Add a test to ensure that we round-trip literals faithfully
diff --git a/src/lib.rs b/src/lib.rs
index 55f93ef..aa02643 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -136,6 +136,7 @@
         Ident,
         WhereClause,
         Ty,
+        Lit,
     }
 
     #[cfg(feature = "full")]