Fix warning about unused variables in reject!()
diff --git a/synom/src/lib.rs b/synom/src/lib.rs
index b92fe75..d3646f7 100644
--- a/synom/src/lib.rs
+++ b/synom/src/lib.rs
@@ -610,9 +610,10 @@
 /// ```
 #[macro_export]
 macro_rules! reject {
-    ($i:expr,) => {
+    ($i:expr,) => {{
+        let _ = $i;
         $crate::parse_error()
-    }
+    }}
 }
 
 /// Run a series of parsers and produce all of the results in a tuple.