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kotlinlang

Is there annotation (1.2.x) to force compiler to rise error on not-exhaustive `when`?

isn’t that the default behavior?
but the compiler needs to be able to infer it’s not exhaustive (_e.g._ enum)

That's only the behavior for expression `when`s, not statements. And I agree that is something that's missing.

For now you can do something like `inline fun Any?.exhaustive() = Unit`, use like this:
```when (x) { ... }.exhaustive()```
It forces the `when` to be an expression.

Problem is that that pollutes the global namespace.

I have found even more handy workaround:
```
val &lt;T&gt; T.exhaustive: T
    get() = this
```
here: <https://proandroiddev.com/til-when-is-when-exhaustive-31d69f630a8b>
But I have hoped something official is possible (that is to treat a warning as compile time error).

Meh, why would you want that? Either you use it as an expression and then you don't need any tricks, and otherwise you don't need the `.exhaustive()` to return anything.

For readability (that is to express intention explicitly) at all cases. But you are right, of course, it isn't obligatory. Still not sure which way to use. I guess, it is matter of taste :slightly_smiling_face:

No definitely don't do anything funky when you actually want the expression, just use the language feature then!

I also found it useful for side effect `when` that I still want to handle all cases

Okay, but then just do something like ```val Any?.exhaustive
    get() = Unit```
no need to make it more confusing.