Comma-separated predicates in simple CASE expressions (f263)

I was looking at F263 from the SQL standard, Comma-separated predicates in
simple CASE expression, and thinking if we could support this within the
framework we already have at a minimal added cost.  The attached sketch diff
turns each predicate in the list into a CaseWhen node and uses the location
from parsing for grouping in errorhandling for searched case.

Is this a viable approach or am I missing something obvious?

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Daniel Gustafsson        https://vmware.com/