Add async/await/actor test samples

Snapshots/Async/Actors.swift

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+actor SafeCollector {
+    var deck: Set<String>
+
+    init(deck: Set<String>) {
+        self.deck = deck
+    }
+
+    func send(card selected: String, to person: SafeCollector) async -> Bool {
+        guard deck.contains(selected) else { return false }
+
+        deck.remove(selected)
+        await person.transfer(card: selected)
+        return true
+    }
+
+    func transfer(card: String) {
+        deck.insert(card)
+    }
+}
+
+class NewDataController {
+    @MainActor func save() {
+        print("Saving data…")
+    }
+}

Snapshots/Async/AsyncAwait.swift

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+func processWeather() async {
+    let records = await fetchWeatherHistory()
+    let average = await calculateAverageTemperature(for: records)
+    let response = await upload(result: average)
+    print("Server response: \(response)")
+}
+
+enum UserError: Error {
+    case invalidCount, dataTooLong
+}
+
+func fetchUsers(count: Int) async throws -> [String] {
+    if count > 3 {
+        // Don't attempt to fetch too many users
+        throw UserError.invalidCount
+    }
+
+    // Complex networking code here; we'll just send back up to `count` users
+    return Array(["Antoni", "Karamo", "Tan"].prefix(count))
+}
+
+func save(users: [String]) async throws -> String {
+    let savedUsers = users.joined(separator: ",")
+
+    if savedUsers.count > 32 {
+        throw UserError.dataTooLong
+    } else {
+        // Actual saving code would go here
+        return "Saved \(savedUsers)!"
+    }
+}
+
+func updateUsers() async {
+    do {
+        let users = try await fetchUsers(count: 3)
+        let result = try await save(users: users)
+        print(result)
+    } catch {
+        print("Oops!")
+    }
+}

Snapshots/Async/AsyncLet.swift

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+func printUserDetails() async {
+    async let username = getUser()
+    async let scores = getHighScores()
+    async let friends = getFriends()
+
+    let user = await UserData(name: username, friends: friends, highScores: scores)
+    print("Hello, my name is \(user.name), and I have \(user.friends.count) friends!")
+}
+
+enum NumberError: Error {
+    case outOfRange
+}
+
+func fibonacci(of number: Int) async throws -> Int {
+    if number < 0 || number > 22 {
+        throw NumberError.outOfRange
+    }
+
+    if number < 2 { return number }
+    async let first = fibonacci(of: number - 2)
+    async let second = fibonacci(of: number - 1)
+    return try await first + second
+}

Snapshots/Async/AsyncSequences.swift

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+func printAllDoubles() async {
+    for await number in DoubleGenerator() {
+        print(number)
+    }
+}
+
+func containsExactNumber() async {
+    let doubles = DoubleGenerator()
+    let match = await doubles.contains(16_777_216)
+    print(match)
+}

Snapshots/Async/EffectfulProperties.swift

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+var contents: String {
+    get async throws {
+        guard let url = Bundle.main.url(forResource: filename, withExtension: nil) else {
+            throw FileError.missing
+        }
+
+        do {
+            return try String(contentsOf: url)
+        } catch {
+            throw FileError.unreadable
+        }
+    }
+}

Snapshots/Async/PropertyWrappers.swift

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+func setScore2(@Clamped(range: 0 ... 100) to score: Int) {
+    print("Setting score to \(score)")
+}

Snapshots/Async/README.md

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+Async/await test samples from https://www.hackingwithswift.com/articles/233/whats-new-in-swift-5-5

Snapshots/Async/Sendable.swift

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+func runLater(_ function: @escaping @Sendable () -> Void) {
+    DispatchQueue.global().asyncAfter(deadline: .now() + 3, execute: function)
+}