T11145.hs:8:1: error:
    • Data constructor ‘MkFuggle’ returns type ‘Fuggle
                                                  Int (Maybe Bool)’
        instead of an instance of its parent type ‘Fuggle
                                                     Int (Maybe (a, b))’
    • In the definition of data constructor ‘MkFuggle’
      In the data instance declaration for ‘Fuggle’