fix clippy lints

src/lib.rs

@@ -1,5 +1,5 @@
 #![deny(clippy::pedantic, unused_imports)]
-#![allow(dead_code, unstable_name_collisions)]
+#![allow(dead_code, unstable_name_collisions, clippy::missing_errors_doc)]
 #![feature(impl_trait_in_assoc_type)]
 
 use mon::{Parser, input::Input};