[Sema][ObjC] Infer availability of +new from availability of -init

[erik.pilkington]

Summary

rdar://18335828

Thanks!
Erik

[arphaman]

Hmm, I don't think this solution is ideal, we'd rather have an attribute somewhere for other consumers of availability annotations. Does MyObject have an implicit decl of new, or are we referring to NSObjects new? Ideally we would an attribute on a particular new instead, but that might not work.

[erik.pilkington]

In D51189#1211754, @arphaman wrote:

Hmm, I don't think this solution is ideal, we'd rather have an attribute somewhere for other consumers of availability annotations. Does MyObject have an implicit decl of new, or are we referring to NSObjects new? Ideally we would an attribute on a particular new instead, but that might not work.

We're referring to NSObject's new. I don't think it's unreasonable to ask users who override init to be unavailable also override new with the same annotation, but it seems like extra boilerplate for something that we can easily infer in clang. What other consumers are you concerned about?

[arphaman]

In D51189#1211763, @erik.pilkington wrote:

In D51189#1211754, @arphaman wrote:

Hmm, I don't think this solution is ideal, we'd rather have an attribute somewhere for other consumers of availability annotations. Does MyObject have an implicit decl of new, or are we referring to NSObjects new? Ideally we would an attribute on a particular new instead, but that might not work.

We're referring to NSObject's new. I don't think it's unreasonable to ask users who override init to be unavailable also override new with the same annotation, but it seems like extra boilerplate for something that we can easily infer in clang. What other consumers are you concerned about?

+ @ributzka
One consumer is TAPI. It looks at the declarations present in the header file, so it won't be able to reason about the availability of new with the current implementation. We could potentially implicitly declare unavailable new in the interface if init is unavailable, but that wouldn't really too work with class categories (since new might be explicitly declared there). Maybe it's worth it though.

[ributzka]

TAPI mostly cares about linkable symbols, so this shouldn't be a problem.

[steven_wu]

I feel like this is a much tricky situation than just new and init. Following example is the same situation.

__attribute__((objc_root_class))
@interface NSObject
- (void) foo;
- (void) bar;
@end

@implementation NSObject
- (void) foo {}
- (void) bar { [self foo]; }
@end

@interface MyObject : NSObject
- (void) foo __attribute__((unavailable));
@end

void test(MyObject *obj) {
  [obj bar];
}

We can do something about [NSObject new] because we know it's implementation but we have to live with more general cases.

[arphaman]

That's probably the best solution then, I don't think declaring implicit new just for availability attribute is sound.

Does this work with self new as well?

clang/lib/AST/DeclObjC.cpp

833

const auto

836

const auto

clang/lib/Sema/SemaDeclAttr.cpp

6949

Please be consistent with the name, you are using ClassMessageReceiver, ClassReceiver and Receiver in different arguments in this patch.

6986

Comparisons to nullptr are redundant, you can just say S.NSAPIObj && ClassMessageReceiver. Same below.

[erik.pilkington]

Address @arphaman's review comments.

[erik.pilkington]

In D51189#1211910, @steven_wu wrote:

I feel like this is a much tricky situation than just new and init. Following example is the same situation.

__attribute__((objc_root_class))
@interface NSObject
- (void) foo;
- (void) bar;
@end

@implementation NSObject
- (void) foo {}
- (void) bar { [self foo]; }
@end

@interface MyObject : NSObject
- (void) foo __attribute__((unavailable));
@end

void test(MyObject *obj) {
  [obj bar];
}

We can do something about [NSObject new] because we know it's implementation but we have to live with more general cases.

I agree that the general case is impossible to properly diagnose, but I think its totally reasonable for us to special case this pattern with NSObject.

clang/lib/Sema/SemaDeclAttr.cpp

6949

Sure, sorry. I canonicalized on ClassReceiver.

[arphaman]

LGTM

clang/include/clang/AST/ASTContext.h

   QualType ObjCIdRedefinitionType;
   QualType ObjCClassRedefinitionType;
   QualType ObjCSelRedefinitionType;
 
   /// The identifier 'bool'.
   mutable IdentifierInfo *BoolName = nullptr;
 
   /// The identifier 'NSObject'.
-  IdentifierInfo *NSObjectName = nullptr;
+  mutable IdentifierInfo *NSObjectName = nullptr;
 
   /// The identifier 'NSCopying'.
   IdentifierInfo *NSCopyingName = nullptr;
 
   /// The identifier '__make_integer_seq'.
   mutable IdentifierInfo *MakeIntegerSeqName = nullptr;
 
   /// The identifier '__type_pack_element'.

