{"ast_node_type":"function","tokens":[{"end":96,"kind":"keyword","start":0,"text":"fn"}]}
    fn parse_expr_while(&mut self, opt_label: Option<Label>, lo: Span) -> PResult<'a, P<Expr>> {
    /// Parses a `while` or `while let` expression (`while` token already eaten).
        let policy = LetChainsPolicy::EditionDependent { current_edition: lo.edition() };