1 //===--- SemaDeclObjC.cpp - Semantic Analysis for ObjC Declarations -------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 //  This file implements semantic analysis for Objective C declarations.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "TypeLocBuilder.h"
15 #include "clang/AST/ASTConsumer.h"
16 #include "clang/AST/ASTContext.h"
17 #include "clang/AST/ASTMutationListener.h"
18 #include "clang/AST/DeclObjC.h"
19 #include "clang/AST/Expr.h"
20 #include "clang/AST/ExprObjC.h"
21 #include "clang/AST/RecursiveASTVisitor.h"
22 #include "clang/Basic/SourceManager.h"
23 #include "clang/Sema/DeclSpec.h"
24 #include "clang/Sema/Lookup.h"
25 #include "clang/Sema/Scope.h"
26 #include "clang/Sema/ScopeInfo.h"
27 #include "clang/Sema/SemaInternal.h"
28 #include "llvm/ADT/DenseMap.h"
29 #include "llvm/ADT/DenseSet.h"
30 
31 using namespace clang;
32 
33 /// Check whether the given method, which must be in the 'init'
34 /// family, is a valid member of that family.
35 ///
36 /// \param receiverTypeIfCall - if null, check this as if declaring it;
37 ///   if non-null, check this as if making a call to it with the given
38 ///   receiver type
39 ///
40 /// \return true to indicate that there was an error and appropriate
41 ///   actions were taken
42 bool Sema::checkInitMethod(ObjCMethodDecl *method,
43                            QualType receiverTypeIfCall) {
44   if (method->isInvalidDecl()) return true;
45 
46   // This castAs is safe: methods that don't return an object
47   // pointer won't be inferred as inits and will reject an explicit
48   // objc_method_family(init).
49 
50   // We ignore protocols here.  Should we?  What about Class?
51 
52   const ObjCObjectType *result =
53       method->getReturnType()->castAs<ObjCObjectPointerType>()->getObjectType();
54 
55   if (result->isObjCId()) {
56     return false;
57   } else if (result->isObjCClass()) {
58     // fall through: always an error
59   } else {
60     ObjCInterfaceDecl *resultClass = result->getInterface();
61     assert(resultClass && "unexpected object type!");
62 
63     // It's okay for the result type to still be a forward declaration
64     // if we're checking an interface declaration.
65     if (!resultClass->hasDefinition()) {
66       if (receiverTypeIfCall.isNull() &&
67           !isa<ObjCImplementationDecl>(method->getDeclContext()))
68         return false;
69 
70     // Otherwise, we try to compare class types.
71     } else {
72       // If this method was declared in a protocol, we can't check
73       // anything unless we have a receiver type that's an interface.
74       const ObjCInterfaceDecl *receiverClass = nullptr;
75       if (isa<ObjCProtocolDecl>(method->getDeclContext())) {
76         if (receiverTypeIfCall.isNull())
77           return false;
78 
79         receiverClass = receiverTypeIfCall->castAs<ObjCObjectPointerType>()
80           ->getInterfaceDecl();
81 
82         // This can be null for calls to e.g. id<Foo>.
83         if (!receiverClass) return false;
84       } else {
85         receiverClass = method->getClassInterface();
86         assert(receiverClass && "method not associated with a class!");
87       }
88 
89       // If either class is a subclass of the other, it's fine.
90       if (receiverClass->isSuperClassOf(resultClass) ||
91           resultClass->isSuperClassOf(receiverClass))
92         return false;
93     }
94   }
95 
96   SourceLocation loc = method->getLocation();
97 
98   // If we're in a system header, and this is not a call, just make
99   // the method unusable.
100   if (receiverTypeIfCall.isNull() && getSourceManager().isInSystemHeader(loc)) {
101     method->addAttr(UnavailableAttr::CreateImplicit(Context, "",
102                       UnavailableAttr::IR_ARCInitReturnsUnrelated, loc));
103     return true;
104   }
105 
106   // Otherwise, it's an error.
107   Diag(loc, diag::err_arc_init_method_unrelated_result_type);
108   method->setInvalidDecl();
109   return true;
110 }
111 
112 void Sema::CheckObjCMethodOverride(ObjCMethodDecl *NewMethod,
113                                    const ObjCMethodDecl *Overridden) {
114   if (Overridden->hasRelatedResultType() &&
115       !NewMethod->hasRelatedResultType()) {
116     // This can only happen when the method follows a naming convention that
117     // implies a related result type, and the original (overridden) method has
118     // a suitable return type, but the new (overriding) method does not have
119     // a suitable return type.
120     QualType ResultType = NewMethod->getReturnType();
121     SourceRange ResultTypeRange = NewMethod->getReturnTypeSourceRange();
122 
123     // Figure out which class this method is part of, if any.
124     ObjCInterfaceDecl *CurrentClass
125       = dyn_cast<ObjCInterfaceDecl>(NewMethod->getDeclContext());
126     if (!CurrentClass) {
127       DeclContext *DC = NewMethod->getDeclContext();
128       if (ObjCCategoryDecl *Cat = dyn_cast<ObjCCategoryDecl>(DC))
129         CurrentClass = Cat->getClassInterface();
130       else if (ObjCImplDecl *Impl = dyn_cast<ObjCImplDecl>(DC))
131         CurrentClass = Impl->getClassInterface();
132       else if (ObjCCategoryImplDecl *CatImpl
133                = dyn_cast<ObjCCategoryImplDecl>(DC))
134         CurrentClass = CatImpl->getClassInterface();
135     }
136 
137     if (CurrentClass) {
138       Diag(NewMethod->getLocation(),
139            diag::warn_related_result_type_compatibility_class)
140         << Context.getObjCInterfaceType(CurrentClass)
141         << ResultType
142         << ResultTypeRange;
143     } else {
144       Diag(NewMethod->getLocation(),
145            diag::warn_related_result_type_compatibility_protocol)
146         << ResultType
147         << ResultTypeRange;
148     }
149 
150     if (ObjCMethodFamily Family = Overridden->getMethodFamily())
151       Diag(Overridden->getLocation(),
152            diag::note_related_result_type_family)
153         << /*overridden method*/ 0
154         << Family;
155     else
156       Diag(Overridden->getLocation(),
157            diag::note_related_result_type_overridden);
158   }
159 
160   if ((NewMethod->hasAttr<NSReturnsRetainedAttr>() !=
161        Overridden->hasAttr<NSReturnsRetainedAttr>())) {
162     Diag(NewMethod->getLocation(),
163          getLangOpts().ObjCAutoRefCount
164              ? diag::err_nsreturns_retained_attribute_mismatch
165              : diag::warn_nsreturns_retained_attribute_mismatch)
166         << 1;
167     Diag(Overridden->getLocation(), diag::note_previous_decl) << "method";
168   }
169   if ((NewMethod->hasAttr<NSReturnsNotRetainedAttr>() !=
170        Overridden->hasAttr<NSReturnsNotRetainedAttr>())) {
171     Diag(NewMethod->getLocation(),
172          getLangOpts().ObjCAutoRefCount
173              ? diag::err_nsreturns_retained_attribute_mismatch
174              : diag::warn_nsreturns_retained_attribute_mismatch)
175         << 0;
176     Diag(Overridden->getLocation(), diag::note_previous_decl)  << "method";
177   }
178 
179   ObjCMethodDecl::param_const_iterator oi = Overridden->param_begin(),
180                                        oe = Overridden->param_end();
181   for (ObjCMethodDecl::param_iterator ni = NewMethod->param_begin(),
182                                       ne = NewMethod->param_end();
183        ni != ne && oi != oe; ++ni, ++oi) {
184     const ParmVarDecl *oldDecl = (*oi);
185     ParmVarDecl *newDecl = (*ni);
186     if (newDecl->hasAttr<NSConsumedAttr>() !=
187         oldDecl->hasAttr<NSConsumedAttr>()) {
188       Diag(newDecl->getLocation(),
189            getLangOpts().ObjCAutoRefCount
190                ? diag::err_nsconsumed_attribute_mismatch
191                : diag::warn_nsconsumed_attribute_mismatch);
192       Diag(oldDecl->getLocation(), diag::note_previous_decl) << "parameter";
193     }
194 
195     // A parameter of the overriding method should be annotated with noescape
196     // if the corresponding parameter of the overridden method is annotated.
197     if (oldDecl->hasAttr<NoEscapeAttr>() && !newDecl->hasAttr<NoEscapeAttr>()) {
198       Diag(newDecl->getLocation(),
199            diag::warn_overriding_method_missing_noescape);
200       Diag(oldDecl->getLocation(), diag::note_overridden_marked_noescape);
201     }
202   }
203 }
204 
205 /// \brief Check a method declaration for compatibility with the Objective-C
206 /// ARC conventions.
207 bool Sema::CheckARCMethodDecl(ObjCMethodDecl *method) {
208   ObjCMethodFamily family = method->getMethodFamily();
209   switch (family) {
210   case OMF_None:
211   case OMF_finalize:
212   case OMF_retain:
213   case OMF_release:
214   case OMF_autorelease:
215   case OMF_retainCount:
216   case OMF_self:
217   case OMF_initialize:
218   case OMF_performSelector:
219     return false;
220 
221   case OMF_dealloc:
222     if (!Context.hasSameType(method->getReturnType(), Context.VoidTy)) {
223       SourceRange ResultTypeRange = method->getReturnTypeSourceRange();
224       if (ResultTypeRange.isInvalid())
225         Diag(method->getLocation(), diag::err_dealloc_bad_result_type)
226             << method->getReturnType()
227             << FixItHint::CreateInsertion(method->getSelectorLoc(0), "(void)");
228       else
229         Diag(method->getLocation(), diag::err_dealloc_bad_result_type)
230             << method->getReturnType()
231             << FixItHint::CreateReplacement(ResultTypeRange, "void");
232       return true;
233     }
234     return false;
235 
236   case OMF_init:
237     // If the method doesn't obey the init rules, don't bother annotating it.
238     if (checkInitMethod(method, QualType()))
239       return true;
240 
241     method->addAttr(NSConsumesSelfAttr::CreateImplicit(Context));
242 
243     // Don't add a second copy of this attribute, but otherwise don't
244     // let it be suppressed.
245     if (method->hasAttr<NSReturnsRetainedAttr>())
246       return false;
247     break;
248 
249   case OMF_alloc:
250   case OMF_copy:
251   case OMF_mutableCopy:
252   case OMF_new:
253     if (method->hasAttr<NSReturnsRetainedAttr>() ||
254         method->hasAttr<NSReturnsNotRetainedAttr>() ||
255         method->hasAttr<NSReturnsAutoreleasedAttr>())
256       return false;
257     break;
258   }
259 
260   method->addAttr(NSReturnsRetainedAttr::CreateImplicit(Context));
261   return false;
262 }
263 
264 static void DiagnoseObjCImplementedDeprecations(Sema &S, const NamedDecl *ND,
265                                                 SourceLocation ImplLoc) {
266   if (!ND)
267     return;
268   bool IsCategory = false;
269   AvailabilityResult Availability = ND->getAvailability();
270   if (Availability != AR_Deprecated) {
271     if (isa<ObjCMethodDecl>(ND)) {
272       if (Availability != AR_Unavailable)
273         return;
274       // Warn about implementing unavailable methods.
275       S.Diag(ImplLoc, diag::warn_unavailable_def);
276       S.Diag(ND->getLocation(), diag::note_method_declared_at)
277           << ND->getDeclName();
278       return;
279     }
280     if (const auto *CD = dyn_cast<ObjCCategoryDecl>(ND)) {
281       if (!CD->getClassInterface()->isDeprecated())
282         return;
283       ND = CD->getClassInterface();
284       IsCategory = true;
285     } else
286       return;
287   }
288   S.Diag(ImplLoc, diag::warn_deprecated_def)
289       << (isa<ObjCMethodDecl>(ND)
290               ? /*Method*/ 0
291               : isa<ObjCCategoryDecl>(ND) || IsCategory ? /*Category*/ 2
292                                                         : /*Class*/ 1);
293   if (isa<ObjCMethodDecl>(ND))
294     S.Diag(ND->getLocation(), diag::note_method_declared_at)
295         << ND->getDeclName();
296   else
297     S.Diag(ND->getLocation(), diag::note_previous_decl)
298         << (isa<ObjCCategoryDecl>(ND) ? "category" : "class");
299 }
300 
301 /// AddAnyMethodToGlobalPool - Add any method, instance or factory to global
302 /// pool.
303 void Sema::AddAnyMethodToGlobalPool(Decl *D) {
304   ObjCMethodDecl *MDecl = dyn_cast_or_null<ObjCMethodDecl>(D);
305 
306   // If we don't have a valid method decl, simply return.
307   if (!MDecl)
308     return;
309   if (MDecl->isInstanceMethod())
310     AddInstanceMethodToGlobalPool(MDecl, true);
311   else
312     AddFactoryMethodToGlobalPool(MDecl, true);
313 }
314 
315 /// HasExplicitOwnershipAttr - returns true when pointer to ObjC pointer
316 /// has explicit ownership attribute; false otherwise.
317 static bool
318 HasExplicitOwnershipAttr(Sema &S, ParmVarDecl *Param) {
319   QualType T = Param->getType();
320 
321   if (const PointerType *PT = T->getAs<PointerType>()) {
322     T = PT->getPointeeType();
323   } else if (const ReferenceType *RT = T->getAs<ReferenceType>()) {
324     T = RT->getPointeeType();
325   } else {
326     return true;
327   }
328 
329   // If we have a lifetime qualifier, but it's local, we must have
330   // inferred it. So, it is implicit.
331   return !T.getLocalQualifiers().hasObjCLifetime();
332 }
333 
334 /// ActOnStartOfObjCMethodDef - This routine sets up parameters; invisible
335 /// and user declared, in the method definition's AST.
336 void Sema::ActOnStartOfObjCMethodDef(Scope *FnBodyScope, Decl *D) {
337   assert((getCurMethodDecl() == nullptr) && "Methodparsing confused");
338   ObjCMethodDecl *MDecl = dyn_cast_or_null<ObjCMethodDecl>(D);
339 
340   // If we don't have a valid method decl, simply return.
341   if (!MDecl)
342     return;
343 
344   // Allow all of Sema to see that we are entering a method definition.
345   PushDeclContext(FnBodyScope, MDecl);
346   PushFunctionScope();
347 
348   // Create Decl objects for each parameter, entrring them in the scope for
349   // binding to their use.
350 
351   // Insert the invisible arguments, self and _cmd!
352   MDecl->createImplicitParams(Context, MDecl->getClassInterface());
353 
354   PushOnScopeChains(MDecl->getSelfDecl(), FnBodyScope);
355   PushOnScopeChains(MDecl->getCmdDecl(), FnBodyScope);
356 
357   // The ObjC parser requires parameter names so there's no need to check.
358   CheckParmsForFunctionDef(MDecl->parameters(),
359                            /*CheckParameterNames=*/false);
360 
361   // Introduce all of the other parameters into this scope.
362   for (auto *Param : MDecl->parameters()) {
363     if (!Param->isInvalidDecl() &&
364         getLangOpts().ObjCAutoRefCount &&
365         !HasExplicitOwnershipAttr(*this, Param))
366       Diag(Param->getLocation(), diag::warn_arc_strong_pointer_objc_pointer) <<
367             Param->getType();
368 
369     if (Param->getIdentifier())
370       PushOnScopeChains(Param, FnBodyScope);
371   }
372 
373   // In ARC, disallow definition of retain/release/autorelease/retainCount
374   if (getLangOpts().ObjCAutoRefCount) {
375     switch (MDecl->getMethodFamily()) {
376     case OMF_retain:
377     case OMF_retainCount:
378     case OMF_release:
379     case OMF_autorelease:
380       Diag(MDecl->getLocation(), diag::err_arc_illegal_method_def)
381         << 0 << MDecl->getSelector();
382       break;
383 
384     case OMF_None:
385     case OMF_dealloc:
386     case OMF_finalize:
387     case OMF_alloc:
388     case OMF_init:
389     case OMF_mutableCopy:
390     case OMF_copy:
391     case OMF_new:
392     case OMF_self:
393     case OMF_initialize:
394     case OMF_performSelector:
395       break;
396     }
397   }
398 
399   // Warn on deprecated methods under -Wdeprecated-implementations,
400   // and prepare for warning on missing super calls.
401   if (ObjCInterfaceDecl *IC = MDecl->getClassInterface()) {
402     ObjCMethodDecl *IMD =
403       IC->lookupMethod(MDecl->getSelector(), MDecl->isInstanceMethod());
404 
405     if (IMD) {
406       ObjCImplDecl *ImplDeclOfMethodDef =
407         dyn_cast<ObjCImplDecl>(MDecl->getDeclContext());
408       ObjCContainerDecl *ContDeclOfMethodDecl =
409         dyn_cast<ObjCContainerDecl>(IMD->getDeclContext());
410       ObjCImplDecl *ImplDeclOfMethodDecl = nullptr;
411       if (ObjCInterfaceDecl *OID = dyn_cast<ObjCInterfaceDecl>(ContDeclOfMethodDecl))
412         ImplDeclOfMethodDecl = OID->getImplementation();
413       else if (ObjCCategoryDecl *CD = dyn_cast<ObjCCategoryDecl>(ContDeclOfMethodDecl)) {
414         if (CD->IsClassExtension()) {
415           if (ObjCInterfaceDecl *OID = CD->getClassInterface())
416             ImplDeclOfMethodDecl = OID->getImplementation();
417         } else
418             ImplDeclOfMethodDecl = CD->getImplementation();
419       }
420       // No need to issue deprecated warning if deprecated mehod in class/category
421       // is being implemented in its own implementation (no overriding is involved).
422       if (!ImplDeclOfMethodDecl || ImplDeclOfMethodDecl != ImplDeclOfMethodDef)
423         DiagnoseObjCImplementedDeprecations(*this, IMD, MDecl->getLocation());
424     }
425 
426     if (MDecl->getMethodFamily() == OMF_init) {
427       if (MDecl->isDesignatedInitializerForTheInterface()) {
428         getCurFunction()->ObjCIsDesignatedInit = true;
429         getCurFunction()->ObjCWarnForNoDesignatedInitChain =
430             IC->getSuperClass() != nullptr;
431       } else if (IC->hasDesignatedInitializers()) {
432         getCurFunction()->ObjCIsSecondaryInit = true;
433         getCurFunction()->ObjCWarnForNoInitDelegation = true;
434       }
435     }
436 
437     // If this is "dealloc" or "finalize", set some bit here.
438     // Then in ActOnSuperMessage() (SemaExprObjC), set it back to false.
439     // Finally, in ActOnFinishFunctionBody() (SemaDecl), warn if flag is set.
440     // Only do this if the current class actually has a superclass.
441     if (const ObjCInterfaceDecl *SuperClass = IC->getSuperClass()) {
442       ObjCMethodFamily Family = MDecl->getMethodFamily();
443       if (Family == OMF_dealloc) {
444         if (!(getLangOpts().ObjCAutoRefCount ||
445               getLangOpts().getGC() == LangOptions::GCOnly))
446           getCurFunction()->ObjCShouldCallSuper = true;
447 
448       } else if (Family == OMF_finalize) {
449         if (Context.getLangOpts().getGC() != LangOptions::NonGC)
450           getCurFunction()->ObjCShouldCallSuper = true;
451 
452       } else {
453         const ObjCMethodDecl *SuperMethod =
454           SuperClass->lookupMethod(MDecl->getSelector(),
455                                    MDecl->isInstanceMethod());
456         getCurFunction()->ObjCShouldCallSuper =
457           (SuperMethod && SuperMethod->hasAttr<ObjCRequiresSuperAttr>());
458       }
459     }
460   }
461 }
462 
463 namespace {
464 
465 // Callback to only accept typo corrections that are Objective-C classes.
466 // If an ObjCInterfaceDecl* is given to the constructor, then the validation
467 // function will reject corrections to that class.
468 class ObjCInterfaceValidatorCCC : public CorrectionCandidateCallback {
469  public:
470   ObjCInterfaceValidatorCCC() : CurrentIDecl(nullptr) {}
471   explicit ObjCInterfaceValidatorCCC(ObjCInterfaceDecl *IDecl)
472       : CurrentIDecl(IDecl) {}
473 
474   bool ValidateCandidate(const TypoCorrection &candidate) override {
475     ObjCInterfaceDecl *ID = candidate.getCorrectionDeclAs<ObjCInterfaceDecl>();
476     return ID && !declaresSameEntity(ID, CurrentIDecl);
477   }
478 
479  private:
480   ObjCInterfaceDecl *CurrentIDecl;
481 };
482 
483 } // end anonymous namespace
484 
485 static void diagnoseUseOfProtocols(Sema &TheSema,
486                                    ObjCContainerDecl *CD,
487                                    ObjCProtocolDecl *const *ProtoRefs,
488                                    unsigned NumProtoRefs,
489                                    const SourceLocation *ProtoLocs) {
490   assert(ProtoRefs);
491   // Diagnose availability in the context of the ObjC container.
492   Sema::ContextRAII SavedContext(TheSema, CD);
493   for (unsigned i = 0; i < NumProtoRefs; ++i) {
494     (void)TheSema.DiagnoseUseOfDecl(ProtoRefs[i], ProtoLocs[i],
495                                     /*UnknownObjCClass=*/nullptr,
496                                     /*ObjCPropertyAccess=*/false,
497                                     /*AvoidPartialAvailabilityChecks=*/true);
498   }
499 }
500 
501 void Sema::
502 ActOnSuperClassOfClassInterface(Scope *S,
503                                 SourceLocation AtInterfaceLoc,
504                                 ObjCInterfaceDecl *IDecl,
505                                 IdentifierInfo *ClassName,
506                                 SourceLocation ClassLoc,
507                                 IdentifierInfo *SuperName,
508                                 SourceLocation SuperLoc,
509                                 ArrayRef<ParsedType> SuperTypeArgs,
510                                 SourceRange SuperTypeArgsRange) {
511   // Check if a different kind of symbol declared in this scope.
512   NamedDecl *PrevDecl = LookupSingleName(TUScope, SuperName, SuperLoc,
513                                          LookupOrdinaryName);
514 
515   if (!PrevDecl) {
516     // Try to correct for a typo in the superclass name without correcting
517     // to the class we're defining.
518     if (TypoCorrection Corrected = CorrectTypo(
519             DeclarationNameInfo(SuperName, SuperLoc),
520             LookupOrdinaryName, TUScope,
521             nullptr, llvm::make_unique<ObjCInterfaceValidatorCCC>(IDecl),
522             CTK_ErrorRecovery)) {
523       diagnoseTypo(Corrected, PDiag(diag::err_undef_superclass_suggest)
524                    << SuperName << ClassName);
525       PrevDecl = Corrected.getCorrectionDeclAs<ObjCInterfaceDecl>();
526     }
527   }
528 
529   if (declaresSameEntity(PrevDecl, IDecl)) {
530     Diag(SuperLoc, diag::err_recursive_superclass)
531       << SuperName << ClassName << SourceRange(AtInterfaceLoc, ClassLoc);
532     IDecl->setEndOfDefinitionLoc(ClassLoc);
533   } else {
534     ObjCInterfaceDecl *SuperClassDecl =
535     dyn_cast_or_null<ObjCInterfaceDecl>(PrevDecl);
536     QualType SuperClassType;
537 
538     // Diagnose classes that inherit from deprecated classes.
539     if (SuperClassDecl) {
540       (void)DiagnoseUseOfDecl(SuperClassDecl, SuperLoc);
541       SuperClassType = Context.getObjCInterfaceType(SuperClassDecl);
542     }
543 
544     if (PrevDecl && !SuperClassDecl) {
545       // The previous declaration was not a class decl. Check if we have a
546       // typedef. If we do, get the underlying class type.
547       if (const TypedefNameDecl *TDecl =
548           dyn_cast_or_null<TypedefNameDecl>(PrevDecl)) {
549         QualType T = TDecl->getUnderlyingType();
550         if (T->isObjCObjectType()) {
551           if (NamedDecl *IDecl = T->getAs<ObjCObjectType>()->getInterface()) {
552             SuperClassDecl = dyn_cast<ObjCInterfaceDecl>(IDecl);
553             SuperClassType = Context.getTypeDeclType(TDecl);
554 
555             // This handles the following case:
556             // @interface NewI @end
557             // typedef NewI DeprI __attribute__((deprecated("blah")))
558             // @interface SI : DeprI /* warn here */ @end
559             (void)DiagnoseUseOfDecl(const_cast<TypedefNameDecl*>(TDecl), SuperLoc);
560           }
561         }
562       }
563 
564       // This handles the following case:
565       //
566       // typedef int SuperClass;
567       // @interface MyClass : SuperClass {} @end
568       //
569       if (!SuperClassDecl) {
570         Diag(SuperLoc, diag::err_redefinition_different_kind) << SuperName;
571         Diag(PrevDecl->getLocation(), diag::note_previous_definition);
572       }
573     }
574 
575     if (!dyn_cast_or_null<TypedefNameDecl>(PrevDecl)) {
576       if (!SuperClassDecl)
577         Diag(SuperLoc, diag::err_undef_superclass)
578           << SuperName << ClassName << SourceRange(AtInterfaceLoc, ClassLoc);
579       else if (RequireCompleteType(SuperLoc,
580                                    SuperClassType,
581                                    diag::err_forward_superclass,
582                                    SuperClassDecl->getDeclName(),
583                                    ClassName,
584                                    SourceRange(AtInterfaceLoc, ClassLoc))) {
585         SuperClassDecl = nullptr;
586         SuperClassType = QualType();
587       }
588     }
589 
590     if (SuperClassType.isNull()) {
591       assert(!SuperClassDecl && "Failed to set SuperClassType?");
592       return;
593     }
594 
595     // Handle type arguments on the superclass.
596     TypeSourceInfo *SuperClassTInfo = nullptr;
597     if (!SuperTypeArgs.empty()) {
598       TypeResult fullSuperClassType = actOnObjCTypeArgsAndProtocolQualifiers(
599                                         S,
600                                         SuperLoc,
601                                         CreateParsedType(SuperClassType,
602                                                          nullptr),
603                                         SuperTypeArgsRange.getBegin(),
604                                         SuperTypeArgs,
605                                         SuperTypeArgsRange.getEnd(),
606                                         SourceLocation(),
607                                         { },
608                                         { },
609                                         SourceLocation());
610       if (!fullSuperClassType.isUsable())
611         return;
612 
613       SuperClassType = GetTypeFromParser(fullSuperClassType.get(),
614                                          &SuperClassTInfo);
615     }
616 
617     if (!SuperClassTInfo) {
618       SuperClassTInfo = Context.getTrivialTypeSourceInfo(SuperClassType,
619                                                          SuperLoc);
620     }
621 
622     IDecl->setSuperClass(SuperClassTInfo);
623     IDecl->setEndOfDefinitionLoc(SuperClassTInfo->getTypeLoc().getLocEnd());
624   }
625 }
626 
627 DeclResult Sema::actOnObjCTypeParam(Scope *S,
628                                     ObjCTypeParamVariance variance,
629                                     SourceLocation varianceLoc,
630                                     unsigned index,
631                                     IdentifierInfo *paramName,
632                                     SourceLocation paramLoc,
633                                     SourceLocation colonLoc,
634                                     ParsedType parsedTypeBound) {
635   // If there was an explicitly-provided type bound, check it.
636   TypeSourceInfo *typeBoundInfo = nullptr;
637   if (parsedTypeBound) {
638     // The type bound can be any Objective-C pointer type.
639     QualType typeBound = GetTypeFromParser(parsedTypeBound, &typeBoundInfo);
640     if (typeBound->isObjCObjectPointerType()) {
641       // okay
642     } else if (typeBound->isObjCObjectType()) {
643       // The user forgot the * on an Objective-C pointer type, e.g.,
644       // "T : NSView".
645       SourceLocation starLoc = getLocForEndOfToken(
646                                  typeBoundInfo->getTypeLoc().getEndLoc());
647       Diag(typeBoundInfo->getTypeLoc().getBeginLoc(),
648            diag::err_objc_type_param_bound_missing_pointer)
649         << typeBound << paramName
650         << FixItHint::CreateInsertion(starLoc, " *");
651 
652       // Create a new type location builder so we can update the type
653       // location information we have.
654       TypeLocBuilder builder;
655       builder.pushFullCopy(typeBoundInfo->getTypeLoc());
656 
657       // Create the Objective-C pointer type.
658       typeBound = Context.getObjCObjectPointerType(typeBound);
659       ObjCObjectPointerTypeLoc newT
660         = builder.push<ObjCObjectPointerTypeLoc>(typeBound);
661       newT.setStarLoc(starLoc);
662 
663       // Form the new type source information.
664       typeBoundInfo = builder.getTypeSourceInfo(Context, typeBound);
665     } else {
666       // Not a valid type bound.
667       Diag(typeBoundInfo->getTypeLoc().getBeginLoc(),
668            diag::err_objc_type_param_bound_nonobject)
669         << typeBound << paramName;
670 
671       // Forget the bound; we'll default to id later.
672       typeBoundInfo = nullptr;
673     }
674 
675     // Type bounds cannot have qualifiers (even indirectly) or explicit
676     // nullability.
