src/v8/test/mjsunit/regress/readonly1.js

// Copyright 2013 the V8 project authors. All rights reserved.
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// modification, are permitted provided that the following conditions are
// met:
//
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function s(v) {
  v.x = 1;
}

function s_strict(v) {
  "use strict";
  v.x = 1;
}

function c(p) {
  return {__proto__: p};
}

var p = {};

var o1 = c(p);
var o2 = c(p);
var o3 = c(p);
var o4 = c(p);

// Make p go slow.
// Do this after using p as prototype, since using an object as prototype kicks
// it back into fast mode.
p.y = 1;
delete p.y;
p.x = 5;

// Initialize the store IC.
s(o1);
s(o2);
s_strict(o1);
s_strict(o2);

// Make x non-writable.
Object.defineProperty(p, "x", { writable: false });

// Verify that direct setting fails.
o3.x = 20;
assertEquals(5, o3.x);

// Verify that setting through the IC fails.
s(o4);
assertEquals(5, o4.x);
assertThrows("s_strict(o4);", TypeError);