Re: Extension of non-limited type needs limited component

[michael.jackson5@virgin.net (Mike)]

I wrote

> > How do I extend a non-limited tagged type to add a limited component?

Jean-Pierre Rosen replied

> You can't. Make the original type limited.
> The whole hierarchy has to be limited (or not limited, excluding adding a
> limited element). The reason is that otherwise, you could end up trying to
> assign a variable with a limited component.

Unfortunately I can't make the base type limited as it is a generic
gui dialog base 'class'.

I understand that I would need to make the extended type limited to
avoid the possible assignment to the limited component, but I cannot
see why I should have to make the whole hierarchy limited.

How can assignment by upcasting the extended type possibly affect the
limited component?

Regards,

Mike