syntax_data: {"ast_node_type":"other","tokens":[{"end":63,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:         // a few "fast path" cases to avoid locking HygieneData
context_before:     pub fn is_descendant_of(self, ancestor: ExpnId) -> bool {
context_after:         if ancestor == ExpnId::root() || ancestor == self {