Open Radar

 
Area:
Foundation

Summary:
Calling Calendar.enumerateDates(startingAfter:, matching:, matchingPolicy:, using:) with certain start dates will hang execution with what looks like an internal infinite loop at year boundaries.

Steps to Reproduce:
Call the mentioned API with certain parameters, see attached playground.

import Foundation

let cal = Calendar(identifier: .gregorian)
let comps = DateComponents(day: 1)
let startDate = ISO8601DateFormatter().date(from: "2017-08-20T00:00:00Z")!

cal.enumerateDates(startingAfter: startDate, matching: comps, matchingPolicy: .nextTime) { (date, _, _) in
    print(date!)
}

Expected Results:
print out of every start of the month after the start date

Observed Results:
four values being printed, then the program execution hangs

2017-08-31 22:00:00 +0000
2017-09-30 22:00:00 +0000
2017-10-31 23:00:00 +0000
2017-11-30 23:00:00 +0000

my local timezone being Europe/Berlin (which does not seem to influence the results, though)

Version:
iOS 11 beta from Xcode Version 9.0 beta 6 (9M214v) 
also seen live on device with iOS 11 beta 7

Attachment: Playground with same code as above