syntax_data: {"ast_node_type":"other","tokens":[{"end":73,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:         // If this is the first ExpnData with a given hash, then keep our
context_before:     let disambiguator = HygieneData::with(|data| {
context_after:         // disambiguator at 0 (the default u32 value)