sealed class TodoAction : Action

sealed class TodoListAction : TodoAction()
object LoadTodos : TodoListAction()

sealed class TodoDetailAction : TodoAction()
data class GetTodo(val id: Int) : TodoDetailAction()

-----

fun interface Reducer<S : StoreState, A : Action> {
    operator fun invoke(state: S, action: A): S
}

----

val TodoReducer: Reducer<TodosState, TodoListAction> =
    Reducer { state, action ->
        when(action) {
          is LoadTodos -> state      
        }
    }

----

val a: Reducer<TodosState, TodoAction> = TodoReducer 
//Error: Type mismatch.
        Required: Reducer<TodosState, TodoAction>
        Found: Reducer<TodosState, TodoListAction>