tvs, orig_ty)
351 tcIsForAllTy (ForAllTy tv ty) = True
352 tcIsForAllTy (NoteTy n ty) = tcIsForAllTy ty
353 tcIsForAllTy (UsageTy n ty) = tcIsForAllTy ty
354 tcIsForAllTy t = False
356 tcSplitRhoTy :: Type -> ([PredType], Type)
357 tcSplitRhoTy ty = split ty ty []
359 split orig_ty (FunTy arg res) ts = case tcSplitPredTy_maybe arg of
360 Just p -> split res res (p:ts)
361 Nothing -> (reverse ts, orig_ty)
362 split orig_ty (NoteTy n ty) ts = split orig_ty ty ts
363 split orig_ty (UsageTy _ ty) ts = split orig_ty ty ts
364 split orig_ty ty ts = (reverse ts, orig_ty)
366 tcSplitSigmaTy ty = case tcSplitForAllTys ty of
367 (tvs, rho) -> case tcSplitRhoTy rho of
368 (theta, tau) -> (tvs, theta, tau)
370 tcTyConAppTyCon :: Type -> TyCon
371 tcTyConAppTyCon ty = fst (tcSplitTyConApp ty)
373 tcTyConAppArgs :: Type -> [Type]
374 tcTyConAppArgs ty = snd (tcSplitTyConApp ty)
376 tcSplitTyConApp :: Type -> (TyCon, [Type])
377 tcSplitTyConApp ty = case tcSplitTyConApp_maybe ty of
379 Nothing -> pprPanic "tcSplitTyConApp" (pprType ty)
381 tcSplitTyConApp_maybe :: Type -> Maybe (TyCon, [Type])
382 -- Newtypes are opaque, so they may be split
383 tcSplitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
384 tcSplitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [unUTy arg,unUTy res])
385 tcSplitTyConApp_maybe (NoteTy n ty) = tcSplitTyConApp_maybe ty
386 tcSplitTyConApp_maybe (UsageTy _ ty) = tcSplitTyConApp_maybe ty
387 tcSplitTyConApp_maybe (SourceTy (NType tc tys)) = Just (tc,tys)
388 -- However, predicates are not treated
389 -- as tycon applications by the type checker
390 tcSplitTyConApp_maybe other = Nothing
392 tcSplitFunTys :: Type -> ([Type], Type)
393 tcSplitFunTys ty = case tcSplitFunTy_maybe ty of
395 Just (arg,res) -> (arg:args, res')
397 (args,res') = tcSplitFunTys res
399 tcSplitFunTy_maybe :: Type -> Maybe (Type, Type)
400 tcSplitFunTy_maybe (FunTy arg res) = Just (arg, res)
401 tcSplitFunTy_maybe (NoteTy n ty) = tcSplitFunTy_maybe ty
402 tcSplitFunTy_maybe (UsageTy _ ty) = tcSplitFunTy_maybe ty
403 tcSplitFunTy_maybe other = Nothing
405 tcFunArgTy ty = case tcSplitFunTy_maybe ty of { Just (arg,res) -> arg }
406 tcFunResultTy ty = case tcSplitFunTy_maybe ty of { Just (arg,res) -> res }
409 tcSplitAppTy_maybe :: Type -> Maybe (Type, Type)
410 tcSplitAppTy_maybe (FunTy ty1 ty2) = Just (TyConApp funTyCon [unUTy ty1], unUTy ty2)
411 tcSplitAppTy_maybe (AppTy ty1 ty2) = Just (ty1, ty2)
412 tcSplitAppTy_maybe (NoteTy n ty) = tcSplitAppTy_maybe ty
413 tcSplitAppTy_maybe (UsageTy _ ty) = tcSplitAppTy_maybe ty
414 tcSplitAppTy_maybe (SourceTy (NType tc tys)) = tc_split_app tc tys
415 --- Don't forget that newtype!
