[Proposal] 'selfprivate' Access Control - allowing access in extension within '`self`'

Evolution Pitches
6

This has also been discussed here

In short, I don't think it's a good idea. Among other things, it would allow to work around privateness in extensions, by adding members that refer to the internal selfprivate member:

extension ClientSecurityStuff {
  var isAvailableWorkaround: Bool {
    get { self.isAvailable }
    set { self.isAvailable = newValue }
  }
}