Fix #12919 by making the flattener homegeneous.
[ghc.git] / compiler / types / Type.hs
1 -- (c) The University of Glasgow 2006
2 -- (c) The GRASP/AQUA Project, Glasgow University, 1998
3 --
4 -- Type - public interface
5
6 {-# LANGUAGE CPP, FlexibleContexts #-}
7 {-# OPTIONS_GHC -fno-warn-orphans #-}
8
9 -- | Main functions for manipulating types and type-related things
10 module Type (
11 -- Note some of this is just re-exports from TyCon..
12
13 -- * Main data types representing Types
14 -- $type_classification
15
16 -- $representation_types
17 TyThing(..), Type, ArgFlag(..), KindOrType, PredType, ThetaType,
18 Var, TyVar, isTyVar, TyCoVar, TyBinder, TyVarBinder,
19
20 -- ** Constructing and deconstructing types
21 mkTyVarTy, mkTyVarTys, getTyVar, getTyVar_maybe, repGetTyVar_maybe,
22 getCastedTyVar_maybe, tyVarKind,
23
24 mkAppTy, mkAppTys, splitAppTy, splitAppTys, repSplitAppTys,
25 splitAppTy_maybe, repSplitAppTy_maybe, tcRepSplitAppTy_maybe,
26
27 mkFunTy, mkFunTys, splitFunTy, splitFunTy_maybe,
28 splitFunTys, funResultTy, funArgTy,
29
30 mkTyConApp, mkTyConTy,
31 tyConAppTyCon_maybe, tyConAppTyConPicky_maybe,
32 tyConAppArgs_maybe, tyConAppTyCon, tyConAppArgs,
33 splitTyConApp_maybe, splitTyConApp, tyConAppArgN,
34 tcRepSplitTyConApp_maybe, tcSplitTyConApp_maybe,
35 splitListTyConApp_maybe,
36 repSplitTyConApp_maybe,
37
38 mkForAllTy, mkForAllTys, mkInvForAllTys, mkSpecForAllTys,
39 mkVisForAllTys, mkInvForAllTy,
40 splitForAllTys, splitForAllTyVarBndrs,
41 splitForAllTy_maybe, splitForAllTy,
42 splitPiTy_maybe, splitPiTy, splitPiTys,
43 mkPiTy, mkPiTys, mkTyConBindersPreferAnon,
44 mkLamType, mkLamTypes,
45 piResultTy, piResultTys,
46 applyTysX, dropForAlls,
47
48 mkNumLitTy, isNumLitTy,
49 mkStrLitTy, isStrLitTy,
50
51 getRuntimeRep_maybe, getRuntimeRepFromKind_maybe,
52
53 mkCastTy, mkCoercionTy, splitCastTy_maybe,
54
55 userTypeError_maybe, pprUserTypeErrorTy,
56
57 coAxNthLHS,
58 stripCoercionTy, splitCoercionType_maybe,
59
60 splitPiTysInvisible, filterOutInvisibleTypes,
61 partitionInvisibles,
62 synTyConResKind,
63
64 modifyJoinResTy, setJoinResTy,
65
66 -- Analyzing types
67 TyCoMapper(..), mapType, mapCoercion,
68
69 -- (Newtypes)
70 newTyConInstRhs,
71
72 -- Pred types
73 mkFamilyTyConApp,
74 isDictLikeTy,
75 mkPrimEqPred, mkReprPrimEqPred, mkPrimEqPredRole,
76 equalityTyCon,
77 mkHeteroPrimEqPred, mkHeteroReprPrimEqPred,
78 mkClassPred,
79 isClassPred, isEqPred, isNomEqPred,
80 isIPPred, isIPPred_maybe, isIPTyCon, isIPClass,
81 isCTupleClass,
82
83 -- Deconstructing predicate types
84 PredTree(..), EqRel(..), eqRelRole, classifyPredType,
85 getClassPredTys, getClassPredTys_maybe,
86 getEqPredTys, getEqPredTys_maybe, getEqPredRole,
87 predTypeEqRel,
88
89 -- ** Binders
90 sameVis,
91 mkTyVarBinder, mkTyVarBinders,
92 mkAnonBinder,
93 isAnonTyBinder, isNamedTyBinder,
94 binderVar, binderVars, binderKind, binderArgFlag,
95 tyBinderType, tyBinderVar_maybe,
96 binderRelevantType_maybe, caseBinder,
97 isVisibleArgFlag, isInvisibleArgFlag, isVisibleBinder, isInvisibleBinder,
98 tyConBindersTyBinders,
99
100 -- ** Common type constructors
101 funTyCon,
102
103 -- ** Predicates on types
104 isTyVarTy, isFunTy, isDictTy, isPredTy, isCoercionTy,
105 isCoercionTy_maybe, isCoercionType, isForAllTy,
106 isPiTy, isTauTy, isFamFreeTy,
107
108 isValidJoinPointType,
109
110 -- (Lifting and boxity)
111 isLiftedType_maybe, isUnliftedType, isUnboxedTupleType, isUnboxedSumType,
112 isAlgType, isDataFamilyAppType,
113 isPrimitiveType, isStrictType,
114 isRuntimeRepTy, isRuntimeRepVar, isRuntimeRepKindedTy,
115 dropRuntimeRepArgs,
116 getRuntimeRep, getRuntimeRepFromKind,
117
118 -- * Main data types representing Kinds
119 Kind,
120
121 -- ** Finding the kind of a type
122 typeKind, isTypeLevPoly, resultIsLevPoly,
123
124 -- ** Common Kind
125 liftedTypeKind,
126
127 -- * Type free variables
128 tyCoFVsOfType, tyCoFVsBndr,
129 tyCoVarsOfType, tyCoVarsOfTypes,
130 tyCoVarsOfTypeDSet,
131 coVarsOfType,
132 coVarsOfTypes, closeOverKinds, closeOverKindsList,
133 noFreeVarsOfType,
134 splitVisVarsOfType, splitVisVarsOfTypes,
135 expandTypeSynonyms,
136 typeSize,
137
138 -- * Well-scoped lists of variables
139 dVarSetElemsWellScoped, toposortTyVars, tyCoVarsOfTypeWellScoped,
140 tyCoVarsOfTypesWellScoped,
141
142 -- * Type comparison
143 eqType, eqTypeX, eqTypes, nonDetCmpType, nonDetCmpTypes, nonDetCmpTypeX,
144 nonDetCmpTypesX, nonDetCmpTc,
145 eqVarBndrs,
146
147 -- * Forcing evaluation of types
148 seqType, seqTypes,
149
150 -- * Other views onto Types
151 coreView, tcView,
152
153 tyConsOfType,
154
155 -- * Main type substitution data types
156 TvSubstEnv, -- Representation widely visible
157 TCvSubst(..), -- Representation visible to a few friends
158
159 -- ** Manipulating type substitutions
160 emptyTvSubstEnv, emptyTCvSubst, mkEmptyTCvSubst,
161
162 mkTCvSubst, zipTvSubst, mkTvSubstPrs,
163 notElemTCvSubst,
164 getTvSubstEnv, setTvSubstEnv,
165 zapTCvSubst, getTCvInScope, getTCvSubstRangeFVs,
166 extendTCvInScope, extendTCvInScopeList, extendTCvInScopeSet,
167 extendTCvSubst, extendCvSubst,
168 extendTvSubst, extendTvSubstBinderAndInScope,
169 extendTvSubstList, extendTvSubstAndInScope,
170 extendTvSubstWithClone,
171 isInScope, composeTCvSubstEnv, composeTCvSubst, zipTyEnv, zipCoEnv,
172 isEmptyTCvSubst, unionTCvSubst,
173
174 -- ** Performing substitution on types and kinds
175 substTy, substTys, substTyWith, substTysWith, substTheta,
176 substTyAddInScope,
177 substTyUnchecked, substTysUnchecked, substThetaUnchecked,
178 substTyWithUnchecked,
179 substCoUnchecked, substCoWithUnchecked,
180 substTyVarBndr, substTyVar, substTyVars,
181 cloneTyVarBndr, cloneTyVarBndrs, lookupTyVar,
182
183 -- * Pretty-printing
184 pprType, pprParendType, pprPrecType,
185 pprTypeApp, pprTyThingCategory, pprShortTyThing,
186 pprTvBndr, pprTvBndrs, pprForAll, pprUserForAll,
187 pprSigmaType, ppSuggestExplicitKinds,
188 pprTheta, pprThetaArrowTy, pprClassPred,
189 pprKind, pprParendKind, pprSourceTyCon,
190 TyPrec(..), maybeParen,
191 pprTyVar, pprTyVars,
192
193 -- * Tidying type related things up for printing
194 tidyType, tidyTypes,
195 tidyOpenType, tidyOpenTypes,
196 tidyOpenKind,
197 tidyTyCoVarBndr, tidyTyCoVarBndrs, tidyFreeTyCoVars,
198 tidyOpenTyCoVar, tidyOpenTyCoVars,
199 tidyTyVarOcc,
200 tidyTopType,
201 tidyKind,
202 tidyTyVarBinder, tidyTyVarBinders
203 ) where
204
205 #include "HsVersions.h"
206
207 import GhcPrelude
208
209 import BasicTypes
210
211 -- We import the representation and primitive functions from TyCoRep.
212 -- Many things are reexported, but not the representation!
213
214 import Kind
215 import TyCoRep
216
217 -- friends:
218 import Var
219 import VarEnv
220 import VarSet
221 import UniqSet
222
223 import Class
224 import TyCon
225 import TysPrim
226 import {-# SOURCE #-} TysWiredIn ( listTyCon, typeNatKind
227 , typeSymbolKind, liftedTypeKind )
228 import PrelNames
229 import CoAxiom
230 import {-# SOURCE #-} Coercion
231
232 -- others
233 import Util
234 import Outputable
235 import FastString
236 import Pair
237 import ListSetOps
238 import Digraph
239 import Unique ( nonDetCmpUnique )
240
241 import Maybes ( orElse )
242 import Data.Maybe ( isJust, mapMaybe )
243 import Control.Monad ( guard )
244 import Control.Arrow ( first, second )
245
246 -- $type_classification
247 -- #type_classification#
248 --
249 -- Types are one of:
250 --
251 -- [Unboxed] Iff its representation is other than a pointer
252 -- Unboxed types are also unlifted.
253 --
254 -- [Lifted] Iff it has bottom as an element.
255 -- Closures always have lifted types: i.e. any
256 -- let-bound identifier in Core must have a lifted
257 -- type. Operationally, a lifted object is one that
258 -- can be entered.
259 -- Only lifted types may be unified with a type variable.
260 --
261 -- [Algebraic] Iff it is a type with one or more constructors, whether
262 -- declared with @data@ or @newtype@.
263 -- An algebraic type is one that can be deconstructed
264 -- with a case expression. This is /not/ the same as
265 -- lifted types, because we also include unboxed
266 -- tuples in this classification.
267 --
268 -- [Data] Iff it is a type declared with @data@, or a boxed tuple.
269 --
270 -- [Primitive] Iff it is a built-in type that can't be expressed in Haskell.
271 --
272 -- Currently, all primitive types are unlifted, but that's not necessarily
273 -- the case: for example, @Int@ could be primitive.
274 --
275 -- Some primitive types are unboxed, such as @Int#@, whereas some are boxed
276 -- but unlifted (such as @ByteArray#@). The only primitive types that we
277 -- classify as algebraic are the unboxed tuples.
278 --
279 -- Some examples of type classifications that may make this a bit clearer are:
280 --
281 -- @
282 -- Type primitive boxed lifted algebraic
283 -- -----------------------------------------------------------------------------
284 -- Int# Yes No No No
285 -- ByteArray# Yes Yes No No
286 -- (\# a, b \#) Yes No No Yes
287 -- (\# a | b \#) Yes No No Yes
288 -- ( a, b ) No Yes Yes Yes
289 -- [a] No Yes Yes Yes
290 -- @
291
292 -- $representation_types
293 -- A /source type/ is a type that is a separate type as far as the type checker is
294 -- concerned, but which has a more low-level representation as far as Core-to-Core
295 -- passes and the rest of the back end is concerned.
296 --
297 -- You don't normally have to worry about this, as the utility functions in
298 -- this module will automatically convert a source into a representation type
299 -- if they are spotted, to the best of it's abilities. If you don't want this
300 -- to happen, use the equivalent functions from the "TcType" module.
301
302 {-
303 ************************************************************************
304 * *
305 Type representation
306 * *
307 ************************************************************************
308
309 Note [coreView vs tcView]
310 ~~~~~~~~~~~~~~~~~~~~~~~~~
311 So far as the typechecker is concerned, 'Constraint' and 'TYPE LiftedRep' are distinct kinds.
312
313 But in Core these two are treated as identical.
314
315 We implement this by making 'coreView' convert 'Constraint' to 'TYPE LiftedRep' on the fly.
316 The function tcView (used in the type checker) does not do this.
317
318 See also Trac #11715, which tracks removing this inconsistency.
319
320 -}
321
322 {-# INLINE coreView #-}
323 coreView :: Type -> Maybe Type
324 -- ^ This function Strips off the /top layer only/ of a type synonym
325 -- application (if any) its underlying representation type.
326 -- Returns Nothing if there is nothing to look through.
327 -- This function considers 'Constraint' to be a synonym of @TYPE LiftedRep@.
328 --
329 -- By being non-recursive and inlined, this case analysis gets efficiently
330 -- joined onto the case analysis that the caller is already doing
331 coreView (TyConApp tc tys) | Just (tenv, rhs, tys') <- expandSynTyCon_maybe tc tys
332 = Just (mkAppTys (substTy (mkTvSubstPrs tenv) rhs) tys')
333 -- The free vars of 'rhs' should all be bound by 'tenv', so it's
334 -- ok to use 'substTy' here.
335 -- See also Note [The substitution invariant] in TyCoRep.
336 -- Its important to use mkAppTys, rather than (foldl AppTy),
337 -- because the function part might well return a
338 -- partially-applied type constructor; indeed, usually will!
339
340 coreView (TyConApp tc []) -- At the Core level, Constraint = Type
341 | isStarKindSynonymTyCon tc
342 = Just liftedTypeKind
343
344 coreView _ = Nothing
345
346 -- | Gives the typechecker view of a type. This unwraps synonyms but
347 -- leaves 'Constraint' alone. c.f. coreView, which turns Constraint into
348 -- TYPE LiftedRep. Returns Nothing if no unwrapping happens.
349 -- See also Note [coreView vs tcView] in Type.
350 {-# INLINE tcView #-}
351 tcView :: Type -> Maybe Type
352 tcView (TyConApp tc tys) | Just (tenv, rhs, tys') <- expandSynTyCon_maybe tc tys
353 = Just (mkAppTys (substTy (mkTvSubstPrs tenv) rhs) tys')
354 -- The free vars of 'rhs' should all be bound by 'tenv', so it's
355 -- ok to use 'substTy' here.
