sorry to not ask it during the meetting, but how u...

# arrow

[thanerian]

sorry to not ask it during the meetting, but how union types could interact with when expression? I asume that a fold() method will be available, but most kotlin devs are familiar with exaustive when expression, could compiler plugin support it?

[Imran/Malic]

Could you rephrase your question a bit. I don’t understand the question.
There is going to be an ide piece for Meta , which can give you an automatic exhaustive when expression on a Union Type. It’s not implemented, yet.

[thanerian]

sorry, my question is, Are Union Types compatibles with exaustive when expression in the same way as sealed classes do?

[Imran/Malic]

Of course, because their expressed as inline Classes. Loosely speaking, because you have all possible ‘cases’ of Types in a Union, deriving a when should be pretty easy. So Something like this:

val a: Union3<Int, String, Long> = TODO()

when(a){
  is Int -> doOnInt(a)
  is String -> doOnString(a)
  is Long -> doOnLong(a)
}

is possible. But don’t take that as is. This is just to showcase, how it may look like.

[thanerian]

sounds great, thanks @Imran/Malic

[Imran/Malic]

In fact a when is not even needed, because Unions can do the conversion to Null, whenever the Type you care about is not the one you expect

[raulraja]

when is needed if you don't go to null but the snippet above is how you would destructure a union

[Imran/Malic]

Your welcome @thanerian