677     if (typeBoundInfo) {
678       QualType typeBound = typeBoundInfo->getType();
679       TypeLoc qual = typeBoundInfo->getTypeLoc().findExplicitQualifierLoc();
680       if (qual || typeBound.hasQualifiers()) {
681         bool diagnosed = false;
682         SourceRange rangeToRemove;
683         if (qual) {
684           if (auto attr = qual.getAs<AttributedTypeLoc>()) {
685             rangeToRemove = attr.getLocalSourceRange();
686             if (attr.getTypePtr()->getImmediateNullability()) {
687               Diag(attr.getLocStart(),
688                    diag::err_objc_type_param_bound_explicit_nullability)
689                 << paramName << typeBound
690                 << FixItHint::CreateRemoval(rangeToRemove);
691               diagnosed = true;
692             }
693           }
694         }
695 
696         if (!diagnosed) {
697           Diag(qual ? qual.getLocStart()
698                     : typeBoundInfo->getTypeLoc().getLocStart(),
699               diag::err_objc_type_param_bound_qualified)
700             << paramName << typeBound << typeBound.getQualifiers().getAsString()
701             << FixItHint::CreateRemoval(rangeToRemove);
702         }
703 
704         // If the type bound has qualifiers other than CVR, we need to strip
705         // them or we'll probably assert later when trying to apply new
706         // qualifiers.
707         Qualifiers quals = typeBound.getQualifiers();
708         quals.removeCVRQualifiers();
709         if (!quals.empty()) {
710           typeBoundInfo =
711              Context.getTrivialTypeSourceInfo(typeBound.getUnqualifiedType());
712         }
713       }
714     }
715   }
716 
717   // If there was no explicit type bound (or we removed it due to an error),
718   // use 'id' instead.
719   if (!typeBoundInfo) {
720     colonLoc = SourceLocation();
721     typeBoundInfo = Context.getTrivialTypeSourceInfo(Context.getObjCIdType());
722   }
723 
724   // Create the type parameter.
725   return ObjCTypeParamDecl::Create(Context, CurContext, variance, varianceLoc,
726                                    index, paramLoc, paramName, colonLoc,
727                                    typeBoundInfo);
728 }
729 
730 ObjCTypeParamList *Sema::actOnObjCTypeParamList(Scope *S,
731                                                 SourceLocation lAngleLoc,
732                                                 ArrayRef<Decl *> typeParamsIn,
733                                                 SourceLocation rAngleLoc) {
734   // We know that the array only contains Objective-C type parameters.
735   ArrayRef<ObjCTypeParamDecl *>
736     typeParams(
737       reinterpret_cast<ObjCTypeParamDecl * const *>(typeParamsIn.data()),
738       typeParamsIn.size());
739 
740   // Diagnose redeclarations of type parameters.
741   // We do this now because Objective-C type parameters aren't pushed into
742   // scope until later (after the instance variable block), but we want the
743   // diagnostics to occur right after we parse the type parameter list.
744   llvm::SmallDenseMap<IdentifierInfo *, ObjCTypeParamDecl *> knownParams;
745   for (auto typeParam : typeParams) {
746     auto known = knownParams.find(typeParam->getIdentifier());
747     if (known != knownParams.end()) {
748       Diag(typeParam->getLocation(), diag::err_objc_type_param_redecl)
749         << typeParam->getIdentifier()
750         << SourceRange(known->second->getLocation());
751 
752       typeParam->setInvalidDecl();
753     } else {
754       knownParams.insert(std::make_pair(typeParam->getIdentifier(), typeParam));
755 
756       // Push the type parameter into scope.
757       PushOnScopeChains(typeParam, S, /*AddToContext=*/false);
758     }
759   }
760 
761   // Create the parameter list.
762   return ObjCTypeParamList::create(Context, lAngleLoc, typeParams, rAngleLoc);
763 }
764 
765 void Sema::popObjCTypeParamList(Scope *S, ObjCTypeParamList *typeParamList) {
766   for (auto typeParam : *typeParamList) {
767     if (!typeParam->isInvalidDecl()) {
768       S->RemoveDecl(typeParam);
769       IdResolver.RemoveDecl(typeParam);
770     }
771   }
772 }
773 
774 namespace {
775   /// The context in which an Objective-C type parameter list occurs, for use
776   /// in diagnostics.
777   enum class TypeParamListContext {
778     ForwardDeclaration,
779     Definition,
780     Category,
781     Extension
782   };
783 } // end anonymous namespace
784 
785 /// Check consistency between two Objective-C type parameter lists, e.g.,
786 /// between a category/extension and an \@interface or between an \@class and an
787 /// \@interface.
788 static bool checkTypeParamListConsistency(Sema &S,
789                                           ObjCTypeParamList *prevTypeParams,
790                                           ObjCTypeParamList *newTypeParams,
791                                           TypeParamListContext newContext) {
792   // If the sizes don't match, complain about that.
793   if (prevTypeParams->size() != newTypeParams->size()) {
794     SourceLocation diagLoc;
795     if (newTypeParams->size() > prevTypeParams->size()) {
796       diagLoc = newTypeParams->begin()[prevTypeParams->size()]->getLocation();
797     } else {
798       diagLoc = S.getLocForEndOfToken(newTypeParams->back()->getLocEnd());
799     }
800 
801     S.Diag(diagLoc, diag::err_objc_type_param_arity_mismatch)
802       << static_cast<unsigned>(newContext)
803       << (newTypeParams->size() > prevTypeParams->size())
804       << prevTypeParams->size()
805       << newTypeParams->size();
806 
807     return true;
808   }
809 
810   // Match up the type parameters.
811   for (unsigned i = 0, n = prevTypeParams->size(); i != n; ++i) {
812     ObjCTypeParamDecl *prevTypeParam = prevTypeParams->begin()[i];
813     ObjCTypeParamDecl *newTypeParam = newTypeParams->begin()[i];
814 
815     // Check for consistency of the variance.
816     if (newTypeParam->getVariance() != prevTypeParam->getVariance()) {
817       if (newTypeParam->getVariance() == ObjCTypeParamVariance::Invariant &&
818           newContext != TypeParamListContext::Definition) {
819         // When the new type parameter is invariant and is not part
820         // of the definition, just propagate the variance.
821         newTypeParam->setVariance(prevTypeParam->getVariance());
822       } else if (prevTypeParam->getVariance()
823                    == ObjCTypeParamVariance::Invariant &&
824                  !(isa<ObjCInterfaceDecl>(prevTypeParam->getDeclContext()) &&
825                    cast<ObjCInterfaceDecl>(prevTypeParam->getDeclContext())
826                      ->getDefinition() == prevTypeParam->getDeclContext())) {
827         // When the old parameter is invariant and was not part of the
828         // definition, just ignore the difference because it doesn't
829         // matter.
830       } else {
831         {
832           // Diagnose the conflict and update the second declaration.
833           SourceLocation diagLoc = newTypeParam->getVarianceLoc();
834           if (diagLoc.isInvalid())
835             diagLoc = newTypeParam->getLocStart();
836 
837           auto diag = S.Diag(diagLoc,
838                              diag::err_objc_type_param_variance_conflict)
839                         << static_cast<unsigned>(newTypeParam->getVariance())
840                         << newTypeParam->getDeclName()
841                         << static_cast<unsigned>(prevTypeParam->getVariance())
842                         << prevTypeParam->getDeclName();
843           switch (prevTypeParam->getVariance()) {
844           case ObjCTypeParamVariance::Invariant:
845             diag << FixItHint::CreateRemoval(newTypeParam->getVarianceLoc());
846             break;
847 
848           case ObjCTypeParamVariance::Covariant:
849           case ObjCTypeParamVariance::Contravariant: {
850             StringRef newVarianceStr
851                = prevTypeParam->getVariance() == ObjCTypeParamVariance::Covariant
852                    ? "__covariant"
853                    : "__contravariant";
854             if (newTypeParam->getVariance()
855                   == ObjCTypeParamVariance::Invariant) {
856               diag << FixItHint::CreateInsertion(newTypeParam->getLocStart(),
857                                                  (newVarianceStr + " ").str());
858             } else {
859               diag << FixItHint::CreateReplacement(newTypeParam->getVarianceLoc(),
860                                                newVarianceStr);
861             }
862           }
863           }
864         }
865 
866         S.Diag(prevTypeParam->getLocation(), diag::note_objc_type_param_here)
867           << prevTypeParam->getDeclName();
868 
869         // Override the variance.
870         newTypeParam->setVariance(prevTypeParam->getVariance());
871       }
872     }
873 
874     // If the bound types match, there's nothing to do.
875     if (S.Context.hasSameType(prevTypeParam->getUnderlyingType(),
876                               newTypeParam->getUnderlyingType()))
877       continue;
878 
879     // If the new type parameter's bound was explicit, complain about it being
880     // different from the original.
881     if (newTypeParam->hasExplicitBound()) {
882       SourceRange newBoundRange = newTypeParam->getTypeSourceInfo()
883                                     ->getTypeLoc().getSourceRange();
884       S.Diag(newBoundRange.getBegin(), diag::err_objc_type_param_bound_conflict)
885         << newTypeParam->getUnderlyingType()
886         << newTypeParam->getDeclName()
887         << prevTypeParam->hasExplicitBound()
888         << prevTypeParam->getUnderlyingType()
889         << (newTypeParam->getDeclName() == prevTypeParam->getDeclName())
890         << prevTypeParam->getDeclName()
891         << FixItHint::CreateReplacement(
892              newBoundRange,
893              prevTypeParam->getUnderlyingType().getAsString(
894                S.Context.getPrintingPolicy()));
895 
896       S.Diag(prevTypeParam->getLocation(), diag::note_objc_type_param_here)
897         << prevTypeParam->getDeclName();
898 
899       // Override the new type parameter's bound type with the previous type,
900       // so that it's consistent.
901       newTypeParam->setTypeSourceInfo(
902         S.Context.getTrivialTypeSourceInfo(prevTypeParam->getUnderlyingType()));
903       continue;
904     }
905 
906     // The new type parameter got the implicit bound of 'id'. That's okay for
907     // categories and extensions (overwrite it later), but not for forward
908     // declarations and @interfaces, because those must be standalone.
909     if (newContext == TypeParamListContext::ForwardDeclaration ||
910         newContext == TypeParamListContext::Definition) {
911       // Diagnose this problem for forward declarations and definitions.
912       SourceLocation insertionLoc
913         = S.getLocForEndOfToken(newTypeParam->getLocation());
914       std::string newCode
915         = " : " + prevTypeParam->getUnderlyingType().getAsString(
916                     S.Context.getPrintingPolicy());
917       S.Diag(newTypeParam->getLocation(),
918              diag::err_objc_type_param_bound_missing)
919         << prevTypeParam->getUnderlyingType()
920         << newTypeParam->getDeclName()
921         << (newContext == TypeParamListContext::ForwardDeclaration)
922         << FixItHint::CreateInsertion(insertionLoc, newCode);
923 
924       S.Diag(prevTypeParam->getLocation(), diag::note_objc_type_param_here)
925         << prevTypeParam->getDeclName();
926     }
927 
928     // Update the new type parameter's bound to match the previous one.
929     newTypeParam->setTypeSourceInfo(
930       S.Context.getTrivialTypeSourceInfo(prevTypeParam->getUnderlyingType()));
931   }
932 
933   return false;
934 }
935 
936 Decl *Sema::
937 ActOnStartClassInterface(Scope *S, SourceLocation AtInterfaceLoc,
938                          IdentifierInfo *ClassName, SourceLocation ClassLoc,
939                          ObjCTypeParamList *typeParamList,
940                          IdentifierInfo *SuperName, SourceLocation SuperLoc,
941                          ArrayRef<ParsedType> SuperTypeArgs,
942                          SourceRange SuperTypeArgsRange,
943                          Decl * const *ProtoRefs, unsigned NumProtoRefs,
944                          const SourceLocation *ProtoLocs,
945                          SourceLocation EndProtoLoc, AttributeList *AttrList) {
946   assert(ClassName && "Missing class identifier");
947 
948   // Check for another declaration kind with the same name.
949   NamedDecl *PrevDecl =
950       LookupSingleName(TUScope, ClassName, ClassLoc, LookupOrdinaryName,
951                        forRedeclarationInCurContext());
952 
953   if (PrevDecl && !isa<ObjCInterfaceDecl>(PrevDecl)) {
954     Diag(ClassLoc, diag::err_redefinition_different_kind) << ClassName;
955     Diag(PrevDecl->getLocation(), diag::note_previous_definition);
956   }
957 
958   // Create a declaration to describe this @interface.
959   ObjCInterfaceDecl* PrevIDecl = dyn_cast_or_null<ObjCInterfaceDecl>(PrevDecl);
960 
961   if (PrevIDecl && PrevIDecl->getIdentifier() != ClassName) {
962     // A previous decl with a different name is because of
963     // @compatibility_alias, for example:
964     // \code
965     //   @class NewImage;
966     //   @compatibility_alias OldImage NewImage;
967     // \endcode
968     // A lookup for 'OldImage' will return the 'NewImage' decl.
969     //
970     // In such a case use the real declaration name, instead of the alias one,
971     // otherwise we will break IdentifierResolver and redecls-chain invariants.
972     // FIXME: If necessary, add a bit to indicate that this ObjCInterfaceDecl
973     // has been aliased.
974     ClassName = PrevIDecl->getIdentifier();
975   }
976 
977   // If there was a forward declaration with type parameters, check
978   // for consistency.
979   if (PrevIDecl) {
980     if (ObjCTypeParamList *prevTypeParamList = PrevIDecl->getTypeParamList()) {
981       if (typeParamList) {
982         // Both have type parameter lists; check for consistency.
983         if (checkTypeParamListConsistency(*this, prevTypeParamList,
984                                           typeParamList,
985                                           TypeParamListContext::Definition)) {
986           typeParamList = nullptr;
987         }
988       } else {
989         Diag(ClassLoc, diag::err_objc_parameterized_forward_class_first)
990           << ClassName;
991         Diag(prevTypeParamList->getLAngleLoc(), diag::note_previous_decl)
992           << ClassName;
993 
994         // Clone the type parameter list.
995         SmallVector<ObjCTypeParamDecl *, 4> clonedTypeParams;
996         for (auto typeParam : *prevTypeParamList) {
997           clonedTypeParams.push_back(
998             ObjCTypeParamDecl::Create(
999               Context,
1000               CurContext,
1001               typeParam->getVariance(),
1002               SourceLocation(),
1003               typeParam->getIndex(),
1004               SourceLocation(),
1005               typeParam->getIdentifier(),
1006               SourceLocation(),
1007               Context.getTrivialTypeSourceInfo(typeParam->getUnderlyingType())));
1008         }
1009 
1010         typeParamList = ObjCTypeParamList::create(Context,
1011                                                   SourceLocation(),
1012                                                   clonedTypeParams,
1013                                                   SourceLocation());
1014       }
1015     }
1016   }
1017 
1018   ObjCInterfaceDecl *IDecl
1019     = ObjCInterfaceDecl::Create(Context, CurContext, AtInterfaceLoc, ClassName,
1020                                 typeParamList, PrevIDecl, ClassLoc);
1021   if (PrevIDecl) {
1022     // Class already seen. Was it a definition?
1023     if (ObjCInterfaceDecl *Def = PrevIDecl->getDefinition()) {
1024       Diag(AtInterfaceLoc, diag::err_duplicate_class_def)
1025         << PrevIDecl->getDeclName();
1026       Diag(Def->getLocation(), diag::note_previous_definition);
1027       IDecl->setInvalidDecl();
1028     }
1029   }
1030 
1031   if (AttrList)
1032     ProcessDeclAttributeList(TUScope, IDecl, AttrList);
1033   AddPragmaAttributes(TUScope, IDecl);
1034   PushOnScopeChains(IDecl, TUScope);
1035 
1036   // Start the definition of this class. If we're in a redefinition case, there
1037   // may already be a definition, so we'll end up adding to it.
1038   if (!IDecl->hasDefinition())
1039     IDecl->startDefinition();
1040 
1041   if (SuperName) {
1042     // Diagnose availability in the context of the @interface.
1043     ContextRAII SavedContext(*this, IDecl);
1044 
1045     ActOnSuperClassOfClassInterface(S, AtInterfaceLoc, IDecl,
1046                                     ClassName, ClassLoc,
1047                                     SuperName, SuperLoc, SuperTypeArgs,
1048                                     SuperTypeArgsRange);
1049   } else { // we have a root class.
1050     IDecl->setEndOfDefinitionLoc(ClassLoc);
1051   }
1052 
1053   // Check then save referenced protocols.
1054   if (NumProtoRefs) {
1055     diagnoseUseOfProtocols(*this, IDecl, (ObjCProtocolDecl*const*)ProtoRefs,
1056                            NumProtoRefs, ProtoLocs);
1057     IDecl->setProtocolList((ObjCProtocolDecl*const*)ProtoRefs, NumProtoRefs,
1058                            ProtoLocs, Context);
1059     IDecl->setEndOfDefinitionLoc(EndProtoLoc);
1060   }
1061 
1062   CheckObjCDeclScope(IDecl);
1063   return ActOnObjCContainerStartDefinition(IDecl);
1064 }
1065 
1066 /// ActOnTypedefedProtocols - this action finds protocol list as part of the
1067 /// typedef'ed use for a qualified super class and adds them to the list
1068 /// of the protocols.
1069 void Sema::ActOnTypedefedProtocols(SmallVectorImpl<Decl *> &ProtocolRefs,
1070                                   SmallVectorImpl<SourceLocation> &ProtocolLocs,
1071                                    IdentifierInfo *SuperName,
1072                                    SourceLocation SuperLoc) {
1073   if (!SuperName)
1074     return;
1075   NamedDecl* IDecl = LookupSingleName(TUScope, SuperName, SuperLoc,
1076                                       LookupOrdinaryName);
1077   if (!IDecl)
1078     return;
1079 
1080   if (const TypedefNameDecl *TDecl = dyn_cast_or_null<TypedefNameDecl>(IDecl)) {
1081     QualType T = TDecl->getUnderlyingType();
1082     if (T->isObjCObjectType())
1083       if (const ObjCObjectType *OPT = T->getAs<ObjCObjectType>()) {
1084         ProtocolRefs.append(OPT->qual_begin(), OPT->qual_end());
1085         // FIXME: Consider whether this should be an invalid loc since the loc
1086         // is not actually pointing to a protocol name reference but to the
1087         // typedef reference. Note that the base class name loc is also pointing
1088         // at the typedef.
1089         ProtocolLocs.append(OPT->getNumProtocols(), SuperLoc);
1090       }
1091   }
1092 }
1093 
1094 /// ActOnCompatibilityAlias - this action is called after complete parsing of
1095 /// a \@compatibility_alias declaration. It sets up the alias relationships.
1096 Decl *Sema::ActOnCompatibilityAlias(SourceLocation AtLoc,
1097                                     IdentifierInfo *AliasName,
1098                                     SourceLocation AliasLocation,
1099                                     IdentifierInfo *ClassName,
1100                                     SourceLocation ClassLocation) {
1101   // Look for previous declaration of alias name
1102   NamedDecl *ADecl =
1103       LookupSingleName(TUScope, AliasName, AliasLocation, LookupOrdinaryName,
1104                        forRedeclarationInCurContext());
1105   if (ADecl) {
1106     Diag(AliasLocation, diag::err_conflicting_aliasing_type) << AliasName;
1107     Diag(ADecl->getLocation(), diag::note_previous_declaration);
1108     return nullptr;
1109   }
1110   // Check for class declaration
1111   NamedDecl *CDeclU =
1112       LookupSingleName(TUScope, ClassName, ClassLocation, LookupOrdinaryName,
1113                        forRedeclarationInCurContext());
1114   if (const TypedefNameDecl *TDecl =
1115         dyn_cast_or_null<TypedefNameDecl>(CDeclU)) {
1116     QualType T = TDecl->getUnderlyingType();
1117     if (T->isObjCObjectType()) {
1118       if (NamedDecl *IDecl = T->getAs<ObjCObjectType>()->getInterface()) {
1119         ClassName = IDecl->getIdentifier();
1120         CDeclU = LookupSingleName(TUScope, ClassName, ClassLocation,
1121                                   LookupOrdinaryName,
1122                                   forRedeclarationInCurContext());
1123       }
1124     }
1125   }
1126   ObjCInterfaceDecl *CDecl = dyn_cast_or_null<ObjCInterfaceDecl>(CDeclU);
1127   if (!CDecl) {
1128     Diag(ClassLocation, diag::warn_undef_interface) << ClassName;
1129     if (CDeclU)
1130       Diag(CDeclU->getLocation(), diag::note_previous_declaration);
1131     return nullptr;
1132   }
1133 
1134   // Everything checked out, instantiate a new alias declaration AST.
1135   ObjCCompatibleAliasDecl *AliasDecl =
1136     ObjCCompatibleAliasDecl::Create(Context, CurContext, AtLoc, AliasName, CDecl);
1137 
1138   if (!CheckObjCDeclScope(AliasDecl))
1139     PushOnScopeChains(AliasDecl, TUScope);
1140 
1141   return AliasDecl;
1142 }
1143 
1144 bool Sema::CheckForwardProtocolDeclarationForCircularDependency(
1145   IdentifierInfo *PName,
1146   SourceLocation &Ploc, SourceLocation PrevLoc,
1147   const ObjCList<ObjCProtocolDecl> &PList) {
1148 
1149   bool res = false;
1150   for (ObjCList<ObjCProtocolDecl>::iterator I = PList.begin(),
1151        E = PList.end(); I != E; ++I) {
1152     if (ObjCProtocolDecl *PDecl = LookupProtocol((*I)->getIdentifier(),
1153                                                  Ploc)) {
1154       if (PDecl->getIdentifier() == PName) {
1155         Diag(Ploc, diag::err_protocol_has_circular_dependency);
1156         Diag(PrevLoc, diag::note_previous_definition);
1157         res = true;
1158       }
1159 
1160       if (!PDecl->hasDefinition())
1161         continue;
1162 
1163       if (CheckForwardProtocolDeclarationForCircularDependency(PName, Ploc,
1164             PDecl->getLocation(), PDecl->getReferencedProtocols()))
1165         res = true;
1166     }
1167   }
1168   return res;
1169 }
1170 
1171 Decl *
1172 Sema::ActOnStartProtocolInterface(SourceLocation AtProtoInterfaceLoc,
1173                                   IdentifierInfo *ProtocolName,
1174                                   SourceLocation ProtocolLoc,
1175                                   Decl * const *ProtoRefs,
1176                                   unsigned NumProtoRefs,
1177                                   const SourceLocation *ProtoLocs,
1178                                   SourceLocation EndProtoLoc,
1179                                   AttributeList *AttrList) {
1180   bool err = false;
1181   // FIXME: Deal with AttrList.
1182   assert(ProtocolName && "Missing protocol identifier");
1183   ObjCProtocolDecl *PrevDecl = LookupProtocol(ProtocolName, ProtocolLoc,
1184                                               forRedeclarationInCurContext());
1185   ObjCProtocolDecl *PDecl = nullptr;
1186   if (ObjCProtocolDecl *Def = PrevDecl? PrevDecl->getDefinition() : nullptr) {
1187     // If we already have a definition, complain.
1188     Diag(ProtocolLoc, diag::warn_duplicate_protocol_def) << ProtocolName;
1189     Diag(Def->getLocation(), diag::note_previous_definition);
1190 
1191     // Create a new protocol that is completely distinct from previous
1192     // declarations, and do not make this protocol available for name lookup.
1193     // That way, we'll end up completely ignoring the duplicate.
1194     // FIXME: Can we turn this into an error?
1195     PDecl = ObjCProtocolDecl::Create(Context, CurContext, ProtocolName,
1196                                      ProtocolLoc, AtProtoInterfaceLoc,
1197                                      /*PrevDecl=*/nullptr);
1198     PDecl->startDefinition();
1199   } else {
1200     if (PrevDecl) {
1201       // Check for circular dependencies among protocol declarations. This can
1202       // only happen if this protocol was forward-declared.
1203       ObjCList<ObjCProtocolDecl> PList;
1204       PList.set((ObjCProtocolDecl *const*)ProtoRefs, NumProtoRefs, Context);
1205       err = CheckForwardProtocolDeclarationForCircularDependency(
1206               ProtocolName, ProtocolLoc, PrevDecl->getLocation(), PList);
1207     }
1208 
1209     // Create the new declaration.
1210     PDecl = ObjCProtocolDecl::Create(Context, CurContext, ProtocolName,
1211                                      ProtocolLoc, AtProtoInterfaceLoc,
1212                                      /*PrevDecl=*/PrevDecl);
1213 
1214     PushOnScopeChains(PDecl, TUScope);
1215     PDecl->startDefinition();
1216   }
1217 
1218   if (AttrList)
1219     ProcessDeclAttributeList(TUScope, PDecl, AttrList);
1220   AddPragmaAttributes(TUScope, PDecl);
1221 
1222   // Merge attributes from previous declarations.
1223   if (PrevDecl)
1224     mergeDeclAttributes(PDecl, PrevDecl);
1225 
1226   if (!err && NumProtoRefs ) {
1227     /// Check then save referenced protocols.
1228     diagnoseUseOfProtocols(*this, PDecl, (ObjCProtocolDecl*const*)ProtoRefs,
1229                            NumProtoRefs, ProtoLocs);
1230     PDecl->setProtocolList((ObjCProtocolDecl*const*)ProtoRefs, NumProtoRefs,
1231                            ProtoLocs, Context);
1232   }
1233 
1234   CheckObjCDeclScope(PDecl);
1235   return ActOnObjCContainerStartDefinition(PDecl);
1236 }
1237 
1238 static bool NestedProtocolHasNoDefinition(ObjCProtocolDecl *PDecl,
1239                                           ObjCProtocolDecl *&UndefinedProtocol) {
1240   if (!PDecl->hasDefinition() || PDecl->getDefinition()->isHidden()) {
1241     UndefinedProtocol = PDecl;
1242     return true;
1243   }
1244 
1245   for (auto *PI : PDecl->protocols())
1246     if (NestedProtocolHasNoDefinition(PI, UndefinedProtocol)) {
1247       UndefinedProtocol = PI;
1248       return true;
1249     }
1250   return false;
1251 }
1252 
1253 /// FindProtocolDeclaration - This routine looks up protocols and
1254 /// issues an error if they are not declared. It returns list of
1255 /// protocol declarations in its 'Protocols' argument.
1256 void
1257 Sema::FindProtocolDeclaration(bool WarnOnDeclarations, bool ForObjCContainer,
1258                               ArrayRef<IdentifierLocPair> ProtocolId,
1259                               SmallVectorImpl<Decl *> &Protocols) {
1260   for (const IdentifierLocPair &Pair : ProtocolId) {
1261     ObjCProtocolDecl *PDecl = LookupProtocol(Pair.first, Pair.second);
1262     if (!PDecl) {
1263       TypoCorrection Corrected = CorrectTypo(
1264           DeclarationNameInfo(Pair.first, Pair.second),
1265           LookupObjCProtocolName, TUScope, nullptr,
1266           llvm::make_unique<DeclFilterCCC<ObjCProtocolDecl>>(),
1267           CTK_ErrorRecovery);
1268       if ((PDecl = Corrected.getCorrectionDeclAs<ObjCProtocolDecl>()))
1269         diagnoseTypo(Corrected, PDiag(diag::err_undeclared_protocol_suggest)
1270                                     << Pair.first);
1271     }
1272 
1273     if (!PDecl) {
1274       Diag(Pair.second, diag::err_undeclared_protocol) << Pair.first;
1275       continue;
1276     }
1277     // If this is a forward protocol declaration, get its definition.
1278     if (!PDecl->isThisDeclarationADefinition() && PDecl->getDefinition())
1279       PDecl = PDecl->getDefinition();
1280 
1281     // For an objc container, delay protocol reference checking until after we
1282     // can set the objc decl as the availability context, otherwise check now.
1283     if (!ForObjCContainer) {
1284       (void)DiagnoseUseOfDecl(PDecl, Pair.second);
1285     }
1286 
1287     // If this is a forward declaration and we are supposed to warn in this
1288     // case, do it.
1289     // FIXME: Recover nicely in the hidden case.
1290     ObjCProtocolDecl *UndefinedProtocol;
1291 
1292     if (WarnOnDeclarations &&
1293         NestedProtocolHasNoDefinition(PDecl, UndefinedProtocol)) {
1294       Diag(Pair.second, diag::warn_undef_protocolref) << Pair.first;
1295       Diag(UndefinedProtocol->getLocation(), diag::note_protocol_decl_undefined)
1296         << UndefinedProtocol;
1297     }
1298     Protocols.push_back(PDecl);
1299   }
1300 }
1301 
1302 namespace {
1303 // Callback to only accept typo corrections that are either
1304 // Objective-C protocols or valid Objective-C type arguments.
1305 class ObjCTypeArgOrProtocolValidatorCCC : public CorrectionCandidateCallback {
1306   ASTContext &Context;
1307   Sema::LookupNameKind LookupKind;
1308  public:
1309   ObjCTypeArgOrProtocolValidatorCCC(ASTContext &context,
1310                                     Sema::LookupNameKind lookupKind)
1311     : Context(context), LookupKind(lookupKind) { }
1312 
1313   bool ValidateCandidate(const TypoCorrection &candidate) override {
1314     // If we're allowed to find protocols and we have a protocol, accept it.
