DiffMoves.swift

extension OrderedCollectionDifference {
    public func inferringMoves<T: Hashable>(by f: (ChangeElement) -> T) -> OrderedCollectionDifference<ChangeElement> {
        let removeDict: [T: Int?] = {
            var res = [T: Int?](minimumCapacity: Swift.min(removals.count, insertions.count))
            for r in removals {
                let key = f(r.element)
                if res[key] != .none {
                    res[key] = .some(.none)
                } else {
                    res[key] = .some(r.offset)
                }
            }
            return res.filter { (_, v) -> Bool in v != .none }
        }()
        
        let insertDict: [T :Int?] = {
            var res = [T :Int?](minimumCapacity: Swift.min(removals.count, insertions.count))
            for i in insertions {
                let key = f(i.element)
                if res[key] != .none {
                    res[key] = .some(.none)
                } else {
                    res[key] = .some(i.offset)
                }
            }
            return res.filter { (_, v) -> Bool in v != .none }
        }()
    
        return OrderedCollectionDifference.init(validatedChanges: map({ (c: OrderedCollectionDifference<ChangeElement>.Change) -> OrderedCollectionDifference<ChangeElement>.Change in
            switch c {
            case .remove(offset: let o, element: let e, associatedWith: _):
                let key = f(e)
                if removeDict[key] == nil {
                    return c
                }
                if let assoc = insertDict[key] {
                    return .remove(offset: o, element: e, associatedWith: assoc)
                }
            case .insert(offset: let o, element: let e, associatedWith: _):
                let key = f(e)
                if insertDict[key] == nil {
                    return c
                }
                if let assoc = removeDict[key] {
                    return .insert(offset: o, element: e, associatedWith: assoc)
                }
            }
            return c
        }))
    }
}

test.swift

struct Person: Equatable {
    var uuid: String
    var name: String
    var employer: String
}

let before = [
    Person(uuid: "4628c50f-4516-4d52-ad30-28ed81b3c1b3",
        name: "Chris Lattner",
        employer: "Apple"),
    Person(uuid: "6a5ff808-91e0-4b1a-a4dc-37b30704c8a1",
        name: "Mark Zuckerberg",
        employer: "Facebook")
]

let after = [
    Person(uuid: "4628c50f-4516-4d52-ad30-28ed81b3c1b3",
        name: "Chris Lattner",
        employer: "Google"),
    Person(uuid: "2e683426-801c-4754-924c-95920fc760a5",
        name: "Bill Gates",
        employer: "Microsoft")
]

let diff = before
        .difference(from: after)
        .inferringMoves(by: { $0.uuid })