fold-or-what.kt

    var leftPsi: PsiElement? = clone.firstPsi
    val result = generateSequence (clone.firstPsi) { it.findNextSibling(end) }
            .filter { ! it.haveSibling(end) }
            .map {
                val result = leftPsi!! to it
                leftPsi = it.findNextSibling(end)
                result
            }