> This was an easy way to say that the polymorphism of m was not captured by 'a. I don't want to abuse your time, but if
> you have a tiny example illustrating when this automatic promotion is indeed useful, I'd be curious to see it. In any
> case, many thanks for the fix, which I'll use right away.

I think that the automatic promotion is just for convenience to avoid
writing "'a . ..." on lots of methods. Your example should probably be
considered a bug since the promotion should really only happen when the
method type is genuinely polymorphic, but I don't know how easy it is to
fix.

Regards,

Leo