Multi-delegation/proxy class support

Language Design
5

You’re describing the Gang-of-Four Composite Pattern here…

It’s not really something that I’d think should be implemented at the language level for delegation, but might prove useful as a compiler plugin for an annotation (as it’s a very common pattern). Something like

@Composite(MyStuff::class)
class Container: MyStuff {
    ...
}

and the compiler plugin could generate children and myCall to make it effectively:

class Container: MyStuff {
    var children: List<MyStuff>(); // optional arg to annotation to make this private
    override fun myCall(...params...) {
        children.forEach { it.myCall(...params...); } 
    }
    ...
}

Probably useful to do for a few other Design Patterns as well