356 -- See also Note [The substitution invariant] in TyCoRep.
357 -- Its important to use mkAppTys, rather than (foldl AppTy),
358 -- because the function part might well return a
359 -- partially-applied type constructor; indeed, usually will!
360 tcView _ = Nothing
361
362 -----------------------------------------------
363 expandTypeSynonyms :: Type -> Type
364 -- ^ Expand out all type synonyms. Actually, it'd suffice to expand out
365 -- just the ones that discard type variables (e.g. type Funny a = Int)
366 -- But we don't know which those are currently, so we just expand all.
367 --
368 -- 'expandTypeSynonyms' only expands out type synonyms mentioned in the type,
369 -- not in the kinds of any TyCon or TyVar mentioned in the type.
370 --
371 -- Keep this synchronized with 'synonymTyConsOfType'
372 expandTypeSynonyms ty
373 = go (mkEmptyTCvSubst in_scope) ty
374 where
375 in_scope = mkInScopeSet (tyCoVarsOfType ty)
376
377 go subst (TyConApp tc tys)
378 | Just (tenv, rhs, tys') <- expandSynTyCon_maybe tc expanded_tys
379 = let subst' = mkTvSubst in_scope (mkVarEnv tenv)
380 -- Make a fresh substitution; rhs has nothing to
381 -- do with anything that has happened so far
382 -- NB: if you make changes here, be sure to build an
383 -- /idempotent/ substitution, even in the nested case
384 -- type T a b = a -> b
385 -- type S x y = T y x
386 -- (Trac #11665)
387 in mkAppTys (go subst' rhs) tys'
388 | otherwise
389 = TyConApp tc expanded_tys
390 where
391 expanded_tys = (map (go subst) tys)
392
393 go _ (LitTy l) = LitTy l
394 go subst (TyVarTy tv) = substTyVar subst tv
395 go subst (AppTy t1 t2) = mkAppTy (go subst t1) (go subst t2)
396 go subst (FunTy arg res)
397 = mkFunTy (go subst arg) (go subst res)
398 go subst (ForAllTy (TvBndr tv vis) t)
399 = let (subst', tv') = substTyVarBndrCallback go subst tv in
400 ForAllTy (TvBndr tv' vis) (go subst' t)
401 go subst (CastTy ty co) = mkCastTy (go subst ty) (go_co subst co)
402 go subst (CoercionTy co) = mkCoercionTy (go_co subst co)
403
404 go_co subst (Refl r ty)
405 = mkReflCo r (go subst ty)
406 -- NB: coercions are always expanded upon creation
407 go_co subst (TyConAppCo r tc args)
408 = mkTyConAppCo r tc (map (go_co subst) args)
409 go_co subst (AppCo co arg)
410 = mkAppCo (go_co subst co) (go_co subst arg)
411 go_co subst (ForAllCo tv kind_co co)
412 = let (subst', tv', kind_co') = go_cobndr subst tv kind_co in
413 mkForAllCo tv' kind_co' (go_co subst' co)
414 go_co subst (FunCo r co1 co2)
415 = mkFunCo r (go_co subst co1) (go_co subst co2)
416 go_co subst (CoVarCo cv)
417 = substCoVar subst cv
418 go_co subst (AxiomInstCo ax ind args)
419 = mkAxiomInstCo ax ind (map (go_co subst) args)
420 go_co subst (UnivCo p r t1 t2)
421 = mkUnivCo (go_prov subst p) r (go subst t1) (go subst t2)
422 go_co subst (SymCo co)
423 = mkSymCo (go_co subst co)
424 go_co subst (TransCo co1 co2)
425 = mkTransCo (go_co subst co1) (go_co subst co2)
426 go_co subst (NthCo n co)
427 = mkNthCo n (go_co subst co)
428 go_co subst (LRCo lr co)
429 = mkLRCo lr (go_co subst co)
430 go_co subst (InstCo co arg)
431 = mkInstCo (go_co subst co) (go_co subst arg)
432 go_co subst (CoherenceCo co1 co2)
433 = mkCoherenceCo (go_co subst co1) (go_co subst co2)
434 go_co subst (KindCo co)
435 = mkKindCo (go_co subst co)
436 go_co subst (SubCo co)
437 = mkSubCo (go_co subst co)
438 go_co subst (AxiomRuleCo ax cs)
439 = AxiomRuleCo ax (map (go_co subst) cs)
440 go_co _ (HoleCo h)
441 = pprPanic "expandTypeSynonyms hit a hole" (ppr h)
442
443 go_prov _ UnsafeCoerceProv = UnsafeCoerceProv
444 go_prov subst (PhantomProv co) = PhantomProv (go_co subst co)
445 go_prov subst (ProofIrrelProv co) = ProofIrrelProv (go_co subst co)
446 go_prov _ p@(PluginProv _) = p
447
448 -- the "False" and "const" are to accommodate the type of
449 -- substForAllCoBndrCallback, which is general enough to
450 -- handle coercion optimization (which sometimes swaps the
451 -- order of a coercion)
452 go_cobndr subst = substForAllCoBndrCallback False (go_co subst) subst
453
454 {-
455 ************************************************************************
456 * *
457 Analyzing types
458 * *
459 ************************************************************************
460
461 These functions do a map-like operation over types, performing some operation
462 on all variables and binding sites. Primarily used for zonking.
463
464 Note [Efficiency for mapCoercion ForAllCo case]
465 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
466 As noted in Note [Forall coercions] in TyCoRep, a ForAllCo is a bit redundant.
467 It stores a TyVar and a Coercion, where the kind of the TyVar always matches
468 the left-hand kind of the coercion. This is convenient lots of the time, but
469 not when mapping a function over a coercion.
470
471 The problem is that tcm_tybinder will affect the TyVar's kind and
472 mapCoercion will affect the Coercion, and we hope that the results will be
473 the same. Even if they are the same (which should generally happen with
474 correct algorithms), then there is an efficiency issue. In particular,
475 this problem seems to make what should be a linear algorithm into a potentially
476 exponential one. But it's only going to be bad in the case where there's
477 lots of foralls in the kinds of other foralls. Like this:
478
479 forall a : (forall b : (forall c : ...). ...). ...
480
481 This construction seems unlikely. So we'll do the inefficient, easy way
482 for now.
483
484 Note [Specialising mappers]
485 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
486 These INLINABLE pragmas are indispensable. mapType/mapCoercion are used
487 to implement zonking, and it's vital that they get specialised to the TcM
488 monad. This specialisation happens automatically (that is, without a
489 SPECIALISE pragma) as long as the definitions are INLINABLE. For example,
490 this one change made a 20% allocation difference in perf/compiler/T5030.
491
492 -}
493
494 -- | This describes how a "map" operation over a type/coercion should behave
495 data TyCoMapper env m
496 = TyCoMapper
497 { tcm_smart :: Bool -- ^ Should the new type be created with smart
498 -- constructors?
499 , tcm_tyvar :: env -> TyVar -> m Type
500 , tcm_covar :: env -> CoVar -> m Coercion
501 , tcm_hole :: env -> CoercionHole -> m Coercion
502 -- ^ What to do with coercion holes.
503 -- See Note [Coercion holes] in TyCoRep.
504
505 , tcm_tybinder :: env -> TyVar -> ArgFlag -> m (env, TyVar)
506 -- ^ The returned env is used in the extended scope
507 }
508
509 {-# INLINABLE mapType #-} -- See Note [Specialising mappers]
510 mapType :: Monad m => TyCoMapper env m -> env -> Type -> m Type
511 mapType mapper@(TyCoMapper { tcm_smart = smart, tcm_tyvar = tyvar
512 , tcm_tybinder = tybinder })
513 env ty
514 = go ty
515 where
516 go (TyVarTy tv) = tyvar env tv
517 go (AppTy t1 t2) = mkappty <$> go t1 <*> go t2
518 go t@(TyConApp _ []) = return t -- avoid allocation in this exceedingly
519 -- common case (mostly, for *)
520 go (TyConApp tc tys) = mktyconapp tc <$> mapM go tys
521 go (FunTy arg res) = FunTy <$> go arg <*> go res
522 go (ForAllTy (TvBndr tv vis) inner)
523 = do { (env', tv') <- tybinder env tv vis
524 ; inner' <- mapType mapper env' inner
525 ; return $ ForAllTy (TvBndr tv' vis) inner' }
526 go ty@(LitTy {}) = return ty
527 go (CastTy ty co) = mkcastty <$> go ty <*> mapCoercion mapper env co
528 go (CoercionTy co) = CoercionTy <$> mapCoercion mapper env co
529
530 (mktyconapp, mkappty, mkcastty)
531 | smart = (mkTyConApp, mkAppTy, mkCastTy)
532 | otherwise = (TyConApp, AppTy, CastTy)
533
534 {-# INLINABLE mapCoercion #-} -- See Note [Specialising mappers]
535 mapCoercion :: Monad m
536 => TyCoMapper env m -> env -> Coercion -> m Coercion
537 mapCoercion mapper@(TyCoMapper { tcm_smart = smart, tcm_covar = covar
538 , tcm_hole = cohole, tcm_tybinder = tybinder })
539 env co
540 = go co
541 where
542 go (Refl r ty) = Refl r <$> mapType mapper env ty
543 go (TyConAppCo r tc args)
544 = mktyconappco r tc <$> mapM go args
545 go (AppCo c1 c2) = mkappco <$> go c1 <*> go c2
546 go (ForAllCo tv kind_co co)
547 = do { kind_co' <- go kind_co
548 ; (env', tv') <- tybinder env tv Inferred
549 ; co' <- mapCoercion mapper env' co
550 ; return $ mkforallco tv' kind_co' co' }
551 -- See Note [Efficiency for mapCoercion ForAllCo case]
552 go (FunCo r c1 c2) = mkFunCo r <$> go c1 <*> go c2
553 go (CoVarCo cv) = covar env cv
554 go (AxiomInstCo ax i args)
555 = mkaxiominstco ax i <$> mapM go args
556 go (HoleCo hole) = cohole env hole
557 go (UnivCo p r t1 t2)
558 = mkunivco <$> go_prov p <*> pure r
559 <*> mapType mapper env t1 <*> mapType mapper env t2
560 go (SymCo co) = mksymco <$> go co
561 go (TransCo c1 c2) = mktransco <$> go c1 <*> go c2
562 go (AxiomRuleCo r cos) = AxiomRuleCo r <$> mapM go cos
563 go (NthCo i co) = mknthco i <$> go co
564 go (LRCo lr co) = mklrco lr <$> go co
565 go (InstCo co arg) = mkinstco <$> go co <*> go arg
566 go (CoherenceCo c1 c2) = mkcoherenceco <$> go c1 <*> go c2
567 go (KindCo co) = mkkindco <$> go co
568 go (SubCo co) = mksubco <$> go co
569
570 go_prov UnsafeCoerceProv = return UnsafeCoerceProv
571 go_prov (PhantomProv co) = PhantomProv <$> go co
572 go_prov (ProofIrrelProv co) = ProofIrrelProv <$> go co
573 go_prov p@(PluginProv _) = return p
574
575 ( mktyconappco, mkappco, mkaxiominstco, mkunivco
576 , mksymco, mktransco, mknthco, mklrco, mkinstco, mkcoherenceco
577 , mkkindco, mksubco, mkforallco)
578 | smart
579 = ( mkTyConAppCo, mkAppCo, mkAxiomInstCo, mkUnivCo
580 , mkSymCo, mkTransCo, mkNthCo, mkLRCo, mkInstCo, mkCoherenceCo
581 , mkKindCo, mkSubCo, mkForAllCo )
582 | otherwise
583 = ( TyConAppCo, AppCo, AxiomInstCo, UnivCo
584 , SymCo, TransCo, NthCo, LRCo, InstCo, CoherenceCo
585 , KindCo, SubCo, ForAllCo )
586
587 {-
588 ************************************************************************
589 * *
590 \subsection{Constructor-specific functions}
591 * *
592 ************************************************************************
593
594
595 ---------------------------------------------------------------------
596 TyVarTy
597 ~~~~~~~
598 -}
599
600 -- | Attempts to obtain the type variable underlying a 'Type', and panics with the
601 -- given message if this is not a type variable type. See also 'getTyVar_maybe'
602 getTyVar :: String -> Type -> TyVar
603 getTyVar msg ty = case getTyVar_maybe ty of
604 Just tv -> tv
605 Nothing -> panic ("getTyVar: " ++ msg)
606
607 isTyVarTy :: Type -> Bool
608 isTyVarTy ty = isJust (getTyVar_maybe ty)
609
610 -- | Attempts to obtain the type variable underlying a 'Type'
611 getTyVar_maybe :: Type -> Maybe TyVar
612 getTyVar_maybe ty | Just ty' <- coreView ty = getTyVar_maybe ty'
613 | otherwise = repGetTyVar_maybe ty
614
615 -- | If the type is a tyvar, possibly under a cast, returns it, along
616 -- with the coercion. Thus, the co is :: kind tv ~N kind type
617 getCastedTyVar_maybe :: Type -> Maybe (TyVar, CoercionN)
618 getCastedTyVar_maybe ty | Just ty' <- coreView ty = getCastedTyVar_maybe ty'
619 getCastedTyVar_maybe (CastTy (TyVarTy tv) co) = Just (tv, co)
620 getCastedTyVar_maybe (TyVarTy tv)
621 = Just (tv, mkReflCo Nominal (tyVarKind tv))
622 getCastedTyVar_maybe _ = Nothing
623
624 -- | Attempts to obtain the type variable underlying a 'Type', without
625 -- any expansion
626 repGetTyVar_maybe :: Type -> Maybe TyVar
627 repGetTyVar_maybe (TyVarTy tv) = Just tv
628 repGetTyVar_maybe _ = Nothing
629
630 {-
631 ---------------------------------------------------------------------
632 AppTy
633 ~~~~~
634 We need to be pretty careful with AppTy to make sure we obey the
635 invariant that a TyConApp is always visibly so. mkAppTy maintains the
636 invariant: use it.
637
638 Note [Decomposing fat arrow c=>t]
639 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
640 Can we unify (a b) with (Eq a => ty)? If we do so, we end up with
641 a partial application like ((=>) Eq a) which doesn't make sense in
642 source Haskell. In contrast, we *can* unify (a b) with (t1 -> t2).
643 Here's an example (Trac #9858) of how you might do it:
644 i :: (Typeable a, Typeable b) => Proxy (a b) -> TypeRep
645 i p = typeRep p
646
647 j = i (Proxy :: Proxy (Eq Int => Int))
648 The type (Proxy (Eq Int => Int)) is only accepted with -XImpredicativeTypes,
649 but suppose we want that. But then in the call to 'i', we end
650 up decomposing (Eq Int => Int), and we definitely don't want that.
