syntax_data: {"ast_node_type":"other","tokens":[{"end":55,"kind":"keyword","start":0,"text":"push_inner::<I>(&mut"}]}
source_snippet:                 push_inner::<I>(&mut self.stack, next);
context_before:             if self.visited.insert(next) {
context_after:                 debug!("next: stack={:?}", self.stack);