test/SourceKit/InterfaceGen/Inputs/Foo.swift - third_party/swift - Git at Google

 @_exported import Foo

 public class FooOverlayClassBase {
   public func f() {}
 }
 public class FooOverlayClassDerived : FooOverlayClassBase {
   override public func f() {}
 }

 class InternalClassShouldShow {}
	@_exported import Foo

	public class FooOverlayClassBase {
	public func f() {}
	}
	public class FooOverlayClassDerived : FooOverlayClassBase {
	override public func f() {}
	}

	class InternalClassShouldShow {}