KMP Screens in common code

[PriviteraStefano]

Hi, I'm new to this framework, just found out about this yesterday, but I really like the idea behind it and I'd love to experiment with it.
I'm trying to implement it in one of my KMP projects, but I got stuck while following the tutorial.

I'm writing the Presenter, the Screen and the UI in common code and I don't have any error or warnings in the IDE, but once I try to build the app I get Object 'AuthScreen' is not abstract and does not implement abstract member 'describeContentents'.

data class Username(val value: String)
data class Password(val value: String)
data class ShowPassword(val value: Boolean)

data object AuthScreen : Screen {
    data class State(
        val username: Username,
        val password: Password,
        val showPassword: ShowPassword,
        val eventSink: (Event) -> Unit
    ) : CircuitUiState

    sealed class Event : CircuitUiEvent {
        data class UsernameChanged(val username: String) : Event()
        data class PasswordChanged(val password: String) : Event()
        data object TogglePasswordVisibility : Event()
    }
}

class AuthUi : Ui<AuthScreen.State> {
    @Composable
    override fun Content(state: AuthScreen.State, modifier: Modifier) {
        AuthView(state, modifier)
    }
}

class AuthPresenter : Presenter<AuthScreen.State> {
    @Composable
    override fun present(): AuthScreen.State {
        var username by remember { mutableStateOf(Username("")) }
        var password by remember { mutableStateOf(Password("")) }
        var showPassword by remember { mutableStateOf(ShowPassword(false)) }

        return AuthScreen.State(
            username = username,
            password = password,
            showPassword = showPassword,
        ) { event ->
            when (event) {
                is AuthScreen.Event.UsernameChanged -> {
                    username = Username(event.username)
                }

                is AuthScreen.Event.PasswordChanged -> {
                    password = Password(event.password)
                }

                is AuthScreen.Event.TogglePasswordVisibility -> {
                    showPassword = ShowPassword(!showPassword.value)
                }
            }
        }
    }
}

@Composable
fun AuthView(
    state: AuthScreen.State,
    modifier: Modifier = Modifier
) {
    Scaffold(
        modifier = modifier,
    ) { innerPadding ->
        LazyColumn(
            modifier = Modifier.fillMaxSize().padding(horizontal = 12.dp, vertical = 24.dp),
            contentPadding = innerPadding,
            horizontalAlignment = Alignment.CenterHorizontally,
            verticalArrangement = Arrangement.Bottom
        ) {
            item {
                OutlinedTextField(
                    modifier = Modifier,
                    value = state.username.value,
                    onValueChange = { state.eventSink(AuthScreen.Event.UsernameChanged(it)) },
                    label = { Text("Username") },
                    singleLine = true
                )
            }
            item {
                OutlinedTextField(
                    value = state.password.value,
                    onValueChange = { state.eventSink(AuthScreen.Event.PasswordChanged(it)) },
                    label = { Text("Password") }
                )
            }
        }
    }
}

//In my app entry point 

        val circuit = Circuit.Builder()
            .addPresenter<AuthScreen, AuthScreen.State>(AuthPresenter())
            .addUi<AuthScreen, AuthScreen.State> { state, modifier -> AuthUi().Content(state, modifier) }
            .build()

        CircuitCompositionLocals(circuit) {
            CircuitContent(AuthScreen, modifier = Modifier.fillMaxSize())
        }

Since I'm building for Android, this looks like AuthScreen depends on @parcelize, as it is said in the docs.
Is there a way to work with Circuit in common code directly without depending on @parcelize?

Thanks in advance for the help!

[ZacSweers]

The multiplatform counter sample has an example of a multiplatform parcelize annotation you can adapt