{"ast_node_type":"variable","tokens":[{"end":78,"kind":"keyword","start":0,"text":"let"}]}
    let source_root = snap.analysis.source_root_id(runnable.nav.file_id).ok();
    let target_spec = TargetSpec::for_file(snap, runnable.nav.file_id)?;
    let config = snap.config.runnables(source_root);