{"ast_node_type":"other","tokens":[{"end":62,"kind":"keyword","start":0,"text":"(NotNested(span),"}]}
            (NotNested(span), Some(NotNested(prev_span))) => {
        match (field_decl, self.seen_fields.get(&field_name).copied()) {
                self.tcx.dcx().emit_err(errors::FieldAlreadyDeclared::NotNested {