private val overlay: NodeDataContainer<DNode, DElement, DProperty, DError>
) : NodeDataContainer<DNode, DElement, DProperty, DError> {
    override fun data(node: DeclarativeDocument.DocumentNode.ElementNode): DElement = when (val from = overlayOriginContainer.data(node)) {
        is FromUnderlay -> underlay.data(node)
        is FromOverlay -> overlay.data(node)
        is MergedElements -> overlay.data(from.overlayElement)
    }

            fun visit(node: DeclarativeDocument.DocumentNode, depth: Int = 0) {
                append("    ".repeat(depth))
                when (node) {
                    is DeclarativeDocument.DocumentNode.ElementNode -> {
                        appendLine(
                            "element(${node.name}" +