   }
 
   /// Set the user-written type that redefines 'SEL'.
   void setObjCSelRedefinitionType(QualType RedefType) {
     ObjCSelRedefinitionType = RedefType;
   }
 
   /// Retrieve the identifier 'NSObject'.
-  IdentifierInfo *getNSObjectName() {
+  IdentifierInfo *getNSObjectName() const {
     if (!NSObjectName) {
       NSObjectName = &Idents.get("NSObject");
     }
 
     return NSObjectName;
   }
 
   /// Retrieve the identifier 'NSCopying'.

clang/include/clang/AST/DeclObjC.h

   void setLazyBody(uint64_t Offset) { Body = Offset; }
 
   CompoundStmt *getCompoundBody() { return (CompoundStmt*)getBody(); }
   void setBody(Stmt *B) { Body = B; }
 
   /// Returns whether this specific method is a definition.
   bool isThisDeclarationADefinition() const { return hasBody(); }
 
+  /// Is this method defined in the NSObject base class?
+  bool definedInNSObject(const ASTContext &) const;
+
   // Implement isa/cast/dyncast/etc.
   static bool classof(const Decl *D) { return classofKind(D->getKind()); }
   static bool classofKind(Kind K) { return K == ObjCMethod; }
 
   static DeclContext *castToDeclContext(const ObjCMethodDecl *D) {
     return static_cast<DeclContext *>(const_cast<ObjCMethodDecl*>(D));
   }
 

clang/include/clang/AST/NSAPI.h

Selector getSetObjectAtIndexedSubscriptSelector() const {
     return getOrInitSelector(Ids, setObjectAtIndexedSubscriptSel);
   }
 
   /// Returns selector for "isEqual:".
   Selector getIsEqualSelector() const {
     return getOrInitSelector(StringRef("isEqual"), isEqualSel);
   }
 
+  Selector getNewSelector() const {
+    return getOrInitNullarySelector("new", NewSel);
+  }
+
+  Selector getInitSelector() const {
+    return getOrInitNullarySelector("init", InitSel);
+  }
+
   /// Enumerates the NSNumber methods used to generate literals.
   enum NSNumberLiteralMethodKind {
     NSNumberWithChar,
     NSNumberWithUnsignedChar,
     NSNumberWithShort,
     NSNumberWithUnsignedShort,
     NSNumberWithInt,
     NSNumberWithUnsignedInt,
public:
   bool isSubclassOfNSClass(ObjCInterfaceDecl *InterfaceDecl,
                            NSClassIdKindKind NSClassKind) const;
 
 private:
   bool isObjCTypedef(QualType T, StringRef name, IdentifierInfo *&II) const;
   bool isObjCEnumerator(const Expr *E,
                         StringRef name, IdentifierInfo *&II) const;
   Selector getOrInitSelector(ArrayRef<StringRef> Ids, Selector &Sel) const;
+  Selector getOrInitNullarySelector(StringRef Id, Selector &Sel) const;
 
   ASTContext &Ctx;
 
   mutable IdentifierInfo *ClassIds[NumClassIds];
 
   mutable Selector NSStringSelectors[NumNSStringMethods];
 
   /// The selectors for Objective-C NSArray methods.
   mutable Selector NSArraySelectors[NumNSArrayMethods];
 
   /// The selectors for Objective-C NSDictionary methods.
   mutable Selector NSDictionarySelectors[NumNSDictionaryMethods];
 
   /// The selectors for Objective-C NSSet methods.
   mutable Selector NSSetSelectors[NumNSSetMethods];
 
   /// The Objective-C NSNumber selectors used to create NSNumber literals.
   mutable Selector NSNumberClassSelectors[NumNSNumberLiteralMethods];
   mutable Selector NSNumberInstanceSelectors[NumNSNumberLiteralMethods];
 
   mutable Selector objectForKeyedSubscriptSel, objectAtIndexedSubscriptSel,
                    setObjectForKeyedSubscriptSel,setObjectAtIndexedSubscriptSel,
-                   isEqualSel;
+                   isEqualSel, InitSel, NewSel;
 
   mutable IdentifierInfo *BOOLId, *NSIntegerId, *NSUIntegerId;
   mutable IdentifierInfo *NSASCIIStringEncodingId, *NSUTF8StringEncodingId;
 };
 
