test/mjsunit/regress/regress-convert-transition.js

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var input = '{ "a1":1, "a2":1, "a3":1, "a4":1, "a5":1, "a6":1, "a7":1,\
               "a8":1, "a9":1, "a10":1, "a11":1, "a12":1, "a13":1}';
var a = JSON.parse(input);
a.a = function() { return 10; };

// Force conversion of field to slow mode.
var b = JSON.parse(input);
b.a = 10;

// Add another property to the object that would transition to a.
var c = JSON.parse(input);
c.x = 10;
assertEquals(undefined, c.a);