Bug with cyclic abbreviations ?

Bug with cyclic abbreviations ?

[Julien Verlaguet]

This is a problem that I only have when the -rectypes option is activated.

$./ocaml -rectypes
         Objective Caml version 3.08.3

# type 'a t='a;;
type 'a t = 'a

# type cycle='a t as 'a;;
The type abbreviation cycle is cyclic

agreed.

# let (x : 'a t as 'a)=0;;
Fatal error: exception Stack_overflow

Shouldn't it detect the cyclic abbreviation in this case too ?

J

Re: [Caml-list] Bug with cyclic abbreviations ?

[Frédéric Gava]

Hi,

> # let (x : 'a t as 'a)=0;;
> Fatal error: exception Stack_overflow

I have the same problem with

let _ = (fun () -> let (x : 'a t as 'a)=0 in 0);;

where the evaluation of the let has been freezed... so is it the type system
which loops ?

Frédéric Gava

Re: [Caml-list] Bug with cyclic abbreviations ?

[Jacques Garrigue]

From: Julien Verlaguet <Julien.Verlaguet@pps.jussieu.fr>

> This is a problem that I only have when the -rectypes option is activated.
> 
> $./ocaml -rectypes
>          Objective Caml version 3.08.3
> 
> # type 'a t='a;;
> type 'a t = 'a
> 
> # type cycle='a t as 'a;;
> The type abbreviation cycle is cyclic
> 
> agreed.
> 
> # let (x : 'a t as 'a)=0;;
> Fatal error: exception Stack_overflow
> 
> Shouldn't it detect the cyclic abbreviation in this case too ?

Indeed, there was a bug in the occur check when using -rectypes.
I suppose this bug has always been there. Funny nobody found it
before.
This is now fixed in CVS (both 3.08 and 3.09).

By the way, there is a special address for bug reports. This helps
tracking them. (Fortunately this one was solved immediately.)

Jacques Garrigue