{"ast_node_type":"variable","tokens":[{"end":84,"kind":"keyword","start":0,"text":"let"}]}
                        let variant_dest = dest.project_downcast(bx, variant_index);
                    mir::AggregateKind::Adt(_, variant_index, _, _, active_field_index) => {
                        (variant_index, variant_dest, active_field_index)