Properly conjugate 'arguments' when more than 1 is allowed

src/builtin/macros.rs

@@ -28,7 +28,11 @@ macro_rules! decl {
 macro_rules! max_args {
     ($args:ident, $count:literal) => {
         if $args.len() > $count {
+            if $count > 1 {
+                return Err(format!("Only {} arguments allowed, but {} were passed.", $count, $args.len()).into());
+            } else {
                 return Err(format!("Only {} argument allowed, but {} were passed.", $count, $args.len()).into());
             }
+        }
     };
 }