651
652 This really only applies to the type checker; in Core, '=>' and '->'
653 are the same, as are 'Constraint' and '*'. But for now I've put
654 the test in repSplitAppTy_maybe, which applies throughout, because
655 the other calls to splitAppTy are in Unify, which is also used by
656 the type checker (e.g. when matching type-function equations).
657
658 -}
659
660 -- | Applies a type to another, as in e.g. @k a@
661 mkAppTy :: Type -> Type -> Type
662 -- See Note [Respecting definitional equality], invariant (EQ1).
663 mkAppTy (CastTy fun_ty co) arg_ty
664 | ([arg_co], res_co) <- decomposePiCos (typeKind fun_ty) [arg_ty] co
665 = (fun_ty `mkAppTy` (arg_ty `mkCastTy` arg_co)) `mkCastTy` res_co
666
667 mkAppTy (TyConApp tc tys) ty2 = mkTyConApp tc (tys ++ [ty2])
668 mkAppTy ty1 ty2 = AppTy ty1 ty2
669 -- Note that the TyConApp could be an
670 -- under-saturated type synonym. GHC allows that; e.g.
671 -- type Foo k = k a -> k a
672 -- type Id x = x
673 -- foo :: Foo Id -> Foo Id
674 --
675 -- Here Id is partially applied in the type sig for Foo,
676 -- but once the type synonyms are expanded all is well
677
678 mkAppTys :: Type -> [Type] -> Type
679 mkAppTys ty1 [] = ty1
680 mkAppTys (CastTy fun_ty co) arg_tys -- much more efficient then nested mkAppTy
681 -- Why do this? See (EQ1) of
682 -- Note [Respecting definitional equality]
683 -- in TyCoRep
684 = foldl AppTy ((mkAppTys fun_ty casted_arg_tys) `mkCastTy` res_co) leftovers
685 where
686 (arg_cos, res_co) = decomposePiCos (typeKind fun_ty) arg_tys co
687 (args_to_cast, leftovers) = splitAtList arg_cos arg_tys
688 casted_arg_tys = zipWith mkCastTy args_to_cast arg_cos
689 mkAppTys (TyConApp tc tys1) tys2 = mkTyConApp tc (tys1 ++ tys2)
690 mkAppTys ty1 tys2 = foldl AppTy ty1 tys2
691
692 -------------
693 splitAppTy_maybe :: Type -> Maybe (Type, Type)
694 -- ^ Attempt to take a type application apart, whether it is a
695 -- function, type constructor, or plain type application. Note
696 -- that type family applications are NEVER unsaturated by this!
697 splitAppTy_maybe ty | Just ty' <- coreView ty
698 = splitAppTy_maybe ty'
699 splitAppTy_maybe ty = repSplitAppTy_maybe ty
700
701 -------------
702 repSplitAppTy_maybe :: HasDebugCallStack => Type -> Maybe (Type,Type)
703 -- ^ Does the AppTy split as in 'splitAppTy_maybe', but assumes that
704 -- any Core view stuff is already done
705 repSplitAppTy_maybe (FunTy ty1 ty2)
706 = Just (TyConApp funTyCon [rep1, rep2, ty1], ty2)
707 where
708 rep1 = getRuntimeRep ty1
709 rep2 = getRuntimeRep ty2
710
711 repSplitAppTy_maybe (AppTy ty1 ty2)
712 = Just (ty1, ty2)
713
714 repSplitAppTy_maybe (TyConApp tc tys)
715 | mightBeUnsaturatedTyCon tc || tys `lengthExceeds` tyConArity tc
716 , Just (tys', ty') <- snocView tys
717 = Just (TyConApp tc tys', ty') -- Never create unsaturated type family apps!
718
719 repSplitAppTy_maybe _other = Nothing
720
721 -- this one doesn't braek apart (c => t).
722 -- See Note [Decomposing fat arrow c=>t]
723 -- Defined here to avoid module loops between Unify and TcType.
724 tcRepSplitAppTy_maybe :: Type -> Maybe (Type,Type)
725 -- ^ Does the AppTy split as in 'tcSplitAppTy_maybe', but assumes that
726 -- any coreView stuff is already done. Refuses to look through (c => t)
727 tcRepSplitAppTy_maybe (FunTy ty1 ty2)
728 | isConstraintKind (typeKind ty1)
729 = Nothing -- See Note [Decomposing fat arrow c=>t]
730
731 | otherwise
732 = Just (TyConApp funTyCon [rep1, rep2, ty1], ty2)
733 where
734 rep1 = getRuntimeRep ty1
735 rep2 = getRuntimeRep ty2
736
737 tcRepSplitAppTy_maybe (AppTy ty1 ty2) = Just (ty1, ty2)
738 tcRepSplitAppTy_maybe (TyConApp tc tys)
739 | mightBeUnsaturatedTyCon tc || tys `lengthExceeds` tyConArity tc
740 , Just (tys', ty') <- snocView tys
741 = Just (TyConApp tc tys', ty') -- Never create unsaturated type family apps!
742 tcRepSplitAppTy_maybe _other = Nothing
743
744 -- | Split a type constructor application into its type constructor and
745 -- applied types. Note that this may fail in the case of a 'FunTy' with an
746 -- argument of unknown kind 'FunTy' (e.g. @FunTy (a :: k) Int@. since the kind
747 -- of @a@ isn't of the form @TYPE rep@). Consequently, you may need to zonk your
748 -- type before using this function.
749 --
750 -- If you only need the 'TyCon', consider using 'tcTyConAppTyCon_maybe'.
751 tcSplitTyConApp_maybe :: HasCallStack => Type -> Maybe (TyCon, [Type])
752 -- Defined here to avoid module loops between Unify and TcType.
753 tcSplitTyConApp_maybe ty | Just ty' <- tcView ty = tcSplitTyConApp_maybe ty'
754 tcSplitTyConApp_maybe ty = tcRepSplitTyConApp_maybe ty
755
756 -- | Like 'tcSplitTyConApp_maybe' but doesn't look through type synonyms.
757 tcRepSplitTyConApp_maybe :: HasCallStack => Type -> Maybe (TyCon, [Type])
758 -- Defined here to avoid module loops between Unify and TcType.
759 tcRepSplitTyConApp_maybe (TyConApp tc tys)
760 = Just (tc, tys)
761
762 tcRepSplitTyConApp_maybe (FunTy arg res)
763 = Just (funTyCon, [arg_rep, res_rep, arg, res])
764 where
765 arg_rep = getRuntimeRep arg
766 res_rep = getRuntimeRep res
767
768 tcRepSplitTyConApp_maybe _
769 = Nothing
770
771 -------------
772 splitAppTy :: Type -> (Type, Type)
773 -- ^ Attempts to take a type application apart, as in 'splitAppTy_maybe',
774 -- and panics if this is not possible
775 splitAppTy ty = case splitAppTy_maybe ty of
776 Just pr -> pr
777 Nothing -> panic "splitAppTy"
778
779 -------------
780 splitAppTys :: Type -> (Type, [Type])
781 -- ^ Recursively splits a type as far as is possible, leaving a residual
782 -- type being applied to and the type arguments applied to it. Never fails,
783 -- even if that means returning an empty list of type applications.
784 splitAppTys ty = split ty ty []
785 where
786 split orig_ty ty args | Just ty' <- coreView ty = split orig_ty ty' args
787 split _ (AppTy ty arg) args = split ty ty (arg:args)
788 split _ (TyConApp tc tc_args) args
789 = let -- keep type families saturated
790 n | mightBeUnsaturatedTyCon tc = 0
791 | otherwise = tyConArity tc
792 (tc_args1, tc_args2) = splitAt n tc_args
793 in
794 (TyConApp tc tc_args1, tc_args2 ++ args)
795 split _ (FunTy ty1 ty2) args
796 = ASSERT( null args )
797 (TyConApp funTyCon [], [rep1, rep2, ty1, ty2])
798 where
799 rep1 = getRuntimeRep ty1
800 rep2 = getRuntimeRep ty2
801
802 split orig_ty _ args = (orig_ty, args)
803
804 -- | Like 'splitAppTys', but doesn't look through type synonyms
805 repSplitAppTys :: HasDebugCallStack => Type -> (Type, [Type])
806 repSplitAppTys ty = split ty []
807 where
808 split (AppTy ty arg) args = split ty (arg:args)
809 split (TyConApp tc tc_args) args
810 = let n | mightBeUnsaturatedTyCon tc = 0
811 | otherwise = tyConArity tc
812 (tc_args1, tc_args2) = splitAt n tc_args
813 in
814 (TyConApp tc tc_args1, tc_args2 ++ args)
815 split (FunTy ty1 ty2) args
816 = ASSERT( null args )
817 (TyConApp funTyCon [], [rep1, rep2, ty1, ty2])
818 where
819 rep1 = getRuntimeRep ty1
820 rep2 = getRuntimeRep ty2
821
822 split ty args = (ty, args)
823
824 {-
825 LitTy
826 ~~~~~
827 -}
828
829 mkNumLitTy :: Integer -> Type
830 mkNumLitTy n = LitTy (NumTyLit n)
831
832 -- | Is this a numeric literal. We also look through type synonyms.
833 isNumLitTy :: Type -> Maybe Integer
834 isNumLitTy ty | Just ty1 <- coreView ty = isNumLitTy ty1
835 isNumLitTy (LitTy (NumTyLit n)) = Just n
836 isNumLitTy _ = Nothing
837
838 mkStrLitTy :: FastString -> Type
839 mkStrLitTy s = LitTy (StrTyLit s)
840
841 -- | Is this a symbol literal. We also look through type synonyms.
842 isStrLitTy :: Type -> Maybe FastString
843 isStrLitTy ty | Just ty1 <- coreView ty = isStrLitTy ty1
844 isStrLitTy (LitTy (StrTyLit s)) = Just s
845 isStrLitTy _ = Nothing
846
847
848 -- | Is this type a custom user error?
849 -- If so, give us the kind and the error message.
850 userTypeError_maybe :: Type -> Maybe Type
851 userTypeError_maybe t
852 = do { (tc, _kind : msg : _) <- splitTyConApp_maybe t
853 -- There may be more than 2 arguments, if the type error is
854 -- used as a type constructor (e.g. at kind `Type -> Type`).
855
856 ; guard (tyConName tc == errorMessageTypeErrorFamName)
857 ; return msg }
858
859 -- | Render a type corresponding to a user type error into a SDoc.
860 pprUserTypeErrorTy :: Type -> SDoc
861 pprUserTypeErrorTy ty =
862 case splitTyConApp_maybe ty of
863
864 -- Text "Something"
865 Just (tc,[txt])
866 | tyConName tc == typeErrorTextDataConName
867 , Just str <- isStrLitTy txt -> ftext str
868
869 -- ShowType t
870 Just (tc,[_k,t])
871 | tyConName tc == typeErrorShowTypeDataConName -> ppr t
872
873 -- t1 :<>: t2
874 Just (tc,[t1,t2])
875 | tyConName tc == typeErrorAppendDataConName ->
876 pprUserTypeErrorTy t1 <> pprUserTypeErrorTy t2
877
878 -- t1 :$$: t2
879 Just (tc,[t1,t2])
880 | tyConName tc == typeErrorVAppendDataConName ->
881 pprUserTypeErrorTy t1 $$ pprUserTypeErrorTy t2
882
883 -- An unevaluated type function
884 _ -> ppr ty
885
886
887
888
889 {-
890 ---------------------------------------------------------------------
891 FunTy
892 ~~~~~
893
894 Note [Representation of function types]
895 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
896
897 Functions (e.g. Int -> Char) are can be thought of as being applications
898 of funTyCon (known in Haskell surface syntax as (->)),
899
900 (->) :: forall (r1 :: RuntimeRep) (r2 :: RuntimeRep)
901 (a :: TYPE r1) (b :: TYPE r2).
902 a -> b -> Type
903
904 However, for efficiency's sake we represent saturated applications of (->)
905 with FunTy. For instance, the type,
906
907 (->) r1 r2 a b
908
909 is equivalent to,
910
911 FunTy (Anon a) b
912
913 Note how the RuntimeReps are implied in the FunTy representation. For this
914 reason we must be careful when recontructing the TyConApp representation (see,
915 for instance, splitTyConApp_maybe).
916
917 In the compiler we maintain the invariant that all saturated applications of
918 (->) are represented with FunTy.
919
920 See #11714.
921 -}
922
923 isFunTy :: Type -> Bool
924 isFunTy ty = isJust (splitFunTy_maybe ty)
925
926 splitFunTy :: Type -> (Type, Type)
927 -- ^ Attempts to extract the argument and result types from a type, and
928 -- panics if that is not possible. See also 'splitFunTy_maybe'
929 splitFunTy ty | Just ty' <- coreView ty = splitFunTy ty'
930 splitFunTy (FunTy arg res) = (arg, res)
931 splitFunTy other = pprPanic "splitFunTy" (ppr other)
932
933 splitFunTy_maybe :: Type -> Maybe (Type, Type)
934 -- ^ Attempts to extract the argument and result types from a type
935 splitFunTy_maybe ty | Just ty' <- coreView ty = splitFunTy_maybe ty'
936 splitFunTy_maybe (FunTy arg res) = Just (arg, res)
937 splitFunTy_maybe _ = Nothing
938
939 splitFunTys :: Type -> ([Type], Type)
940 splitFunTys ty = split [] ty ty
941 where
942 split args orig_ty ty | Just ty' <- coreView ty = split args orig_ty ty'
943 split args _ (FunTy arg res) = split (arg:args) res res
944 split args orig_ty _ = (reverse args, orig_ty)
945
946 funResultTy :: Type -> Type
947 -- ^ Extract the function result type and panic if that is not possible
948 funResultTy ty | Just ty' <- coreView ty = funResultTy ty'
949 funResultTy (FunTy _ res) = res
950 funResultTy ty = pprPanic "funResultTy" (ppr ty)
951
952 funArgTy :: Type -> Type
953 -- ^ Extract the function argument type and panic if that is not possible
954 funArgTy ty | Just ty' <- coreView ty = funArgTy ty'
955 funArgTy (FunTy arg _res) = arg
956 funArgTy ty = pprPanic "funArgTy" (ppr ty)
957
958 piResultTy :: HasDebugCallStack => Type -> Type -> Type
959 piResultTy ty arg = case piResultTy_maybe ty arg of
960 Just res -> res
961 Nothing -> pprPanic "piResultTy" (ppr ty $$ ppr arg)
962
963 piResultTy_maybe :: Type -> Type -> Maybe Type
964
965 -- ^ Just like 'piResultTys' but for a single argument
966 -- Try not to iterate 'piResultTy', because it's inefficient to substitute
967 -- one variable at a time; instead use 'piResultTys"
968 piResultTy_maybe ty arg
969 | Just ty' <- coreView ty = piResultTy_maybe ty' arg
970
971 | FunTy _ res <- ty
972 = Just res
973
974 | ForAllTy (TvBndr tv _) res <- ty
975 = let empty_subst = mkEmptyTCvSubst $ mkInScopeSet $
976 tyCoVarsOfTypes [arg,res]
977 in Just (substTy (extendTvSubst empty_subst tv arg) res)
978
979 | otherwise
980 = Nothing
981
982 -- | (piResultTys f_ty [ty1, .., tyn]) gives the type of (f ty1 .. tyn)
983 -- where f :: f_ty
984 -- 'piResultTys' is interesting because:
985 -- 1. 'f_ty' may have more for-alls than there are args
986 -- 2. Less obviously, it may have fewer for-alls
987 -- For case 2. think of:
988 -- piResultTys (forall a.a) [forall b.b, Int]
989 -- This really can happen, but only (I think) in situations involving
990 -- undefined. For example:
991 -- undefined :: forall a. a
992 -- Term: undefined @(forall b. b->b) @Int
993 -- This term should have type (Int -> Int), but notice that
994 -- there are more type args than foralls in 'undefined's type.
