I am puzzled by a deluge of warnings like:

This code path does I/O on the main thread underneath that can lead to UI responsiveness issues. Consider ways to optimize this code path

on code that seems perfectly inocuous, like:

class FileOrFolderCell: UICollectionViewCell {
    @IBOutlet weak var newBadge: UILabel!
    //...
    let emojiLabelInitialFontSize: CGFloat = 64 // <-- flagged as potential hang risk
    //...
    var isNew = false { // <-- potential hang risk
        didSet {
            newBadge.isHidden = !isNew
        }
    }
//...
}

There is no I/O that I can see in my code. What are those warnings all about? Can anybody offer any insights on how to address this?