> * I would like to see more work on `RecoverableError`. I know this is a more
> or less faithful translation of `NSErrorRecoveryAttempting`, but I don't
> think that's a particularly good API, and I would like to see it revisited.
>
> The design I'd prefer would look more like this:
>
> protocol RecoverableError: Error {
> var recoveryOptions: [ErrorRecoveryOption] { get }
> }
>
> typealias ErrorRecoveryCompletionHandler = (recovered: Bool) ->Void
>
> protocol ErrorRecoveryOption {
> var localizedName: String { get }
> func attemptRecovery(completion: ErrorRecoveryCompletionHandler) {…}
> }
>
> struct AnyErrorRecoveryOption: ErrorRecoveryOption {
> typealias RecoveryAttempter = (ErrorRecoveryCompletionHandler) ->Void
>
> var localizedName: String
> var attempter: RecoveryAttempter
>
> init(localizedName: String, attempter: RecoveryAttempter) {…}
>
> func attemptRecovery(completion: CompletionHandler) { attempter(completion) }
> }
>
> Though further from the equivalent Foundation API, I think this is a much
> cleaner design. It requires no `switch` statements, avoids issues with
> matching indices between the option array and the recovery attempter, and
> makes it easier for interested subtypes to add or remove recovery options.
>
> In particular, in my view, there should be only one way to attempt recovery,
> and that way should not be application-modal. If a client wants to recover
> modally, we should invoke the non-modal API and then spin the runloop until
> the completion handler runs.
>
> If a better `RecoverableError` design isn't feasible in Swift 3, I think we
> can defer it. In a pinch, `CustomNSError` provides the ability to specify
> error-handling behavior the old-fashioned way.
I agree. This feels like a much better API, specially as it’s not tied to Cocoa
(e.g. via `CustomNSError `). One tweak I would suggest is for the completion
handler to return an error:
```
typealias ErrorRecoveryCompletionHandler = (recoveryError: Error?) ->Void
```
If the recovery from an error fails, It’s almost certainly because *another*
error occurred.
I realise this is an even larger departure from Cocoa, but it should not be
difficult to do technically. A negative result returned by, say,
`NSErrorRecoveryAttempting` can will be converted to a new `RecoveryFailed`
error struct which wraps the original error; conversely, a “recovered” boolean
can be created by simply checking if the recovery error is `nil`.
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