add expected diag


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@60927 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Sema/exprs.c b/test/Sema/exprs.c
index 1b8e134..73d73eb 100644
--- a/test/Sema/exprs.c
+++ b/test/Sema/exprs.c
@@ -42,6 +42,6 @@
 // rdar://6095061
 int test8(void) {
   int i;
-  __builtin_choose_expr (0, 42, i) = 10;
+  __builtin_choose_expr (0, 42, i) = 10;  // expected-warning {{extension used}}
   return i;
 }