androidx.fragment:fragment-ktx:1.2.0-rc02 library contains lint checks for when one doesn't use viewLifecycleOwner property as LifecycleOwner, while observing LiveData in a Fragment. This repository shows the added lint check is missing a check for when one uses the observe extension function instead of the class function.
When running lint task on the project the FragmentLiveDataObserve lint check doesn't report errors for liveData.observe(this) {} or liveData.observe(this, {}), which are extension functions.
Only error is reported for liveData.observe(this, Observer { }).