416 tcSplitAppTy_maybe (TyConApp tc tys) = tc_split_app tc tys
417 tcSplitAppTy_maybe other = Nothing
419 tc_split_app tc [] = Nothing
420 tc_split_app tc tys = split tys []
422 split [ty2] acc = Just (TyConApp tc (reverse acc), ty2)
423 split (ty:tys) acc = split tys (ty:acc)
425 tcSplitAppTy ty = case tcSplitAppTy_maybe ty of
427 Nothing -> pprPanic "tcSplitAppTy" (pprType ty)
429 tcGetTyVar_maybe :: Type -> Maybe TyVar
430 tcGetTyVar_maybe (TyVarTy tv) = Just tv
431 tcGetTyVar_maybe (NoteTy _ t) = tcGetTyVar_maybe t
432 tcGetTyVar_maybe ty@(UsageTy _ _) = pprPanic "tcGetTyVar_maybe: UTy:" (pprType ty)
433 tcGetTyVar_maybe other = Nothing
435 tcGetTyVar :: String -> Type -> TyVar
436 tcGetTyVar msg ty = expectJust msg (tcGetTyVar_maybe ty)
438 tcIsTyVarTy :: Type -> Bool
439 tcIsTyVarTy ty = maybeToBool (tcGetTyVar_maybe ty)
442 The type of a method for class C is always of the form:
443 Forall a1..an. C a1..an => sig_ty
444 where sig_ty is the type given by the method's signature, and thus in general
445 is a ForallTy. At the point that splitMethodTy is called, it is expected
446 that the outer Forall has already been stripped off. splitMethodTy then
447 returns (C a1..an, sig_ty') where sig_ty' is sig_ty with any Notes or
451 tcSplitMethodTy :: Type -> (PredType, Type)
452 tcSplitMethodTy ty = split ty
454 split (FunTy arg res) = case tcSplitPredTy_maybe arg of
456 Nothing -> panic "splitMethodTy"
457 split (NoteTy n ty) = split ty
458 split (UsageTy _ ty) = split ty
459 split _ = panic "splitMethodTy"
461 tcSplitDFunTy :: Type -> ([TyVar], [SourceType], Class, [Type])
462 -- Split the type of a dictionary function
464 = case tcSplitSigmaTy ty of { (tvs, theta, tau) ->
465 case tcSplitPredTy_maybe tau of { Just (ClassP clas tys) ->
466 (tvs, theta, clas, tys) }}
470 %************************************************************************
472 \subsection{Predicate types}
474 %************************************************************************
476 "Predicates" are particular source types, namelyClassP or IParams
479 isPred :: SourceType -> Bool
480 isPred (ClassP _ _) = True
481 isPred (IParam _ _) = True
482 isPred (NType _ _) = False
484 isPredTy :: Type -> Bool
485 isPredTy (NoteTy _ ty) = isPredTy ty
486 isPredTy (UsageTy _ ty) = isPredTy ty
487 isPredTy (SourceTy sty) = isPred sty
490 tcSplitPredTy_maybe :: Type -> Maybe PredType
491 -- Returns Just for predicates only
492 tcSplitPredTy_maybe (NoteTy _ ty) = tcSplitPredTy_maybe ty
493 tcSplitPredTy_maybe (UsageTy _ ty) = tcSplitPredTy_maybe ty
494 tcSplitPredTy_maybe (SourceTy p) | isPred p = Just p
495 tcSplitPredTy_maybe other = Nothing
497 predTyUnique :: PredType -> Unique
498 predTyUnique (IParam n _) = getUnique (ipNameName n)
499 predTyUnique (ClassP clas tys) = getUnique clas
501 predHasFDs :: PredType -> Bool
502 -- True if the predicate has functional depenencies;
503 -- I.e. should participate in improvement
504 predHasFDs (IParam _ _) = True
505 predHasFDs (ClassP cls _) = classHasFDs cls
507 mkPredName :: Unique -> SrcLoc -> SourceType -> Name
508 mkPredName uniq loc (ClassP cls tys) = mkLocalName uniq (mkDictOcc (getOccName cls)) loc
509 mkPredName uniq loc (IParam ip ty) = mkLocalName uniq (getOccName (ipNameName ip)) loc
513 --------------------- Dictionary types ---------------------------------
516 mkClassPred clas tys = UASSERT2( not (any isUTy tys), ppr clas <+> fsep (map pprType tys) )
519 isClassPred :: SourceType -> Bool
520 isClassPred (ClassP clas tys) = True
521 isClassPred other = False
523 isTyVarClassPred (ClassP clas tys) = all tcIsTyVarTy tys
524 isTyVarClassPred other = False
526 getClassPredTys_maybe :: SourceType -> Maybe (Class, [Type])
527 getClassPredTys_maybe (ClassP clas tys) = Just (clas, tys)
