Add HasDebugStack for typeKind
[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, nextRole,
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 filterOutInvisibleTyVars, 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,
96 binderRelevantType_maybe, caseBinder,
97 isVisibleArgFlag, isInvisibleArgFlag, isVisibleBinder, isInvisibleBinder,
98 tyConBindersTyBinders,
99 mkTyBinderTyConBinder,
100
101 -- ** Common type constructors
102 funTyCon,
103
104 -- ** Predicates on types
105 isTyVarTy, isFunTy, isDictTy, isPredTy, isCoercionTy,
106 isCoercionTy_maybe, isCoercionType, isForAllTy,
107 isPiTy, isTauTy, isFamFreeTy,
108
109 isValidJoinPointType,
110
111 -- (Lifting and boxity)
112 isLiftedType_maybe, isUnliftedType, isUnboxedTupleType, isUnboxedSumType,
113 isAlgType, isDataFamilyAppType,
114 isPrimitiveType, isStrictType,
115 isRuntimeRepTy, isRuntimeRepVar, isRuntimeRepKindedTy,
116 dropRuntimeRepArgs,
117 getRuntimeRep, getRuntimeRepFromKind,
118
119 -- * Main data types representing Kinds
120 Kind,
121
122 -- ** Finding the kind of a type
123 typeKind, isTypeLevPoly, resultIsLevPoly,
124
125 -- ** Common Kind
126 liftedTypeKind,
127
128 -- * Type free variables
129 tyCoFVsOfType, tyCoFVsBndr,
130 tyCoVarsOfType, tyCoVarsOfTypes,
131 tyCoVarsOfTypeDSet,
132 coVarsOfType,
133 coVarsOfTypes, closeOverKinds, closeOverKindsList,
134 noFreeVarsOfType,
135 splitVisVarsOfType, splitVisVarsOfTypes,
136 expandTypeSynonyms,
137 typeSize,
138
139 -- * Well-scoped lists of variables
140 dVarSetElemsWellScoped, toposortTyVars, tyCoVarsOfTypeWellScoped,
141 tyCoVarsOfTypesWellScoped,
142
143 -- * Type comparison
144 eqType, eqTypeX, eqTypes, nonDetCmpType, nonDetCmpTypes, nonDetCmpTypeX,
145 nonDetCmpTypesX, nonDetCmpTc,
146 eqVarBndrs,
147
148 -- * Forcing evaluation of types
149 seqType, seqTypes,
150
151 -- * Other views onto Types
152 coreView, tcView,
153
154 tyConsOfType,
155
156 -- * Main type substitution data types
157 TvSubstEnv, -- Representation widely visible
158 TCvSubst(..), -- Representation visible to a few friends
159
160 -- ** Manipulating type substitutions
161 emptyTvSubstEnv, emptyTCvSubst, mkEmptyTCvSubst,
162
163 mkTCvSubst, zipTvSubst, mkTvSubstPrs,
164 notElemTCvSubst,
165 getTvSubstEnv, setTvSubstEnv,
166 zapTCvSubst, getTCvInScope, getTCvSubstRangeFVs,
167 extendTCvInScope, extendTCvInScopeList, extendTCvInScopeSet,
168 extendTCvSubst, extendCvSubst,
169 extendTvSubst, extendTvSubstBinderAndInScope,
170 extendTvSubstList, extendTvSubstAndInScope,
171 extendTvSubstWithClone,
172 isInScope, composeTCvSubstEnv, composeTCvSubst, zipTyEnv, zipCoEnv,
173 isEmptyTCvSubst, unionTCvSubst,
174
175 -- ** Performing substitution on types and kinds
176 substTy, substTys, substTyWith, substTysWith, substTheta,
177 substTyAddInScope,
178 substTyUnchecked, substTysUnchecked, substThetaUnchecked,
179 substTyWithUnchecked,
180 substCoUnchecked, substCoWithUnchecked,
181 substTyVarBndr, substTyVar, substTyVars,
182 cloneTyVarBndr, cloneTyVarBndrs, lookupTyVar,
183
184 -- * Pretty-printing
185 pprType, pprParendType, pprPrecType,
186 pprTypeApp, pprTyThingCategory, pprShortTyThing,
187 pprTvBndr, pprTvBndrs, pprForAll, pprUserForAll,
188 pprSigmaType, ppSuggestExplicitKinds,
189 pprTheta, pprThetaArrowTy, pprClassPred,
190 pprKind, pprParendKind, pprSourceTyCon,
191 TyPrec(..), maybeParen,
192 pprTyVar, pprTyVars, pprPrefixApp, pprArrowChain,
193
194 -- * Tidying type related things up for printing
195 tidyType, tidyTypes,
196 tidyOpenType, tidyOpenTypes,
197 tidyOpenKind,
198 tidyTyCoVarBndr, tidyTyCoVarBndrs, tidyFreeTyCoVars,
199 tidyOpenTyCoVar, tidyOpenTyCoVars,
200 tidyTyVarOcc,
201 tidyTopType,
202 tidyKind,
203 tidyTyVarBinder, tidyTyVarBinders
204 ) where
205
206 #include "HsVersions.h"
207
208 import BasicTypes
209
210 -- We import the representation and primitive functions from TyCoRep.
211 -- Many things are reexported, but not the representation!
212
213 import Kind
214 import TyCoRep
215
216 -- friends:
217 import Var
218 import VarEnv
219 import VarSet
220 import UniqSet
221
222 import Class
223 import TyCon
224 import TysPrim
225 import {-# SOURCE #-} TysWiredIn ( listTyCon, typeNatKind
226 , typeSymbolKind, liftedTypeKind )
227 import PrelNames
228 import CoAxiom
229 import {-# SOURCE #-} Coercion
230
231 -- others
232 import Util
233 import Outputable
234 import FastString
235 import Pair
236 import ListSetOps
237 import Digraph
238 import Unique ( nonDetCmpUnique )
239 import SrcLoc ( SrcSpan )
240 import OccName ( OccName )
241 import Name ( mkInternalName )
242
243 import Maybes ( orElse )
244 import Data.Maybe ( isJust, mapMaybe )
245 import Control.Monad ( guard )
246 import Control.Arrow ( first, second )
247
248 -- $type_classification
249 -- #type_classification#
250 --
251 -- Types are one of:
252 --
253 -- [Unboxed] Iff its representation is other than a pointer
254 -- Unboxed types are also unlifted.
255 --
256 -- [Lifted] Iff it has bottom as an element.
257 -- Closures always have lifted types: i.e. any
258 -- let-bound identifier in Core must have a lifted
259 -- type. Operationally, a lifted object is one that
260 -- can be entered.
261 -- Only lifted types may be unified with a type variable.
262 --
263 -- [Algebraic] Iff it is a type with one or more constructors, whether
264 -- declared with @data@ or @newtype@.
265 -- An algebraic type is one that can be deconstructed
266 -- with a case expression. This is /not/ the same as
267 -- lifted types, because we also include unboxed
268 -- tuples in this classification.
269 --
270 -- [Data] Iff it is a type declared with @data@, or a boxed tuple.
271 --
272 -- [Primitive] Iff it is a built-in type that can't be expressed in Haskell.
273 --
274 -- Currently, all primitive types are unlifted, but that's not necessarily
275 -- the case: for example, @Int@ could be primitive.
276 --
277 -- Some primitive types are unboxed, such as @Int#@, whereas some are boxed
278 -- but unlifted (such as @ByteArray#@). The only primitive types that we
279 -- classify as algebraic are the unboxed tuples.
280 --
281 -- Some examples of type classifications that may make this a bit clearer are:
282 --
283 -- @
284 -- Type primitive boxed lifted algebraic
285 -- -----------------------------------------------------------------------------
286 -- Int# Yes No No No
287 -- ByteArray# Yes Yes No No
288 -- (\# a, b \#) Yes No No Yes
289 -- (\# a | b \#) Yes No No Yes
290 -- ( a, b ) No Yes Yes Yes
291 -- [a] No Yes Yes Yes
292 -- @
293
294 -- $representation_types
295 -- A /source type/ is a type that is a separate type as far as the type checker is
296 -- concerned, but which has a more low-level representation as far as Core-to-Core
297 -- passes and the rest of the back end is concerned.
298 --
299 -- You don't normally have to worry about this, as the utility functions in
300 -- this module will automatically convert a source into a representation type
301 -- if they are spotted, to the best of it's abilities. If you don't want this
302 -- to happen, use the equivalent functions from the "TcType" module.
303
304 {-
305 ************************************************************************
306 * *
307 Type representation
308 * *
309 ************************************************************************
310
311 Note [coreView vs tcView]
312 ~~~~~~~~~~~~~~~~~~~~~~~~~
313 So far as the typechecker is concerned, 'Constraint' and 'TYPE LiftedRep' are distinct kinds.
314
315 But in Core these two are treated as identical.
316
317 We implement this by making 'coreView' convert 'Constraint' to 'TYPE LiftedRep' on the fly.
318 The function tcView (used in the type checker) does not do this.
319
320 See also Trac #11715, which tracks removing this inconsistency.
321
322 -}
323
324 {-# INLINE coreView #-}
325 coreView :: Type -> Maybe Type
326 -- ^ This function Strips off the /top layer only/ of a type synonym
327 -- application (if any) its underlying representation type.
328 -- Returns Nothing if there is nothing to look through.
329 -- This function considers 'Constraint' to be a synonym of @TYPE LiftedRep@.
330 --
331 -- By being non-recursive and inlined, this case analysis gets efficiently
332 -- joined onto the case analysis that the caller is already doing
333 coreView (TyConApp tc tys) | Just (tenv, rhs, tys') <- expandSynTyCon_maybe tc tys
334 = Just (mkAppTys (substTy (mkTvSubstPrs tenv) rhs) tys')
335 -- The free vars of 'rhs' should all be bound by 'tenv', so it's
336 -- ok to use 'substTy' here.
337 -- See also Note [The substitution invariant] in TyCoRep.
338 -- Its important to use mkAppTys, rather than (foldl AppTy),
339 -- because the function part might well return a
340 -- partially-applied type constructor; indeed, usually will!
341 coreView (TyConApp tc [])
342 | isStarKindSynonymTyCon tc
343 = Just liftedTypeKind
344
345 coreView _ = Nothing
346
347 -- | Gives the typechecker view of a type. This unwraps synonyms but
348 -- leaves 'Constraint' alone. c.f. coreView, which turns Constraint into
349 -- TYPE LiftedRep. Returns Nothing if no unwrapping happens.
350 -- See also Note [coreView vs tcView] in Type.
351 {-# INLINE tcView #-}
352 tcView :: Type -> Maybe Type
353 tcView (TyConApp tc tys) | Just (tenv, rhs, tys') <- expandSynTyCon_maybe tc tys
354 = Just (mkAppTys (substTy (mkTvSubstPrs tenv) rhs) tys')
355 -- The free vars of 'rhs' should all be bound by 'tenv', so it's
356 -- ok to use 'substTy' here.
357 -- See also Note [The substitution invariant] in TyCoRep.
358 -- Its important to use mkAppTys, rather than (foldl AppTy),
359 -- because the function part might well return a
360 -- partially-applied type constructor; indeed, usually will!
361 tcView _ = Nothing
362
363 -----------------------------------------------
364 expandTypeSynonyms :: Type -> Type
365 -- ^ Expand out all type synonyms. Actually, it'd suffice to expand out
366 -- just the ones that discard type variables (e.g. type Funny a = Int)
367 -- But we don't know which those are currently, so we just expand all.
368 --
369 -- 'expandTypeSynonyms' only expands out type synonyms mentioned in the type,
370 -- not in the kinds of any TyCon or TyVar mentioned in the type.
371 --
372 -- Keep this synchronized with 'synonymTyConsOfType'
373 expandTypeSynonyms ty
374 = go (mkEmptyTCvSubst in_scope) ty
375 where
376 in_scope = mkInScopeSet (tyCoVarsOfType ty)
377
378 go subst (TyConApp tc tys)
379 | Just (tenv, rhs, tys') <- expandSynTyCon_maybe tc expanded_tys
380 = let subst' = mkTvSubst in_scope (mkVarEnv tenv)
381 -- Make a fresh substitution; rhs has nothing to
382 -- do with anything that has happened so far
383 -- NB: if you make changes here, be sure to build an
384 -- /idempotent/ substitution, even in the nested case
385 -- type T a b = a -> b
386 -- type S x y = T y x
387 -- (Trac #11665)
388 in mkAppTys (go subst' rhs) tys'
389 | otherwise
390 = TyConApp tc expanded_tys
391 where
392 expanded_tys = (map (go subst) tys)
393
394 go _ (LitTy l) = LitTy l
395 go subst (TyVarTy tv) = substTyVar subst tv
396 go subst (AppTy t1 t2) = mkAppTy (go subst t1) (go subst t2)
397 go subst (FunTy arg res)
398 = mkFunTy (go subst arg) (go subst res)
399 go subst (ForAllTy (TvBndr tv vis) t)
400 = let (subst', tv') = substTyVarBndrCallback go subst tv in
401 ForAllTy (TvBndr tv' vis) (go subst' t)
402 go subst (CastTy ty co) = mkCastTy (go subst ty) (go_co subst co)
403 go subst (CoercionTy co) = mkCoercionTy (go_co subst co)
404
405 go_co subst (Refl r ty)
406 = mkReflCo r (go subst ty)
407 -- NB: coercions are always expanded upon creation
408 go_co subst (TyConAppCo r tc args)
409 = mkTyConAppCo r tc (map (go_co subst) args)
410 go_co subst (AppCo co arg)
411 = mkAppCo (go_co subst co) (go_co subst arg)
412 go_co subst (ForAllCo tv kind_co co)
413 = let (subst', tv', kind_co') = go_cobndr subst tv kind_co in
414 mkForAllCo tv' kind_co' (go_co subst' co)
415 go_co subst (FunCo r co1 co2)
416 = mkFunCo r (go_co subst co1) (go_co subst co2)
417 go_co subst (CoVarCo cv)
418 = substCoVar subst cv
419 go_co subst (AxiomInstCo ax ind args)
420 = mkAxiomInstCo ax ind (map (go_co subst) args)
421 go_co subst (UnivCo p r t1 t2)
422 = mkUnivCo (go_prov subst p) r (go subst t1) (go subst t2)
423 go_co subst (SymCo co)
424 = mkSymCo (go_co subst co)
425 go_co subst (TransCo co1 co2)
426 = mkTransCo (go_co subst co1) (go_co subst co2)
427 go_co subst (NthCo n co)
428 = mkNthCo n (go_co subst co)
429 go_co subst (LRCo lr co)
430 = mkLRCo lr (go_co subst co)
431 go_co subst (InstCo co arg)
432 = mkInstCo (go_co subst co) (go_co subst arg)
433 go_co subst (CoherenceCo co1 co2)
434 = mkCoherenceCo (go_co subst co1) (go_co subst co2)
435 go_co subst (KindCo co)
436 = mkKindCo (go_co subst co)
437 go_co subst (SubCo co)
438 = mkSubCo (go_co subst co)
439 go_co subst (AxiomRuleCo ax cs) = AxiomRuleCo ax (map (go_co subst) cs)
440
441 go_prov _ UnsafeCoerceProv = UnsafeCoerceProv
442 go_prov subst (PhantomProv co) = PhantomProv (go_co subst co)
443 go_prov subst (ProofIrrelProv co) = ProofIrrelProv (go_co subst co)
444 go_prov _ p@(PluginProv _) = p
445 go_prov _ (HoleProv h) = pprPanic "expandTypeSynonyms hit a hole" (ppr h)
446
447 -- the "False" and "const" are to accommodate the type of
448 -- substForAllCoBndrCallback, which is general enough to
449 -- handle coercion optimization (which sometimes swaps the
450 -- order of a coercion)
451 go_cobndr subst = substForAllCoBndrCallback False (go_co subst) subst
452
453 {-
454 ************************************************************************
455 * *
456 Analyzing types
457 * *
458 ************************************************************************
459
460 These functions do a map-like operation over types, performing some operation
461 on all variables and binding sites. Primarily used for zonking.
