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Ctype.Unify(_) with associated functor args containing open PV/obj. type and open obj. type. #6981

vicuna opened this issue Sep 7, 2015 · 2 comments


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@vicuna vicuna commented Sep 7, 2015

Original bug ID: 6981
Reporter: labichn
Assigned to: @garrigue
Status: closed (set by @xavierleroy on 2017-02-16T14:16:27Z)
Resolution: fixed
Priority: normal
Severity: crash
Platform: x86_64
OS: Arch GNU/Linux
OS Version: 4.1.6-1
Version: 4.02.3
Target version: 4.03.0+dev / +beta1
Fixed in version: 4.03.0+dev / +beta1
Category: typing
Related to: #6513
Monitored by: @hcarty

Bug description

See steps to reproduce for minimal example.

The bug occurs in a functor with two parameters, where the first module Bar contains a private row type (either PV or open object) and the second module contains a private, open object type that refers to any type inside of Bar (not just the private row type).

I'm unsure of what the behavior should be (found this during some refactoring with stale code), but I imagine it's not a unification error:

Fatal error: exception Ctype.Unify(_)

I was able to reproduce this error for all compiler versions 4.00.1 and above. In 3.12.1 the error is formatted slightly differently:

Fatal error: exception Ctype.Unify(_, _)

Steps to reproduce

module type S =
type a
type b
module Foo
(Bar : S with type a = private [> `A])
(Baz : S with type b = private < b : Bar.b ; .. >) =
Fatal error: exception Ctype.Unify(_)

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@vicuna vicuna commented Nov 27, 2015

Comment author: @alainfrisch

This is compiler crash -> bumping priority.

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@vicuna vicuna commented Nov 30, 2015

Comment author: @garrigue

Fixed in trunk by commit 20b59a3.

Same problem as #6513, but for structures. Should have been fixed then...

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