On Mon, Jul 23, 2012 at 2:43 PM, David Nadlinger <s...@klickverbot.at> wrote: [getting subclasses] > You can't do that without breaking the module system – as long as a class is > not final (and then it doesn't make much sense to ask for its subclasses > anyway), somebody can always extend it in a module completely separate from > the code making the query. > > To illustrate what I mean, let's assume you define a class Foo in a module > A. The user imports A from a second module B, and potentially extends Foo > there. Now, if it was possible to get all possible subclasses in A, this > would lead to information leaking from B to A, while the import graph only > allows the other direction. As a consequence, all kinds of issues related to > order dependence, separate compilation, etc. would arise.
Yes, I know. That would be a purely local question: from module A, what subclasses of class Foo do I see? Anyway, maybe I'm warped by CLOS.