Issue MergeError exception for double def situations

When finding two symbols in the same class that have the same signature
as seen from some prefix, issue a merge error.

This is simpler and more robust than the alternative of producing an overloaded
denotation and dealing with it afterwards.

1 files changed, 17 insertions, 0 deletions

diff --git a/tests/neg/i1240a.scala b/tests/neg/i1240a.scala
new file mode 100644
index 000000000..dc711454e
--- /dev/null
+++ b/tests/neg/i1240a.scala
@@ -0,0 +1,17 @@
+
+// more complicated example
+abstract class A {
+  type C[X]
+  def foo[B](x: C[B]): C[B]       = {println("A.C"); x}
+  def foo[B](x: List[B]): List[B] = {println("A.List"); x}
+  def give[X]: C[X]
+}
+
+class B extends A {
+  type C[X] = List[X]
+  override def give[X] = Nil
+  override def foo[B](x: C[B]): C[B] =  {println("B.C"); x} // error: merge error during erasure
+  val a: A = this
+  a.foo(a.give[Int]) // what method should be called here in runtime?
+}
+