Given code like this: ```enum class Foo { Bar, Baz, } fun foo(foo: Foo) = when (foo) { ...

# intellij

[wasyl]

Given code like this:

enum class Foo {
    Bar,
    Baz,
}

fun foo(foo: Foo) = when (foo) {
    Foo.Bar -> 2
    Foo.Baz -> 3
}

fun main() {
    println(foo(Foo.Bar))
}

Is there any inspection I can run to find out that Foo.Baz can be removed? I want to find actually unused code, and Foo.Baz is effectively unreachable if nothing ever uses Foo.Bar as value parameter (?) or assignment value

[CLOVIS]

I don't think that's true. Code could be using Foo.entries() . If this is a library, some external code could be using it too.

[wasyl]

If this is a library, some external code could be using it too.

that's fair, but I still want to run it if I know all my modules are self-contained if I'm developing an application, or if the identifiers are not public

Code could be using Foo.entries()

That's right 😕 Same for sealed classes and reflection I guess, but I'd still want to find declarations without explicit usage. Technically it might not be correct, but it'd still be useful

[CLOVIS]

You could run ‘find usage’ on Baz, no?

[wasyl]

I can but I have to run it for every declaration, look at the results and determine that all are just reads. I want to run this on entire enum class with ~40 entries for example, and find all entries that I can potentially remove

[christophsturm]

if you make fun foo private you will get a notification “value of parameter foo is alway Foo.Bar”

[christophsturm]

then you can remove that case and then Foo.Baz is unused

[wasyl]

I don't see that warning 👀 But regardless this wouldn't work as soon as I have more entries:

private enum class Foo {
    Bar,
    Baz,
    Baa,
}

private fun foo(foo: Foo) = when (foo) {
    Foo.Bar -> 2
    Foo.Baz -> 3
    Foo.Baa -> 4
}

private fun main() {
    println(foo(Foo.Bar))
    println(foo(Foo.Baa))
}

[christophsturm]

i pasted it into a .kt file maybe thats the difference. but you are right!

[wasyl]

I wanted to keep the example simple, in reality I have an enum class or a sealed interfaces with ~20-40 entries, and those entries are all mapped to something else in one function.
Then application code passes these enum/interface classes somewhere, but at some point some of the entries might stop being used. They'll still be mapped so technically used as far as IDE is concerned, but I want to find candidates to remove

[wasyl]

And of course it's not one enum, it's dozens of enums with dozens of entries, so I really need something automated

[christophsturm]

idea has a warning “value is written but never read”, and I think there should be something like this for your case

[christophsturm]

but i am not sure how to call it

[wasyl]

I only see this one, but yeah that's what I want. Or rather the opposite — value is read (in a when) but never written (passed)

[christophsturm]

maybe file a youtrack with a feature idea?

[wasyl]

Yeah I think I will. I just hoped something exists already 😄

[wasyl]

Opened https://youtrack.jetbrains.com/issue/KTIJ-30902/Inspection-to-find-declarations-never-used-in-write-position