{"ast_node_type":"variable","tokens":[{"end":61,"kind":"keyword","start":0,"text":"let"}]}
    let _ = parser.by_ref().collect::<Vec<Piece<'static>>>();
    let mut parser = Parser::new(fmt, None, Some(fmt_pre.into()), false, ParseMode::Format);
    assert_eq!(parser.errors[0].span, 4..4);