Hi everyone! I want to initialize a `Boolean` vari...

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[Alejo]

Hi everyone!
I want to initialize a Boolean variable from another one of type Boolean? and if the value is null then I will want to check if a value is present in another list and use that value for the initialization. Here is the code:

val statuses = listOf("pending", "on-hold", "auto-draft") 
   val status = "pending"
   val isEditable: Boolean? = true
   
   val result = isEditable ?: status in statuses
   print(result)

But this initialization using the Elvis operator always returns false , if I move the status in statuses to a different variable or I wrap it in a run {status in statuses} then the code works as expected.
Am I missing something here or this is a bug?
You can test the example here: https://pl.kotl.in/4QDgoNvYi

[max.denissov]

Hi! Please, use clarifying parentheses val result = isEditable ?: (status in statuses)

[Joffrey]

I think the issue is that isEditable ?: status in statuses is understood as (isEditable ?: status) in statuses, so you need clarifying parentheses around your in check:

val result = isEditable ?: (status in statuses)

However, I'm surprised this compiles without the parentheses. There might be a bug in how elvis type is considered for contains:

statuses.contains(42 ?: "bob") // compiles fine, returns false
statuses.contains(42) // compile error

[Joffrey]

Mmh actually I believe it has to do with the fact that List is covariant in T and contains can be understood as being applied to a List<Comparable> here. The type of 42 ?: "bob" is likely Comparable and thus the contains call compiles.

The same could be said for 42 alone, but I guess the compiler doesn't go that far. It does work with explicit type argument:

statuses.contains<Comparable<*>>(42) // compiles fine

[Alejo]

Great explanation!

[Alejo]

Using clarifying parentheses solved the issue. Thanks!