syntax_data: {"ast_node_type":"variable","tokens":[{"end":67,"kind":"keyword","start":0,"text":"while"}]}
source_snippet:             while let Some((expn_id, transparency)) = marks.pop() {
context_before:             let scope = marks.last().map(|mark| mark.0);
context_after:                 *self = data.apply_mark(*self, expn_id, transparency);