[SR-4451] type(of:) behaviour change from Swift 3.0.2 to Swift 3.1.

Previous ID	SR-4451
Radar	rdar://problem/31404284
Original Reporter	razvandub (JIRA User)
Type	Bug

Attachment: Download

Votes	0
Component/s	Compiler
Labels	Bug, StarterBug, TypeChecker
Assignee	None
Priority	Medium

md5: 59a922e46e7486ff5d399c2af0e0d2d8

Issue Description:

It seems that the behaviour of "type(of: )" has changed from Swift 3.0.2 to Swift 3.1 w.r.t. optional Any? closure parameters referenced as Any.

"type(of: oItem) as? T.Type" below returns "__NSCFString.Type" when using Swift 3.0.2 compiler and "nil" when using Swift 3.1 compiler.

import Foundation

internal extension Set where Element: NSObject {
    
    internal func items <T: NSObject> (ofType itemType: T.Type) -> Set<T>? {
        return NSSet(set: self).filtered(using: NSPredicate { (oItem: Any /* Note Any instead of Any? */, _) -> Bool in
            return nil != (type(of: oItem) as? T.Type)  // Swift 3.0.2 => true, Swift 3.1 => false.
            //                        return oItem is T // Swift 3.0.2 => true, Swift 3.1 => true.
        }) as? Set<T>
    }
}

let stringsOfTypeNSObject = (["1", "2"] as Set<NSString>).items(ofType: NSObject.self)

print(stringsOfTypeNSObject ?? []) // Swift 3.0.2 => [1, 2], Swift 3.1 => [].