The lambda expression is unused

While using Android's Switch, I was attaching a setOnCheckedChangeListener to it and got this warning

The lambda expression is unused. If you mean a block, you can use 'run {...}'

Here' the code snippet:

switchAction.setOnCheckedChangeListener({
    _, isChecked ->
    {
        preferences.userStatus = isChecked
        switchToggleVisibility(isChecked)
        if (isChecked) {
            fetchStats()
            getOrders()
        } else {
            releaseOrder()
        }
    }
})

Using run does fix this warning, but does anyone know the cause behind this? How is the lambda expression unused?