 	}
 }
 
-@available(macOS, introduced: 10.12)
+@available(macOS 10.12, *)
 extension ToolbarDelegatingOwner {
 	func assignUnclaimedToolbarItems(_ toolbar: NSToolbar, handler: ToolbarItemHandler) {
 		for item in toolbar.items where item.action == nil {

}

//this subclass allows a closure to be injected for validation
@available(macOS, introduced: 10.12)
class ValidatingToolbarItem: NSToolbarItem {
	typealias ToolbarValidationHandler = (ValidatingToolbarItem) -> Void
	var validationHandler: ToolbarValidationHandler?

	func assignUnclaimedToolbarItems(_ toolbar: NSToolbar, handler: ToolbarItemHandler)
}

@available(macOS 10.12, *)
extension ToolbarItemHandler {
	func hookupToToolbarItems(_ handler: ToolbarItemHandler, window: NSWindow) {
		//find owner
