Any idea why this ``` val newStage = when { expiresInDays >= 2 -> 0...

# getting-started

[David Kubecka]

Any idea why this

val newStage = when {
                expiresInDays >= 2 -> 0
                expiresInDays in 0..1 -> 1
                expiresInDays < 0 -> 2
                else -> 3
            }

generates a warning Condition 'expiresInDays < 0' is always true in IDEA? (expiresInDays is of type Long.)

[ephemient]

presuming expiresInDays is a val, the IDE inspection knows that the first 3 cases cover everything. Kotlin doesn't, though: https://youtrack.jetbrains.com/issue/KT-34548

[David Kubecka]

I (and IDE IMO as well) am not talking about the last condition but about the 3rd one expiresInDays < 0

[David Kubecka]

And yes, expiresInDays is val

[David Kubecka]

Thanks for the link! That would be my second question anyway 🙂

[ephemient]

IDE is telling you that your code has the same effect as

val newStage = when {
                expiresInDays >= 2 -> 0
                expiresInDays in 0..1 -> 1
                true -> 2
                else -> 3
            }

[David Kubecka]

Ah, I see

[ephemient]

if you only use expiresInDays >= 2 ->, expiresInDays in 0..1 ->, and else -> as the three cases, the compiler will know it's exhaustive and you also don't have IDE warnings

[Klitos Kyriacou]

I just realised that "else" could always be replaced by "true" in when statements/expressions, making "else" redundant (except after "if"). But "else" sounds more sensible anyway.

[ephemient]

when writing guards in Haskell, it is conventional that the fallback case is | otherwise ->. that isn't a language keyword, it's just defined as otherwise = True.