462
463 Note [Efficiency for mapCoercion ForAllCo case]
464 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
465 As noted in Note [Forall coercions] in TyCoRep, a ForAllCo is a bit redundant.
466 It stores a TyVar and a Coercion, where the kind of the TyVar always matches
467 the left-hand kind of the coercion. This is convenient lots of the time, but
468 not when mapping a function over a coercion.
469
470 The problem is that tcm_tybinder will affect the TyVar's kind and
471 mapCoercion will affect the Coercion, and we hope that the results will be
472 the same. Even if they are the same (which should generally happen with
473 correct algorithms), then there is an efficiency issue. In particular,
474 this problem seems to make what should be a linear algorithm into a potentially
475 exponential one. But it's only going to be bad in the case where there's
476 lots of foralls in the kinds of other foralls. Like this:
477
478 forall a : (forall b : (forall c : ...). ...). ...
479
480 This construction seems unlikely. So we'll do the inefficient, easy way
481 for now.
482
483 Note [Specialising mappers]
484 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
485 These INLINABLE pragmas are indispensable. mapType/mapCoercion are used
486 to implement zonking, and it's vital that they get specialised to the TcM
487 monad. This specialisation happens automatically (that is, without a
488 SPECIALISE pragma) as long as the definitions are INLINABLE. For example,
489 this one change made a 20% allocation difference in perf/compiler/T5030.
490
491 -}
492
493 -- | This describes how a "map" operation over a type/coercion should behave
494 data TyCoMapper env m
495 = TyCoMapper
496 { tcm_smart :: Bool -- ^ Should the new type be created with smart
497 -- constructors?
498 , tcm_tyvar :: env -> TyVar -> m Type
499 , tcm_covar :: env -> CoVar -> m Coercion
500 , tcm_hole :: env -> CoercionHole -> Role
501 -> Type -> Type -> m Coercion
502 -- ^ What to do with coercion holes. See Note [Coercion holes] in
503 -- 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 (UnivCo (HoleProv hole) r t1 t2)
557 = cohole env hole r t1 t2
558 go (UnivCo p r t1 t2)
559 = mkunivco <$> go_prov p <*> pure r
560 <*> mapType mapper env t1 <*> mapType mapper env t2
561 go (SymCo co) = mksymco <$> go co
562 go (TransCo c1 c2) = mktransco <$> go c1 <*> go c2
563 go (AxiomRuleCo r cos) = AxiomRuleCo r <$> mapM go cos
564 go (NthCo i co) = mknthco i <$> go co
565 go (LRCo lr co) = mklrco lr <$> go co
566 go (InstCo co arg) = mkinstco <$> go co <*> go arg
567 go (CoherenceCo c1 c2) = mkcoherenceco <$> go c1 <*> go c2
568 go (KindCo co) = mkkindco <$> go co
569 go (SubCo co) = mksubco <$> go co
570
571 go_prov UnsafeCoerceProv = return UnsafeCoerceProv
572 go_prov (PhantomProv co) = PhantomProv <$> go co
573 go_prov (ProofIrrelProv co) = ProofIrrelProv <$> go co
574 go_prov p@(PluginProv _) = return p
575 go_prov (HoleProv _) = panic "mapCoercion"
576
577 ( mktyconappco, mkappco, mkaxiominstco, mkunivco
578 , mksymco, mktransco, mknthco, mklrco, mkinstco, mkcoherenceco
579 , mkkindco, mksubco, mkforallco)
580 | smart
581 = ( mkTyConAppCo, mkAppCo, mkAxiomInstCo, mkUnivCo
582 , mkSymCo, mkTransCo, mkNthCo, mkLRCo, mkInstCo, mkCoherenceCo
583 , mkKindCo, mkSubCo, mkForAllCo )
584 | otherwise
585 = ( TyConAppCo, AppCo, AxiomInstCo, UnivCo
586 , SymCo, TransCo, NthCo, LRCo, InstCo, CoherenceCo
587 , KindCo, SubCo, ForAllCo )
588
589 {-
590 ************************************************************************
591 * *
592 \subsection{Constructor-specific functions}
593 * *
594 ************************************************************************
595
596
597 ---------------------------------------------------------------------
598 TyVarTy
599 ~~~~~~~
600 -}
601
602 -- | Attempts to obtain the type variable underlying a 'Type', and panics with the
603 -- given message if this is not a type variable type. See also 'getTyVar_maybe'
604 getTyVar :: String -> Type -> TyVar
605 getTyVar msg ty = case getTyVar_maybe ty of
606 Just tv -> tv
607 Nothing -> panic ("getTyVar: " ++ msg)
608
609 isTyVarTy :: Type -> Bool
610 isTyVarTy ty = isJust (getTyVar_maybe ty)
611
612 -- | Attempts to obtain the type variable underlying a 'Type'
613 getTyVar_maybe :: Type -> Maybe TyVar
614 getTyVar_maybe ty | Just ty' <- coreView ty = getTyVar_maybe ty'
615 | otherwise = repGetTyVar_maybe ty
616
617 -- | If the type is a tyvar, possibly under a cast, returns it, along
618 -- with the coercion. Thus, the co is :: kind tv ~N kind type
619 getCastedTyVar_maybe :: Type -> Maybe (TyVar, CoercionN)
620 getCastedTyVar_maybe ty | Just ty' <- coreView ty = getCastedTyVar_maybe ty'
621 getCastedTyVar_maybe (CastTy (TyVarTy tv) co) = Just (tv, co)
622 getCastedTyVar_maybe (TyVarTy tv)
623 = Just (tv, mkReflCo Nominal (tyVarKind tv))
624 getCastedTyVar_maybe _ = Nothing
625
626 -- | Attempts to obtain the type variable underlying a 'Type', without
627 -- any expansion
628 repGetTyVar_maybe :: Type -> Maybe TyVar
629 repGetTyVar_maybe (TyVarTy tv) = Just tv
630 repGetTyVar_maybe _ = Nothing
631
632 {-
633 ---------------------------------------------------------------------
634 AppTy
635 ~~~~~
636 We need to be pretty careful with AppTy to make sure we obey the
637 invariant that a TyConApp is always visibly so. mkAppTy maintains the
638 invariant: use it.
639
640 Note [Decomposing fat arrow c=>t]
641 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
642 Can we unify (a b) with (Eq a => ty)? If we do so, we end up with
643 a partial application like ((=>) Eq a) which doesn't make sense in
644 source Haskell. In contrast, we *can* unify (a b) with (t1 -> t2).
645 Here's an example (Trac #9858) of how you might do it:
646 i :: (Typeable a, Typeable b) => Proxy (a b) -> TypeRep
647 i p = typeRep p
648
649 j = i (Proxy :: Proxy (Eq Int => Int))
650 The type (Proxy (Eq Int => Int)) is only accepted with -XImpredicativeTypes,
651 but suppose we want that. But then in the call to 'i', we end
652 up decomposing (Eq Int => Int), and we definitely don't want that.
653
654 This really only applies to the type checker; in Core, '=>' and '->'
655 are the same, as are 'Constraint' and '*'. But for now I've put
656 the test in repSplitAppTy_maybe, which applies throughout, because
657 the other calls to splitAppTy are in Unify, which is also used by
658 the type checker (e.g. when matching type-function equations).
659
660 -}
661
662 -- | Applies a type to another, as in e.g. @k a@
663 mkAppTy :: Type -> Type -> Type
664 mkAppTy (TyConApp tc tys) ty2 = mkTyConApp tc (tys ++ [ty2])
665 mkAppTy ty1 ty2 = AppTy ty1 ty2
666 -- Note that the TyConApp could be an
667 -- under-saturated type synonym. GHC allows that; e.g.
668 -- type Foo k = k a -> k a
669 -- type Id x = x
670 -- foo :: Foo Id -> Foo Id
671 --
672 -- Here Id is partially applied in the type sig for Foo,
673 -- but once the type synonyms are expanded all is well
674
675 mkAppTys :: Type -> [Type] -> Type
676 mkAppTys ty1 [] = ty1
677 mkAppTys (TyConApp tc tys1) tys2 = mkTyConApp tc (tys1 ++ tys2)
678 mkAppTys ty1 tys2 = foldl AppTy ty1 tys2
679
680 -------------
681 splitAppTy_maybe :: Type -> Maybe (Type, Type)
682 -- ^ Attempt to take a type application apart, whether it is a
683 -- function, type constructor, or plain type application. Note
684 -- that type family applications are NEVER unsaturated by this!
685 splitAppTy_maybe ty | Just ty' <- coreView ty
686 = splitAppTy_maybe ty'
687 splitAppTy_maybe ty = repSplitAppTy_maybe ty
688
689 -------------
690 repSplitAppTy_maybe :: Type -> Maybe (Type,Type)
691 -- ^ Does the AppTy split as in 'splitAppTy_maybe', but assumes that
692 -- any Core view stuff is already done
693 repSplitAppTy_maybe (FunTy ty1 ty2)
694 = Just (TyConApp funTyCon [rep1, rep2, ty1], ty2)
695 where
696 rep1 = getRuntimeRep ty1
697 rep2 = getRuntimeRep ty2
698
699 repSplitAppTy_maybe (AppTy ty1 ty2)
700 = Just (ty1, ty2)
701
702 repSplitAppTy_maybe (TyConApp tc tys)
703 | mightBeUnsaturatedTyCon tc || tys `lengthExceeds` tyConArity tc
704 , Just (tys', ty') <- snocView tys
705 = Just (TyConApp tc tys', ty') -- Never create unsaturated type family apps!
706
707 repSplitAppTy_maybe _other = Nothing
708
709 -- this one doesn't braek apart (c => t).
710 -- See Note [Decomposing fat arrow c=>t]
711 -- Defined here to avoid module loops between Unify and TcType.
712 tcRepSplitAppTy_maybe :: Type -> Maybe (Type,Type)
713 -- ^ Does the AppTy split as in 'tcSplitAppTy_maybe', but assumes that
714 -- any coreView stuff is already done. Refuses to look through (c => t)
715 tcRepSplitAppTy_maybe (FunTy ty1 ty2)
716 | isConstraintKind (typeKind ty1)
717 = Nothing -- See Note [Decomposing fat arrow c=>t]
718
719 | otherwise
720 = Just (TyConApp funTyCon [rep1, rep2, ty1], ty2)
721 where
722 rep1 = getRuntimeRep ty1
723 rep2 = getRuntimeRep ty2
724
725 tcRepSplitAppTy_maybe (AppTy ty1 ty2) = Just (ty1, ty2)
726 tcRepSplitAppTy_maybe (TyConApp tc tys)
727 | mightBeUnsaturatedTyCon tc || tys `lengthExceeds` tyConArity tc
728 , Just (tys', ty') <- snocView tys
729 = Just (TyConApp tc tys', ty') -- Never create unsaturated type family apps!
730 tcRepSplitAppTy_maybe _other = Nothing
731
732 -- | Split a type constructor application into its type constructor and
733 -- applied types. Note that this may fail in the case of a 'FunTy' with an
734 -- argument of unknown kind 'FunTy' (e.g. @FunTy (a :: k) Int@. since the kind
735 -- of @a@ isn't of the form @TYPE rep@). Consequently, you may need to zonk your
736 -- type before using this function.
737 --
738 -- If you only need the 'TyCon', consider using 'tcTyConAppTyCon_maybe'.
739 tcSplitTyConApp_maybe :: HasCallStack => Type -> Maybe (TyCon, [Type])
740 -- Defined here to avoid module loops between Unify and TcType.
741 tcSplitTyConApp_maybe ty | Just ty' <- tcView ty = tcSplitTyConApp_maybe ty'
742 tcSplitTyConApp_maybe ty = tcRepSplitTyConApp_maybe ty
743
744 -- | Like 'tcSplitTyConApp_maybe' but doesn't look through type synonyms.
745 tcRepSplitTyConApp_maybe :: HasCallStack => Type -> Maybe (TyCon, [Type])
746 -- Defined here to avoid module loops between Unify and TcType.
