Full error message is:
Attribute body is never executed because the type of the attribute is self-initializing (i.e. expanded or detachable).
This is a warning, not an error.
The only class that can benefit from an attribute body is a Void-safe class.
For expanded or detachable, a mere warning doesn't seem sufficient.
The source code is ignored. That should not be standard procedure.
What do the rest of you think about this?
Is there a preference to make this a full blown error?
How to configure that preference?