Im getting the error message use of 'self' in delegating initializer before self.init is called. But why?

class Shape {
    let sides: Int
    let name: String

    init(sides: Int, name: String) {
        self.sides = sides
        self.name = name
    }
}


class Square: Shape {
    var sideLength: Double
    var area: Double {
        get {
            return sideLength * sideLength

        }
        set {
            sideLength = sqrt(newValue)
        }

    }

    init(name: String, sides: Int, sideLength: Double) {
       self.sideLength = sideLength
        super.init(sides: sides, name: name)

    }

    convenience init(sidelength: Double) {
        self.init(name: "Square", sides: 4, sideLength: sideLength) // the error comes up for this line
    }
}

let square = Square(sidelength: 20)
square.name