0005143: module types and type constraints - MantisBT

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ID

Project

Category

View Status

Date Submitted

Last Update

0005143

OCaml

OCaml general

public

2010-09-03 11:25

2013-04-23 02:52

Reporter

montagu

Assigned To

garrigue

Priority

normal

Severity

minor

Reproducibility

always

Status

assigned

Resolution

open

Platform

OS

OS Version

Product Version

3.12.0

Target Version

4.01.0+dev

Fixed in Version

Summary

0005143: module types and type constraints

Description

Type constraints are not stable under equivalence of module types.

Additional Information

module type S1 = sig
  type t
  type u = t
end

module type S2 = sig
  type u
  type t = u
end

(* S1 and S2 are equivalent signatures, ie. S1 is included in S2 and S2 is included in S1 *)

module type S1' = S1 with type t = int
(* ok *)

module type S2' = S2 with type t = int
(* fails *)

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Notes
(0005651) garrigue (manager) 2010-09-05 02:20	I'm afraid this is not a bug. Namely, two module types can mutually convertible without being equal. The specification of constraints is to replace the current manifest type with a new one. If the current manifest type was necessary, this is bound to break something. You can always write: module type S2' = S2 with type t = int and type u = int

(0005652) montagu (reporter) 2010-09-05 11:17	No: in 3.12, module type S2' = S2 with type t = int and type u = int fails, whereas module type S2' = S2 with type u = int and type t = int is accepted.

(0009190) garrigue (manager) 2013-04-23 02:52	Indeed, but I would rather say that the problem is that the order of with constraints is relevant. Changing this behavior would require changing the algorithm for with constraints, which I believe is part of the specification.

Issue History
Date Modified	Username	Field	Change
2010-09-03 11:25	montagu	New Issue
2010-09-05 02:20	garrigue	Note Added: 0005651
2010-09-05 11:17	montagu	Note Added: 0005652
2011-05-20 17:47	doligez	Status	new => acknowledged
2012-06-01 09:26	garrigue	Assigned To	=> garrigue
2012-06-01 09:26	garrigue	Status	acknowledged => assigned
2012-07-10 18:30	doligez	Target Version	=> 4.01.0+dev
2012-07-31 13:36	doligez	Target Version	4.01.0+dev => 4.00.1+dev
2012-09-19 14:07	doligez	Target Version	4.00.1+dev => 4.01.0+dev
2013-04-23 02:52	garrigue	Note Added: 0009190

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