fun main() {
    val sb = StringBuilder()
    // sb becomes this within the lambda scope
    val string = with(sb) /* Is an extention function on type T */ {
        appendLine("Something")
        append('a')
        toString()
    }

    val buildString = buildString {
        append(1)
        append(2)
        toString()
    }

    val words = Words()
    with(words) {
        // The following two lines should compile:
        "one".record()
        +"two"
    }
    words.toString() == "[one, two]"
}

class Words {
    private val list = mutableListOf<String>()

    fun String.record() = list.add(this)

    operator fun String.unaryPlus() = list.add(this)

    override fun toString() = list.toString()
}