[SR-3168] Missing fix-it for "'optional' can only be applied to protocol members"

[belkadan]

Previous ID	SR-3168
Radar	rdar://problem/25583673
Original Reporter	@belkadan
Type	Improvement
Status	Resolved
Resolution	Done

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Improvement, DiagnosticsQoI, StarterBug
Assignee	@belkadan
Priority	Medium

md5: 3712ee5c89fa28d178516e90e2ba9a8f

Issue Description:

import UIKit

class C: NSObject, UICollectionViewDelegate {
    optional internal func indexPathForPreferredFocusedView(in collectionView: UICollectionView) -> IndexPath? {
        return nil
    }
}

<stdin>:5:5: error: 'optional' can only be applied to protocol members
    optional internal func indexPathForPreferredFocusedView(in collectionView: UICollectionView) -> IndexPath? {
    ^

There should be a fix-it to remove the "optional".

[robinkunde]

Pull request: #5717