[Pitch] Adding a Self type name shortcut for static member access

Evolution Pitches
40

Having read SE-0088 and skimmed through this discussion, it's not clear to me that this Self would support what I'm really hoping for, which is the ability to define a method on a base class (or an extension of a base class) that can return an instance of a derived class and take advantage of Swift’s type inference in the process (example here):

extension
NSManagedObject
{
    class func
    all(inMOC: NSManagedObjectContext,
            predicateFormat inPredicateFormat: String,
            _ inArgs: CVarArg...)
        throws
        -> [Self]
    {
        let entity = self.entity(inMOC: inMOC)
        let req = NSFetchRequest<Self>()
        req.entity = entity
        
        let pred = NSPredicate(format: inPredicateFormat, argumentArray: inArgs)
        req.predicate = pred
        
        return try inMOC.fetch(req) as [Self]
    }
}

class MyEntity : NSManagedObject {}

let myEntities = MyEntity.all(inMOC: moc, predicateFormat: : "foo == %d", someInt)
// myEntities is inferred to be of type [MyEntity]

In this use, Self is the static type of the derived usage.