Methods are not analyzed if a factory function's object is bound before returning

[fantazio]

Context

If a factory function binds its result (with or without manipulating the binding) before returning it, then its methods are not tracked.

Example and reproduction

(* /tmp/bind_before_return/bind_before_return.ml *)
let factory () =
  let res =
    object
      method used = ()
      method unused = ()
    end
  in
  res

let () = (factory ())#used

$ ocamlopt -bin-annot bind_before_return.ml
$ dead_code_analyzer --nothing -M all bind_before_return.cmi bind_before_return.cmt
Scanning files...
 [DONE]

.> UNUSED METHODS:
=================

Nothing else to report in this section
--------------------------------------------------------------------------------

We can see that there is not unused method reported although factory#unused should be reported. Without the binding to res in factory, the results are:

Scanning files...
 [DONE]

.> UNUSED METHODS:
=================
/tmp/bind_before_return/bind_before_return.ml:2: factory#unused

Nothing else to report in this section
--------------------------------------------------------------------------------