-
Notifications
You must be signed in to change notification settings - Fork 10.5k
/
Copy pathTypeCheckProtocolInference.cpp
2733 lines (2306 loc) · 97.1 KB
/
TypeCheckProtocolInference.cpp
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
//===--- TypeCheckProtocolInference.cpp - Associated Type Inference -------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
//
// This file implements semantic analysis for protocols, in particular, checking
// whether a given type conforms to a given protocol.
//===----------------------------------------------------------------------===//
#include "TypeCheckProtocol.h"
#include "DerivedConformances.h"
#include "TypeChecker.h"
#include "swift/AST/Decl.h"
#include "swift/AST/GenericSignature.h"
#include "swift/AST/NameLookupRequests.h"
#include "swift/AST/ProtocolConformance.h"
#include "swift/AST/SubstitutionMap.h"
#include "swift/AST/TypeMatcher.h"
#include "swift/AST/Types.h"
#include "swift/Basic/Defer.h"
#include "swift/ClangImporter/ClangModule.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/TinyPtrVector.h"
#define DEBUG_TYPE "Associated type inference"
#include "llvm/Support/Debug.h"
STATISTIC(NumSolutionStates, "# of solution states visited");
STATISTIC(NumSolutionStatesFailedCheck,
"# of solution states that failed constraints check");
STATISTIC(NumConstrainedExtensionChecks,
"# of constrained extension checks");
STATISTIC(NumConstrainedExtensionChecksFailed,
"# of constrained extension checks failed");
STATISTIC(NumDuplicateSolutionStates,
"# of duplicate solution states ");
using namespace swift;
void InferredAssociatedTypesByWitness::dump() const {
dump(llvm::errs(), 0);
}
void InferredAssociatedTypesByWitness::dump(llvm::raw_ostream &out,
unsigned indent) const {
out << "\n";
out.indent(indent) << "(";
if (Witness) {
Witness->dumpRef(out);
}
for (const auto &inferred : Inferred) {
out << "\n";
out.indent(indent + 2);
out << inferred.first->getName() << " := "
<< inferred.second.getString();
}
for (const auto &inferred : NonViable) {
out << "\n";
out.indent(indent + 2);
out << std::get<0>(inferred)->getName() << " := "
<< std::get<1>(inferred).getString();
auto type = std::get<2>(inferred).getRequirement();
out << " [failed constraint " << type.getString() << "]";
}
out << ")";
}
void InferredTypeWitnessesSolution::dump() const {
const auto numValueWitnesses = ValueWitnesses.size();
llvm::errs() << "Type Witnesses:\n";
for (auto &typeWitness : TypeWitnesses) {
llvm::errs() << " " << typeWitness.first->getName() << " := ";
typeWitness.second.first->print(llvm::errs());
if (typeWitness.second.second == numValueWitnesses) {
llvm::errs() << ", abstract";
} else {
llvm::errs() << ", inferred from $" << typeWitness.second.second;
}
llvm::errs() << '\n';
}
llvm::errs() << "Value Witnesses:\n";
for (unsigned i : indices(ValueWitnesses)) {
const auto &valueWitness = ValueWitnesses[i];
llvm::errs() << '$' << i << ":\n ";
valueWitness.first->dumpRef(llvm::errs());
llvm::errs() << " ->\n ";
valueWitness.second->dumpRef(llvm::errs());
llvm::errs() << '\n';
}
}
namespace {
void dumpInferredAssociatedTypesByWitnesses(
const InferredAssociatedTypesByWitnesses &inferred,
llvm::raw_ostream &out,
unsigned indent) {
for (const auto &value : inferred) {
value.dump(out, indent);
}
}
void dumpInferredAssociatedTypesByWitnesses(
const InferredAssociatedTypesByWitnesses &inferred) LLVM_ATTRIBUTE_USED;
void dumpInferredAssociatedTypesByWitnesses(
const InferredAssociatedTypesByWitnesses &inferred) {
dumpInferredAssociatedTypesByWitnesses(inferred, llvm::errs(), 0);
}
void dumpInferredAssociatedTypes(const InferredAssociatedTypes &inferred,
llvm::raw_ostream &out,
unsigned indent) {
for (const auto &value : inferred) {
out << "\n";
out.indent(indent) << "(";
value.first->dumpRef(out);
dumpInferredAssociatedTypesByWitnesses(value.second, out, indent + 2);
out << ")";
}
out << "\n";
}
void dumpInferredAssociatedTypes(
const InferredAssociatedTypes &inferred) LLVM_ATTRIBUTE_USED;
void dumpInferredAssociatedTypes(const InferredAssociatedTypes &inferred) {
dumpInferredAssociatedTypes(inferred, llvm::errs(), 0);
}
}
AssociatedTypeInference::AssociatedTypeInference(
ASTContext &ctx, NormalProtocolConformance *conformance)
: ctx(ctx), conformance(conformance), proto(conformance->getProtocol()),
dc(conformance->getDeclContext()), adoptee(conformance->getType()) {}
static bool associatedTypesAreSameEquivalenceClass(AssociatedTypeDecl *a,
AssociatedTypeDecl *b) {
if (a == b)
return true;
// TODO: Do a proper equivalence check here by looking for some relationship
// between a and b's protocols. In practice today, it's unlikely that
// two same-named associated types can currently be independent, since we
// don't have anything like `@implements(P.foo)` to rename witnesses (and
// we still fall back to name lookup for witnesses in more cases than we
// should).
