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 // String.prototype.iterator is generic.

 load(libdir + "asserts.js");

 load(libdir + "iteration.js");

 load(libdir + "string.js");

 function test(obj) {

     var it = String.prototype[std_iterator].call(obj);

     var s = String(obj);

     for (var i = 0, length = s.length; i < length;) {

         var r = s[i++];

         if (isHighSurrogate(r) && i < length && isLowSurrogate(s[i])) {

             r += s[i++];

         }

         assertIteratorNext(it, r);

     }

     assertIteratorDone(it, undefined);

 }

 test({toString: () => ""});

 test({toString: () => "xyz"});

 test({toString: () => "\ud808\udf45"});

 test({valueOf: () => ""});

 test({valueOf: () => "xyz"});

 test({valueOf: () => "\ud808\udf45"});