Eng 6553 group by alias

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What happens if you try to use a tag inside the HAVING clause -- like to try to reference an agg expression in the SELECT clause?
I'd like to see a test case that shows that this either works (I doubt it) or gives a reasonable error message -- I hope -- ideally the same message you get if the name in the having clause is not defined anywhere at all, showing that the tag in the SELECT makes no difference to the HAVING clause. If the behavior is anything else, I would want to see more edge cases tested to verify that the new behavior is consistent for different definitions of the tag in the SELECT.