995
996 -- If you edit this function, you may need to update the GHC formalism
997 -- See Note [GHC Formalism] in coreSyn/CoreLint.hs
998
999 -- This is a heavily used function (e.g. from typeKind),
1000 -- so we pay attention to efficiency, especially in the special case
1001 -- where there are no for-alls so we are just dropping arrows from
1002 -- a function type/kind.
1003 piResultTys :: HasDebugCallStack => Type -> [Type] -> Type
1004 piResultTys ty [] = ty
1005 piResultTys ty orig_args@(arg:args)
1006 | Just ty' <- coreView ty
1007 = piResultTys ty' orig_args
1008
1009 | FunTy _ res <- ty
1010 = piResultTys res args
1011
1012 | ForAllTy (TvBndr tv _) res <- ty
1013 = go (extendVarEnv emptyTvSubstEnv tv arg) res args
1014
1015 | otherwise
1016 = pprPanic "piResultTys1" (ppr ty $$ ppr orig_args)
1017 where
1018 in_scope = mkInScopeSet (tyCoVarsOfTypes (ty:orig_args))
1019
1020 go :: TvSubstEnv -> Type -> [Type] -> Type
1021 go tv_env ty [] = substTy (mkTvSubst in_scope tv_env) ty
1022
1023 go tv_env ty all_args@(arg:args)
1024 | Just ty' <- coreView ty
1025 = go tv_env ty' all_args
1026
1027 | FunTy _ res <- ty
1028 = go tv_env res args
1029
1030 | ForAllTy (TvBndr tv _) res <- ty
1031 = go (extendVarEnv tv_env tv arg) res args
1032
1033 | TyVarTy tv <- ty
1034 , Just ty' <- lookupVarEnv tv_env tv
1035 -- Deals with piResultTys (forall a. a) [forall b.b, Int]
1036 = piResultTys ty' all_args
1037
1038 | otherwise
1039 = pprPanic "piResultTys2" (ppr ty $$ ppr orig_args $$ ppr all_args)
1040
1041 applyTysX :: [TyVar] -> Type -> [Type] -> Type
1042 -- applyTyxX beta-reduces (/\tvs. body_ty) arg_tys
1043 -- Assumes that (/\tvs. body_ty) is closed
1044 applyTysX tvs body_ty arg_tys
1045 = ASSERT2( arg_tys `lengthAtLeast` n_tvs, pp_stuff )
1046 ASSERT2( tyCoVarsOfType body_ty `subVarSet` mkVarSet tvs, pp_stuff )
1047 mkAppTys (substTyWith tvs (take n_tvs arg_tys) body_ty)
1048 (drop n_tvs arg_tys)
1049 where
1050 pp_stuff = vcat [ppr tvs, ppr body_ty, ppr arg_tys]
1051 n_tvs = length tvs
1052
1053 {-
1054 ---------------------------------------------------------------------
1055 TyConApp
1056 ~~~~~~~~
1057 -}
1058
1059 -- | A key function: builds a 'TyConApp' or 'FunTy' as appropriate to
1060 -- its arguments. Applies its arguments to the constructor from left to right.
1061 mkTyConApp :: TyCon -> [Type] -> Type
1062 mkTyConApp tycon tys
1063 | isFunTyCon tycon
1064 , [_rep1,_rep2,ty1,ty2] <- tys
1065 = FunTy ty1 ty2
1066
1067 | otherwise
1068 = TyConApp tycon tys
1069
1070 -- splitTyConApp "looks through" synonyms, because they don't
1071 -- mean a distinct type, but all other type-constructor applications
1072 -- including functions are returned as Just ..
1073
1074 -- | Retrieve the tycon heading this type, if there is one. Does /not/
1075 -- look through synonyms.
1076 tyConAppTyConPicky_maybe :: Type -> Maybe TyCon
1077 tyConAppTyConPicky_maybe (TyConApp tc _) = Just tc
1078 tyConAppTyConPicky_maybe (FunTy {}) = Just funTyCon
1079 tyConAppTyConPicky_maybe _ = Nothing
1080
1081
1082 -- | The same as @fst . splitTyConApp@
1083 tyConAppTyCon_maybe :: Type -> Maybe TyCon
1084 tyConAppTyCon_maybe ty | Just ty' <- coreView ty = tyConAppTyCon_maybe ty'
1085 tyConAppTyCon_maybe (TyConApp tc _) = Just tc
1086 tyConAppTyCon_maybe (FunTy {}) = Just funTyCon
1087 tyConAppTyCon_maybe _ = Nothing
1088
1089 tyConAppTyCon :: Type -> TyCon
1090 tyConAppTyCon ty = tyConAppTyCon_maybe ty `orElse` pprPanic "tyConAppTyCon" (ppr ty)
1091
1092 -- | The same as @snd . splitTyConApp@
1093 tyConAppArgs_maybe :: Type -> Maybe [Type]
1094 tyConAppArgs_maybe ty | Just ty' <- coreView ty = tyConAppArgs_maybe ty'
1095 tyConAppArgs_maybe (TyConApp _ tys) = Just tys
1096 tyConAppArgs_maybe (FunTy arg res)
1097 | Just rep1 <- getRuntimeRep_maybe arg
1098 , Just rep2 <- getRuntimeRep_maybe res
1099 = Just [rep1, rep2, arg, res]
1100 tyConAppArgs_maybe _ = Nothing
1101
1102 tyConAppArgs :: Type -> [Type]
1103 tyConAppArgs ty = tyConAppArgs_maybe ty `orElse` pprPanic "tyConAppArgs" (ppr ty)
1104
1105 tyConAppArgN :: Int -> Type -> Type
1106 -- Executing Nth
1107 tyConAppArgN n ty
1108 = case tyConAppArgs_maybe ty of
1109 Just tys -> ASSERT2( tys `lengthExceeds` n, ppr n <+> ppr tys ) tys `getNth` n
1110 Nothing -> pprPanic "tyConAppArgN" (ppr n <+> ppr ty)
1111
1112 -- | Attempts to tease a type apart into a type constructor and the application
1113 -- of a number of arguments to that constructor. Panics if that is not possible.
1114 -- See also 'splitTyConApp_maybe'
1115 splitTyConApp :: Type -> (TyCon, [Type])
1116 splitTyConApp ty = case splitTyConApp_maybe ty of
1117 Just stuff -> stuff
1118 Nothing -> pprPanic "splitTyConApp" (ppr ty)
1119
1120 -- | Attempts to tease a type apart into a type constructor and the application
1121 -- of a number of arguments to that constructor
1122 splitTyConApp_maybe :: HasDebugCallStack => Type -> Maybe (TyCon, [Type])
1123 splitTyConApp_maybe ty | Just ty' <- coreView ty = splitTyConApp_maybe ty'
1124 splitTyConApp_maybe ty = repSplitTyConApp_maybe ty
1125
1126 -- | Like 'splitTyConApp_maybe', but doesn't look through synonyms. This
1127 -- assumes the synonyms have already been dealt with.
1128 repSplitTyConApp_maybe :: HasDebugCallStack => Type -> Maybe (TyCon, [Type])
1129 repSplitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
1130 repSplitTyConApp_maybe (FunTy arg res)
1131 | Just arg_rep <- getRuntimeRep_maybe arg
1132 , Just res_rep <- getRuntimeRep_maybe res
1133 = Just (funTyCon, [arg_rep, res_rep, arg, res])
1134 repSplitTyConApp_maybe _ = Nothing
1135
1136 -- | Attempts to tease a list type apart and gives the type of the elements if
1137 -- successful (looks through type synonyms)
1138 splitListTyConApp_maybe :: Type -> Maybe Type
1139 splitListTyConApp_maybe ty = case splitTyConApp_maybe ty of
1140 Just (tc,[e]) | tc == listTyCon -> Just e
1141 _other -> Nothing
1142
1143 newTyConInstRhs :: TyCon -> [Type] -> Type
1144 -- ^ Unwrap one 'layer' of newtype on a type constructor and its
1145 -- arguments, using an eta-reduced version of the @newtype@ if possible.
1146 -- This requires tys to have at least @newTyConInstArity tycon@ elements.
1147 newTyConInstRhs tycon tys
1148 = ASSERT2( tvs `leLength` tys, ppr tycon $$ ppr tys $$ ppr tvs )
1149 applyTysX tvs rhs tys
1150 where
1151 (tvs, rhs) = newTyConEtadRhs tycon
1152
1153 {-
1154 ---------------------------------------------------------------------
1155 CastTy
1156 ~~~~~~
1157 A casted type has its *kind* casted into something new.
1158
1159 -}
1160
1161 splitCastTy_maybe :: Type -> Maybe (Type, Coercion)
1162 splitCastTy_maybe ty | Just ty' <- coreView ty = splitCastTy_maybe ty'
1163 splitCastTy_maybe (CastTy ty co) = Just (ty, co)
1164 splitCastTy_maybe _ = Nothing
1165
1166 -- | Make a 'CastTy'. The Coercion must be nominal. Checks the
1167 -- Coercion for reflexivity, dropping it if it's reflexive.
1168 -- See Note [Respecting definitional equality] in TyCoRep
1169 mkCastTy :: Type -> Coercion -> Type
1170 mkCastTy ty co | isReflexiveCo co = ty -- (EQ2) from the Note
1171 -- NB: Do the slow check here. This is important to keep the splitXXX
1172 -- functions working properly. Otherwise, we may end up with something
1173 -- like (((->) |> something_reflexive_but_not_obviously_so) biz baz)
1174 -- fails under splitFunTy_maybe. This happened with the cheaper check
1175 -- in test dependent/should_compile/dynamic-paper.
1176
1177 mkCastTy (CastTy ty co1) co2 = mkCastTy ty (co1 `mkTransCo` co2) -- (EQ3) from the Note
1178 -- call mkCastTy again for the reflexivity check
1179 mkCastTy ty co = CastTy ty co
1180
1181 tyConBindersTyBinders :: [TyConBinder] -> [TyBinder]
1182 -- Return the tyConBinders in TyBinder form
1183 tyConBindersTyBinders = map to_tyb
1184 where
1185 to_tyb (TvBndr tv (NamedTCB vis)) = Named (TvBndr tv vis)
1186 to_tyb (TvBndr tv AnonTCB) = Anon (tyVarKind tv)
1187
1188 {-
1189 --------------------------------------------------------------------
1190 CoercionTy
1191 ~~~~~~~~~~
1192 CoercionTy allows us to inject coercions into types. A CoercionTy
1193 should appear only in the right-hand side of an application.
1194 -}
1195
1196 mkCoercionTy :: Coercion -> Type
1197 mkCoercionTy = CoercionTy
1198
1199 isCoercionTy :: Type -> Bool
1200 isCoercionTy (CoercionTy _) = True
1201 isCoercionTy _ = False
1202
1203 isCoercionTy_maybe :: Type -> Maybe Coercion
1204 isCoercionTy_maybe (CoercionTy co) = Just co
1205 isCoercionTy_maybe _ = Nothing
1206
1207 stripCoercionTy :: Type -> Coercion
1208 stripCoercionTy (CoercionTy co) = co
1209 stripCoercionTy ty = pprPanic "stripCoercionTy" (ppr ty)
1210
1211 {-
1212 ---------------------------------------------------------------------
1213 SynTy
1214 ~~~~~
1215
1216 Notes on type synonyms
1217 ~~~~~~~~~~~~~~~~~~~~~~
1218 The various "split" functions (splitFunTy, splitRhoTy, splitForAllTy) try
1219 to return type synonyms wherever possible. Thus
1220
1221 type Foo a = a -> a
1222
1223 we want
1224 splitFunTys (a -> Foo a) = ([a], Foo a)
1225 not ([a], a -> a)
1226
1227 The reason is that we then get better (shorter) type signatures in
1228 interfaces. Notably this plays a role in tcTySigs in TcBinds.hs.
1229
1230
1231 ---------------------------------------------------------------------
1232 ForAllTy
1233 ~~~~~~~~
1234 -}
1235
1236 -- | Make a dependent forall over an Inferred (as opposed to Specified)
1237 -- variable
1238 mkInvForAllTy :: TyVar -> Type -> Type
1239 mkInvForAllTy tv ty = ASSERT( isTyVar tv )
1240 ForAllTy (TvBndr tv Inferred) ty
1241
1242 -- | Like mkForAllTys, but assumes all variables are dependent and Inferred,
1243 -- a common case
1244 mkInvForAllTys :: [TyVar] -> Type -> Type
1245 mkInvForAllTys tvs ty = ASSERT( all isTyVar tvs )
1246 foldr mkInvForAllTy ty tvs
1247
1248 -- | Like mkForAllTys, but assumes all variables are dependent and specified,
1249 -- a common case
1250 mkSpecForAllTys :: [TyVar] -> Type -> Type
1251 mkSpecForAllTys tvs = ASSERT( all isTyVar tvs )
1252 mkForAllTys [ TvBndr tv Specified | tv <- tvs ]
1253
1254 -- | Like mkForAllTys, but assumes all variables are dependent and visible
1255 mkVisForAllTys :: [TyVar] -> Type -> Type
1256 mkVisForAllTys tvs = ASSERT( all isTyVar tvs )
1257 mkForAllTys [ TvBndr tv Required | tv <- tvs ]
1258
1259 mkLamType :: Var -> Type -> Type
1260 -- ^ Makes a @(->)@ type or an implicit forall type, depending
1261 -- on whether it is given a type variable or a term variable.
