[1mMain.hs:2.9-14:[1;31m error:[0m[1m
   • Cannot unify `t` with `[t]` because of occurs check
   • Relevant bindings:
       x :: t
       f :: t -> [t]
   • In expression '[x] : []':
   • In equation `f x  = x : ([x] : [])`
   • In function `Main.f`
   • In recursive group:
         Main.f
  [1;34m|[0m
[1;34m2[0m [1;34m| [0mf x = x:[1;31m[x]:[][0m
  [1;34m|[0m         [1;31m^^^^^^[0m