528 getClassPredTys_maybe _ = Nothing
530 getClassPredTys :: PredType -> (Class, [Type])
531 getClassPredTys (ClassP clas tys) = (clas, tys)
533 mkDictTy :: Class -> [Type] -> Type
534 mkDictTy clas tys = UASSERT2( not (any isUTy tys), ppr clas <+> fsep (map pprType tys) )
535 mkPredTy (ClassP clas tys)
537 isDictTy :: Type -> Bool
538 isDictTy (SourceTy p) = isClassPred p
539 isDictTy (NoteTy _ ty) = isDictTy ty
540 isDictTy (UsageTy _ ty) = isDictTy ty
541 isDictTy other = False
544 --------------------- Implicit parameters ---------------------------------
547 isIPPred :: SourceType -> Bool
548 isIPPred (IParam _ _) = True
549 isIPPred other = False
551 inheritablePred :: PredType -> Bool
552 -- Can be inherited by a context. For example, consider
553 -- f x = let g y = (?v, y+x)
554 -- in (g 3 with ?v = 8,
556 -- The point is that g's type must be quantifed over ?v:
557 -- g :: (?v :: a) => a -> a
558 -- but it doesn't need to be quantified over the Num a dictionary
559 -- which can be free in g's rhs, and shared by both calls to g
560 inheritablePred (ClassP _ _) = True
561 inheritablePred other = False
565 %************************************************************************
567 \subsection{Comparison}
569 %************************************************************************
571 Comparison, taking note of newtypes, predicates, etc,
572 But ignoring usage types
575 tcEqType :: Type -> Type -> Bool
576 tcEqType ty1 ty2 = case ty1 `tcCmpType` ty2 of { EQ -> True; other -> False }
578 tcEqTypes :: [Type] -> [Type] -> Bool
579 tcEqTypes ty1 ty2 = case ty1 `tcCmpTypes` ty2 of { EQ -> True; other -> False }
581 tcEqPred :: PredType -> PredType -> Bool
582 tcEqPred p1 p2 = case p1 `tcCmpPred` p2 of { EQ -> True; other -> False }
585 tcCmpType :: Type -> Type -> Ordering
586 tcCmpType ty1 ty2 = cmpTy emptyVarEnv ty1 ty2
588 tcCmpTypes tys1 tys2 = cmpTys emptyVarEnv tys1 tys2
590 tcCmpPred p1 p2 = cmpSourceTy emptyVarEnv p1 p2
592 cmpTys env tys1 tys2 = cmpList (cmpTy env) tys1 tys2
595 cmpTy :: TyVarEnv TyVar -> Type -> Type -> Ordering
596 -- The "env" maps type variables in ty1 to type variables in ty2
597 -- So when comparing for-alls.. (forall tv1 . t1) (forall tv2 . t2)
598 -- we in effect substitute tv2 for tv1 in t1 before continuing
600 -- Look through NoteTy and UsageTy
601 cmpTy env (NoteTy _ ty1) ty2 = cmpTy env ty1 ty2
602 cmpTy env ty1 (NoteTy _ ty2) = cmpTy env ty1 ty2
603 cmpTy env (UsageTy _ ty1) ty2 = cmpTy env ty1 ty2
604 cmpTy env ty1 (UsageTy _ ty2) = cmpTy env ty1 ty2
606 -- Deal with equal constructors
607 cmpTy env (TyVarTy tv1) (TyVarTy tv2) = case lookupVarEnv env tv1 of
608 Just tv1a -> tv1a `compare` tv2
609 Nothing -> tv1 `compare` tv2
611 cmpTy env (SourceTy p1) (SourceTy p2) = cmpSourceTy env p1 p2
612 cmpTy env (AppTy f1 a1) (AppTy f2 a2) = cmpTy env f1 f2 `thenCmp` cmpTy env a1 a2
613 cmpTy env (FunTy f1 a1) (FunTy f2 a2) = cmpTy env f1 f2 `thenCmp` cmpTy env a1 a2
614 cmpTy env (TyConApp tc1 tys1) (TyConApp tc2 tys2) = (tc1 `compare` tc2) `thenCmp` (cmpTys env tys1 tys2)
615 cmpTy env (ForAllTy tv1 t1) (ForAllTy tv2 t2) = cmpTy (extendVarEnv env tv1 tv2) t1 t2
617 -- Deal with the rest: TyVarTy < AppTy < FunTy < TyConApp < ForAllTy < SourceTy
618 cmpTy env (AppTy _ _) (TyVarTy _) = GT
620 cmpTy env (FunTy _ _) (TyVarTy _) = GT
621 cmpTy env (FunTy _ _) (AppTy _ _) = GT
623 cmpTy env (TyConApp _ _) (TyVarTy _) = GT
624 cmpTy env (TyConApp _ _) (AppTy _ _) = GT
625 cmpTy env (TyConApp _ _) (FunTy _ _) = GT
627 cmpTy env (ForAllTy _ _) (TyVarTy _) = GT
628 cmpTy env (ForAllTy _ _) (AppTy _ _) = GT
629 cmpTy env (ForAllTy _ _) (FunTy _ _) = GT
630 cmpTy env (ForAllTy _ _) (TyConApp _ _) = GT
632 cmpTy env (SourceTy _) t2 = GT
638 cmpSourceTy :: TyVarEnv TyVar -> SourceType -> SourceType -> Ordering