1262 -- This is used, for example, when producing the type of a lambda.
1263 -- Always uses Inferred binders.
1264 mkLamTypes :: [Var] -> Type -> Type
1265 -- ^ 'mkLamType' for multiple type or value arguments
1266
1267 mkLamType v ty
1268 | isTyVar v = ForAllTy (TvBndr v Inferred) ty
1269 | otherwise = FunTy (varType v) ty
1270
1271 mkLamTypes vs ty = foldr mkLamType ty vs
1272
1273 -- | Given a list of type-level vars and a result kind,
1274 -- makes TyBinders, preferring anonymous binders
1275 -- if the variable is, in fact, not dependent.
1276 -- e.g. mkTyConBindersPreferAnon [(k:*),(b:k),(c:k)] (k->k)
1277 -- We want (k:*) Named, (a;k) Anon, (c:k) Anon
1278 --
1279 -- All binders are /visible/.
1280 mkTyConBindersPreferAnon :: [TyVar] -> Type -> [TyConBinder]
1281 mkTyConBindersPreferAnon vars inner_ty = fst (go vars)
1282 where
1283 go :: [TyVar] -> ([TyConBinder], VarSet) -- also returns the free vars
1284 go [] = ([], tyCoVarsOfType inner_ty)
1285 go (v:vs) | v `elemVarSet` fvs
1286 = ( TvBndr v (NamedTCB Required) : binders
1287 , fvs `delVarSet` v `unionVarSet` kind_vars )
1288 | otherwise
1289 = ( TvBndr v AnonTCB : binders
1290 , fvs `unionVarSet` kind_vars )
1291 where
1292 (binders, fvs) = go vs
1293 kind_vars = tyCoVarsOfType $ tyVarKind v
1294
1295 -- | Take a ForAllTy apart, returning the list of tyvars and the result type.
1296 -- This always succeeds, even if it returns only an empty list. Note that the
1297 -- result type returned may have free variables that were bound by a forall.
1298 splitForAllTys :: Type -> ([TyVar], Type)
1299 splitForAllTys ty = split ty ty []
1300 where
1301 split orig_ty ty tvs | Just ty' <- coreView ty = split orig_ty ty' tvs
1302 split _ (ForAllTy (TvBndr tv _) ty) tvs = split ty ty (tv:tvs)
1303 split orig_ty _ tvs = (reverse tvs, orig_ty)
1304
1305 -- | Like 'splitPiTys' but split off only /named/ binders.
1306 splitForAllTyVarBndrs :: Type -> ([TyVarBinder], Type)
1307 splitForAllTyVarBndrs ty = split ty ty []
1308 where
1309 split orig_ty ty bs | Just ty' <- coreView ty = split orig_ty ty' bs
1310 split _ (ForAllTy b res) bs = split res res (b:bs)
1311 split orig_ty _ bs = (reverse bs, orig_ty)
1312
1313 -- | Checks whether this is a proper forall (with a named binder)
1314 isForAllTy :: Type -> Bool
1315 isForAllTy ty | Just ty' <- coreView ty = isForAllTy ty'
1316 isForAllTy (ForAllTy {}) = True
1317 isForAllTy _ = False
1318
1319 -- | Is this a function or forall?
1320 isPiTy :: Type -> Bool
1321 isPiTy ty | Just ty' <- coreView ty = isForAllTy ty'
1322 isPiTy (ForAllTy {}) = True
1323 isPiTy (FunTy {}) = True
1324 isPiTy _ = False
1325
1326 -- | Take a forall type apart, or panics if that is not possible.
1327 splitForAllTy :: Type -> (TyVar, Type)
1328 splitForAllTy ty
1329 | Just answer <- splitForAllTy_maybe ty = answer
1330 | otherwise = pprPanic "splitForAllTy" (ppr ty)
1331
1332 -- | Drops all ForAllTys
1333 dropForAlls :: Type -> Type
1334 dropForAlls ty = go ty
1335 where
1336 go ty | Just ty' <- coreView ty = go ty'
1337 go (ForAllTy _ res) = go res
1338 go res = res
1339
1340 -- | Attempts to take a forall type apart, but only if it's a proper forall,
1341 -- with a named binder
1342 splitForAllTy_maybe :: Type -> Maybe (TyVar, Type)
1343 splitForAllTy_maybe ty = go ty
1344 where
1345 go ty | Just ty' <- coreView ty = go ty'
1346 go (ForAllTy (TvBndr tv _) ty) = Just (tv, ty)
1347 go _ = Nothing
1348
1349 -- | Attempts to take a forall type apart; works with proper foralls and
1350 -- functions
1351 splitPiTy_maybe :: Type -> Maybe (TyBinder, Type)
1352 splitPiTy_maybe ty = go ty
1353 where
1354 go ty | Just ty' <- coreView ty = go ty'
1355 go (ForAllTy bndr ty) = Just (Named bndr, ty)
1356 go (FunTy arg res) = Just (Anon arg, res)
1357 go _ = Nothing
1358
1359 -- | Takes a forall type apart, or panics
1360 splitPiTy :: Type -> (TyBinder, Type)
1361 splitPiTy ty
1362 | Just answer <- splitPiTy_maybe ty = answer
1363 | otherwise = pprPanic "splitPiTy" (ppr ty)
1364
1365 -- | Split off all TyBinders to a type, splitting both proper foralls
1366 -- and functions
1367 splitPiTys :: Type -> ([TyBinder], Type)
1368 splitPiTys ty = split ty ty []
1369 where
1370 split orig_ty ty bs | Just ty' <- coreView ty = split orig_ty ty' bs
1371 split _ (ForAllTy b res) bs = split res res (Named b : bs)
1372 split _ (FunTy arg res) bs = split res res (Anon arg : bs)
1373 split orig_ty _ bs = (reverse bs, orig_ty)
1374
1375 -- Like splitPiTys, but returns only *invisible* binders, including constraints
1376 -- Stops at the first visible binder
1377 splitPiTysInvisible :: Type -> ([TyBinder], Type)
1378 splitPiTysInvisible ty = split ty ty []
1379 where
1380 split orig_ty ty bs | Just ty' <- coreView ty = split orig_ty ty' bs
1381 split _ (ForAllTy b@(TvBndr _ vis) res) bs
1382 | isInvisibleArgFlag vis = split res res (Named b : bs)
1383 split _ (FunTy arg res) bs
1384 | isPredTy arg = split res res (Anon arg : bs)
1385 split orig_ty _ bs = (reverse bs, orig_ty)
1386
1387 -- | Given a tycon and its arguments, filters out any invisible arguments
1388 filterOutInvisibleTypes :: TyCon -> [Type] -> [Type]
1389 filterOutInvisibleTypes tc tys = snd $ partitionInvisibles tc id tys
1390
1391 -- | Given a tycon and a list of things (which correspond to arguments),
1392 -- partitions the things into
1393 -- Inferred or Specified ones and
1394 -- Required ones
1395 -- The callback function is necessary for this scenario:
1396 --
1397 -- > T :: forall k. k -> k
1398 -- > partitionInvisibles T [forall m. m -> m -> m, S, R, Q]
1399 --
1400 -- After substituting, we get
1401 --
1402 -- > T (forall m. m -> m -> m) :: (forall m. m -> m -> m) -> forall n. n -> n -> n
1403 --
1404 -- Thus, the first argument is invisible, @S@ is visible, @R@ is invisible again,
1405 -- and @Q@ is visible.
1406 --
1407 -- If you're absolutely sure that your tycon's kind doesn't end in a variable,
1408 -- it's OK if the callback function panics, as that's the only time it's
1409 -- consulted.
1410 partitionInvisibles :: TyCon -> (a -> Type) -> [a] -> ([a], [a])
1411 partitionInvisibles tc get_ty = go emptyTCvSubst (tyConKind tc)
1412 where
1413 go _ _ [] = ([], [])
1414 go subst (ForAllTy (TvBndr tv vis) res_ki) (x:xs)
1415 | isVisibleArgFlag vis = second (x :) (go subst' res_ki xs)
1416 | otherwise = first (x :) (go subst' res_ki xs)
1417 where
1418 subst' = extendTvSubst subst tv (get_ty x)
1419 go subst (TyVarTy tv) xs
1420 | Just ki <- lookupTyVar subst tv = go subst ki xs
1421 go _ _ xs = ([], xs) -- something is ill-kinded. But this can happen
1422 -- when printing errors. Assume everything is visible.
1423
1424 -- @isTauTy@ tests if a type has no foralls
1425 isTauTy :: Type -> Bool
1426 isTauTy ty | Just ty' <- coreView ty = isTauTy ty'
1427 isTauTy (TyVarTy _) = True
1428 isTauTy (LitTy {}) = True
1429 isTauTy (TyConApp tc tys) = all isTauTy tys && isTauTyCon tc
1430 isTauTy (AppTy a b) = isTauTy a && isTauTy b
1431 isTauTy (FunTy a b) = isTauTy a && isTauTy b
1432 isTauTy (ForAllTy {}) = False
1433 isTauTy (CastTy ty _) = isTauTy ty
1434 isTauTy (CoercionTy _) = False -- Not sure about this
1435
1436 {-
1437 %************************************************************************
1438 %* *
1439 TyBinders
1440 %* *
1441 %************************************************************************
1442 -}
1443
1444 -- | Make an anonymous binder
1445 mkAnonBinder :: Type -> TyBinder
1446 mkAnonBinder = Anon
1447
1448 -- | Does this binder bind a variable that is /not/ erased? Returns
1449 -- 'True' for anonymous binders.
1450 isAnonTyBinder :: TyBinder -> Bool
1451 isAnonTyBinder (Named {}) = False
1452 isAnonTyBinder (Anon {}) = True
1453
1454 isNamedTyBinder :: TyBinder -> Bool
1455 isNamedTyBinder (Named {}) = True
1456 isNamedTyBinder (Anon {}) = False
1457
1458 tyBinderVar_maybe :: TyBinder -> Maybe TyVar
1459 tyBinderVar_maybe (Named tv) = Just $ binderVar tv
1460 tyBinderVar_maybe _ = Nothing
1461
1462 tyBinderType :: TyBinder -> Type
1463 -- Barely used
1464 tyBinderType (Named tvb) = binderKind tvb
1465 tyBinderType (Anon ty) = ty
1466
1467 -- | Extract a relevant type, if there is one.
1468 binderRelevantType_maybe :: TyBinder -> Maybe Type
1469 binderRelevantType_maybe (Named {}) = Nothing
1470 binderRelevantType_maybe (Anon ty) = Just ty
1471
1472 -- | Like 'maybe', but for binders.
1473 caseBinder :: TyBinder -- ^ binder to scrutinize
1474 -> (TyVarBinder -> a) -- ^ named case
1475 -> (Type -> a) -- ^ anonymous case
1476 -> a
1477 caseBinder (Named v) f _ = f v
1478 caseBinder (Anon t) _ d = d t
1479
1480
1481 {-
1482 %************************************************************************
1483 %* *
1484 Pred
1485 * *
1486 ************************************************************************
1487
1488 Predicates on PredType
1489
1490 Note [isPredTy complications]
1491 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1492 You would think that we could define
1493 isPredTy ty = isConstraintKind (typeKind ty)
1494 But there are a number of complications:
1495
1496 * isPredTy is used when printing types, which can happen in debug
1497 printing during type checking of not-fully-zonked types. So it's
1498 not cool to say isConstraintKind (typeKind ty) because, absent
1499 zonking, the type might be ill-kinded, and typeKind crashes. Hence the
1500 rather tiresome story here
1501
1502 * isPredTy must return "True" to *unlifted* coercions, such as (t1 ~# t2)
1503 and (t1 ~R# t2), which are not of kind Constraint! Currently they are
1504 of kind #.
1505
1506 * If we do form the type '(C a => C [a]) => blah', then we'd like to
1507 print it as such. But that means that isPredTy must return True for
1508 (C a => C [a]). Admittedly that type is illegal in Haskell, but we
1509 want to print it nicely in error messages.
1510 -}
1511
1512 -- | Is the type suitable to classify a given/wanted in the typechecker?
1513 isPredTy :: Type -> Bool
1514 -- See Note [isPredTy complications]
1515 isPredTy ty = go ty []
1516 where
1517 go :: Type -> [KindOrType] -> Bool
1518 go (AppTy ty1 ty2) args = go ty1 (ty2 : args)
1519 go (TyVarTy tv) args = go_k (tyVarKind tv) args
1520 go (TyConApp tc tys) args = ASSERT( null args ) -- TyConApp invariant
1521 go_tc tc tys
1522 go (FunTy arg res) []
1523 | isPredTy arg = isPredTy res -- (Eq a => C a)
1524 | otherwise = False -- (Int -> Bool)
1525 go (ForAllTy _ ty) [] = go ty []
1526 go (CastTy _ co) args = go_k (pSnd (coercionKind co)) args
1527 go _ _ = False
1528
1529 go_tc :: TyCon -> [KindOrType] -> Bool
1530 go_tc tc args
1531 | tc `hasKey` eqPrimTyConKey || tc `hasKey` eqReprPrimTyConKey
1532 = args `lengthIs` 4 -- ~# and ~R# sadly have result kind #
1533 -- not Constraint; but we still want
1534 -- isPredTy to reply True.
1535 | otherwise = go_k (tyConKind tc) args
1536
1537 go_k :: Kind -> [KindOrType] -> Bool
1538 -- True <=> ('k' applied to 'kts') = Constraint
1539 go_k k [] = isConstraintKind k
1540 go_k k (arg:args) = case piResultTy_maybe k arg of
1541 Just k' -> go_k k' args
1542 Nothing -> WARN( True, text "isPredTy" <+> ppr ty )
1543 False
1544 -- This last case shouldn't happen under most circumstances. It can
1545 -- occur if we call isPredTy during kind checking, especially if one
1546 -- of the following happens:
1547 --
1548 -- 1. There is actually a kind error. Example in which this showed up:
1549 -- polykinds/T11399
1550 --
1551 -- 2. A type constructor application appears to be oversaturated. An
1552 -- example of this occurred in GHC Trac #13187:
1553 --
1554 -- {-# LANGUAGE PolyKinds #-}
1555 -- type Const a b = b
1556 -- f :: Const Int (,) Bool Char -> Char
1557 --
1558 -- We call isPredTy (Const k1 k2 Int (,) Bool Char
1559 -- where k1,k2 are unification variables that have been
1560 -- unified to *, and (*->*->*) resp, /but not zonked/.
1561 -- This shows that isPredTy can report a false negative
1562 -- if a constraint is similarly oversaturated, but
1563 -- it's hard to do better than isPredTy currently does without
1564 -- zonking, so we punt on such cases for now. This only happens
1565 -- during debug-printing, so it doesn't matter.
