Android Compose Generics Objects and Extensions

[wym3316]

Name of the Codelab or Codelab URL
https://developer.android.com/codelabs/basic-android-kotlin-compose-generics?hl=ja&continue=https%3A%2F%2Fdeveloper.android.com%2Fcourses%2Fpathways%2Fandroid-basics-compose-unit-3-pathway-1%3Fhl%3Dja%26_gl%3D1*m31xei*_up*MQ..*_ga*MTIwMjg2MzcwOC4xNzM0OTQyMTEy*_ga_6HH9YJMN9M*MTczNDk2MjQ4Ny4yLjAuMTczNDk2MjQ4Ny4wLjAuMTAwNjEwNDE1NA..%23codelab-https%3A%2F%2Fdeveloper.android.com%2Fcodelabs%2Fbasic-android-kotlin-compose-generics&_gl=1*1powsb*_up*MQ..*_ga*MTIwMjg2MzcwOC4xNzM0OTQyMTEy*_ga_6HH9YJMN9M*MTczNDk2MjQ4Ny4yLjAuMTczNDk2MjQ4Ny4wLjAuMTAwNjEwNDE1NA..#5

Describe the problem
Wrong code
fun main() {
println(Quiz.progressText)
}

Correct code
fun main() {
println(Quiz.StudentProgress.progressText)
}

In which lesson and step of the codelab can this issue be found?
[6. 新しいプロパティとメソッドでクラスを拡張する]
3

I mean 6-3

How to reproduce?
data class Question(
val questionText: String,
val answer: T,
val difficulty: Difficulty
)

enum class Difficulty {
EASY, MEDIUM, HARD
}

class Quiz {
val question1 = Question("Quoth the raven ___", "nevermore", Difficulty.MEDIUM)
val question2 = Question("The sky is green. True or false", false, Difficulty.EASY)
val question3 = Question("How many days are there between full moons?", 28, Difficulty.HARD)

object StudentProgress {
var total: Int = 10
var answered: Int = 3
}

}

val Quiz.StudentProgress.progressText: String
get() = "${answered} of ${total} answered"

fun main() {
// below is incorrect
println(Quiz.progressText)

// correct code is below
println(Quiz.StudentProgress.progressText)

}

Versions
Kotlin Playground

Additional information

codelab: basic-android-compose-training-add-scrollable-list