Fix #3539: Add regression tests

Author: nicolasstucki

tests/pos/i3539.scala

@@ -0,0 +1,16 @@
+object Test {
+  def main(args: Array[String]): Unit = {
+    val i2s = (x: Int) => ""
+    assert(asInstanceOf.asInstanceOf[AnyRef => String].apply(null) == "")
+    val i2i = (x: Int) => x + 1
+    assert(i2i.asInstanceOf[AnyRef => Int].apply(null) == 1)
+  }
+}
+
+class Test {
+
+  asInstanceOf[Nothing].asInstanceOf[AnyRef => String]
+
+  asInstanceOf[Nothing].asInstanceOf[AnyRef => String].apply(null)
+
+}