{"ast_node_type":"function","tokens":[{"end":54,"kind":"keyword","start":0,"text":"fn"}]}
    fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) {
impl<'tcx> Visitor<'tcx> for CollectLitsVisitor<'tcx> {
        if let hir::ExprKind::Lit(_) = expr.kind {