Separate instance of classes calling Composable function

Let's say I have some kind of structure like this:

data class C(val value: Int) {
    @Composable
    fun MyComposable() {
        Text("Value: $value")
    }
}

@Composable
fun ParentComposable(stateFlow: StateFlow<C>) {
    val state by stateFlow.collectAsState()
    state.MyComposable()
}

I'm assuming the composable will be treated as an entirely separate instance and the whole thing will need to be recomposed (no children skipped even). Is this correct?

There are several issues with your code:

• You should never pass flows to a composable. Only pass simple objects, like data classes or primitive data types. Where you obtain the flow, collect it immediately and only pass its content to your composables.
• Composable functions that emit UI should be top-level functions, not members of classes - and certainly not data classes.
• Data classes are meant to be simple containers for data, they are not meant to contain UI logic (e.g. composable functions). The relation between data classes and composables is that instances of the former are passed as parameters to the latter.
• When collecting flows in a composable function you should use collectAsStateWithLifecycle instead of collectAsState to make sure the flows are stopped and resumed according to the composable's lifecycle.

When you fix all of the above your original question becomes moot. For the sake of completeness, though: Since the function belongs to the class and not the instance, and the class never changes, the composable will be recognized as the same one and no additional recompositions will take place. MyComposable is recomposed only when the new C instance has a different value.