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.)

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

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

expiresInDays < 0

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
            }

Ah, I see

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

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.

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

.