syntax_data: {"ast_node_type":"variable","tokens":[{"end":69,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:             let head: Vec<_> = head.iter().map(pat_to_str).collect();
context_before:         [head @ .., tail] if head.len() < LIMIT => {
context_after:             format!("`{}` and `{}`", head.join("`, `"), cx.print_witness_pat(tail))