1566
1567 isClassPred, isEqPred, isNomEqPred, isIPPred :: PredType -> Bool
1568 isClassPred ty = case tyConAppTyCon_maybe ty of
1569 Just tyCon | isClassTyCon tyCon -> True
1570 _ -> False
1571 isEqPred ty = case tyConAppTyCon_maybe ty of
1572 Just tyCon -> tyCon `hasKey` eqPrimTyConKey
1573 || tyCon `hasKey` eqReprPrimTyConKey
1574 _ -> False
1575
1576 isNomEqPred ty = case tyConAppTyCon_maybe ty of
1577 Just tyCon -> tyCon `hasKey` eqPrimTyConKey
1578 _ -> False
1579
1580 isIPPred ty = case tyConAppTyCon_maybe ty of
1581 Just tc -> isIPTyCon tc
1582 _ -> False
1583
1584 isIPTyCon :: TyCon -> Bool
1585 isIPTyCon tc = tc `hasKey` ipClassKey
1586 -- Class and its corresponding TyCon have the same Unique
1587
1588 isIPClass :: Class -> Bool
1589 isIPClass cls = cls `hasKey` ipClassKey
1590
1591 isCTupleClass :: Class -> Bool
1592 isCTupleClass cls = isTupleTyCon (classTyCon cls)
1593
1594 isIPPred_maybe :: Type -> Maybe (FastString, Type)
1595 isIPPred_maybe ty =
1596 do (tc,[t1,t2]) <- splitTyConApp_maybe ty
1597 guard (isIPTyCon tc)
1598 x <- isStrLitTy t1
1599 return (x,t2)
1600
1601 {-
1602 Make PredTypes
1603
1604 --------------------- Equality types ---------------------------------
1605 -}
1606
1607 -- | Makes a lifted equality predicate at the given role
1608 mkPrimEqPredRole :: Role -> Type -> Type -> PredType
1609 mkPrimEqPredRole Nominal = mkPrimEqPred
1610 mkPrimEqPredRole Representational = mkReprPrimEqPred
1611 mkPrimEqPredRole Phantom = panic "mkPrimEqPredRole phantom"
1612
1613 -- | Creates a primitive type equality predicate.
1614 -- Invariant: the types are not Coercions
1615 mkPrimEqPred :: Type -> Type -> Type
1616 mkPrimEqPred ty1 ty2
1617 = TyConApp eqPrimTyCon [k1, k2, ty1, ty2]
1618 where
1619 k1 = typeKind ty1
1620 k2 = typeKind ty2
1621
1622 -- | Creates a primite type equality predicate with explicit kinds
1623 mkHeteroPrimEqPred :: Kind -> Kind -> Type -> Type -> Type
1624 mkHeteroPrimEqPred k1 k2 ty1 ty2 = TyConApp eqPrimTyCon [k1, k2, ty1, ty2]
1625
1626 -- | Creates a primitive representational type equality predicate
1627 -- with explicit kinds
1628 mkHeteroReprPrimEqPred :: Kind -> Kind -> Type -> Type -> Type
1629 mkHeteroReprPrimEqPred k1 k2 ty1 ty2
1630 = TyConApp eqReprPrimTyCon [k1, k2, ty1, ty2]
1631
1632 -- | Try to split up a coercion type into the types that it coerces
1633 splitCoercionType_maybe :: Type -> Maybe (Type, Type)
1634 splitCoercionType_maybe ty
1635 = do { (tc, [_, _, ty1, ty2]) <- splitTyConApp_maybe ty
1636 ; guard $ tc `hasKey` eqPrimTyConKey || tc `hasKey` eqReprPrimTyConKey
1637 ; return (ty1, ty2) }
1638
1639 mkReprPrimEqPred :: Type -> Type -> Type
1640 mkReprPrimEqPred ty1 ty2
1641 = TyConApp eqReprPrimTyCon [k1, k2, ty1, ty2]
1642 where
1643 k1 = typeKind ty1
1644 k2 = typeKind ty2
1645
1646 equalityTyCon :: Role -> TyCon
1647 equalityTyCon Nominal = eqPrimTyCon
1648 equalityTyCon Representational = eqReprPrimTyCon
1649 equalityTyCon Phantom = eqPhantPrimTyCon
1650
1651 -- --------------------- Dictionary types ---------------------------------
1652
1653 mkClassPred :: Class -> [Type] -> PredType
1654 mkClassPred clas tys = TyConApp (classTyCon clas) tys
1655
1656 isDictTy :: Type -> Bool
1657 isDictTy = isClassPred
1658
1659 isDictLikeTy :: Type -> Bool
1660 -- Note [Dictionary-like types]
1661 isDictLikeTy ty | Just ty' <- coreView ty = isDictLikeTy ty'
1662 isDictLikeTy ty = case splitTyConApp_maybe ty of
1663 Just (tc, tys) | isClassTyCon tc -> True
1664 | isTupleTyCon tc -> all isDictLikeTy tys
1665 _other -> False
1666
1667 {-
1668 Note [Dictionary-like types]
1669 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1670 Being "dictionary-like" means either a dictionary type or a tuple thereof.
1671 In GHC 6.10 we build implication constraints which construct such tuples,
1672 and if we land up with a binding
1673 t :: (C [a], Eq [a])
1674 t = blah
1675 then we want to treat t as cheap under "-fdicts-cheap" for example.
1676 (Implication constraints are normally inlined, but sadly not if the
1677 occurrence is itself inside an INLINE function! Until we revise the
1678 handling of implication constraints, that is.) This turned out to
1679 be important in getting good arities in DPH code. Example:
1680
1681 class C a
1682 class D a where { foo :: a -> a }
1683 instance C a => D (Maybe a) where { foo x = x }
1684
1685 bar :: (C a, C b) => a -> b -> (Maybe a, Maybe b)
1686 {-# INLINE bar #-}
1687 bar x y = (foo (Just x), foo (Just y))
1688
1689 Then 'bar' should jolly well have arity 4 (two dicts, two args), but
1690 we ended up with something like
1691 bar = __inline_me__ (\d1,d2. let t :: (D (Maybe a), D (Maybe b)) = ...
1692 in \x,y. <blah>)
1693
1694 This is all a bit ad-hoc; eg it relies on knowing that implication
1695 constraints build tuples.
1696
1697
1698 Decomposing PredType
1699 -}
1700
1701 -- | A choice of equality relation. This is separate from the type 'Role'
1702 -- because 'Phantom' does not define a (non-trivial) equality relation.
1703 data EqRel = NomEq | ReprEq
1704 deriving (Eq, Ord)
1705
1706 instance Outputable EqRel where
1707 ppr NomEq = text "nominal equality"
1708 ppr ReprEq = text "representational equality"
1709
1710 eqRelRole :: EqRel -> Role
1711 eqRelRole NomEq = Nominal
1712 eqRelRole ReprEq = Representational
1713
1714 data PredTree = ClassPred Class [Type]
1715 | EqPred EqRel Type Type
1716 | IrredPred PredType
1717 -- NB: There is no TuplePred case
1718 -- Tuple predicates like (Eq a, Ord b) are just treated
1719 -- as ClassPred, as if we had a tuple class with two superclasses
1720 -- class (c1, c2) => (%,%) c1 c2
1721
1722 classifyPredType :: PredType -> PredTree
1723 classifyPredType ev_ty = case splitTyConApp_maybe ev_ty of
1724 Just (tc, [_, _, ty1, ty2])
1725 | tc `hasKey` eqReprPrimTyConKey -> EqPred ReprEq ty1 ty2
1726 | tc `hasKey` eqPrimTyConKey -> EqPred NomEq ty1 ty2
1727 Just (tc, tys)
1728 | Just clas <- tyConClass_maybe tc -> ClassPred clas tys
1729 _ -> IrredPred ev_ty
1730
1731 getClassPredTys :: HasDebugCallStack => PredType -> (Class, [Type])
1732 getClassPredTys ty = case getClassPredTys_maybe ty of
1733 Just (clas, tys) -> (clas, tys)
1734 Nothing -> pprPanic "getClassPredTys" (ppr ty)
1735
1736 getClassPredTys_maybe :: PredType -> Maybe (Class, [Type])
1737 getClassPredTys_maybe ty = case splitTyConApp_maybe ty of
1738 Just (tc, tys) | Just clas <- tyConClass_maybe tc -> Just (clas, tys)
1739 _ -> Nothing
1740
1741 getEqPredTys :: PredType -> (Type, Type)
1742 getEqPredTys ty
1743 = case splitTyConApp_maybe ty of
1744 Just (tc, [_, _, ty1, ty2])
1745 | tc `hasKey` eqPrimTyConKey
1746 || tc `hasKey` eqReprPrimTyConKey
1747 -> (ty1, ty2)
1748 _ -> pprPanic "getEqPredTys" (ppr ty)
1749
1750 getEqPredTys_maybe :: PredType -> Maybe (Role, Type, Type)
1751 getEqPredTys_maybe ty
1752 = case splitTyConApp_maybe ty of
1753 Just (tc, [_, _, ty1, ty2])
1754 | tc `hasKey` eqPrimTyConKey -> Just (Nominal, ty1, ty2)
1755 | tc `hasKey` eqReprPrimTyConKey -> Just (Representational, ty1, ty2)
1756 _ -> Nothing
1757
1758 getEqPredRole :: PredType -> Role
1759 getEqPredRole ty = eqRelRole (predTypeEqRel ty)
1760
1761 -- | Get the equality relation relevant for a pred type.
1762 predTypeEqRel :: PredType -> EqRel
1763 predTypeEqRel ty
1764 | Just (tc, _) <- splitTyConApp_maybe ty
1765 , tc `hasKey` eqReprPrimTyConKey
1766 = ReprEq
1767 | otherwise
1768 = NomEq
1769
1770 {-
1771 %************************************************************************
1772 %* *
1773 Well-scoped tyvars
1774 * *
1775 ************************************************************************
1776 -}
1777
1778 -- | Do a topological sort on a list of tyvars,
1779 -- so that binders occur before occurrences
1780 -- E.g. given [ a::k, k::*, b::k ]
1781 -- it'll return a well-scoped list [ k::*, a::k, b::k ]
1782 --
1783 -- This is a deterministic sorting operation
1784 -- (that is, doesn't depend on Uniques).
1785 toposortTyVars :: [TyCoVar] -> [TyCoVar]
1786 toposortTyVars tvs = reverse $
1787 [ node_payload node | node <- topologicalSortG $
1788 graphFromEdgedVerticesOrd nodes ]
1789 where
1790 var_ids :: VarEnv Int
1791 var_ids = mkVarEnv (zip tvs [1..])
1792
1793 nodes :: [ Node Int TyVar ]
1794 nodes = [ DigraphNode
1795 tv
1796 (lookupVarEnv_NF var_ids tv)
1797 (mapMaybe (lookupVarEnv var_ids)
1798 (tyCoVarsOfTypeList (tyVarKind tv)))
1799 | tv <- tvs ]
1800
1801 -- | Extract a well-scoped list of variables from a deterministic set of
1802 -- variables. The result is deterministic.
1803 -- NB: There used to exist varSetElemsWellScoped :: VarSet -> [Var] which
1804 -- took a non-deterministic set and produced a non-deterministic
1805 -- well-scoped list. If you care about the list being well-scoped you also
1806 -- most likely care about it being in deterministic order.
1807 dVarSetElemsWellScoped :: DVarSet -> [Var]
1808 dVarSetElemsWellScoped = toposortTyVars . dVarSetElems
1809
1810 -- | Get the free vars of a type in scoped order
1811 tyCoVarsOfTypeWellScoped :: Type -> [TyVar]
1812 tyCoVarsOfTypeWellScoped = toposortTyVars . tyCoVarsOfTypeList
1813
1814 -- | Get the free vars of types in scoped order
1815 tyCoVarsOfTypesWellScoped :: [Type] -> [TyVar]
1816 tyCoVarsOfTypesWellScoped = toposortTyVars . tyCoVarsOfTypesList
1817
1818 {-
1819 ************************************************************************
1820 * *
1821 \subsection{Type families}
1822 * *
1823 ************************************************************************
1824 -}
1825
1826 mkFamilyTyConApp :: TyCon -> [Type] -> Type
1827 -- ^ Given a family instance TyCon and its arg types, return the
1828 -- corresponding family type. E.g:
1829 --
1830 -- > data family T a
1831 -- > data instance T (Maybe b) = MkT b
1832 --
1833 -- Where the instance tycon is :RTL, so:
1834 --
1835 -- > mkFamilyTyConApp :RTL Int = T (Maybe Int)
1836 mkFamilyTyConApp tc tys
1837 | Just (fam_tc, fam_tys) <- tyConFamInst_maybe tc
1838 , let tvs = tyConTyVars tc
1839 fam_subst = ASSERT2( tvs `equalLength` tys, ppr tc <+> ppr tys )
1840 zipTvSubst tvs tys
1841 = mkTyConApp fam_tc (substTys fam_subst fam_tys)
1842 | otherwise
1843 = mkTyConApp tc tys
1844
1845 -- | Get the type on the LHS of a coercion induced by a type/data
1846 -- family instance.
1847 coAxNthLHS :: CoAxiom br -> Int -> Type
1848 coAxNthLHS ax ind =
1849 mkTyConApp (coAxiomTyCon ax) (coAxBranchLHS (coAxiomNthBranch ax ind))
1850
1851 -- | Pretty prints a 'TyCon', using the family instance in case of a
1852 -- representation tycon. For example:
1853 --
1854 -- > data T [a] = ...
1855 --
1856 -- In that case we want to print @T [a]@, where @T@ is the family 'TyCon'
1857 pprSourceTyCon :: TyCon -> SDoc
1858 pprSourceTyCon tycon
1859 | Just (fam_tc, tys) <- tyConFamInst_maybe tycon
1860 = ppr $ fam_tc `TyConApp` tys -- can't be FunTyCon
1861 | otherwise
1862 = ppr tycon
1863
1864 -- @isTauTy@ tests if a type has no foralls
1865 isFamFreeTy :: Type -> Bool
1866 isFamFreeTy ty | Just ty' <- coreView ty = isFamFreeTy ty'
1867 isFamFreeTy (TyVarTy _) = True
1868 isFamFreeTy (LitTy {}) = True
1869 isFamFreeTy (TyConApp tc tys) = all isFamFreeTy tys && isFamFreeTyCon tc
1870 isFamFreeTy (AppTy a b) = isFamFreeTy a && isFamFreeTy b
1871 isFamFreeTy (FunTy a b) = isFamFreeTy a && isFamFreeTy b
1872 isFamFreeTy (ForAllTy _ ty) = isFamFreeTy ty
1873 isFamFreeTy (CastTy ty _) = isFamFreeTy ty
1874 isFamFreeTy (CoercionTy _) = False -- Not sure about this
1875
1876 {-
1877 ************************************************************************
1878 * *
1879 \subsection{Liftedness}
1880 * *
1881 ************************************************************************
1882 -}
1883
1884 -- | Returns Just True if this type is surely lifted, Just False
1885 -- if it is surely unlifted, Nothing if we can't be sure (i.e., it is
1886 -- levity polymorphic), and panics if the kind does not have the shape
1887 -- TYPE r.
