Turns out it was just a lifetime issue.

src/renderer/renderer.rs

@@ -88,7 +88,7 @@ impl<'a> DustRenderer<'a> {
     }
 
     fn new_breadcrumbs_partial<'b>(
-        &self,
+        &'b self,
         maybe_breadcrumbs: Option<&'b BreadcrumbTree>,
         explicit_context_maybe_breadcrumbs: Option<&'b BreadcrumbTree>,
         injected_context: Option<&'b dyn IntoContextElement>,
@@ -139,7 +139,7 @@ impl<'a> DustRenderer<'a> {
                 });
         });
 
-        None
+        Some((parent, new_nodes))
     }
 
     /// Returns a Breadcrumb tree where all the bottom nodes that do