1315     if (LookupKind != Sema::LookupOrdinaryName) {
1316       if (candidate.getCorrectionDeclAs<ObjCProtocolDecl>())
1317         return true;
1318     }
1319 
1320     // If we're allowed to find type names and we have one, accept it.
1321     if (LookupKind != Sema::LookupObjCProtocolName) {
1322       // If we have a type declaration, we might accept this result.
1323       if (auto typeDecl = candidate.getCorrectionDeclAs<TypeDecl>()) {
1324         // If we found a tag declaration outside of C++, skip it. This
1325         // can happy because we look for any name when there is no
1326         // bias to protocol or type names.
1327         if (isa<RecordDecl>(typeDecl) && !Context.getLangOpts().CPlusPlus)
1328           return false;
1329 
1330         // Make sure the type is something we would accept as a type
1331         // argument.
1332         auto type = Context.getTypeDeclType(typeDecl);
1333         if (type->isObjCObjectPointerType() ||
1334             type->isBlockPointerType() ||
1335             type->isDependentType() ||
1336             type->isObjCObjectType())
1337           return true;
1338 
1339         return false;
1340       }
1341 
1342       // If we have an Objective-C class type, accept it; there will
1343       // be another fix to add the '*'.
1344       if (candidate.getCorrectionDeclAs<ObjCInterfaceDecl>())
1345         return true;
1346 
1347       return false;
1348     }
1349 
1350     return false;
1351   }
1352 };
1353 } // end anonymous namespace
1354 
1355 void Sema::DiagnoseTypeArgsAndProtocols(IdentifierInfo *ProtocolId,
1356                                         SourceLocation ProtocolLoc,
1357                                         IdentifierInfo *TypeArgId,
1358                                         SourceLocation TypeArgLoc,
1359                                         bool SelectProtocolFirst) {
1360   Diag(TypeArgLoc, diag::err_objc_type_args_and_protocols)
1361       << SelectProtocolFirst << TypeArgId << ProtocolId
1362       << SourceRange(ProtocolLoc);
1363 }
1364 
1365 void Sema::actOnObjCTypeArgsOrProtocolQualifiers(
1366        Scope *S,
1367        ParsedType baseType,
1368        SourceLocation lAngleLoc,
1369        ArrayRef<IdentifierInfo *> identifiers,
1370        ArrayRef<SourceLocation> identifierLocs,
1371        SourceLocation rAngleLoc,
1372        SourceLocation &typeArgsLAngleLoc,
1373        SmallVectorImpl<ParsedType> &typeArgs,
1374        SourceLocation &typeArgsRAngleLoc,
1375        SourceLocation &protocolLAngleLoc,
1376        SmallVectorImpl<Decl *> &protocols,
1377        SourceLocation &protocolRAngleLoc,
1378        bool warnOnIncompleteProtocols) {
1379   // Local function that updates the declaration specifiers with
1380   // protocol information.
1381   unsigned numProtocolsResolved = 0;
1382   auto resolvedAsProtocols = [&] {
1383     assert(numProtocolsResolved == identifiers.size() && "Unresolved protocols");
1384 
1385     // Determine whether the base type is a parameterized class, in
1386     // which case we want to warn about typos such as
1387     // "NSArray<NSObject>" (that should be NSArray<NSObject *>).
1388     ObjCInterfaceDecl *baseClass = nullptr;
1389     QualType base = GetTypeFromParser(baseType, nullptr);
1390     bool allAreTypeNames = false;
1391     SourceLocation firstClassNameLoc;
1392     if (!base.isNull()) {
1393       if (const auto *objcObjectType = base->getAs<ObjCObjectType>()) {
1394         baseClass = objcObjectType->getInterface();
1395         if (baseClass) {
1396           if (auto typeParams = baseClass->getTypeParamList()) {
1397             if (typeParams->size() == numProtocolsResolved) {
1398               // Note that we should be looking for type names, too.
1399               allAreTypeNames = true;
1400             }
1401           }
1402         }
1403       }
1404     }
1405 
1406     for (unsigned i = 0, n = protocols.size(); i != n; ++i) {
1407       ObjCProtocolDecl *&proto
1408         = reinterpret_cast<ObjCProtocolDecl *&>(protocols[i]);
1409       // For an objc container, delay protocol reference checking until after we
1410       // can set the objc decl as the availability context, otherwise check now.
1411       if (!warnOnIncompleteProtocols) {
1412         (void)DiagnoseUseOfDecl(proto, identifierLocs[i]);
1413       }
1414 
1415       // If this is a forward protocol declaration, get its definition.
1416       if (!proto->isThisDeclarationADefinition() && proto->getDefinition())
1417         proto = proto->getDefinition();
1418 
1419       // If this is a forward declaration and we are supposed to warn in this
1420       // case, do it.
1421       // FIXME: Recover nicely in the hidden case.
1422       ObjCProtocolDecl *forwardDecl = nullptr;
1423       if (warnOnIncompleteProtocols &&
1424           NestedProtocolHasNoDefinition(proto, forwardDecl)) {
1425         Diag(identifierLocs[i], diag::warn_undef_protocolref)
1426           << proto->getDeclName();
1427         Diag(forwardDecl->getLocation(), diag::note_protocol_decl_undefined)
1428           << forwardDecl;
1429       }
1430 
1431       // If everything this far has been a type name (and we care
1432       // about such things), check whether this name refers to a type
1433       // as well.
1434       if (allAreTypeNames) {
1435         if (auto *decl = LookupSingleName(S, identifiers[i], identifierLocs[i],
1436                                           LookupOrdinaryName)) {
1437           if (isa<ObjCInterfaceDecl>(decl)) {
1438             if (firstClassNameLoc.isInvalid())
1439               firstClassNameLoc = identifierLocs[i];
1440           } else if (!isa<TypeDecl>(decl)) {
1441             // Not a type.
1442             allAreTypeNames = false;
1443           }
1444         } else {
1445           allAreTypeNames = false;
1446         }
1447       }
1448     }
1449 
1450     // All of the protocols listed also have type names, and at least
1451     // one is an Objective-C class name. Check whether all of the
1452     // protocol conformances are declared by the base class itself, in
1453     // which case we warn.
1454     if (allAreTypeNames && firstClassNameLoc.isValid()) {
1455       llvm::SmallPtrSet<ObjCProtocolDecl*, 8> knownProtocols;
1456       Context.CollectInheritedProtocols(baseClass, knownProtocols);
1457       bool allProtocolsDeclared = true;
1458       for (auto proto : protocols) {
1459         if (knownProtocols.count(static_cast<ObjCProtocolDecl *>(proto)) == 0) {
1460           allProtocolsDeclared = false;
1461           break;
1462         }
1463       }
1464 
1465       if (allProtocolsDeclared) {
1466         Diag(firstClassNameLoc, diag::warn_objc_redundant_qualified_class_type)
1467           << baseClass->getDeclName() << SourceRange(lAngleLoc, rAngleLoc)
1468           << FixItHint::CreateInsertion(getLocForEndOfToken(firstClassNameLoc),
1469                                         " *");
1470       }
1471     }
1472 
1473     protocolLAngleLoc = lAngleLoc;
1474     protocolRAngleLoc = rAngleLoc;
1475     assert(protocols.size() == identifierLocs.size());
1476   };
1477 
1478   // Attempt to resolve all of the identifiers as protocols.
1479   for (unsigned i = 0, n = identifiers.size(); i != n; ++i) {
1480     ObjCProtocolDecl *proto = LookupProtocol(identifiers[i], identifierLocs[i]);
1481     protocols.push_back(proto);
1482     if (proto)
1483       ++numProtocolsResolved;
1484   }
1485 
1486   // If all of the names were protocols, these were protocol qualifiers.
1487   if (numProtocolsResolved == identifiers.size())
1488     return resolvedAsProtocols();
1489 
1490   // Attempt to resolve all of the identifiers as type names or
1491   // Objective-C class names. The latter is technically ill-formed,
1492   // but is probably something like \c NSArray<NSView *> missing the
1493   // \c*.
1494   typedef llvm::PointerUnion<TypeDecl *, ObjCInterfaceDecl *> TypeOrClassDecl;
1495   SmallVector<TypeOrClassDecl, 4> typeDecls;
1496   unsigned numTypeDeclsResolved = 0;
1497   for (unsigned i = 0, n = identifiers.size(); i != n; ++i) {
1498     NamedDecl *decl = LookupSingleName(S, identifiers[i], identifierLocs[i],
1499                                        LookupOrdinaryName);
1500     if (!decl) {
1501       typeDecls.push_back(TypeOrClassDecl());
1502       continue;
1503     }
1504 
1505     if (auto typeDecl = dyn_cast<TypeDecl>(decl)) {
1506       typeDecls.push_back(typeDecl);
1507       ++numTypeDeclsResolved;
1508       continue;
1509     }
1510 
1511     if (auto objcClass = dyn_cast<ObjCInterfaceDecl>(decl)) {
1512       typeDecls.push_back(objcClass);
1513       ++numTypeDeclsResolved;
1514       continue;
1515     }
1516 
1517     typeDecls.push_back(TypeOrClassDecl());
1518   }
1519 
1520   AttributeFactory attrFactory;
1521 
1522   // Local function that forms a reference to the given type or
1523   // Objective-C class declaration.
1524   auto resolveTypeReference = [&](TypeOrClassDecl typeDecl, SourceLocation loc)
1525                                 -> TypeResult {
1526     // Form declaration specifiers. They simply refer to the type.
1527     DeclSpec DS(attrFactory);
1528     const char* prevSpec; // unused
1529     unsigned diagID; // unused
1530     QualType type;
1531     if (auto *actualTypeDecl = typeDecl.dyn_cast<TypeDecl *>())
1532       type = Context.getTypeDeclType(actualTypeDecl);
1533     else
1534       type = Context.getObjCInterfaceType(typeDecl.get<ObjCInterfaceDecl *>());
1535     TypeSourceInfo *parsedTSInfo = Context.getTrivialTypeSourceInfo(type, loc);
1536     ParsedType parsedType = CreateParsedType(type, parsedTSInfo);
1537     DS.SetTypeSpecType(DeclSpec::TST_typename, loc, prevSpec, diagID,
1538                        parsedType, Context.getPrintingPolicy());
1539     // Use the identifier location for the type source range.
1540     DS.SetRangeStart(loc);
1541     DS.SetRangeEnd(loc);
1542 
1543     // Form the declarator.
1544     Declarator D(DS, DeclaratorContext::TypeNameContext);
1545 
1546     // If we have a typedef of an Objective-C class type that is missing a '*',
1547     // add the '*'.
1548     if (type->getAs<ObjCInterfaceType>()) {
1549       SourceLocation starLoc = getLocForEndOfToken(loc);
1550       ParsedAttributes parsedAttrs(attrFactory);
1551       D.AddTypeInfo(DeclaratorChunk::getPointer(/*typeQuals=*/0, starLoc,
1552                                                 SourceLocation(),
1553                                                 SourceLocation(),
1554                                                 SourceLocation(),
1555                                                 SourceLocation(),
1556                                                 SourceLocation()),
1557                                                 parsedAttrs,
1558                                                 starLoc);
1559 
1560       // Diagnose the missing '*'.
1561       Diag(loc, diag::err_objc_type_arg_missing_star)
1562         << type
1563         << FixItHint::CreateInsertion(starLoc, " *");
1564     }
1565 
1566     // Convert this to a type.
1567     return ActOnTypeName(S, D);
1568   };
1569 
1570   // Local function that updates the declaration specifiers with
1571   // type argument information.
1572   auto resolvedAsTypeDecls = [&] {
1573     // We did not resolve these as protocols.
1574     protocols.clear();
1575 
1576     assert(numTypeDeclsResolved == identifiers.size() && "Unresolved type decl");
1577     // Map type declarations to type arguments.
1578     for (unsigned i = 0, n = identifiers.size(); i != n; ++i) {
1579       // Map type reference to a type.
1580       TypeResult type = resolveTypeReference(typeDecls[i], identifierLocs[i]);
1581       if (!type.isUsable()) {
1582         typeArgs.clear();
1583         return;
1584       }
1585 
1586       typeArgs.push_back(type.get());
1587     }
1588 
1589     typeArgsLAngleLoc = lAngleLoc;
1590     typeArgsRAngleLoc = rAngleLoc;
1591   };
1592 
1593   // If all of the identifiers can be resolved as type names or
1594   // Objective-C class names, we have type arguments.
1595   if (numTypeDeclsResolved == identifiers.size())
1596     return resolvedAsTypeDecls();
1597 
1598   // Error recovery: some names weren't found, or we have a mix of
1599   // type and protocol names. Go resolve all of the unresolved names
1600   // and complain if we can't find a consistent answer.
1601   LookupNameKind lookupKind = LookupAnyName;
1602   for (unsigned i = 0, n = identifiers.size(); i != n; ++i) {
1603     // If we already have a protocol or type. Check whether it is the
1604     // right thing.
1605     if (protocols[i] || typeDecls[i]) {
1606       // If we haven't figured out whether we want types or protocols
1607       // yet, try to figure it out from this name.
1608       if (lookupKind == LookupAnyName) {
1609         // If this name refers to both a protocol and a type (e.g., \c
1610         // NSObject), don't conclude anything yet.
1611         if (protocols[i] && typeDecls[i])
1612           continue;
1613 
1614         // Otherwise, let this name decide whether we'll be correcting
1615         // toward types or protocols.
1616         lookupKind = protocols[i] ? LookupObjCProtocolName
1617                                   : LookupOrdinaryName;
1618         continue;
1619       }
1620 
1621       // If we want protocols and we have a protocol, there's nothing
1622       // more to do.
1623       if (lookupKind == LookupObjCProtocolName && protocols[i])
1624         continue;
1625 
1626       // If we want types and we have a type declaration, there's
1627       // nothing more to do.
1628       if (lookupKind == LookupOrdinaryName && typeDecls[i])
1629         continue;
1630 
1631       // We have a conflict: some names refer to protocols and others
1632       // refer to types.
1633       DiagnoseTypeArgsAndProtocols(identifiers[0], identifierLocs[0],
1634                                    identifiers[i], identifierLocs[i],
1635                                    protocols[i] != nullptr);
1636 
1637       protocols.clear();
1638       typeArgs.clear();
1639       return;
1640     }
1641 
1642     // Perform typo correction on the name.
1643     TypoCorrection corrected = CorrectTypo(
1644         DeclarationNameInfo(identifiers[i], identifierLocs[i]), lookupKind, S,
1645         nullptr,
1646         llvm::make_unique<ObjCTypeArgOrProtocolValidatorCCC>(Context,
1647                                                              lookupKind),
1648         CTK_ErrorRecovery);
1649     if (corrected) {
1650       // Did we find a protocol?
1651       if (auto proto = corrected.getCorrectionDeclAs<ObjCProtocolDecl>()) {
1652         diagnoseTypo(corrected,
1653                      PDiag(diag::err_undeclared_protocol_suggest)
1654                        << identifiers[i]);
1655         lookupKind = LookupObjCProtocolName;
1656         protocols[i] = proto;
1657         ++numProtocolsResolved;
1658         continue;
1659       }
1660 
1661       // Did we find a type?
1662       if (auto typeDecl = corrected.getCorrectionDeclAs<TypeDecl>()) {
1663         diagnoseTypo(corrected,
1664                      PDiag(diag::err_unknown_typename_suggest)
1665                        << identifiers[i]);
1666         lookupKind = LookupOrdinaryName;
1667         typeDecls[i] = typeDecl;
1668         ++numTypeDeclsResolved;
1669         continue;
1670       }
1671 
1672       // Did we find an Objective-C class?
1673       if (auto objcClass = corrected.getCorrectionDeclAs<ObjCInterfaceDecl>()) {
1674         diagnoseTypo(corrected,
1675                      PDiag(diag::err_unknown_type_or_class_name_suggest)
1676                        << identifiers[i] << true);
1677         lookupKind = LookupOrdinaryName;
1678         typeDecls[i] = objcClass;
1679         ++numTypeDeclsResolved;
1680         continue;
1681       }
1682     }
1683 
1684     // We couldn't find anything.
1685     Diag(identifierLocs[i],
1686          (lookupKind == LookupAnyName ? diag::err_objc_type_arg_missing
1687           : lookupKind == LookupObjCProtocolName ? diag::err_undeclared_protocol
1688           : diag::err_unknown_typename))
1689       << identifiers[i];
1690     protocols.clear();
1691     typeArgs.clear();
1692     return;
1693   }
1694 
1695   // If all of the names were (corrected to) protocols, these were
1696   // protocol qualifiers.
1697   if (numProtocolsResolved == identifiers.size())
1698     return resolvedAsProtocols();
1699 
1700   // Otherwise, all of the names were (corrected to) types.
1701   assert(numTypeDeclsResolved == identifiers.size() && "Not all types?");
1702   return resolvedAsTypeDecls();
1703 }
1704 
1705 /// DiagnoseClassExtensionDupMethods - Check for duplicate declaration of
1706 /// a class method in its extension.
1707 ///
1708 void Sema::DiagnoseClassExtensionDupMethods(ObjCCategoryDecl *CAT,
1709                                             ObjCInterfaceDecl *ID) {
1710   if (!ID)
1711     return;  // Possibly due to previous error
1712 
1713   llvm::DenseMap<Selector, const ObjCMethodDecl*> MethodMap;
1714   for (auto *MD : ID->methods())
1715     MethodMap[MD->getSelector()] = MD;
1716 
1717   if (MethodMap.empty())
1718     return;
1719   for (const auto *Method : CAT->methods()) {
1720     const ObjCMethodDecl *&PrevMethod = MethodMap[Method->getSelector()];
1721     if (PrevMethod &&
1722         (PrevMethod->isInstanceMethod() == Method->isInstanceMethod()) &&
1723         !MatchTwoMethodDeclarations(Method, PrevMethod)) {
1724       Diag(Method->getLocation(), diag::err_duplicate_method_decl)
1725             << Method->getDeclName();
1726       Diag(PrevMethod->getLocation(), diag::note_previous_declaration);
1727     }
1728   }
1729 }
1730 
1731 /// ActOnForwardProtocolDeclaration - Handle \@protocol foo;
1732 Sema::DeclGroupPtrTy
1733 Sema::ActOnForwardProtocolDeclaration(SourceLocation AtProtocolLoc,
1734                                       ArrayRef<IdentifierLocPair> IdentList,
1735                                       AttributeList *attrList) {
1736   SmallVector<Decl *, 8> DeclsInGroup;
1737   for (const IdentifierLocPair &IdentPair : IdentList) {
1738     IdentifierInfo *Ident = IdentPair.first;
1739     ObjCProtocolDecl *PrevDecl = LookupProtocol(Ident, IdentPair.second,
1740                                                 forRedeclarationInCurContext());
1741     ObjCProtocolDecl *PDecl
1742       = ObjCProtocolDecl::Create(Context, CurContext, Ident,
1743                                  IdentPair.second, AtProtocolLoc,
1744                                  PrevDecl);
1745 
1746     PushOnScopeChains(PDecl, TUScope);
1747     CheckObjCDeclScope(PDecl);
1748 
1749     if (attrList)
1750       ProcessDeclAttributeList(TUScope, PDecl, attrList);
1751     AddPragmaAttributes(TUScope, PDecl);
1752 
1753     if (PrevDecl)
1754       mergeDeclAttributes(PDecl, PrevDecl);
1755 
1756     DeclsInGroup.push_back(PDecl);
1757   }
1758 
1759   return BuildDeclaratorGroup(DeclsInGroup);
1760 }
1761 
1762 Decl *Sema::
1763 ActOnStartCategoryInterface(SourceLocation AtInterfaceLoc,
1764                             IdentifierInfo *ClassName, SourceLocation ClassLoc,
1765                             ObjCTypeParamList *typeParamList,
1766                             IdentifierInfo *CategoryName,
1767                             SourceLocation CategoryLoc,
1768                             Decl * const *ProtoRefs,
1769                             unsigned NumProtoRefs,
1770                             const SourceLocation *ProtoLocs,
1771                             SourceLocation EndProtoLoc,
1772                             AttributeList *AttrList) {
1773   ObjCCategoryDecl *CDecl;
1774   ObjCInterfaceDecl *IDecl = getObjCInterfaceDecl(ClassName, ClassLoc, true);
1775 
1776   /// Check that class of this category is already completely declared.
1777 
1778   if (!IDecl
1779       || RequireCompleteType(ClassLoc, Context.getObjCInterfaceType(IDecl),
1780                              diag::err_category_forward_interface,
1781                              CategoryName == nullptr)) {
1782     // Create an invalid ObjCCategoryDecl to serve as context for
1783     // the enclosing method declarations.  We mark the decl invalid
1784     // to make it clear that this isn't a valid AST.
1785     CDecl = ObjCCategoryDecl::Create(Context, CurContext, AtInterfaceLoc,
1786                                      ClassLoc, CategoryLoc, CategoryName,
1787                                      IDecl, typeParamList);
1788     CDecl->setInvalidDecl();
1789     CurContext->addDecl(CDecl);
1790 
1791     if (!IDecl)
1792       Diag(ClassLoc, diag::err_undef_interface) << ClassName;
1793     return ActOnObjCContainerStartDefinition(CDecl);
1794   }
1795 
1796   if (!CategoryName && IDecl->getImplementation()) {
1797     Diag(ClassLoc, diag::err_class_extension_after_impl) << ClassName;
1798     Diag(IDecl->getImplementation()->getLocation(),
1799           diag::note_implementation_declared);
1800   }
1801 
1802   if (CategoryName) {
1803     /// Check for duplicate interface declaration for this category
1804     if (ObjCCategoryDecl *Previous
1805           = IDecl->FindCategoryDeclaration(CategoryName)) {
1806       // Class extensions can be declared multiple times, categories cannot.
1807       Diag(CategoryLoc, diag::warn_dup_category_def)
1808         << ClassName << CategoryName;
1809       Diag(Previous->getLocation(), diag::note_previous_definition);
1810     }
1811   }
1812 
1813   // If we have a type parameter list, check it.
1814   if (typeParamList) {
1815     if (auto prevTypeParamList = IDecl->getTypeParamList()) {
1816       if (checkTypeParamListConsistency(*this, prevTypeParamList, typeParamList,
1817                                         CategoryName
1818                                           ? TypeParamListContext::Category
1819                                           : TypeParamListContext::Extension))
1820         typeParamList = nullptr;
1821     } else {
1822       Diag(typeParamList->getLAngleLoc(),
1823            diag::err_objc_parameterized_category_nonclass)
1824         << (CategoryName != nullptr)
1825         << ClassName
1826         << typeParamList->getSourceRange();
1827 
1828       typeParamList = nullptr;
1829     }
1830   }
1831 
1832   CDecl = ObjCCategoryDecl::Create(Context, CurContext, AtInterfaceLoc,
1833                                    ClassLoc, CategoryLoc, CategoryName, IDecl,
1834                                    typeParamList);
1835   // FIXME: PushOnScopeChains?
1836   CurContext->addDecl(CDecl);
1837 
1838   // Process the attributes before looking at protocols to ensure that the
1839   // availability attribute is attached to the category to provide availability
1840   // checking for protocol uses.
1841   if (AttrList)
1842     ProcessDeclAttributeList(TUScope, CDecl, AttrList);
1843   AddPragmaAttributes(TUScope, CDecl);
1844 
1845   if (NumProtoRefs) {
1846     diagnoseUseOfProtocols(*this, CDecl, (ObjCProtocolDecl*const*)ProtoRefs,
1847                            NumProtoRefs, ProtoLocs);
1848     CDecl->setProtocolList((ObjCProtocolDecl*const*)ProtoRefs, NumProtoRefs,
1849                            ProtoLocs, Context);
1850     // Protocols in the class extension belong to the class.
1851     if (CDecl->IsClassExtension())
1852      IDecl->mergeClassExtensionProtocolList((ObjCProtocolDecl*const*)ProtoRefs,
1853                                             NumProtoRefs, Context);
1854   }
1855 
1856   CheckObjCDeclScope(CDecl);
1857   return ActOnObjCContainerStartDefinition(CDecl);
1858 }
1859 
1860 /// ActOnStartCategoryImplementation - Perform semantic checks on the
1861 /// category implementation declaration and build an ObjCCategoryImplDecl
1862 /// object.
1863 Decl *Sema::ActOnStartCategoryImplementation(
1864                       SourceLocation AtCatImplLoc,
1865                       IdentifierInfo *ClassName, SourceLocation ClassLoc,
1866                       IdentifierInfo *CatName, SourceLocation CatLoc) {
1867   ObjCInterfaceDecl *IDecl = getObjCInterfaceDecl(ClassName, ClassLoc, true);
1868   ObjCCategoryDecl *CatIDecl = nullptr;
1869   if (IDecl && IDecl->hasDefinition()) {
1870     CatIDecl = IDecl->FindCategoryDeclaration(CatName);
1871     if (!CatIDecl) {
1872       // Category @implementation with no corresponding @interface.
1873       // Create and install one.
1874       CatIDecl = ObjCCategoryDecl::Create(Context, CurContext, AtCatImplLoc,
1875                                           ClassLoc, CatLoc,
1876                                           CatName, IDecl,
1877                                           /*typeParamList=*/nullptr);
1878       CatIDecl->setImplicit();
1879     }
1880   }
1881 
1882   ObjCCategoryImplDecl *CDecl =
1883     ObjCCategoryImplDecl::Create(Context, CurContext, CatName, IDecl,
1884                                  ClassLoc, AtCatImplLoc, CatLoc);
1885   /// Check that class of this category is already completely declared.
1886   if (!IDecl) {
1887     Diag(ClassLoc, diag::err_undef_interface) << ClassName;
1888     CDecl->setInvalidDecl();
1889   } else if (RequireCompleteType(ClassLoc, Context.getObjCInterfaceType(IDecl),
1890                                  diag::err_undef_interface)) {
1891     CDecl->setInvalidDecl();
1892   }
1893 
1894   // FIXME: PushOnScopeChains?
1895   CurContext->addDecl(CDecl);
1896 
1897   // If the interface has the objc_runtime_visible attribute, we
1898   // cannot implement a category for it.
1899   if (IDecl && IDecl->hasAttr<ObjCRuntimeVisibleAttr>()) {
1900     Diag(ClassLoc, diag::err_objc_runtime_visible_category)
1901       << IDecl->getDeclName();
1902   }
1903 
1904   /// Check that CatName, category name, is not used in another implementation.
1905   if (CatIDecl) {
1906     if (CatIDecl->getImplementation()) {
1907       Diag(ClassLoc, diag::err_dup_implementation_category) << ClassName
1908         << CatName;
1909       Diag(CatIDecl->getImplementation()->getLocation(),
1910            diag::note_previous_definition);
1911       CDecl->setInvalidDecl();
1912     } else {
1913       CatIDecl->setImplementation(CDecl);
1914       // Warn on implementating category of deprecated class under
1915       // -Wdeprecated-implementations flag.
1916       DiagnoseObjCImplementedDeprecations(*this, CatIDecl,
1917                                           CDecl->getLocation());
1918     }
1919   }
1920 
1921   CheckObjCDeclScope(CDecl);
1922   return ActOnObjCContainerStartDefinition(CDecl);
1923 }
1924 
1925 Decl *Sema::ActOnStartClassImplementation(
1926                       SourceLocation AtClassImplLoc,
1927                       IdentifierInfo *ClassName, SourceLocation ClassLoc,
1928                       IdentifierInfo *SuperClassname,
1929                       SourceLocation SuperClassLoc) {
1930   ObjCInterfaceDecl *IDecl = nullptr;
1931   // Check for another declaration kind with the same name.
1932   NamedDecl *PrevDecl
1933     = LookupSingleName(TUScope, ClassName, ClassLoc, LookupOrdinaryName,
1934                        forRedeclarationInCurContext());
1935   if (PrevDecl && !isa<ObjCInterfaceDecl>(PrevDecl)) {
1936     Diag(ClassLoc, diag::err_redefinition_different_kind) << ClassName;
1937     Diag(PrevDecl->getLocation(), diag::note_previous_definition);
1938   } else if ((IDecl = dyn_cast_or_null<ObjCInterfaceDecl>(PrevDecl))) {
1939     // FIXME: This will produce an error if the definition of the interface has
1940     // been imported from a module but is not visible.
1941     RequireCompleteType(ClassLoc, Context.getObjCInterfaceType(IDecl),
1942                         diag::warn_undef_interface);
1943   } else {
1944     // We did not find anything with the name ClassName; try to correct for
1945     // typos in the class name.
1946     TypoCorrection Corrected = CorrectTypo(
1947         DeclarationNameInfo(ClassName, ClassLoc), LookupOrdinaryName, TUScope,
1948         nullptr, llvm::make_unique<ObjCInterfaceValidatorCCC>(), CTK_NonError);
1949     if (Corrected.getCorrectionDeclAs<ObjCInterfaceDecl>()) {
1950       // Suggest the (potentially) correct interface name. Don't provide a
1951       // code-modification hint or use the typo name for recovery, because
1952       // this is just a warning. The program may actually be correct.
