Response Type acting like Either pattern

Response.kt

sealed class Response<out S, out E>
data class Success<S>(val success: S) : Response<S, Nothing>()
data class Failure<E>(val error: E) : Response<Nothing, E>()

fun <S, E, R> Response<S, E>.map(f: (S) -> R): Response<R, E> = when (this) {
    is Success -> Success(f(this.success))
    is Failure -> this
}

fun <S, E, R> Response<S, E>.flatMap(f: (S) -> Response<R, E>): Response<R, E> = when (this) {
    is Success -> f(this.success)
    is Failure -> this
}

fun <S, E> Response<S, E>.getOrElse(f: (E) -> S): S = when (this) {
    is Success -> this.success
    is Failure -> f(this.error)
}

fun <S, E> Response<S, E>.doOnSuccess(f: (S) -> Unit): Response<S, E> = when (this) {
    is Success -> {
        f(this.success)
        this
    }
    is Failure -> this
}

fun <S, E> Response<S, E>.doOnFailure(f: (E) -> Unit): Response<S, E> = when (this) {
    is Success -> this
    is Failure -> {
        f(this.error)
        this
    }
}