{"ast_node_type":"function","tokens":[{"end":100,"kind":"keyword","start":0,"text":"fn"}]}
    fn with_current_self_item<T>(&mut self, self_item: &Item, f: impl FnOnce(&mut Self) -> T) -> T {
        let previous_value = replace(&mut self.diag_metadata.current_self_item, Some(self_item.id));