Hi Jian,
I tested the latest v14 patch on current master.Everything worked as expected in my testing. I verified that whole-row referenced constraints and indexes are handled correctly when dropping a column, and that ALTER COLUMN SET DATA TYPE still reports an error when whole-row dependent objects exist. I also tested the newly merged trigger and row-level security policy cases. ALTER TABLE ... DROP COLUMN correctly reports dependency errors when a whole-row reference exists, and using CASCADE removes the dependent trigger or policy as expected. I also verified that the remaining table definition is correct after the operation, and I didn't notice any unexpected behavior during testing.
Thanks for the update.
regards
lakshmi