Index: include/clang/Basic/Attr.td
===================================================================
--- include/clang/Basic/Attr.td
+++ include/clang/Basic/Attr.td
@@ -102,13 +102,6 @@
                                        [{S->isInstanceMethod()}],
                                        "Objective-C instance methods">;
 
-def ObjCInterfaceDeclInitMethod : SubsetSubject<ObjCMethod,
-                               [{S->getMethodFamily() == OMF_init &&
-                                 (isa<ObjCInterfaceDecl>(S->getDeclContext()) ||
-                                  (isa<ObjCCategoryDecl>(S->getDeclContext()) &&
-            cast<ObjCCategoryDecl>(S->getDeclContext())->IsClassExtension()))}],
-            "init methods of interface or class extension declarations">;
-
 def Struct : SubsetSubject<Record,
                            [{!S->isUnion()}], "structs">;
 
@@ -1786,7 +1779,7 @@
 
 def ObjCDesignatedInitializer : Attr {
   let Spellings = [Clang<"objc_designated_initializer">];
-  let Subjects = SubjectList<[ObjCInterfaceDeclInitMethod], ErrorDiag>;
+  let Subjects = SubjectList<[ObjCMethod], ErrorDiag>;
   let Documentation = [Undocumented];
 }
 
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -3481,6 +3481,9 @@
 def warn_objc_implementation_missing_designated_init_override : Warning<
   "method override for the designated initializer of the superclass %objcinstance0 not found">,
   InGroup<ObjCDesignatedInit>;
+def err_designated_init_attr_non_init : Error<
+  "'objc_designated_initializer' attribute only applies to init methods "
+  "of interface or class extension declarations">;
 
 // objc_bridge attribute diagnostics.
 def err_objc_attr_not_id : Error<
Index: lib/Sema/SemaDeclAttr.cpp
===================================================================
--- lib/Sema/SemaDeclAttr.cpp
+++ lib/Sema/SemaDeclAttr.cpp
@@ -5249,11 +5249,22 @@
 
 static void handleObjCDesignatedInitializer(Sema &S, Decl *D,
                                             const ParsedAttr &AL) {
+  DeclContext *Ctx = D->getDeclContext();
+
+  // This attribute can only be applied to methods in interfaces or class
+  // extensions.
+  if (!isa<ObjCInterfaceDecl>(Ctx) &&
+      !(isa<ObjCCategoryDecl>(Ctx) &&
+        cast<ObjCCategoryDecl>(Ctx)->IsClassExtension())) {
+    S.Diag(D->getLocation(), diag::err_designated_init_attr_non_init);
+    return;
+  }
+
   ObjCInterfaceDecl *IFace;
-  if (auto *CatDecl = dyn_cast<ObjCCategoryDecl>(D->getDeclContext()))
+  if (auto *CatDecl = dyn_cast<ObjCCategoryDecl>(Ctx))
     IFace = CatDecl->getClassInterface();
   else
-    IFace = cast<ObjCInterfaceDecl>(D->getDeclContext());
+    IFace = cast<ObjCInterfaceDecl>(Ctx);
 
   if (!IFace)
     return;
@@ -7243,6 +7254,17 @@
       }
     }
   }
+
+  // Do this check after processing D's attributes because the attribute
+  // objc_method_family can change whether the given method is in the init
+  // family, and it can be applied after objc_designated_initializer. This is a
+  // bit of a hack, but we need it to be compatible with versions of clang that
+  // processed the attribute list in the wrong order.
+  if (D->hasAttr<ObjCDesignatedInitializerAttr>() &&
+      cast<ObjCMethodDecl>(D)->getMethodFamily() != OMF_init) {
+    Diag(D->getLocation(), diag::err_designated_init_attr_non_init);
+    D->dropAttr<ObjCDesignatedInitializerAttr>();
+  }
 }
 
 // Helper for delayed processing TransparentUnion attribute.
Index: test/Misc/pragma-attribute-supported-attributes-list.test
===================================================================
--- test/Misc/pragma-attribute-supported-attributes-list.test
+++ test/Misc/pragma-attribute-supported-attributes-list.test
@@ -97,6 +97,7 @@
 // CHECK-NEXT: ObjCBridge (SubjectMatchRule_record, SubjectMatchRule_type_alias)
 // CHECK-NEXT: ObjCBridgeMutable (SubjectMatchRule_record)
 // CHECK-NEXT: ObjCBridgeRelated (SubjectMatchRule_record)
+// CHECK-NEXT: ObjCDesignatedInitializer (SubjectMatchRule_objc_method)
 // CHECK-NEXT: ObjCException (SubjectMatchRule_objc_interface)
 // CHECK-NEXT: ObjCExplicitProtocolImpl (SubjectMatchRule_objc_protocol)
 // CHECK-NEXT: ObjCExternallyRetained (SubjectMatchRule_variable_not_is_parameter, SubjectMatchRule_function, SubjectMatchRule_block, SubjectMatchRule_objc_method)
Index: test/SemaObjC/attr-designated-init.m
===================================================================
--- test/SemaObjC/attr-designated-init.m
+++ test/SemaObjC/attr-designated-init.m
@@ -3,7 +3,7 @@
 #define NS_DESIGNATED_INITIALIZER __attribute__((objc_designated_initializer))
 #define NS_UNAVAILABLE __attribute__((unavailable))
 
-void fnfoo(void) NS_DESIGNATED_INITIALIZER; // expected-error {{only applies to init methods of interface or class extension declarations}}
+void fnfoo(void) NS_DESIGNATED_INITIALIZER; // expected-error {{'objc_designated_initializer' attribute only applies to Objective-C methods}}
 
 @protocol P1
 -(id)init NS_DESIGNATED_INITIALIZER; // expected-error {{only applies to init methods of interface or class extension declarations}}
@@ -428,3 +428,16 @@
 @interface CategoryForMissingInterface(Cat) // expected-error{{cannot find interface declaration}}
 - (instancetype)init NS_DESIGNATED_INITIALIZER; // expected-error{{only applies to init methods of interface or class extension declarations}}
 @end
+
+@interface TwoAttrs
+-(instancetype)foo
+    __attribute__((objc_designated_initializer))
+    __attribute__((objc_method_family(init)));
+-(instancetype)bar
+    __attribute__((objc_method_family(init)))
+    __attribute__((objc_designated_initializer));
+-(instancetype)baz
+  __attribute__((objc_designated_initializer, objc_method_family(init)));
+-(instancetype)quux
+  __attribute__((objc_method_family(init), objc_designated_initializer));
+@end