text: // Copyright (C) 2015 the V8 project authors. All rights reserved.
  // This code is governed by the BSD license found in the LICENSE file.
  /*---
  es6id: 9.5.4
  description: >
      Throws a TypeError exception if boolean trap result is true and target is
      extensible.
  info: |
      [[PreventExtensions]] ( )
  
      ...
      10. If booleanTrapResult is true, then
          ...
          c. If targetIsExtensible is true, throw a TypeError exception.
      11. Return booleanTrapResult.
      ...
  features: [Proxy]
  ---*/
  
  var p = new Proxy({}, {
    preventExtensions: function(t) {
      return true;
    }
  });
  
  assert.throws(TypeError, function() {
    Object.preventExtensions(p);
  });
  