Property wrapper of keychain store

KeychainStorage.swift

import Foundation
import KeychainAccess

//https://www.swiftbysundell.com/articles/property-wrappers-in-swift/
public protocol AnyOptional {
    var isNil: Bool { get }
}

extension Optional: AnyOptional {
    public var isNil: Bool { self == nil }
}

@propertyWrapper
public struct KeychainStorage<T> where T: KeychainStorgaeDataAcceptable {
    let key: String
    let defaultValue: T
    let keychain: Keychain

    init(_ key: String, keychain: Keychain, defaultValue: T) {
        self.key = key
        self.defaultValue = defaultValue
        self.keychain = keychain
    }

    public var wrappedValue: T {
        get {
            if let value = keychain[key] as? T {
                return value
            } else {
                return defaultValue
            }
        }
        set {
            if let value = newValue as? AnyOptional, value.isNil {
                keychain[key] = nil
            } else {
                if let value = newValue as? Data {
                    keychain[data: key] = value
                } else if let value = newValue as? String {
                    keychain[string: key] = value
                } else {
                    assertionFailure("Keychain should never store data other then String or Data type")
                }
            }
        }
    }
}

// see more: https://swiftbysundell.com/articles/property-wrappers-in-swift/
extension KeychainStorage where T: ExpressibleByNilLiteral {
    init(_ key: String, keychain: Keychain) {
        self.key = key
        self.defaultValue = nil
        self.keychain = keychain
    }
}

public protocol KeychainStorgaeDataAcceptable {}
extension String: KeychainStorgaeDataAcceptable {}
extension Data: KeychainStorgaeDataAcceptable {}
extension Optional: KeychainStorgaeDataAcceptable where Wrapped: KeychainStorgaeDataAcceptable {}