Fix #2112: Add regression test

Author: odersky

tests/pos/i2112.scala

@@ -0,0 +1,7 @@
+import scala.collection.JavaConverters._
+
+object Test {
+  def test(x: Any): Unit = {
+    x.asInstanceOf[java.util.List[_]].asScala.toList
+  }
+}