Can I test for `when` exhaustiveness without assigning the result to a variable? `val x: Unit =` fee...

# compiler

[reactormonk]

Can I test for when exhaustiveness without assigning the result to a variable? val x: Unit = feels a bit silly.

[wasyl]

There’s https://youtrack.jetbrains.com/issue/KT-12380/Support-sealed-exhaustive-whens so the exhaustive behavior will be default in future versions on Kotlin (https://youtrack.jetbrains.com/issue/KT-12380/Support-sealed-exhaustive-whens#focus=Comments-27-5034058.0-0)

[wasyl]

I think you should be able to use it already with progressive mode (https://kotlinlang.org/docs/whatsnew13.html#progressive-mode) but I haven’t tried it myself

[wasyl]

Alternatively, as a quick workaround, you can define an extension function or property exhaustive that, when called on the when result, will force exhaustiveness. Another way is what I use often, to have the when a result of an expression function — it very often makes sense anyway

[ephemient]

https://github.com/cashapp/exhaustive#readme

[ephemient]

the built-in exhaustive mode is already default in Kotlin 1.7

[ephemient]

my preference for a workaround in earlier versions or in cases where the built-in exhaustiveness checker isn't enabled by default is a trailing

when {
    ...
}.let { /* exhaustive */ }

which has no extra impact

[Jaime]

@ephemient is possible disable exhaustive in kotlin 1.7?

[ephemient]

with -language-version 1.5 it should not be enabled