The problem is that JvmRecord has SOURCE retention
Probably, increasing its retention might be a more reliable solution
(or in some other way serializing that the class is a record)
Just checking supertypes seems like a reasonable approximation:
only records kotlin are allowed to extend j.l.Record.
But the relevant diagnostic has been added only since 1.4.30,
so potentially there could have been exist a non-record class with
such supertype compiled by 1.4.20, but this case seems to be ill-formed
and marginal anyway.
For Java classes, it's irrelevant since they don't have member properties
(only synthetic extensions)
^KT-43677 In Progress
Alexander Udalov