Clippy and warning clean-ups.

src/syntax.rs

@@ -6,7 +6,7 @@ mod location;
 mod simplify;
 mod tokens;
 lalrpop_mod!(
-    #[allow(clippy::just_underscores_and_digits)]
+    #[allow(clippy::just_underscores_and_digits, clippy::clone_on_copy)]
     parser,
     "/syntax/parser.rs"
 );