ReferenceWritableKeyPath.swift

class Size { // Changed to class
    var width: Int
    let height: Int
    
    init(width: Int, height: Int) {
        self.width = width
        self.height = height
    }
}

struct Table {
    let size: Size
    let material: String
}

let tableSizeKeyPath = \Table.size.width // ReferenceWritableKeyPath<Table, Int>
let tableMaterialKeyPath = \Table.material // KeyPath<Table, String>