if (a->getName() == b->getName())
return true;
return false;
}
InferredAssociatedTypesByWitnesses
AssociatedTypeInference::inferTypeWitnessesViaValueWitnesses(
ConformanceChecker &checker,
const llvm::SetVector<AssociatedTypeDecl *> &allUnresolved,
ValueDecl *req) {
// Conformances constructed by the ClangImporter should have explicit type
// witnesses already.
if (isa<ClangModuleUnit>(conformance->getDeclContext()->getModuleScopeContext())) {
llvm::errs() << "Cannot infer associated types for imported conformance:\n";
conformance->getType().dump(llvm::errs());
for (auto assocTypeDecl : allUnresolved)
assocTypeDecl->dump(llvm::errs());
abort();
}
InferredAssociatedTypesByWitnesses result;
auto isExtensionUsableForInference = [&](const ExtensionDecl *extension) {
// The context the conformance being checked is declared on.
const auto conformanceCtx = checker.Conformance->getDeclContext();
if (extension == conformanceCtx)
return true;
// Invalid case.
const auto extendedNominal = extension->getExtendedNominal();
if (extendedNominal == nullptr)
return true;
auto *proto = dyn_cast<ProtocolDecl>(extendedNominal);
// If the extension is bound to the nominal the conformance is
// declared on, it is viable for inference when its conditional
// requirements are satisfied by those of the conformance context.
if (!proto) {
// Retrieve the generic signature of the extension.
const auto extensionSig = extension->getGenericSignature();
return extensionSig
.requirementsNotSatisfiedBy(
conformanceCtx->getGenericSignatureOfContext())
.empty();
}
// The condition here is a bit more fickle than
// `isExtensionApplied`. That check would prematurely reject
// extensions like `P where AssocType == T` if we're relying on a
// default implementation inside the extension to infer `AssocType == T`
// in the first place. Only check conformances on the `Self` type,
// because those have to be explicitly declared on the type somewhere
// so won't be affected by whatever answer inference comes up with.
auto *module = dc->getParentModule();
auto checkConformance = [&](ProtocolDecl *proto) {
auto typeInContext = dc->mapTypeIntoContext(conformance->getType());
auto otherConf = TypeChecker::conformsToProtocol(
typeInContext, proto, module);
return !otherConf.isInvalid();
};
// First check the extended protocol itself.
if (!checkConformance(proto))
return false;
// Source file and module file have different ways to get self bounds.
// Source file extension will have trailing where clause which can avoid
// computing a generic signature. Module file will not have
// trailing where clause, so it will compute generic signature to get
// self bounds which might result in slow performance.