747 tcRepSplitTyConApp_maybe (TyConApp tc tys)
748 = Just (tc, tys)
749
750 tcRepSplitTyConApp_maybe (FunTy arg res)
751 = Just (funTyCon, [arg_rep, res_rep, arg, res])
752 where
753 arg_rep = getRuntimeRep arg
754 res_rep = getRuntimeRep res
755
756 tcRepSplitTyConApp_maybe _
757 = Nothing
758
759 -------------
760 splitAppTy :: Type -> (Type, Type)
761 -- ^ Attempts to take a type application apart, as in 'splitAppTy_maybe',
762 -- and panics if this is not possible
763 splitAppTy ty = case splitAppTy_maybe ty of
764 Just pr -> pr
765 Nothing -> panic "splitAppTy"
766
767 -------------
768 splitAppTys :: Type -> (Type, [Type])
769 -- ^ Recursively splits a type as far as is possible, leaving a residual
770 -- type being applied to and the type arguments applied to it. Never fails,
771 -- even if that means returning an empty list of type applications.
772 splitAppTys ty = split ty ty []
773 where
774 split orig_ty ty args | Just ty' <- coreView ty = split orig_ty ty' args
775 split _ (AppTy ty arg) args = split ty ty (arg:args)
776 split _ (TyConApp tc tc_args) args
777 = let -- keep type families saturated
778 n | mightBeUnsaturatedTyCon tc = 0
779 | otherwise = tyConArity tc
780 (tc_args1, tc_args2) = splitAt n tc_args
781 in
782 (TyConApp tc tc_args1, tc_args2 ++ args)
783 split _ (FunTy ty1 ty2) args
784 = ASSERT( null args )
785 (TyConApp funTyCon [], [rep1, rep2, ty1, ty2])
786 where
787 rep1 = getRuntimeRep ty1
788 rep2 = getRuntimeRep ty2
789
790 split orig_ty _ args = (orig_ty, args)
791
792 -- | Like 'splitAppTys', but doesn't look through type synonyms
793 repSplitAppTys :: HasDebugCallStack => Type -> (Type, [Type])
794 repSplitAppTys ty = split ty []
795 where
796 split (AppTy ty arg) args = split ty (arg:args)
797 split (TyConApp tc tc_args) args
798 = let n | mightBeUnsaturatedTyCon tc = 0
799 | otherwise = tyConArity tc
800 (tc_args1, tc_args2) = splitAt n tc_args
801 in
802 (TyConApp tc tc_args1, tc_args2 ++ args)
803 split (FunTy ty1 ty2) args
804 = ASSERT( null args )
805 (TyConApp funTyCon [], [rep1, rep2, ty1, ty2])
806 where
807 rep1 = getRuntimeRep ty1
808 rep2 = getRuntimeRep ty2
809
810 split ty args = (ty, args)
811
812 {-
813 LitTy
814 ~~~~~
815 -}
816
817 mkNumLitTy :: Integer -> Type
818 mkNumLitTy n = LitTy (NumTyLit n)
819
820 -- | Is this a numeric literal. We also look through type synonyms.
821 isNumLitTy :: Type -> Maybe Integer
822 isNumLitTy ty | Just ty1 <- coreView ty = isNumLitTy ty1
823 isNumLitTy (LitTy (NumTyLit n)) = Just n
824 isNumLitTy _ = Nothing
825
826 mkStrLitTy :: FastString -> Type
827 mkStrLitTy s = LitTy (StrTyLit s)
828
829 -- | Is this a symbol literal. We also look through type synonyms.
830 isStrLitTy :: Type -> Maybe FastString
831 isStrLitTy ty | Just ty1 <- coreView ty = isStrLitTy ty1
832 isStrLitTy (LitTy (StrTyLit s)) = Just s
833 isStrLitTy _ = Nothing
834
835
836 -- | Is this type a custom user error?
837 -- If so, give us the kind and the error message.
838 userTypeError_maybe :: Type -> Maybe Type
839 userTypeError_maybe t
840 = do { (tc, _kind : msg : _) <- splitTyConApp_maybe t
841 -- There may be more than 2 arguments, if the type error is
842 -- used as a type constructor (e.g. at kind `Type -> Type`).
843
844 ; guard (tyConName tc == errorMessageTypeErrorFamName)
845 ; return msg }
846
847 -- | Render a type corresponding to a user type error into a SDoc.
848 pprUserTypeErrorTy :: Type -> SDoc
849 pprUserTypeErrorTy ty =
850 case splitTyConApp_maybe ty of
851
852 -- Text "Something"
853 Just (tc,[txt])
854 | tyConName tc == typeErrorTextDataConName
855 , Just str <- isStrLitTy txt -> ftext str
856
857 -- ShowType t
858 Just (tc,[_k,t])
859 | tyConName tc == typeErrorShowTypeDataConName -> ppr t
860
861 -- t1 :<>: t2
862 Just (tc,[t1,t2])
863 | tyConName tc == typeErrorAppendDataConName ->
864 pprUserTypeErrorTy t1 <> pprUserTypeErrorTy t2
865
866 -- t1 :$$: t2
867 Just (tc,[t1,t2])
868 | tyConName tc == typeErrorVAppendDataConName ->
869 pprUserTypeErrorTy t1 $$ pprUserTypeErrorTy t2
870
871 -- An uneavaluated type function
872 _ -> ppr ty
873
874
875
876
877 {-
878 ---------------------------------------------------------------------
879 FunTy
880 ~~~~~
881
882 Note [Representation of function types]
883 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
884
885 Functions (e.g. Int -> Char) are can be thought of as being applications
886 of funTyCon (known in Haskell surface syntax as (->)),
887
888 (->) :: forall (r1 :: RuntimeRep) (r2 :: RuntimeRep)
889 (a :: TYPE r1) (b :: TYPE r2).
890 a -> b -> Type
891
892 However, for efficiency's sake we represent saturated applications of (->)
893 with FunTy. For instance, the type,
894
895 (->) r1 r2 a b
896
897 is equivalent to,
898
899 FunTy (Anon a) b
900
901 Note how the RuntimeReps are implied in the FunTy representation. For this
902 reason we must be careful when recontructing the TyConApp representation (see,
903 for instance, splitTyConApp_maybe).
904
905 In the compiler we maintain the invariant that all saturated applications of
906 (->) are represented with FunTy.
907
908 See #11714.
909 -}
910
911 isFunTy :: Type -> Bool
912 isFunTy ty = isJust (splitFunTy_maybe ty)
913
914 splitFunTy :: Type -> (Type, Type)
915 -- ^ Attempts to extract the argument and result types from a type, and
916 -- panics if that is not possible. See also 'splitFunTy_maybe'
917 splitFunTy ty | Just ty' <- coreView ty = splitFunTy ty'
918 splitFunTy (FunTy arg res) = (arg, res)
919 splitFunTy other = pprPanic "splitFunTy" (ppr other)
920
921 splitFunTy_maybe :: Type -> Maybe (Type, Type)
922 -- ^ Attempts to extract the argument and result types from a type
923 splitFunTy_maybe ty | Just ty' <- coreView ty = splitFunTy_maybe ty'
924 splitFunTy_maybe (FunTy arg res) = Just (arg, res)
925 splitFunTy_maybe _ = Nothing
926
927 splitFunTys :: Type -> ([Type], Type)
928 splitFunTys ty = split [] ty ty
929 where
930 split args orig_ty ty | Just ty' <- coreView ty = split args orig_ty ty'
931 split args _ (FunTy arg res) = split (arg:args) res res
932 split args orig_ty _ = (reverse args, orig_ty)
933
934 funResultTy :: Type -> Type
935 -- ^ Extract the function result type and panic if that is not possible
936 funResultTy ty | Just ty' <- coreView ty = funResultTy ty'
937 funResultTy (FunTy _ res) = res
938 funResultTy ty = pprPanic "funResultTy" (ppr ty)
939
940 funArgTy :: Type -> Type
941 -- ^ Extract the function argument type and panic if that is not possible
942 funArgTy ty | Just ty' <- coreView ty = funArgTy ty'
943 funArgTy (FunTy arg _res) = arg
944 funArgTy ty = pprPanic "funArgTy" (ppr ty)
945
946 piResultTy :: HasDebugCallStack => Type -> Type -> Type
947 piResultTy ty arg = case piResultTy_maybe ty arg of
948 Just res -> res
949 Nothing -> pprPanic "piResultTy" (ppr ty $$ ppr arg)
950
951 piResultTy_maybe :: Type -> Type -> Maybe Type
952
953 -- ^ Just like 'piResultTys' but for a single argument
954 -- Try not to iterate 'piResultTy', because it's inefficient to substitute
955 -- one variable at a time; instead use 'piResultTys"
956 piResultTy_maybe ty arg
957 | Just ty' <- coreView ty = piResultTy_maybe ty' arg
958
959 | FunTy _ res <- ty
960 = Just res
961
962 | ForAllTy (TvBndr tv _) res <- ty
963 = let empty_subst = mkEmptyTCvSubst $ mkInScopeSet $
964 tyCoVarsOfTypes [arg,res]
965 in Just (substTy (extendTvSubst empty_subst tv arg) res)
966
967 | otherwise
968 = Nothing
969
970 -- | (piResultTys f_ty [ty1, .., tyn]) gives the type of (f ty1 .. tyn)
971 -- where f :: f_ty
972 -- 'piResultTys' is interesting because:
973 -- 1. 'f_ty' may have more for-alls than there are args
974 -- 2. Less obviously, it may have fewer for-alls
975 -- For case 2. think of:
976 -- piResultTys (forall a.a) [forall b.b, Int]
977 -- This really can happen, but only (I think) in situations involving
978 -- undefined. For example:
979 -- undefined :: forall a. a
980 -- Term: undefined @(forall b. b->b) @Int
981 -- This term should have type (Int -> Int), but notice that
982 -- there are more type args than foralls in 'undefined's type.
983
984 -- If you edit this function, you may need to update the GHC formalism
985 -- See Note [GHC Formalism] in coreSyn/CoreLint.hs
986
987 -- This is a heavily used function (e.g. from typeKind),
988 -- so we pay attention to efficiency, especially in the special case
989 -- where there are no for-alls so we are just dropping arrows from
990 -- a function type/kind.
991 piResultTys :: HasDebugCallStack => Type -> [Type] -> Type
992 piResultTys ty [] = ty
993 piResultTys ty orig_args@(arg:args)
994 | Just ty' <- coreView ty
995 = piResultTys ty' orig_args
996
997 | FunTy _ res <- ty
998 = piResultTys res args
999
1000 | ForAllTy (TvBndr tv _) res <- ty
1001 = go (extendVarEnv emptyTvSubstEnv tv arg) res args
1002
1003 | otherwise
1004 = pprPanic "piResultTys1" (ppr ty $$ ppr orig_args)
1005 where
1006 in_scope = mkInScopeSet (tyCoVarsOfTypes (ty:orig_args))
1007
1008 go :: TvSubstEnv -> Type -> [Type] -> Type
1009 go tv_env ty [] = substTy (mkTvSubst in_scope tv_env) ty
1010
1011 go tv_env ty all_args@(arg:args)
1012 | Just ty' <- coreView ty
1013 = go tv_env ty' all_args
1014
1015 | FunTy _ res <- ty
1016 = go tv_env res args
1017
1018 | ForAllTy (TvBndr tv _) res <- ty
1019 = go (extendVarEnv tv_env tv arg) res args
1020
1021 | TyVarTy tv <- ty
1022 , Just ty' <- lookupVarEnv tv_env tv
1023 -- Deals with piResultTys (forall a. a) [forall b.b, Int]
1024 = piResultTys ty' all_args
1025
1026 | otherwise
1027 = pprPanic "piResultTys2" (ppr ty $$ ppr orig_args $$ ppr all_args)
1028
1029 applyTysX :: [TyVar] -> Type -> [Type] -> Type
1030 -- applyTyxX beta-reduces (/\tvs. body_ty) arg_tys
1031 -- Assumes that (/\tvs. body_ty) is closed
1032 applyTysX tvs body_ty arg_tys
1033 = ASSERT2( arg_tys `lengthAtLeast` n_tvs, pp_stuff )
1034 ASSERT2( tyCoVarsOfType body_ty `subVarSet` mkVarSet tvs, pp_stuff )
1035 mkAppTys (substTyWith tvs (take n_tvs arg_tys) body_ty)
1036 (drop n_tvs arg_tys)
1037 where
1038 pp_stuff = vcat [ppr tvs, ppr body_ty, ppr arg_tys]
1039 n_tvs = length tvs
1040
1041 {-
1042 ---------------------------------------------------------------------
1043 TyConApp
1044 ~~~~~~~~
1045 -}
1046
1047 -- | A key function: builds a 'TyConApp' or 'FunTy' as appropriate to
1048 -- its arguments. Applies its arguments to the constructor from left to right.
1049 mkTyConApp :: TyCon -> [Type] -> Type
1050 mkTyConApp tycon tys
1051 | isFunTyCon tycon
1052 , [_rep1,_rep2,ty1,ty2] <- tys
1053 = FunTy ty1 ty2
1054
1055 | otherwise
1056 = TyConApp tycon tys
1057
1058 -- splitTyConApp "looks through" synonyms, because they don't
1059 -- mean a distinct type, but all other type-constructor applications
1060 -- including functions are returned as Just ..
1061
1062 -- | Retrieve the tycon heading this type, if there is one. Does /not/
1063 -- look through synonyms.
