1 files changed, 23 insertions, 0 deletions
diff --git a/test/checker-tests/fail10.scala b/test/checker-tests/fail10.scala
new file mode 100644
index 0000000000..6d4e6c27c9
--- /dev/null
+++ b/test/checker-tests/fail10.scala
@@ -0,0 +1,23 @@
+class ClassCounts extends scala.collection.mutable.HashMap[Class[_], Int] { }
+
+class A {
+  def f(xs: ClassCounts) {
+    // ok
+    xs(getClass) = xs(getClass) + 1
+    // not ok
+    xs(getClass) += 1
+  }
+}
+
+// [Not checkable: parser]
+// [Not checkable: namer]
+// [Not checkable: packageobjects]
+// [Now checking: typer]
+// test/checker-tests/fail10.scala:8: error:
+// **** ERROR DURING INTERNAL CHECKING ****
+// type mismatch;
+//  found   : java.lang.Class[?0(in value ev$1)] where type ?0(in value ev$1)
+//  required: java.lang.Class[?0(in method f)] where type ?0(in method f)
+//     xs(getClass) += 1
+//        ^
+// one error found