SelfBounds bounds;
if (extension->getParentSourceFile() != nullptr)
bounds = getSelfBoundsFromWhereClause(extension);
else
bounds = getSelfBoundsFromGenericSignature(extension);
for (auto *decl : bounds.decls) {
if (auto *proto = dyn_cast<ProtocolDecl>(decl)) {
if (!checkConformance(proto))
return false;
}
}
return true;
};
for (auto witness :
checker.lookupValueWitnesses(req, /*ignoringNames=*/nullptr)) {
LLVM_DEBUG(llvm::dbgs() << "Inferring associated types from decl:\n";
witness->dump(llvm::dbgs()));
// If the potential witness came from an extension, and our `Self`
// type can't use it regardless of what associated types we end up
// inferring, skip the witness.
if (auto extension = dyn_cast<ExtensionDecl>(witness->getDeclContext()))
if (!isExtensionUsableForInference(extension)) {
LLVM_DEBUG(llvm::dbgs() << "Extension not usable for inference\n");
continue;
}
// Try to resolve the type witness via this value witness.
auto witnessResult = inferTypeWitnessesViaValueWitness(req, witness);
// Filter out duplicated inferred types as well as inferred types
// that don't meet the requirements placed on the associated type.
llvm::DenseSet<std::pair<AssociatedTypeDecl *, CanType>> known;
for (unsigned i = 0; i < witnessResult.Inferred.size(); /*nothing*/) {
#define REJECT {\
witnessResult.Inferred.erase(witnessResult.Inferred.begin() + i); \
continue; \
}
auto &result = witnessResult.Inferred[i];
LLVM_DEBUG(llvm::dbgs() << "Considering whether "
<< result.first->getName()
<< " can infer to:\n";
result.second->dump(llvm::dbgs()));
// Filter out errors.
if (result.second->hasError()) {
LLVM_DEBUG(llvm::dbgs() << "-- has error type\n");
REJECT;
}
// Filter out duplicates.
if (!known.insert({result.first, result.second->getCanonicalType()})
.second) {
LLVM_DEBUG(llvm::dbgs() << "-- duplicate\n");
REJECT;
}
// Filter out circular possibilities, e.g. that
// AssocType == S.AssocType or
// AssocType == Foo<S.AssocType>.
bool canInferFromOtherAssociatedType = false;
bool containsTautologicalType =
result.second.findIf([&](Type t) -> bool {
auto dmt = t->getAs<DependentMemberType>();
if (!dmt)
return false;
if (!associatedTypesAreSameEquivalenceClass(dmt->getAssocType(),
result.first))
return false;
auto typeInContext =
conformance->getDeclContext()->mapTypeIntoContext(conformance->getType());
if (!dmt->getBase()->isEqual(typeInContext))
return false;
// If this associated type is same-typed to another associated type
// on `Self`, then it may still be an interesting candidate if we find
// an answer for that other type.
auto witnessContext = witness->getDeclContext();
if (witnessContext->getExtendedProtocolDecl()
&& witnessContext->getGenericSignatureOfContext()) {
auto selfTy = witnessContext->getSelfInterfaceType();
auto selfAssocTy = DependentMemberType::get(selfTy,
dmt->getAssocType());
for (auto &reqt : witnessContext->getGenericSignatureOfContext()
.getRequirements()) {
switch (reqt.getKind()) {
case RequirementKind::SameShape:
llvm_unreachable("Same-shape requirement not supported here");
case RequirementKind::Conformance:
case RequirementKind::Superclass:
case RequirementKind::Layout:
break;
case RequirementKind::SameType:
Type other;
if (reqt.getFirstType()->isEqual(selfAssocTy)) {
other = reqt.getSecondType();
} else if (reqt.getSecondType()->isEqual(selfAssocTy)) {
other = reqt.getFirstType();
} else {
break;
}
if (auto otherAssoc = other->getAs<DependentMemberType>()) {
if (otherAssoc->getBase()->isEqual(selfTy)) {
auto otherDMT = DependentMemberType::get(dmt->getBase(),
otherAssoc->getAssocType());
// We may be able to infer one associated type from the
// other.
result.second = result.second.transform([&](Type t) -> Type{
if (t->isEqual(dmt))
return otherDMT;
return t;
});
canInferFromOtherAssociatedType = true;
LLVM_DEBUG(llvm::dbgs() << "++ we can same-type to:\n";
result.second->dump(llvm::dbgs()));
return false;
}
}
break;
}
}
}
return true;
});
if (containsTautologicalType) {
LLVM_DEBUG(llvm::dbgs() << "-- tautological\n");
REJECT;
}
// Check that the type witness doesn't contradict an
// explicitly-given type witness. If it does contradict, throw out the
// witness completely.
