src/third_party/mozjs-45/js/src/jit-test/tests/basic/testIncElem4.js

var counter = 0;
var x = { toString: function() { counter++; } };
var y = {};

for (var i = 0; i < 50; i++)
  ++y[x];

// :FIXME: bug 672076
//assertEq(counter, 50);