[cxx-interop] Import ObjCPropertyDecl of type NS_OPTIONS fields a struct type

Try importing ObjCPropertyDecl field types the C++-Interop-NS_OPTIONS
way. This will fix cases such as:

```
import UIKit

func f(gesture: UISwipeGestureRecognizer,
       direction: UISwipeGestureRecognizer.Direction) {
  gesture.direction = direction // error
}
```

because it will make sure the field inside class UIGestureRecognizer is
of the enum-struct type and not the typedef-rawValue type when importing
an ObjC class.

Author: plotfi

lib/ClangImporter/ImportDecl.cpp

@@ -5211,7 +5211,11 @@ namespace {
         }
       }
 
-      auto importedType = Impl.importPropertyType(decl, isInSystemModule(dc));
+      auto fieldType = decl->getType();
+      ImportedType importedType = tryImportOptionsTypeForField(fieldType, Impl);
+
+      if (!importedType)
+        importedType = Impl.importPropertyType(decl, isInSystemModule(dc));
       if (!importedType) {
         Impl.addImportDiagnostic(
             decl, Diagnostic(diag::objc_property_not_imported, decl),

lib/ClangImporter/ImportType.cpp

@@ -3224,6 +3224,9 @@ ImportedType ClangImporter::Implementation::importMethodParamsAndReturnType(
           importedType.isImplicitlyUnwrapped()};
 }
 
+ImportedType tryImportOptionsTypeForField(const clang::QualType type,
+                                          ClangImporter::Implementation &Impl);
+
 ImportedType ClangImporter::Implementation::importAccessorParamsAndReturnType(
     const DeclContext *dc, const clang::ObjCPropertyDecl *property,
     const clang::ObjCMethodDecl *clangDecl, bool isFromSystemModule,
@@ -3247,9 +3250,13 @@ ImportedType ClangImporter::Implementation::importAccessorParamsAndReturnType(
   DeclContext *origDC = importDeclContextOf(property,
                                             property->getDeclContext());
   assert(origDC);
+  auto fieldType = isGetter ? clangDecl->getReturnType() : clangDecl->getParamDecl(0)->getType();
+  ImportedType importedNSOptionsType = tryImportOptionsTypeForField(fieldType, *this);
 
   // Import the property type, independent of what kind of accessor this is.
   auto importedType = importPropertyType(property, isFromSystemModule);
+  if (importedNSOptionsType)
+    importedType = importedNSOptionsType;
   if (!importedType)
     return {Type(), false};
 

test/Interop/Cxx/enum/Inputs/c-enums-NS_OPTIONS.h

@@ -82,6 +82,10 @@ struct HasNSOptionField {
   Bar bar;
 };
 
+@interface HasNSOptionFieldObjC
+@property Bar bar;
+@end
+
 Baz CFunctionReturningNSOption();
 void CFunctionTakingNSOption(Baz);
 

test/Interop/Cxx/enum/c-enums-NS_OPTIONS.swift

@@ -25,3 +25,7 @@ import CenumsNSOptions
 // CHECK: struct HasNSOptionField {
 // CHECK:   var bar: Bar
 // CHECK: }
+
+// CHECK: class HasNSOptionFieldObjC {
+// CHECK:   var bar: Bar
+// CHECK: }