Better handling of merge errors

Instead of picking one at random, throw a MergeError
which might be caught later in mergeDenot. MergeDenot
has enough info to pick a simulate Scala2 linarization
if the prefix comes from Scala2, or it rethrows the
exception so that it becomes a type error.

1 files changed, 7 insertions, 0 deletions

diff --git a/tests/neg/i827.scala b/tests/neg/i827.scala
new file mode 100644
index 000000000..cc795b590
--- /dev/null
+++ b/tests/neg/i827.scala
@@ -0,0 +1,7 @@
+trait A { trait Inner }
+trait B { self: A =>
+  trait Inner extends self.Inner
+}
+
+
+class C extends C