ValidatableInterfaceElement conformance to AnyObject

[Steveybrown]

When trying set properties of ValidatableInterfaceElement in a subclass of UITextfield I am getting Cannot assign to property: 'self' is immutable swift error.

To resolve this I had to restrict ValidatableInterfaceElement to AnyObject. Is there a known workaround for this?

I'm happy to submit a PR if supported ?

Side note:
https://stackoverflow.com/questions/52727345/cannot-assign-to-property-self-is-immutable-swift-error

Thanks,