SI-4859 Don't rewrite CC().CC2() to new CC2

Where CC and CC2 are case classes. Attempting to do so leads to
a "no legal prefix" error.

Now, we restrict this optimization (living in RefChecks ?!) to
case class applies with a "safe to inline" qualifier.

1 files changed, 2 insertions, 0 deletions

diff --git a/test/pending/pos/t4859.scala b/test/files/pos/t4859.scala
index ec5abd966d..284a39b7ab 100644
--- a/test/pending/pos/t4859.scala
+++ b/test/files/pos/t4859.scala
@@ -1,5 +1,7 @@
 object O {
+  // error: C is not a legal prefix for a constructor
   C().CC()
+  // but this works.
   D().DD()
 }