Что выведет Swift: группировка через reduce(into:)

let words = ["swift", "kotlin", "dart", "scala", "kotlin"]
let byLetter = words.reduce(into: [Character: Int]()) { acc, w in
    acc[w.first!, default: 0] += 1
}
for key in byLetter.keys.sorted() {
    print(key, byLetter[key]!)
}