Behavior of groupBy().mapValues() differs in Scala 2.12 vs Scala 2.13

It’s a pity that this was not changed in Scala 3. Since moving from Scala 2.13 to 3.0 is some work after all, this would have not added much. (There are a few more of these cases, if i remember correctly). In Scala 3.1.3 i still get this warning.