syntax_data: {"ast_node_type":"other","tokens":[{"end":92,"kind":"keyword","start":0,"text":"while"}]}
source_snippet:         while !self.latest_ctxts.lock().is_empty() || !self.latest_expns.lock().is_empty() {
context_before:         // a `SyntaxContext` that we haven't seen before
context_after:             debug!(