Merge pull request swiftlang#32676 from lorentey/simplify-checkclass

[Foundation] Update & simplify class name stability check

Author: lorentey

include/swift/Runtime/FoundationSupport.h

@@ -0,0 +1,40 @@
+//===--- FoundationSupport.cpp - Support functions for Foundation ---------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2020 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+//
+// Helper functions for the Foundation framework.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SWIFT_RUNTIME_FOUNDATION_SUPPORT_H
+#define SWIFT_RUNTIME_FOUNDATION_SUPPORT_H
+
+#include "swift/Runtime/Config.h"
+
+#if SWIFT_OBJC_INTEROP
+#include <objc/runtime.h>
+
+#ifdef __cplusplus
+namespace swift { extern "C" {
+#endif
+
+/// Returns a boolean indicating whether the Objective-C name of a class type is
+/// stable across executions, i.e., if the class name is safe to serialize. (The
+/// names of private and local types are unstable.)
+SWIFT_RUNTIME_STDLIB_SPI
+bool _swift_isObjCTypeNameSerializable(Class theClass);
+
+#ifdef __cplusplus
+}} // extern "C", namespace swift
+#endif
+
+#endif // SWIFT_OBJC_INTEROP
+#endif // SWIFT_RUNTIME_FOUNDATION_SUPPORT_H

stdlib/public/Darwin/Foundation/CMakeLists.txt

@@ -7,7 +7,7 @@ add_swift_target_library(swiftFoundation ${SWIFT_SDK_OVERLAY_LIBRARY_BUILD_TYPES
   BundleLookup.mm
   Calendar.swift
   CharacterSet.swift
-  CheckClass.mm
+  CheckClass.swift
   Codable.swift
   Collections+DataProtocol.swift
   CombineTypealiases.swift