It's possible the changes do change the concrete return type in 2.12 too,
though no API interface types should change. I recall that because 2.13
makes WrappedArray a typedef (not gone, actually) I believe some code had
to change that expected it, to make it work on 2.12 and 2.13. Apps
shouldn't de
i rebuild master for Spark 2.12 and i see it also uses List instead of
WrappedArray. so the change is in master (compared to 3.0.1) and it is not
limited to Scala 2.13.
this might impact user programs somewhat? List has different performance
characteristics than WrappedArray... for starters it is n
Scala 2.13 changed the typedef of Seq to an immutable.Seq, yes. So lots of
things will now return an immutable Seq. Almost all code doesn't care what
Seq it returns and we didn't change any of that in the code, so, this is
just what we're getting as a 'default' from whatever operations produce the
