syntax_data: {"ast_node_type":"other","tokens":[{"end":73,"kind":"keyword","start":0,"text":"(ExternCrateSource::Extern(def_id),"}]}
source_snippet:                     (ExternCrateSource::Extern(def_id), LOCAL_CRATE) => {
context_before:                 Some(&ExternCrate { src, dependency_of, span, .. }) => match (src, dependency_of) {
context_after:                         // NOTE(eddyb) the only reason `span` might be dummy,