Please take a look at this function at jetpack compose sample: https://github.com/android/compose-samples/blob/master/JetNews/app/src/main/java/com/example/jetnews/ui/home/HomeScreen.kt#L97

@Composable
private fun HomeScreenTopSection(post: Post) {
    ProvideEmphasis(emphasis = EmphasisLevels().high) {
        Text(
            modifier = LayoutPadding(start = 16.dp, top = 16.dp, end = 16.dp, bottom = 0.dp),
            text = "Top stories for you",
            style = MaterialTheme.typography().subtitle1
        )
    }
    Ripple(bounded = true) {
        Clickable(onClick = {
            navigateTo(Screen.Article(post.id))
        }) {
            PostCardTop(post = post)
        }
    }
    HomeScreenDivider()
}

As you see it's an incomplete composable function because we are calling 3 other functions without a Row or Column, and

HomeScreenTopSection

can draw correctly just because the parent has called it inside a column: https://github.com/android/compose-samples/blob/master/JetNews/app/src/main/java/com/example/jetnews/ui/home/HomeScreen.kt#L88

Column(modifier = modifier) {
            HomeScreenTopSection(post = postTop)
            HomeScreenSimpleSection(posts = postsSimple)
            HomeScreenPopularSection(posts = postsPopular)
            HomeScreenHistorySection(posts = postsHistory)
        }

So if I call

HomeScreenTopSection

outside a column or row, there are multiple possible solutions: 1) the compose framework can decide to put it inside a Row for example 2) Keep the first one and throw away others and seems that compose follows this approach at the moment. 3) Threw error I think first and second solutions are not appropriate solutions and seems that throwing compile time error is not possible and just remains run time error. Our functions return Unit, if they return something the

HomeScreenTopSection

should return a list and the problem is solved we can throw compile time errors. but with returning functions we loose lots of its benefits so that's not an option here, but what about adding annotations like

ThisShouldBeCalledInsideRowOrColumn

(I know it's a worst naming you ever seen 😬) ?

this is not a runtime exception because all contexts in which you are able to call a composable are contexts that have a layout policy implied by the parent

Yes, but is it valid if I call it outside of Row or Column? and nothing prevents me from doing that.

if you call it inside of a composable function, a layout policy exists

Got it, Thanks