syntax_data: {"ast_node_type":"other","tokens":[{"end":83,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:         // a couple "fast path" cases to avoid traversing parents in the loop below
context_before:     fn is_descendant_of(&self, mut expn_id: ExpnId, ancestor: ExpnId) -> bool {
context_after:         if ancestor == ExpnId::root() {