if (!allUnresolved.count(result.first)) {
auto existingWitness =
conformance->getTypeWitness(result.first);
existingWitness = dc->mapTypeIntoContext(existingWitness);
// If the deduced type contains an irreducible
// DependentMemberType, that indicates a dependency
// on another associated type we haven't deduced,
// so we can't tell whether there's a contradiction
// yet.
auto newWitness = result.second->getCanonicalType();
if (!newWitness->hasTypeParameter() &&
!newWitness->hasDependentMember() &&
!existingWitness->isEqual(newWitness)) {
LLVM_DEBUG(llvm::dbgs() << "** contradicts explicit type witness, "
"rejecting inference from this decl\n");
goto next_witness;
}
}
// If we same-typed to another unresolved associated type, we won't
// be able to check conformances yet.
if (!canInferFromOtherAssociatedType) {
// Check that the type witness meets the
// requirements on the associated type.
if (auto failed =
checkTypeWitness(result.second, result.first, conformance)) {
witnessResult.NonViable.push_back(
std::make_tuple(result.first,result.second,failed));
LLVM_DEBUG(llvm::dbgs() << "-- doesn't fulfill requirements\n");
REJECT;
}
}
LLVM_DEBUG(llvm::dbgs() << "++ seems legit\n");
++i;
}
#undef REJECT
// If no inferred types remain, skip this witness.
if (witnessResult.Inferred.empty() && witnessResult.NonViable.empty())
continue;
// If there were any non-viable inferred associated types, don't
// infer anything from this witness.
if (!witnessResult.NonViable.empty())
witnessResult.Inferred.clear();
result.push_back(std::move(witnessResult));
next_witness:;
}
return result;
}
InferredAssociatedTypes
AssociatedTypeInference::inferTypeWitnessesViaValueWitnesses(
ConformanceChecker &checker,
const llvm::SetVector<AssociatedTypeDecl *> &assocTypes)
{
InferredAssociatedTypes result;
for (auto member : proto->getMembers()) {
auto req = dyn_cast<ValueDecl>(member);
if (!req || !req->isProtocolRequirement())
continue;
// Infer type witnesses for associated types.
if (auto assocType = dyn_cast<AssociatedTypeDecl>(req)) {
// If this is not one of the associated types we are trying to infer,
// just continue.
if (assocTypes.count(assocType) == 0)
continue;
auto reqInferred = inferTypeWitnessesViaAssociatedType(checker,
assocTypes,
assocType);
if (!reqInferred.empty())
result.push_back({req, std::move(reqInferred)});
continue;
}
// Skip operator requirements, because they match globally and
// therefore tend to cause deduction mismatches.
// FIXME: If we had some basic sanity checking of Self, we might be able to
// use these.
if (auto func = dyn_cast<FuncDecl>(req)) {
if (func->isOperator() || isa<AccessorDecl>(func))
continue;
}
// Validate the requirement.
if (req->isInvalid())
continue;
// Check whether any of the associated types we care about are
// referenced in this value requirement.
{
const auto referenced = checker.getReferencedAssociatedTypes(req);
if (llvm::find_if(referenced, [&](AssociatedTypeDecl *const assocType) {
return assocTypes.count(assocType);
}) == referenced.end())
continue;
}
// Infer associated types from the potential value witnesses for
// this requirement.
auto reqInferred =
inferTypeWitnessesViaValueWitnesses(checker, assocTypes, req);
if (reqInferred.empty())
continue;
result.push_back({req, std::move(reqInferred)});
}
return result;
}
/// Map error types back to their original types.
static Type mapErrorTypeToOriginal(Type type) {
if (auto errorType = type->getAs<ErrorType>()) {
if (auto originalType = errorType->getOriginalType())
return originalType.transform(mapErrorTypeToOriginal);
}
return type;
}
/// Produce the type when matching a witness.
static Type getWitnessTypeForMatching(NormalProtocolConformance *conformance,
ValueDecl *witness) {
if (witness->isRecursiveValidation())
return Type();
if (witness->isInvalid())
return Type();
if (!witness->getDeclContext()->isTypeContext()) {
// FIXME: Could we infer from 'Self' to make these work?
return witness->getInterfaceType();
}
// Retrieve the set of substitutions to be applied to the witness.
