On 10/18/2016 11:10 AM, Pierrick Couderc wrote:
> Hi,
> 
> It is supposed to work, but it seems thepattern-matching compiler does
> not detect that M0.to_string is non exhaustive, thus it does not add a
> Match_Failure in case the variant is unknown. With extensible variants,
> a pattern matching is only exhaustive if you provide a wildcard or a
> variable for variants added afterwards. 


Indeed, if I add a catch-all branch in M0.to_string then the code in
that branch is run, with no segfault.

But I guess my original idea of extending the type doesn't really work
as I hoped, since with nested expressions like that, I'd need to find a
way for M0.to_string to call back M1.to_string when a `T` is found.

Back to the drawing board...

Thanks,
Andre