v8/test/mjsunit/indexed-accessors.js

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// Test that getters can be defined and called with an index as a parameter.

var o = {};
o.x = 42;
o.__defineGetter__('0', function() { return o.x; });
assertEquals(o.x, o[0]);
assertEquals(o.x, o.__lookupGetter__('0')());

o.__defineSetter__('0', function(y) { o.x = y; });
assertEquals(o.x, o[0]);
assertEquals(o.x, o.__lookupGetter__('0')());
o[0] = 21;
assertEquals(21, o.x);
o.__lookupSetter__(0)(7);
assertEquals(7, o.x);

function Pair(x, y) {
  this.x = x;
  this.y = y;
};
Pair.prototype.__defineGetter__('0', function() { return this.x; });
Pair.prototype.__defineGetter__('1', function() { return this.y; });
Pair.prototype.__defineSetter__('0', function(x) { this.x = x; });
Pair.prototype.__defineSetter__('1', function(y) { this.y = y; });

var p = new Pair(2, 3);
assertEquals(2, p[0]);
assertEquals(3, p[1]);
p.x = 7;
p[1] = 8;
assertEquals(7, p[0]);
assertEquals(7, p.x);
assertEquals(8, p[1]);
assertEquals(8, p.y);


// Testing that a defined getter doesn't get lost due to inline caching.
var expected = {};
var actual = {};
for (var i = 0; i < 10; i++) {
  expected[i] = actual[i] = i;
}
function testArray() {
  for (var i = 0; i < 10; i++) {
    assertEquals(expected[i], actual[i]);
  }
}
actual[1000000] = -1;
testArray();
testArray();
actual.__defineGetter__('0', function() { return expected[0]; });
expected[0] = 42;
testArray();
expected[0] = 111;
testArray();

// Using a setter where only a getter is defined throws an exception.
var q = {};
q.__defineGetter__('0', function() { return 42; });
assertThrows('q[0] = 7');

// Using a getter where only a setter is defined returns undefined.
var q1 = {};
q1.__defineSetter__('0', function() {q1.b = 17;});
assertEquals(q1[0], undefined);
// Setter works
q1[0] = 3;
assertEquals(q1[0], undefined);
assertEquals(q1.b, 17);

// Complex case of using an undefined getter.
// From http://code.google.com/p/v8/issues/detail?id=298
// Reported by nth10sd.

a = function() {};
__defineSetter__("0", function() {});
if (a |= '') {};
assertThrows('this[a].__parent__');
assertEquals(a, 0);
assertEquals(this[a], undefined);