Type model =
conformance->getDeclContext()->mapTypeIntoContext(conformance->getType());
TypeSubstitutionMap substitutions = model->getMemberSubstitutions(witness);
Type type = witness->getInterfaceType()->getReferenceStorageReferent();
if (substitutions.empty())
return type;
// Strip off the requirements of a generic function type.
// FIXME: This doesn't actually break recursion when substitution
// looks for an inferred type witness, but it makes it far less
// common, because most of the recursion involves the requirements
// of the generic type.
if (auto genericFn = type->getAs<GenericFunctionType>()) {
type = FunctionType::get(genericFn->getParams(),
genericFn->getResult(),
genericFn->getExtInfo());
}
// Remap associated types that reference other protocols into this
// protocol.
auto proto = conformance->getProtocol();
type = type.transformRec([proto](TypeBase *type) -> llvm::Optional<Type> {
if (auto depMemTy = dyn_cast<DependentMemberType>(type)) {
if (depMemTy->getAssocType() &&
depMemTy->getAssocType()->getProtocol() != proto) {
if (auto *assocType = proto->getAssociatedType(depMemTy->getName())) {
auto origProto = depMemTy->getAssocType()->getProtocol();
if (proto->inheritsFrom(origProto))
return Type(DependentMemberType::get(depMemTy->getBase(),
assocType));
}
}
}
return llvm::None;
});
ModuleDecl *module = conformance->getDeclContext()->getParentModule();
auto resultType = type.subst(QueryTypeSubstitutionMap{substitutions},
LookUpConformanceInModule(module));
if (!resultType->hasError()) return resultType;
// Map error types with original types *back* to the original, dependent type.
return resultType.transform(mapErrorTypeToOriginal);
}
/// Remove the 'self' type from the given type, if it's a method type.
static Type removeSelfParam(ValueDecl *value, Type type) {
if (value->hasCurriedSelf()) {
return type->castTo<AnyFunctionType>()->getResult();
}
return type;
}
InferredAssociatedTypesByWitnesses
AssociatedTypeInference::inferTypeWitnessesViaAssociatedType(
ConformanceChecker &checker,
const llvm::SetVector<AssociatedTypeDecl *> &allUnresolved,
AssociatedTypeDecl *assocType) {
// Form the default name _Default_Foo.
DeclNameRef defaultName;
{
SmallString<32> defaultNameStr;
{
llvm::raw_svector_ostream out(defaultNameStr);
out << "_Default_";
out << assocType->getName().str();
}
defaultName = DeclNameRef(getASTContext().getIdentifier(defaultNameStr));
}
NLOptions subOptions = (NL_QualifiedDefault |
NL_OnlyTypes |
NL_ProtocolMembers);
// Look for types with the given default name that have appropriate
// @_implements attributes.
SmallVector<ValueDecl *, 4> lookupResults;
dc->lookupQualified(dc->getSelfNominalTypeDecl(), defaultName,
isa<ExtensionDecl>(dc)
? cast<ExtensionDecl>(dc)->getStartLoc()
: cast<NominalTypeDecl>(dc)->getStartLoc(),
subOptions, lookupResults);
InferredAssociatedTypesByWitnesses result;
for (auto decl : lookupResults) {
// We want type declarations.
auto typeDecl = dyn_cast<TypeDecl>(decl);
if (!typeDecl || isa<AssociatedTypeDecl>(typeDecl))
continue;
// We only find these within a protocol extension.
auto defaultProto = typeDecl->getDeclContext()->getSelfProtocolDecl();
if (!defaultProto)
continue;
// Determine the witness type.
Type witnessType = getWitnessTypeForMatching(conformance, typeDecl);
if (!witnessType) continue;
if (auto witnessMetaType = witnessType->getAs<AnyMetatypeType>())
witnessType = witnessMetaType->getInstanceType();
else
continue;
// Add this result.
