Is it possible to implement contextual extension functions in Kotlin?

Question

JVM

For example:

fun String.hello() = "world"

contextFunction {
println("".hello()) //Внутри contextFunction метод должен работать
}

println("".hello()) // А за пределами contextFunction он не должен существовать

The goal is to add methods for standard types, but only inside the dsl, so as not to pollute the global scope with these methods.

Answer 1

Of course it is possible. It is necessary to transfer a lambda with a receiver as a callback. And inside the receiver to determine the extension.

object Ctx {
    fun String.hello() = "world"
}

fun contextFunction(block: Ctx.() -> Unit) {
    Ctx.block()
}

fun main(args: Array<String>) {
    contextFunction {
        println("".hello())
    }
}

Still it is possible to rest and add functions to this context from the outside. Not quite in the usual way, but what if you want something strange.

val Ctx.hello2: String.() -> String get() = { "$this world" }

contextFunction{
   "hi".hello2()
}

Answer 2

No, It is Immpossible. And I don't understand why this is necessary.
Just make a dsl method and pass your string to it (and/or anything else)