#     type 'a t = 'a
# Characters 42-43:
  let f (g : 'a list -> 'a t -> 'a) s = g s s;;
                                            ^
Error: This expression has type 'a list
       but an expression was expected of type 'a t = 'a
       The type variable 'a occurs inside 'a list
# Characters 42-43:
  let f (g : 'a * 'b -> 'a t -> 'a) s = g s s;;
                                            ^
Error: This expression has type 'a * 'b
       but an expression was expected of type 'a t = 'a
       The type variable 'a occurs inside 'a * 'b
#