syntax_data: {"ast_node_type":"variable","tokens":[{"end":62,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:     let macro_backtrace = sopts.unstable_opts.macro_backtrace;
context_before: ) -> Box<DynEmitter> {
context_after:     let track_diagnostics = sopts.unstable_opts.track_diagnostics;