Hi,
I have encountered a behavior of the type checking of recursive modules which is hard for me to understand.
Especially so, since the code used to compile with Ocaml 3.10.0 but does not with
3.10.2. And, an almost similar piece of code compiles correctly.
I tried to extract the smallest piece of code that exhibits the problem, but it's still quite long. Sorry.
Here is the code that does not type with 3.10.2:
=======================================
module type BSig =
sig
type t
val f: t -> unit
end
module type ASig = functor(B: BSig) ->
sig
type t
val g: B.t -> unit
end
module Make(C: BSig) =
struct
type t = int
let g _ = ()
end
module MakeA = (Make: ASig)
module rec A:
sig
type t
val g: B.t -> unit
end
= MakeA(B)
and B:
sig
type t = int * A.t
val f: t -> unit
end
=
struct
type t = int * A.t
let f x = A.g x (* does not type *)
(*
let f (a, b) = A.g (a, b) (* types correctly *)
*)
end
=========================
Note that if function f is replaced by the commented version, then the type checker succeeds. Even though, this code modification is only giving the additional information that the argument of f is a pair.
It would be nice for both versions of the code to compile, because the current behavior of the type checker seems to me not easily predictable.
Thank you in advance for your help,