1064 tyConAppTyConPicky_maybe :: Type -> Maybe TyCon
1065 tyConAppTyConPicky_maybe (TyConApp tc _) = Just tc
1066 tyConAppTyConPicky_maybe (FunTy {}) = Just funTyCon
1067 tyConAppTyConPicky_maybe _ = Nothing
1068
1069
1070 -- | The same as @fst . splitTyConApp@
1071 tyConAppTyCon_maybe :: Type -> Maybe TyCon
1072 tyConAppTyCon_maybe ty | Just ty' <- coreView ty = tyConAppTyCon_maybe ty'
1073 tyConAppTyCon_maybe (TyConApp tc _) = Just tc
1074 tyConAppTyCon_maybe (FunTy {}) = Just funTyCon
1075 tyConAppTyCon_maybe _ = Nothing
1076
1077 tyConAppTyCon :: Type -> TyCon
1078 tyConAppTyCon ty = tyConAppTyCon_maybe ty `orElse` pprPanic "tyConAppTyCon" (ppr ty)
1079
1080 -- | The same as @snd . splitTyConApp@
1081 tyConAppArgs_maybe :: Type -> Maybe [Type]
1082 tyConAppArgs_maybe ty | Just ty' <- coreView ty = tyConAppArgs_maybe ty'
1083 tyConAppArgs_maybe (TyConApp _ tys) = Just tys
1084 tyConAppArgs_maybe (FunTy arg res)
1085 | Just rep1 <- getRuntimeRep_maybe arg
1086 , Just rep2 <- getRuntimeRep_maybe res
1087 = Just [rep1, rep2, arg, res]
1088 tyConAppArgs_maybe _ = Nothing
1089
1090 tyConAppArgs :: Type -> [Type]
1091 tyConAppArgs ty = tyConAppArgs_maybe ty `orElse` pprPanic "tyConAppArgs" (ppr ty)
1092
1093 tyConAppArgN :: Int -> Type -> Type
1094 -- Executing Nth
1095 tyConAppArgN n ty
1096 = case tyConAppArgs_maybe ty of
1097 Just tys -> ASSERT2( tys `lengthExceeds` n, ppr n <+> ppr tys ) tys `getNth` n
1098 Nothing -> pprPanic "tyConAppArgN" (ppr n <+> ppr ty)
1099
1100 -- | Attempts to tease a type apart into a type constructor and the application
1101 -- of a number of arguments to that constructor. Panics if that is not possible.
1102 -- See also 'splitTyConApp_maybe'
1103 splitTyConApp :: Type -> (TyCon, [Type])
1104 splitTyConApp ty = case splitTyConApp_maybe ty of
1105 Just stuff -> stuff
1106 Nothing -> pprPanic "splitTyConApp" (ppr ty)
1107
1108 -- | Attempts to tease a type apart into a type constructor and the application
1109 -- of a number of arguments to that constructor
1110 splitTyConApp_maybe :: HasDebugCallStack => Type -> Maybe (TyCon, [Type])
1111 splitTyConApp_maybe ty | Just ty' <- coreView ty = splitTyConApp_maybe ty'
1112 splitTyConApp_maybe ty = repSplitTyConApp_maybe ty
1113
1114 -- | Like 'splitTyConApp_maybe', but doesn't look through synonyms. This
1115 -- assumes the synonyms have already been dealt with.
1116 repSplitTyConApp_maybe :: HasDebugCallStack => Type -> Maybe (TyCon, [Type])
1117 repSplitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
1118 repSplitTyConApp_maybe (FunTy arg res)
1119 | Just arg_rep <- getRuntimeRep_maybe arg
1120 , Just res_rep <- getRuntimeRep_maybe res
1121 = Just (funTyCon, [arg_rep, res_rep, arg, res])
1122 repSplitTyConApp_maybe _ = Nothing
1123
1124 -- | Attempts to tease a list type apart and gives the type of the elements if
1125 -- successful (looks through type synonyms)
1126 splitListTyConApp_maybe :: Type -> Maybe Type
1127 splitListTyConApp_maybe ty = case splitTyConApp_maybe ty of
1128 Just (tc,[e]) | tc == listTyCon -> Just e
1129 _other -> Nothing
1130
1131 -- | What is the role assigned to the next parameter of this type? Usually,
1132 -- this will be 'Nominal', but if the type is a 'TyConApp', we may be able to
1133 -- do better. The type does *not* have to be well-kinded when applied for this
1134 -- to work!
1135 nextRole :: Type -> Role
1136 nextRole ty
1137 | Just (tc, tys) <- splitTyConApp_maybe ty
1138 , let num_tys = length tys
1139 , num_tys < tyConArity tc
1140 = tyConRoles tc `getNth` num_tys
1141
1142 | otherwise
1143 = Nominal
1144
1145 newTyConInstRhs :: TyCon -> [Type] -> Type
1146 -- ^ Unwrap one 'layer' of newtype on a type constructor and its
1147 -- arguments, using an eta-reduced version of the @newtype@ if possible.
1148 -- This requires tys to have at least @newTyConInstArity tycon@ elements.
1149 newTyConInstRhs tycon tys
1150 = ASSERT2( tvs `leLength` tys, ppr tycon $$ ppr tys $$ ppr tvs )
1151 applyTysX tvs rhs tys
1152 where
1153 (tvs, rhs) = newTyConEtadRhs tycon
1154
1155 {-
1156 ---------------------------------------------------------------------
1157 CastTy
1158 ~~~~~~
1159 A casted type has its *kind* casted into something new.
1160
1161 Note [No reflexive casts in types]
1162 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1163 As far as possible, we would like to maintain the following property:
1164
1165 (*) If (t1 `eqType` t2), then t1 and t2 are treated identically within GHC.
1166
1167 The (*) property is very useful, because we have a tendency to compare two
1168 types to see if they're equal, and then arbitrarily choose one. We don't
1169 want this arbitrary choice to then matter later on. Maintaining (*) means
1170 that every function that looks at a structure of a type must think about
1171 casts. In places where we directly pattern-match, this consideration is
1172 forced by consideration of the CastTy constructor.
1173
1174 But, when we call a splitXXX function, it's easy to ignore the possibility
1175 of casts. In particular, splitTyConApp is used extensively, and we don't
1176 want it to fail on (T a b c |> co). Happily, if we have
1177 (T a b c |> co) `eqType` (T d e f)
1178 then co must be reflexive. Why? eqType checks that the kinds are equal, as
1179 well as checking that (a `eqType` d), (b `eqType` e), and (c `eqType` f).
1180 By the kind check, we know that (T a b c |> co) and (T d e f) have the same
1181 kind. So the only way that co could be non-reflexive is for (T a b c) to have
1182 a different kind than (T d e f). But because T's kind is closed (all tycon kinds
1183 are closed), the only way for this to happen is that one of the arguments has
1184 to differ, leading to a contradiction. Thus, co is reflexive.
1185
1186 Accordingly, by eliminating reflexive casts, splitTyConApp need not worry
1187 about outermost casts to uphold (*).
1188
1189 Unforunately, that's not the end of the story. Consider comparing
1190 (T a b c) =? (T a b |> (co -> <Type>)) (c |> sym co)
1191 These two types have the same kind (Type), but the left type is a TyConApp
1192 while the right type is not. To handle this case, we will have to implement
1193 some variant of the dreaded KPush algorithm (c.f. CoreOpt.pushCoDataCon).
1194 This stone is left unturned for now, meaning that we don't yet uphold (*).
1195
1196 The other place where (*) will be hard to guarantee is in splitAppTy, because
1197 I (Richard E) can't think of a way to push coercions into AppTys. The good
1198 news here is that splitAppTy is not used all that much, and so all clients of
1199 that function can simply be told to use splitCastTy as well, in order to
1200 uphold (*). This, too, is left undone, for now.
1201
1202 -}
1203
1204 splitCastTy_maybe :: Type -> Maybe (Type, Coercion)
1205 splitCastTy_maybe ty | Just ty' <- coreView ty = splitCastTy_maybe ty'
1206 splitCastTy_maybe (CastTy ty co) = Just (ty, co)
1207 splitCastTy_maybe _ = Nothing
1208
1209 -- | Make a 'CastTy'. The Coercion must be nominal. Checks the
1210 -- Coercion for reflexivity, dropping it if it's reflexive.
1211 -- See Note [No reflexive casts in types]
1212 mkCastTy :: Type -> Coercion -> Type
1213 mkCastTy ty co | isReflexiveCo co = ty
1214 -- NB: Do the slow check here. This is important to keep the splitXXX
1215 -- functions working properly. Otherwise, we may end up with something
1216 -- like (((->) |> something_reflexive_but_not_obviously_so) biz baz)
1217 -- fails under splitFunTy_maybe. This happened with the cheaper check
1218 -- in test dependent/should_compile/dynamic-paper.
1219
1220 mkCastTy (CastTy ty co1) co2 = mkCastTy ty (co1 `mkTransCo` co2)
1221 mkCastTy ty co = CastTy ty co
1222
1223 tyConBindersTyBinders :: [TyConBinder] -> [TyBinder]
1224 -- Return the tyConBinders in TyBinder form
1225 tyConBindersTyBinders = map to_tyb
1226 where
1227 to_tyb (TvBndr tv (NamedTCB vis)) = Named (TvBndr tv vis)
1228 to_tyb (TvBndr tv AnonTCB) = Anon (tyVarKind tv)
1229
1230 {-
1231 --------------------------------------------------------------------
1232 CoercionTy
1233 ~~~~~~~~~~
1234 CoercionTy allows us to inject coercions into types. A CoercionTy
1235 should appear only in the right-hand side of an application.
1236 -}
1237
1238 mkCoercionTy :: Coercion -> Type
1239 mkCoercionTy = CoercionTy
1240
1241 isCoercionTy :: Type -> Bool
1242 isCoercionTy (CoercionTy _) = True
1243 isCoercionTy _ = False
1244
1245 isCoercionTy_maybe :: Type -> Maybe Coercion
1246 isCoercionTy_maybe (CoercionTy co) = Just co
1247 isCoercionTy_maybe _ = Nothing
1248
1249 stripCoercionTy :: Type -> Coercion
1250 stripCoercionTy (CoercionTy co) = co
1251 stripCoercionTy ty = pprPanic "stripCoercionTy" (ppr ty)
1252
1253 {-
1254 ---------------------------------------------------------------------
1255 SynTy
1256 ~~~~~
1257
1258 Notes on type synonyms
1259 ~~~~~~~~~~~~~~~~~~~~~~
1260 The various "split" functions (splitFunTy, splitRhoTy, splitForAllTy) try
1261 to return type synonyms wherever possible. Thus
1262
1263 type Foo a = a -> a
1264
1265 we want
1266 splitFunTys (a -> Foo a) = ([a], Foo a)
1267 not ([a], a -> a)
1268
1269 The reason is that we then get better (shorter) type signatures in
1270 interfaces. Notably this plays a role in tcTySigs in TcBinds.hs.
1271
1272
1273 ---------------------------------------------------------------------
1274 ForAllTy
1275 ~~~~~~~~
1276 -}
1277
1278 -- | Make a dependent forall over an Inferred (as opposed to Specified)
1279 -- variable
1280 mkInvForAllTy :: TyVar -> Type -> Type
1281 mkInvForAllTy tv ty = ASSERT( isTyVar tv )
1282 ForAllTy (TvBndr tv Inferred) ty
1283
1284 -- | Like mkForAllTys, but assumes all variables are dependent and Inferred,
1285 -- a common case
1286 mkInvForAllTys :: [TyVar] -> Type -> Type
1287 mkInvForAllTys tvs ty = ASSERT( all isTyVar tvs )
1288 foldr mkInvForAllTy ty tvs
1289
1290 -- | Like mkForAllTys, but assumes all variables are dependent and specified,
1291 -- a common case
1292 mkSpecForAllTys :: [TyVar] -> Type -> Type
1293 mkSpecForAllTys tvs = ASSERT( all isTyVar tvs )
1294 mkForAllTys [ TvBndr tv Specified | tv <- tvs ]
1295
1296 -- | Like mkForAllTys, but assumes all variables are dependent and visible
1297 mkVisForAllTys :: [TyVar] -> Type -> Type
1298 mkVisForAllTys tvs = ASSERT( all isTyVar tvs )
1299 mkForAllTys [ TvBndr tv Required | tv <- tvs ]
1300
1301 mkLamType :: Var -> Type -> Type
1302 -- ^ Makes a @(->)@ type or an implicit forall type, depending
1303 -- on whether it is given a type variable or a term variable.
1304 -- This is used, for example, when producing the type of a lambda.
1305 -- Always uses Inferred binders.
1306 mkLamTypes :: [Var] -> Type -> Type
1307 -- ^ 'mkLamType' for multiple type or value arguments
1308
1309 mkLamType v ty
1310 | isTyVar v = ForAllTy (TvBndr v Inferred) ty
1311 | otherwise = FunTy (varType v) ty
1312
1313 mkLamTypes vs ty = foldr mkLamType ty vs
1314
1315 -- | Given a list of type-level vars and a result kind,
1316 -- makes TyBinders, preferring anonymous binders
1317 -- if the variable is, in fact, not dependent.
1318 -- e.g. mkTyConBindersPreferAnon [(k:*),(b:k),(c:k)] (k->k)
1319 -- We want (k:*) Named, (a;k) Anon, (c:k) Anon
1320 --
1321 -- All binders are /visible/.
1322 mkTyConBindersPreferAnon :: [TyVar] -> Type -> [TyConBinder]
1323 mkTyConBindersPreferAnon vars inner_ty = fst (go vars)
1324 where
1325 go :: [TyVar] -> ([TyConBinder], VarSet) -- also returns the free vars
1326 go [] = ([], tyCoVarsOfType inner_ty)
1327 go (v:vs) | v `elemVarSet` fvs
1328 = ( TvBndr v (NamedTCB Required) : binders
1329 , fvs `delVarSet` v `unionVarSet` kind_vars )
1330 | otherwise
1331 = ( TvBndr v AnonTCB : binders
1332 , fvs `unionVarSet` kind_vars )
1333 where
1334 (binders, fvs) = go vs
1335 kind_vars = tyCoVarsOfType $ tyVarKind v
1336
1337 -- | Take a ForAllTy apart, returning the list of tyvars and the result type.
1338 -- This always succeeds, even if it returns only an empty list. Note that the
1339 -- result type returned may have free variables that were bound by a forall.
