Add negative test in macro-braces-dot-question.rs.

Author: m-ou-se

src/test/ui/parser/macro-braces-dot-question.rs

@@ -5,5 +5,7 @@ use std::io::Write;
 fn main() -> Result<(), std::io::Error> {
     vec! { 1, 2, 3 }.len();
     write! { vec![], "" }?;
+    println!{""}
+    [0]; // separate statement, not indexing into the result of println.
     Ok(())
 }