syntax_data: {"ast_node_type":"function","tokens":[{"end":58,"kind":"keyword","start":0,"text":"fn"}]}
source_snippet:     fn push_opt_integer_62(&mut self, tag: &str, x: u64) {
context_before:     ///   e.g. `1` becomes `tag + "_"`, `2` becomes `tag + "0_"`, etc.
context_after:         if let Some(x) = x.checked_sub(1) {