Noticed this warning today `Non exhaustive when statements o

Question

Noticed this warning today `Non exhaustive when statements on sealed class interface will be prohibited in 1 7 add else branch` Does that mean using a sealed class interface will no longer be exhaustive in a `when` I thought that was a feature of ``sealed`

ephemient · Answer

you need to explicitly match everything or add `else`

ephemient · Answer

see <https kotlinlang org docs whatsnew1530 html exhaustive when statements for sealed and boolean subjects>

Roukanken · Answer

currently in `when` statements you don t need else there is an implicit else gt do nothing in statements when s without return value in 1 7 this will no longer be case and you ll need to add the else clause even in statements

ephemient · Answer

there is still an implicit else gt do nothing for non sealed non enum types

Roukanken · Answer

and yeah this is only a topic when we re talking about sealed enums

ghosalmartin · Answer

hmm okays but what about if am attaching the result of a `when` to a variable and the switching type is a sealed

Roukanken · Answer

in that case then even in current version you need to list all the cases OR use an else the 1 7 change is just that it will work the same way even if you are not using the result of the when

ephemient · Answer

exactly if the value is used the `when` must be exhaustive always either by having full branch coverage or by `else` regardless of the type if the value is not used previously Kotlin did not enforce exhaustive `when` but for enums and sealed types it will

Richard Gomez · Answer

< ghosalmartin> What does your code look like I ran into a strange issue last week with a `when` block and a `sealed interface `It forced me to add an `else` statement despite having all the cases defined

ghosalmartin · Answer

tbf this code is purely to flex the feature shall we say but

ghosalmartin · Answer

but this gives me the warning

ghosalmartin · Answer

```sealed interface House data class Semidetached val sharedWall String House data class Detached val noSharedWall String House fun test val myHouse House = House Detached when myHouse is House Detached gt myHouse noSharedWall is House Semidetached gt myHouse sharedWall ```

ephemient · Answer

IDE or command line compiler there s a number of IJ plugin bugs around this such as

Richard Gomez · Answer

gt IDE or command line compiler there s a number of IJ plugin bugs around this such as In my case it was the IDE Good to know