1340 splitForAllTys :: Type -> ([TyVar], Type)
1341 splitForAllTys ty = split ty ty []
1342 where
1343 split orig_ty ty tvs | Just ty' <- coreView ty = split orig_ty ty' tvs
1344 split _ (ForAllTy (TvBndr tv _) ty) tvs = split ty ty (tv:tvs)
1345 split orig_ty _ tvs = (reverse tvs, orig_ty)
1346
1347 -- | Like 'splitPiTys' but split off only /named/ binders.
1348 splitForAllTyVarBndrs :: Type -> ([TyVarBinder], Type)
1349 splitForAllTyVarBndrs ty = split ty ty []
1350 where
1351 split orig_ty ty bs | Just ty' <- coreView ty = split orig_ty ty' bs
1352 split _ (ForAllTy b res) bs = split res res (b:bs)
1353 split orig_ty _ bs = (reverse bs, orig_ty)
1354
1355 -- | Checks whether this is a proper forall (with a named binder)
1356 isForAllTy :: Type -> Bool
1357 isForAllTy ty | Just ty' <- coreView ty = isForAllTy ty'
1358 isForAllTy (ForAllTy {}) = True
1359 isForAllTy _ = False
1360
1361 -- | Is this a function or forall?
1362 isPiTy :: Type -> Bool
1363 isPiTy ty | Just ty' <- coreView ty = isForAllTy ty'
1364 isPiTy (ForAllTy {}) = True
1365 isPiTy (FunTy {}) = True
1366 isPiTy _ = False
1367
1368 -- | Take a forall type apart, or panics if that is not possible.
1369 splitForAllTy :: Type -> (TyVar, Type)
1370 splitForAllTy ty
1371 | Just answer <- splitForAllTy_maybe ty = answer
1372 | otherwise = pprPanic "splitForAllTy" (ppr ty)
1373
1374 -- | Drops all ForAllTys
1375 dropForAlls :: Type -> Type
1376 dropForAlls ty = go ty
1377 where
1378 go ty | Just ty' <- coreView ty = go ty'
1379 go (ForAllTy _ res) = go res
1380 go res = res
1381
1382 -- | Attempts to take a forall type apart, but only if it's a proper forall,
1383 -- with a named binder
1384 splitForAllTy_maybe :: Type -> Maybe (TyVar, Type)
1385 splitForAllTy_maybe ty = go ty
1386 where
1387 go ty | Just ty' <- coreView ty = go ty'
1388 go (ForAllTy (TvBndr tv _) ty) = Just (tv, ty)
1389 go _ = Nothing
1390
1391 -- | Attempts to take a forall type apart; works with proper foralls and
1392 -- functions
1393 splitPiTy_maybe :: Type -> Maybe (TyBinder, Type)
1394 splitPiTy_maybe ty = go ty
1395 where
1396 go ty | Just ty' <- coreView ty = go ty'
1397 go (ForAllTy bndr ty) = Just (Named bndr, ty)
1398 go (FunTy arg res) = Just (Anon arg, res)
1399 go _ = Nothing
1400
1401 -- | Takes a forall type apart, or panics
1402 splitPiTy :: Type -> (TyBinder, Type)
1403 splitPiTy ty
1404 | Just answer <- splitPiTy_maybe ty = answer
1405 | otherwise = pprPanic "splitPiTy" (ppr ty)
1406
1407 -- | Split off all TyBinders to a type, splitting both proper foralls
1408 -- and functions
1409 splitPiTys :: Type -> ([TyBinder], Type)
1410 splitPiTys ty = split ty ty []
1411 where
1412 split orig_ty ty bs | Just ty' <- coreView ty = split orig_ty ty' bs
1413 split _ (ForAllTy b res) bs = split res res (Named b : bs)
1414 split _ (FunTy arg res) bs = split res res (Anon arg : bs)
1415 split orig_ty _ bs = (reverse bs, orig_ty)
1416
1417 -- Like splitPiTys, but returns only *invisible* binders, including constraints
1418 -- Stops at the first visible binder
1419 splitPiTysInvisible :: Type -> ([TyBinder], Type)
1420 splitPiTysInvisible ty = split ty ty []
1421 where
1422 split orig_ty ty bs | Just ty' <- coreView ty = split orig_ty ty' bs
1423 split _ (ForAllTy b@(TvBndr _ vis) res) bs
1424 | isInvisibleArgFlag vis = split res res (Named b : bs)
1425 split _ (FunTy arg res) bs
1426 | isPredTy arg = split res res (Anon arg : bs)
1427 split orig_ty _ bs = (reverse bs, orig_ty)
1428
1429 -- | Given a tycon and its arguments, filters out any invisible arguments
1430 filterOutInvisibleTypes :: TyCon -> [Type] -> [Type]
1431 filterOutInvisibleTypes tc tys = snd $ partitionInvisibles tc id tys
1432
1433 -- | Like 'filterOutInvisibles', but works on 'TyVar's
1434 filterOutInvisibleTyVars :: TyCon -> [TyVar] -> [TyVar]
1435 filterOutInvisibleTyVars tc tvs = snd $ partitionInvisibles tc mkTyVarTy tvs
1436
1437 -- | Given a tycon and a list of things (which correspond to arguments),
1438 -- partitions the things into
1439 -- Inferred or Specified ones and
1440 -- Required ones
1441 -- The callback function is necessary for this scenario:
1442 --
1443 -- > T :: forall k. k -> k
1444 -- > partitionInvisibles T [forall m. m -> m -> m, S, R, Q]
1445 --
1446 -- After substituting, we get
1447 --
1448 -- > T (forall m. m -> m -> m) :: (forall m. m -> m -> m) -> forall n. n -> n -> n
1449 --
1450 -- Thus, the first argument is invisible, @S@ is visible, @R@ is invisible again,
1451 -- and @Q@ is visible.
1452 --
1453 -- If you're absolutely sure that your tycon's kind doesn't end in a variable,
1454 -- it's OK if the callback function panics, as that's the only time it's
1455 -- consulted.
1456 partitionInvisibles :: TyCon -> (a -> Type) -> [a] -> ([a], [a])
1457 partitionInvisibles tc get_ty = go emptyTCvSubst (tyConKind tc)
1458 where
1459 go _ _ [] = ([], [])
1460 go subst (ForAllTy (TvBndr tv vis) res_ki) (x:xs)
1461 | isVisibleArgFlag vis = second (x :) (go subst' res_ki xs)
1462 | otherwise = first (x :) (go subst' res_ki xs)
1463 where
1464 subst' = extendTvSubst subst tv (get_ty x)
1465 go subst (TyVarTy tv) xs
1466 | Just ki <- lookupTyVar subst tv = go subst ki xs
1467 go _ _ xs = ([], xs) -- something is ill-kinded. But this can happen
1468 -- when printing errors. Assume everything is visible.
1469
1470 -- @isTauTy@ tests if a type has no foralls
1471 isTauTy :: Type -> Bool
1472 isTauTy ty | Just ty' <- coreView ty = isTauTy ty'
1473 isTauTy (TyVarTy _) = True
1474 isTauTy (LitTy {}) = True
1475 isTauTy (TyConApp tc tys) = all isTauTy tys && isTauTyCon tc
1476 isTauTy (AppTy a b) = isTauTy a && isTauTy b
1477 isTauTy (FunTy a b) = isTauTy a && isTauTy b
1478 isTauTy (ForAllTy {}) = False
1479 isTauTy (CastTy ty _) = isTauTy ty
1480 isTauTy (CoercionTy _) = False -- Not sure about this
1481
1482 {-
1483 %************************************************************************
1484 %* *
1485 TyBinders
1486 %* *
1487 %************************************************************************
1488 -}
1489
1490 -- | Make an anonymous binder
1491 mkAnonBinder :: Type -> TyBinder
1492 mkAnonBinder = Anon
1493
1494 -- | Does this binder bind a variable that is /not/ erased? Returns
1495 -- 'True' for anonymous binders.
1496 isAnonTyBinder :: TyBinder -> Bool
1497 isAnonTyBinder (Named {}) = False
1498 isAnonTyBinder (Anon {}) = True
1499
1500 isNamedTyBinder :: TyBinder -> Bool
1501 isNamedTyBinder (Named {}) = True
1502 isNamedTyBinder (Anon {}) = False
1503
1504 tyBinderType :: TyBinder -> Type
1505 -- Barely used
1506 tyBinderType (Named tvb) = binderKind tvb
1507 tyBinderType (Anon ty) = ty
1508
1509 -- | Extract a relevant type, if there is one.
1510 binderRelevantType_maybe :: TyBinder -> Maybe Type
1511 binderRelevantType_maybe (Named {}) = Nothing
1512 binderRelevantType_maybe (Anon ty) = Just ty
1513
1514 -- | Like 'maybe', but for binders.
1515 caseBinder :: TyBinder -- ^ binder to scrutinize
1516 -> (TyVarBinder -> a) -- ^ named case
1517 -> (Type -> a) -- ^ anonymous case
1518 -> a
1519 caseBinder (Named v) f _ = f v
1520 caseBinder (Anon t) _ d = d t
1521
1522 -- | Manufacture a new 'TyConBinder' from a 'TyBinder'. Anonymous
1523 -- 'TyBinder's are still assigned names as 'TyConBinder's, so we need
1524 -- the extra gunk with which to construct a 'Name'. Used when producing
1525 -- tyConTyVars from a datatype kind signature. Defined here to avoid module
1526 -- loops.
1527 mkTyBinderTyConBinder :: TyBinder -> SrcSpan -> Unique -> OccName -> TyConBinder
1528 mkTyBinderTyConBinder (Named (TvBndr tv argf)) _ _ _ = TvBndr tv (NamedTCB argf)
1529 mkTyBinderTyConBinder (Anon kind) loc uniq occ
1530 = TvBndr (mkTyVar (mkInternalName uniq occ loc) kind) AnonTCB
1531
1532 {-
1533 %************************************************************************
1534 %* *
1535 Pred
1536 * *
1537 ************************************************************************
1538
1539 Predicates on PredType
1540
1541 Note [isPredTy complications]
1542 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1543 You would think that we could define
1544 isPredTy ty = isConstraintKind (typeKind ty)
1545 But there are a number of complications:
1546
1547 * isPredTy is used when printing types, which can happen in debug
1548 printing during type checking of not-fully-zonked types. So it's
1549 not cool to say isConstraintKind (typeKind ty) because, absent
1550 zonking, the type might be ill-kinded, and typeKind crashes. Hence the
1551 rather tiresome story here
1552
1553 * isPredTy must return "True" to *unlifted* coercions, such as (t1 ~# t2)
1554 and (t1 ~R# t2), which are not of kind Constraint! Currently they are
1555 of kind #.
1556
1557 * If we do form the type '(C a => C [a]) => blah', then we'd like to
1558 print it as such. But that means that isPredTy must return True for
1559 (C a => C [a]). Admittedly that type is illegal in Haskell, but we
1560 want to print it nicely in error messages.
1561 -}
1562
1563 -- | Is the type suitable to classify a given/wanted in the typechecker?
1564 isPredTy :: Type -> Bool
1565 -- See Note [isPredTy complications]
1566 isPredTy ty = go ty []
1567 where
1568 go :: Type -> [KindOrType] -> Bool
1569 go (AppTy ty1 ty2) args = go ty1 (ty2 : args)
1570 go (TyVarTy tv) args = go_k (tyVarKind tv) args
1571 go (TyConApp tc tys) args = ASSERT( null args ) -- TyConApp invariant
1572 go_tc tc tys
1573 go (FunTy arg res) []
1574 | isPredTy arg = isPredTy res -- (Eq a => C a)
1575 | otherwise = False -- (Int -> Bool)
1576 go (ForAllTy _ ty) [] = go ty []
1577 go (CastTy _ co) args = go_k (pSnd (coercionKind co)) args
1578 go _ _ = False
1579
1580 go_tc :: TyCon -> [KindOrType] -> Bool
1581 go_tc tc args
1582 | tc `hasKey` eqPrimTyConKey || tc `hasKey` eqReprPrimTyConKey
1583 = args `lengthIs` 4 -- ~# and ~R# sadly have result kind #
1584 -- not Constraint; but we still want
1585 -- isPredTy to reply True.
1586 | otherwise = go_k (tyConKind tc) args
1587
1588 go_k :: Kind -> [KindOrType] -> Bool
1589 -- True <=> ('k' applied to 'kts') = Constraint
1590 go_k k [] = isConstraintKind k
1591 go_k k (arg:args) = case piResultTy_maybe k arg of
1592 Just k' -> go_k k' args
1593 Nothing -> WARN( True, text "isPredTy" <+> ppr ty )
1594 False
1595 -- This last case shouldn't happen under most circumstances. It can
1596 -- occur if we call isPredTy during kind checking, especially if one
1597 -- of the following happens:
1598 --
1599 -- 1. There is actually a kind error. Example in which this showed up:
1600 -- polykinds/T11399
1601 --
1602 -- 2. A type constructor application appears to be oversaturated. An
1603 -- example of this occurred in GHC Trac #13187:
1604 --
1605 -- {-# LANGUAGE PolyKinds #-}
1606 -- type Const a b = b
1607 -- f :: Const Int (,) Bool Char -> Char
1608 --
1609 -- We call isPredTy (Const k1 k2 Int (,) Bool Char
1610 -- where k1,k2 are unification variables that have been
1611 -- unified to *, and (*->*->*) resp, /but not zonked/.
1612 -- This shows that isPredTy can report a false negative
1613 -- if a constraint is similarly oversaturated, but
1614 -- it's hard to do better than isPredTy currently does without
1615 -- zonking, so we punt on such cases for now. This only happens
1616 -- during debug-printing, so it doesn't matter.
