var value by remember { mutableStateOf(default) } produce error, why?

I'm referring to the example in https://developer.android.com/jetpack/compose/state. When I code

var expanded by remember { mutableStateOf(false) }

It errors stating

Type 'TypeVariable(T)' has no method 'getValue(Nothing?, KProperty<*>)' and thus it cannot serve as a delegate

The below works though

val expanded = remember { mutableStateOf(false) }

// OR

val (expanded, setExpanded) = remember { mutableStateOf(false) }