extension Swift.Error { func `throw`<T>() throws -> T { throw self } } extension Optional { func `else`<T: Swift.Error>(_ error: @autoclosure () -> T) throws -> Optional { guard case .some = self else { throw error() } return self } func unwrap<T: Swift.Error>(or error: @autoclosure () -> T) throws -> Wrapped { guard case let .some(wrapped) = self else { throw error() } return wrapped } enum Error: Swift.Error { case isNone(String) } func `else`(_ message: @autoclosure () -> String) throws -> Optional { guard case .some = self else { throw Error.isNone(message()) } return self } func unwrap(or message: @autoclosure () -> String) throws -> Wrapped { guard case let .some(wrapped) = self else { throw Error.isNone(message()) } return wrapped } } enum Error: Swift.Error { case unavailable, notInt } let dictionary: [AnyHashable: Any] = ["available": 1] do { let a = try (dictionary["available"] ?? Error.unavailable.throw()) as? Int ?? Error.notInt.throw() let b = try dictionary["available"].unwrap(or: Error.unavailable) as? Int ?? Error.notInt.throw() let c = try dictionary["available"].map({ try ($0 as? Int).unwrap(or: Error.notInt) }).unwrap(or: Error.unavailable) let d = try dictionary["available"].map({ try $0 as? Int ?? Error.notInt.throw() }) ?? Error.unavailable.throw() let e = try dictionary["available"].else(Error.unavailable).map({ $0 as? Int }).unwrap(or: Error.notInt) let f = try dictionary["available"].else("\"available\" does not exists").map({ $0 as? Int}).unwrap(or: "Fail converting to Int") } catch { print(error) }