Kotlin can't do this, or is the syntax wrong? Does...

# compiler

[reactormonk]

Kotlin can't do this, or is the syntax wrong? Doesn't know T in the inner object.

@Serializable
sealed interface Request<T> {
    data object Get
    data class Set(val value: T) : ReturnValue
}

[dmitriy.novozhilov]

Only inner classes can catch type parameters of containing classes as each specific object will have it's own actual parametrization
Set class in your example is not inner, but nested class

[reactormonk]

Ah ok, and then it can't be an interface, but needs to be an actual class etc, so probably more trouble than it's worth

[Youssef Shoaib [MOD]]

Are Get and Set meant to be implementations of Request? If so, the solution is simple:

@Serializable
sealed interface Request<out T> {
    data object Get: Request<Nothing>
    data class Set<out T>(val value: T) : ReturnValue, Request<T>
}

[reactormonk]

More of a thought experiment, the actual API's gotta be different 😭

[Youssef Shoaib [MOD]]

inner class is a very specific OOP concept. The closest general Kotlin feature would be something like context(...) class (which is getting removed lol). What you likely want is something akin to this:

@Serializable
sealed interface Request<T> {
    data object Get
    data class Set<T>(val request: Request<T>, val value: T) : ReturnValue
}

But as you can see, this is useless since rn there's no implementors of Request