Incremental weakening of module aliases is not allowed

[vicuna]

Original bug ID: 6465
Reporter: @garrigue
Assigned to: @garrigue
Status: closed (set by @xavierleroy on 2016-12-07T10:47:11Z)
Resolution: fixed
Priority: normal
Severity: minor
Version: 4.02.0+dev
Target version: 4.02.2+dev / +rc1
Fixed in version: 4.03.0+dev / +beta1
Category: typing
Tags: patch

Bug description

Assuming:
module M = struct type t = A module B = struct type u = B end end;;

the following fails:
module P : sig type t = M.t = A module B = M.B end = M;;

wheras this works:
module P : sig type t = M.t = A module B = M.B end = struct include M end;;

Clearly one would expect the type of M to be a subtype of that of struct include M end.

File attachments

• strengthen_alias.diff

[vicuna]

Comment author: @garrigue

Added a preliminary patch, but it does not pass all tests yet (a problem with recursive modules).

[vicuna]

Comment author: @garrigue

Updated the patch. Now all tests in the typing testsuite go through.

[vicuna]

Comment author: @garrigue

Does the new target mean that I should merge the patch in the 4.02 branch now?
(Sorry, I've been busy with other things, and forgot to follow on this one...)

[vicuna]

Comment author: @garrigue

Merging will have to wait for later, as the current patch breaks camlp4.

[vicuna]

Comment author: @garrigue

Patch was merged in trunk at revision 15405.