Writing a Kotlin util function which provides self-reference in initializer

Question

I\'m trying to generalize my hack from an answer to another question.

It should provide a way to reference a value which is not constructed yet inside its initializ

Answer 1

The best I have managed to produce while still being completely generic is this:

class SelfReference(val initializer: SelfReference.() -> T)  {
    val self: T by lazy {
        inner ?: throw IllegalStateException("Do not use `self` until initialized.")
    }

    private val inner = initializer()
    operator fun invoke(): T = self
}

Adding the invoke operator lets you use it in the following way:

val h: Holder = selfReference { Holder(0) { this().x++ } }

This is the closest I got to make it look like something you would "normally" write.

Sadly I think it is not possible to get completely rid of a explicit access to the element. Since to do that you would need a lambda parameter of type T.() -> T but then you wouldn't be able to call that parameter without an instance of Tand being T a generic there is no clean and safe way to acquire this instance.

But maybe I'm wrong and this helps you think of a solution to the problem