[kitd]

This interface has now been set in stone. Any additions that would be useful for the widget interface, say OnClick(), will require a breaking change.

The idiomatic way to deal with this is to add a new interface with the extensions. This not only prevents old code from breaking but also gives you compile-time assurance that your clients and objects know how to communicate with each other.

[lelanthran]

>> This interface has now been set in stone. Any additions that would be useful for the widget interface, say OnClick(), will require a breaking change.

> The idiomatic way to deal with this is to add a new interface with the extensions.

I also found that particular criticism weird in the GP, considering that the paper itself, with the widget example cited by the GP, performs the `extend` on an interface to add to existing interfaces without breaking existing code.

IOW, it uses the widget example, quoted by GP, to demonstrate how to add to an interface without breaking changes.