{"ast_node_type":"variable","tokens":[{"end":69,"kind":"keyword","start":0,"text":"let"}]}
    let snippet = cx.sess().source_map().span_to_snippet(span).ok()?;
fn find_delimiters(cx: &LateContext<'_>, span: Span) -> Option<(Span, Span, char)> {
    let (open, open_ch) = snippet.char_indices().find(|&(_, c)| "([{".contains(c))?;