Error: instance method 'METHOD' requires that 'CLASS' conform to 'PROTOCOL'

Using Swift
, ,
1

Hi,
Im seeing the below error when I try to compile my code. I couldn't figure out the underlying issue here. Can someone please help me understand what's going on and how to fix this.

error: instance method 'snapshot(state:card:size:)' requires that 'UICollectionViewCell' conform to 'CardViewProtocol'

Code that produces the above error.

// UI Model
struct WelcomeCardUIModel { }

// Protocols
protocol CardViewProtocol {
    associatedtype State
    
    func render(state: State)
}

protocol CardDimensionCalculable {
    associatedtype CardModel

    static func cardDimension(for traitCollection: UITraitCollection, bounds: CGRect, model: CardModel?) -> CGSize
}

// Protocols Usage
class WelcomeCard: UICollectionViewCell { }

extension WelcomeCard: CardViewProtocol {
    func render(state: WelcomeCardUIModel) { }
}

extension WelcomeCard: CardDimensionCalculable {
    static func cardDimension(for traitCollection: UITraitCollection, bounds: CGRect = .zero, model: WelcomeCardUIModel? = nil) -> CGSize {
        return CGSize.zero
    }
}

// Error class
class CardSnapshotTests {
    func testWelcomeCardWithModel() {
        /**
         error: instance method 'snapshot(state:card:size:)' requires that 'UICollectionViewCell'
         conform to 'CardViewProtocol' snapshot(state: WelcomeCardUIModel(), card: WelcomeCard.self)
         */
        snapshot(state: WelcomeCardUIModel(), card: WelcomeCard.self) {
            return WelcomeCard.cardDimension(for: $0, width: UIScreen.main.bounds.width)
        }
    }
    
    private func snapshot<Card: UICollectionViewCell & CardViewProtocol>(state: Card.State, card: Card.Type, size: (UITraitCollection) -> CGSize) {
        /* Code */
    }
}
3

Actually i found the reason, it is a silly mistake made by me.

The below line,

snapshot(state: WelcomeCardUIModel(), card: WelcomeCard.self) {
    return WelcomeCard.cardDimension(for: $0, width: UIScreen.main.bounds.width)
}

supposed to be,

snapshot(state: WelcomeCardUIModel(), card: WelcomeCard.self) {
    return WelcomeCard.cardDimension(for: $0, bounds: UIScreen.main.bounds)
}

Xcode didn't throw error on the exact line where the error was.