 }  // end namespace clang
 
 #endif // LLVM_CLANG_AST_NSAPI_H

clang/include/clang/Sema/Sema.h

     DelayedDiagnostics.popUndelayed(state);
   }
 
   void redelayDiagnostics(sema::DelayedDiagnosticPool &pool);
 
   void DiagnoseAvailabilityOfDecl(NamedDecl *D, ArrayRef<SourceLocation> Locs,
                                   const ObjCInterfaceDecl *UnknownObjCClass,
                                   bool ObjCPropertyAccess,
-                                  bool AvoidPartialAvailabilityChecks = false);
+                                  bool AvoidPartialAvailabilityChecks = false,
+                                  ObjCInterfaceDecl *ClassReceiver = nullptr);
 
   bool makeUnavailableInSystemHeader(SourceLocation loc,
                                      UnavailableAttr::ImplicitReason reason);
 
   /// Issue any -Wunguarded-availability warnings in \c FD
   void DiagnoseUnguardedAvailabilityViolations(Decl *FD);
 
   //===--------------------------------------------------------------------===//
   // Expression Parsing Callbacks: SemaExpr.cpp.
 
   bool CanUseDecl(NamedDecl *D, bool TreatUnavailableAsInvalid);
   bool DiagnoseUseOfDecl(NamedDecl *D, ArrayRef<SourceLocation> Locs,
                          const ObjCInterfaceDecl *UnknownObjCClass = nullptr,
                          bool ObjCPropertyAccess = false,
-                         bool AvoidPartialAvailabilityChecks = false);
+                         bool AvoidPartialAvailabilityChecks = false,
+                         ObjCInterfaceDecl *ClassReciever = nullptr);
   void NoteDeletedFunction(FunctionDecl *FD);
   void NoteDeletedInheritingConstructor(CXXConstructorDecl *CD);
   std::string getDeletedOrUnavailableSuffix(const FunctionDecl *FD);
   bool DiagnosePropertyAccessorMismatch(ObjCPropertyDecl *PD,
                                         ObjCMethodDecl *Getter,
                                         SourceLocation Loc);
   void DiagnoseSentinelCalls(NamedDecl *D, SourceLocation Loc,
                              ArrayRef<Expr *> Args);

clang/lib/AST/DeclObjC.cpp

                                     Selector(), QualType(), nullptr, nullptr);
 }
 
 bool ObjCMethodDecl::isThisDeclarationADesignatedInitializer() const {
   return getMethodFamily() == OMF_init &&
       hasAttr<ObjCDesignatedInitializerAttr>();
 }
 
+bool ObjCMethodDecl::definedInNSObject(const ASTContext &Ctx) const {
+  if (const auto *PD = dyn_cast<const ObjCProtocolDecl>(getDeclContext()))
+    return PD->getIdentifier() == Ctx.getNSObjectName();
+  if (const auto *ID = dyn_cast<const ObjCInterfaceDecl>(getDeclContext()))
+    return ID->getIdentifier() == Ctx.getNSObjectName();
+  return false;
+}
+
 bool ObjCMethodDecl::isDesignatedInitializerForTheInterface(
     const ObjCMethodDecl **InitMethod) const {
   if (getMethodFamily() != OMF_init)
     return false;
   const DeclContext *DC = getDeclContext();
   if (isa<ObjCProtocolDecl>(DC))
     return false;
   if (const ObjCInterfaceDecl *ID = getClassInterface())

clang/lib/AST/NSAPI.cpp

     SmallVector<IdentifierInfo *, 4> Idents;
     for (ArrayRef<StringRef>::const_iterator
            I = Ids.begin(), E = Ids.end(); I != E; ++I)
       Idents.push_back(&Ctx.Idents.get(*I));
     Sel = Ctx.Selectors.getSelector(Idents.size(), Idents.data());
   }
   return Sel;
 }
+
+Selector NSAPI::getOrInitNullarySelector(StringRef Id, Selector &Sel) const {
+  if (Sel.isNull()) {
+    IdentifierInfo *Ident = &Ctx.Idents.get(Id);
+    Sel = Ctx.Selectors.getSelector(0, &Ident);
+  }
+  return Sel;
+}

clang/lib/Sema/SemaDeclAttr.cpp

         size_t suffix = RealizedPlatform.rfind("_app_extension");
         if (suffix != StringRef::npos)
           RealizedPlatform = RealizedPlatform.slice(0, suffix);
       }
 
