syntax_data: {"ast_node_type":"variable","tokens":[{"end":79,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:             let diff_iter = lines.array_windows().map(|&[fst, snd]| snd - fst);
context_before:             // Encode the difference list.
context_after:             let num_diffs = lines.len() - 1;