syntax_data: {"ast_node_type":"variable","tokens":[{"end":66,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let (idx, is_new) = inner.byte_strs.insert_full(byte_str);
context_before:         // #91445 for details.
context_after:         debug_assert!(is_new); // due to the get_index_of check above