Cannot use auto closure init in a closure about result HOT 5 CLOSED

func simpleFunc() {
    let result: Result<String, NSError> = Result(try tryIsSuccess("success"))
}

// simpleBlock is inferred as `() throws -> Void`.
let simpleBlock = {
    let result: Result<String, NSError> = Result(try tryIsSuccess("success"))
}

        asset.loadValuesAsynchronouslyForKeys(keys) {[weak asset, weak self] in
            let result = Result{ [weak asset] in
                guard let asset = asset else { throw Break.Unknown }
                for key in keys {
                    var error: NSError?
                    switch asset.statusOfValueForKey(key, error: &error) {
                    case .Failed   : throw Break.Error(error!)
                    case .Cancelled: return nil // return nil means no result, because the cancel result has been handled elsewhere
                    case .Loaded   : continue
                    default        : throw Break.Unknown
                    }
                }
                return asset.playable && !asset.hasProtectedContent
            }

            if let result = result {
                self?.outputHandler(result)
            }
        }

extension Result{
    public init?(_ f: () throws -> T?) {
        do {
            guard let result = try f() else { return nil }
            self = .Success(result)
        } catch {
            self = .Failure(error as! Error)
        }    
    }
}