1888 isLiftedType_maybe :: HasDebugCallStack => Type -> Maybe Bool
1889 isLiftedType_maybe ty = go (getRuntimeRep ty)
1890 where
1891 go rr | Just rr' <- coreView rr = go rr'
1892 go (TyConApp lifted_rep [])
1893 | lifted_rep `hasKey` liftedRepDataConKey = Just True
1894 go (TyConApp {}) = Just False -- everything else is unlifted
1895 go _ = Nothing -- levity polymorphic
1896
1897 -- | See "Type#type_classification" for what an unlifted type is.
1898 -- Panics on levity polymorphic types.
1899 isUnliftedType :: HasDebugCallStack => Type -> Bool
1900 -- isUnliftedType returns True for forall'd unlifted types:
1901 -- x :: forall a. Int#
1902 -- I found bindings like these were getting floated to the top level.
1903 -- They are pretty bogus types, mind you. It would be better never to
1904 -- construct them
1905 isUnliftedType ty
1906 = not (isLiftedType_maybe ty `orElse`
1907 pprPanic "isUnliftedType" (ppr ty <+> dcolon <+> ppr (typeKind ty)))
1908
1909 -- | Is this a type of kind RuntimeRep? (e.g. LiftedRep)
1910 isRuntimeRepKindedTy :: Type -> Bool
1911 isRuntimeRepKindedTy = isRuntimeRepTy . typeKind
1912
1913 -- | Drops prefix of RuntimeRep constructors in 'TyConApp's. Useful for e.g.
1914 -- dropping 'LiftedRep arguments of unboxed tuple TyCon applications:
1915 --
1916 -- dropRuntimeRepArgs [ 'LiftedRep, 'IntRep
1917 -- , String, Int# ] == [String, Int#]
1918 --
1919 dropRuntimeRepArgs :: [Type] -> [Type]
1920 dropRuntimeRepArgs = dropWhile isRuntimeRepKindedTy
1921
1922 -- | Extract the RuntimeRep classifier of a type. For instance,
1923 -- @getRuntimeRep_maybe Int = LiftedRep@. Returns 'Nothing' if this is not
1924 -- possible.
1925 getRuntimeRep_maybe :: HasDebugCallStack
1926 => Type -> Maybe Type
1927 getRuntimeRep_maybe = getRuntimeRepFromKind_maybe . typeKind
1928
1929 -- | Extract the RuntimeRep classifier of a type. For instance,
1930 -- @getRuntimeRep_maybe Int = LiftedRep@. Panics if this is not possible.
1931 getRuntimeRep :: HasDebugCallStack => Type -> Type
1932 getRuntimeRep ty
1933 = case getRuntimeRep_maybe ty of
1934 Just r -> r
1935 Nothing -> pprPanic "getRuntimeRep" (ppr ty <+> dcolon <+> ppr (typeKind ty))
1936
1937 -- | Extract the RuntimeRep classifier of a type from its kind. For example,
1938 -- @getRuntimeRepFromKind * = LiftedRep@; Panics if this is not possible.
1939 getRuntimeRepFromKind :: HasDebugCallStack
1940 => Type -> Type
1941 getRuntimeRepFromKind k =
1942 case getRuntimeRepFromKind_maybe k of
1943 Just r -> r
1944 Nothing -> pprPanic "getRuntimeRepFromKind"
1945 (ppr k <+> dcolon <+> ppr (typeKind k))
1946
1947 -- | Extract the RuntimeRep classifier of a type from its kind. For example,
1948 -- @getRuntimeRepFromKind * = LiftedRep@; Returns 'Nothing' if this is not
1949 -- possible.
1950 getRuntimeRepFromKind_maybe :: HasDebugCallStack
1951 => Type -> Maybe Type
1952 getRuntimeRepFromKind_maybe = go
1953 where
1954 go k | Just k' <- coreView k = go k'
1955 go k
1956 | Just (_tc, [arg]) <- splitTyConApp_maybe k
1957 = ASSERT2( _tc `hasKey` tYPETyConKey, ppr k )
1958 Just arg
1959 go _ = Nothing
1960
1961 isUnboxedTupleType :: Type -> Bool
1962 isUnboxedTupleType ty
1963 = tyConAppTyCon (getRuntimeRep ty) `hasKey` tupleRepDataConKey
1964 -- NB: Do not use typePrimRep, as that can't tell the difference between
1965 -- unboxed tuples and unboxed sums
1966
1967
1968 isUnboxedSumType :: Type -> Bool
1969 isUnboxedSumType ty
1970 = tyConAppTyCon (getRuntimeRep ty) `hasKey` sumRepDataConKey
1971
1972 -- | See "Type#type_classification" for what an algebraic type is.
1973 -- Should only be applied to /types/, as opposed to e.g. partially
1974 -- saturated type constructors
1975 isAlgType :: Type -> Bool
1976 isAlgType ty
1977 = case splitTyConApp_maybe ty of
1978 Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc )
1979 isAlgTyCon tc
1980 _other -> False
1981
1982 -- | Check whether a type is a data family type
1983 isDataFamilyAppType :: Type -> Bool
1984 isDataFamilyAppType ty = case tyConAppTyCon_maybe ty of
1985 Just tc -> isDataFamilyTyCon tc
1986 _ -> False
1987
1988 -- | Computes whether an argument (or let right hand side) should
1989 -- be computed strictly or lazily, based only on its type.
1990 -- Currently, it's just 'isUnliftedType'. Panics on levity-polymorphic types.
1991 isStrictType :: HasDebugCallStack => Type -> Bool
1992 isStrictType = isUnliftedType
1993
1994 isPrimitiveType :: Type -> Bool
1995 -- ^ Returns true of types that are opaque to Haskell.
1996 isPrimitiveType ty = case splitTyConApp_maybe ty of
1997 Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc )
1998 isPrimTyCon tc
1999 _ -> False
2000
2001 {-
2002 ************************************************************************
2003 * *
2004 \subsection{Join points}
2005 * *
2006 ************************************************************************
2007 -}
2008
2009 -- | Determine whether a type could be the type of a join point of given total
2010 -- arity, according to the polymorphism rule. A join point cannot be polymorphic
2011 -- in its return type, since given
2012 -- join j @a @b x y z = e1 in e2,
2013 -- the types of e1 and e2 must be the same, and a and b are not in scope for e2.
2014 -- (See Note [The polymorphism rule of join points] in CoreSyn.) Returns False
2015 -- also if the type simply doesn't have enough arguments.
2016 --
2017 -- Note that we need to know how many arguments (type *and* value) the putative
2018 -- join point takes; for instance, if
2019 -- j :: forall a. a -> Int
2020 -- then j could be a binary join point returning an Int, but it could *not* be a
2021 -- unary join point returning a -> Int.
2022 --
2023 -- TODO: See Note [Excess polymorphism and join points]
2024 isValidJoinPointType :: JoinArity -> Type -> Bool
2025 isValidJoinPointType arity ty
2026 = valid_under emptyVarSet arity ty
2027 where
2028 valid_under tvs arity ty
2029 | arity == 0
2030 = isEmptyVarSet (tvs `intersectVarSet` tyCoVarsOfType ty)
2031 | Just (t, ty') <- splitForAllTy_maybe ty
2032 = valid_under (tvs `extendVarSet` t) (arity-1) ty'
2033 | Just (_, res_ty) <- splitFunTy_maybe ty
2034 = valid_under tvs (arity-1) res_ty
2035 | otherwise
2036 = False
2037
2038 {- Note [Excess polymorphism and join points]
2039 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2040 In principle, if a function would be a join point except that it fails
2041 the polymorphism rule (see Note [The polymorphism rule of join points] in
2042 CoreSyn), it can still be made a join point with some effort. This is because
2043 all tail calls must return the same type (they return to the same context!), and
2044 thus if the return type depends on an argument, that argument must always be the
2045 same.
2046
2047 For instance, consider:
2048
2049 let f :: forall a. a -> Char -> [a]
2050 f @a x c = ... f @a y 'a' ...
2051 in ... f @Int 1 'b' ... f @Int 2 'c' ...
2052
2053 (where the calls are tail calls). `f` fails the polymorphism rule because its
2054 return type is [a], where [a] is bound. But since the type argument is always
2055 'Int', we can rewrite it as:
2056
2057 let f' :: Int -> Char -> [Int]
2058 f' x c = ... f' y 'a' ...
2059 in ... f' 1 'b' ... f 2 'c' ...
2060
2061 and now we can make f' a join point:
2062
2063 join f' :: Int -> Char -> [Int]
2064 f' x c = ... jump f' y 'a' ...
2065 in ... jump f' 1 'b' ... jump f' 2 'c' ...
2066
2067 It's not clear that this comes up often, however. TODO: Measure how often and
2068 add this analysis if necessary. See Trac #14620.
2069
2070
2071 ************************************************************************
2072 * *
2073 \subsection{Sequencing on types}
2074 * *
2075 ************************************************************************
2076 -}
2077
2078 seqType :: Type -> ()
2079 seqType (LitTy n) = n `seq` ()
2080 seqType (TyVarTy tv) = tv `seq` ()
2081 seqType (AppTy t1 t2) = seqType t1 `seq` seqType t2
2082 seqType (FunTy t1 t2) = seqType t1 `seq` seqType t2
2083 seqType (TyConApp tc tys) = tc `seq` seqTypes tys
2084 seqType (ForAllTy (TvBndr tv _) ty) = seqType (tyVarKind tv) `seq` seqType ty
2085 seqType (CastTy ty co) = seqType ty `seq` seqCo co
2086 seqType (CoercionTy co) = seqCo co
2087
2088 seqTypes :: [Type] -> ()
2089 seqTypes [] = ()
2090 seqTypes (ty:tys) = seqType ty `seq` seqTypes tys
2091
2092 {-
2093 ************************************************************************
2094 * *
2095 Comparison for types
2096 (We don't use instances so that we know where it happens)
2097 * *
2098 ************************************************************************
2099
2100 Note [Equality on AppTys]
2101 ~~~~~~~~~~~~~~~~~~~~~~~~~
2102 In our cast-ignoring equality, we want to say that the following two
2103 are equal:
2104
2105 (Maybe |> co) (Int |> co') ~? Maybe Int
2106
2107 But the left is an AppTy while the right is a TyConApp. The solution is
2108 to use repSplitAppTy_maybe to break up the TyConApp into its pieces and
2109 then continue. Easy to do, but also easy to forget to do.
2110
2111 -}
2112
2113 eqType :: Type -> Type -> Bool
2114 -- ^ Type equality on source types. Does not look through @newtypes@ or
2115 -- 'PredType's, but it does look through type synonyms.
2116 -- This first checks that the kinds of the types are equal and then
2117 -- checks whether the types are equal, ignoring casts and coercions.
2118 -- (The kind check is a recursive call, but since all kinds have type
2119 -- @Type@, there is no need to check the types of kinds.)
2120 -- See also Note [Non-trivial definitional equality] in TyCoRep.
2121 eqType t1 t2 = isEqual $ nonDetCmpType t1 t2
2122 -- It's OK to use nonDetCmpType here and eqType is deterministic,
2123 -- nonDetCmpType does equality deterministically
2124
2125 -- | Compare types with respect to a (presumably) non-empty 'RnEnv2'.
2126 eqTypeX :: RnEnv2 -> Type -> Type -> Bool
2127 eqTypeX env t1 t2 = isEqual $ nonDetCmpTypeX env t1 t2
2128 -- It's OK to use nonDetCmpType here and eqTypeX is deterministic,
2129 -- nonDetCmpTypeX does equality deterministically
2130
2131 -- | Type equality on lists of types, looking through type synonyms
2132 -- but not newtypes.
2133 eqTypes :: [Type] -> [Type] -> Bool
2134 eqTypes tys1 tys2 = isEqual $ nonDetCmpTypes tys1 tys2
2135 -- It's OK to use nonDetCmpType here and eqTypes is deterministic,
2136 -- nonDetCmpTypes does equality deterministically
2137
2138 eqVarBndrs :: RnEnv2 -> [Var] -> [Var] -> Maybe RnEnv2
2139 -- Check that the var lists are the same length
2140 -- and have matching kinds; if so, extend the RnEnv2
2141 -- Returns Nothing if they don't match
2142 eqVarBndrs env [] []
2143 = Just env
2144 eqVarBndrs env (tv1:tvs1) (tv2:tvs2)
2145 | eqTypeX env (tyVarKind tv1) (tyVarKind tv2)
2146 = eqVarBndrs (rnBndr2 env tv1 tv2) tvs1 tvs2
2147 eqVarBndrs _ _ _= Nothing
2148
2149 -- Now here comes the real worker
2150
2151 {-
2152 Note [nonDetCmpType nondeterminism]
2153 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2154 nonDetCmpType is implemented in terms of nonDetCmpTypeX. nonDetCmpTypeX
2155 uses nonDetCmpTc which compares TyCons by their Unique value. Using Uniques for
2156 ordering leads to nondeterminism. We hit the same problem in the TyVarTy case,
2157 comparing type variables is nondeterministic, note the call to nonDetCmpVar in
2158 nonDetCmpTypeX.
2159 See Note [Unique Determinism] for more details.
2160 -}
2161
2162 nonDetCmpType :: Type -> Type -> Ordering
2163 nonDetCmpType t1 t2
2164 -- we know k1 and k2 have the same kind, because they both have kind *.
2165 = nonDetCmpTypeX rn_env t1 t2
2166 where
2167 rn_env = mkRnEnv2 (mkInScopeSet (tyCoVarsOfTypes [t1, t2]))
2168
2169 nonDetCmpTypes :: [Type] -> [Type] -> Ordering
2170 nonDetCmpTypes ts1 ts2 = nonDetCmpTypesX rn_env ts1 ts2
2171 where
2172 rn_env = mkRnEnv2 (mkInScopeSet (tyCoVarsOfTypes (ts1 ++ ts2)))
2173
2174 -- | An ordering relation between two 'Type's (known below as @t1 :: k1@
2175 -- and @t2 :: k2@)
2176 data TypeOrdering = TLT -- ^ @t1 < t2@
2177 | TEQ -- ^ @t1 ~ t2@ and there are no casts in either,
2178 -- therefore we can conclude @k1 ~ k2@
2179 | TEQX -- ^ @t1 ~ t2@ yet one of the types contains a cast so
2180 -- they may differ in kind.
