Component used: Compose Version used: 1.0.0-alpha12 Devices/Android versions reproduced on: Pixel 4 Android 11

The recommended code to replace savedInstanceState{ 0 } is rememberSaveable { mutableStateOf(0) }

However, I've found this causes a crash whenever the app is minimized.

The exception thrown is

java.lang.RuntimeException: Parcel: unable to marshal value androidx.compose.runtime.SnapshotMutableStateImpl@5a847c2

After digging into the code I believe this is caused by the special version of rememberSaveable for MutableState objects doesn't have a default saver parameter so the normal version is used which doesn't know how to save a MutableState.

I think changing the rememberSaveable definition from

@Composable
fun <T> rememberSaveable(
    vararg inputs: Any?,
    stateSaver: Saver<T, out Any>,
    key: String? = null,
    init: () -> MutableState<T>
): MutableState<T> = rememberSaveable(
    inputs,
    saver = mutableStateSaver(stateSaver),
    key = key,
    init = init
)

to

@Composable
fun <T> rememberSaveable(
    vararg inputs: Any?,
    stateSaver: Saver<T, out Any> = autoSaver(),
    key: String? = null,
    init: () -> MutableState<T>
): MutableState<T> = rememberSaveable(
    inputs,
    saver = mutableStateSaver(stateSaver),
    key = key,
    init = init
)

would fix this.