syntax_data: {"ast_node_type":"other","tokens":[{"end":77,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:                         // FIXME(eddyb) find something better to key this on,
context_before:                         // `extern crate` injected by default.
context_after:                         // or avoid ending up with `ExternCrateSource::Extern`,