Please can someone explain what is happening here:...

# getting-started

[Mark]

Please can someone explain what is happening here: https://pl.kotl.in/3lF-S9LUl

var check1 = true
var check2 = false
val test = if (check1) {
    null
} else if (check2) {
    listOf("foo")
} else {
    listOf("bar")
}.map { 2 }
println(test)

It seems we don’t need to use safe null on the map call. However, if we remove the middle branch, then we do need it:

var check1 = true
var check2 = false
val test = if (check1) {
    null
} else {
    listOf("bar")
}?.map { 2 }
println(test)

In both cases (without the map), the type of test is List<String>?

[sanggggg]

I think it’s because the second code is recognized as below

fun main() {
    var check1 = true
    var check2 = false
    val test = if (check1) {
        null
    } else {
        if (check2) {
        	listOf("foo")
	    } else {
        	listOf("bar")
    	}.map { 2 }
    }
    println(test)
}

[Mark]

Yes, it looks to be the case. But is it intended, and isn’t it confusing?

[ephemient]

exactly that.
https://kotlinlang.slack.com/archives/C0B9K7EP2/p1651041143051719

[ephemient]

it's "intended" as far as being consistent with how the Kotlin grammar is defined, but it's definitely confusing and I think the grammar should change

[Mark]

Yup definitely confusing: https://pl.kotl.in/Mhd5jD9RD

[ephemient]

whether or not kotlin gets fixed (which it may not as this would be a breaking change), this is better written

when {
    check1 -> 1
    check2 -> 2
    else -> 3
}.let { println("got $it") }

[Mark]

I updated the sample code https://pl.kotl.in/SVXHS8mSn to simplify it a bit. It’s so easy to introduce a bug this way. Judiciously switching to when instead of else if does sound like the more sensible approach

[sanggggg]

It’s quite confusing 😢
I think it’d be good to add it as a lint rule. (like warning referenced consecutive if elses) What do you guys think about this?

If agreed, I’ll report the issue to detekt

[ephemient]

I filed https://youtrack.jetbrains.com/issue/KT-52608/Confusing-precedence-after-chained-if-else asking for a change in Kotlin itself, but if that doesn't go anywhere then linters like ktlint or detekt are the next best place.

[Mark]

Hmm, marked as duplicate. Actually I had a feeling I’d seen (and starred!) that before.