Kotlin - Restrict extension method scope

Question

Is there a way to restrict extension methods in DSLs?

Say I have a class structure like this:

class Outer {
    fun middle(op: Middle.() -> Unit):         


        

Answer 1

The official way to restrict scope is DslMarker. It cannot help in some cases (when you need to annotate java sources, for example) - and here @Deprecated is used. But try DslMarker first.

@DslMarker
@Target(AnnotationTarget.CLASS, AnnotationTarget.TYPE)
annotation class Scope

@Scope
class Outer {
    fun middle(op: Middle.() -> Unit): Middle { /**/ }
}

@Scope
class Middle {
    fun inner(op: Inner.() -> Unit): Inner {/**/ }
}

class Inner

Thus the last middle call is not compilable anymore.