syntax_data: {"ast_node_type":"variable","tokens":[{"end":64,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                 let from = u64::try_from(prefix.len()).unwrap();
context_before:             | PatKind::Slice { ref prefix, ref slice, ref suffix } => {
context_after:                 let to = u64::try_from(suffix.len()).unwrap();