foo.swift

func ingest<T:Ingestable, U where U:Persistable, U:SwiftyMeragable, U:NSManagedObject>(ingestables: [T]?, completion: ( persistedObjects:[U] )->Void) {
}




func ingest<T where T:Ingestable, T.IngestedType:Persistable, T.IngestedType:SwiftyMeragable, T.IngestedType:NSManagedObject>(ingestables: [T]?, completion: (( persistedObjects:[NSManagedObjectID] )->Void)? = nil) {
}

internal protocol Ingestable : SwiftySerializable {
    typealias IngestedType
    func fetchRequestForUniquing() -> NSFetchRequest?
}

extension TransientUser : Ingestable {
    typealias IngestedType = PersistentUser
    
    func fetchRequestForUniquing() -> NSFetchRequest? {}
    }