639 cmpSourceTy env (IParam n1 ty1) (IParam n2 ty2) = (n1 `compare` n2) `thenCmp` (cmpTy env ty1 ty2)
640 -- Compare types as well as names for implicit parameters
641 -- This comparison is used exclusively (I think) for the
642 -- finite map built in TcSimplify
643 cmpSourceTy env (IParam _ _) sty = LT
645 cmpSourceTy env (ClassP _ _) (IParam _ _) = GT
646 cmpSourceTy env (ClassP c1 tys1) (ClassP c2 tys2) = (c1 `compare` c2) `thenCmp` (cmpTys env tys1 tys2)
647 cmpSourceTy env (ClassP _ _) (NType _ _) = LT
649 cmpSourceTy env (NType tc1 tys1) (NType tc2 tys2) = (tc1 `compare` tc2) `thenCmp` (cmpTys env tys1 tys2)
650 cmpSourceTy env (NType _ _) sty = GT
653 PredTypes are used as a FM key in TcSimplify,
654 so we take the easy path and make them an instance of Ord
657 instance Eq SourceType where { (==) = tcEqPred }
658 instance Ord SourceType where { compare = tcCmpPred }
662 %************************************************************************
664 \subsection{Predicates}
666 %************************************************************************
668 isSigmaTy returns true of any qualified type. It doesn't *necessarily* have
670 f :: (?x::Int) => Int -> Int
673 isSigmaTy :: Type -> Bool
674 isSigmaTy (ForAllTy tyvar ty) = True
675 isSigmaTy (FunTy a b) = isPredTy a
676 isSigmaTy (NoteTy n ty) = isSigmaTy ty
677 isSigmaTy (UsageTy _ ty) = isSigmaTy ty
680 isOverloadedTy :: Type -> Bool
681 isOverloadedTy (ForAllTy tyvar ty) = isOverloadedTy ty
682 isOverloadedTy (FunTy a b) = isPredTy a
683 isOverloadedTy (NoteTy n ty) = isOverloadedTy ty
684 isOverloadedTy (UsageTy _ ty) = isOverloadedTy ty
685 isOverloadedTy _ = False
689 isFloatTy = is_tc floatTyConKey
690 isDoubleTy = is_tc doubleTyConKey
691 isForeignPtrTy = is_tc foreignPtrTyConKey
692 isIntegerTy = is_tc integerTyConKey
693 isIntTy = is_tc intTyConKey
694 isAddrTy = is_tc addrTyConKey
695 isBoolTy = is_tc boolTyConKey
696 isUnitTy = is_tc unitTyConKey
698 is_tc :: Unique -> Type -> Bool
699 -- Newtypes are opaque to this
700 is_tc uniq ty = case tcSplitTyConApp_maybe ty of
701 Just (tc, _) -> uniq == getUnique tc
706 %************************************************************************
710 %************************************************************************
713 hoistForAllTys :: Type -> Type
714 -- Move all the foralls to the top
715 -- e.g. T -> forall a. a ==> forall a. T -> a
716 -- Careful: LOSES USAGE ANNOTATIONS!
718 = case hoist ty of { (tvs, body) -> mkForAllTys tvs body }
720 hoist :: Type -> ([TyVar], Type)
721 hoist ty = case tcSplitFunTys ty of { (args, res) ->
722 case tcSplitForAllTys res of {
723 ([], body) -> ([], ty) ;
724 (tvs1, body1) -> case hoist body1 of { (tvs2,body2) ->
725 (tvs1 ++ tvs2, mkFunTys args body2)
731 deNoteType :: Type -> Type
732 -- Remove synonyms, but not source types
733 deNoteType ty@(TyVarTy tyvar) = ty
734 deNoteType (TyConApp tycon tys) = TyConApp tycon (map deNoteType tys)
735 deNoteType (SourceTy p) = SourceTy (deNoteSourceType p)
736 deNoteType (NoteTy _ ty) = deNoteType ty
737 deNoteType (AppTy fun arg) = AppTy (deNoteType fun) (deNoteType arg)
738 deNoteType (FunTy fun arg) = FunTy (deNoteType fun) (deNoteType arg)
739 deNoteType (ForAllTy tv ty) = ForAllTy tv (deNoteType ty)
740 deNoteType (UsageTy u ty) = UsageTy u (deNoteType ty)
742 deNoteSourceType :: SourceType -> SourceType
743 deNoteSourceType (ClassP c tys) = ClassP c (map deNoteType tys)
744 deNoteSourceType (IParam n ty) = IParam n (deNoteType ty)
745 deNoteSourceType (NType tc tys) = NType tc (map deNoteType tys)
748 Find the free names of a type, including the type constructors and classes it mentions
749 This is used in the front end of the compiler
752 namesOfType :: Type -> NameSet
753 namesOfType (TyVarTy tv) = unitNameSet (getName tv)
