Kotlin star projection

SampleTest.kt

class Foo<out T : Number>(private val data: T) {

    fun get2(): T {
        return data
    }
}

class Bar<T>(private val data: T) {

    fun get2(): T {
        return data
    }
}


class SampleTest {

    @Test
    fun starProjections() {
        val a: Number = 1
        val foo = Foo(a)
        fooHandler(foo)

        val s: String = "abc"
        val bar = Bar(s)
        barHandler(bar)
    }

    // <S: Number> is mandatory. Doesn't work with just <S>
    private fun <S : Number> fooHandler(foo: Foo<S>) {
        println(foo.get2())
    }

    private fun <S> barHandler(bar: Bar<S>) {
        println(bar.get2())
    }
}