syntax_data: {"ast_node_type":"other","tokens":[{"end":79,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:                         // or avoid ending up with `ExternCrateSource::Extern`,
context_before:                         // FIXME(eddyb) find something better to key this on,
context_after:                         // for the injected `std`/`core`.