1953       diagnoseTypo(Corrected,
1954                    PDiag(diag::warn_undef_interface_suggest) << ClassName,
1955                    /*ErrorRecovery*/false);
1956     } else {
1957       Diag(ClassLoc, diag::warn_undef_interface) << ClassName;
1958     }
1959   }
1960 
1961   // Check that super class name is valid class name
1962   ObjCInterfaceDecl *SDecl = nullptr;
1963   if (SuperClassname) {
1964     // Check if a different kind of symbol declared in this scope.
1965     PrevDecl = LookupSingleName(TUScope, SuperClassname, SuperClassLoc,
1966                                 LookupOrdinaryName);
1967     if (PrevDecl && !isa<ObjCInterfaceDecl>(PrevDecl)) {
1968       Diag(SuperClassLoc, diag::err_redefinition_different_kind)
1969         << SuperClassname;
1970       Diag(PrevDecl->getLocation(), diag::note_previous_definition);
1971     } else {
1972       SDecl = dyn_cast_or_null<ObjCInterfaceDecl>(PrevDecl);
1973       if (SDecl && !SDecl->hasDefinition())
1974         SDecl = nullptr;
1975       if (!SDecl)
1976         Diag(SuperClassLoc, diag::err_undef_superclass)
1977           << SuperClassname << ClassName;
1978       else if (IDecl && !declaresSameEntity(IDecl->getSuperClass(), SDecl)) {
1979         // This implementation and its interface do not have the same
1980         // super class.
1981         Diag(SuperClassLoc, diag::err_conflicting_super_class)
1982           << SDecl->getDeclName();
1983         Diag(SDecl->getLocation(), diag::note_previous_definition);
1984       }
1985     }
1986   }
1987 
1988   if (!IDecl) {
1989     // Legacy case of @implementation with no corresponding @interface.
1990     // Build, chain & install the interface decl into the identifier.
1991 
1992     // FIXME: Do we support attributes on the @implementation? If so we should
1993     // copy them over.
1994     IDecl = ObjCInterfaceDecl::Create(Context, CurContext, AtClassImplLoc,
1995                                       ClassName, /*typeParamList=*/nullptr,
1996                                       /*PrevDecl=*/nullptr, ClassLoc,
1997                                       true);
1998     AddPragmaAttributes(TUScope, IDecl);
1999     IDecl->startDefinition();
2000     if (SDecl) {
2001       IDecl->setSuperClass(Context.getTrivialTypeSourceInfo(
2002                              Context.getObjCInterfaceType(SDecl),
2003                              SuperClassLoc));
2004       IDecl->setEndOfDefinitionLoc(SuperClassLoc);
2005     } else {
2006       IDecl->setEndOfDefinitionLoc(ClassLoc);
2007     }
2008 
2009     PushOnScopeChains(IDecl, TUScope);
2010   } else {
2011     // Mark the interface as being completed, even if it was just as
2012     //   @class ....;
2013     // declaration; the user cannot reopen it.
2014     if (!IDecl->hasDefinition())
2015       IDecl->startDefinition();
2016   }
2017 
2018   ObjCImplementationDecl* IMPDecl =
2019     ObjCImplementationDecl::Create(Context, CurContext, IDecl, SDecl,
2020                                    ClassLoc, AtClassImplLoc, SuperClassLoc);
2021 
2022   if (CheckObjCDeclScope(IMPDecl))
2023     return ActOnObjCContainerStartDefinition(IMPDecl);
2024 
2025   // Check that there is no duplicate implementation of this class.
2026   if (IDecl->getImplementation()) {
2027     // FIXME: Don't leak everything!
2028     Diag(ClassLoc, diag::err_dup_implementation_class) << ClassName;
2029     Diag(IDecl->getImplementation()->getLocation(),
2030          diag::note_previous_definition);
2031     IMPDecl->setInvalidDecl();
2032   } else { // add it to the list.
2033     IDecl->setImplementation(IMPDecl);
2034     PushOnScopeChains(IMPDecl, TUScope);
2035     // Warn on implementating deprecated class under
2036     // -Wdeprecated-implementations flag.
2037     DiagnoseObjCImplementedDeprecations(*this, IDecl, IMPDecl->getLocation());
2038   }
2039 
2040   // If the superclass has the objc_runtime_visible attribute, we
2041   // cannot implement a subclass of it.
2042   if (IDecl->getSuperClass() &&
2043       IDecl->getSuperClass()->hasAttr<ObjCRuntimeVisibleAttr>()) {
2044     Diag(ClassLoc, diag::err_objc_runtime_visible_subclass)
2045       << IDecl->getDeclName()
2046       << IDecl->getSuperClass()->getDeclName();
2047   }
2048 
2049   return ActOnObjCContainerStartDefinition(IMPDecl);
2050 }
2051 
2052 Sema::DeclGroupPtrTy
2053 Sema::ActOnFinishObjCImplementation(Decl *ObjCImpDecl, ArrayRef<Decl *> Decls) {
2054   SmallVector<Decl *, 64> DeclsInGroup;
2055   DeclsInGroup.reserve(Decls.size() + 1);
2056 
2057   for (unsigned i = 0, e = Decls.size(); i != e; ++i) {
2058     Decl *Dcl = Decls[i];
2059     if (!Dcl)
2060       continue;
2061     if (Dcl->getDeclContext()->isFileContext())
2062       Dcl->setTopLevelDeclInObjCContainer();
2063     DeclsInGroup.push_back(Dcl);
2064   }
2065 
2066   DeclsInGroup.push_back(ObjCImpDecl);
2067 
2068   return BuildDeclaratorGroup(DeclsInGroup);
2069 }
2070 
2071 void Sema::CheckImplementationIvars(ObjCImplementationDecl *ImpDecl,
2072                                     ObjCIvarDecl **ivars, unsigned numIvars,
2073                                     SourceLocation RBrace) {
2074   assert(ImpDecl && "missing implementation decl");
2075   ObjCInterfaceDecl* IDecl = ImpDecl->getClassInterface();
2076   if (!IDecl)
2077     return;
2078   /// Check case of non-existing \@interface decl.
2079   /// (legacy objective-c \@implementation decl without an \@interface decl).
2080   /// Add implementations's ivar to the synthesize class's ivar list.
2081   if (IDecl->isImplicitInterfaceDecl()) {
2082     IDecl->setEndOfDefinitionLoc(RBrace);
2083     // Add ivar's to class's DeclContext.
2084     for (unsigned i = 0, e = numIvars; i != e; ++i) {
2085       ivars[i]->setLexicalDeclContext(ImpDecl);
2086       IDecl->makeDeclVisibleInContext(ivars[i]);
2087       ImpDecl->addDecl(ivars[i]);
2088     }
2089 
2090     return;
2091   }
2092   // If implementation has empty ivar list, just return.
2093   if (numIvars == 0)
2094     return;
2095 
2096   assert(ivars && "missing @implementation ivars");
2097   if (LangOpts.ObjCRuntime.isNonFragile()) {
2098     if (ImpDecl->getSuperClass())
2099       Diag(ImpDecl->getLocation(), diag::warn_on_superclass_use);
2100     for (unsigned i = 0; i < numIvars; i++) {
2101       ObjCIvarDecl* ImplIvar = ivars[i];
2102       if (const ObjCIvarDecl *ClsIvar =
2103             IDecl->getIvarDecl(ImplIvar->getIdentifier())) {
2104         Diag(ImplIvar->getLocation(), diag::err_duplicate_ivar_declaration);
2105         Diag(ClsIvar->getLocation(), diag::note_previous_definition);
2106         continue;
2107       }
2108       // Check class extensions (unnamed categories) for duplicate ivars.
2109       for (const auto *CDecl : IDecl->visible_extensions()) {
2110         if (const ObjCIvarDecl *ClsExtIvar =
2111             CDecl->getIvarDecl(ImplIvar->getIdentifier())) {
2112           Diag(ImplIvar->getLocation(), diag::err_duplicate_ivar_declaration);
2113           Diag(ClsExtIvar->getLocation(), diag::note_previous_definition);
2114           continue;
2115         }
2116       }
2117       // Instance ivar to Implementation's DeclContext.
2118       ImplIvar->setLexicalDeclContext(ImpDecl);
2119       IDecl->makeDeclVisibleInContext(ImplIvar);
2120       ImpDecl->addDecl(ImplIvar);
2121     }
2122     return;
2123   }
2124   // Check interface's Ivar list against those in the implementation.
2125   // names and types must match.
2126   //
2127   unsigned j = 0;
2128   ObjCInterfaceDecl::ivar_iterator
2129     IVI = IDecl->ivar_begin(), IVE = IDecl->ivar_end();
2130   for (; numIvars > 0 && IVI != IVE; ++IVI) {
2131     ObjCIvarDecl* ImplIvar = ivars[j++];
2132     ObjCIvarDecl* ClsIvar = *IVI;
2133     assert (ImplIvar && "missing implementation ivar");
2134     assert (ClsIvar && "missing class ivar");
2135 
2136     // First, make sure the types match.
2137     if (!Context.hasSameType(ImplIvar->getType(), ClsIvar->getType())) {
2138       Diag(ImplIvar->getLocation(), diag::err_conflicting_ivar_type)
2139         << ImplIvar->getIdentifier()
2140         << ImplIvar->getType() << ClsIvar->getType();
2141       Diag(ClsIvar->getLocation(), diag::note_previous_definition);
2142     } else if (ImplIvar->isBitField() && ClsIvar->isBitField() &&
2143                ImplIvar->getBitWidthValue(Context) !=
2144                ClsIvar->getBitWidthValue(Context)) {
2145       Diag(ImplIvar->getBitWidth()->getLocStart(),
2146            diag::err_conflicting_ivar_bitwidth) << ImplIvar->getIdentifier();
2147       Diag(ClsIvar->getBitWidth()->getLocStart(),
2148            diag::note_previous_definition);
2149     }
2150     // Make sure the names are identical.
2151     if (ImplIvar->getIdentifier() != ClsIvar->getIdentifier()) {
2152       Diag(ImplIvar->getLocation(), diag::err_conflicting_ivar_name)
2153         << ImplIvar->getIdentifier() << ClsIvar->getIdentifier();
2154       Diag(ClsIvar->getLocation(), diag::note_previous_definition);
2155     }
2156     --numIvars;
2157   }
2158 
2159   if (numIvars > 0)
2160     Diag(ivars[j]->getLocation(), diag::err_inconsistent_ivar_count);
2161   else if (IVI != IVE)
2162     Diag(IVI->getLocation(), diag::err_inconsistent_ivar_count);
2163 }
2164 
2165 static void WarnUndefinedMethod(Sema &S, SourceLocation ImpLoc,
2166                                 ObjCMethodDecl *method,
2167                                 bool &IncompleteImpl,
2168                                 unsigned DiagID,
2169                                 NamedDecl *NeededFor = nullptr) {
2170   // No point warning no definition of method which is 'unavailable'.
2171   switch (method->getAvailability()) {
2172   case AR_Available:
2173   case AR_Deprecated:
2174     break;
2175 
2176       // Don't warn about unavailable or not-yet-introduced methods.
2177   case AR_NotYetIntroduced:
2178   case AR_Unavailable:
2179     return;
2180   }
2181 
2182   // FIXME: For now ignore 'IncompleteImpl'.
2183   // Previously we grouped all unimplemented methods under a single
2184   // warning, but some users strongly voiced that they would prefer
2185   // separate warnings.  We will give that approach a try, as that
2186   // matches what we do with protocols.
2187   {
2188     const Sema::SemaDiagnosticBuilder &B = S.Diag(ImpLoc, DiagID);
2189     B << method;
2190     if (NeededFor)
2191       B << NeededFor;
2192   }
2193 
2194   // Issue a note to the original declaration.
2195   SourceLocation MethodLoc = method->getLocStart();
2196   if (MethodLoc.isValid())
2197     S.Diag(MethodLoc, diag::note_method_declared_at) << method;
2198 }
2199 
2200 /// Determines if type B can be substituted for type A.  Returns true if we can
2201 /// guarantee that anything that the user will do to an object of type A can
2202 /// also be done to an object of type B.  This is trivially true if the two
2203 /// types are the same, or if B is a subclass of A.  It becomes more complex
2204 /// in cases where protocols are involved.
2205 ///
2206 /// Object types in Objective-C describe the minimum requirements for an
2207 /// object, rather than providing a complete description of a type.  For
2208 /// example, if A is a subclass of B, then B* may refer to an instance of A.
2209 /// The principle of substitutability means that we may use an instance of A
2210 /// anywhere that we may use an instance of B - it will implement all of the
2211 /// ivars of B and all of the methods of B.
2212 ///
2213 /// This substitutability is important when type checking methods, because
2214 /// the implementation may have stricter type definitions than the interface.
2215 /// The interface specifies minimum requirements, but the implementation may
2216 /// have more accurate ones.  For example, a method may privately accept
2217 /// instances of B, but only publish that it accepts instances of A.  Any
2218 /// object passed to it will be type checked against B, and so will implicitly
2219 /// by a valid A*.  Similarly, a method may return a subclass of the class that
2220 /// it is declared as returning.
2221 ///
2222 /// This is most important when considering subclassing.  A method in a
2223 /// subclass must accept any object as an argument that its superclass's
2224 /// implementation accepts.  It may, however, accept a more general type
2225 /// without breaking substitutability (i.e. you can still use the subclass
2226 /// anywhere that you can use the superclass, but not vice versa).  The
2227 /// converse requirement applies to return types: the return type for a
2228 /// subclass method must be a valid object of the kind that the superclass
2229 /// advertises, but it may be specified more accurately.  This avoids the need
2230 /// for explicit down-casting by callers.
2231 ///
2232 /// Note: This is a stricter requirement than for assignment.
2233 static bool isObjCTypeSubstitutable(ASTContext &Context,
2234                                     const ObjCObjectPointerType *A,
2235                                     const ObjCObjectPointerType *B,
2236                                     bool rejectId) {
2237   // Reject a protocol-unqualified id.
2238   if (rejectId && B->isObjCIdType()) return false;
2239 
2240   // If B is a qualified id, then A must also be a qualified id and it must
2241   // implement all of the protocols in B.  It may not be a qualified class.
2242   // For example, MyClass<A> can be assigned to id<A>, but MyClass<A> is a
2243   // stricter definition so it is not substitutable for id<A>.
2244   if (B->isObjCQualifiedIdType()) {
2245     return A->isObjCQualifiedIdType() &&
2246            Context.ObjCQualifiedIdTypesAreCompatible(QualType(A, 0),
2247                                                      QualType(B,0),
2248                                                      false);
2249   }
2250 
2251   /*
2252   // id is a special type that bypasses type checking completely.  We want a
2253   // warning when it is used in one place but not another.
2254   if (C.isObjCIdType(A) || C.isObjCIdType(B)) return false;
2255 
2256 
2257   // If B is a qualified id, then A must also be a qualified id (which it isn't
2258   // if we've got this far)
2259   if (B->isObjCQualifiedIdType()) return false;
2260   */
2261 
2262   // Now we know that A and B are (potentially-qualified) class types.  The
2263   // normal rules for assignment apply.
2264   return Context.canAssignObjCInterfaces(A, B);
2265 }
2266 
2267 static SourceRange getTypeRange(TypeSourceInfo *TSI) {
2268   return (TSI ? TSI->getTypeLoc().getSourceRange() : SourceRange());
2269 }
2270 
2271 /// Determine whether two set of Objective-C declaration qualifiers conflict.
2272 static bool objcModifiersConflict(Decl::ObjCDeclQualifier x,
2273                                   Decl::ObjCDeclQualifier y) {
2274   return (x & ~Decl::OBJC_TQ_CSNullability) !=
2275          (y & ~Decl::OBJC_TQ_CSNullability);
2276 }
2277 
2278 static bool CheckMethodOverrideReturn(Sema &S,
2279                                       ObjCMethodDecl *MethodImpl,
2280                                       ObjCMethodDecl *MethodDecl,
2281                                       bool IsProtocolMethodDecl,
2282                                       bool IsOverridingMode,
2283                                       bool Warn) {
2284   if (IsProtocolMethodDecl &&
2285       objcModifiersConflict(MethodDecl->getObjCDeclQualifier(),
2286                             MethodImpl->getObjCDeclQualifier())) {
2287     if (Warn) {
2288       S.Diag(MethodImpl->getLocation(),
2289              (IsOverridingMode
2290                   ? diag::warn_conflicting_overriding_ret_type_modifiers
2291                   : diag::warn_conflicting_ret_type_modifiers))
2292           << MethodImpl->getDeclName()
2293           << MethodImpl->getReturnTypeSourceRange();
2294       S.Diag(MethodDecl->getLocation(), diag::note_previous_declaration)
2295           << MethodDecl->getReturnTypeSourceRange();
2296     }
2297     else
2298       return false;
2299   }
2300   if (Warn && IsOverridingMode &&
2301       !isa<ObjCImplementationDecl>(MethodImpl->getDeclContext()) &&
2302       !S.Context.hasSameNullabilityTypeQualifier(MethodImpl->getReturnType(),
2303                                                  MethodDecl->getReturnType(),
2304                                                  false)) {
2305     auto nullabilityMethodImpl =
2306       *MethodImpl->getReturnType()->getNullability(S.Context);
2307     auto nullabilityMethodDecl =
2308       *MethodDecl->getReturnType()->getNullability(S.Context);
2309       S.Diag(MethodImpl->getLocation(),
2310              diag::warn_conflicting_nullability_attr_overriding_ret_types)
2311         << DiagNullabilityKind(
2312              nullabilityMethodImpl,
2313              ((MethodImpl->getObjCDeclQualifier() & Decl::OBJC_TQ_CSNullability)
2314               != 0))
2315         << DiagNullabilityKind(
2316              nullabilityMethodDecl,
2317              ((MethodDecl->getObjCDeclQualifier() & Decl::OBJC_TQ_CSNullability)
2318                 != 0));
2319       S.Diag(MethodDecl->getLocation(), diag::note_previous_declaration);
2320   }
2321 
2322   if (S.Context.hasSameUnqualifiedType(MethodImpl->getReturnType(),
2323                                        MethodDecl->getReturnType()))
2324     return true;
2325   if (!Warn)
2326     return false;
2327 
2328   unsigned DiagID =
2329     IsOverridingMode ? diag::warn_conflicting_overriding_ret_types
2330                      : diag::warn_conflicting_ret_types;
2331 
2332   // Mismatches between ObjC pointers go into a different warning
2333   // category, and sometimes they're even completely whitelisted.
2334   if (const ObjCObjectPointerType *ImplPtrTy =
2335           MethodImpl->getReturnType()->getAs<ObjCObjectPointerType>()) {
2336     if (const ObjCObjectPointerType *IfacePtrTy =
2337             MethodDecl->getReturnType()->getAs<ObjCObjectPointerType>()) {
2338       // Allow non-matching return types as long as they don't violate
2339       // the principle of substitutability.  Specifically, we permit
2340       // return types that are subclasses of the declared return type,
2341       // or that are more-qualified versions of the declared type.
2342       if (isObjCTypeSubstitutable(S.Context, IfacePtrTy, ImplPtrTy, false))
2343         return false;
2344 
2345       DiagID =
2346         IsOverridingMode ? diag::warn_non_covariant_overriding_ret_types
2347                          : diag::warn_non_covariant_ret_types;
2348     }
2349   }
2350 
2351   S.Diag(MethodImpl->getLocation(), DiagID)
2352       << MethodImpl->getDeclName() << MethodDecl->getReturnType()
2353       << MethodImpl->getReturnType()
2354       << MethodImpl->getReturnTypeSourceRange();
2355   S.Diag(MethodDecl->getLocation(), IsOverridingMode
2356                                         ? diag::note_previous_declaration
2357                                         : diag::note_previous_definition)
2358       << MethodDecl->getReturnTypeSourceRange();
2359   return false;
2360 }
2361 
2362 static bool CheckMethodOverrideParam(Sema &S,
2363                                      ObjCMethodDecl *MethodImpl,
2364                                      ObjCMethodDecl *MethodDecl,
2365                                      ParmVarDecl *ImplVar,
2366                                      ParmVarDecl *IfaceVar,
2367                                      bool IsProtocolMethodDecl,
2368                                      bool IsOverridingMode,
2369                                      bool Warn) {
2370   if (IsProtocolMethodDecl &&
2371       objcModifiersConflict(ImplVar->getObjCDeclQualifier(),
2372                             IfaceVar->getObjCDeclQualifier())) {
2373     if (Warn) {
2374       if (IsOverridingMode)
2375         S.Diag(ImplVar->getLocation(),
2376                diag::warn_conflicting_overriding_param_modifiers)
2377             << getTypeRange(ImplVar->getTypeSourceInfo())
2378             << MethodImpl->getDeclName();
2379       else S.Diag(ImplVar->getLocation(),
2380              diag::warn_conflicting_param_modifiers)
2381           << getTypeRange(ImplVar->getTypeSourceInfo())
2382           << MethodImpl->getDeclName();
2383       S.Diag(IfaceVar->getLocation(), diag::note_previous_declaration)
2384           << getTypeRange(IfaceVar->getTypeSourceInfo());
2385     }
2386     else
2387       return false;
2388   }
2389 
2390   QualType ImplTy = ImplVar->getType();
2391   QualType IfaceTy = IfaceVar->getType();
2392   if (Warn && IsOverridingMode &&
2393       !isa<ObjCImplementationDecl>(MethodImpl->getDeclContext()) &&
2394       !S.Context.hasSameNullabilityTypeQualifier(ImplTy, IfaceTy, true)) {
2395     S.Diag(ImplVar->getLocation(),
2396            diag::warn_conflicting_nullability_attr_overriding_param_types)
2397       << DiagNullabilityKind(
2398            *ImplTy->getNullability(S.Context),
2399            ((ImplVar->getObjCDeclQualifier() & Decl::OBJC_TQ_CSNullability)
2400             != 0))
2401       << DiagNullabilityKind(
2402            *IfaceTy->getNullability(S.Context),
2403            ((IfaceVar->getObjCDeclQualifier() & Decl::OBJC_TQ_CSNullability)
2404             != 0));
2405     S.Diag(IfaceVar->getLocation(), diag::note_previous_declaration);
2406   }
2407   if (S.Context.hasSameUnqualifiedType(ImplTy, IfaceTy))
2408     return true;
2409 
2410   if (!Warn)
2411     return false;
2412   unsigned DiagID =
2413     IsOverridingMode ? diag::warn_conflicting_overriding_param_types
2414                      : diag::warn_conflicting_param_types;
2415 
2416   // Mismatches between ObjC pointers go into a different warning
2417   // category, and sometimes they're even completely whitelisted.
2418   if (const ObjCObjectPointerType *ImplPtrTy =
2419         ImplTy->getAs<ObjCObjectPointerType>()) {
2420     if (const ObjCObjectPointerType *IfacePtrTy =
2421           IfaceTy->getAs<ObjCObjectPointerType>()) {
2422       // Allow non-matching argument types as long as they don't
2423       // violate the principle of substitutability.  Specifically, the
2424       // implementation must accept any objects that the superclass
2425       // accepts, however it may also accept others.
2426       if (isObjCTypeSubstitutable(S.Context, ImplPtrTy, IfacePtrTy, true))
2427         return false;
2428 
2429       DiagID =
2430       IsOverridingMode ? diag::warn_non_contravariant_overriding_param_types
2431                        : diag::warn_non_contravariant_param_types;
2432     }
2433   }
2434 
2435   S.Diag(ImplVar->getLocation(), DiagID)
2436     << getTypeRange(ImplVar->getTypeSourceInfo())
2437     << MethodImpl->getDeclName() << IfaceTy << ImplTy;
2438   S.Diag(IfaceVar->getLocation(),
2439          (IsOverridingMode ? diag::note_previous_declaration
2440                            : diag::note_previous_definition))
2441     << getTypeRange(IfaceVar->getTypeSourceInfo());
2442   return false;
2443 }
2444 
2445 /// In ARC, check whether the conventional meanings of the two methods
2446 /// match.  If they don't, it's a hard error.
2447 static bool checkMethodFamilyMismatch(Sema &S, ObjCMethodDecl *impl,
2448                                       ObjCMethodDecl *decl) {
2449   ObjCMethodFamily implFamily = impl->getMethodFamily();
2450   ObjCMethodFamily declFamily = decl->getMethodFamily();
2451   if (implFamily == declFamily) return false;
2452 
2453   // Since conventions are sorted by selector, the only possibility is
2454   // that the types differ enough to cause one selector or the other
2455   // to fall out of the family.
2456   assert(implFamily == OMF_None || declFamily == OMF_None);
2457 
2458   // No further diagnostics required on invalid declarations.
2459   if (impl->isInvalidDecl() || decl->isInvalidDecl()) return true;
2460 
2461   const ObjCMethodDecl *unmatched = impl;
2462   ObjCMethodFamily family = declFamily;
2463   unsigned errorID = diag::err_arc_lost_method_convention;
2464   unsigned noteID = diag::note_arc_lost_method_convention;
2465   if (declFamily == OMF_None) {
2466     unmatched = decl;
2467     family = implFamily;
2468     errorID = diag::err_arc_gained_method_convention;
2469     noteID = diag::note_arc_gained_method_convention;
2470   }
2471 
2472   // Indexes into a %select clause in the diagnostic.
2473   enum FamilySelector {
2474     F_alloc, F_copy, F_mutableCopy = F_copy, F_init, F_new
2475   };
2476   FamilySelector familySelector = FamilySelector();
2477 
2478   switch (family) {
2479   case OMF_None: llvm_unreachable("logic error, no method convention");
2480   case OMF_retain:
2481   case OMF_release:
2482   case OMF_autorelease:
2483   case OMF_dealloc:
2484   case OMF_finalize:
2485   case OMF_retainCount:
2486   case OMF_self:
2487   case OMF_initialize:
2488   case OMF_performSelector:
2489     // Mismatches for these methods don't change ownership
2490     // conventions, so we don't care.
2491     return false;
2492 
2493   case OMF_init: familySelector = F_init; break;
2494   case OMF_alloc: familySelector = F_alloc; break;
2495   case OMF_copy: familySelector = F_copy; break;
2496   case OMF_mutableCopy: familySelector = F_mutableCopy; break;
2497   case OMF_new: familySelector = F_new; break;
2498   }
2499 
2500   enum ReasonSelector { R_NonObjectReturn, R_UnrelatedReturn };
2501   ReasonSelector reasonSelector;
2502 
2503   // The only reason these methods don't fall within their families is
2504   // due to unusual result types.
2505   if (unmatched->getReturnType()->isObjCObjectPointerType()) {
2506     reasonSelector = R_UnrelatedReturn;
2507   } else {
2508     reasonSelector = R_NonObjectReturn;
2509   }
2510 
2511   S.Diag(impl->getLocation(), errorID) << int(familySelector) << int(reasonSelector);
2512   S.Diag(decl->getLocation(), noteID) << int(familySelector) << int(reasonSelector);
2513 
2514   return true;
2515 }
2516 
2517 void Sema::WarnConflictingTypedMethods(ObjCMethodDecl *ImpMethodDecl,
2518                                        ObjCMethodDecl *MethodDecl,
2519                                        bool IsProtocolMethodDecl) {
2520   if (getLangOpts().ObjCAutoRefCount &&
2521       checkMethodFamilyMismatch(*this, ImpMethodDecl, MethodDecl))
2522     return;
2523 
2524   CheckMethodOverrideReturn(*this, ImpMethodDecl, MethodDecl,
2525                             IsProtocolMethodDecl, false,
2526                             true);
2527 
2528   for (ObjCMethodDecl::param_iterator IM = ImpMethodDecl->param_begin(),
2529        IF = MethodDecl->param_begin(), EM = ImpMethodDecl->param_end(),
2530        EF = MethodDecl->param_end();
2531        IM != EM && IF != EF; ++IM, ++IF) {
2532     CheckMethodOverrideParam(*this, ImpMethodDecl, MethodDecl, *IM, *IF,
2533                              IsProtocolMethodDecl, false, true);
2534   }
2535 
2536   if (ImpMethodDecl->isVariadic() != MethodDecl->isVariadic()) {
2537     Diag(ImpMethodDecl->getLocation(),
2538          diag::warn_conflicting_variadic);
2539     Diag(MethodDecl->getLocation(), diag::note_previous_declaration);
2540   }
2541 }
2542 
2543 void Sema::CheckConflictingOverridingMethod(ObjCMethodDecl *Method,
2544                                        ObjCMethodDecl *Overridden,
2545                                        bool IsProtocolMethodDecl) {
2546 
2547   CheckMethodOverrideReturn(*this, Method, Overridden,
2548                             IsProtocolMethodDecl, true,
2549                             true);
2550 
2551   for (ObjCMethodDecl::param_iterator IM = Method->param_begin(),
2552        IF = Overridden->param_begin(), EM = Method->param_end(),
2553        EF = Overridden->param_end();
2554        IM != EM && IF != EF; ++IM, ++IF) {
2555     CheckMethodOverrideParam(*this, Method, Overridden, *IM, *IF,
2556                              IsProtocolMethodDecl, true, true);
2557   }
2558 
2559   if (Method->isVariadic() != Overridden->isVariadic()) {
2560     Diag(Method->getLocation(),
2561          diag::warn_conflicting_overriding_variadic);
2562     Diag(Overridden->getLocation(), diag::note_previous_declaration);
2563   }
2564 }
2565 
2566 /// WarnExactTypedMethods - This routine issues a warning if method
2567 /// implementation declaration matches exactly that of its declaration.
