[ClangImporter] If enum_extensibility was removed, it's not an enum.

lib/ClangImporter/ImportEnumInfo.cpp

@@ -60,6 +60,18 @@ void EnumInfo::classifyEnum(ASTContext &ctx, const clang::EnumDecl *decl,
     return;
   }
 
+  // If API notes have /removed/ a FlagEnum or EnumExtensibility attribute,
+  // then we don't need to check the macros.
+  for (auto *attr : decl->specific_attrs<clang::SwiftVersionedAttr>()) {
+    if (!attr->getVersion().empty())
+      continue;
+    if (isa<clang::FlagEnumAttr>(attr->getAttrToAdd()) ||
+        isa<clang::EnumExtensibilityAttr>(attr->getAttrToAdd())) {
+      kind = EnumKind::Unknown;
+      return;
+    }
+  }
+
   // Was the enum declared using *_ENUM or *_OPTIONS?
   // FIXME: Stop using these once flag_enum and enum_extensibility
   // have been adopted everywhere, or at least relegate them to Swift 3 mode

test/ClangImporter/enum.swift

@@ -11,6 +11,7 @@
 
 import Foundation
 import user_objc
+import enums_using_attributes
 
 // NS_ENUM
 var mince = NSRuncingMode.mince
@@ -149,6 +150,7 @@ var topLevelCaseName = RuncingMince // expected-error{{}}
 #endif
 
 let _: EnumViaAttribute = .first
+let _: CFEnumWithAttr = .first
 
 // NS_OPTIONS
 var withMince: NSRuncingOptions = .enableMince
@@ -196,6 +198,7 @@ let objcFlags: objc_flags = [.taggedPointer, .swiftRefcount]
 
 let optionsWithSwiftName: NSOptionsAlsoGetSwiftName = .Case
 let optionsViaAttribute: OptionsViaAttribute = [.first, .second]
+let optionsViaAttribute2: CFOptionsWithAttr = [.first]
 
 // <rdar://problem/25168818> Don't import None members in NS_OPTIONS types
 #if !IRGEN
@@ -211,3 +214,10 @@ _ = EmptySet3.None
 // Just use this type, making sure that its case alias doesn't cause problems.
 // rdar://problem/30401506
 _ = EnumWithAwkwardDeprecations.normalCase1
+
+#if !IRGEN
+let _: UnknownEnumThanksToAPINotes = .first // expected-error {{has no member 'first'}}
+let _: UnknownOptionsThanksToAPINotes = .first // expected-error {{has no member 'first'}}
+#endif
+let _ = UnknownEnumThanksToAPINotesFirst
+let _ = UnknownOptionsThanksToAPINotesFirst

test/Inputs/clang-importer-sdk/usr/include/enums_using_attributes.apinotes

@@ -0,0 +1,6 @@
+Name: enums_using_attributes
+Tags:
+- Name: UnknownEnumThanksToAPINotes
+  EnumKind: none
+- Name: UnknownOptionsThanksToAPINotes
+  EnumKind: none

test/Inputs/clang-importer-sdk/usr/include/enums_using_attributes.h

@@ -0,0 +1,18 @@
+#define CF_ENUM(_type, _name) enum _name : _type _name; \
+  enum __attribute__((enum_extensibility(open))) _name : _type
+#define CF_OPTIONS(_type, _name) enum _name : _type _name; \
+  enum __attribute__((enum_extensibility(open), flag_enum)) _name : _type
+
+typedef CF_ENUM(int, CFEnumWithAttr) {
+  CFEnumWithAttrFirst = 1,
+};
+typedef CF_ENUM(int, UnknownEnumThanksToAPINotes) {
+  UnknownEnumThanksToAPINotesFirst = 1,
+};
+
+typedef CF_OPTIONS(int, CFOptionsWithAttr) {
+  CFOptionsWithAttrFirst = 1,
+};
+typedef CF_OPTIONS(int, UnknownOptionsThanksToAPINotes) {
+  UnknownOptionsThanksToAPINotesFirst = 1,
+};

test/Inputs/clang-importer-sdk/usr/include/module.map

@@ -98,6 +98,10 @@ module objc_structs {
   export *
 }
 
+module enums_using_attributes {
+  header "enums_using_attributes.h"
+}
+
 module errors {
   header "errors.h"
   export *