declaring
abstract fun declaring(component: Component, node: SwingModifier.Node<*>, element: SwingModifier.NodeElement<*, *>, write: () -> Unit)
Runs write - what one element writes onto component for the slot node holds, whether that is the slot's first write or a later one.
node identifies the slot for as long as it holds one, which the element does not: a pass hands the slot a fresh element carrying the same declaration. element is that declaration, and is what a report about the write names it by.