       StringRef TargetPlatform = Context.getTargetInfo().getPlatformName();
 
       // Match the platform name.
       if (RealizedPlatform == TargetPlatform)
         return Avail;
     }
   }
   return nullptr;
 }
 
 /// The diagnostic we should emit for \c D, and the declaration that
 /// originated it, or \c AR_Available.
 ///
 /// \param D The declaration to check.
 /// \param Message If non-null, this will be populated with the message from
 /// the availability attribute that is selected.
+/// \param ClassReceiver If we're checking the the method of a class message
+/// send, the class. Otherwise nullptr.
 static std::pair<AvailabilityResult, const NamedDecl *>
-ShouldDiagnoseAvailabilityOfDecl(const NamedDecl *D, std::string *Message) {
+ShouldDiagnoseAvailabilityOfDecl(Sema &S, const NamedDecl *D,
+                                 std::string *Message,
+                                 ObjCInterfaceDecl *ClassReceiver) {
   AvailabilityResult Result = D->getAvailability(Message);
 
   // For typedefs, if the typedef declaration appears available look
   // to the underlying type to see if it is more restrictive.
   while (const auto *TD = dyn_cast<TypedefNameDecl>(D)) {
     if (Result == AR_Available) {
       if (const auto *TT = TD->getUnderlyingType()->getAs<TagType>()) {
         D = TT->getDecl();
         Result = D->getAvailability(Message);
         continue;
       }
     }
     break;
   }
 
   // Forward class declarations get their attributes from their definition.
   if (const auto *IDecl = dyn_cast<ObjCInterfaceDecl>(D)) {
     if (IDecl->getDefinition()) {
       D = IDecl->getDefinition();
       Result = D->getAvailability(Message);
     }
   }
 
   if (const auto *ECD = dyn_cast<EnumConstantDecl>(D))
     if (Result == AR_Available) {
       const DeclContext *DC = ECD->getDeclContext();
       if (const auto *TheEnumDecl = dyn_cast<EnumDecl>(DC)) {
         Result = TheEnumDecl->getAvailability(Message);
         D = TheEnumDecl;
       }
     }
 
+  // For +new, infer availability from -init.
+  if (const auto *MD = dyn_cast<ObjCMethodDecl>(D)) {
+    if (S.NSAPIObj && ClassReceiver) {
+      ObjCMethodDecl *Init = ClassReceiver->lookupInstanceMethod(
+          S.NSAPIObj->getInitSelector());
+      if (Init && Result == AR_Available && MD->isClassMethod() &&
+          MD->getSelector() == S.NSAPIObj->getNewSelector() &&
+          MD->definedInNSObject(S.getASTContext())) {
+        Result = Init->getAvailability(Message);
+        D = Init;
+      }
+    }
+  }
+
   return {Result, D};
 }
 
 
 /// whether we should emit a diagnostic for \c K and \c DeclVersion in
 /// the context of \c Ctx. For example, we should emit an unavailable diagnostic
 /// in a deprecated context, but not the other way around.
 static bool ShouldDiagnoseAvailabilityInContext(Sema &S, AvailabilityResult K,

 
   Sema &SemaRef;
   Decl *Ctx;
 
   /// Stack of potentially nested 'if (@available(...))'s.
   SmallVector<VersionTuple, 8> AvailabilityStack;
   SmallVector<const Stmt *, 16> StmtStack;
 
-  void DiagnoseDeclAvailability(NamedDecl *D, SourceRange Range);
+  void DiagnoseDeclAvailability(NamedDecl *D, SourceRange Range,
+                                ObjCInterfaceDecl *ClassReceiver = nullptr);
 
 public:
   DiagnoseUnguardedAvailability(Sema &SemaRef, Decl *Ctx)
       : SemaRef(SemaRef), Ctx(Ctx) {
     AvailabilityStack.push_back(
         SemaRef.Context.getTargetInfo().getPlatformMinVersion());
   }
 

 
   bool VisitObjCPropertyRefExpr(ObjCPropertyRefExpr *PRE) {
     if (PRE->isClassReceiver())
       DiagnoseDeclAvailability(PRE->getClassReceiver(), PRE->getReceiverLocation());
     return true;
   }
 