1617
1618 isClassPred, isEqPred, isNomEqPred, isIPPred :: PredType -> Bool
1619 isClassPred ty = case tyConAppTyCon_maybe ty of
1620 Just tyCon | isClassTyCon tyCon -> True
1621 _ -> False
1622 isEqPred ty = case tyConAppTyCon_maybe ty of
1623 Just tyCon -> tyCon `hasKey` eqPrimTyConKey
1624 || tyCon `hasKey` eqReprPrimTyConKey
1625 _ -> False
1626
1627 isNomEqPred ty = case tyConAppTyCon_maybe ty of
1628 Just tyCon -> tyCon `hasKey` eqPrimTyConKey
1629 _ -> False
1630
1631 isIPPred ty = case tyConAppTyCon_maybe ty of
1632 Just tc -> isIPTyCon tc
1633 _ -> False
1634
1635 isIPTyCon :: TyCon -> Bool
1636 isIPTyCon tc = tc `hasKey` ipClassKey
1637 -- Class and its corresponding TyCon have the same Unique
1638
1639 isIPClass :: Class -> Bool
1640 isIPClass cls = cls `hasKey` ipClassKey
1641
1642 isCTupleClass :: Class -> Bool
1643 isCTupleClass cls = isTupleTyCon (classTyCon cls)
1644
1645 isIPPred_maybe :: Type -> Maybe (FastString, Type)
1646 isIPPred_maybe ty =
1647 do (tc,[t1,t2]) <- splitTyConApp_maybe ty
1648 guard (isIPTyCon tc)
1649 x <- isStrLitTy t1
1650 return (x,t2)
1651
1652 {-
1653 Make PredTypes
1654
1655 --------------------- Equality types ---------------------------------
1656 -}
1657
1658 -- | Makes a lifted equality predicate at the given role
1659 mkPrimEqPredRole :: Role -> Type -> Type -> PredType
1660 mkPrimEqPredRole Nominal = mkPrimEqPred
1661 mkPrimEqPredRole Representational = mkReprPrimEqPred
1662 mkPrimEqPredRole Phantom = panic "mkPrimEqPredRole phantom"
1663
1664 -- | Creates a primitive type equality predicate.
1665 -- Invariant: the types are not Coercions
1666 mkPrimEqPred :: Type -> Type -> Type
1667 mkPrimEqPred ty1 ty2
1668 = TyConApp eqPrimTyCon [k1, k2, ty1, ty2]
1669 where
1670 k1 = typeKind ty1
1671 k2 = typeKind ty2
1672
1673 -- | Creates a primite type equality predicate with explicit kinds
1674 mkHeteroPrimEqPred :: Kind -> Kind -> Type -> Type -> Type
1675 mkHeteroPrimEqPred k1 k2 ty1 ty2 = TyConApp eqPrimTyCon [k1, k2, ty1, ty2]
1676
1677 -- | Creates a primitive representational type equality predicate
1678 -- with explicit kinds
1679 mkHeteroReprPrimEqPred :: Kind -> Kind -> Type -> Type -> Type
1680 mkHeteroReprPrimEqPred k1 k2 ty1 ty2
1681 = TyConApp eqReprPrimTyCon [k1, k2, ty1, ty2]
1682
1683 -- | Try to split up a coercion type into the types that it coerces
1684 splitCoercionType_maybe :: Type -> Maybe (Type, Type)
1685 splitCoercionType_maybe ty
1686 = do { (tc, [_, _, ty1, ty2]) <- splitTyConApp_maybe ty
1687 ; guard $ tc `hasKey` eqPrimTyConKey || tc `hasKey` eqReprPrimTyConKey
1688 ; return (ty1, ty2) }
1689
1690 mkReprPrimEqPred :: Type -> Type -> Type
1691 mkReprPrimEqPred ty1 ty2
1692 = TyConApp eqReprPrimTyCon [k1, k2, ty1, ty2]
1693 where
1694 k1 = typeKind ty1
1695 k2 = typeKind ty2
1696
1697 equalityTyCon :: Role -> TyCon
1698 equalityTyCon Nominal = eqPrimTyCon
1699 equalityTyCon Representational = eqReprPrimTyCon
1700 equalityTyCon Phantom = eqPhantPrimTyCon
1701
1702 -- --------------------- Dictionary types ---------------------------------
1703
1704 mkClassPred :: Class -> [Type] -> PredType
1705 mkClassPred clas tys = TyConApp (classTyCon clas) tys
1706
1707 isDictTy :: Type -> Bool
1708 isDictTy = isClassPred
1709
1710 isDictLikeTy :: Type -> Bool
1711 -- Note [Dictionary-like types]
1712 isDictLikeTy ty | Just ty' <- coreView ty = isDictLikeTy ty'
1713 isDictLikeTy ty = case splitTyConApp_maybe ty of
1714 Just (tc, tys) | isClassTyCon tc -> True
1715 | isTupleTyCon tc -> all isDictLikeTy tys
1716 _other -> False
1717
1718 {-
1719 Note [Dictionary-like types]
1720 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1721 Being "dictionary-like" means either a dictionary type or a tuple thereof.
1722 In GHC 6.10 we build implication constraints which construct such tuples,
1723 and if we land up with a binding
1724 t :: (C [a], Eq [a])
1725 t = blah
1726 then we want to treat t as cheap under "-fdicts-cheap" for example.
1727 (Implication constraints are normally inlined, but sadly not if the
1728 occurrence is itself inside an INLINE function! Until we revise the
1729 handling of implication constraints, that is.) This turned out to
1730 be important in getting good arities in DPH code. Example:
1731
1732 class C a
1733 class D a where { foo :: a -> a }
1734 instance C a => D (Maybe a) where { foo x = x }
1735
1736 bar :: (C a, C b) => a -> b -> (Maybe a, Maybe b)
1737 {-# INLINE bar #-}
1738 bar x y = (foo (Just x), foo (Just y))
1739
1740 Then 'bar' should jolly well have arity 4 (two dicts, two args), but
1741 we ended up with something like
1742 bar = __inline_me__ (\d1,d2. let t :: (D (Maybe a), D (Maybe b)) = ...
1743 in \x,y. <blah>)
1744
1745 This is all a bit ad-hoc; eg it relies on knowing that implication
1746 constraints build tuples.
1747
1748
1749 Decomposing PredType
1750 -}
1751
1752 -- | A choice of equality relation. This is separate from the type 'Role'
1753 -- because 'Phantom' does not define a (non-trivial) equality relation.
1754 data EqRel = NomEq | ReprEq
1755 deriving (Eq, Ord)
1756
1757 instance Outputable EqRel where
1758 ppr NomEq = text "nominal equality"
1759 ppr ReprEq = text "representational equality"
1760
1761 eqRelRole :: EqRel -> Role
1762 eqRelRole NomEq = Nominal
1763 eqRelRole ReprEq = Representational
1764
1765 data PredTree = ClassPred Class [Type]
1766 | EqPred EqRel Type Type
1767 | IrredPred PredType
1768
1769 classifyPredType :: PredType -> PredTree
1770 classifyPredType ev_ty = case splitTyConApp_maybe ev_ty of
1771 Just (tc, [_, _, ty1, ty2])
1772 | tc `hasKey` eqReprPrimTyConKey -> EqPred ReprEq ty1 ty2
1773 | tc `hasKey` eqPrimTyConKey -> EqPred NomEq ty1 ty2
1774 Just (tc, tys)
1775 | Just clas <- tyConClass_maybe tc -> ClassPred clas tys
1776 _ -> IrredPred ev_ty
1777
1778 getClassPredTys :: PredType -> (Class, [Type])
1779 getClassPredTys ty = case getClassPredTys_maybe ty of
1780 Just (clas, tys) -> (clas, tys)
1781 Nothing -> pprPanic "getClassPredTys" (ppr ty)
1782
1783 getClassPredTys_maybe :: PredType -> Maybe (Class, [Type])
1784 getClassPredTys_maybe ty = case splitTyConApp_maybe ty of
1785 Just (tc, tys) | Just clas <- tyConClass_maybe tc -> Just (clas, tys)
1786 _ -> Nothing
1787
1788 getEqPredTys :: PredType -> (Type, Type)
1789 getEqPredTys ty
1790 = case splitTyConApp_maybe ty of
1791 Just (tc, [_, _, ty1, ty2])
1792 | tc `hasKey` eqPrimTyConKey
1793 || tc `hasKey` eqReprPrimTyConKey
1794 -> (ty1, ty2)
1795 _ -> pprPanic "getEqPredTys" (ppr ty)
1796
1797 getEqPredTys_maybe :: PredType -> Maybe (Role, Type, Type)
1798 getEqPredTys_maybe ty
1799 = case splitTyConApp_maybe ty of
1800 Just (tc, [_, _, ty1, ty2])
1801 | tc `hasKey` eqPrimTyConKey -> Just (Nominal, ty1, ty2)
1802 | tc `hasKey` eqReprPrimTyConKey -> Just (Representational, ty1, ty2)
1803 _ -> Nothing
1804
1805 getEqPredRole :: PredType -> Role
1806 getEqPredRole ty = eqRelRole (predTypeEqRel ty)
1807
1808 -- | Get the equality relation relevant for a pred type.
1809 predTypeEqRel :: PredType -> EqRel
1810 predTypeEqRel ty
1811 | Just (tc, _) <- splitTyConApp_maybe ty
1812 , tc `hasKey` eqReprPrimTyConKey
1813 = ReprEq
1814 | otherwise
1815 = NomEq
1816
1817 {-
1818 %************************************************************************
1819 %* *
1820 Well-scoped tyvars
1821 * *
1822 ************************************************************************
1823 -}
1824
1825 -- | Do a topological sort on a list of tyvars,
1826 -- so that binders occur before occurrences
1827 -- E.g. given [ a::k, k::*, b::k ]
1828 -- it'll return a well-scoped list [ k::*, a::k, b::k ]
1829 --
1830 -- This is a deterministic sorting operation
1831 -- (that is, doesn't depend on Uniques).
1832 toposortTyVars :: [TyCoVar] -> [TyCoVar]
1833 toposortTyVars tvs = reverse $
1834 [ node_payload node | node <- topologicalSortG $
1835 graphFromEdgedVerticesOrd nodes ]
1836 where
1837 var_ids :: VarEnv Int
1838 var_ids = mkVarEnv (zip tvs [1..])
1839
1840 nodes :: [ Node Int TyVar ]
1841 nodes = [ DigraphNode
1842 tv
1843 (lookupVarEnv_NF var_ids tv)
1844 (mapMaybe (lookupVarEnv var_ids)
1845 (tyCoVarsOfTypeList (tyVarKind tv)))
1846 | tv <- tvs ]
1847
1848 -- | Extract a well-scoped list of variables from a deterministic set of
1849 -- variables. The result is deterministic.
1850 -- NB: There used to exist varSetElemsWellScoped :: VarSet -> [Var] which
1851 -- took a non-deterministic set and produced a non-deterministic
1852 -- well-scoped list. If you care about the list being well-scoped you also
1853 -- most likely care about it being in deterministic order.
1854 dVarSetElemsWellScoped :: DVarSet -> [Var]
1855 dVarSetElemsWellScoped = toposortTyVars . dVarSetElems
1856
1857 -- | Get the free vars of a type in scoped order
1858 tyCoVarsOfTypeWellScoped :: Type -> [TyVar]
1859 tyCoVarsOfTypeWellScoped = toposortTyVars . tyCoVarsOfTypeList
1860
1861 -- | Get the free vars of types in scoped order
1862 tyCoVarsOfTypesWellScoped :: [Type] -> [TyVar]
1863 tyCoVarsOfTypesWellScoped = toposortTyVars . tyCoVarsOfTypesList
1864
1865 {-
1866 ************************************************************************
1867 * *
1868 \subsection{Type families}
1869 * *
1870 ************************************************************************
1871 -}
1872
1873 mkFamilyTyConApp :: TyCon -> [Type] -> Type
1874 -- ^ Given a family instance TyCon and its arg types, return the
1875 -- corresponding family type. E.g:
1876 --
1877 -- > data family T a
1878 -- > data instance T (Maybe b) = MkT b
1879 --
1880 -- Where the instance tycon is :RTL, so:
1881 --
1882 -- > mkFamilyTyConApp :RTL Int = T (Maybe Int)
1883 mkFamilyTyConApp tc tys
1884 | Just (fam_tc, fam_tys) <- tyConFamInst_maybe tc
1885 , let tvs = tyConTyVars tc
1886 fam_subst = ASSERT2( tvs `equalLength` tys, ppr tc <+> ppr tys )
1887 zipTvSubst tvs tys
1888 = mkTyConApp fam_tc (substTys fam_subst fam_tys)
1889 | otherwise
1890 = mkTyConApp tc tys
1891
1892 -- | Get the type on the LHS of a coercion induced by a type/data
1893 -- family instance.
1894 coAxNthLHS :: CoAxiom br -> Int -> Type
1895 coAxNthLHS ax ind =
1896 mkTyConApp (coAxiomTyCon ax) (coAxBranchLHS (coAxiomNthBranch ax ind))
1897
1898 -- | Pretty prints a 'TyCon', using the family instance in case of a
1899 -- representation tycon. For example:
1900 --
1901 -- > data T [a] = ...
1902 --
1903 -- In that case we want to print @T [a]@, where @T@ is the family 'TyCon'
1904 pprSourceTyCon :: TyCon -> SDoc
1905 pprSourceTyCon tycon
1906 | Just (fam_tc, tys) <- tyConFamInst_maybe tycon
1907 = ppr $ fam_tc `TyConApp` tys -- can't be FunTyCon
1908 | otherwise
1909 = ppr tycon
1910
1911 -- @isTauTy@ tests if a type has no foralls
1912 isFamFreeTy :: Type -> Bool
1913 isFamFreeTy ty | Just ty' <- coreView ty = isFamFreeTy ty'
1914 isFamFreeTy (TyVarTy _) = True
1915 isFamFreeTy (LitTy {}) = True
1916 isFamFreeTy (TyConApp tc tys) = all isFamFreeTy tys && isFamFreeTyCon tc
1917 isFamFreeTy (AppTy a b) = isFamFreeTy a && isFamFreeTy b
1918 isFamFreeTy (FunTy a b) = isFamFreeTy a && isFamFreeTy b
1919 isFamFreeTy (ForAllTy _ ty) = isFamFreeTy ty
1920 isFamFreeTy (CastTy ty _) = isFamFreeTy ty
1921 isFamFreeTy (CoercionTy _) = False -- Not sure about this
1922
1923 {-
1924 ************************************************************************
1925 * *
1926 \subsection{Liftedness}
1927 * *
1928 ************************************************************************
1929 -}
1930
1931 -- | Returns Just True if this type is surely lifted, Just False
1932 -- if it is surely unlifted, Nothing if we can't be sure (i.e., it is
1933 -- levity polymorphic), and panics if the kind does not have the shape
1934 -- TYPE r.
