from preamble:

"Change Set:  RecompileUpdateCS-AFi
Date:   17 May 2001
Author:   Alain Fischer

Changing definition of a class force a compilation of the class
and the metaclass methods through Behavior>>recompile:from:
With the old method, the current ChangeSet is not updated which
could let some obsolete reference in the system causing problems
when you try to save a project.
The new method update the current ChangeSet in a way similar to
the one used when you accept change to a method in a code pane."