test.kt

package bug

import java.lang.reflect.ParameterizedType

abstract class Bar<T> {
    val type: java.lang.reflect.Type

    init {
        val superClass = javaClass.genericSuperclass
        type = (superClass as ParameterizedType).actualTypeArguments[0]
    }
}

inline fun <reified T> wtf() =
    object : Bar<T>() {}

inline fun <reified E> doesntWork() =
    wtf<List<E>>().type

inline fun <reified E> works() =
    (object : Bar<List<E>>() {}).type

fun main() {
    println(doesntWork<String>().typeName)
    println(works<String>().typeName)
}