So, effects and the unaryPlus have been removed. How would the following code be rewritten to follow the latest fashion in Compose? I think it was originally written in an article by @Luca Nicoletti and doesn't compile anymore on Dev04:

// general purpose observe effect. this will likely be provided by LiveData. effect API for
// compose will also simplify soon.
fun <T> observe(data: LiveData<T>) = effectOf<T?> {
    val result = +state<T?> { data.value }
    val observer = +memo { Observer<T> { result.value = it } }

    +onCommit(data) {
        data.observeForever(observer)
        onDispose { data.removeObserver(observer) }
    }

    result.value
}

Ref: https://medium.com/swlh/android-mvi-with-jetpack-compose-b0890f5156ac

Change

= effectOf<T?>

to,

: T?

in the signature (normal return value) and add

@Composable

as a function annotation, then remove the `+`s from the effect calls in the function body and add an explicit

return

keyword at the end. Change

memo

to

remember

as it was renamed.

yep, that. ☝️

Nice I was so close... just had the return statement wrong. Will try that out, thanks guys.

the syntax change also removes the weirdness around operator precedence that made these not work so well as extension functions or properties; you could just as easily declare this as,

@Composable
val <T> LiveData<T>.latestValue: T? get() { ... }

if you'd prefer.

I like that too. And, I nearly immediately run into an Exception during code generation.

e: java.lang.IllegalStateException: Backend Internal error: Exception during code generation
Element is unknownThe root cause java.util.NoSuchElementException was thrown at: androidx.compose.plugins.kotlin.compiler.lower.ComposableCallTransformer.irComposableExpr(ComposableCallTransformer.kt:1362)

Caused by: java.util.NoSuchElementException: Collection contains no element matching the predicate.

I guess I'll go on a hunt for what might be causing that.