1 files changed, 17 insertions, 0 deletions
diff --git a/test/files/pos/t0904.scala b/test/files/pos/t0904.scala
new file mode 100644
index 0000000000..28ad30fc2d
--- /dev/null
+++ b/test/files/pos/t0904.scala
@@ -0,0 +1,17 @@
+trait A {
+  def apply(x: Int): Int
+  def update(x: Int, y: Int): Unit
+}
+
+trait B extends A
+
+abstract class Foo {
+  val a: A = null
+  val b: B = null
+
+  a(0) = 1
+  b(0) = 1
+
+  a(0) += 1
+  b(0) += 1 // this one does not type check.
+}