bedobi

    fun doSomething(user: User) { if (user is Student) { do this } else { do that } }

    data class User (id: Int, name: String, email: String)

    data class Student (userId: Id, blabla student specific attributes)

    data class Employee (userId: Id, blabla employee specific attributes)

    The current state of software safety discussion resembles the state of medical safety discussion 2, 3 decades ago (yeah, software is really really behind time).

    Back then, too, the thoughts on medical safety also were divided into 2 schools: the professionalism and the process oriented. The former school argues more or less what Uncle Bob argues: blame the damned and * who made the mistakes; be more careful, damn it.

    But of course, that stupidity fell out of favor. After all, when mistakes kill, people are serious about it. After a while, serious people realize that blaming and clamoring for care backfires big time. That's when they applied, you know, science and statistic to safety.

    So, tools are upgraded: better color coded medicine boxes, for example, or checklists in surgery. But it's more. They figured out what trainings and processes provide high impacts and do them rigorously. Nurses are taught (I am not kidding you) how to question doctors when weird things happen; identity verification (ever notice why nurses ask your birthday like a thousand times a day?) got extremely serious; etc.

    My take: give it a few more years, and software, too, probably will follow the same path. We needs more data, though.

    Either<Error, Foo>

    return fooService
                .getFoo(
                    fooId
                ) //Either<Error, Foo>
                .fold({ //left (error) case
                    when (it) {
                        is GetFooErrors.NotAuthenticated -> { Response.status(401).build() }
                        is GetFooErrors.InalidFooId -> { Response.status(400).build() }
                        is GetFooErrors.Other -> { Response.status(500).build() }
                    }
                }, { //right case
                   Response.ok(it)
                })