Comment 5 for bug 1130419

> We should perhaps add a test case too ...

Indeed. Polished a bit over mine and attached it now. All tests are happy with my patch, but they tend to be rather simple so I would have been more surprised if not.

Beware: The CompareProviders functoid the patch modifies isn't present for too long; I think I added it between P and Q. Might therefore be hard to backport this to P (could have the benefit of fixing other M-A corner cases though).