syntax_data: {"ast_node_type":"variable","tokens":[{"end":54,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                 let mut label = MultiSpan::from(span);
context_before:                     format!("this matches on type `{}_`", def_br_mutbl.ref_prefix_str());
context_after:                 label.push_span_label(span, label_msg);