Fixes SI-5201. Adds flatten to TraversableViewLike.

Note: This commit exposes a pretty rich type on flatten in views.  HOWEVER, because we don't
capture the higher kinded type of the underlying collection, it makes returning a more minimal type
pretty dang hard.  I can imagine a very breaking and painful change of capturing the underling
collection as a higher-kinded type as well as the current view type in a *ViewLike.scala.

I hope this kind of issue, along with others, drives a rethink of our view API design.

1 files changed, 5 insertions, 0 deletions

diff --git a/test/files/run/t5201.scala b/test/files/run/t5201.scala
new file mode 100644
index 0000000000..a371082797
--- /dev/null
+++ b/test/files/run/t5201.scala
@@ -0,0 +1,5 @@
+object Test extends App {
+  val seq = Seq(Seq(1, 2), Seq(3, 4)).view.flatten
+  
+  Console.println(seq.isInstanceOf[collection.SeqView[_,_]])
+}