{"ast_node_type":"function","tokens":[{"end":40,"kind":"keyword","start":0,"text":"fn"}]}
    fn parse_byref(&mut self) -> ByRef {
    /// Parses reference binding mode (`ref`, `ref mut`, or nothing).
        if self.eat_keyword(exp!(Ref)) { ByRef::Yes(self.parse_mutability()) } else { ByRef::No }