RepPolyRecordPattern.hs:7:35: error:
    The type of the first pattern in the equation for ‘fld’
    does not have a fixed runtime representation:
      X a :: TYPE rep

RepPolyRecordPattern.hs:13:1: error:
    The type of the first pattern in the equation for ‘upd’
    does not have a fixed runtime representation:
      X a :: TYPE rep