if (underlayMergeKey is MergeKey.CannotMerge || underlayMergeKey !in overlayMergeKeys) {
                underlayNodes.forEach {
                    result.add(it)
                    recordAsCopiedRecursively(it, ::FromUnderlay)
                }
                underlayNodesByMergeKey.remove(underlayMergeKey)
            }
        }