2568 void Sema::WarnExactTypedMethods(ObjCMethodDecl *ImpMethodDecl,
2569                                  ObjCMethodDecl *MethodDecl,
2570                                  bool IsProtocolMethodDecl) {
2571   // don't issue warning when protocol method is optional because primary
2572   // class is not required to implement it and it is safe for protocol
2573   // to implement it.
2574   if (MethodDecl->getImplementationControl() == ObjCMethodDecl::Optional)
2575     return;
2576   // don't issue warning when primary class's method is
2577   // depecated/unavailable.
2578   if (MethodDecl->hasAttr<UnavailableAttr>() ||
2579       MethodDecl->hasAttr<DeprecatedAttr>())
2580     return;
2581 
2582   bool match = CheckMethodOverrideReturn(*this, ImpMethodDecl, MethodDecl,
2583                                       IsProtocolMethodDecl, false, false);
2584   if (match)
2585     for (ObjCMethodDecl::param_iterator IM = ImpMethodDecl->param_begin(),
2586          IF = MethodDecl->param_begin(), EM = ImpMethodDecl->param_end(),
2587          EF = MethodDecl->param_end();
2588          IM != EM && IF != EF; ++IM, ++IF) {
2589       match = CheckMethodOverrideParam(*this, ImpMethodDecl, MethodDecl,
2590                                        *IM, *IF,
2591                                        IsProtocolMethodDecl, false, false);
2592       if (!match)
2593         break;
2594     }
2595   if (match)
2596     match = (ImpMethodDecl->isVariadic() == MethodDecl->isVariadic());
2597   if (match)
2598     match = !(MethodDecl->isClassMethod() &&
2599               MethodDecl->getSelector() == GetNullarySelector("load", Context));
2600 
2601   if (match) {
2602     Diag(ImpMethodDecl->getLocation(),
2603          diag::warn_category_method_impl_match);
2604     Diag(MethodDecl->getLocation(), diag::note_method_declared_at)
2605       << MethodDecl->getDeclName();
2606   }
2607 }
2608 
2609 /// FIXME: Type hierarchies in Objective-C can be deep. We could most likely
2610 /// improve the efficiency of selector lookups and type checking by associating
2611 /// with each protocol / interface / category the flattened instance tables. If
2612 /// we used an immutable set to keep the table then it wouldn't add significant
2613 /// memory cost and it would be handy for lookups.
2614 
2615 typedef llvm::DenseSet<IdentifierInfo*> ProtocolNameSet;
2616 typedef std::unique_ptr<ProtocolNameSet> LazyProtocolNameSet;
2617 
2618 static void findProtocolsWithExplicitImpls(const ObjCProtocolDecl *PDecl,
2619                                            ProtocolNameSet &PNS) {
2620   if (PDecl->hasAttr<ObjCExplicitProtocolImplAttr>())
2621     PNS.insert(PDecl->getIdentifier());
2622   for (const auto *PI : PDecl->protocols())
2623     findProtocolsWithExplicitImpls(PI, PNS);
2624 }
2625 
2626 /// Recursively populates a set with all conformed protocols in a class
2627 /// hierarchy that have the 'objc_protocol_requires_explicit_implementation'
2628 /// attribute.
2629 static void findProtocolsWithExplicitImpls(const ObjCInterfaceDecl *Super,
2630                                            ProtocolNameSet &PNS) {
2631   if (!Super)
2632     return;
2633 
2634   for (const auto *I : Super->all_referenced_protocols())
2635     findProtocolsWithExplicitImpls(I, PNS);
2636 
2637   findProtocolsWithExplicitImpls(Super->getSuperClass(), PNS);
2638 }
2639 
2640 /// CheckProtocolMethodDefs - This routine checks unimplemented methods
2641 /// Declared in protocol, and those referenced by it.
2642 static void CheckProtocolMethodDefs(Sema &S,
2643                                     SourceLocation ImpLoc,
2644                                     ObjCProtocolDecl *PDecl,
2645                                     bool& IncompleteImpl,
2646                                     const Sema::SelectorSet &InsMap,
2647                                     const Sema::SelectorSet &ClsMap,
2648                                     ObjCContainerDecl *CDecl,
2649                                     LazyProtocolNameSet &ProtocolsExplictImpl) {
2650   ObjCCategoryDecl *C = dyn_cast<ObjCCategoryDecl>(CDecl);
2651   ObjCInterfaceDecl *IDecl = C ? C->getClassInterface()
2652                                : dyn_cast<ObjCInterfaceDecl>(CDecl);
2653   assert (IDecl && "CheckProtocolMethodDefs - IDecl is null");
2654 
2655   ObjCInterfaceDecl *Super = IDecl->getSuperClass();
2656   ObjCInterfaceDecl *NSIDecl = nullptr;
2657 
2658   // If this protocol is marked 'objc_protocol_requires_explicit_implementation'
2659   // then we should check if any class in the super class hierarchy also
2660   // conforms to this protocol, either directly or via protocol inheritance.
2661   // If so, we can skip checking this protocol completely because we
2662   // know that a parent class already satisfies this protocol.
2663   //
2664   // Note: we could generalize this logic for all protocols, and merely
2665   // add the limit on looking at the super class chain for just
2666   // specially marked protocols.  This may be a good optimization.  This
2667   // change is restricted to 'objc_protocol_requires_explicit_implementation'
2668   // protocols for now for controlled evaluation.
2669   if (PDecl->hasAttr<ObjCExplicitProtocolImplAttr>()) {
2670     if (!ProtocolsExplictImpl) {
2671       ProtocolsExplictImpl.reset(new ProtocolNameSet);
2672       findProtocolsWithExplicitImpls(Super, *ProtocolsExplictImpl);
2673     }
2674     if (ProtocolsExplictImpl->find(PDecl->getIdentifier()) !=
2675         ProtocolsExplictImpl->end())
2676       return;
2677 
2678     // If no super class conforms to the protocol, we should not search
2679     // for methods in the super class to implicitly satisfy the protocol.
2680     Super = nullptr;
2681   }
2682 
2683   if (S.getLangOpts().ObjCRuntime.isNeXTFamily()) {
2684     // check to see if class implements forwardInvocation method and objects
2685     // of this class are derived from 'NSProxy' so that to forward requests
2686     // from one object to another.
2687     // Under such conditions, which means that every method possible is
2688     // implemented in the class, we should not issue "Method definition not
2689     // found" warnings.
2690     // FIXME: Use a general GetUnarySelector method for this.
2691     IdentifierInfo* II = &S.Context.Idents.get("forwardInvocation");
2692     Selector fISelector = S.Context.Selectors.getSelector(1, &II);
2693     if (InsMap.count(fISelector))
2694       // Is IDecl derived from 'NSProxy'? If so, no instance methods
2695       // need be implemented in the implementation.
2696       NSIDecl = IDecl->lookupInheritedClass(&S.Context.Idents.get("NSProxy"));
2697   }
2698 
2699   // If this is a forward protocol declaration, get its definition.
2700   if (!PDecl->isThisDeclarationADefinition() &&
2701       PDecl->getDefinition())
2702     PDecl = PDecl->getDefinition();
2703 
2704   // If a method lookup fails locally we still need to look and see if
2705   // the method was implemented by a base class or an inherited
2706   // protocol. This lookup is slow, but occurs rarely in correct code
2707   // and otherwise would terminate in a warning.
2708 
2709   // check unimplemented instance methods.
2710   if (!NSIDecl)
2711     for (auto *method : PDecl->instance_methods()) {
2712       if (method->getImplementationControl() != ObjCMethodDecl::Optional &&
2713           !method->isPropertyAccessor() &&
2714           !InsMap.count(method->getSelector()) &&
2715           (!Super || !Super->lookupMethod(method->getSelector(),
2716                                           true /* instance */,
2717                                           false /* shallowCategory */,
2718                                           true /* followsSuper */,
2719                                           nullptr /* category */))) {
2720             // If a method is not implemented in the category implementation but
2721             // has been declared in its primary class, superclass,
2722             // or in one of their protocols, no need to issue the warning.
2723             // This is because method will be implemented in the primary class
2724             // or one of its super class implementation.
2725 
2726             // Ugly, but necessary. Method declared in protcol might have
2727             // have been synthesized due to a property declared in the class which
2728             // uses the protocol.
2729             if (ObjCMethodDecl *MethodInClass =
2730                   IDecl->lookupMethod(method->getSelector(),
2731                                       true /* instance */,
2732                                       true /* shallowCategoryLookup */,
2733                                       false /* followSuper */))
2734               if (C || MethodInClass->isPropertyAccessor())
2735                 continue;
2736             unsigned DIAG = diag::warn_unimplemented_protocol_method;
2737             if (!S.Diags.isIgnored(DIAG, ImpLoc)) {
2738               WarnUndefinedMethod(S, ImpLoc, method, IncompleteImpl, DIAG,
2739                                   PDecl);
2740             }
2741           }
2742     }
2743   // check unimplemented class methods
2744   for (auto *method : PDecl->class_methods()) {
2745     if (method->getImplementationControl() != ObjCMethodDecl::Optional &&
2746         !ClsMap.count(method->getSelector()) &&
2747         (!Super || !Super->lookupMethod(method->getSelector(),
2748                                         false /* class method */,
2749                                         false /* shallowCategoryLookup */,
2750                                         true  /* followSuper */,
2751                                         nullptr /* category */))) {
2752       // See above comment for instance method lookups.
2753       if (C && IDecl->lookupMethod(method->getSelector(),
2754                                    false /* class */,
2755                                    true /* shallowCategoryLookup */,
2756                                    false /* followSuper */))
2757         continue;
2758 
2759       unsigned DIAG = diag::warn_unimplemented_protocol_method;
2760       if (!S.Diags.isIgnored(DIAG, ImpLoc)) {
2761         WarnUndefinedMethod(S, ImpLoc, method, IncompleteImpl, DIAG, PDecl);
2762       }
2763     }
2764   }
2765   // Check on this protocols's referenced protocols, recursively.
2766   for (auto *PI : PDecl->protocols())
2767     CheckProtocolMethodDefs(S, ImpLoc, PI, IncompleteImpl, InsMap, ClsMap,
2768                             CDecl, ProtocolsExplictImpl);
2769 }
2770 
2771 /// MatchAllMethodDeclarations - Check methods declared in interface
2772 /// or protocol against those declared in their implementations.
2773 ///
2774 void Sema::MatchAllMethodDeclarations(const SelectorSet &InsMap,
2775                                       const SelectorSet &ClsMap,
2776                                       SelectorSet &InsMapSeen,
2777                                       SelectorSet &ClsMapSeen,
2778                                       ObjCImplDecl* IMPDecl,
2779                                       ObjCContainerDecl* CDecl,
2780                                       bool &IncompleteImpl,
2781                                       bool ImmediateClass,
2782                                       bool WarnCategoryMethodImpl) {
2783   // Check and see if instance methods in class interface have been
2784   // implemented in the implementation class. If so, their types match.
2785   for (auto *I : CDecl->instance_methods()) {
2786     if (!InsMapSeen.insert(I->getSelector()).second)
2787       continue;
2788     if (!I->isPropertyAccessor() &&
2789         !InsMap.count(I->getSelector())) {
2790       if (ImmediateClass)
2791         WarnUndefinedMethod(*this, IMPDecl->getLocation(), I, IncompleteImpl,
2792                             diag::warn_undef_method_impl);
2793       continue;
2794     } else {
2795       ObjCMethodDecl *ImpMethodDecl =
2796         IMPDecl->getInstanceMethod(I->getSelector());
2797       assert(CDecl->getInstanceMethod(I->getSelector(), true/*AllowHidden*/) &&
2798              "Expected to find the method through lookup as well");
2799       // ImpMethodDecl may be null as in a @dynamic property.
2800       if (ImpMethodDecl) {
2801         if (!WarnCategoryMethodImpl)
2802           WarnConflictingTypedMethods(ImpMethodDecl, I,
2803                                       isa<ObjCProtocolDecl>(CDecl));
2804         else if (!I->isPropertyAccessor())
2805           WarnExactTypedMethods(ImpMethodDecl, I, isa<ObjCProtocolDecl>(CDecl));
2806       }
2807     }
2808   }
2809 
2810   // Check and see if class methods in class interface have been
2811   // implemented in the implementation class. If so, their types match.
2812   for (auto *I : CDecl->class_methods()) {
2813     if (!ClsMapSeen.insert(I->getSelector()).second)
2814       continue;
2815     if (!I->isPropertyAccessor() &&
2816         !ClsMap.count(I->getSelector())) {
2817       if (ImmediateClass)
2818         WarnUndefinedMethod(*this, IMPDecl->getLocation(), I, IncompleteImpl,
2819                             diag::warn_undef_method_impl);
2820     } else {
2821       ObjCMethodDecl *ImpMethodDecl =
2822         IMPDecl->getClassMethod(I->getSelector());
2823       assert(CDecl->getClassMethod(I->getSelector(), true/*AllowHidden*/) &&
2824              "Expected to find the method through lookup as well");
2825       // ImpMethodDecl may be null as in a @dynamic property.
2826       if (ImpMethodDecl) {
2827         if (!WarnCategoryMethodImpl)
2828           WarnConflictingTypedMethods(ImpMethodDecl, I,
2829                                       isa<ObjCProtocolDecl>(CDecl));
2830         else if (!I->isPropertyAccessor())
2831           WarnExactTypedMethods(ImpMethodDecl, I, isa<ObjCProtocolDecl>(CDecl));
2832       }
2833     }
2834   }
2835 
2836   if (ObjCProtocolDecl *PD = dyn_cast<ObjCProtocolDecl> (CDecl)) {
2837     // Also, check for methods declared in protocols inherited by
2838     // this protocol.
2839     for (auto *PI : PD->protocols())
2840       MatchAllMethodDeclarations(InsMap, ClsMap, InsMapSeen, ClsMapSeen,
2841                                  IMPDecl, PI, IncompleteImpl, false,
2842                                  WarnCategoryMethodImpl);
2843   }
2844 
2845   if (ObjCInterfaceDecl *I = dyn_cast<ObjCInterfaceDecl> (CDecl)) {
2846     // when checking that methods in implementation match their declaration,
2847     // i.e. when WarnCategoryMethodImpl is false, check declarations in class
2848     // extension; as well as those in categories.
2849     if (!WarnCategoryMethodImpl) {
2850       for (auto *Cat : I->visible_categories())
2851         MatchAllMethodDeclarations(InsMap, ClsMap, InsMapSeen, ClsMapSeen,
2852                                    IMPDecl, Cat, IncompleteImpl,
2853                                    ImmediateClass && Cat->IsClassExtension(),
2854                                    WarnCategoryMethodImpl);
2855     } else {
2856       // Also methods in class extensions need be looked at next.
2857       for (auto *Ext : I->visible_extensions())
2858         MatchAllMethodDeclarations(InsMap, ClsMap, InsMapSeen, ClsMapSeen,
2859                                    IMPDecl, Ext, IncompleteImpl, false,
2860                                    WarnCategoryMethodImpl);
2861     }
2862 
2863     // Check for any implementation of a methods declared in protocol.
2864     for (auto *PI : I->all_referenced_protocols())
2865       MatchAllMethodDeclarations(InsMap, ClsMap, InsMapSeen, ClsMapSeen,
2866                                  IMPDecl, PI, IncompleteImpl, false,
2867                                  WarnCategoryMethodImpl);
2868 
2869     // FIXME. For now, we are not checking for extact match of methods
2870     // in category implementation and its primary class's super class.
2871     if (!WarnCategoryMethodImpl && I->getSuperClass())
2872       MatchAllMethodDeclarations(InsMap, ClsMap, InsMapSeen, ClsMapSeen,
2873                                  IMPDecl,
2874                                  I->getSuperClass(), IncompleteImpl, false);
2875   }
2876 }
2877 
2878 /// CheckCategoryVsClassMethodMatches - Checks that methods implemented in
2879 /// category matches with those implemented in its primary class and
2880 /// warns each time an exact match is found.
2881 void Sema::CheckCategoryVsClassMethodMatches(
2882                                   ObjCCategoryImplDecl *CatIMPDecl) {
2883   // Get category's primary class.
2884   ObjCCategoryDecl *CatDecl = CatIMPDecl->getCategoryDecl();
2885   if (!CatDecl)
2886     return;
2887   ObjCInterfaceDecl *IDecl = CatDecl->getClassInterface();
2888   if (!IDecl)
2889     return;
2890   ObjCInterfaceDecl *SuperIDecl = IDecl->getSuperClass();
2891   SelectorSet InsMap, ClsMap;
2892 
2893   for (const auto *I : CatIMPDecl->instance_methods()) {
2894     Selector Sel = I->getSelector();
2895     // When checking for methods implemented in the category, skip over
2896     // those declared in category class's super class. This is because
2897     // the super class must implement the method.
2898     if (SuperIDecl && SuperIDecl->lookupMethod(Sel, true))
2899       continue;
2900     InsMap.insert(Sel);
2901   }
2902 
2903   for (const auto *I : CatIMPDecl->class_methods()) {
2904     Selector Sel = I->getSelector();
2905     if (SuperIDecl && SuperIDecl->lookupMethod(Sel, false))
2906       continue;
2907     ClsMap.insert(Sel);
2908   }
2909   if (InsMap.empty() && ClsMap.empty())
2910     return;
2911 
2912   SelectorSet InsMapSeen, ClsMapSeen;
2913   bool IncompleteImpl = false;
2914   MatchAllMethodDeclarations(InsMap, ClsMap, InsMapSeen, ClsMapSeen,
2915                              CatIMPDecl, IDecl,
2916                              IncompleteImpl, false,
2917                              true /*WarnCategoryMethodImpl*/);
2918 }
2919 
2920 void Sema::ImplMethodsVsClassMethods(Scope *S, ObjCImplDecl* IMPDecl,
2921                                      ObjCContainerDecl* CDecl,
2922                                      bool IncompleteImpl) {
2923   SelectorSet InsMap;
2924   // Check and see if instance methods in class interface have been
2925   // implemented in the implementation class.
2926   for (const auto *I : IMPDecl->instance_methods())
2927     InsMap.insert(I->getSelector());
2928 
2929   // Add the selectors for getters/setters of @dynamic properties.
2930   for (const auto *PImpl : IMPDecl->property_impls()) {
2931     // We only care about @dynamic implementations.
2932     if (PImpl->getPropertyImplementation() != ObjCPropertyImplDecl::Dynamic)
2933       continue;
2934 
2935     const auto *P = PImpl->getPropertyDecl();
2936     if (!P) continue;
2937 
2938     InsMap.insert(P->getGetterName());
2939     if (!P->getSetterName().isNull())
2940       InsMap.insert(P->getSetterName());
2941   }
2942 
2943   // Check and see if properties declared in the interface have either 1)
2944   // an implementation or 2) there is a @synthesize/@dynamic implementation
2945   // of the property in the @implementation.
2946   if (const ObjCInterfaceDecl *IDecl = dyn_cast<ObjCInterfaceDecl>(CDecl)) {
2947     bool SynthesizeProperties = LangOpts.ObjCDefaultSynthProperties &&
2948                                 LangOpts.ObjCRuntime.isNonFragile() &&
2949                                 !IDecl->isObjCRequiresPropertyDefs();
2950     DiagnoseUnimplementedProperties(S, IMPDecl, CDecl, SynthesizeProperties);
2951   }
2952 
2953   // Diagnose null-resettable synthesized setters.
2954   diagnoseNullResettableSynthesizedSetters(IMPDecl);
2955 
2956   SelectorSet ClsMap;
2957   for (const auto *I : IMPDecl->class_methods())
2958     ClsMap.insert(I->getSelector());
2959 
2960   // Check for type conflict of methods declared in a class/protocol and
2961   // its implementation; if any.
2962   SelectorSet InsMapSeen, ClsMapSeen;
2963   MatchAllMethodDeclarations(InsMap, ClsMap, InsMapSeen, ClsMapSeen,
2964                              IMPDecl, CDecl,
2965                              IncompleteImpl, true);
2966 
2967   // check all methods implemented in category against those declared
2968   // in its primary class.
2969   if (ObjCCategoryImplDecl *CatDecl =
2970         dyn_cast<ObjCCategoryImplDecl>(IMPDecl))
2971     CheckCategoryVsClassMethodMatches(CatDecl);
2972 
2973   // Check the protocol list for unimplemented methods in the @implementation
2974   // class.
2975   // Check and see if class methods in class interface have been
2976   // implemented in the implementation class.
2977 
2978   LazyProtocolNameSet ExplicitImplProtocols;
2979 
2980   if (ObjCInterfaceDecl *I = dyn_cast<ObjCInterfaceDecl> (CDecl)) {
2981     for (auto *PI : I->all_referenced_protocols())
2982       CheckProtocolMethodDefs(*this, IMPDecl->getLocation(), PI, IncompleteImpl,
2983                               InsMap, ClsMap, I, ExplicitImplProtocols);
2984   } else if (ObjCCategoryDecl *C = dyn_cast<ObjCCategoryDecl>(CDecl)) {
2985     // For extended class, unimplemented methods in its protocols will
2986     // be reported in the primary class.
2987     if (!C->IsClassExtension()) {
2988       for (auto *P : C->protocols())
2989         CheckProtocolMethodDefs(*this, IMPDecl->getLocation(), P,
2990                                 IncompleteImpl, InsMap, ClsMap, CDecl,
2991                                 ExplicitImplProtocols);
2992       DiagnoseUnimplementedProperties(S, IMPDecl, CDecl,
2993                                       /*SynthesizeProperties=*/false);
2994     }
2995   } else
2996     llvm_unreachable("invalid ObjCContainerDecl type.");
2997 }
2998 
2999 Sema::DeclGroupPtrTy
3000 Sema::ActOnForwardClassDeclaration(SourceLocation AtClassLoc,
3001                                    IdentifierInfo **IdentList,
3002                                    SourceLocation *IdentLocs,
3003                                    ArrayRef<ObjCTypeParamList *> TypeParamLists,
3004                                    unsigned NumElts) {
3005   SmallVector<Decl *, 8> DeclsInGroup;
3006   for (unsigned i = 0; i != NumElts; ++i) {
3007     // Check for another declaration kind with the same name.
3008     NamedDecl *PrevDecl
3009       = LookupSingleName(TUScope, IdentList[i], IdentLocs[i],
3010                          LookupOrdinaryName, forRedeclarationInCurContext());
3011     if (PrevDecl && !isa<ObjCInterfaceDecl>(PrevDecl)) {
3012       // GCC apparently allows the following idiom:
3013       //
3014       // typedef NSObject < XCElementTogglerP > XCElementToggler;
3015       // @class XCElementToggler;
3016       //
3017       // Here we have chosen to ignore the forward class declaration
3018       // with a warning. Since this is the implied behavior.
3019       TypedefNameDecl *TDD = dyn_cast<TypedefNameDecl>(PrevDecl);
3020       if (!TDD || !TDD->getUnderlyingType()->isObjCObjectType()) {
3021         Diag(AtClassLoc, diag::err_redefinition_different_kind) << IdentList[i];
3022         Diag(PrevDecl->getLocation(), diag::note_previous_definition);
3023       } else {
3024         // a forward class declaration matching a typedef name of a class refers
3025         // to the underlying class. Just ignore the forward class with a warning
3026         // as this will force the intended behavior which is to lookup the
3027         // typedef name.
3028         if (isa<ObjCObjectType>(TDD->getUnderlyingType())) {
3029           Diag(AtClassLoc, diag::warn_forward_class_redefinition)
3030               << IdentList[i];
3031           Diag(PrevDecl->getLocation(), diag::note_previous_definition);
3032           continue;
3033         }
3034       }
3035     }
3036 
3037     // Create a declaration to describe this forward declaration.
3038     ObjCInterfaceDecl *PrevIDecl
3039       = dyn_cast_or_null<ObjCInterfaceDecl>(PrevDecl);
3040 
3041     IdentifierInfo *ClassName = IdentList[i];
3042     if (PrevIDecl && PrevIDecl->getIdentifier() != ClassName) {
3043       // A previous decl with a different name is because of
3044       // @compatibility_alias, for example:
3045       // \code
3046       //   @class NewImage;
3047       //   @compatibility_alias OldImage NewImage;
3048       // \endcode
3049       // A lookup for 'OldImage' will return the 'NewImage' decl.
3050       //
3051       // In such a case use the real declaration name, instead of the alias one,
3052       // otherwise we will break IdentifierResolver and redecls-chain invariants.
3053       // FIXME: If necessary, add a bit to indicate that this ObjCInterfaceDecl
3054       // has been aliased.
3055       ClassName = PrevIDecl->getIdentifier();
3056     }
3057 
3058     // If this forward declaration has type parameters, compare them with the
3059     // type parameters of the previous declaration.
3060     ObjCTypeParamList *TypeParams = TypeParamLists[i];
3061     if (PrevIDecl && TypeParams) {
3062       if (ObjCTypeParamList *PrevTypeParams = PrevIDecl->getTypeParamList()) {
3063         // Check for consistency with the previous declaration.
3064         if (checkTypeParamListConsistency(
3065               *this, PrevTypeParams, TypeParams,
3066               TypeParamListContext::ForwardDeclaration)) {
3067           TypeParams = nullptr;
3068         }
3069       } else if (ObjCInterfaceDecl *Def = PrevIDecl->getDefinition()) {
3070         // The @interface does not have type parameters. Complain.
3071         Diag(IdentLocs[i], diag::err_objc_parameterized_forward_class)
3072           << ClassName
3073           << TypeParams->getSourceRange();
3074         Diag(Def->getLocation(), diag::note_defined_here)
3075           << ClassName;
3076 
3077         TypeParams = nullptr;
3078       }
3079     }
3080 
3081     ObjCInterfaceDecl *IDecl
3082       = ObjCInterfaceDecl::Create(Context, CurContext, AtClassLoc,
3083                                   ClassName, TypeParams, PrevIDecl,
3084                                   IdentLocs[i]);
3085     IDecl->setAtEndRange(IdentLocs[i]);
3086 
3087     PushOnScopeChains(IDecl, TUScope);
3088     CheckObjCDeclScope(IDecl);
3089     DeclsInGroup.push_back(IDecl);
3090   }
3091 
3092   return BuildDeclaratorGroup(DeclsInGroup);
3093 }
3094 
3095 static bool tryMatchRecordTypes(ASTContext &Context,
3096                                 Sema::MethodMatchStrategy strategy,
3097                                 const Type *left, const Type *right);
3098 
3099 static bool matchTypes(ASTContext &Context, Sema::MethodMatchStrategy strategy,
3100                        QualType leftQT, QualType rightQT) {
3101   const Type *left =
3102     Context.getCanonicalType(leftQT).getUnqualifiedType().getTypePtr();
3103   const Type *right =
3104     Context.getCanonicalType(rightQT).getUnqualifiedType().getTypePtr();
3105 
3106   if (left == right) return true;
3107 
3108   // If we're doing a strict match, the types have to match exactly.
3109   if (strategy == Sema::MMS_strict) return false;
3110 
3111   if (left->isIncompleteType() || right->isIncompleteType()) return false;
3112 
3113   // Otherwise, use this absurdly complicated algorithm to try to
3114   // validate the basic, low-level compatibility of the two types.
3115 
3116   // As a minimum, require the sizes and alignments to match.
3117   TypeInfo LeftTI = Context.getTypeInfo(left);
3118   TypeInfo RightTI = Context.getTypeInfo(right);
3119   if (LeftTI.Width != RightTI.Width)
3120     return false;
3121 
3122   if (LeftTI.Align != RightTI.Align)
3123     return false;
3124 
3125   // Consider all the kinds of non-dependent canonical types:
3126   // - functions and arrays aren't possible as return and parameter types
3127 
3128   // - vector types of equal size can be arbitrarily mixed
3129   if (isa<VectorType>(left)) return isa<VectorType>(right);
3130   if (isa<VectorType>(right)) return false;
3131 
3132   // - references should only match references of identical type
3133   // - structs, unions, and Objective-C objects must match more-or-less
3134   //   exactly
3135   // - everything else should be a scalar
3136   if (!left->isScalarType() || !right->isScalarType())
3137     return tryMatchRecordTypes(Context, strategy, left, right);
3138 
3139   // Make scalars agree in kind, except count bools as chars, and group
3140   // all non-member pointers together.
3141   Type::ScalarTypeKind leftSK = left->getScalarTypeKind();
3142   Type::ScalarTypeKind rightSK = right->getScalarTypeKind();
3143   if (leftSK == Type::STK_Bool) leftSK = Type::STK_Integral;
3144   if (rightSK == Type::STK_Bool) rightSK = Type::STK_Integral;
3145   if (leftSK == Type::STK_CPointer || leftSK == Type::STK_BlockPointer)
3146     leftSK = Type::STK_ObjCObjectPointer;
3147   if (rightSK == Type::STK_CPointer || rightSK == Type::STK_BlockPointer)
3148     rightSK = Type::STK_ObjCObjectPointer;
3149 
3150   // Note that data member pointers and function member pointers don't
3151   // intermix because of the size differences.
