text: // Copyright (C) 2020 Alexey Shvayka. All rights reserved.
  // This code is governed by the BSD license found in the LICENSE file.
  
  /*---
  esid: sec-proxy-object-internal-methods-and-internal-slots-preventextensions
  description: >
    If "preventExtensions" trap is null or undefined, [[PreventExtensions]] call
    is properly forwarded to [[ProxyTarget]] (which is also a Proxy object).
  info: |
    [[PreventExtensions]] ( )
  
    [...]
    4. Let target be O.[[ProxyTarget]].
    5. Let trap be ? GetMethod(handler, "preventExtensions").
    6. If trap is undefined, then
      a. Return ? target.[[PreventExtensions]]().
  features: [Proxy]
  ---*/
  
  var plainObject = {};
  var plainObjectTarget = new Proxy(plainObject, {});
  var plainObjectProxy = new Proxy(plainObjectTarget, {
    preventExtensions: null,
  });
  
  Object.preventExtensions(plainObjectProxy);
  assert(!Object.isExtensible(plainObject));
  