I think I need to make into_context_element return an Option.

The reason is, missing values for paths are not equal to null so I can't use an OwnedLiteral unless I create a special "walking failed" OwnedLiteral.

src/renderer/parameters_context.rs

@@ -37,7 +37,11 @@ impl<'a> IntoContextElement for RValue<'a> {
         renderer: &DustRenderer,
         breadcrumbs: Option<&BreadcrumbTree>,
     ) -> &dyn ContextElement {
-        todo!()
+        match self {
+            RValue::RVLiteral(owned_literal) => owned_literal,
+            RValue::RVPath(path) => todo!(),
+            RValue::RVTemplate(template) => todo!(),
+        }
     }
 }