[cxx-interop] Add anonymous enum logic to importFunctionReturnType().

Author: zoecarver

lib/ClangImporter/ImportType.cpp

@@ -2091,6 +2091,20 @@ ImportedType ClangImporter::Implementation::importFunctionReturnType(
           ->isTemplateTypeParmType())
     OptionalityOfReturn = OTK_None;
 
+  if (auto typedefType = dyn_cast<clang::TypedefType>(clangDecl->getReturnType().getTypePtr())) {
+    if (isUnavailableInSwift(typedefType->getDecl())) {
+      if (auto clangEnum = findAnonymousEnumForTypedef(SwiftContext, typedefType)) {
+        // If this fails, it means that we need a stronger predicate for
+        // determining the relationship between an enum and typedef.
+        assert(clangEnum.getValue()->getIntegerType()->getCanonicalTypeInternal() ==
+               typedefType->getCanonicalTypeInternal());
+        if (auto swiftEnum = importDecl(*clangEnum, CurrentVersion)) {
+          return {cast<NominalTypeDecl>(swiftEnum)->getDeclaredType(), false};
+        }
+      }
+    }
+  }
+
   // Import the result type.
   return importType(clangDecl->getReturnType(),
                     (isAuditedResult ? ImportTypeKind::AuditedResult

test/Interop/Cxx/enum/Inputs/anonymous-with-swift-name.h

@@ -24,6 +24,10 @@ inline CFColorMask useCFColorMask(CFColorMask mask) { return mask; }
 
 struct ParentStruct { };
 
+inline CFColorMask renameCFColorMask(ParentStruct parent)
+    __attribute__((swift_name("ParentStruct.childFn(self:)")))
+{ return kSOColorMaskRed; }
+
 typedef __attribute__((availability(swift, unavailable))) __attribute__((swift_name("ParentStruct.NewName"))) unsigned OldName;
 
 enum __attribute__((flag_enum,enum_extensibility(open))) : OldName {

test/Interop/Cxx/enum/anonymous-with-swift-name-module-interface.swift

@@ -60,10 +60,11 @@
 // Test rename with "swift_name" attr:
 // CHECK: struct ParentStruct
 
-// CHECK: @available(swift, obsoleted: 3, renamed: "ParentStruct.NewName")
-// CHECK: @available(*, unavailable, message: "Not available in Swift")
-// CHECK: typealias OldName = ParentStruct.NewName
+// CHECK: @available(swift, obsoleted: 3, renamed: "ParentStruct.childFn(self:)")
+// CHECK: func renameCFColorMask(_ parent: ParentStruct) -> CFColorMask
+
 // CHECK: extension ParentStruct {
+// CHECK:     func childFn() -> CFColorMask
 // CHECK:     @available(*, unavailable, message: "Not available in Swift")
 // CHECK:     typealias NewName = UInt32
 // CHECK:     struct NewName : OptionSet, @unchecked Sendable {
@@ -81,6 +82,10 @@
 // CHECK:     }
 // CHECK: }
 
+// CHECK: @available(swift, obsoleted: 3, renamed: "ParentStruct.NewName")
+// CHECK: @available(*, unavailable, message: "Not available in Swift")
+// CHECK: typealias OldName = ParentStruct.NewName
+
 // CHECK: @available(swift, obsoleted: 3, renamed: "ParentStruct.NewName")
 // CHECK: typealias OldName = ParentStruct.NewName
 // CHECK: @available(*, unavailable, message: "Not available in Swift")