InferredAssociatedTypesByWitness inferred;
inferred.Witness = typeDecl;
inferred.Inferred.push_back({assocType, witnessType});
result.push_back(std::move(inferred));
}
return result;
}
Type swift::adjustInferredAssociatedType(TypeAdjustment adjustment, Type type,
bool &performed) {
// If we have an optional type, adjust its wrapped type.
if (auto optionalObjectType = type->getOptionalObjectType()) {
auto newOptionalObjectType =
adjustInferredAssociatedType(adjustment, optionalObjectType, performed);
if (newOptionalObjectType.getPointer() == optionalObjectType.getPointer())
return type;
return OptionalType::get(newOptionalObjectType);
}
auto needsAdjustment = [=](FunctionType *funcType) -> bool {
if (adjustment == TypeAdjustment::NoescapeToEscaping)
return funcType->isNoEscape();
else
return !funcType->isSendable();
};
auto adjust = [=](const ASTExtInfo &info) -> ASTExtInfo {
if (adjustment == TypeAdjustment::NoescapeToEscaping)
return info.withNoEscape(false);
else
return info.withConcurrent(true);
};
// If we have a noescape function type, make it escaping.
if (auto funcType = type->getAs<FunctionType>()) {
performed = needsAdjustment(funcType);
if (performed)
return FunctionType::get(funcType->getParams(), funcType->getResult(),
adjust(funcType->getExtInfo()));
}
return type;
}
/// Attempt to resolve a type witness via a specific value witness.
InferredAssociatedTypesByWitness
AssociatedTypeInference::inferTypeWitnessesViaValueWitness(ValueDecl *req,
ValueDecl *witness) {
InferredAssociatedTypesByWitness inferred;
inferred.Witness = witness;
// Compute the requirement and witness types we'll use for matching.
Type fullWitnessType = getWitnessTypeForMatching(conformance, witness);
if (!fullWitnessType) {
return inferred;
}
auto setup =
[&]() -> std::tuple<llvm::Optional<RequirementMatch>, Type, Type> {
fullWitnessType = removeSelfParam(witness, fullWitnessType);
return std::make_tuple(llvm::None,
removeSelfParam(req, req->getInterfaceType()),
fullWitnessType);
};
/// Visits a requirement type to match it to a potential witness for
/// the purpose of deducing associated types.
///
/// The visitor argument is the witness type. If there are any
/// obvious conflicts between the structure of the two types,
/// returns true. The conflict checking is fairly conservative, only
/// considering rough structure.
class MatchVisitor : public TypeMatcher<MatchVisitor> {
NormalProtocolConformance *Conformance;
InferredAssociatedTypesByWitness &Inferred;
public:
MatchVisitor(NormalProtocolConformance *conformance,
InferredAssociatedTypesByWitness &inferred)
: Conformance(conformance), Inferred(inferred) { }
/// Structural mismatches imply that the witness cannot match.
bool mismatch(TypeBase *firstType, TypeBase *secondType,
Type sugaredFirstType) {
// If either type hit an error, don't stop yet.
if (firstType->hasError() || secondType->hasError())
return true;
// FIXME: Check whether one of the types is dependent?
return false;
}
/// Deduce associated types from dependent member types in the witness.
bool mismatch(DependentMemberType *firstDepMember,
TypeBase *secondType, Type sugaredFirstType) {
// If the second type is an error, don't look at it further.
if (secondType->hasError())
return true;
// Adjust the type to a type that can be written explicitly.
bool noescapeToEscaping = false;
Type inferredType =
adjustInferredAssociatedType(TypeAdjustment::NoescapeToEscaping,
secondType, noescapeToEscaping);
if (!inferredType->isMaterializable())
return true;
// If the type contains a type parameter, there is nothing we can infer
// from it.
// FIXME: This is a weird state introduced by associated type inference
// that should not exist.
if (inferredType->hasTypeParameter())
return true;
auto proto = Conformance->getProtocol();
if (auto assocType = getReferencedAssocTypeOfProtocol(firstDepMember,
proto)) {
Inferred.Inferred.push_back({assocType, inferredType});
}
// Always allow mismatches here.
return true;
}
/// FIXME: Recheck the type of Self against the second type?
bool mismatch(GenericTypeParamType *selfParamType,
TypeBase *secondType, Type sugaredFirstType) {
return true;
}
};
// Match a requirement and witness type.
