let closedRange = Int.min...3
let partialRange = ...3

let numbers = [10, 20, 30, 40, 50, 60, 70]

print(numbers[closedRange]) // 💣💣💣 ERROR: Negative Array index is out of range

let numbers = [10, 20, 30, 40, 50, 60, 70]

print(numbers[partialRange]) // from the first index in the sequence, all the way to index: 3 
// Prints "[10, 20, 30, 40]"

protocol Registrable {
    static func register()
}

extension Registrable {
    static func register() {
        print("Registering \(Self.self)")
    }
}

class Service: Registrable {}

// Prints `Registering Service`
Service.register()

private extension HTTPClient: URLSessionDelegate {
    /// Handles server authentication challenges for Certificate Pinning.
    func urlSession(
        _ session: URLSession,
        didReceive challenge: URLAuthenticationChallenge,
        completionHandler: @escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Void
    ) {
        // We will write our pinning business logic here.
    }
}

// This struct is not sendable
struct Movie {
    let formatterCache = FormatterCache() // This is class
    let releaseDate = Date()
    var formattedReleaseDate: String {
        let formatter = formatterCache.formatter(for: "YYYY")
        return formatter.string(from: releaseDate)
    }
}

// This struct is sendable
struct Movie {
    var formattedReleaseDate = "2022"
}

func exampleFunc() async {
  let isNotSendable = MyClass()

  // Value of non-Sendable type ... accessed after being transferred; 
  // later accesses could race
  Task {
    isNotSendable.count += 1
  }

  // Access can happen concurrently
  print(isNotSendable.count)
}

struct SingleUseTicket: ~Copyable {
    let ticketID: Int
    
    consuming func invalidate() {
        print("Ticket \(ticketID) invalidated.")
        
        // cleanup logic
        
        discard self
    }
    
    deinit {
        print("Ticket deinitialized.")
        
        // cleanup logic
    }
}

func testFibonacciSequenceThrowsError() async throws {
    do {
        let _ = try await fibonacciSequence(count: -1)
        XCTFail("Expected an error for negative count, but no error was thrown")
    } catch FibonacciError.invalidCount {
        // Success! The expected error was thrown.
    } catch {
        XCTFail("Unexpected error thrown: \(error)")
    }
}