Omitting unused this$0 as an optimaization?

[stephan-herrmann]

I've seen churn in javac:

• Originally https://bugs.openjdk.org/browse/JDK-8271623 implemented omission of unused this$0, in part to help avoid memory leaks via this invisible reference
• Then https://bugs.openjdk.org/browse/JDK-8277965 rowed back (to some degree) because the omission interacts with serialization - that was the status at Java 18
• Currently a change is under review, which under "Compatibility" discusses some similar/same bytecode stability issues.
• More discussion happening in the bug of that PR: https://bugs.openjdk.org/browse/JDK-8336492 which has several mentions of "unspecified".

@srikanth-sankaran do we have any similar optimization in place? For now we should probably just wait, what will be the conclusion for javac, and then decide if this calls for any action in ecj.