{"ast_node_type":"variable","tokens":[{"end":57,"kind":"keyword","start":0,"text":"let"}]}
                let item = tcx.hir_expect_item(impl_did);
            } else if diff_fields.len() > 1 {
                let span = if let ItemKind::Impl(hir::Impl { of_trait: Some(t), .. }) = &item.kind {