Record update with duplicate fields is incorrectly accepted

module T21959 where

data R = R { fld :: Int }
  deriving stock Show

f :: R -> R
f r = r { T21959.fld = 1, fld = 2 }

>>> show (f (R 0))
> "R {fld = 2}"

This is because the duplicate field check doesn't take into account qualified names. I will fix in !8686.