MatchVisitor matchVisitor(conformance, inferred);
auto matchTypes = [&](Type reqType,
Type witnessType) -> llvm::Optional<RequirementMatch> {
if (!matchVisitor.match(reqType, witnessType)) {
return RequirementMatch(witness, MatchKind::TypeConflict,
fullWitnessType);
}
return llvm::None;
};
// Finalization of the checking is pretty trivial; just bundle up a
// result we can look at.
auto finalize = [&](bool anyRenaming, ArrayRef<OptionalAdjustment>)
-> RequirementMatch {
return RequirementMatch(witness,
anyRenaming ? MatchKind::RenamedMatch
: MatchKind::ExactMatch,
fullWitnessType);
};
// Match the witness. If we don't succeed, throw away the inference
// information.
// FIXME: A renamed match might be useful to retain for the failure case.
if (!matchWitness(dc, req, witness, setup, matchTypes, finalize)
.isWellFormed()) {
inferred.Inferred.clear();
}
return inferred;
}
AssociatedTypeDecl *AssociatedTypeInference::findDefaultedAssociatedType(
AssociatedTypeDecl *assocType) {
// If this associated type has a default, we're done.
if (assocType->hasDefaultDefinitionType())
return assocType;
// Look at overridden associated types.
SmallPtrSet<CanType, 4> canonicalTypes;
SmallVector<AssociatedTypeDecl *, 2> results;
for (auto overridden : assocType->getOverriddenDecls()) {
auto overriddenDefault = findDefaultedAssociatedType(overridden);
if (!overriddenDefault) continue;
Type overriddenType =
overriddenDefault->getDefaultDefinitionType();
assert(overriddenType);
if (!overriddenType) continue;
CanType key = overriddenType->getCanonicalType();
if (canonicalTypes.insert(key).second)
results.push_back(overriddenDefault);
}
// If there was a single result, return it.
// FIXME: We could find *all* of the non-covered, defaulted associated types.
return results.size() == 1 ? results.front() : nullptr;
}
Type AssociatedTypeInference::computeFixedTypeWitness(
AssociatedTypeDecl *assocType) {
Type resultType;
// Look at all of the inherited protocols to determine whether they
// require a fixed type for this associated type.
for (auto conformedProto : dc->getSelfNominalTypeDecl()->getAllProtocols()) {
if (conformedProto != assocType->getProtocol() &&
!conformedProto->inheritsFrom(assocType->getProtocol()))
continue;
auto sig = conformedProto->getGenericSignature();
// FIXME: The RequirementMachine will assert on re-entrant construction.
// We should find a more principled way of breaking this cycle.
if (ctx.isRecursivelyConstructingRequirementMachine(sig.getCanonicalSignature()) ||
ctx.isRecursivelyConstructingRequirementMachine(conformedProto) ||
conformedProto->isComputingRequirementSignature())
continue;
auto selfTy = conformedProto->getSelfInterfaceType();
if (!sig->requiresProtocol(selfTy, assocType->getProtocol()))
continue;
auto structuralTy = DependentMemberType::get(selfTy, assocType->getName());
const auto ty = sig.getReducedType(structuralTy);
// A dependent member type with an identical base and name indicates that
// the protocol does not same-type constrain it in any way; move on to
// the next protocol.
if (auto *const memberTy = ty->getAs<DependentMemberType>()) {
if (memberTy->getBase()->isEqual(selfTy) &&
memberTy->getName() == assocType->getName())
continue;
}
if (!resultType) {
resultType = ty;
continue;
}
// FIXME: Bailing out on ambiguity.
if (!resultType->isEqual(ty))
return Type();
}
return resultType;
}
llvm::Optional<AbstractTypeWitness>
AssociatedTypeInference::computeDefaultTypeWitness(
AssociatedTypeDecl *assocType) const {
// Go find a default definition.
auto *const defaultedAssocType = findDefaultedAssociatedType(assocType);
if (!defaultedAssocType)
return llvm::None;
const Type defaultType = defaultedAssocType->getDefaultDefinitionType();
// FIXME: Circularity
if (!defaultType)
return llvm::None;
if (defaultType->hasError())
return llvm::None;
return AbstractTypeWitness(assocType, defaultType, defaultedAssocType);
}
std::pair<Type, TypeDecl *>
AssociatedTypeInference::computeDerivedTypeWitness(
AssociatedTypeDecl *assocType) {
if (adoptee->hasError())
return std::make_pair(Type(), nullptr);
// Can we derive conformances for this protocol and adoptee?