754 namesOfType (TyConApp tycon tys) = unitNameSet (getName tycon) `unionNameSets` namesOfTypes tys
755 namesOfType (NoteTy (SynNote ty1) ty2) = namesOfType ty1
756 namesOfType (NoteTy other_note ty2) = namesOfType ty2
757 namesOfType (SourceTy (IParam n ty)) = namesOfType ty
758 namesOfType (SourceTy (ClassP cl tys)) = unitNameSet (getName cl) `unionNameSets` namesOfTypes tys
759 namesOfType (SourceTy (NType tc tys)) = unitNameSet (getName tc) `unionNameSets` namesOfTypes tys
760 namesOfType (FunTy arg res) = namesOfType arg `unionNameSets` namesOfType res
761 namesOfType (AppTy fun arg) = namesOfType fun `unionNameSets` namesOfType arg
762 namesOfType (ForAllTy tyvar ty) = namesOfType ty `delFromNameSet` getName tyvar
763 namesOfType (UsageTy u ty) = namesOfType u `unionNameSets` namesOfType ty
765 namesOfTypes tys = foldr (unionNameSets . namesOfType) emptyNameSet tys
767 namesOfDFunHead :: Type -> NameSet
768 -- Find the free type constructors and classes
769 -- of the head of the dfun instance type
770 -- The 'dfun_head_type' is because of
771 -- instance Foo a => Baz T where ...
772 -- The decl is an orphan if Baz and T are both not locally defined,
773 -- even if Foo *is* locally defined
774 namesOfDFunHead dfun_ty = case tcSplitSigmaTy dfun_ty of
775 (tvs,_,head_ty) -> delListFromNameSet (namesOfType head_ty)
780 %************************************************************************
782 \subsection[TysWiredIn-ext-type]{External types}
784 %************************************************************************
786 The compiler's foreign function interface supports the passing of a
787 restricted set of types as arguments and results (the restricting factor
791 isFFIArgumentTy :: DynFlags -> Safety -> Type -> Bool
792 -- Checks for valid argument type for a 'foreign import'
793 isFFIArgumentTy dflags safety ty
794 = checkRepTyCon (legalOutgoingTyCon dflags safety) ty
796 isFFIExternalTy :: Type -> Bool
797 -- Types that are allowed as arguments of a 'foreign export'
798 isFFIExternalTy ty = checkRepTyCon legalFEArgTyCon ty
800 isFFIImportResultTy :: DynFlags -> Type -> Bool
801 isFFIImportResultTy dflags ty
802 = checkRepTyCon (legalFIResultTyCon dflags) ty
804 isFFIExportResultTy :: Type -> Bool
805 isFFIExportResultTy ty = checkRepTyCon legalFEResultTyCon ty
807 isFFIDynArgumentTy :: Type -> Bool
808 -- The argument type of a foreign import dynamic must be Ptr, FunPtr, Addr,
809 -- or a newtype of either.
810 isFFIDynArgumentTy = checkRepTyCon (\tc -> tc == ptrTyCon || tc == funPtrTyCon || tc == addrTyCon)
812 isFFIDynResultTy :: Type -> Bool
813 -- The result type of a foreign export dynamic must be Ptr, FunPtr, Addr,
814 -- or a newtype of either.
815 isFFIDynResultTy = checkRepTyCon (\tc -> tc == ptrTyCon || tc == funPtrTyCon || tc == addrTyCon)
817 isFFILabelTy :: Type -> Bool
818 -- The type of a foreign label must be Ptr, FunPtr, Addr,
819 -- or a newtype of either.
820 isFFILabelTy = checkRepTyCon (\tc -> tc == ptrTyCon || tc == funPtrTyCon || tc == addrTyCon)
822 checkRepTyCon :: (TyCon -> Bool) -> Type -> Bool
823 -- Look through newtypes
824 -- Non-recursive ones are transparent to splitTyConApp,
825 -- but recursive ones aren't; hence the splitNewType_maybe
826 checkRepTyCon check_tc ty
827 | Just ty' <- splitNewType_maybe ty = checkRepTyCon check_tc ty'
828 | Just (tc,_) <- splitTyConApp_maybe ty = check_tc tc
832 ----------------------------------------------
833 These chaps do the work; they are not exported
834 ----------------------------------------------
837 legalFEArgTyCon :: TyCon -> Bool
838 -- It's illegal to return foreign objects and (mutable)
839 -- bytearrays from a _ccall_ / foreign declaration
840 -- (or be passed them as arguments in foreign exported functions).
