tests/note.hs:1:1: Error: Unused LANGUAGE pragma
Found:
  {-# LANGUAGE RecordWildCards #-}
Why not remove it.
Note: you may need to add DisambiguateRecordFields

tests/note.hs:5:11: Warning: Use null
Found:
  length xs == 0
Why not:
  null xs
Note: increases laziness

2 suggestions