I think I solved the clone issue by manually implementing clone since the Rc needs to be cloned, not the content inside it.

src/parser/list.rs

@@ -1,10 +1,18 @@
 use std::rc::Rc;
 
-#[derive(Debug, Clone)]
+#[derive(Debug)]
 pub struct List<T> {
     head: Option<Rc<Node<T>>>,
 }
 
+impl<T> Clone for List<T> {
+    fn clone(&self) -> Self {
+        List {
+            head: self.head.clone(),
+        }
+    }
+}
+
 #[derive(Debug, Clone)]
 pub struct Node<T> {
     data: T,
@@ -27,7 +35,7 @@ impl<T> List<T> {
 
     pub fn without_front(&self) -> List<T> {
         List {
-            head: self.head.as_ref().map(|node| node.parent.clone()).flatten()
+            head: self.head.as_ref().map(|node| node.parent.clone()).flatten(),
         }
     }