IdentityObject & abstract superclasses

[Dan Smith]

> On Aug 20, 2020, at 4:25 PM, Brian Goetz <brian.goetz at oracle.com> wrote:
> 
> One degree of freedom that you've omitted, which might help you wiggle out of some of the uncomfortable corners, is warning-now-error-later.  
> 
> Your "I like, but might be disruptive" approach is to error on the cases where it is not super clear.  But by starting with a warning, errors like the ~10 in java.base would have some time to explicitly say `implements IdObject` without it seeming like a world-breaking change.

True. We're stuck waiting for IdentityObject before those warnings can be implemented, so we have to design for a world without any preparatory warnings first, but a few iterations down the road we could dial down inference and dial up error checks.