842 | getUnique tc `elem` [ foreignObjTyConKey, foreignPtrTyConKey,
843 byteArrayTyConKey, mutableByteArrayTyConKey ]
845 -- It's also illegal to make foreign exports that take unboxed
846 -- arguments. The RTS API currently can't invoke such things. --SDM 7/2000
848 = boxedMarshalableTyCon tc
850 legalFIResultTyCon :: DynFlags -> TyCon -> Bool
851 legalFIResultTyCon dflags tc
852 | getUnique tc `elem`
853 [ foreignObjTyConKey, foreignPtrTyConKey,
854 byteArrayTyConKey, mutableByteArrayTyConKey ] = False
855 | tc == unitTyCon = True
856 | otherwise = marshalableTyCon dflags tc
858 legalFEResultTyCon :: TyCon -> Bool
859 legalFEResultTyCon tc
860 | getUnique tc `elem`
861 [ foreignObjTyConKey, foreignPtrTyConKey,
862 byteArrayTyConKey, mutableByteArrayTyConKey ] = False
863 | tc == unitTyCon = True
864 | otherwise = boxedMarshalableTyCon tc
866 legalOutgoingTyCon :: DynFlags -> Safety -> TyCon -> Bool
867 -- Checks validity of types going from Haskell -> external world
868 legalOutgoingTyCon dflags safety tc
869 | playSafe safety && getUnique tc `elem` [byteArrayTyConKey, mutableByteArrayTyConKey]
872 = marshalableTyCon dflags tc
874 marshalableTyCon dflags tc
875 = (dopt Opt_GlasgowExts dflags && isUnLiftedTyCon tc)
876 || boxedMarshalableTyCon tc
878 boxedMarshalableTyCon tc
879 = getUnique tc `elem` [ intTyConKey, int8TyConKey, int16TyConKey
880 , int32TyConKey, int64TyConKey
881 , wordTyConKey, word8TyConKey, word16TyConKey
882 , word32TyConKey, word64TyConKey
883 , floatTyConKey, doubleTyConKey
884 , addrTyConKey, ptrTyConKey, funPtrTyConKey
885 , charTyConKey, foreignObjTyConKey
888 , byteArrayTyConKey, mutableByteArrayTyConKey
894 %************************************************************************
896 \subsection{Unification with an explicit substitution}
898 %************************************************************************
900 (allDistinctTyVars tys tvs) = True
902 all the types tys are type variables,
903 distinct from each other and from tvs.
905 This is useful when checking that unification hasn't unified signature
906 type variables. For example, if the type sig is
907 f :: forall a b. a -> b -> b
908 we want to check that 'a' and 'b' havn't
909 (a) been unified with a non-tyvar type
910 (b) been unified with each other (all distinct)
911 (c) been unified with a variable free in the environment
914 allDistinctTyVars :: [Type] -> TyVarSet -> Bool
916 allDistinctTyVars [] acc
918 allDistinctTyVars (ty:tys) acc
919 = case tcGetTyVar_maybe ty of
920 Nothing -> False -- (a)
921 Just tv | tv `elemVarSet` acc -> False -- (b) or (c)
922 | otherwise -> allDistinctTyVars tys (acc `extendVarSet` tv)
926 %************************************************************************
928 \subsection{Unification with an explicit substitution}
930 %************************************************************************
932 Unify types with an explicit substitution and no monad.
933 Ignore usage annotations.
937 = (TyVarSet, -- Set of template tyvars
938 TyVarSubstEnv) -- Not necessarily idempotent
940 unifyTysX :: TyVarSet -- Template tyvars
943 -> Maybe TyVarSubstEnv
944 unifyTysX tmpl_tyvars ty1 ty2
945 = uTysX ty1 ty2 (\(_,s) -> Just s) (tmpl_tyvars, emptySubstEnv)
947 unifyExtendTysX :: TyVarSet -- Template tyvars
948 -> TyVarSubstEnv -- Substitution to start with
951 -> Maybe TyVarSubstEnv -- Extended substitution
952 unifyExtendTysX tmpl_tyvars subst ty1 ty2
953 = uTysX ty1 ty2 (\(_,s) -> Just s) (tmpl_tyvars, subst)
955 unifyTyListsX :: TyVarSet -> [Type] -> [Type]
956 -> Maybe TyVarSubstEnv
957 unifyTyListsX tmpl_tyvars tys1 tys2
958 = uTyListsX tys1 tys2 (\(_,s) -> Just s) (tmpl_tyvars, emptySubstEnv)
963 -> (MySubst -> Maybe result)
967 uTysX (NoteTy _ ty1) ty2 k subst = uTysX ty1 ty2 k subst
968 uTysX ty1 (NoteTy _ ty2) k subst = uTysX ty1 ty2 k subst
970 -- Variables; go for uVar
971 uTysX (TyVarTy tyvar1) (TyVarTy tyvar2) k subst
974 uTysX (TyVarTy tyvar1) ty2 k subst@(tmpls,_)
975 | tyvar1 `elemVarSet` tmpls
976 = uVarX tyvar1 ty2 k subst
977 uTysX ty1 (TyVarTy tyvar2) k subst@(tmpls,_)
978 | tyvar2 `elemVarSet` tmpls
979 = uVarX tyvar2 ty1 k subst
982 uTysX (SourceTy (IParam n1 t1)) (SourceTy (IParam n2 t2)) k subst
983 | n1 == n2 = uTysX t1 t2 k subst
984 uTysX (SourceTy (ClassP c1 tys1)) (SourceTy (ClassP c2 tys2)) k subst
985 | c1 == c2 = uTyListsX tys1 tys2 k subst
986 uTysX (SourceTy (NType tc1 tys1)) (SourceTy (NType tc2 tys2)) k subst
987 | tc1 == tc2 = 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 (TyConApp con1 tys1) (TyConApp con2 tys2) k subst
995 | (con1 == con2 && equalLength tys1 tys2)
996 = uTyListsX tys1 tys2 k subst
998 -- Applications need a bit of care!
