Issue Description:

When I like to conform MyViewController to MyProtocol as follows. It causes error "Type 'MyViewController' does not conform to protocol 'MyProtocol'" in Swift 5

// code1.swift
class MyView: UIView {}

protocol MyProtocol: AnyObject {
  var myView: MyView { get }
}

// Type 'MyViewController' does not conform to protocol 'MyProtocol'
class MyViewController: UIViewController, MyProtocol {
  @IBOutlet var myView: MyView!
}

Of course, I have an option to write like this

// code2.swift
 class MyViewController: UIViewController, MyProtocol {
  @IBOutlet var _myView: MyView! 
  var myView: MyView { _myView }
}

Or, I can make its accessor to be implicitly unwrapped optionals as this.

// code3.swift
class MyView: UIView {}

protocol MyProtocol: AnyObject { 
  var myView: MyView! { get }
}

class MyViewController: UIViewController, MyProtocol {
  @IBOutlet var myView: MyView!
}

If the protocol is written by ourself, we can rewrite as code3, however, if the protocol is provided by third party, then I have take other way such as code2.

I have a feature request that return value of implicitly unwrapped optional value to be treated as none optional value (code1). Or, if swift team come up with better way to solve this problem, then I would be happy.

Thanks,