NominalTypeDecl *derivingTypeDecl = dc->getSelfNominalTypeDecl();
if (!DerivedConformance::derivesProtocolConformance(dc, derivingTypeDecl,
proto))
return std::make_pair(Type(), nullptr);
// Try to derive the type witness.
auto result = TypeChecker::deriveTypeWitness(dc, derivingTypeDecl, assocType);
if (!result.first)
return std::make_pair(Type(), nullptr);
// Make sure that the derived type satisfies requirements.
if (checkTypeWitness(result.first, assocType, conformance)) {
/// FIXME: Diagnose based on this.
failedDerivedAssocType = assocType;
failedDerivedWitness = result.first;
return std::make_pair(Type(), nullptr);
}
return result;
}
llvm::Optional<AbstractTypeWitness>
AssociatedTypeInference::computeAbstractTypeWitness(
AssociatedTypeDecl *assocType) {
// We don't have a type witness for this associated type, so go
// looking for more options.
if (Type concreteType = computeFixedTypeWitness(assocType))
return AbstractTypeWitness(assocType, concreteType);
// If we can form a default type, do so.
if (const auto &typeWitness = computeDefaultTypeWitness(assocType))
return typeWitness;
// If there is a generic parameter of the named type, use that.
if (auto genericSig = dc->getGenericSignatureOfContext()) {
for (auto gp : genericSig.getInnermostGenericParams()) {
// Packs cannot witness associated type requirements.
if (gp->isParameterPack())
continue;
if (gp->getName() == assocType->getName())
return AbstractTypeWitness(assocType, gp);
}
}
return llvm::None;
}
void AssociatedTypeInference::collectAbstractTypeWitnesses(
TypeWitnessSystem &system,
ArrayRef<AssociatedTypeDecl *> unresolvedAssocTypes) const {
// First, look at all the protocols the adoptee conforms to and feed the
// same-type constraints in their requirement signatures to the system.
for (auto *const conformedProto :
dc->getSelfNominalTypeDecl()->getAllProtocols(/*sorted=*/true)) {
// FIXME: The RequirementMachine will assert on re-entrant construction.
// We should find a more principled way of breaking this cycle.
if (ctx.isRecursivelyConstructingRequirementMachine(
conformedProto->getGenericSignature().getCanonicalSignature()) ||
ctx.isRecursivelyConstructingRequirementMachine(conformedProto) ||
conformedProto->isComputingRequirementSignature())
continue;
for (const auto &req :
conformedProto->getRequirementSignature().getRequirements()) {
if (req.getKind() != RequirementKind::SameType) {
continue;
}
system.addSameTypeRequirement(req);
}
}
// If the same-type constraints weren't enough to resolve an associated type,
// look for more options.
for (auto *const assocType : unresolvedAssocTypes) {
if (system.hasResolvedTypeWitness(assocType->getName())) {
continue;
}
// If we find a default type definition, feed it to the system.
if (const auto &typeWitness = computeDefaultTypeWitness(assocType)) {
system.addDefaultTypeWitness(typeWitness->getType(),
typeWitness->getDefaultedAssocType());
} else {
// As a last resort, look for a generic parameter that matches the name
// of the associated type.
if (auto genericSig = dc->getGenericSignatureOfContext()) {
for (auto *gp : genericSig.getInnermostGenericParams()) {
if (gp->getName() == assocType->getName()) {
system.addTypeWitness(assocType->getName(), gp);
}
}
}
}
}
}
Type AssociatedTypeInference::substCurrentTypeWitnesses(Type type) {
// Local function that folds dependent member types with non-dependent
// bases into actual member references.
std::function<Type(Type)> foldDependentMemberTypes;
llvm::DenseSet<AssociatedTypeDecl *> recursionCheck;
foldDependentMemberTypes = [&](Type type) -> Type {
if (auto depMemTy = type->getAs<DependentMemberType>()) {
auto baseTy = depMemTy->getBase().transform(foldDependentMemberTypes);
if (baseTy.isNull() || baseTy->hasTypeParameter())
return nullptr;