             case .editing:
                 navigationItem.rightBarButtonItem = cancelComparisonButton
                 collectionView.allowsMultipleSelection = true
-                forEachVisibleCell { $0.setEditing(true) }
+                forEachVisibleCell { $1.setEditing(true) }
                 compareToolbarButton.isEnabled = false
                 NSLayoutConstraint.activate([
                     firstComparisonSelectionButton.widthAnchor.constraint(equalToConstant: 90),

            cell.author = item.user
            cell.sizeDiff = item.revisionSize
            cell.comment = item.parsedComment?.removingHTML
        }

        cellContentCache.setObject(CellContent(time: cell.time, displayTime: cell.displayTime, author: cell.author, authorImage: cell.authorImage, sizeDiff: cell.sizeDiff, comment: cell.comment), forKey: indexPath as NSIndexPath)

        cell.apply(theme: theme)
    }

    public class SelectionThemeModel {

            compareToolbarButton.isEnabled = collectionView.indexPathsForSelectedItems?.count ?? 0 == 2
        }

        guard let cell = collectionView.cellForItem(at: indexPath) as? PageHistoryCollectionViewCell else {
            return
        }

        let button: UIButton?
        let themeModel: SelectionThemeModel?
        if maxNumberOfRevisionsSelected {
            forEachVisibleCell { (indexPath: IndexPath, cell: PageHistoryCollectionViewCell) in
                if !cell.isSelected {
                    self.updateSelectionThemeModel(self.disabledSelectionThemeModel, for: cell, at: indexPath)
                }
                cell.enableEditing(false)
            }
        }
        switch openSelectionIndex {
