[1mMain.hs:5.17:[1;31m error:[0m[1m
   • Expected `m` but got `b`
   • Relevant bindings:
       x :: b
       f :: b -> a
       apply :: T a -> m
   • In equation `apply (Main.T f x)  = x`
   • In function `Main.apply`
   • In recursive group:
         Main.apply
  [1;34m|[0m
[1;34m5[0m [1;34m| [0mapply (T f x) = [1;31mx[0m
  [1;34m|[0m                 [1;31m^[0m

