Hello, I'm just starting out on learning how to use KotlinX (and serdes in general) and I am running...

# serialization

[RayeW47]

Hello, I'm just starting out on learning how to use KotlinX (and serdes in general) and I am running in to an issue I can't seem to understand how to solve.

I have a @Serializable class A and I have a helper class for companions to automatically grab a file to deserialize something in to an A and put it in A(.Companion).INSTANCE.
However, using .INSTANCE gets a bit annoying to use and looks kind of gross, so I am trying to convert A in to a @Serializable sealed interface A, so that A.Companion can be an A and I can simply reference A rather than A(.Companion).INSTANCE.
I can't seem to understand enough to get this working with a sealed interface, I keep running in to polymorphism errors or NPEs if I try to delegate similar to how I do in Loader, so I am here for help.
Here's a minimum example.

abstract class Loader<T>(val type: StringFormat, val filePath: String, val serializer: () -> KSerializer<T>, ) {
    val INSTANCE by lazy {
        type.decodeFromString(serializer(), File(filePath).readText())
    }
}

current

@Serializable
class A(val someProperty: Int) {
    companion object: Loader<A>(
        type = Json.Default, filePath = "./config/A-config.json", serializer = { A.serializer() }
    )
}

fun main() {
    A.INSTANCE.someProperty
}

goal

@Serializable
sealed interface A {
    val someProperty: Int
    companion object: Loader<A>(
        type = Json.Default, filePath = "./config/A-config.json", serializer = { A.serializer() }
    )
}

fun main() {
    A.someProperty
}