Testing the claims from the bug report in the REPL in Xcode 11.5

// > swift
Welcome to Apple Swift version 5.2.4 (swiftlang-1103.0.32.9 clang-1103.0.32.53).
Type :help for assistance.
  1> import Foundation
  2> Optional<IndexPath>.none == nil
$R0: Bool = true
  3> let indexPath: IndexPath? = nil
indexPath: IndexPath? = nil
  4> dump(indexPath)
- nil
$R1: IndexPath? = nil

While the above doesn't seem to correspond to the behavior reported, perhaps what you are seeing is the LLDB bug SR-11593, where the debugger incorrectly displays nil for some Optionals? (see screenshot in SR-11546 for example)

Comment by Jason Sadler (JIRA)

Thanks for looking into this! I think a few things must be at play here.

1. I used the REPL and I'm seeing what you're seeing, so no bug there.

2. Using po in LLDB to find the value of the variable does sound exactly like SR-11593.

3. However, in my project, I am still getting incorrect behaviour with a conditional when running on the iPad simulator:

let selectedProjectIsInList = listViewController.selectedObject.map { dataSource.indexPath(for: $0) } != Optional<IndexPath>.none
if !selectedProjectIsInList {
    listViewController.selectObject(nil)
    router.emptyRightPane()
}

where selectedObject is an optional, and indexPath(for🙂 returns IndexPath?. If I use nil instead of Optional<IndexPath>.none above, the code within the if block is never run. Switching it to use Optional<IndexPath>.none causes it to behave as expected. indexPath(for🙂 is a thin wrapper around an NSFetchedResultsController:

func indexPath(for object: T) -> IndexPath? {
    return fetchedResultsController.indexPath(forObject: object)
}

The Optional map function looks like this:

func map<U>(_ transform: (Wrapped) throws -> U) rethrows -> U?

It means that in your case it will return IndexPath?? i.e. Optional<Optional<IndexPath>>.

You have 3 potential returns for your expression

1. selectedObject is nil returns

   Optional<Optional<IndexPath>>.none
   

2. selectedObject is not nil and
   2.1 has no indexPath returns

   Optional<Optional<IndexPath>>.some(Optional<IndexPath>.none)
   

   2.2 has indexPath returns

   Optional<Optional<IndexPath>>.some(Optional<IndexPath>.some(IndexPath))
   

   If you compare these returns for equality to nil, you'll see that it's only true for (1), but if you instead compare with Optional<IndexPath>.none it's only true for (2.1).

To fix your problem you probably want to replace map with flatMap to get an expression that returns IndexPath?.

Comment by Jason Sadler (JIRA)

�‍♂️ yes. I can’t believe I missed that. Thanks so much!
I suppose this can be resolved as a dupe of the issue you mentioned in your first comment.