Original bug ID: 3476
Reporter: administrator
Assigned to: @xavierleroy
Status: closed (set by @xavierleroy on 2006-08-30T11:57:53Z)
Resolution: won't fix
Priority: normal
Severity: minor
Category: ~DO NOT USE (was: OCaml general)
Related to: #4049 #4615 #5058
Child of: #5302
Monitored by: @lpw25 @mmottl

Bug description

Hi,

this mail has already been sent to you once, but didn't show up in the
bug tracker (possibly a problem with the mail agent). To make sure you
get it, here it is again:

We have observed strange behaviour of the type checker when using
functors.

The following code does not compile:

module FF(X : sig end) =
struct
type t
end

module M =
struct
module X = struct end
module Y = FF (X) (* XXX *)
type t = Y.t
end

module F
(Y : sig type t end)
(M : sig type t = Y.t end) =
struct
end

module N = F (M.Y) (M)

The error is:

Signature mismatch:
Modules do not match:
sig
module X : sig end
module Y : sig type t = FF(X).t end
type t = Y.t
end
is not included in
sig type t = M.Y.t end
Type declarations do not match:
type t = Y.t
is not included in
type t = M.Y.t

However, if we replace the line marked with "XXX" as follows (i.e.
expand the definition of the argument "X"):

module Y = FF (struct end)

then the code compiles without problems. Are we overlooking a trivial
reason why the first code should be incorrect?

Our compiler version is 3.08.2.

Best regards,
Markus

--
Markus Mottl mmottl@janestcapital.com