{"ast_node_type":"other","tokens":[{"end":46,"kind":"keyword","start":0,"text":"///"}]}
    /// for now to provide a more useful error
    /// Parse `box expr` - this syntax has been removed, but we still parse this
    fn parse_expr_box(&mut self, box_kw: Span) -> PResult<'a, (Span, ExprKind)> {