3152 
3153   return (leftSK == rightSK);
3154 }
3155 
3156 static bool tryMatchRecordTypes(ASTContext &Context,
3157                                 Sema::MethodMatchStrategy strategy,
3158                                 const Type *lt, const Type *rt) {
3159   assert(lt && rt && lt != rt);
3160 
3161   if (!isa<RecordType>(lt) || !isa<RecordType>(rt)) return false;
3162   RecordDecl *left = cast<RecordType>(lt)->getDecl();
3163   RecordDecl *right = cast<RecordType>(rt)->getDecl();
3164 
3165   // Require union-hood to match.
3166   if (left->isUnion() != right->isUnion()) return false;
3167 
3168   // Require an exact match if either is non-POD.
3169   if ((isa<CXXRecordDecl>(left) && !cast<CXXRecordDecl>(left)->isPOD()) ||
3170       (isa<CXXRecordDecl>(right) && !cast<CXXRecordDecl>(right)->isPOD()))
3171     return false;
3172 
3173   // Require size and alignment to match.
3174   TypeInfo LeftTI = Context.getTypeInfo(lt);
3175   TypeInfo RightTI = Context.getTypeInfo(rt);
3176   if (LeftTI.Width != RightTI.Width)
3177     return false;
3178 
3179   if (LeftTI.Align != RightTI.Align)
3180     return false;
3181 
3182   // Require fields to match.
3183   RecordDecl::field_iterator li = left->field_begin(), le = left->field_end();
3184   RecordDecl::field_iterator ri = right->field_begin(), re = right->field_end();
3185   for (; li != le && ri != re; ++li, ++ri) {
3186     if (!matchTypes(Context, strategy, li->getType(), ri->getType()))
3187       return false;
3188   }
3189   return (li == le && ri == re);
3190 }
3191 
3192 /// MatchTwoMethodDeclarations - Checks that two methods have matching type and
3193 /// returns true, or false, accordingly.
3194 /// TODO: Handle protocol list; such as id<p1,p2> in type comparisons
3195 bool Sema::MatchTwoMethodDeclarations(const ObjCMethodDecl *left,
3196                                       const ObjCMethodDecl *right,
3197                                       MethodMatchStrategy strategy) {
3198   if (!matchTypes(Context, strategy, left->getReturnType(),
3199                   right->getReturnType()))
3200     return false;
3201 
3202   // If either is hidden, it is not considered to match.
3203   if (left->isHidden() || right->isHidden())
3204     return false;
3205 
3206   if (getLangOpts().ObjCAutoRefCount &&
3207       (left->hasAttr<NSReturnsRetainedAttr>()
3208          != right->hasAttr<NSReturnsRetainedAttr>() ||
3209        left->hasAttr<NSConsumesSelfAttr>()
3210          != right->hasAttr<NSConsumesSelfAttr>()))
3211     return false;
3212 
3213   ObjCMethodDecl::param_const_iterator
3214     li = left->param_begin(), le = left->param_end(), ri = right->param_begin(),
3215     re = right->param_end();
3216 
3217   for (; li != le && ri != re; ++li, ++ri) {
3218     assert(ri != right->param_end() && "Param mismatch");
3219     const ParmVarDecl *lparm = *li, *rparm = *ri;
3220 
3221     if (!matchTypes(Context, strategy, lparm->getType(), rparm->getType()))
3222       return false;
3223 
3224     if (getLangOpts().ObjCAutoRefCount &&
3225         lparm->hasAttr<NSConsumedAttr>() != rparm->hasAttr<NSConsumedAttr>())
3226       return false;
3227   }
3228   return true;
3229 }
3230 
3231 static bool isMethodContextSameForKindofLookup(ObjCMethodDecl *Method,
3232                                                ObjCMethodDecl *MethodInList) {
3233   auto *MethodProtocol = dyn_cast<ObjCProtocolDecl>(Method->getDeclContext());
3234   auto *MethodInListProtocol =
3235       dyn_cast<ObjCProtocolDecl>(MethodInList->getDeclContext());
3236   // If this method belongs to a protocol but the method in list does not, or
3237   // vice versa, we say the context is not the same.
3238   if ((MethodProtocol && !MethodInListProtocol) ||
3239       (!MethodProtocol && MethodInListProtocol))
3240     return false;
3241 
3242   if (MethodProtocol && MethodInListProtocol)
3243     return true;
3244 
3245   ObjCInterfaceDecl *MethodInterface = Method->getClassInterface();
3246   ObjCInterfaceDecl *MethodInListInterface =
3247       MethodInList->getClassInterface();
3248   return MethodInterface == MethodInListInterface;
3249 }
3250 
3251 void Sema::addMethodToGlobalList(ObjCMethodList *List,
3252                                  ObjCMethodDecl *Method) {
3253   // Record at the head of the list whether there were 0, 1, or >= 2 methods
3254   // inside categories.
3255   if (ObjCCategoryDecl *CD =
3256           dyn_cast<ObjCCategoryDecl>(Method->getDeclContext()))
3257     if (!CD->IsClassExtension() && List->getBits() < 2)
3258       List->setBits(List->getBits() + 1);
3259 
3260   // If the list is empty, make it a singleton list.
3261   if (List->getMethod() == nullptr) {
3262     List->setMethod(Method);
3263     List->setNext(nullptr);
3264     return;
3265   }
3266 
3267   // We've seen a method with this name, see if we have already seen this type
3268   // signature.
3269   ObjCMethodList *Previous = List;
3270   ObjCMethodList *ListWithSameDeclaration = nullptr;
3271   for (; List; Previous = List, List = List->getNext()) {
3272     // If we are building a module, keep all of the methods.
3273     if (getLangOpts().isCompilingModule())
3274       continue;
3275 
3276     bool SameDeclaration = MatchTwoMethodDeclarations(Method,
3277                                                       List->getMethod());
3278     // Looking for method with a type bound requires the correct context exists.
3279     // We need to insert a method into the list if the context is different.
3280     // If the method's declaration matches the list
3281     // a> the method belongs to a different context: we need to insert it, in
3282     //    order to emit the availability message, we need to prioritize over
3283     //    availability among the methods with the same declaration.
3284     // b> the method belongs to the same context: there is no need to insert a
3285     //    new entry.
3286     // If the method's declaration does not match the list, we insert it to the
3287     // end.
3288     if (!SameDeclaration ||
3289         !isMethodContextSameForKindofLookup(Method, List->getMethod())) {
3290       // Even if two method types do not match, we would like to say
3291       // there is more than one declaration so unavailability/deprecated
3292       // warning is not too noisy.
3293       if (!Method->isDefined())
3294         List->setHasMoreThanOneDecl(true);
3295 
3296       // For methods with the same declaration, the one that is deprecated
3297       // should be put in the front for better diagnostics.
3298       if (Method->isDeprecated() && SameDeclaration &&
3299           !ListWithSameDeclaration && !List->getMethod()->isDeprecated())
3300         ListWithSameDeclaration = List;
3301 
3302       if (Method->isUnavailable() && SameDeclaration &&
3303           !ListWithSameDeclaration &&
3304           List->getMethod()->getAvailability() < AR_Deprecated)
3305         ListWithSameDeclaration = List;
3306       continue;
3307     }
3308 
3309     ObjCMethodDecl *PrevObjCMethod = List->getMethod();
3310 
3311     // Propagate the 'defined' bit.
3312     if (Method->isDefined())
3313       PrevObjCMethod->setDefined(true);
3314     else {
3315       // Objective-C doesn't allow an @interface for a class after its
3316       // @implementation. So if Method is not defined and there already is
3317       // an entry for this type signature, Method has to be for a different
3318       // class than PrevObjCMethod.
3319       List->setHasMoreThanOneDecl(true);
3320     }
3321 
3322     // If a method is deprecated, push it in the global pool.
3323     // This is used for better diagnostics.
3324     if (Method->isDeprecated()) {
3325       if (!PrevObjCMethod->isDeprecated())
3326         List->setMethod(Method);
3327     }
3328     // If the new method is unavailable, push it into global pool
3329     // unless previous one is deprecated.
3330     if (Method->isUnavailable()) {
3331       if (PrevObjCMethod->getAvailability() < AR_Deprecated)
3332         List->setMethod(Method);
3333     }
3334 
3335     return;
3336   }
3337 
3338   // We have a new signature for an existing method - add it.
3339   // This is extremely rare. Only 1% of Cocoa selectors are "overloaded".
3340   ObjCMethodList *Mem = BumpAlloc.Allocate<ObjCMethodList>();
3341 
3342   // We insert it right before ListWithSameDeclaration.
3343   if (ListWithSameDeclaration) {
3344     auto *List = new (Mem) ObjCMethodList(*ListWithSameDeclaration);
3345     // FIXME: should we clear the other bits in ListWithSameDeclaration?
3346     ListWithSameDeclaration->setMethod(Method);
3347     ListWithSameDeclaration->setNext(List);
3348     return;
3349   }
3350 
3351   Previous->setNext(new (Mem) ObjCMethodList(Method));
3352 }
3353 
3354 /// \brief Read the contents of the method pool for a given selector from
3355 /// external storage.
3356 void Sema::ReadMethodPool(Selector Sel) {
3357   assert(ExternalSource && "We need an external AST source");
3358   ExternalSource->ReadMethodPool(Sel);
3359 }
3360 
3361 void Sema::updateOutOfDateSelector(Selector Sel) {
3362   if (!ExternalSource)
3363     return;
3364   ExternalSource->updateOutOfDateSelector(Sel);
3365 }
3366 
3367 void Sema::AddMethodToGlobalPool(ObjCMethodDecl *Method, bool impl,
3368                                  bool instance) {
3369   // Ignore methods of invalid containers.
3370   if (cast<Decl>(Method->getDeclContext())->isInvalidDecl())
3371     return;
3372 
3373   if (ExternalSource)
3374     ReadMethodPool(Method->getSelector());
3375 
3376   GlobalMethodPool::iterator Pos = MethodPool.find(Method->getSelector());
3377   if (Pos == MethodPool.end())
3378     Pos = MethodPool.insert(std::make_pair(Method->getSelector(),
3379                                            GlobalMethods())).first;
3380 
3381   Method->setDefined(impl);
3382 
3383   ObjCMethodList &Entry = instance ? Pos->second.first : Pos->second.second;
3384   addMethodToGlobalList(&Entry, Method);
3385 }
3386 
3387 /// Determines if this is an "acceptable" loose mismatch in the global
3388 /// method pool.  This exists mostly as a hack to get around certain
3389 /// global mismatches which we can't afford to make warnings / errors.
3390 /// Really, what we want is a way to take a method out of the global
3391 /// method pool.
3392 static bool isAcceptableMethodMismatch(ObjCMethodDecl *chosen,
3393                                        ObjCMethodDecl *other) {
3394   if (!chosen->isInstanceMethod())
3395     return false;
3396 
3397   Selector sel = chosen->getSelector();
3398   if (!sel.isUnarySelector() || sel.getNameForSlot(0) != "length")
3399     return false;
3400 
3401   // Don't complain about mismatches for -length if the method we
3402   // chose has an integral result type.
3403   return (chosen->getReturnType()->isIntegerType());
3404 }
3405 
3406 /// Return true if the given method is wthin the type bound.
3407 static bool FilterMethodsByTypeBound(ObjCMethodDecl *Method,
3408                                      const ObjCObjectType *TypeBound) {
3409   if (!TypeBound)
3410     return true;
3411 
3412   if (TypeBound->isObjCId())
3413     // FIXME: should we handle the case of bounding to id<A, B> differently?
3414     return true;
3415 
3416   auto *BoundInterface = TypeBound->getInterface();
3417   assert(BoundInterface && "unexpected object type!");
3418 
3419   // Check if the Method belongs to a protocol. We should allow any method
3420   // defined in any protocol, because any subclass could adopt the protocol.
3421   auto *MethodProtocol = dyn_cast<ObjCProtocolDecl>(Method->getDeclContext());
3422   if (MethodProtocol) {
3423     return true;
3424   }
3425 
3426   // If the Method belongs to a class, check if it belongs to the class
3427   // hierarchy of the class bound.
3428   if (ObjCInterfaceDecl *MethodInterface = Method->getClassInterface()) {
3429     // We allow methods declared within classes that are part of the hierarchy
3430     // of the class bound (superclass of, subclass of, or the same as the class
3431     // bound).
3432     return MethodInterface == BoundInterface ||
3433            MethodInterface->isSuperClassOf(BoundInterface) ||
3434            BoundInterface->isSuperClassOf(MethodInterface);
3435   }
3436   llvm_unreachable("unknow method context");
3437 }
3438 
3439 /// We first select the type of the method: Instance or Factory, then collect
3440 /// all methods with that type.
3441 bool Sema::CollectMultipleMethodsInGlobalPool(
3442     Selector Sel, SmallVectorImpl<ObjCMethodDecl *> &Methods,
3443     bool InstanceFirst, bool CheckTheOther,
3444     const ObjCObjectType *TypeBound) {
3445   if (ExternalSource)
3446     ReadMethodPool(Sel);
3447 
3448   GlobalMethodPool::iterator Pos = MethodPool.find(Sel);
3449   if (Pos == MethodPool.end())
3450     return false;
3451 
3452   // Gather the non-hidden methods.
3453   ObjCMethodList &MethList = InstanceFirst ? Pos->second.first :
3454                              Pos->second.second;
3455   for (ObjCMethodList *M = &MethList; M; M = M->getNext())
3456     if (M->getMethod() && !M->getMethod()->isHidden()) {
3457       if (FilterMethodsByTypeBound(M->getMethod(), TypeBound))
3458         Methods.push_back(M->getMethod());
3459     }
3460 
3461   // Return if we find any method with the desired kind.
3462   if (!Methods.empty())
3463     return Methods.size() > 1;
3464 
3465   if (!CheckTheOther)
3466     return false;
3467 
3468   // Gather the other kind.
3469   ObjCMethodList &MethList2 = InstanceFirst ? Pos->second.second :
3470                               Pos->second.first;
3471   for (ObjCMethodList *M = &MethList2; M; M = M->getNext())
3472     if (M->getMethod() && !M->getMethod()->isHidden()) {
3473       if (FilterMethodsByTypeBound(M->getMethod(), TypeBound))
3474         Methods.push_back(M->getMethod());
3475     }
3476 
3477   return Methods.size() > 1;
3478 }
3479 
3480 bool Sema::AreMultipleMethodsInGlobalPool(
3481     Selector Sel, ObjCMethodDecl *BestMethod, SourceRange R,
3482     bool receiverIdOrClass, SmallVectorImpl<ObjCMethodDecl *> &Methods) {
3483   // Diagnose finding more than one method in global pool.
3484   SmallVector<ObjCMethodDecl *, 4> FilteredMethods;
3485   FilteredMethods.push_back(BestMethod);
3486 
3487   for (auto *M : Methods)
3488     if (M != BestMethod && !M->hasAttr<UnavailableAttr>())
3489       FilteredMethods.push_back(M);
3490 
3491   if (FilteredMethods.size() > 1)
3492     DiagnoseMultipleMethodInGlobalPool(FilteredMethods, Sel, R,
3493                                        receiverIdOrClass);
3494 
3495   GlobalMethodPool::iterator Pos = MethodPool.find(Sel);
3496   // Test for no method in the pool which should not trigger any warning by
3497   // caller.
3498   if (Pos == MethodPool.end())
3499     return true;
3500   ObjCMethodList &MethList =
3501     BestMethod->isInstanceMethod() ? Pos->second.first : Pos->second.second;
3502   return MethList.hasMoreThanOneDecl();
3503 }
3504 
3505 ObjCMethodDecl *Sema::LookupMethodInGlobalPool(Selector Sel, SourceRange R,
3506                                                bool receiverIdOrClass,
3507                                                bool instance) {
3508   if (ExternalSource)
3509     ReadMethodPool(Sel);
3510 
3511   GlobalMethodPool::iterator Pos = MethodPool.find(Sel);
3512   if (Pos == MethodPool.end())
3513     return nullptr;
3514 
3515   // Gather the non-hidden methods.
3516   ObjCMethodList &MethList = instance ? Pos->second.first : Pos->second.second;
3517   SmallVector<ObjCMethodDecl *, 4> Methods;
3518   for (ObjCMethodList *M = &MethList; M; M = M->getNext()) {
3519     if (M->getMethod() && !M->getMethod()->isHidden())
3520       return M->getMethod();
3521   }
3522   return nullptr;
3523 }
3524 
3525 void Sema::DiagnoseMultipleMethodInGlobalPool(SmallVectorImpl<ObjCMethodDecl*> &Methods,
3526                                               Selector Sel, SourceRange R,
3527                                               bool receiverIdOrClass) {
3528   // We found multiple methods, so we may have to complain.
3529   bool issueDiagnostic = false, issueError = false;
3530 
3531   // We support a warning which complains about *any* difference in
3532   // method signature.
3533   bool strictSelectorMatch =
3534   receiverIdOrClass &&
3535   !Diags.isIgnored(diag::warn_strict_multiple_method_decl, R.getBegin());
3536   if (strictSelectorMatch) {
3537     for (unsigned I = 1, N = Methods.size(); I != N; ++I) {
3538       if (!MatchTwoMethodDeclarations(Methods[0], Methods[I], MMS_strict)) {
3539         issueDiagnostic = true;
3540         break;
3541       }
3542     }
3543   }
3544 
3545   // If we didn't see any strict differences, we won't see any loose
3546   // differences.  In ARC, however, we also need to check for loose
3547   // mismatches, because most of them are errors.
3548   if (!strictSelectorMatch ||
3549       (issueDiagnostic && getLangOpts().ObjCAutoRefCount))
3550     for (unsigned I = 1, N = Methods.size(); I != N; ++I) {
3551       // This checks if the methods differ in type mismatch.
3552       if (!MatchTwoMethodDeclarations(Methods[0], Methods[I], MMS_loose) &&
3553           !isAcceptableMethodMismatch(Methods[0], Methods[I])) {
3554         issueDiagnostic = true;
3555         if (getLangOpts().ObjCAutoRefCount)
3556           issueError = true;
3557         break;
3558       }
3559     }
3560 
3561   if (issueDiagnostic) {
3562     if (issueError)
3563       Diag(R.getBegin(), diag::err_arc_multiple_method_decl) << Sel << R;
3564     else if (strictSelectorMatch)
3565       Diag(R.getBegin(), diag::warn_strict_multiple_method_decl) << Sel << R;
3566     else
3567       Diag(R.getBegin(), diag::warn_multiple_method_decl) << Sel << R;
3568 
3569     Diag(Methods[0]->getLocStart(),
3570          issueError ? diag::note_possibility : diag::note_using)
3571     << Methods[0]->getSourceRange();
3572     for (unsigned I = 1, N = Methods.size(); I != N; ++I) {
3573       Diag(Methods[I]->getLocStart(), diag::note_also_found)
3574       << Methods[I]->getSourceRange();
3575     }
3576   }
3577 }
3578 
3579 ObjCMethodDecl *Sema::LookupImplementedMethodInGlobalPool(Selector Sel) {
3580   GlobalMethodPool::iterator Pos = MethodPool.find(Sel);
3581   if (Pos == MethodPool.end())
3582     return nullptr;
3583 
3584   GlobalMethods &Methods = Pos->second;
3585   for (const ObjCMethodList *Method = &Methods.first; Method;
3586        Method = Method->getNext())
3587     if (Method->getMethod() &&
3588         (Method->getMethod()->isDefined() ||
3589          Method->getMethod()->isPropertyAccessor()))
3590       return Method->getMethod();
3591 
3592   for (const ObjCMethodList *Method = &Methods.second; Method;
3593        Method = Method->getNext())
3594     if (Method->getMethod() &&
3595         (Method->getMethod()->isDefined() ||
3596          Method->getMethod()->isPropertyAccessor()))
3597       return Method->getMethod();
3598   return nullptr;
3599 }
3600 
3601 static void
3602 HelperSelectorsForTypoCorrection(
3603                       SmallVectorImpl<const ObjCMethodDecl *> &BestMethod,
3604                       StringRef Typo, const ObjCMethodDecl * Method) {
3605   const unsigned MaxEditDistance = 1;
3606   unsigned BestEditDistance = MaxEditDistance + 1;
3607   std::string MethodName = Method->getSelector().getAsString();
3608 
3609   unsigned MinPossibleEditDistance = abs((int)MethodName.size() - (int)Typo.size());
3610   if (MinPossibleEditDistance > 0 &&
3611       Typo.size() / MinPossibleEditDistance < 1)
3612     return;
3613   unsigned EditDistance = Typo.edit_distance(MethodName, true, MaxEditDistance);
3614   if (EditDistance > MaxEditDistance)
3615     return;
3616   if (EditDistance == BestEditDistance)
3617     BestMethod.push_back(Method);
3618   else if (EditDistance < BestEditDistance) {
3619     BestMethod.clear();
3620     BestMethod.push_back(Method);
3621   }
3622 }
3623 
3624 static bool HelperIsMethodInObjCType(Sema &S, Selector Sel,
3625                                      QualType ObjectType) {
3626   if (ObjectType.isNull())
3627     return true;
3628   if (S.LookupMethodInObjectType(Sel, ObjectType, true/*Instance method*/))
3629     return true;
3630   return S.LookupMethodInObjectType(Sel, ObjectType, false/*Class method*/) !=
3631          nullptr;
3632 }
3633 
3634 const ObjCMethodDecl *
3635 Sema::SelectorsForTypoCorrection(Selector Sel,
3636                                  QualType ObjectType) {
3637   unsigned NumArgs = Sel.getNumArgs();
3638   SmallVector<const ObjCMethodDecl *, 8> Methods;
3639   bool ObjectIsId = true, ObjectIsClass = true;
3640   if (ObjectType.isNull())
3641     ObjectIsId = ObjectIsClass = false;
3642   else if (!ObjectType->isObjCObjectPointerType())
3643     return nullptr;
3644   else if (const ObjCObjectPointerType *ObjCPtr =
3645            ObjectType->getAsObjCInterfacePointerType()) {
3646     ObjectType = QualType(ObjCPtr->getInterfaceType(), 0);
3647     ObjectIsId = ObjectIsClass = false;
3648   }
3649   else if (ObjectType->isObjCIdType() || ObjectType->isObjCQualifiedIdType())
3650     ObjectIsClass = false;
3651   else if (ObjectType->isObjCClassType() || ObjectType->isObjCQualifiedClassType())
3652     ObjectIsId = false;
3653   else
3654     return nullptr;
3655 
3656   for (GlobalMethodPool::iterator b = MethodPool.begin(),
3657        e = MethodPool.end(); b != e; b++) {
3658     // instance methods
3659     for (ObjCMethodList *M = &b->second.first; M; M=M->getNext())
3660       if (M->getMethod() &&
3661           (M->getMethod()->getSelector().getNumArgs() == NumArgs) &&
3662           (M->getMethod()->getSelector() != Sel)) {
3663         if (ObjectIsId)
3664           Methods.push_back(M->getMethod());
3665         else if (!ObjectIsClass &&
3666                  HelperIsMethodInObjCType(*this, M->getMethod()->getSelector(),
3667                                           ObjectType))
3668           Methods.push_back(M->getMethod());
3669       }
3670     // class methods
3671     for (ObjCMethodList *M = &b->second.second; M; M=M->getNext())
3672       if (M->getMethod() &&
3673           (M->getMethod()->getSelector().getNumArgs() == NumArgs) &&
3674           (M->getMethod()->getSelector() != Sel)) {
3675         if (ObjectIsClass)
3676           Methods.push_back(M->getMethod());
3677         else if (!ObjectIsId &&
3678                  HelperIsMethodInObjCType(*this, M->getMethod()->getSelector(),
3679                                           ObjectType))
3680           Methods.push_back(M->getMethod());
3681       }
3682   }
3683 
3684   SmallVector<const ObjCMethodDecl *, 8> SelectedMethods;
3685   for (unsigned i = 0, e = Methods.size(); i < e; i++) {
3686     HelperSelectorsForTypoCorrection(SelectedMethods,
3687                                      Sel.getAsString(), Methods[i]);
3688   }
3689   return (SelectedMethods.size() == 1) ? SelectedMethods[0] : nullptr;
3690 }
3691 
3692 /// DiagnoseDuplicateIvars -
3693 /// Check for duplicate ivars in the entire class at the start of
3694 /// \@implementation. This becomes necesssary because class extension can
3695 /// add ivars to a class in random order which will not be known until
3696 /// class's \@implementation is seen.
3697 void Sema::DiagnoseDuplicateIvars(ObjCInterfaceDecl *ID,
3698                                   ObjCInterfaceDecl *SID) {
3699   for (auto *Ivar : ID->ivars()) {
3700     if (Ivar->isInvalidDecl())
3701       continue;
3702     if (IdentifierInfo *II = Ivar->getIdentifier()) {
3703       ObjCIvarDecl* prevIvar = SID->lookupInstanceVariable(II);
3704       if (prevIvar) {
3705         Diag(Ivar->getLocation(), diag::err_duplicate_member) << II;
3706         Diag(prevIvar->getLocation(), diag::note_previous_declaration);
3707         Ivar->setInvalidDecl();
3708       }
3709     }
3710   }
3711 }
3712 
3713 /// Diagnose attempts to define ARC-__weak ivars when __weak is disabled.
3714 static void DiagnoseWeakIvars(Sema &S, ObjCImplementationDecl *ID) {
3715   if (S.getLangOpts().ObjCWeak) return;
3716 
3717   for (auto ivar = ID->getClassInterface()->all_declared_ivar_begin();
3718          ivar; ivar = ivar->getNextIvar()) {
3719     if (ivar->isInvalidDecl()) continue;
3720     if (ivar->getType().getObjCLifetime() == Qualifiers::OCL_Weak) {
3721       if (S.getLangOpts().ObjCWeakRuntime) {
3722         S.Diag(ivar->getLocation(), diag::err_arc_weak_disabled);
3723       } else {
3724         S.Diag(ivar->getLocation(), diag::err_arc_weak_no_runtime);
3725       }
3726     }
3727   }
3728 }
3729 
3730 /// Diagnose attempts to use flexible array member with retainable object type.
3731 static void DiagnoseRetainableFlexibleArrayMember(Sema &S,
3732                                                   ObjCInterfaceDecl *ID) {
3733   if (!S.getLangOpts().ObjCAutoRefCount)
3734     return;
3735 
3736   for (auto ivar = ID->all_declared_ivar_begin(); ivar;
3737        ivar = ivar->getNextIvar()) {
3738     if (ivar->isInvalidDecl())
3739       continue;
3740     QualType IvarTy = ivar->getType();
3741     if (IvarTy->isIncompleteArrayType() &&
3742         (IvarTy.getObjCLifetime() != Qualifiers::OCL_ExplicitNone) &&
3743         IvarTy->isObjCLifetimeType()) {
3744       S.Diag(ivar->getLocation(), diag::err_flexible_array_arc_retainable);
3745       ivar->setInvalidDecl();
3746     }
3747   }
3748 }
3749 
3750 Sema::ObjCContainerKind Sema::getObjCContainerKind() const {
3751   switch (CurContext->getDeclKind()) {
3752     case Decl::ObjCInterface:
3753       return Sema::OCK_Interface;
3754     case Decl::ObjCProtocol:
3755       return Sema::OCK_Protocol;
3756     case Decl::ObjCCategory:
3757       if (cast<ObjCCategoryDecl>(CurContext)->IsClassExtension())
3758         return Sema::OCK_ClassExtension;
3759       return Sema::OCK_Category;
3760     case Decl::ObjCImplementation:
3761       return Sema::OCK_Implementation;
3762     case Decl::ObjCCategoryImpl:
3763       return Sema::OCK_CategoryImplementation;
3764 
3765     default:
3766       return Sema::OCK_None;
3767   }
3768 }
3769 
3770 static bool IsVariableSizedType(QualType T) {
3771   if (T->isIncompleteArrayType())
3772     return true;
3773   const auto *RecordTy = T->getAs<RecordType>();
3774   return (RecordTy && RecordTy->getDecl()->hasFlexibleArrayMember());
3775 }
3776 
3777 static void DiagnoseVariableSizedIvars(Sema &S, ObjCContainerDecl *OCD) {
3778   ObjCInterfaceDecl *IntfDecl = nullptr;
3779   ObjCInterfaceDecl::ivar_range Ivars = llvm::make_range(
3780       ObjCInterfaceDecl::ivar_iterator(), ObjCInterfaceDecl::ivar_iterator());
3781   if ((IntfDecl = dyn_cast<ObjCInterfaceDecl>(OCD))) {
3782     Ivars = IntfDecl->ivars();
3783   } else if (auto *ImplDecl = dyn_cast<ObjCImplementationDecl>(OCD)) {
3784     IntfDecl = ImplDecl->getClassInterface();
3785     Ivars = ImplDecl->ivars();
3786   } else if (auto *CategoryDecl = dyn_cast<ObjCCategoryDecl>(OCD)) {
3787     if (CategoryDecl->IsClassExtension()) {
3788       IntfDecl = CategoryDecl->getClassInterface();
3789       Ivars = CategoryDecl->ivars();
3790     }
3791   }
3792 
3793   // Check if variable sized ivar is in interface and visible to subclasses.