   bool VisitObjCMessageExpr(ObjCMessageExpr *Msg) {
-    if (ObjCMethodDecl *D = Msg->getMethodDecl())
+    if (ObjCMethodDecl *D = Msg->getMethodDecl()) {
+      ObjCInterfaceDecl *ID = nullptr;
+      QualType ReceiverTy = Msg->getClassReceiver();
+      if (!ReceiverTy.isNull() && ReceiverTy->getAsObjCInterfaceType())
+        ID = ReceiverTy->getAsObjCInterfaceType()->getInterface();
+
       DiagnoseDeclAvailability(
-          D, SourceRange(Msg->getSelectorStartLoc(), Msg->getEndLoc()));
+          D, SourceRange(Msg->getSelectorStartLoc(), Msg->getEndLoc()), ID);
+    }
     return true;
   }
 
   bool VisitDeclRefExpr(DeclRefExpr *DRE) {
     DiagnoseDeclAvailability(DRE->getDecl(),
                              SourceRange(DRE->getBeginLoc(), DRE->getEndLoc()));
     return true;
   }

         << (!SemaRef.getLangOpts().ObjC1);
     return true;
   }
 
   bool VisitTypeLoc(TypeLoc Ty);
 };
 
 void DiagnoseUnguardedAvailability::DiagnoseDeclAvailability(
-    NamedDecl *D, SourceRange Range) {
+    NamedDecl *D, SourceRange Range, ObjCInterfaceDecl *ReceiverClass) {
   AvailabilityResult Result;
   const NamedDecl *OffendingDecl;
   std::tie(Result, OffendingDecl) =
-    ShouldDiagnoseAvailabilityOfDecl(D, nullptr);
+      ShouldDiagnoseAvailabilityOfDecl(SemaRef, D, nullptr, ReceiverClass);
   if (Result != AR_Available) {
     // All other diagnostic kinds have already been handled in
     // DiagnoseAvailabilityOfDecl.
     if (Result != AR_NotYetIntroduced)
       return;
 
     const AvailabilityAttr *AA =
       getAttrForPlatform(SemaRef.getASTContext(), OffendingDecl);

 
   DiagnoseUnguardedAvailability(*this, D).IssueDiagnostics(Body);
 }
 
 void Sema::DiagnoseAvailabilityOfDecl(NamedDecl *D,
                                       ArrayRef<SourceLocation> Locs,
                                       const ObjCInterfaceDecl *UnknownObjCClass,
                                       bool ObjCPropertyAccess,
-                                      bool AvoidPartialAvailabilityChecks) {
+                                      bool AvoidPartialAvailabilityChecks,
+                                      ObjCInterfaceDecl *ClassReceiver) {
   std::string Message;
   AvailabilityResult Result;
   const NamedDecl* OffendingDecl;
   // See if this declaration is unavailable, deprecated, or partial.
-  std::tie(Result, OffendingDecl) = ShouldDiagnoseAvailabilityOfDecl(D, &Message);
+  std::tie(Result, OffendingDecl) =
+      ShouldDiagnoseAvailabilityOfDecl(*this, D, &Message, ClassReceiver);
   if (Result == AR_Available)
     return;
 
   if (Result == AR_NotYetIntroduced) {
     if (AvoidPartialAvailabilityChecks)
       return;
 
     // We need to know the @available context in the current function to

clang/lib/Sema/SemaExpr.cpp

 /// function is being used.
 ///
 /// \returns true if there was an error (this declaration cannot be
 /// referenced), false otherwise.
 ///
 bool Sema::DiagnoseUseOfDecl(NamedDecl *D, ArrayRef<SourceLocation> Locs,
                              const ObjCInterfaceDecl *UnknownObjCClass,
                              bool ObjCPropertyAccess,
-                             bool AvoidPartialAvailabilityChecks) {
+                             bool AvoidPartialAvailabilityChecks,
+                             ObjCInterfaceDecl *ClassReceiver) {
   SourceLocation Loc = Locs.front();
   if (getLangOpts().CPlusPlus && isa<FunctionDecl>(D)) {
     // If there were any diagnostics suppressed by template argument deduction,
     // emit them now.
     auto Pos = SuppressedDiagnostics.find(D->getCanonicalDecl());
     if (Pos != SuppressedDiagnostics.end()) {
       for (const PartialDiagnosticAt &Suppressed : Pos->second)
         Diag(Suppressed.first, Suppressed.second);
if (LangOpts.OpenMP && DRD && !CurContext->containsDecl(D) &&
       isa<VarDecl>(D)) {
     Diag(Loc, diag::err_omp_wrong_var_in_declare_reduction)
         << getCurFunction()->HasOMPDeclareReductionCombiner;
     Diag(D->getLocation(), diag::note_entity_declared_at) << D;
     return true;
   }
 
