syntax_data: {"ast_node_type":"variable","tokens":[{"end":40,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let new_t = t.fold_with(folder);
context_before:     match iter.by_ref().enumerate().find_map(|(i, t)| {
context_after:         if new_t != t { Some((i, new_t)) } else { None }