1935 isLiftedType_maybe :: HasDebugCallStack => Type -> Maybe Bool
1936 isLiftedType_maybe ty = go (getRuntimeRep ty)
1937 where
1938 go rr | Just rr' <- coreView rr = go rr'
1939 go (TyConApp lifted_rep [])
1940 | lifted_rep `hasKey` liftedRepDataConKey = Just True
1941 go (TyConApp {}) = Just False -- everything else is unlifted
1942 go _ = Nothing -- levity polymorphic
1943
1944 -- | See "Type#type_classification" for what an unlifted type is.
1945 -- Panics on levity polymorphic types.
1946 isUnliftedType :: HasDebugCallStack => Type -> Bool
1947 -- isUnliftedType returns True for forall'd unlifted types:
1948 -- x :: forall a. Int#
1949 -- I found bindings like these were getting floated to the top level.
1950 -- They are pretty bogus types, mind you. It would be better never to
1951 -- construct them
1952 isUnliftedType ty
1953 = not (isLiftedType_maybe ty `orElse`
1954 pprPanic "isUnliftedType" (ppr ty <+> dcolon <+> ppr (typeKind ty)))
1955
1956 -- | Is this a type of kind RuntimeRep? (e.g. LiftedRep)
1957 isRuntimeRepKindedTy :: Type -> Bool
1958 isRuntimeRepKindedTy = isRuntimeRepTy . typeKind
1959
1960 -- | Drops prefix of RuntimeRep constructors in 'TyConApp's. Useful for e.g.
1961 -- dropping 'LiftedRep arguments of unboxed tuple TyCon applications:
1962 --
1963 -- dropRuntimeRepArgs [ 'LiftedRep, 'IntRep
1964 -- , String, Int# ] == [String, Int#]
1965 --
1966 dropRuntimeRepArgs :: [Type] -> [Type]
1967 dropRuntimeRepArgs = dropWhile isRuntimeRepKindedTy
1968
1969 -- | Extract the RuntimeRep classifier of a type. For instance,
1970 -- @getRuntimeRep_maybe Int = LiftedRep@. Returns 'Nothing' if this is not
1971 -- possible.
1972 getRuntimeRep_maybe :: HasDebugCallStack
1973 => Type -> Maybe Type
1974 getRuntimeRep_maybe = getRuntimeRepFromKind_maybe . typeKind
1975
1976 -- | Extract the RuntimeRep classifier of a type. For instance,
1977 -- @getRuntimeRep_maybe Int = LiftedRep@. Panics if this is not possible.
1978 getRuntimeRep :: HasDebugCallStack => Type -> Type
1979 getRuntimeRep ty
1980 = case getRuntimeRep_maybe ty of
1981 Just r -> r
1982 Nothing -> pprPanic "getRuntimeRep" (ppr ty <+> dcolon <+> ppr (typeKind ty))
1983
1984 -- | Extract the RuntimeRep classifier of a type from its kind. For example,
1985 -- @getRuntimeRepFromKind * = LiftedRep@; Panics if this is not possible.
1986 getRuntimeRepFromKind :: HasDebugCallStack
1987 => Type -> Type
1988 getRuntimeRepFromKind k =
1989 case getRuntimeRepFromKind_maybe k of
1990 Just r -> r
1991 Nothing -> pprPanic "getRuntimeRepFromKind"
1992 (ppr k <+> dcolon <+> ppr (typeKind k))
1993
1994 -- | Extract the RuntimeRep classifier of a type from its kind. For example,
1995 -- @getRuntimeRepFromKind * = LiftedRep@; Returns 'Nothing' if this is not
1996 -- possible.
1997 getRuntimeRepFromKind_maybe :: HasDebugCallStack
1998 => Type -> Maybe Type
1999 getRuntimeRepFromKind_maybe = go
2000 where
2001 go k | Just k' <- coreView k = go k'
2002 go k
2003 | Just (_tc, [arg]) <- splitTyConApp_maybe k
2004 = ASSERT2( _tc `hasKey` tYPETyConKey, ppr k )
2005 Just arg
2006 go _ = Nothing
2007
2008 isUnboxedTupleType :: Type -> Bool
2009 isUnboxedTupleType ty
2010 = tyConAppTyCon (getRuntimeRep ty) `hasKey` tupleRepDataConKey
2011 -- NB: Do not use typePrimRep, as that can't tell the difference between
2012 -- unboxed tuples and unboxed sums
2013
2014
2015 isUnboxedSumType :: Type -> Bool
2016 isUnboxedSumType ty
2017 = tyConAppTyCon (getRuntimeRep ty) `hasKey` sumRepDataConKey
2018
2019 -- | See "Type#type_classification" for what an algebraic type is.
2020 -- Should only be applied to /types/, as opposed to e.g. partially
2021 -- saturated type constructors
2022 isAlgType :: Type -> Bool
2023 isAlgType ty
2024 = case splitTyConApp_maybe ty of
2025 Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc )
2026 isAlgTyCon tc
2027 _other -> False
2028
2029 -- | Check whether a type is a data family type
2030 isDataFamilyAppType :: Type -> Bool
2031 isDataFamilyAppType ty = case tyConAppTyCon_maybe ty of
2032 Just tc -> isDataFamilyTyCon tc
2033 _ -> False
2034
2035 -- | Computes whether an argument (or let right hand side) should
2036 -- be computed strictly or lazily, based only on its type.
2037 -- Currently, it's just 'isUnliftedType'. Panics on levity-polymorphic types.
2038 isStrictType :: HasDebugCallStack => Type -> Bool
2039 isStrictType = isUnliftedType
2040
2041 isPrimitiveType :: Type -> Bool
2042 -- ^ Returns true of types that are opaque to Haskell.
2043 isPrimitiveType ty = case splitTyConApp_maybe ty of
2044 Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc )
2045 isPrimTyCon tc
2046 _ -> False
2047
2048 {-
2049 ************************************************************************
2050 * *
2051 \subsection{Join points}
2052 * *
2053 ************************************************************************
2054 -}
2055
2056 -- | Determine whether a type could be the type of a join point of given total
2057 -- arity, according to the polymorphism rule. A join point cannot be polymorphic
2058 -- in its return type, since given
2059 -- join j @a @b x y z = e1 in e2,
2060 -- the types of e1 and e2 must be the same, and a and b are not in scope for e2.
2061 -- (See Note [The polymorphism rule of join points] in CoreSyn.) Returns False
2062 -- also if the type simply doesn't have enough arguments.
2063 --
2064 -- Note that we need to know how many arguments (type *and* value) the putative
2065 -- join point takes; for instance, if
2066 -- j :: forall a. a -> Int
2067 -- then j could be a binary join point returning an Int, but it could *not* be a
2068 -- unary join point returning a -> Int.
2069 --
2070 -- TODO: See Note [Excess polymorphism and join points]
2071 isValidJoinPointType :: JoinArity -> Type -> Bool
2072 isValidJoinPointType arity ty
2073 = valid_under emptyVarSet arity ty
2074 where
2075 valid_under tvs arity ty
2076 | arity == 0
2077 = isEmptyVarSet (tvs `intersectVarSet` tyCoVarsOfType ty)
2078 | Just (t, ty') <- splitForAllTy_maybe ty
2079 = valid_under (tvs `extendVarSet` t) (arity-1) ty'
2080 | Just (_, res_ty) <- splitFunTy_maybe ty
2081 = valid_under tvs (arity-1) res_ty
2082 | otherwise
2083 = False
2084
2085 {-
2086 ************************************************************************
2087 * *
2088 \subsection{Sequencing on types}
2089 * *
2090 ************************************************************************
2091 -}
2092
2093 seqType :: Type -> ()
2094 seqType (LitTy n) = n `seq` ()
2095 seqType (TyVarTy tv) = tv `seq` ()
2096 seqType (AppTy t1 t2) = seqType t1 `seq` seqType t2
2097 seqType (FunTy t1 t2) = seqType t1 `seq` seqType t2
2098 seqType (TyConApp tc tys) = tc `seq` seqTypes tys
2099 seqType (ForAllTy (TvBndr tv _) ty) = seqType (tyVarKind tv) `seq` seqType ty
2100 seqType (CastTy ty co) = seqType ty `seq` seqCo co
2101 seqType (CoercionTy co) = seqCo co
2102
2103 seqTypes :: [Type] -> ()
2104 seqTypes [] = ()
2105 seqTypes (ty:tys) = seqType ty `seq` seqTypes tys
2106
2107 {-
2108 ************************************************************************
2109 * *
2110 Comparison for types
2111 (We don't use instances so that we know where it happens)
2112 * *
2113 ************************************************************************
2114
2115 Note [Equality on AppTys]
2116 ~~~~~~~~~~~~~~~~~~~~~~~~~
2117 In our cast-ignoring equality, we want to say that the following two
2118 are equal:
2119
2120 (Maybe |> co) (Int |> co') ~? Maybe Int
2121
2122 But the left is an AppTy while the right is a TyConApp. The solution is
2123 to use repSplitAppTy_maybe to break up the TyConApp into its pieces and
2124 then continue. Easy to do, but also easy to forget to do.
2125
2126 -}
2127
2128 eqType :: Type -> Type -> Bool
2129 -- ^ Type equality on source types. Does not look through @newtypes@ or
2130 -- 'PredType's, but it does look through type synonyms.
2131 -- This first checks that the kinds of the types are equal and then
2132 -- checks whether the types are equal, ignoring casts and coercions.
2133 -- (The kind check is a recursive call, but since all kinds have type
2134 -- @Type@, there is no need to check the types of kinds.)
2135 -- See also Note [Non-trivial definitional equality] in TyCoRep.
2136 eqType t1 t2 = isEqual $ nonDetCmpType t1 t2
2137 -- It's OK to use nonDetCmpType here and eqType is deterministic,
2138 -- nonDetCmpType does equality deterministically
2139
2140 -- | Compare types with respect to a (presumably) non-empty 'RnEnv2'.
2141 eqTypeX :: RnEnv2 -> Type -> Type -> Bool
2142 eqTypeX env t1 t2 = isEqual $ nonDetCmpTypeX env t1 t2
2143 -- It's OK to use nonDetCmpType here and eqTypeX is deterministic,
2144 -- nonDetCmpTypeX does equality deterministically
2145
2146 -- | Type equality on lists of types, looking through type synonyms
2147 -- but not newtypes.
2148 eqTypes :: [Type] -> [Type] -> Bool
2149 eqTypes tys1 tys2 = isEqual $ nonDetCmpTypes tys1 tys2
2150 -- It's OK to use nonDetCmpType here and eqTypes is deterministic,
2151 -- nonDetCmpTypes does equality deterministically
2152
2153 eqVarBndrs :: RnEnv2 -> [Var] -> [Var] -> Maybe RnEnv2
2154 -- Check that the var lists are the same length
2155 -- and have matching kinds; if so, extend the RnEnv2
2156 -- Returns Nothing if they don't match
2157 eqVarBndrs env [] []
2158 = Just env
2159 eqVarBndrs env (tv1:tvs1) (tv2:tvs2)
2160 | eqTypeX env (tyVarKind tv1) (tyVarKind tv2)
2161 = eqVarBndrs (rnBndr2 env tv1 tv2) tvs1 tvs2
2162 eqVarBndrs _ _ _= Nothing
2163
2164 -- Now here comes the real worker
2165
2166 {-
2167 Note [nonDetCmpType nondeterminism]
2168 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2169 nonDetCmpType is implemented in terms of nonDetCmpTypeX. nonDetCmpTypeX
2170 uses nonDetCmpTc which compares TyCons by their Unique value. Using Uniques for
2171 ordering leads to nondeterminism. We hit the same problem in the TyVarTy case,
2172 comparing type variables is nondeterministic, note the call to nonDetCmpVar in
2173 nonDetCmpTypeX.
2174 See Note [Unique Determinism] for more details.
2175 -}
2176
2177 nonDetCmpType :: Type -> Type -> Ordering
2178 nonDetCmpType t1 t2
2179 -- we know k1 and k2 have the same kind, because they both have kind *.
2180 = nonDetCmpTypeX rn_env t1 t2
2181 where
2182 rn_env = mkRnEnv2 (mkInScopeSet (tyCoVarsOfTypes [t1, t2]))
2183
2184 nonDetCmpTypes :: [Type] -> [Type] -> Ordering
2185 nonDetCmpTypes ts1 ts2 = nonDetCmpTypesX rn_env ts1 ts2
2186 where
2187 rn_env = mkRnEnv2 (mkInScopeSet (tyCoVarsOfTypes (ts1 ++ ts2)))
2188
2189 -- | An ordering relation between two 'Type's (known below as @t1 :: k1@
2190 -- and @t2 :: k2@)
2191 data TypeOrdering = TLT -- ^ @t1 < t2@
2192 | TEQ -- ^ @t1 ~ t2@ and there are no casts in either,
2193 -- therefore we can conclude @k1 ~ k2@
2194 | TEQX -- ^ @t1 ~ t2@ yet one of the types contains a cast so
2195 -- they may differ in kind.
