dune vs jbuilder

dune-out

File "lib_helpers/kafka_producer.ml", line 1:
Error: The implementation lib_helpers/kafka_producer.ml
       does not match the interface lib_helpers/.kafka_helpers.objs/byte/kafka_helpers__Kafka_producer.cmi:
       Values do not match:
         val stream_to : ('a, unit) sink -> 'a iterable -> unit
       is not included in
         val stream_to : ('a, 'b) sink -> 'a iterable -> 'b
       File "lib_helpers/kafka_producer.mli", line 9, characters 0-48:
         Expected declaration
       File "lib_helpers/kafka_producer.ml", line 4, characters 4-13:
         Actual declaration

kafka_producer.ml

type ('a,'b) sink = unit -> ('a -> unit) * (unit -> 'b)
type 'a iterable = ('a -> unit) -> unit

let stream_to : ('a, 'b) sink -> 'a iterable -> 'b = fun open_sink iterable ->
  let (push,close) = open_sink () in
  try iterable push ; close ()
  with error -> close (); raise error 

kafka_producer.mli

type ('a,'b) sink = unit -> ('a -> unit) * (unit -> 'b) 

type 'a iterable = ('a -> unit) -> unit
val stream_to: ('a,'b) sink -> 'a iterable -> 'b