??= operator

Dear internals, Remember ??=, was accepted with 37/4 votes? Since then I did not have time to implement the ??= because I did not have time Hence I am currently unemployed and continuously passing tech interviews and failing non-technical 2. rounds, I have plenty of time, so I decided to going back to implementations. Sometime ago I got ?:= implementation from @saramg, for cheating but I see that it was not implemented due to edge cases. I think I missed some discussion for a while, so I am unaware of the cases. Was there a decision about it? Or should I give up trying to implement this? Thank you very much, Midori P.S: Sorry for English mistakes if there are.