File "t02bad.ml", line 10, characters 0-61:
10 | module rec A : sig type t = B.t end = struct type t = B.t end
     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Error: The definition of "A.t" contains a cycle:
         "B.t" = "A.t",
         "A.t" = "B.t",
         "B.t" = "A.t"