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first class modules don't allow "with type" declarations for types in sub-modules #5358

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vicuna opened this issue Sep 20, 2011 · 3 comments

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commented Sep 20, 2011

Original bug ID: 5358
Reporter: yminsky
Assigned to: @alainfrisch
Status: closed (set by @xavierleroy on 2012-09-25T18:07:21Z)
Resolution: fixed
Priority: normal
Severity: minor
Version: 3.12.1
Fixed in version: 3.13.0+dev
Category: ~DO NOT USE (was: OCaml general)
Monitored by: sigonnea mehdi @jberdine @hcarty @Chris00

Bug description

For some reason, 1st-class modules have more restrictive "with" syntax, which turns out to be a practical problem.

The main constraint is that with constraints do not seem to be able to refer to sub-modules. Consider the following code snippet:

module type Foo = sig type t end
module type Bar = sig module Foo : Foo end

(* compiles *)
let g (type a) (m : (module Foo with type t = a)) = ()

(* fails to compile with a syntax error *)
let f (type a) (m : (module Bar with type Foo.t = a)) = ()

It would be nice to lift this restriction. (Also, allowing "with module" declarations would be good.)

Additional information

There's a thread discussing this initiated by this message:

https://sympa-roc.inria.fr/wws/arc/caml-list/2011-09/msg00158.html

with a useful explanation by Alain Frisch here:

https://sympa-roc.inria.fr/wws/arc/caml-list/2011-09/msg00162.html

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commented Dec 14, 2011

Comment author: @alainfrisch

Wish granted (commit 11311).

Camlp4 compiles but cannot parses the new feature.

TODO:

  • adapt the manual
  • adapt Camlp4
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commented Dec 16, 2011

Comment author: @diml

I updated Camlp4 (commit 11320).

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commented Dec 16, 2011

Comment author: @alainfrisch

Thanks Jérémie. I've updated the manual, so feel free to mark the issue as resolved if you're confident in the camlp4 update.

@vicuna vicuna closed this Sep 25, 2012

@vicuna vicuna added the bug label Mar 20, 2019

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