3794   if (!isa<ObjCInterfaceDecl>(OCD)) {
3795     for (auto ivar : Ivars) {
3796       if (!ivar->isInvalidDecl() && IsVariableSizedType(ivar->getType())) {
3797         S.Diag(ivar->getLocation(), diag::warn_variable_sized_ivar_visibility)
3798             << ivar->getDeclName() << ivar->getType();
3799       }
3800     }
3801   }
3802 
3803   // Subsequent checks require interface decl.
3804   if (!IntfDecl)
3805     return;
3806 
3807   // Check if variable sized ivar is followed by another ivar.
3808   for (ObjCIvarDecl *ivar = IntfDecl->all_declared_ivar_begin(); ivar;
3809        ivar = ivar->getNextIvar()) {
3810     if (ivar->isInvalidDecl() || !ivar->getNextIvar())
3811       continue;
3812     QualType IvarTy = ivar->getType();
3813     bool IsInvalidIvar = false;
3814     if (IvarTy->isIncompleteArrayType()) {
3815       S.Diag(ivar->getLocation(), diag::err_flexible_array_not_at_end)
3816           << ivar->getDeclName() << IvarTy
3817           << TTK_Class; // Use "class" for Obj-C.
3818       IsInvalidIvar = true;
3819     } else if (const RecordType *RecordTy = IvarTy->getAs<RecordType>()) {
3820       if (RecordTy->getDecl()->hasFlexibleArrayMember()) {
3821         S.Diag(ivar->getLocation(),
3822                diag::err_objc_variable_sized_type_not_at_end)
3823             << ivar->getDeclName() << IvarTy;
3824         IsInvalidIvar = true;
3825       }
3826     }
3827     if (IsInvalidIvar) {
3828       S.Diag(ivar->getNextIvar()->getLocation(),
3829              diag::note_next_ivar_declaration)
3830           << ivar->getNextIvar()->getSynthesize();
3831       ivar->setInvalidDecl();
3832     }
3833   }
3834 
3835   // Check if ObjC container adds ivars after variable sized ivar in superclass.
3836   // Perform the check only if OCD is the first container to declare ivars to
3837   // avoid multiple warnings for the same ivar.
3838   ObjCIvarDecl *FirstIvar =
3839       (Ivars.begin() == Ivars.end()) ? nullptr : *Ivars.begin();
3840   if (FirstIvar && (FirstIvar == IntfDecl->all_declared_ivar_begin())) {
3841     const ObjCInterfaceDecl *SuperClass = IntfDecl->getSuperClass();
3842     while (SuperClass && SuperClass->ivar_empty())
3843       SuperClass = SuperClass->getSuperClass();
3844     if (SuperClass) {
3845       auto IvarIter = SuperClass->ivar_begin();
3846       std::advance(IvarIter, SuperClass->ivar_size() - 1);
3847       const ObjCIvarDecl *LastIvar = *IvarIter;
3848       if (IsVariableSizedType(LastIvar->getType())) {
3849         S.Diag(FirstIvar->getLocation(),
3850                diag::warn_superclass_variable_sized_type_not_at_end)
3851             << FirstIvar->getDeclName() << LastIvar->getDeclName()
3852             << LastIvar->getType() << SuperClass->getDeclName();
3853         S.Diag(LastIvar->getLocation(), diag::note_entity_declared_at)
3854             << LastIvar->getDeclName();
3855       }
3856     }
3857   }
3858 }
3859 
3860 // Note: For class/category implementations, allMethods is always null.
3861 Decl *Sema::ActOnAtEnd(Scope *S, SourceRange AtEnd, ArrayRef<Decl *> allMethods,
3862                        ArrayRef<DeclGroupPtrTy> allTUVars) {
3863   if (getObjCContainerKind() == Sema::OCK_None)
3864     return nullptr;
3865 
3866   assert(AtEnd.isValid() && "Invalid location for '@end'");
3867 
3868   auto *OCD = cast<ObjCContainerDecl>(CurContext);
3869   Decl *ClassDecl = OCD;
3870 
3871   bool isInterfaceDeclKind =
3872         isa<ObjCInterfaceDecl>(ClassDecl) || isa<ObjCCategoryDecl>(ClassDecl)
3873          || isa<ObjCProtocolDecl>(ClassDecl);
3874   bool checkIdenticalMethods = isa<ObjCImplementationDecl>(ClassDecl);
3875 
3876   // FIXME: Remove these and use the ObjCContainerDecl/DeclContext.
3877   llvm::DenseMap<Selector, const ObjCMethodDecl*> InsMap;
3878   llvm::DenseMap<Selector, const ObjCMethodDecl*> ClsMap;
3879 
3880   for (unsigned i = 0, e = allMethods.size(); i != e; i++ ) {
3881     ObjCMethodDecl *Method =
3882       cast_or_null<ObjCMethodDecl>(allMethods[i]);
3883 
3884     if (!Method) continue;  // Already issued a diagnostic.
3885     if (Method->isInstanceMethod()) {
3886       /// Check for instance method of the same name with incompatible types
3887       const ObjCMethodDecl *&PrevMethod = InsMap[Method->getSelector()];
3888       bool match = PrevMethod ? MatchTwoMethodDeclarations(Method, PrevMethod)
3889                               : false;
3890       if ((isInterfaceDeclKind && PrevMethod && !match)
3891           || (checkIdenticalMethods && match)) {
3892           Diag(Method->getLocation(), diag::err_duplicate_method_decl)
3893             << Method->getDeclName();
3894           Diag(PrevMethod->getLocation(), diag::note_previous_declaration);
3895         Method->setInvalidDecl();
3896       } else {
3897         if (PrevMethod) {
3898           Method->setAsRedeclaration(PrevMethod);
3899           if (!Context.getSourceManager().isInSystemHeader(
3900                  Method->getLocation()))
3901             Diag(Method->getLocation(), diag::warn_duplicate_method_decl)
3902               << Method->getDeclName();
3903           Diag(PrevMethod->getLocation(), diag::note_previous_declaration);
3904         }
3905         InsMap[Method->getSelector()] = Method;
3906         /// The following allows us to typecheck messages to "id".
3907         AddInstanceMethodToGlobalPool(Method);
3908       }
3909     } else {
3910       /// Check for class method of the same name with incompatible types
3911       const ObjCMethodDecl *&PrevMethod = ClsMap[Method->getSelector()];
3912       bool match = PrevMethod ? MatchTwoMethodDeclarations(Method, PrevMethod)
3913                               : false;
3914       if ((isInterfaceDeclKind && PrevMethod && !match)
3915           || (checkIdenticalMethods && match)) {
3916         Diag(Method->getLocation(), diag::err_duplicate_method_decl)
3917           << Method->getDeclName();
3918         Diag(PrevMethod->getLocation(), diag::note_previous_declaration);
3919         Method->setInvalidDecl();
3920       } else {
3921         if (PrevMethod) {
3922           Method->setAsRedeclaration(PrevMethod);
3923           if (!Context.getSourceManager().isInSystemHeader(
3924                  Method->getLocation()))
3925             Diag(Method->getLocation(), diag::warn_duplicate_method_decl)
3926               << Method->getDeclName();
3927           Diag(PrevMethod->getLocation(), diag::note_previous_declaration);
3928         }
3929         ClsMap[Method->getSelector()] = Method;
3930         AddFactoryMethodToGlobalPool(Method);
3931       }
3932     }
3933   }
3934   if (isa<ObjCInterfaceDecl>(ClassDecl)) {
3935     // Nothing to do here.
3936   } else if (ObjCCategoryDecl *C = dyn_cast<ObjCCategoryDecl>(ClassDecl)) {
3937     // Categories are used to extend the class by declaring new methods.
3938     // By the same token, they are also used to add new properties. No
3939     // need to compare the added property to those in the class.
3940 
3941     if (C->IsClassExtension()) {
3942       ObjCInterfaceDecl *CCPrimary = C->getClassInterface();
3943       DiagnoseClassExtensionDupMethods(C, CCPrimary);
3944     }
3945   }
3946   if (ObjCContainerDecl *CDecl = dyn_cast<ObjCContainerDecl>(ClassDecl)) {
3947     if (CDecl->getIdentifier())
3948       // ProcessPropertyDecl is responsible for diagnosing conflicts with any
3949       // user-defined setter/getter. It also synthesizes setter/getter methods
3950       // and adds them to the DeclContext and global method pools.
3951       for (auto *I : CDecl->properties())
3952         ProcessPropertyDecl(I);
3953     CDecl->setAtEndRange(AtEnd);
3954   }
3955   if (ObjCImplementationDecl *IC=dyn_cast<ObjCImplementationDecl>(ClassDecl)) {
3956     IC->setAtEndRange(AtEnd);
3957     if (ObjCInterfaceDecl* IDecl = IC->getClassInterface()) {
3958       // Any property declared in a class extension might have user
3959       // declared setter or getter in current class extension or one
3960       // of the other class extensions. Mark them as synthesized as
3961       // property will be synthesized when property with same name is
3962       // seen in the @implementation.
3963       for (const auto *Ext : IDecl->visible_extensions()) {
3964         for (const auto *Property : Ext->instance_properties()) {
3965           // Skip over properties declared @dynamic
3966           if (const ObjCPropertyImplDecl *PIDecl
3967               = IC->FindPropertyImplDecl(Property->getIdentifier(),
3968                                          Property->getQueryKind()))
3969             if (PIDecl->getPropertyImplementation()
3970                   == ObjCPropertyImplDecl::Dynamic)
3971               continue;
3972 
3973           for (const auto *Ext : IDecl->visible_extensions()) {
3974             if (ObjCMethodDecl *GetterMethod
3975                   = Ext->getInstanceMethod(Property->getGetterName()))
3976               GetterMethod->setPropertyAccessor(true);
3977             if (!Property->isReadOnly())
3978               if (ObjCMethodDecl *SetterMethod
3979                     = Ext->getInstanceMethod(Property->getSetterName()))
3980                 SetterMethod->setPropertyAccessor(true);
3981           }
3982         }
3983       }
3984       ImplMethodsVsClassMethods(S, IC, IDecl);
3985       AtomicPropertySetterGetterRules(IC, IDecl);
3986       DiagnoseOwningPropertyGetterSynthesis(IC);
3987       DiagnoseUnusedBackingIvarInAccessor(S, IC);
3988       if (IDecl->hasDesignatedInitializers())
3989         DiagnoseMissingDesignatedInitOverrides(IC, IDecl);
3990       DiagnoseWeakIvars(*this, IC);
3991       DiagnoseRetainableFlexibleArrayMember(*this, IDecl);
3992 
3993       bool HasRootClassAttr = IDecl->hasAttr<ObjCRootClassAttr>();
3994       if (IDecl->getSuperClass() == nullptr) {
3995         // This class has no superclass, so check that it has been marked with
3996         // __attribute((objc_root_class)).
3997         if (!HasRootClassAttr) {
3998           SourceLocation DeclLoc(IDecl->getLocation());
3999           SourceLocation SuperClassLoc(getLocForEndOfToken(DeclLoc));
4000           Diag(DeclLoc, diag::warn_objc_root_class_missing)
4001             << IDecl->getIdentifier();
4002           // See if NSObject is in the current scope, and if it is, suggest
4003           // adding " : NSObject " to the class declaration.
4004           NamedDecl *IF = LookupSingleName(TUScope,
4005                                            NSAPIObj->getNSClassId(NSAPI::ClassId_NSObject),
4006                                            DeclLoc, LookupOrdinaryName);
4007           ObjCInterfaceDecl *NSObjectDecl = dyn_cast_or_null<ObjCInterfaceDecl>(IF);
4008           if (NSObjectDecl && NSObjectDecl->getDefinition()) {
4009             Diag(SuperClassLoc, diag::note_objc_needs_superclass)
4010               << FixItHint::CreateInsertion(SuperClassLoc, " : NSObject ");
4011           } else {
4012             Diag(SuperClassLoc, diag::note_objc_needs_superclass);
4013           }
4014         }
4015       } else if (HasRootClassAttr) {
4016         // Complain that only root classes may have this attribute.
4017         Diag(IDecl->getLocation(), diag::err_objc_root_class_subclass);
4018       }
4019 
4020       if (const ObjCInterfaceDecl *Super = IDecl->getSuperClass()) {
4021         // An interface can subclass another interface with a
4022         // objc_subclassing_restricted attribute when it has that attribute as
4023         // well (because of interfaces imported from Swift). Therefore we have
4024         // to check if we can subclass in the implementation as well.
4025         if (IDecl->hasAttr<ObjCSubclassingRestrictedAttr>() &&
4026             Super->hasAttr<ObjCSubclassingRestrictedAttr>()) {
4027           Diag(IC->getLocation(), diag::err_restricted_superclass_mismatch);
4028           Diag(Super->getLocation(), diag::note_class_declared);
4029         }
4030       }
4031 
4032       if (LangOpts.ObjCRuntime.isNonFragile()) {
4033         while (IDecl->getSuperClass()) {
4034           DiagnoseDuplicateIvars(IDecl, IDecl->getSuperClass());
4035           IDecl = IDecl->getSuperClass();
4036         }
4037       }
4038     }
4039     SetIvarInitializers(IC);
4040   } else if (ObjCCategoryImplDecl* CatImplClass =
4041                                    dyn_cast<ObjCCategoryImplDecl>(ClassDecl)) {
4042     CatImplClass->setAtEndRange(AtEnd);
4043 
4044     // Find category interface decl and then check that all methods declared
4045     // in this interface are implemented in the category @implementation.
4046     if (ObjCInterfaceDecl* IDecl = CatImplClass->getClassInterface()) {
4047       if (ObjCCategoryDecl *Cat
4048             = IDecl->FindCategoryDeclaration(CatImplClass->getIdentifier())) {
4049         ImplMethodsVsClassMethods(S, CatImplClass, Cat);
4050       }
4051     }
4052   } else if (const auto *IntfDecl = dyn_cast<ObjCInterfaceDecl>(ClassDecl)) {
4053     if (const ObjCInterfaceDecl *Super = IntfDecl->getSuperClass()) {
4054       if (!IntfDecl->hasAttr<ObjCSubclassingRestrictedAttr>() &&
4055           Super->hasAttr<ObjCSubclassingRestrictedAttr>()) {
4056         Diag(IntfDecl->getLocation(), diag::err_restricted_superclass_mismatch);
4057         Diag(Super->getLocation(), diag::note_class_declared);
4058       }
4059     }
4060   }
4061   DiagnoseVariableSizedIvars(*this, OCD);
4062   if (isInterfaceDeclKind) {
4063     // Reject invalid vardecls.
4064     for (unsigned i = 0, e = allTUVars.size(); i != e; i++) {
4065       DeclGroupRef DG = allTUVars[i].get();
4066       for (DeclGroupRef::iterator I = DG.begin(), E = DG.end(); I != E; ++I)
4067         if (VarDecl *VDecl = dyn_cast<VarDecl>(*I)) {
4068           if (!VDecl->hasExternalStorage())
4069             Diag(VDecl->getLocation(), diag::err_objc_var_decl_inclass);
4070         }
4071     }
4072   }
4073   ActOnObjCContainerFinishDefinition();
4074 
4075   for (unsigned i = 0, e = allTUVars.size(); i != e; i++) {
4076     DeclGroupRef DG = allTUVars[i].get();
4077     for (DeclGroupRef::iterator I = DG.begin(), E = DG.end(); I != E; ++I)
4078       (*I)->setTopLevelDeclInObjCContainer();
4079     Consumer.HandleTopLevelDeclInObjCContainer(DG);
4080   }
4081 
4082   ActOnDocumentableDecl(ClassDecl);
4083   return ClassDecl;
4084 }
4085 
4086 /// CvtQTToAstBitMask - utility routine to produce an AST bitmask for
4087 /// objective-c's type qualifier from the parser version of the same info.
4088 static Decl::ObjCDeclQualifier
4089 CvtQTToAstBitMask(ObjCDeclSpec::ObjCDeclQualifier PQTVal) {
4090   return (Decl::ObjCDeclQualifier) (unsigned) PQTVal;
4091 }
4092 
4093 /// \brief Check whether the declared result type of the given Objective-C
4094 /// method declaration is compatible with the method's class.
4095 ///
4096 static Sema::ResultTypeCompatibilityKind
4097 CheckRelatedResultTypeCompatibility(Sema &S, ObjCMethodDecl *Method,
4098                                     ObjCInterfaceDecl *CurrentClass) {
4099   QualType ResultType = Method->getReturnType();
4100 
4101   // If an Objective-C method inherits its related result type, then its
4102   // declared result type must be compatible with its own class type. The
4103   // declared result type is compatible if:
4104   if (const ObjCObjectPointerType *ResultObjectType
4105                                 = ResultType->getAs<ObjCObjectPointerType>()) {
4106     //   - it is id or qualified id, or
4107     if (ResultObjectType->isObjCIdType() ||
4108         ResultObjectType->isObjCQualifiedIdType())
4109       return Sema::RTC_Compatible;
4110 
4111     if (CurrentClass) {
4112       if (ObjCInterfaceDecl *ResultClass
4113                                       = ResultObjectType->getInterfaceDecl()) {
4114         //   - it is the same as the method's class type, or
4115         if (declaresSameEntity(CurrentClass, ResultClass))
4116           return Sema::RTC_Compatible;
4117 
4118         //   - it is a superclass of the method's class type
4119         if (ResultClass->isSuperClassOf(CurrentClass))
4120           return Sema::RTC_Compatible;
4121       }
4122     } else {
4123       // Any Objective-C pointer type might be acceptable for a protocol
4124       // method; we just don't know.
4125       return Sema::RTC_Unknown;
4126     }
4127   }
4128 
4129   return Sema::RTC_Incompatible;
4130 }
4131 
4132 namespace {
4133 /// A helper class for searching for methods which a particular method
4134 /// overrides.
4135 class OverrideSearch {
4136 public:
4137   Sema &S;
4138   ObjCMethodDecl *Method;
4139   llvm::SmallSetVector<ObjCMethodDecl*, 4> Overridden;
4140   bool Recursive;
4141 
4142 public:
4143   OverrideSearch(Sema &S, ObjCMethodDecl *method) : S(S), Method(method) {
4144     Selector selector = method->getSelector();
4145 
4146     // Bypass this search if we've never seen an instance/class method
4147     // with this selector before.
4148     Sema::GlobalMethodPool::iterator it = S.MethodPool.find(selector);
4149     if (it == S.MethodPool.end()) {
4150       if (!S.getExternalSource()) return;
4151       S.ReadMethodPool(selector);
4152 
4153       it = S.MethodPool.find(selector);
4154       if (it == S.MethodPool.end())
4155         return;
4156     }
4157     ObjCMethodList &list =
4158       method->isInstanceMethod() ? it->second.first : it->second.second;
4159     if (!list.getMethod()) return;
4160 
4161     ObjCContainerDecl *container
4162       = cast<ObjCContainerDecl>(method->getDeclContext());
4163 
4164     // Prevent the search from reaching this container again.  This is
4165     // important with categories, which override methods from the
4166     // interface and each other.
4167     if (ObjCCategoryDecl *Category = dyn_cast<ObjCCategoryDecl>(container)) {
4168       searchFromContainer(container);
4169       if (ObjCInterfaceDecl *Interface = Category->getClassInterface())
4170         searchFromContainer(Interface);
4171     } else {
4172       searchFromContainer(container);
4173     }
4174   }
4175 
4176   typedef decltype(Overridden)::iterator iterator;
4177   iterator begin() const { return Overridden.begin(); }
4178   iterator end() const { return Overridden.end(); }
4179 
4180 private:
4181   void searchFromContainer(ObjCContainerDecl *container) {
4182     if (container->isInvalidDecl()) return;
4183 
4184     switch (container->getDeclKind()) {
4185 #define OBJCCONTAINER(type, base) \
4186     case Decl::type: \
4187       searchFrom(cast<type##Decl>(container)); \
4188       break;
4189 #define ABSTRACT_DECL(expansion)
4190 #define DECL(type, base) \
4191     case Decl::type:
4192 #include "clang/AST/DeclNodes.inc"
4193       llvm_unreachable("not an ObjC container!");
4194     }
4195   }
4196 
4197   void searchFrom(ObjCProtocolDecl *protocol) {
4198     if (!protocol->hasDefinition())
4199       return;
4200 
4201     // A method in a protocol declaration overrides declarations from
4202     // referenced ("parent") protocols.
4203     search(protocol->getReferencedProtocols());
4204   }
4205 
4206   void searchFrom(ObjCCategoryDecl *category) {
4207     // A method in a category declaration overrides declarations from
4208     // the main class and from protocols the category references.
4209     // The main class is handled in the constructor.
4210     search(category->getReferencedProtocols());
4211   }
4212 
4213   void searchFrom(ObjCCategoryImplDecl *impl) {
4214     // A method in a category definition that has a category
4215     // declaration overrides declarations from the category
4216     // declaration.
4217     if (ObjCCategoryDecl *category = impl->getCategoryDecl()) {
4218       search(category);
4219       if (ObjCInterfaceDecl *Interface = category->getClassInterface())
4220         search(Interface);
4221 
4222     // Otherwise it overrides declarations from the class.
4223     } else if (ObjCInterfaceDecl *Interface = impl->getClassInterface()) {
4224       search(Interface);
4225     }
4226   }
4227 
4228   void searchFrom(ObjCInterfaceDecl *iface) {
4229     // A method in a class declaration overrides declarations from
4230     if (!iface->hasDefinition())
4231       return;
4232 
4233     //   - categories,
4234     for (auto *Cat : iface->known_categories())
4235       search(Cat);
4236 
4237     //   - the super class, and
4238     if (ObjCInterfaceDecl *super = iface->getSuperClass())
4239       search(super);
4240 
4241     //   - any referenced protocols.
4242     search(iface->getReferencedProtocols());
4243   }
4244 
4245   void searchFrom(ObjCImplementationDecl *impl) {
4246     // A method in a class implementation overrides declarations from
4247     // the class interface.
4248     if (ObjCInterfaceDecl *Interface = impl->getClassInterface())
4249       search(Interface);
4250   }
4251 
4252   void search(const ObjCProtocolList &protocols) {
4253     for (ObjCProtocolList::iterator i = protocols.begin(), e = protocols.end();
4254          i != e; ++i)
4255       search(*i);
4256   }
4257 
4258   void search(ObjCContainerDecl *container) {
4259     // Check for a method in this container which matches this selector.
4260     ObjCMethodDecl *meth = container->getMethod(Method->getSelector(),
4261                                                 Method->isInstanceMethod(),
4262                                                 /*AllowHidden=*/true);
4263 
4264     // If we find one, record it and bail out.
4265     if (meth) {
4266       Overridden.insert(meth);
4267       return;
4268     }
4269 
4270     // Otherwise, search for methods that a hypothetical method here
4271     // would have overridden.
4272 
4273     // Note that we're now in a recursive case.
4274     Recursive = true;
4275 
4276     searchFromContainer(container);
4277   }
4278 };
4279 } // end anonymous namespace
4280 
4281 void Sema::CheckObjCMethodOverrides(ObjCMethodDecl *ObjCMethod,
4282                                     ObjCInterfaceDecl *CurrentClass,
4283                                     ResultTypeCompatibilityKind RTC) {
4284   // Search for overridden methods and merge information down from them.
4285   OverrideSearch overrides(*this, ObjCMethod);
4286   // Keep track if the method overrides any method in the class's base classes,
4287   // its protocols, or its categories' protocols; we will keep that info
4288   // in the ObjCMethodDecl.
4289   // For this info, a method in an implementation is not considered as
4290   // overriding the same method in the interface or its categories.
4291   bool hasOverriddenMethodsInBaseOrProtocol = false;
4292   for (OverrideSearch::iterator
4293          i = overrides.begin(), e = overrides.end(); i != e; ++i) {
4294     ObjCMethodDecl *overridden = *i;
4295 
4296     if (!hasOverriddenMethodsInBaseOrProtocol) {
4297       if (isa<ObjCProtocolDecl>(overridden->getDeclContext()) ||
4298           CurrentClass != overridden->getClassInterface() ||
4299           overridden->isOverriding()) {
4300         hasOverriddenMethodsInBaseOrProtocol = true;
4301 
4302       } else if (isa<ObjCImplDecl>(ObjCMethod->getDeclContext())) {
4303         // OverrideSearch will return as "overridden" the same method in the
4304         // interface. For hasOverriddenMethodsInBaseOrProtocol, we need to
4305         // check whether a category of a base class introduced a method with the
4306         // same selector, after the interface method declaration.
4307         // To avoid unnecessary lookups in the majority of cases, we use the
4308         // extra info bits in GlobalMethodPool to check whether there were any
4309         // category methods with this selector.
4310         GlobalMethodPool::iterator It =
4311             MethodPool.find(ObjCMethod->getSelector());
4312         if (It != MethodPool.end()) {
4313           ObjCMethodList &List =
4314             ObjCMethod->isInstanceMethod()? It->second.first: It->second.second;
4315           unsigned CategCount = List.getBits();
4316           if (CategCount > 0) {
4317             // If the method is in a category we'll do lookup if there were at
4318             // least 2 category methods recorded, otherwise only one will do.
4319             if (CategCount > 1 ||
4320                 !isa<ObjCCategoryImplDecl>(overridden->getDeclContext())) {
4321               OverrideSearch overrides(*this, overridden);
4322               for (OverrideSearch::iterator
4323                      OI= overrides.begin(), OE= overrides.end(); OI!=OE; ++OI) {
4324                 ObjCMethodDecl *SuperOverridden = *OI;
4325                 if (isa<ObjCProtocolDecl>(SuperOverridden->getDeclContext()) ||
4326                     CurrentClass != SuperOverridden->getClassInterface()) {
4327                   hasOverriddenMethodsInBaseOrProtocol = true;
4328                   overridden->setOverriding(true);
4329                   break;
4330                 }
4331               }
4332             }
4333           }
4334         }
4335       }
4336     }
4337 
4338     // Propagate down the 'related result type' bit from overridden methods.
4339     if (RTC != Sema::RTC_Incompatible && overridden->hasRelatedResultType())
4340       ObjCMethod->SetRelatedResultType();
4341 
4342     // Then merge the declarations.
4343     mergeObjCMethodDecls(ObjCMethod, overridden);
4344 
4345     if (ObjCMethod->isImplicit() && overridden->isImplicit())
4346       continue; // Conflicting properties are detected elsewhere.
4347 
4348     // Check for overriding methods
4349     if (isa<ObjCInterfaceDecl>(ObjCMethod->getDeclContext()) ||
4350         isa<ObjCImplementationDecl>(ObjCMethod->getDeclContext()))
4351       CheckConflictingOverridingMethod(ObjCMethod, overridden,
4352               isa<ObjCProtocolDecl>(overridden->getDeclContext()));
4353 
4354     if (CurrentClass && overridden->getDeclContext() != CurrentClass &&
4355         isa<ObjCInterfaceDecl>(overridden->getDeclContext()) &&
4356         !overridden->isImplicit() /* not meant for properties */) {
4357       ObjCMethodDecl::param_iterator ParamI = ObjCMethod->param_begin(),
4358                                           E = ObjCMethod->param_end();
4359       ObjCMethodDecl::param_iterator PrevI = overridden->param_begin(),
4360                                      PrevE = overridden->param_end();
4361       for (; ParamI != E && PrevI != PrevE; ++ParamI, ++PrevI) {
4362         assert(PrevI != overridden->param_end() && "Param mismatch");
4363         QualType T1 = Context.getCanonicalType((*ParamI)->getType());
4364         QualType T2 = Context.getCanonicalType((*PrevI)->getType());
4365         // If type of argument of method in this class does not match its
4366         // respective argument type in the super class method, issue warning;
4367         if (!Context.typesAreCompatible(T1, T2)) {
4368           Diag((*ParamI)->getLocation(), diag::ext_typecheck_base_super)
4369             << T1 << T2;
4370           Diag(overridden->getLocation(), diag::note_previous_declaration);
4371           break;
4372         }
4373       }
4374     }
4375   }
4376 
4377   ObjCMethod->setOverriding(hasOverriddenMethodsInBaseOrProtocol);
4378 }
4379 
4380 /// Merge type nullability from for a redeclaration of the same entity,
4381 /// producing the updated type of the redeclared entity.
4382 static QualType mergeTypeNullabilityForRedecl(Sema &S, SourceLocation loc,
4383                                               QualType type,
4384                                               bool usesCSKeyword,
4385                                               SourceLocation prevLoc,
4386                                               QualType prevType,
4387                                               bool prevUsesCSKeyword) {
4388   // Determine the nullability of both types.
4389   auto nullability = type->getNullability(S.Context);
4390   auto prevNullability = prevType->getNullability(S.Context);
4391 
4392   // Easy case: both have nullability.
