Test even deeper nested indexing

Author: dtolnay

src/test/ui/tuple/nested-index.rs

@@ -3,4 +3,7 @@
 fn main () {
     let n = (1, (2, 3)).1.1;
     assert_eq!(n, 3);
+
+    let n = (1, (2, (3, 4))).1.1.1;
+    assert_eq!(n, 4);
 }