[cxx-interop] Add fix for corner case where NS_OPTIONS typedef has to be desugared

lib/ClangImporter/ClangImporter.cpp

@@ -6877,14 +6877,25 @@ const clang::TypedefType *ClangImporter::getTypeDefForCXXCFOptionsDefinition(
   if (!enumDecl->getDeclName().isEmpty())
     return nullptr;
 
-  if (auto typedefType = dyn_cast<clang::TypedefType>(
-          enumDecl->getIntegerType().getTypePtr())) {
-    if (auto enumExtensibilityAttr =
-            typedefType->getDecl()->getAttr<clang::EnumExtensibilityAttr>();
-        enumExtensibilityAttr &&
+  const clang::ElaboratedType *elaboratedType =
+      dyn_cast<clang::ElaboratedType>(enumDecl->getIntegerType().getTypePtr());
+  if (auto typedefType =
+          elaboratedType
+              ? dyn_cast<clang::TypedefType>(elaboratedType->desugar())
+              : dyn_cast<clang::TypedefType>(
+                    enumDecl->getIntegerType().getTypePtr())) {
+    auto enumExtensibilityAttr =
+        elaboratedType
+            ? enumDecl->getAttr<clang::EnumExtensibilityAttr>()
+            : typedefType->getDecl()->getAttr<clang::EnumExtensibilityAttr>();
+    const bool hasFlagEnumAttr =
+        elaboratedType ? enumDecl->hasAttr<clang::FlagEnumAttr>()
+                       : typedefType->getDecl()->hasAttr<clang::FlagEnumAttr>();
+
+    if (enumExtensibilityAttr &&
         enumExtensibilityAttr->getExtensibility() ==
             clang::EnumExtensibilityAttr::Open &&
-        typedefType->getDecl()->hasAttr<clang::FlagEnumAttr>()) {
+        hasFlagEnumAttr) {
       return Impl.isUnavailableInSwift(typedefType->getDecl()) ? typedefType
                                                                : nullptr;
     }

test/Interop/Cxx/objc-correctness/Inputs/NSOptionsMangling.apinotes

@@ -0,0 +1,5 @@
+---
+Name: NSOptionsMangling
+Tags:
+- Name: UIControlState
+  SwiftName: UIControl.State

test/Interop/Cxx/objc-correctness/Inputs/NSOptionsMangling.h

@@ -0,0 +1,22 @@
+#define __CF_OPTIONS_ATTRIBUTES __attribute__((flag_enum,enum_extensibility(open)))
+#if (__cplusplus)
+#define CF_OPTIONS(_type, _name) __attribute__((availability(swift,unavailable))) _type _name; enum __CF_OPTIONS_ATTRIBUTES : _name
+#else
+#define CF_OPTIONS(_type, _name) enum __CF_OPTIONS_ATTRIBUTES _name : _type _name; enum _name : _type
+#endif
+
+typedef CF_OPTIONS(unsigned, UIControlState) { UIControlStateNormal = 0 };
+
+#ifdef __cplusplus
+#define UIKIT_EXTERN extern "C" __attribute__((visibility ("default")))
+#else
+#define UIKIT_EXTERN extern __attribute__((visibility ("default")))
+#endif
+
+@interface UIView
+@end
+
+UIKIT_EXTERN
+@interface UIControl : UIView
+@end
+

test/Interop/Cxx/objc-correctness/Inputs/module.modulemap

@@ -9,3 +9,6 @@ module CxxClassWithNSStringInit [extern_c] {
   requires cplusplus
 }
 
+module NSOptionsMangling {
+  header "NSOptionsMangling.h"
+}

test/Interop/Cxx/objc-correctness/ns-options-mangling.swift

@@ -0,0 +1,11 @@
+// RUN: %target-swift-frontend -I %S/Inputs -c -cxx-interoperability-mode=swift-5.9 %s -S -o - | %FileCheck %s
+// RUN: %target-swift-frontend -I %S/Inputs -c %s -S -o - | %FileCheck %s
+
+// REQUIRES: objc_interop
+
+// CHECK: _$sSo14UIControlStateV4main7FooableACMc
+// The following check is to ensure the conformance is mangled properly:
+// protocol conformance descriptor for __C.UIControlState : main.Fooable in main
+import NSOptionsMangling
+protocol Fooable { }
+extension UIControl.State: Fooable {}