2181 | TGT -- ^ @t1 > t2@
2182 deriving (Eq, Ord, Enum, Bounded)
2183
2184 nonDetCmpTypeX :: RnEnv2 -> Type -> Type -> Ordering -- Main workhorse
2185 -- See Note [Non-trivial definitional equality] in TyCoRep
2186 nonDetCmpTypeX env orig_t1 orig_t2 =
2187 case go env orig_t1 orig_t2 of
2188 -- If there are casts then we also need to do a comparison of the kinds of
2189 -- the types being compared
2190 TEQX -> toOrdering $ go env k1 k2
2191 ty_ordering -> toOrdering ty_ordering
2192 where
2193 k1 = typeKind orig_t1
2194 k2 = typeKind orig_t2
2195
2196 toOrdering :: TypeOrdering -> Ordering
2197 toOrdering TLT = LT
2198 toOrdering TEQ = EQ
2199 toOrdering TEQX = EQ
2200 toOrdering TGT = GT
2201
2202 liftOrdering :: Ordering -> TypeOrdering
2203 liftOrdering LT = TLT
2204 liftOrdering EQ = TEQ
2205 liftOrdering GT = TGT
2206
2207 thenCmpTy :: TypeOrdering -> TypeOrdering -> TypeOrdering
2208 thenCmpTy TEQ rel = rel
2209 thenCmpTy TEQX rel = hasCast rel
2210 thenCmpTy rel _ = rel
2211
2212 hasCast :: TypeOrdering -> TypeOrdering
2213 hasCast TEQ = TEQX
2214 hasCast rel = rel
2215
2216 -- Returns both the resulting ordering relation between the two types
2217 -- and whether either contains a cast.
2218 go :: RnEnv2 -> Type -> Type -> TypeOrdering
2219 go env t1 t2
2220 | Just t1' <- coreView t1 = go env t1' t2
2221 | Just t2' <- coreView t2 = go env t1 t2'
2222
2223 go env (TyVarTy tv1) (TyVarTy tv2)
2224 = liftOrdering $ rnOccL env tv1 `nonDetCmpVar` rnOccR env tv2
2225 go env (ForAllTy (TvBndr tv1 _) t1) (ForAllTy (TvBndr tv2 _) t2)
2226 = go env (tyVarKind tv1) (tyVarKind tv2)
2227 `thenCmpTy` go (rnBndr2 env tv1 tv2) t1 t2
2228 -- See Note [Equality on AppTys]
2229 go env (AppTy s1 t1) ty2
2230 | Just (s2, t2) <- repSplitAppTy_maybe ty2
2231 = go env s1 s2 `thenCmpTy` go env t1 t2
2232 go env ty1 (AppTy s2 t2)
2233 | Just (s1, t1) <- repSplitAppTy_maybe ty1
2234 = go env s1 s2 `thenCmpTy` go env t1 t2
2235 go env (FunTy s1 t1) (FunTy s2 t2)
2236 = go env s1 s2 `thenCmpTy` go env t1 t2
2237 go env (TyConApp tc1 tys1) (TyConApp tc2 tys2)
2238 = liftOrdering (tc1 `nonDetCmpTc` tc2) `thenCmpTy` gos env tys1 tys2
2239 go _ (LitTy l1) (LitTy l2) = liftOrdering (compare l1 l2)
2240 go env (CastTy t1 _) t2 = hasCast $ go env t1 t2
2241 go env t1 (CastTy t2 _) = hasCast $ go env t1 t2
2242
2243 go _ (CoercionTy {}) (CoercionTy {}) = TEQ
2244
2245 -- Deal with the rest: TyVarTy < CoercionTy < AppTy < LitTy < TyConApp < ForAllTy
2246 go _ ty1 ty2
2247 = liftOrdering $ (get_rank ty1) `compare` (get_rank ty2)
2248 where get_rank :: Type -> Int
2249 get_rank (CastTy {})
2250 = pprPanic "nonDetCmpTypeX.get_rank" (ppr [ty1,ty2])
2251 get_rank (TyVarTy {}) = 0
2252 get_rank (CoercionTy {}) = 1
2253 get_rank (AppTy {}) = 3
2254 get_rank (LitTy {}) = 4
2255 get_rank (TyConApp {}) = 5
2256 get_rank (FunTy {}) = 6
2257 get_rank (ForAllTy {}) = 7
2258
2259 gos :: RnEnv2 -> [Type] -> [Type] -> TypeOrdering
2260 gos _ [] [] = TEQ
2261 gos _ [] _ = TLT
2262 gos _ _ [] = TGT
2263 gos env (ty1:tys1) (ty2:tys2) = go env ty1 ty2 `thenCmpTy` gos env tys1 tys2
2264
2265 -------------
2266 nonDetCmpTypesX :: RnEnv2 -> [Type] -> [Type] -> Ordering
2267 nonDetCmpTypesX _ [] [] = EQ
2268 nonDetCmpTypesX env (t1:tys1) (t2:tys2) = nonDetCmpTypeX env t1 t2
2269 `thenCmp` nonDetCmpTypesX env tys1 tys2
2270 nonDetCmpTypesX _ [] _ = LT
2271 nonDetCmpTypesX _ _ [] = GT
2272
2273 -------------
2274 -- | Compare two 'TyCon's. NB: This should /never/ see the "star synonyms",
2275 -- as recognized by Kind.isStarKindSynonymTyCon. See Note
2276 -- [Kind Constraint and kind *] in Kind.
2277 -- See Note [nonDetCmpType nondeterminism]
2278 nonDetCmpTc :: TyCon -> TyCon -> Ordering
2279 nonDetCmpTc tc1 tc2
2280 = ASSERT( not (isStarKindSynonymTyCon tc1) && not (isStarKindSynonymTyCon tc2) )
2281 u1 `nonDetCmpUnique` u2
2282 where
2283 u1 = tyConUnique tc1
2284 u2 = tyConUnique tc2
2285
2286 {-
2287 ************************************************************************
2288 * *
2289 The kind of a type
2290 * *
2291 ************************************************************************
2292 -}
2293
2294 typeKind :: HasDebugCallStack => Type -> Kind
2295 typeKind (TyConApp tc tys) = piResultTys (tyConKind tc) tys
2296 typeKind (AppTy fun arg) = piResultTy (typeKind fun) arg
2297 typeKind (LitTy l) = typeLiteralKind l
2298 typeKind (FunTy {}) = liftedTypeKind
2299 typeKind (ForAllTy _ ty) = typeKind ty
2300 typeKind (TyVarTy tyvar) = tyVarKind tyvar
2301 typeKind (CastTy _ty co) = pSnd $ coercionKind co
2302 typeKind (CoercionTy co) = coercionType co
2303
2304 typeLiteralKind :: TyLit -> Kind
2305 typeLiteralKind l =
2306 case l of
2307 NumTyLit _ -> typeNatKind
2308 StrTyLit _ -> typeSymbolKind
2309
2310 -- | Returns True if a type is levity polymorphic. Should be the same
2311 -- as (isKindLevPoly . typeKind) but much faster.
2312 -- Precondition: The type has kind (TYPE blah)
2313 isTypeLevPoly :: Type -> Bool
2314 isTypeLevPoly = go
2315 where
2316 go ty@(TyVarTy {}) = check_kind ty
2317 go ty@(AppTy {}) = check_kind ty
2318 go ty@(TyConApp tc _) | not (isTcLevPoly tc) = False
2319 | otherwise = check_kind ty
2320 go (ForAllTy _ ty) = go ty
2321 go (FunTy {}) = False
2322 go (LitTy {}) = False
2323 go ty@(CastTy {}) = check_kind ty
2324 go ty@(CoercionTy {}) = pprPanic "isTypeLevPoly co" (ppr ty)
2325
2326 check_kind = isKindLevPoly . typeKind
2327
2328 -- | Looking past all pi-types, is the end result potentially levity polymorphic?
2329 -- Example: True for (forall r (a :: TYPE r). String -> a)
2330 -- Example: False for (forall r1 r2 (a :: TYPE r1) (b :: TYPE r2). a -> b -> Type)
2331 resultIsLevPoly :: Type -> Bool
2332 resultIsLevPoly = isTypeLevPoly . snd . splitPiTys
2333
2334 {-
2335 %************************************************************************
2336 %* *
2337 Miscellaneous functions
2338 %* *
2339 %************************************************************************
2340
2341 -}
2342 -- | All type constructors occurring in the type; looking through type
2343 -- synonyms, but not newtypes.
2344 -- When it finds a Class, it returns the class TyCon.
2345 tyConsOfType :: Type -> UniqSet TyCon
2346 tyConsOfType ty
2347 = go ty
2348 where
2349 go :: Type -> UniqSet TyCon -- The UniqSet does duplicate elim
2350 go ty | Just ty' <- coreView ty = go ty'
2351 go (TyVarTy {}) = emptyUniqSet
2352 go (LitTy {}) = emptyUniqSet
2353 go (TyConApp tc tys) = go_tc tc `unionUniqSets` go_s tys
2354 go (AppTy a b) = go a `unionUniqSets` go b
2355 go (FunTy a b) = go a `unionUniqSets` go b `unionUniqSets` go_tc funTyCon
2356 go (ForAllTy (TvBndr tv _) ty) = go ty `unionUniqSets` go (tyVarKind tv)
2357 go (CastTy ty co) = go ty `unionUniqSets` go_co co
2358 go (CoercionTy co) = go_co co
2359
2360 go_co (Refl _ ty) = go ty
2361 go_co (TyConAppCo _ tc args) = go_tc tc `unionUniqSets` go_cos args
2362 go_co (AppCo co arg) = go_co co `unionUniqSets` go_co arg
2363 go_co (ForAllCo _ kind_co co) = go_co kind_co `unionUniqSets` go_co co
2364 go_co (FunCo _ co1 co2) = go_co co1 `unionUniqSets` go_co co2
2365 go_co (AxiomInstCo ax _ args) = go_ax ax `unionUniqSets` go_cos args
2366 go_co (UnivCo p _ t1 t2) = go_prov p `unionUniqSets` go t1 `unionUniqSets` go t2
2367 go_co (CoVarCo {}) = emptyUniqSet
2368 go_co (HoleCo {}) = emptyUniqSet
2369 go_co (SymCo co) = go_co co
2370 go_co (TransCo co1 co2) = go_co co1 `unionUniqSets` go_co co2
2371 go_co (NthCo _ co) = go_co co
2372 go_co (LRCo _ co) = go_co co
2373 go_co (InstCo co arg) = go_co co `unionUniqSets` go_co arg
2374 go_co (CoherenceCo co1 co2) = go_co co1 `unionUniqSets` go_co co2
2375 go_co (KindCo co) = go_co co
2376 go_co (SubCo co) = go_co co
2377 go_co (AxiomRuleCo _ cs) = go_cos cs
2378
2379 go_prov UnsafeCoerceProv = emptyUniqSet
2380 go_prov (PhantomProv co) = go_co co
2381 go_prov (ProofIrrelProv co) = go_co co
2382 go_prov (PluginProv _) = emptyUniqSet
2383 -- this last case can happen from the tyConsOfType used from
2384 -- checkTauTvUpdate
2385
2386 go_s tys = foldr (unionUniqSets . go) emptyUniqSet tys
2387 go_cos cos = foldr (unionUniqSets . go_co) emptyUniqSet cos
2388
2389 go_tc tc = unitUniqSet tc
2390 go_ax ax = go_tc $ coAxiomTyCon ax
2391
2392 -- | Find the result 'Kind' of a type synonym,
2393 -- after applying it to its 'arity' number of type variables
2394 -- Actually this function works fine on data types too,
2395 -- but they'd always return '*', so we never need to ask
2396 synTyConResKind :: TyCon -> Kind
2397 synTyConResKind tycon = piResultTys (tyConKind tycon) (mkTyVarTys (tyConTyVars tycon))
2398
2399 -- | Retrieve the free variables in this type, splitting them based
2400 -- on whether they are used visibly or invisibly. Invisible ones come
2401 -- first.
2402 splitVisVarsOfType :: Type -> Pair TyCoVarSet
2403 splitVisVarsOfType orig_ty = Pair invis_vars vis_vars
2404 where
2405 Pair invis_vars1 vis_vars = go orig_ty
2406 invis_vars = invis_vars1 `minusVarSet` vis_vars
2407
2408 go (TyVarTy tv) = Pair (tyCoVarsOfType $ tyVarKind tv) (unitVarSet tv)
2409 go (AppTy t1 t2) = go t1 `mappend` go t2
2410 go (TyConApp tc tys) = go_tc tc tys
2411 go (FunTy t1 t2) = go t1 `mappend` go t2
2412 go (ForAllTy (TvBndr tv _) ty)
2413 = ((`delVarSet` tv) <$> go ty) `mappend`
2414 (invisible (tyCoVarsOfType $ tyVarKind tv))
2415 go (LitTy {}) = mempty
2416 go (CastTy ty co) = go ty `mappend` invisible (tyCoVarsOfCo co)
2417 go (CoercionTy co) = invisible $ tyCoVarsOfCo co
2418
2419 invisible vs = Pair vs emptyVarSet
2420
2421 go_tc tc tys = let (invis, vis) = partitionInvisibles tc id tys in
2422 invisible (tyCoVarsOfTypes invis) `mappend` foldMap go vis
2423
2424 splitVisVarsOfTypes :: [Type] -> Pair TyCoVarSet
2425 splitVisVarsOfTypes = foldMap splitVisVarsOfType
2426
2427 modifyJoinResTy :: Int -- Number of binders to skip
2428 -> (Type -> Type) -- Function to apply to result type
2429 -> Type -- Type of join point
2430 -> Type -- New type
2431 -- INVARIANT: If any of the first n binders are foralls, those tyvars cannot
2432 -- appear in the original result type. See isValidJoinPointType.
2433 modifyJoinResTy orig_ar f orig_ty
2434 = go orig_ar orig_ty
2435 where
2436 go 0 ty = f ty
2437 go n ty | Just (arg_bndr, res_ty) <- splitPiTy_maybe ty
2438 = mkPiTy arg_bndr (go (n-1) res_ty)
2439 | otherwise
2440 = pprPanic "modifyJoinResTy" (ppr orig_ar <+> ppr orig_ty)
2441
2442 setJoinResTy :: Int -- Number of binders to skip
2443 -> Type -- New result type
2444 -> Type -- Type of join point
2445 -> Type -- New type
2446 -- INVARIANT: Same as for modifyJoinResTy
2447 setJoinResTy ar new_res_ty ty
2448 = modifyJoinResTy ar (const new_res_ty) ty