   DiagnoseAvailabilityOfDecl(D, Locs, UnknownObjCClass, ObjCPropertyAccess,
-                             AvoidPartialAvailabilityChecks);
+                             AvoidPartialAvailabilityChecks, ClassReceiver);
 
   DiagnoseUnusedOfDecl(*this, D, Loc);
 
   diagnoseUseOfInternalDeclInInlineFunction(*this, D, Loc);
 
   return false;
 }
 

clang/lib/Sema/SemaExprObjC.cpp

     }
     if (!Method)
       Method = Class->lookupClassMethod(Sel);
 
     // If we have an implementation in scope, check "private" methods.
     if (!Method)
       Method = Class->lookupPrivateClassMethod(Sel);
 
-    if (Method && DiagnoseUseOfDecl(Method, SelectorSlotLocs))
+    if (Method && DiagnoseUseOfDecl(Method, SelectorSlotLocs,
+                                    nullptr, false, false, Class))
       return ExprError();
   }
 
   // Check the argument types and determine the result type.
   QualType ReturnType;
   ExprValueKind VK = VK_RValue;
 
   unsigned NumArgs = ArgsIn.size();

               << Method->getSelector() << Sel;
             Diag(Method->getLocation(), diag::note_method_declared_at)
               << Method->getDeclName();
           }
         }
       } else {
         if (ObjCMethodDecl *CurMeth = getCurMethodDecl()) {
           if (ObjCInterfaceDecl *ClassDecl = CurMeth->getClassInterface()) {
+            // FIXME: Is this correct? Why are we assuming that a message to
+            // Class will call a method in the current interface?
+
             // First check the public methods in the class interface.
             Method = ClassDecl->lookupClassMethod(Sel);
 
             if (!Method)
               Method = ClassDecl->lookupPrivateClassMethod(Sel);
+
+            if (Method && DiagnoseUseOfDecl(Method, SelectorSlotLocs, nullptr,
+                                            false, false, ClassDecl))
+              return ExprError();
           }
-          if (Method && DiagnoseUseOfDecl(Method, SelectorSlotLocs))
-            return ExprError();
         }
         if (!Method) {
           // If not messaging 'self', look for any factory method named 'Sel'.
           if (!Receiver || !isSelfExpr(Receiver)) {
             // If no class (factory) method was found, check if an _instance_
             // method of the same name exists in the root class only.
             SmallVector<ObjCMethodDecl*, 4> Methods;
             CollectMultipleMethodsInGlobalPool(Sel, Methods,

clang/test/SemaObjC/infer-availability-from-init.m

+// RUN: %clang_cc1 -triple x86_64-apple-macosx-10.9 -Wunguarded-availability -fblocks -fsyntax-only -verify %s
+
+__attribute__((objc_root_class))
+@interface NSObject
++(instancetype)new;
+-(instancetype)init;
+@end
+
+@interface MyObject : NSObject
+-(instancetype)init __attribute__((unavailable)); // expected-note{{'init' has been explicitly marked unavailable here}}
+@end
+
+void usemyobject() {
+  [MyObject new]; // expected-error{{'new' is unavailable}}
+}
+
+@interface MyOtherObject : NSObject
++(instancetype)init __attribute__((unavailable));
++(instancetype)new;
+@end
+
+void usemyotherobject() {
+  [MyOtherObject new]; // no error; new is overrideen.
+}
+
+@interface NotGoodOverride : NSObject
++(instancetype)init __attribute__((unavailable));
+-(instancetype)new;
++(instancetype)new: (int)x;
+@end
+
+void usenotgoodoverride() {
+  [NotGoodOverride new]; // no error
+}
+
+@interface NotNSObject
++(instancetype)new;
+-(instancetype)init;
+@end
+
+@interface NotMyObject : NotNSObject
+-(instancetype)init __attribute__((unavailable));
+@end
+
+void usenotmyobject() {
+  [NotMyObject new]; // no error; this isn't NSObject
+}
+
+@interface FromSelf : NSObject
+-(instancetype)init __attribute__((unavailable)); // expected-note {{'init' has been explicitly marked unavailable here}}
++(FromSelf*)another_one;
+@end
+
+@implementation FromSelf
++(FromSelf*)another_one {
+  [self new]; // expected-error{{'new' is unavailable}}
+}
+@end