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, 17 insertions, 0 deletions

diff --git a/test/files/pos/t4859.scala b/test/files/pos/t4859.scala
new file mode 100644
index 0000000000..284a39b7ab
--- /dev/null
+++ b/test/files/pos/t4859.scala
@@ -0,0 +1,17 @@
+object O {
+  // error: C is not a legal prefix for a constructor
+  C().CC()
+  // but this works.
+  D().DD()
+}
+
+case class C() {
+  case class CC()
+}
+
+case class D() {
+  class DD()
+  object DD {
+    def apply() = new DD()
+  }
+}