[1mMain.hs:5.15:[1;31m error:[0m[1m
   • Data family constructor result type 'F Int' does not match instance head
     'F [a]'
   • In data family instance 'F [a]':
  [1;34m|[0m
[1;34m5[0m [1;34m| [0mdata instance [1;31mF[0m [a] where
  [1;34m|[0m               [1;31m^[0m

