File "pr6323.ml", line 1:
Warning 63 [erroneous-printed-signature]: The printed interface differs from
  the inferred interface. The inferred interface contained items which could
  not be printed properly due to name collisions between identifiers.
  File "pr6323.ml", line 15, characters 2-24:
  Definition of type t
File "pr6323.ml", line 8, characters 0-26:
  Definition of type t/2
  Beware that this warning is purely informational and will not catch all
  instances of erroneous printed interface.
type 'a t = B of 'a t list
val foo : 'a -> 'b t list -> 'c t list
module DT :
  sig type 'a t = { bar : 'a; } val p : 'a t/2 list -> 'b t/2 list end