Kotlin Reflection and Variance

[debussyman]

I’m trying to understand how variance works with reflection. As an example I’ve come across a seeming inconsistency in how variance is enforced. See this code -

>>> import kotlin.reflect.full.*
>>> data class One(val id: String)
>>> val data = One("Two")
>>> data.javaClass.kotlin.declaredMemberProperties.first().invoke(data)
Two
>>> data::class.declaredMemberProperties.first().invoke(data)
error: out-projected type 'KProperty1<out Line_28.One, Any?>' prohibits the use of 'public abstract fun invoke(p1: T): R defined in kotlin.reflect.KProperty1'
data::class.declaredMemberProperties.first().invoke(data)

What is happening here?

[Wasabi375]

This was already discussed here:

Type projection clash when accessing property delegate instance

My task is to search given class for delegated properties and access information stored in delegate instances. I can access the list of all properties via reflection and then check each one for its type. The problem is that code like this: target::class.memberProperties.forEach { val delegate = it.getDelegate(target) } throws an exception since memberProperties produces out projection and then getDelegate can’t consume initial target. Of course, I can manually cast …

[debussyman]

@Wasabi375 Thanks very much for the reply and link reference! However my question still lingers, why does the invocation through .javaClass work, is there some kind of “variance erasure” happening?