4393   if (nullability.hasValue() == prevNullability.hasValue()) {
4394     // Neither has nullability; continue.
4395     if (!nullability)
4396       return type;
4397 
4398     // The nullabilities are equivalent; do nothing.
4399     if (*nullability == *prevNullability)
4400       return type;
4401 
4402     // Complain about mismatched nullability.
4403     S.Diag(loc, diag::err_nullability_conflicting)
4404       << DiagNullabilityKind(*nullability, usesCSKeyword)
4405       << DiagNullabilityKind(*prevNullability, prevUsesCSKeyword);
4406     return type;
4407   }
4408 
4409   // If it's the redeclaration that has nullability, don't change anything.
4410   if (nullability)
4411     return type;
4412 
4413   // Otherwise, provide the result with the same nullability.
4414   return S.Context.getAttributedType(
4415            AttributedType::getNullabilityAttrKind(*prevNullability),
4416            type, type);
4417 }
4418 
4419 /// Merge information from the declaration of a method in the \@interface
4420 /// (or a category/extension) into the corresponding method in the
4421 /// @implementation (for a class or category).
4422 static void mergeInterfaceMethodToImpl(Sema &S,
4423                                        ObjCMethodDecl *method,
4424                                        ObjCMethodDecl *prevMethod) {
4425   // Merge the objc_requires_super attribute.
4426   if (prevMethod->hasAttr<ObjCRequiresSuperAttr>() &&
4427       !method->hasAttr<ObjCRequiresSuperAttr>()) {
4428     // merge the attribute into implementation.
4429     method->addAttr(
4430       ObjCRequiresSuperAttr::CreateImplicit(S.Context,
4431                                             method->getLocation()));
4432   }
4433 
4434   // Merge nullability of the result type.
4435   QualType newReturnType
4436     = mergeTypeNullabilityForRedecl(
4437         S, method->getReturnTypeSourceRange().getBegin(),
4438         method->getReturnType(),
4439         method->getObjCDeclQualifier() & Decl::OBJC_TQ_CSNullability,
4440         prevMethod->getReturnTypeSourceRange().getBegin(),
4441         prevMethod->getReturnType(),
4442         prevMethod->getObjCDeclQualifier() & Decl::OBJC_TQ_CSNullability);
4443   method->setReturnType(newReturnType);
4444 
4445   // Handle each of the parameters.
4446   unsigned numParams = method->param_size();
4447   unsigned numPrevParams = prevMethod->param_size();
4448   for (unsigned i = 0, n = std::min(numParams, numPrevParams); i != n; ++i) {
4449     ParmVarDecl *param = method->param_begin()[i];
4450     ParmVarDecl *prevParam = prevMethod->param_begin()[i];
4451 
4452     // Merge nullability.
4453     QualType newParamType
4454       = mergeTypeNullabilityForRedecl(
4455           S, param->getLocation(), param->getType(),
4456           param->getObjCDeclQualifier() & Decl::OBJC_TQ_CSNullability,
4457           prevParam->getLocation(), prevParam->getType(),
4458           prevParam->getObjCDeclQualifier() & Decl::OBJC_TQ_CSNullability);
4459     param->setType(newParamType);
4460   }
4461 }
4462 
4463 /// Verify that the method parameters/return value have types that are supported
4464 /// by the x86 target.
4465 static void checkObjCMethodX86VectorTypes(Sema &SemaRef,
4466                                           const ObjCMethodDecl *Method) {
4467   assert(SemaRef.getASTContext().getTargetInfo().getTriple().getArch() ==
4468              llvm::Triple::x86 &&
4469          "x86-specific check invoked for a different target");
4470   SourceLocation Loc;
4471   QualType T;
4472   for (const ParmVarDecl *P : Method->parameters()) {
4473     if (P->getType()->isVectorType()) {
4474       Loc = P->getLocStart();
4475       T = P->getType();
4476       break;
4477     }
4478   }
4479   if (Loc.isInvalid()) {
4480     if (Method->getReturnType()->isVectorType()) {
4481       Loc = Method->getReturnTypeSourceRange().getBegin();
4482       T = Method->getReturnType();
4483     } else
4484       return;
4485   }
4486 
4487   // Vector parameters/return values are not supported by objc_msgSend on x86 in
4488   // iOS < 9 and macOS < 10.11.
4489   const auto &Triple = SemaRef.getASTContext().getTargetInfo().getTriple();
4490   VersionTuple AcceptedInVersion;
4491   if (Triple.getOS() == llvm::Triple::IOS)
4492     AcceptedInVersion = VersionTuple(/*Major=*/9);
4493   else if (Triple.isMacOSX())
4494     AcceptedInVersion = VersionTuple(/*Major=*/10, /*Minor=*/11);
4495   else
4496     return;
4497   if (SemaRef.getASTContext().getTargetInfo().getPlatformMinVersion() >=
4498       AcceptedInVersion)
4499     return;
4500   SemaRef.Diag(Loc, diag::err_objc_method_unsupported_param_ret_type)
4501       << T << (Method->getReturnType()->isVectorType() ? /*return value*/ 1
4502                                                        : /*parameter*/ 0)
4503       << (Triple.isMacOSX() ? "macOS 10.11" : "iOS 9");
4504 }
4505 
4506 Decl *Sema::ActOnMethodDeclaration(
4507     Scope *S,
4508     SourceLocation MethodLoc, SourceLocation EndLoc,
4509     tok::TokenKind MethodType,
4510     ObjCDeclSpec &ReturnQT, ParsedType ReturnType,
4511     ArrayRef<SourceLocation> SelectorLocs,
4512     Selector Sel,
4513     // optional arguments. The number of types/arguments is obtained
4514     // from the Sel.getNumArgs().
4515     ObjCArgInfo *ArgInfo,
4516     DeclaratorChunk::ParamInfo *CParamInfo, unsigned CNumArgs, // c-style args
4517     AttributeList *AttrList, tok::ObjCKeywordKind MethodDeclKind,
4518     bool isVariadic, bool MethodDefinition) {
4519   // Make sure we can establish a context for the method.
4520   if (!CurContext->isObjCContainer()) {
4521     Diag(MethodLoc, diag::err_missing_method_context);
4522     return nullptr;
4523   }
4524   Decl *ClassDecl = cast<ObjCContainerDecl>(CurContext);
4525   QualType resultDeclType;
4526 
4527   bool HasRelatedResultType = false;
4528   TypeSourceInfo *ReturnTInfo = nullptr;
4529   if (ReturnType) {
4530     resultDeclType = GetTypeFromParser(ReturnType, &ReturnTInfo);
4531 
4532     if (CheckFunctionReturnType(resultDeclType, MethodLoc))
4533       return nullptr;
4534 
4535     QualType bareResultType = resultDeclType;
4536     (void)AttributedType::stripOuterNullability(bareResultType);
4537     HasRelatedResultType = (bareResultType == Context.getObjCInstanceType());
4538   } else { // get the type for "id".
4539     resultDeclType = Context.getObjCIdType();
4540     Diag(MethodLoc, diag::warn_missing_method_return_type)
4541       << FixItHint::CreateInsertion(SelectorLocs.front(), "(id)");
4542   }
4543 
4544   ObjCMethodDecl *ObjCMethod = ObjCMethodDecl::Create(
4545       Context, MethodLoc, EndLoc, Sel, resultDeclType, ReturnTInfo, CurContext,
4546       MethodType == tok::minus, isVariadic,
4547       /*isPropertyAccessor=*/false,
4548       /*isImplicitlyDeclared=*/false, /*isDefined=*/false,
4549       MethodDeclKind == tok::objc_optional ? ObjCMethodDecl::Optional
4550                                            : ObjCMethodDecl::Required,
4551       HasRelatedResultType);
4552 
4553   SmallVector<ParmVarDecl*, 16> Params;
4554 
4555   for (unsigned i = 0, e = Sel.getNumArgs(); i != e; ++i) {
4556     QualType ArgType;
4557     TypeSourceInfo *DI;
4558 
4559     if (!ArgInfo[i].Type) {
4560       ArgType = Context.getObjCIdType();
4561       DI = nullptr;
4562     } else {
4563       ArgType = GetTypeFromParser(ArgInfo[i].Type, &DI);
4564     }
4565 
4566     LookupResult R(*this, ArgInfo[i].Name, ArgInfo[i].NameLoc,
4567                    LookupOrdinaryName, forRedeclarationInCurContext());
4568     LookupName(R, S);
4569     if (R.isSingleResult()) {
4570       NamedDecl *PrevDecl = R.getFoundDecl();
4571       if (S->isDeclScope(PrevDecl)) {
4572         Diag(ArgInfo[i].NameLoc,
4573              (MethodDefinition ? diag::warn_method_param_redefinition
4574                                : diag::warn_method_param_declaration))
4575           << ArgInfo[i].Name;
4576         Diag(PrevDecl->getLocation(),
4577              diag::note_previous_declaration);
4578       }
4579     }
4580 
4581     SourceLocation StartLoc = DI
4582       ? DI->getTypeLoc().getBeginLoc()
4583       : ArgInfo[i].NameLoc;
4584 
4585     ParmVarDecl* Param = CheckParameter(ObjCMethod, StartLoc,
4586                                         ArgInfo[i].NameLoc, ArgInfo[i].Name,
4587                                         ArgType, DI, SC_None);
4588 
4589     Param->setObjCMethodScopeInfo(i);
4590 
4591     Param->setObjCDeclQualifier(
4592       CvtQTToAstBitMask(ArgInfo[i].DeclSpec.getObjCDeclQualifier()));
4593 
4594     // Apply the attributes to the parameter.
4595     ProcessDeclAttributeList(TUScope, Param, ArgInfo[i].ArgAttrs);
4596     AddPragmaAttributes(TUScope, Param);
4597 
4598     if (Param->hasAttr<BlocksAttr>()) {
4599       Diag(Param->getLocation(), diag::err_block_on_nonlocal);
4600       Param->setInvalidDecl();
4601     }
4602     S->AddDecl(Param);
4603     IdResolver.AddDecl(Param);
4604 
4605     Params.push_back(Param);
4606   }
4607 
4608   for (unsigned i = 0, e = CNumArgs; i != e; ++i) {
4609     ParmVarDecl *Param = cast<ParmVarDecl>(CParamInfo[i].Param);
4610     QualType ArgType = Param->getType();
4611     if (ArgType.isNull())
4612       ArgType = Context.getObjCIdType();
4613     else
4614       // Perform the default array/function conversions (C99 6.7.5.3p[7,8]).
4615       ArgType = Context.getAdjustedParameterType(ArgType);
4616 
4617     Param->setDeclContext(ObjCMethod);
4618     Params.push_back(Param);
4619   }
4620 
4621   ObjCMethod->setMethodParams(Context, Params, SelectorLocs);
4622   ObjCMethod->setObjCDeclQualifier(
4623     CvtQTToAstBitMask(ReturnQT.getObjCDeclQualifier()));
4624 
4625   if (AttrList)
4626     ProcessDeclAttributeList(TUScope, ObjCMethod, AttrList);
4627   AddPragmaAttributes(TUScope, ObjCMethod);
4628 
4629   // Add the method now.
4630   const ObjCMethodDecl *PrevMethod = nullptr;
4631   if (ObjCImplDecl *ImpDecl = dyn_cast<ObjCImplDecl>(ClassDecl)) {
4632     if (MethodType == tok::minus) {
4633       PrevMethod = ImpDecl->getInstanceMethod(Sel);
4634       ImpDecl->addInstanceMethod(ObjCMethod);
4635     } else {
4636       PrevMethod = ImpDecl->getClassMethod(Sel);
4637       ImpDecl->addClassMethod(ObjCMethod);
4638     }
4639 
4640     // Merge information from the @interface declaration into the
4641     // @implementation.
4642     if (ObjCInterfaceDecl *IDecl = ImpDecl->getClassInterface()) {
4643       if (auto *IMD = IDecl->lookupMethod(ObjCMethod->getSelector(),
4644                                           ObjCMethod->isInstanceMethod())) {
4645         mergeInterfaceMethodToImpl(*this, ObjCMethod, IMD);
4646 
4647         // Warn about defining -dealloc in a category.
4648         if (isa<ObjCCategoryImplDecl>(ImpDecl) && IMD->isOverriding() &&
4649             ObjCMethod->getSelector().getMethodFamily() == OMF_dealloc) {
4650           Diag(ObjCMethod->getLocation(), diag::warn_dealloc_in_category)
4651             << ObjCMethod->getDeclName();
4652         }
4653       }
4654     }
4655   } else {
4656     cast<DeclContext>(ClassDecl)->addDecl(ObjCMethod);
4657   }
4658 
4659   if (PrevMethod) {
4660     // You can never have two method definitions with the same name.
4661     Diag(ObjCMethod->getLocation(), diag::err_duplicate_method_decl)
4662       << ObjCMethod->getDeclName();
4663     Diag(PrevMethod->getLocation(), diag::note_previous_declaration);
4664     ObjCMethod->setInvalidDecl();
4665     return ObjCMethod;
4666   }
4667 
4668   // If this Objective-C method does not have a related result type, but we
4669   // are allowed to infer related result types, try to do so based on the
4670   // method family.
4671   ObjCInterfaceDecl *CurrentClass = dyn_cast<ObjCInterfaceDecl>(ClassDecl);
4672   if (!CurrentClass) {
4673     if (ObjCCategoryDecl *Cat = dyn_cast<ObjCCategoryDecl>(ClassDecl))
4674       CurrentClass = Cat->getClassInterface();
4675     else if (ObjCImplDecl *Impl = dyn_cast<ObjCImplDecl>(ClassDecl))
4676       CurrentClass = Impl->getClassInterface();
4677     else if (ObjCCategoryImplDecl *CatImpl
4678                                    = dyn_cast<ObjCCategoryImplDecl>(ClassDecl))
4679       CurrentClass = CatImpl->getClassInterface();
4680   }
4681 
4682   ResultTypeCompatibilityKind RTC
4683     = CheckRelatedResultTypeCompatibility(*this, ObjCMethod, CurrentClass);
4684 
4685   CheckObjCMethodOverrides(ObjCMethod, CurrentClass, RTC);
4686 
4687   bool ARCError = false;
4688   if (getLangOpts().ObjCAutoRefCount)
4689     ARCError = CheckARCMethodDecl(ObjCMethod);
4690 
4691   // Infer the related result type when possible.
4692   if (!ARCError && RTC == Sema::RTC_Compatible &&
4693       !ObjCMethod->hasRelatedResultType() &&
4694       LangOpts.ObjCInferRelatedResultType) {
4695     bool InferRelatedResultType = false;
4696     switch (ObjCMethod->getMethodFamily()) {
4697     case OMF_None:
4698     case OMF_copy:
4699     case OMF_dealloc:
4700     case OMF_finalize:
4701     case OMF_mutableCopy:
4702     case OMF_release:
4703     case OMF_retainCount:
4704     case OMF_initialize:
4705     case OMF_performSelector:
4706       break;
4707 
4708     case OMF_alloc:
4709     case OMF_new:
4710         InferRelatedResultType = ObjCMethod->isClassMethod();
4711       break;
4712 
4713     case OMF_init:
4714     case OMF_autorelease:
4715     case OMF_retain:
4716     case OMF_self:
4717       InferRelatedResultType = ObjCMethod->isInstanceMethod();
4718       break;
4719     }
4720 
4721     if (InferRelatedResultType &&
4722         !ObjCMethod->getReturnType()->isObjCIndependentClassType())
4723       ObjCMethod->SetRelatedResultType();
4724   }
4725 
4726   if (MethodDefinition &&
4727       Context.getTargetInfo().getTriple().getArch() == llvm::Triple::x86)
4728     checkObjCMethodX86VectorTypes(*this, ObjCMethod);
4729 
4730   ActOnDocumentableDecl(ObjCMethod);
4731 
4732   return ObjCMethod;
4733 }
4734 
4735 bool Sema::CheckObjCDeclScope(Decl *D) {
4736   // Following is also an error. But it is caused by a missing @end
4737   // and diagnostic is issued elsewhere.
4738   if (isa<ObjCContainerDecl>(CurContext->getRedeclContext()))
4739     return false;
4740 
4741   // If we switched context to translation unit while we are still lexically in
4742   // an objc container, it means the parser missed emitting an error.
4743   if (isa<TranslationUnitDecl>(getCurLexicalContext()->getRedeclContext()))
4744     return false;
4745 
4746   Diag(D->getLocation(), diag::err_objc_decls_may_only_appear_in_global_scope);
4747   D->setInvalidDecl();
4748 
4749   return true;
4750 }
4751 
4752 /// Called whenever \@defs(ClassName) is encountered in the source.  Inserts the
4753 /// instance variables of ClassName into Decls.
4754 void Sema::ActOnDefs(Scope *S, Decl *TagD, SourceLocation DeclStart,
4755                      IdentifierInfo *ClassName,
4756                      SmallVectorImpl<Decl*> &Decls) {
4757   // Check that ClassName is a valid class
4758   ObjCInterfaceDecl *Class = getObjCInterfaceDecl(ClassName, DeclStart);
4759   if (!Class) {
4760     Diag(DeclStart, diag::err_undef_interface) << ClassName;
4761     return;
4762   }
4763   if (LangOpts.ObjCRuntime.isNonFragile()) {
4764     Diag(DeclStart, diag::err_atdef_nonfragile_interface);
4765     return;
4766   }
4767 
4768   // Collect the instance variables
4769   SmallVector<const ObjCIvarDecl*, 32> Ivars;
4770   Context.DeepCollectObjCIvars(Class, true, Ivars);
4771   // For each ivar, create a fresh ObjCAtDefsFieldDecl.
4772   for (unsigned i = 0; i < Ivars.size(); i++) {
4773     const FieldDecl* ID = Ivars[i];
4774     RecordDecl *Record = dyn_cast<RecordDecl>(TagD);
4775     Decl *FD = ObjCAtDefsFieldDecl::Create(Context, Record,
4776                                            /*FIXME: StartL=*/ID->getLocation(),
4777                                            ID->getLocation(),
4778                                            ID->getIdentifier(), ID->getType(),
4779                                            ID->getBitWidth());
4780     Decls.push_back(FD);
4781   }
4782 
4783   // Introduce all of these fields into the appropriate scope.
4784   for (SmallVectorImpl<Decl*>::iterator D = Decls.begin();
4785        D != Decls.end(); ++D) {
4786     FieldDecl *FD = cast<FieldDecl>(*D);
4787     if (getLangOpts().CPlusPlus)
4788       PushOnScopeChains(FD, S);
4789     else if (RecordDecl *Record = dyn_cast<RecordDecl>(TagD))
4790       Record->addDecl(FD);
4791   }
4792 }
4793 
4794 /// \brief Build a type-check a new Objective-C exception variable declaration.
4795 VarDecl *Sema::BuildObjCExceptionDecl(TypeSourceInfo *TInfo, QualType T,
4796                                       SourceLocation StartLoc,
4797                                       SourceLocation IdLoc,
4798                                       IdentifierInfo *Id,
4799                                       bool Invalid) {
4800   // ISO/IEC TR 18037 S6.7.3: "The type of an object with automatic storage
4801   // duration shall not be qualified by an address-space qualifier."
4802   // Since all parameters have automatic store duration, they can not have
4803   // an address space.
4804   if (T.getAddressSpace() != LangAS::Default) {
4805     Diag(IdLoc, diag::err_arg_with_address_space);
4806     Invalid = true;
4807   }
4808 
4809   // An @catch parameter must be an unqualified object pointer type;
4810   // FIXME: Recover from "NSObject foo" by inserting the * in "NSObject *foo"?
4811   if (Invalid) {
4812     // Don't do any further checking.
4813   } else if (T->isDependentType()) {
4814     // Okay: we don't know what this type will instantiate to.
4815   } else if (!T->isObjCObjectPointerType()) {
4816     Invalid = true;
4817     Diag(IdLoc ,diag::err_catch_param_not_objc_type);
4818   } else if (T->isObjCQualifiedIdType()) {
4819     Invalid = true;
4820     Diag(IdLoc, diag::err_illegal_qualifiers_on_catch_parm);
4821   }
4822 
4823   VarDecl *New = VarDecl::Create(Context, CurContext, StartLoc, IdLoc, Id,
4824                                  T, TInfo, SC_None);
4825   New->setExceptionVariable(true);
4826 
4827   // In ARC, infer 'retaining' for variables of retainable type.
4828   if (getLangOpts().ObjCAutoRefCount && inferObjCARCLifetime(New))
4829     Invalid = true;
4830 
4831   if (Invalid)
4832     New->setInvalidDecl();
4833   return New;
4834 }
4835 
4836 Decl *Sema::ActOnObjCExceptionDecl(Scope *S, Declarator &D) {
4837   const DeclSpec &DS = D.getDeclSpec();
4838 
4839   // We allow the "register" storage class on exception variables because
4840   // GCC did, but we drop it completely. Any other storage class is an error.
4841   if (DS.getStorageClassSpec() == DeclSpec::SCS_register) {
4842     Diag(DS.getStorageClassSpecLoc(), diag::warn_register_objc_catch_parm)
4843       << FixItHint::CreateRemoval(SourceRange(DS.getStorageClassSpecLoc()));
4844   } else if (DeclSpec::SCS SCS = DS.getStorageClassSpec()) {
4845     Diag(DS.getStorageClassSpecLoc(), diag::err_storage_spec_on_catch_parm)
4846       << DeclSpec::getSpecifierName(SCS);
4847   }
4848   if (DS.isInlineSpecified())
4849     Diag(DS.getInlineSpecLoc(), diag::err_inline_non_function)
4850         << getLangOpts().CPlusPlus17;
4851   if (DeclSpec::TSCS TSCS = D.getDeclSpec().getThreadStorageClassSpec())
4852     Diag(D.getDeclSpec().getThreadStorageClassSpecLoc(),
4853          diag::err_invalid_thread)
4854      << DeclSpec::getSpecifierName(TSCS);
4855   D.getMutableDeclSpec().ClearStorageClassSpecs();
4856 
4857   DiagnoseFunctionSpecifiers(D.getDeclSpec());
4858 
4859   // Check that there are no default arguments inside the type of this
4860   // exception object (C++ only).
4861   if (getLangOpts().CPlusPlus)
4862     CheckExtraCXXDefaultArguments(D);
4863 
4864   TypeSourceInfo *TInfo = GetTypeForDeclarator(D, S);
4865   QualType ExceptionType = TInfo->getType();
4866 
4867   VarDecl *New = BuildObjCExceptionDecl(TInfo, ExceptionType,
4868                                         D.getSourceRange().getBegin(),
4869                                         D.getIdentifierLoc(),
4870                                         D.getIdentifier(),
4871                                         D.isInvalidType());
4872 
4873   // Parameter declarators cannot be qualified (C++ [dcl.meaning]p1).
4874   if (D.getCXXScopeSpec().isSet()) {
4875     Diag(D.getIdentifierLoc(), diag::err_qualified_objc_catch_parm)
4876       << D.getCXXScopeSpec().getRange();
4877     New->setInvalidDecl();
4878   }
4879 
4880   // Add the parameter declaration into this scope.
4881   S->AddDecl(New);
4882   if (D.getIdentifier())
4883     IdResolver.AddDecl(New);
4884 
4885   ProcessDeclAttributes(S, New, D);
4886 
4887   if (New->hasAttr<BlocksAttr>())
4888     Diag(New->getLocation(), diag::err_block_on_nonlocal);
4889   return New;
4890 }
4891 
4892 /// CollectIvarsToConstructOrDestruct - Collect those ivars which require
4893 /// initialization.
4894 void Sema::CollectIvarsToConstructOrDestruct(ObjCInterfaceDecl *OI,
4895                                 SmallVectorImpl<ObjCIvarDecl*> &Ivars) {
4896   for (ObjCIvarDecl *Iv = OI->all_declared_ivar_begin(); Iv;
4897        Iv= Iv->getNextIvar()) {
4898     QualType QT = Context.getBaseElementType(Iv->getType());
4899     if (QT->isRecordType())
4900       Ivars.push_back(Iv);
4901   }
4902 }
4903 
4904 void Sema::DiagnoseUseOfUnimplementedSelectors() {
4905   // Load referenced selectors from the external source.
4906   if (ExternalSource) {
4907     SmallVector<std::pair<Selector, SourceLocation>, 4> Sels;
4908     ExternalSource->ReadReferencedSelectors(Sels);
4909     for (unsigned I = 0, N = Sels.size(); I != N; ++I)
4910       ReferencedSelectors[Sels[I].first] = Sels[I].second;
4911   }
4912 
4913   // Warning will be issued only when selector table is
4914   // generated (which means there is at lease one implementation
4915   // in the TU). This is to match gcc's behavior.
4916   if (ReferencedSelectors.empty() ||
4917       !Context.AnyObjCImplementation())
4918     return;
4919   for (auto &SelectorAndLocation : ReferencedSelectors) {
4920     Selector Sel = SelectorAndLocation.first;
4921     SourceLocation Loc = SelectorAndLocation.second;
4922     if (!LookupImplementedMethodInGlobalPool(Sel))
4923       Diag(Loc, diag::warn_unimplemented_selector) << Sel;
4924   }
4925 }
4926 
4927 ObjCIvarDecl *
4928 Sema::GetIvarBackingPropertyAccessor(const ObjCMethodDecl *Method,
4929                                      const ObjCPropertyDecl *&PDecl) const {
4930   if (Method->isClassMethod())
4931     return nullptr;
4932   const ObjCInterfaceDecl *IDecl = Method->getClassInterface();
4933   if (!IDecl)
4934     return nullptr;
4935   Method = IDecl->lookupMethod(Method->getSelector(), /*isInstance=*/true,
4936                                /*shallowCategoryLookup=*/false,
4937                                /*followSuper=*/false);
4938   if (!Method || !Method->isPropertyAccessor())
4939     return nullptr;
4940   if ((PDecl = Method->findPropertyDecl()))
4941     if (ObjCIvarDecl *IV = PDecl->getPropertyIvarDecl()) {
4942       // property backing ivar must belong to property's class
4943       // or be a private ivar in class's implementation.
4944       // FIXME. fix the const-ness issue.
4945       IV = const_cast<ObjCInterfaceDecl *>(IDecl)->lookupInstanceVariable(
4946                                                         IV->getIdentifier());
4947       return IV;
4948     }
4949   return nullptr;
4950 }
4951 
4952 namespace {
4953   /// Used by Sema::DiagnoseUnusedBackingIvarInAccessor to check if a property
4954   /// accessor references the backing ivar.
4955   class UnusedBackingIvarChecker :
4956       public RecursiveASTVisitor<UnusedBackingIvarChecker> {
4957   public:
4958     Sema &S;
4959     const ObjCMethodDecl *Method;
4960     const ObjCIvarDecl *IvarD;
4961     bool AccessedIvar;
4962     bool InvokedSelfMethod;
4963 
4964     UnusedBackingIvarChecker(Sema &S, const ObjCMethodDecl *Method,
4965                              const ObjCIvarDecl *IvarD)
4966       : S(S), Method(Method), IvarD(IvarD),
4967         AccessedIvar(false), InvokedSelfMethod(false) {
4968       assert(IvarD);
4969     }
4970 
4971     bool VisitObjCIvarRefExpr(ObjCIvarRefExpr *E) {
4972       if (E->getDecl() == IvarD) {
4973         AccessedIvar = true;
4974         return false;
4975       }
4976       return true;
4977     }
4978 
4979     bool VisitObjCMessageExpr(ObjCMessageExpr *E) {
4980       if (E->getReceiverKind() == ObjCMessageExpr::Instance &&
4981           S.isSelfExpr(E->getInstanceReceiver(), Method)) {
4982         InvokedSelfMethod = true;
4983       }
4984       return true;
4985     }
4986   };
4987 } // end anonymous namespace
4988 
4989 void Sema::DiagnoseUnusedBackingIvarInAccessor(Scope *S,
4990                                           const ObjCImplementationDecl *ImplD) {
4991   if (S->hasUnrecoverableErrorOccurred())
4992     return;
4993 
4994   for (const auto *CurMethod : ImplD->instance_methods()) {
4995     unsigned DIAG = diag::warn_unused_property_backing_ivar;
4996     SourceLocation Loc = CurMethod->getLocation();
4997     if (Diags.isIgnored(DIAG, Loc))
4998       continue;
4999 
5000     const ObjCPropertyDecl *PDecl;
5001     const ObjCIvarDecl *IV = GetIvarBackingPropertyAccessor(CurMethod, PDecl);
5002     if (!IV)
5003       continue;
5004 
5005     UnusedBackingIvarChecker Checker(*this, CurMethod, IV);
5006     Checker.TraverseStmt(CurMethod->getBody());
5007     if (Checker.AccessedIvar)
5008       continue;
5009 
5010     // Do not issue this warning if backing ivar is used somewhere and accessor
5011     // implementation makes a self call. This is to prevent false positive in
5012     // cases where the ivar is accessed by another method that the accessor
5013     // delegates to.
5014     if (!IV->isReferenced() || !Checker.InvokedSelfMethod) {
5015       Diag(Loc, DIAG) << IV;
5016       Diag(PDecl->getLocation(), diag::note_property_declare);
5017     }
5018   }
5019 }
5020