I feel like I m really missing something so I will appreciat

Question

I feel like I m really missing something so I will appreciate any insight here I m trying to get the redundant else warning to fire from the Kotlin compiler and I can t get it to work

JasonB · Answer

my understanding is that given an exhaustive `when` on an enum adding an `else` clause should trigger a warning

JasonB · Answer

is that understanding correct

Chris Lee · Answer

able to see that warning both in IntelliJ and the compiler via Gradle ```w file Users chrislee IdeaProjects clario clario app modules frontend phpcgi src main kotlin clario fe phpcgi FastCgiDecoder kt 166 21 when is exhaustive so else is redundant here```

Chris Lee · Answer

do you have a code snippet of what isn t working

JasonB · Answer

``` when vehicle fuelType FuelType DIESEL gt CaFuelTypeEnum DIESEL FuelType ELECTRIC gt CaFuelTypeEnum ELECTRIC FuelType FLEX gt CaFuelTypeEnum FLEX FUEL FuelType GAS gt CaFuelTypeEnum GASOLINE FuelType FULL HYBRID gt CaFuelTypeEnum HYBRID GASOLINE ELECTRIC FuelType PLUG IN HYBRID gt CaFuelTypeEnum HYBRID GASOLINE ELECTRIC FuelType CNG gt CaFuelTypeEnum NATURAL GAS POWERED FuelType LPG gt CaFuelTypeEnum PROPANE FuelType HYDROGEN gt CaFuelTypeEnum HYDROGEN FUEL CELL else gt CaFuelTypeEnum BUTANE ```

JasonB · Answer

language version 1 8

JasonB · Answer

Kotlin plugin 231 1 8 20 IJ8109 175

Chris Lee · Answer

Doing this flags the else as redundant Kotlin 1 8 as well ```public enum class FuelType DIESEL ELECTRIC public class Test public fun foo fuelType FuelType when fuelType FuelType DIESEL gt TODO FuelType ELECTRIC gt TODO else gt ```

Chris Lee · Answer

However this does not when the type is nullable ```public enum class FuelType DIESEL ELECTRIC public class Test public fun foo fuelType FuelType when fuelType FuelType DIESEL gt TODO FuelType ELECTRIC gt TODO else gt ```

Adam S · Answer

does `vehicle fuelType` come from Java Is it nullable What happens if you try `when vehicle fuelType ` or adding a `null gt ` branch

Chris Lee · Answer

adding an explicit null check does flag the else as redundant ```public enum class FuelType DIESEL ELECTRIC public class Test public fun foo fuelType FuelType when fuelType FuelType DIESEL gt TODO FuelType ELECTRIC gt TODO null gt else gt ```

JasonB · Answer

no Java involved in this code and it s not nullable so adding null generates its own warning

JasonB · Answer

also gets flagged as unnecessary

Chris Lee · Answer

are you certain that all the enumerated values are listed

JasonB · Answer

well if I remove the else I also don t get a warning or compile failure

JasonB · Answer

so yes I m pretty sure the `when` is exhaustive

Chris Lee · Answer

In IntelliJ for an empty when it offers the option to all remaining branches may be worth comparing against that to ensure all branches are there

Chris Lee · Answer

For example this no longer generates a redundant else warning as `HYBRID` is not in the when ```public enum class FuelType DIESEL ELECTRIC HYBRID public class Test public fun foo fuelType FuelType when fuelType FuelType DIESEL gt TODO FuelType ELECTRIC gt TODO else gt ```

JasonB · Answer

if I recreate the when as empty then have IntelliJ add all branches which come with TODOs and then add an else I still do not get the warning

JasonB · Answer

```when vehicle fuelType FuelType CNG gt TODO FuelType DIESEL gt TODO FuelType ELECTRIC gt TODO FuelType FLEX gt TODO FuelType FULL HYBRID gt TODO FuelType GAS gt TODO FuelType HYDROGEN gt TODO FuelType LPG gt TODO FuelType PLUG IN HYBRID gt TODO else gt ```

Adam S · Answer

If I try recreating your example in Kotlin Playground I get a warning on the else statement as expected <https pl kotl in Gs4ouSqqj>

Chris Lee · Answer

< JasonB> what does the source for the enum look like

JasonB · Answer

```data class Vehicle val vehicleListingId Int val sellingPriceInCents Int val vin String val year Int val make String val model String val bodyType BodyType val condition Condition val mileage Int val priceInCents Int val fuelType FuelType val modelCode String val dealerId Int val curbWeight Int val msrpInCents Int val baseMsrpInCents Int val accessoryPriceInCents Int fun getCurbWeightOrDefault Int = curbWeight 3000 enum class BodyType CHASSIS CONVERTIBLE COUPE HATCHBACK MINIVAN PICKUP SEDAN SUV VAN WAGON enum class FuelType CNG DIESEL ELECTRIC FLEX FULL HYBRID GAS HYDROGEN LPG PLUG IN HYBRID enum class Condition NEW USED ```

Chris Lee · Answer

hmmm copying that code directly does show then redundant else warning

Chris Lee · Answer

Not able to reproduce that consistently get warning unless a branch is omitted or variable is nullable <https pl kotl in CNmyn8s9X>

Adam S · Answer

have you suppressed warnings in the build file <https kotlinlang org docs compiler reference html nowarn> or with a ` Suppress ` or ` file Suppress ` anywhere

Chris Lee · Answer

Something like ` Suppress REDUNDANT ELSE IN WHEN `

JasonB · Answer

we do have autogenerated files that have their own suppressions but never that one and not on this file

Chris Lee · Answer

does a small sample enum when show the same behaviour

JasonB · Answer

ok I think it s an issue with gradle multimodule

JasonB · Answer

if I have an enum in the same module the check works fine but if I define the enum in a separate module it doesn t fire

Chris Lee · Answer

interesting have a mm project here let me try it

Chris Lee · Answer

yep This code snippet ```public class Test public fun foo fuelType Vehicle FuelType when fuelType Vehicle FuelType CNG gt TODO Vehicle FuelType DIESEL gt TODO Vehicle FuelType ELECTRIC gt TODO Vehicle FuelType FLEX gt TODO Vehicle FuelType FULL HYBRID gt TODO Vehicle FuelType GAS gt TODO Vehicle FuelType HYDROGEN gt TODO Vehicle FuelType LPG gt TODO Vehicle FuelType PLUG IN HYBRID gt TODO else gt ``` warns of redundant else when in same module but not if in different module

Chris Lee · Answer

that s surprising unexpected

JasonB · Answer

quite slightly smiling face

Chris Lee · Answer

checking to see if the same happens for a sealed object

Chris Lee · Answer

yea same problem

JasonB · Answer

ok good to know

JasonB · Answer

appreciate everyone s help I ll see if this already exists in YouTrack

JasonB · Answer

JasonB · Answer

this is intentional

Nino · Answer

Wow seems like a terrible idea disappointed

Chris Lee · Answer

oh ugh that s inconsistent now I need to review a bunch of code to add `else gt error WTF `

Chris Lee · Answer

it s really an artifact of the limited module system in JVM there s no distinction between a nicely separated multi module project that is compiled together and any other random JAR dependency pulled in as any JAR module could in theory be replaced at runtime

David Kubecka · Answer

There are more consequences of that limitation e g <https youtrack jetbrains com issue KT 57311 False positive SMARTCASTIMPOSSIBLE when using a class property from main source in tests>