Why the hell this crashes in UICollectionView?

dummy.swift

let expandedSections = [0, 3, 8]
let indexSet = IndexSet(expandedSections)

		collectionView?.performBatchUpdates(
			{
				[unowned self] in
				if isInserted {
					self.collectionView?.insertItems(at: indexPaths)
				} else {
					self.collectionView?.deleteItems(at: indexPaths)
				}
				if !indexSet.isEmpty {
					self.collectionView?.reloadSections(indexSet)
				}

			}, completion: {
				_ in
			}

Crash is this:

*** Terminating app due to uncaught exception 'NSRangeException', reason: '*** 
-[NSMutableIndexSet addIndexesInRange:]: Range {9223372036854775807, 1} exceeds maximum index value of NSNotFound - 1'
*** First throw call stack:
(
	0   CoreFoundation                      0x000000011000a12b __exceptionPreprocess + 171
	1   libobjc.A.dylib                     0x000000010ed0cf41 objc_exception_throw + 48
	2   CoreFoundation                      0x000000011007f245 +[NSException raise:format:] + 197
	3   Foundation                          0x000000010bfe0309 -[NSMutableIndexSet addIndexesInRange:] + 110
	4   UIKit                               0x000000010d580613 -[UICollectionViewUpdate _computeSupplementaryUpdates] + 1820
	5   UIKit                               0x000000010d614f96 -[UICollectionView _updateWithItems:tentativelyForReordering:animator:] + 3535
	6   UIKit                               0x000000010d60f4c2 -[UICollectionView _endItemAnimationsWithInvalidationContext:tentativelyForReordering:animator:] + 17338
	7   UIKit                               0x000000010d617ac1 -[UICollectionView _endUpdatesWithInvalidationContext:tentativelyForReordering:animator:] + 71
	8   UIKit                               0x000000010d617e06 -[UICollectionView _performBatchUpdates:completion:invalidationContext:tentativelyForReordering:animator:] + 435
	9   UIKit                               0x000000010d617c30 -[UICollectionView _performBatchUpdates:completion:invalidationContext:tentativelyForReordering:] + 91
	10  UIKit                               0x000000010d617bb2 -[UICollectionView _performBatchUpdates:completion:invalidationContext:] + 74
	11  UIKit                               0x000000010d617b07 -[UICollectionView performBatchUpdates:completion:] + 53

Where did it find NSNotFound..?!

2 years later, I have the answer. Happens when you do this:

let indexPath = IndexPath(item: NSNotFound, section: section)
let attr = UICollectionViewLayoutAttributes(forSupplementaryViewOfKind: UICollectionView.elementKindSectionHeader, with: indexPath)

and somewhere along the way you do collectionView.reloadSections()

Problem is indexPath, which should be:

let indexPath = IndexPath(item: 0, section: section)

Hi I'm facing the same issue using framework for CollectionView well that is weird.
Thanks for posting the reason why it happens.
Although i did not understand fully why this is happening.
My only hint is that somehow indexSet is over-floating.