2196 | TGT -- ^ @t1 > t2@
2197 deriving (Eq, Ord, Enum, Bounded)
2198
2199 nonDetCmpTypeX :: RnEnv2 -> Type -> Type -> Ordering -- Main workhorse
2200 -- See Note [Non-trivial definitional equality] in TyCoRep
2201 nonDetCmpTypeX env orig_t1 orig_t2 =
2202 case go env orig_t1 orig_t2 of
2203 -- If there are casts then we also need to do a comparison of the kinds of
2204 -- the types being compared
2205 TEQX -> toOrdering $ go env k1 k2
2206 ty_ordering -> toOrdering ty_ordering
2207 where
2208 k1 = typeKind orig_t1
2209 k2 = typeKind orig_t2
2210
2211 toOrdering :: TypeOrdering -> Ordering
2212 toOrdering TLT = LT
2213 toOrdering TEQ = EQ
2214 toOrdering TEQX = EQ
2215 toOrdering TGT = GT
2216
2217 liftOrdering :: Ordering -> TypeOrdering
2218 liftOrdering LT = TLT
2219 liftOrdering EQ = TEQ
2220 liftOrdering GT = TGT
2221
2222 thenCmpTy :: TypeOrdering -> TypeOrdering -> TypeOrdering
2223 thenCmpTy TEQ rel = rel
2224 thenCmpTy TEQX rel = hasCast rel
2225 thenCmpTy rel _ = rel
2226
2227 hasCast :: TypeOrdering -> TypeOrdering
2228 hasCast TEQ = TEQX
2229 hasCast rel = rel
2230
2231 -- Returns both the resulting ordering relation between the two types
2232 -- and whether either contains a cast.
2233 go :: RnEnv2 -> Type -> Type -> TypeOrdering
2234 go env t1 t2
2235 | Just t1' <- coreView t1 = go env t1' t2
2236 | Just t2' <- coreView t2 = go env t1 t2'
2237
2238 go env (TyVarTy tv1) (TyVarTy tv2)
2239 = liftOrdering $ rnOccL env tv1 `nonDetCmpVar` rnOccR env tv2
2240 go env (ForAllTy (TvBndr tv1 _) t1) (ForAllTy (TvBndr tv2 _) t2)
2241 = go env (tyVarKind tv1) (tyVarKind tv2)
2242 `thenCmpTy` go (rnBndr2 env tv1 tv2) t1 t2
2243 -- See Note [Equality on AppTys]
2244 go env (AppTy s1 t1) ty2
2245 | Just (s2, t2) <- repSplitAppTy_maybe ty2
2246 = go env s1 s2 `thenCmpTy` go env t1 t2
2247 go env ty1 (AppTy s2 t2)
2248 | Just (s1, t1) <- repSplitAppTy_maybe ty1
2249 = go env s1 s2 `thenCmpTy` go env t1 t2
2250 go env (FunTy s1 t1) (FunTy s2 t2)
2251 = go env s1 s2 `thenCmpTy` go env t1 t2
2252 go env (TyConApp tc1 tys1) (TyConApp tc2 tys2)
2253 = liftOrdering (tc1 `nonDetCmpTc` tc2) `thenCmpTy` gos env tys1 tys2
2254 go _ (LitTy l1) (LitTy l2) = liftOrdering (compare l1 l2)
2255 go env (CastTy t1 _) t2 = hasCast $ go env t1 t2
2256 go env t1 (CastTy t2 _) = hasCast $ go env t1 t2
2257
2258 go _ (CoercionTy {}) (CoercionTy {}) = TEQ
2259
2260 -- Deal with the rest: TyVarTy < CoercionTy < AppTy < LitTy < TyConApp < ForAllTy
2261 go _ ty1 ty2
2262 = liftOrdering $ (get_rank ty1) `compare` (get_rank ty2)
2263 where get_rank :: Type -> Int
2264 get_rank (CastTy {})
2265 = pprPanic "nonDetCmpTypeX.get_rank" (ppr [ty1,ty2])
2266 get_rank (TyVarTy {}) = 0
2267 get_rank (CoercionTy {}) = 1
2268 get_rank (AppTy {}) = 3
2269 get_rank (LitTy {}) = 4
2270 get_rank (TyConApp {}) = 5
2271 get_rank (FunTy {}) = 6
2272 get_rank (ForAllTy {}) = 7
2273
2274 gos :: RnEnv2 -> [Type] -> [Type] -> TypeOrdering
2275 gos _ [] [] = TEQ
2276 gos _ [] _ = TLT
2277 gos _ _ [] = TGT
2278 gos env (ty1:tys1) (ty2:tys2) = go env ty1 ty2 `thenCmpTy` gos env tys1 tys2
2279
2280 -------------
2281 nonDetCmpTypesX :: RnEnv2 -> [Type] -> [Type] -> Ordering
2282 nonDetCmpTypesX _ [] [] = EQ
2283 nonDetCmpTypesX env (t1:tys1) (t2:tys2) = nonDetCmpTypeX env t1 t2
2284 `thenCmp` nonDetCmpTypesX env tys1 tys2
2285 nonDetCmpTypesX _ [] _ = LT
2286 nonDetCmpTypesX _ _ [] = GT
2287
2288 -------------
2289 -- | Compare two 'TyCon's. NB: This should /never/ see the "star synonyms",
2290 -- as recognized by Kind.isStarKindSynonymTyCon. See Note
2291 -- [Kind Constraint and kind *] in Kind.
2292 -- See Note [nonDetCmpType nondeterminism]
2293 nonDetCmpTc :: TyCon -> TyCon -> Ordering
2294 nonDetCmpTc tc1 tc2
2295 = ASSERT( not (isStarKindSynonymTyCon tc1) && not (isStarKindSynonymTyCon tc2) )
2296 u1 `nonDetCmpUnique` u2
2297 where
2298 u1 = tyConUnique tc1
2299 u2 = tyConUnique tc2
2300
2301 {-
2302 ************************************************************************
2303 * *
2304 The kind of a type
2305 * *
2306 ************************************************************************
2307 -}
2308
2309 typeKind :: HasDebugCallStack => Type -> Kind
2310 typeKind (TyConApp tc tys) = piResultTys (tyConKind tc) tys
2311 typeKind (AppTy fun arg) = piResultTy (typeKind fun) arg
2312 typeKind (LitTy l) = typeLiteralKind l
2313 typeKind (FunTy {}) = liftedTypeKind
2314 typeKind (ForAllTy _ ty) = typeKind ty
2315 typeKind (TyVarTy tyvar) = tyVarKind tyvar
2316 typeKind (CastTy _ty co) = pSnd $ coercionKind co
2317 typeKind (CoercionTy co) = coercionType co
2318
2319 typeLiteralKind :: TyLit -> Kind
2320 typeLiteralKind l =
2321 case l of
2322 NumTyLit _ -> typeNatKind
2323 StrTyLit _ -> typeSymbolKind
2324
2325 -- | Returns True if a type is levity polymorphic. Should be the same
2326 -- as (isKindLevPoly . typeKind) but much faster.
2327 -- Precondition: The type has kind (TYPE blah)
2328 isTypeLevPoly :: Type -> Bool
2329 isTypeLevPoly = go
2330 where
2331 go ty@(TyVarTy {}) = check_kind ty
2332 go ty@(AppTy {}) = check_kind ty
2333 go ty@(TyConApp tc _) | not (isTcLevPoly tc) = False
2334 | otherwise = check_kind ty
2335 go (ForAllTy _ ty) = go ty
2336 go (FunTy {}) = False
2337 go (LitTy {}) = False
2338 go ty@(CastTy {}) = check_kind ty
2339 go ty@(CoercionTy {}) = pprPanic "isTypeLevPoly co" (ppr ty)
2340
2341 check_kind = isKindLevPoly . typeKind
2342
2343 -- | Looking past all pi-types, is the end result potentially levity polymorphic?
2344 -- Example: True for (forall r (a :: TYPE r). String -> a)
2345 -- Example: False for (forall r1 r2 (a :: TYPE r1) (b :: TYPE r2). a -> b -> Type)
2346 resultIsLevPoly :: Type -> Bool
2347 resultIsLevPoly = isTypeLevPoly . snd . splitPiTys
2348
2349 {-
2350 %************************************************************************
2351 %* *
2352 Miscellaneous functions
2353 %* *
2354 %************************************************************************
2355
2356 -}
2357 -- | All type constructors occurring in the type; looking through type
2358 -- synonyms, but not newtypes.
2359 -- When it finds a Class, it returns the class TyCon.
2360 tyConsOfType :: Type -> UniqSet TyCon
2361 tyConsOfType ty
2362 = go ty
2363 where
2364 go :: Type -> UniqSet TyCon -- The UniqSet does duplicate elim
2365 go ty | Just ty' <- coreView ty = go ty'
2366 go (TyVarTy {}) = emptyUniqSet
2367 go (LitTy {}) = emptyUniqSet
2368 go (TyConApp tc tys) = go_tc tc `unionUniqSets` go_s tys
2369 go (AppTy a b) = go a `unionUniqSets` go b
2370 go (FunTy a b) = go a `unionUniqSets` go b `unionUniqSets` go_tc funTyCon
2371 go (ForAllTy (TvBndr tv _) ty) = go ty `unionUniqSets` go (tyVarKind tv)
2372 go (CastTy ty co) = go ty `unionUniqSets` go_co co
2373 go (CoercionTy co) = go_co co
2374
2375 go_co (Refl _ ty) = go ty
2376 go_co (TyConAppCo _ tc args) = go_tc tc `unionUniqSets` go_cos args
2377 go_co (AppCo co arg) = go_co co `unionUniqSets` go_co arg
2378 go_co (ForAllCo _ kind_co co) = go_co kind_co `unionUniqSets` go_co co
2379 go_co (FunCo _ co1 co2) = go_co co1 `unionUniqSets` go_co co2
2380 go_co (AxiomInstCo ax _ args) = go_ax ax `unionUniqSets` go_cos args
2381 go_co (UnivCo p _ t1 t2) = go_prov p `unionUniqSets` go t1 `unionUniqSets` go t2
2382 go_co (CoVarCo {}) = emptyUniqSet
2383 go_co (SymCo co) = go_co co
2384 go_co (TransCo co1 co2) = go_co co1 `unionUniqSets` go_co co2
2385 go_co (NthCo _ co) = go_co co
2386 go_co (LRCo _ co) = go_co co
2387 go_co (InstCo co arg) = go_co co `unionUniqSets` go_co arg
2388 go_co (CoherenceCo co1 co2) = go_co co1 `unionUniqSets` go_co co2
2389 go_co (KindCo co) = go_co co
2390 go_co (SubCo co) = go_co co
2391 go_co (AxiomRuleCo _ cs) = go_cos cs
2392
2393 go_prov UnsafeCoerceProv = emptyUniqSet
2394 go_prov (PhantomProv co) = go_co co
2395 go_prov (ProofIrrelProv co) = go_co co
2396 go_prov (PluginProv _) = emptyUniqSet
2397 go_prov (HoleProv _) = emptyUniqSet
2398 -- this last case can happen from the tyConsOfType used from
2399 -- checkTauTvUpdate
2400
2401 go_s tys = foldr (unionUniqSets . go) emptyUniqSet tys
2402 go_cos cos = foldr (unionUniqSets . go_co) emptyUniqSet cos
2403
2404 go_tc tc = unitUniqSet tc
2405 go_ax ax = go_tc $ coAxiomTyCon ax
2406
2407 -- | Find the result 'Kind' of a type synonym,
2408 -- after applying it to its 'arity' number of type variables
2409 -- Actually this function works fine on data types too,
2410 -- but they'd always return '*', so we never need to ask
2411 synTyConResKind :: TyCon -> Kind
2412 synTyConResKind tycon = piResultTys (tyConKind tycon) (mkTyVarTys (tyConTyVars tycon))
2413
2414 -- | Retrieve the free variables in this type, splitting them based
2415 -- on whether they are used visibly or invisibly. Invisible ones come
2416 -- first.
2417 splitVisVarsOfType :: Type -> Pair TyCoVarSet
2418 splitVisVarsOfType orig_ty = Pair invis_vars vis_vars
2419 where
2420 Pair invis_vars1 vis_vars = go orig_ty
2421 invis_vars = invis_vars1 `minusVarSet` vis_vars
2422
2423 go (TyVarTy tv) = Pair (tyCoVarsOfType $ tyVarKind tv) (unitVarSet tv)
2424 go (AppTy t1 t2) = go t1 `mappend` go t2
2425 go (TyConApp tc tys) = go_tc tc tys
2426 go (FunTy t1 t2) = go t1 `mappend` go t2
2427 go (ForAllTy (TvBndr tv _) ty)
2428 = ((`delVarSet` tv) <$> go ty) `mappend`
2429 (invisible (tyCoVarsOfType $ tyVarKind tv))
2430 go (LitTy {}) = mempty
2431 go (CastTy ty co) = go ty `mappend` invisible (tyCoVarsOfCo co)
2432 go (CoercionTy co) = invisible $ tyCoVarsOfCo co
2433
2434 invisible vs = Pair vs emptyVarSet
2435
2436 go_tc tc tys = let (invis, vis) = partitionInvisibles tc id tys in
2437 invisible (tyCoVarsOfTypes invis) `mappend` foldMap go vis
2438
2439 splitVisVarsOfTypes :: [Type] -> Pair TyCoVarSet
2440 splitVisVarsOfTypes = foldMap splitVisVarsOfType
2441
2442 modifyJoinResTy :: Int -- Number of binders to skip
2443 -> (Type -> Type) -- Function to apply to result type
2444 -> Type -- Type of join point
2445 -> Type -- New type
2446 -- INVARIANT: If any of the first n binders are foralls, those tyvars cannot
2447 -- appear in the original result type. See isValidJoinPointType.
2448 modifyJoinResTy orig_ar f orig_ty
2449 = go orig_ar orig_ty
2450 where
2451 go 0 ty = f ty
2452 go n ty | Just (arg_bndr, res_ty) <- splitPiTy_maybe ty
2453 = mkPiTy arg_bndr (go (n-1) res_ty)
2454 | otherwise
2455 = pprPanic "modifyJoinResTy" (ppr orig_ar <+> ppr orig_ty)
2456
2457 setJoinResTy :: Int -- Number of binders to skip
2458 -> Type -- New result type
2459 -> Type -- Type of join point
2460 -> Type -- New type
2461 -- INVARIANT: Same as for modifyJoinResTy
2462 setJoinResTy ar new_res_ty ty
2463 = modifyJoinResTy ar (const new_res_ty) ty