[Caml-list] Matching exhausitvity with GADT and modules

[Joris Giovannangeli <joris@giovannangeli.fr>]

Hi,

The following snippet is compiling without warning :

module A = struct

  type foo
  type bar

  type 'a gadt =
      Foo : int -> foo gadt
    | Bar : int -> bar gadt

  let f = function
     | Foo i -> i
end

But if I split the code into two modules :

module A = struct

  type foo
  type bar

  type 'a gadt =
      Foo : int -> foo gadt
    | Bar : int -> bar gadt

end

module B = struct
  include A

  let f : foo gadt -> int = function
     | Foo i -> i
end

I get the following warning :

Warning 8: this pattern-matching is not exhaustive.
Here is an example of a value that is not matched:
Bar _

How can i work around this issue ? As far as i can tell, it is not
possible for Bar to be matched by the function f.

Best regards,
joris