Emit standalone lens pairs for nested record composition

rewrite.ml

@@ -41,7 +41,8 @@ let generate declaration =
               [Nolabel, Exp.field ~loc source (ident ~loc name)]))) in
     List.map (fun (name, body) ->
       Str.value ~loc Nonrecursive [Vb.mk ~loc (variable ~loc name) body])
-      [name, getter; "set_" ^ name, setter; "update_" ^ name, updater]) fields)
+      [name, getter; "set_" ^ name, setter; "update_" ^ name, updater;
+       "_" ^ name, Exp.tuple ~loc [getter; setter]]) fields)
 
 let structure mapper items =
   List.concat (List.map (fun item ->