999 -- They can match FunTy and TyConApp, so use splitAppTy_maybe
1000 -- NB: we've already dealt with type variables and Notes,
1001 -- so if one type is an App the other one jolly well better be too
1002 uTysX (AppTy s1 t1) ty2 k subst
1003 = case tcSplitAppTy_maybe ty2 of
1004 Just (s2, t2) -> uTysX s1 s2 (uTysX t1 t2 k) subst
1005 Nothing -> Nothing -- Fail
1007 uTysX ty1 (AppTy s2 t2) k subst
1008 = case tcSplitAppTy_maybe ty1 of
1009 Just (s1, t1) -> uTysX s1 s2 (uTysX t1 t2 k) subst
1010 Nothing -> Nothing -- Fail
1012 -- Not expecting for-alls in unification
1014 uTysX (ForAllTy _ _) ty2 k subst = panic "Unify.uTysX subst:ForAllTy (1st arg)"
1015 uTysX ty1 (ForAllTy _ _) k subst = panic "Unify.uTysX subst:ForAllTy (2nd arg)"
1019 uTysX (UsageTy _ t1) t2 k subst = uTysX t1 t2 k subst
1020 uTysX t1 (UsageTy _ t2) k subst = uTysX t1 t2 k subst
1022 -- Anything else fails
1023 uTysX ty1 ty2 k subst = Nothing
1026 uTyListsX [] [] k subst = k subst
1027 uTyListsX (ty1:tys1) (ty2:tys2) k subst = uTysX ty1 ty2 (uTyListsX tys1 tys2 k) subst
1028 uTyListsX tys1 tys2 k subst = Nothing -- Fail if the lists are different lengths
1032 -- Invariant: tv1 is a unifiable variable
1033 uVarX tv1 ty2 k subst@(tmpls, env)
1034 = case lookupSubstEnv env tv1 of
1035 Just (DoneTy ty1) -> -- Already bound
1036 uTysX ty1 ty2 k subst
1038 Nothing -- Not already bound
1039 | typeKind ty2 `eqKind` tyVarKind tv1
1040 && occur_check_ok ty2
1041 -> -- No kind mismatch nor occur check
1042 UASSERT( not (isUTy ty2) )
1043 k (tmpls, extendSubstEnv env tv1 (DoneTy ty2))
1045 | otherwise -> Nothing -- Fail if kind mis-match or occur check
1047 occur_check_ok ty = all occur_check_ok_tv (varSetElems (tyVarsOfType ty))
1048 occur_check_ok_tv tv | tv1 == tv = False
1049 | otherwise = case lookupSubstEnv env tv of
1051 Just (DoneTy ty) -> occur_check_ok ty
1056 %************************************************************************
1058 \subsection{Matching on types}
1060 %************************************************************************
1062 Matching is a {\em unidirectional} process, matching a type against a
1063 template (which is just a type with type variables in it). The
1064 matcher assumes that there are no repeated type variables in the
1065 template, so that it simply returns a mapping of type variables to
1066 types. It also fails on nested foralls.
1068 @matchTys@ matches corresponding elements of a list of templates and
1069 types. It and @matchTy@ both ignore usage annotations, unlike the
1070 main function @match@.
