0005036: 3.12.0+dev18: "module type of" leaves weak polymorphic types in module type - MantisBT

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ID

Project

Category

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Date Submitted

Last Update

0005036

OCaml

OCaml general

public

2010-04-24 06:23

2010-04-30 07:13

Reporter

kaustuv

Assigned To

Priority

normal

Severity

minor

Reproducibility

always

Status

closed

Resolution

fixed

Platform

OS

OS Version

Product Version

Target Version

Fixed in Version

3.12.0+dev

Summary

0005036: 3.12.0+dev18: "module type of" leaves weak polymorphic types in module type

Description

   # module type S =
       module type of (struct
                        let f = (fun x -> x) (fun x -> x)
                       end) ;;
   module type S = sig val f : '_a -> '_a end

Light experimentation suggests that only modules that define a value f : 'a. 'a -> 'a will ascribe to the above signature, so "module type of" should promote weak polymorphic types to strong polymorphic types.

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Notes
(0005398) xleroy (administrator) 2010-04-28 10:13	I'm not comfortable with generalizing these type variables automatically. Added a check to reject "module type of M" if "M" contains nongeneralized type variables.

(0005399) kaustuv (reporter) 2010-04-28 11:23	Many apologies for reopening this with a trivial nitpick, but you got the test for closedness and the simplification (PR#5037) in the wrong order in typing/typemod.ml/type_module_type_of. Witness this startling result: # module M = struct let f = (fun x -> x) (fun x -> x) let f x = x end ;; module M : sig val f : 'a -> 'a end # module type S = module type of M ;; Error: The type of this module, sig val f : '_a -> '_a val f : 'a -> 'a end, contains type variables that cannot be generalized

(0005424) garrigue (manager) 2010-04-30 07:13	Indeed, type_implementation was doing it in the opposite order. Fixed in revision 10330.

Issue History
Date Modified	Username	Field	Change
2010-04-24 06:23	kaustuv	New Issue
2010-04-28 10:13	xleroy	Note Added: 0005398
2010-04-28 10:13	xleroy	Status	new => closed
2010-04-28 10:13	xleroy	Resolution	open => fixed
2010-04-28 11:23	kaustuv	Note Added: 0005399
2010-04-28 11:23	kaustuv	Status	closed => feedback
2010-04-28 11:23	kaustuv	Resolution	fixed => reopened
2010-04-30 07:13	garrigue	Note Added: 0005424
2010-04-30 07:13	garrigue	Status	feedback => closed
2010-04-30 07:13	garrigue	Resolution	reopened => fixed
2010-04-30 07:13	garrigue	Fixed in Version	=> 3.12.0+dev

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