Comment by bern4444 | Hacker News Reader

Comment by bern4444 | Hacker News Reader

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That's an interesting counter point, though another comment in a different post for this same article[1] pointed out that Dart is considering adding pattern matching too.

Though I have trouble understanding how a nominal type system affects this? Does dart not have generics? That's all you need to support these patterns? I'm having trouble understanding how the type of type system plays a role here.

Also, what's 'imperative destructing'? Haven't heard that term before, is that just pulling out a property from an object like this from JS?

    const { foo } = objectWithPropertyFoo;

[1]https://news.ycombinator.com/item?id=25334283

Yes Dart has generics which is how you would implement optional types yourself. The type of type system doesn't play a role here you are right. I was thinking of the really good pattern matching I have experienced usually being present with structural subtyping.

Dart is considering adding pattern matching (and real tuples!) and I think they will eventually get there. I just think that would have had to come first to make the case of optionals over nullable types more compelling.

I would call that example destructing in the normal sense and it is basically a form of pattern matching. To do that in an imperative language without pattern matching (i.e. what I am calling imperative destructuring), you end up with code like

  if (maybeFoo.isSome) {
    final foo = maybeFoo.asValue;
    ...
  }

when you really want

  if let Some(foo) = maybeFoo {...}

You may prefer

    for foo in maybeFoo { ... }

This (AIUI) isn't valid Dart code though, but this would be:

    maybeFoo.forEach((foo) { ... })

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