1073 matchTy :: TyVarSet -- Template tyvars
1075 -> Type -- Proposed instance of template
1076 -> Maybe TyVarSubstEnv -- Matching substitution
1079 matchTys :: TyVarSet -- Template tyvars
1080 -> [Type] -- Templates
1081 -> [Type] -- Proposed instance of template
1082 -> Maybe (TyVarSubstEnv, -- Matching substitution
1083 [Type]) -- Left over instance types
1085 matchTy tmpls ty1 ty2 = match ty1 ty2 tmpls (\ senv -> Just senv) emptySubstEnv
1087 matchTys tmpls tys1 tys2 = match_list tys1 tys2 tmpls
1088 (\ (senv,tys) -> Just (senv,tys))
1092 @match@ is the main function. It takes a flag indicating whether
1093 usage annotations are to be respected.
1096 match :: Type -> Type -- Current match pair
1097 -> TyVarSet -- Template vars
1098 -> (TyVarSubstEnv -> Maybe result) -- Continuation
1099 -> TyVarSubstEnv -- Current subst
1102 -- When matching against a type variable, see if the variable
1103 -- has already been bound. If so, check that what it's bound to
1104 -- is the same as ty; if not, bind it and carry on.
1106 match (TyVarTy v) ty tmpls k senv
1107 | v `elemVarSet` tmpls
1108 = -- v is a template variable
1109 case lookupSubstEnv senv v of
1110 Nothing -> UASSERT( not (isUTy ty) )
1111 k (extendSubstEnv senv v (DoneTy ty))
1112 Just (DoneTy ty') | ty' `tcEqType` ty -> k senv -- Succeeds
1113 | otherwise -> Nothing -- Fails
1116 = -- v is not a template variable; ty had better match
1117 -- Can't use (==) because types differ
1118 case tcGetTyVar_maybe ty of
1119 Just v' | v == v' -> k senv -- Success
1120 other -> Nothing -- Failure
1121 -- This tcGetTyVar_maybe is *required* because it must strip Notes.
1122 -- I guess the reason the Note-stripping case is *last* rather than first
1123 -- is to preserve type synonyms etc., so I'm not moving it to the
1124 -- top; but this means that (without the deNotetype) a type
1125 -- variable may not match the pattern (TyVarTy v') as one would
1126 -- expect, due to an intervening Note. KSW 2000-06.
1129 match (SourceTy (IParam n1 t1)) (SourceTy (IParam n2 t2)) tmpls k senv
1130 | n1 == n2 = match t1 t2 tmpls k senv
1131 match (SourceTy (ClassP c1 tys1)) (SourceTy (ClassP c2 tys2)) tmpls k senv
1132 | c1 == c2 = match_list_exactly tys1 tys2 tmpls k senv
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 -- Functions; just check the two parts
1137 match (FunTy arg1 res1) (FunTy arg2 res2) tmpls k senv
1138 = match arg1 arg2 tmpls (match res1 res2 tmpls k) senv
1140 match (AppTy fun1 arg1) ty2 tmpls k senv
1141 = case tcSplitAppTy_maybe ty2 of
1142 Just (fun2,arg2) -> match fun1 fun2 tmpls (match arg1 arg2 tmpls k) senv
1143 Nothing -> Nothing -- Fail
1145 match (TyConApp tc1 tys1) (TyConApp tc2 tys2) tmpls k senv
1146 | tc1 == tc2 = match_list_exactly tys1 tys2 tmpls k senv
1148 -- Newtypes are opaque; other source types should not happen
1149 match (SourceTy (NType tc1 tys1)) (SourceTy (NType tc2 tys2)) tmpls k senv
1150 | tc1 == tc2 = match_list_exactly tys1 tys2 tmpls k senv
1152 match (UsageTy _ ty1) ty2 tmpls k senv = match ty1 ty2 tmpls k senv
1153 match ty1 (UsageTy _ ty2) tmpls k senv = match ty1 ty2 tmpls k senv
1155 -- With type synonyms, we have to be careful for the exact
1156 -- same reasons as in the unifier. Please see the
1157 -- considerable commentary there before changing anything
1158 -- here! (WDP 95/05)
1159 match (NoteTy n1 ty1) ty2 tmpls k senv = match ty1 ty2 tmpls k senv
1160 match ty1 (NoteTy n2 ty2) tmpls k senv = match ty1 ty2 tmpls k senv
1163 match _ _ _ _ _ = Nothing
1165 match_list_exactly tys1 tys2 tmpls k senv
1166 = match_list tys1 tys2 tmpls k' senv
1168 k' (senv', tys2') | null tys2' = k senv' -- Succeed
1169 | otherwise = Nothing -- Fail
1171 match_list [] tys2 tmpls k senv = k (senv, tys2)
1172 match_list (ty1:tys1) [] tmpls k senv = Nothing -- Not enough arg tys => failure
1173 match_list (ty1:tys1) (ty2:tys2) tmpls k senv
1174 = match ty1 ty2 tmpls (match_list tys1 tys2 tmpls k) senv