TypedIdentifier.swift

struct TypedIdentifier<T>: Equatable, Codable, ExpressibleByIntegerLiteral, CustomStringConvertible, RawRepresentable {
    let rawValue: Int
    var description: String {
        return "\(rawValue)"
    }
    
    init?(rawValue: Int) {
        self.rawValue = rawValue
    }
    init(integerLiteral value: Int) {
        self.rawValue = value
    }
}

protocol Identifiable {
    typealias Identifier = TypedIdentifier<Self>
    var id: Identifier { get }
}

struct Post: Equatable, Codable, Identifiable {
    let id: Identifier
    let title: String
    let body: String
}

struct Hotel: Equatable, Codable, Identifiable {
    let id: Identifier
    let name: String
    let description: String
}

func orderRoomInHotel(withId id: TypedIdentifier<Hotel>) { }

let somePost = Post(id: 1, title: "Title", body: "Body")
print(somePost) 
// Post(id: 1, title: "Title", body: "Body")

let encoder = JSONEncoder()
encoder.outputFormatting = .prettyPrinted
let jsonData = try! encoder.encode(somePost)
print(String(data: jsonData, encoding: .utf8)!)
/*
{
  "id" : 1,
  "title" : "Title",
  "body" : "Body"
}
*/
orderRoomInHotel(withId: somePost.id)
// Error: Cannot convert value of type 'Post.Identifier' (aka 'TypedIdentifier<Post>') to expected argument type 'TypedIdentifier<Hotel>'