retry() code block in Swift

Retry.swift

/// Retry a block of code until it succeeds, maximum n times
///
/// Usage:
/// ```
/// var failTimes = 3
/// try retry(5) {
///     if failTimes > 0 {
///         failTimes -= 1
///         throw MyError()
///     }
///     print("Success!")
/// }
/// struct MyError: Error {}
/// ```
func retry<R>(_ count: Int, block: () throws -> R) rethrows -> R {
    var attempt = 0
    while true {
        do { return try block() }
        catch {
            if attempt == count { throw error }
            attempt += 1
        }
    }
}