{"ast_node_type":"variable","tokens":[{"end":72,"kind":"keyword","start":0,"text":"let"}]}
    let pattern_str = tcx.sess.source_map().span_to_snippet(span).ok()?;
fn suggest_ref_mut(tcx: TyCtxt<'_>, span: Span) -> Option<Span> {
    if let Some(rest) = pattern_str.strip_prefix("ref")