<@U0VM8LM17>: ``` sealed class Envelope&lt;T, E&g...

# getting-started

[cedric]

@cdepillabout:

sealed class Envelope<T, E> {
    class Success<T>(val data: T): Envelope<T,E>()
    class Error<E, T>(val err: E, val extra: String): Envelope<T, E>()
}