src/v8/src/builtins/proxy-prevent-extensions.tq

// Copyright 2019 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include 'src/builtins/builtins-proxy-gen.h'

namespace proxy {

  // ES #sec-proxy-object-internal-methods-and-internal-slots-preventextensions
  // https://tc39.es/ecma262/#sec-proxy-object-internal-methods-and-internal-slots-preventextensions
  transitioning builtin
  ProxyPreventExtensions(implicit context: Context)(
      proxy: JSProxy, doThrow: Boolean): Object {
    PerformStackCheck();
    const kTrapName: constexpr string = 'preventExtensions';
    try {
      // 1. Let handler be O.[[ProxyHandler]].
      // 2. If handler is null, throw a TypeError exception.
      // 3. Assert: Type(handler) is Object.
      assert(proxy.handler == Null || Is<JSReceiver>(proxy.handler));
      const handler =
          Cast<JSReceiver>(proxy.handler) otherwise ThrowProxyHandlerRevoked;

      // 4. Let target be O.[[ProxyTarget]].
      const target = proxy.target;

      // 5. Let trap be ? GetMethod(handler, "preventExtensions").
      // 6. If trap is undefined, then (see 6.a below).
      const trap: Callable = GetMethod(handler, kTrapName)
          otherwise goto TrapUndefined(target);

      // 7. Let booleanTrapResult be ToBoolean(? Call(trap, handler, «
      // target»)).
      const trapResult = Call(context, trap, handler, target);

      // 8. If booleanTrapResult is true, then
      //    8.a. Let extensibleTarget be ? IsExtensible(target).
      //    8.b If extensibleTarget is true, throw a TypeError exception.
      if (BranchIfToBooleanIsTrue(trapResult)) {
        const extensibleTarget: Object = object::ObjectIsExtensible(target);
        assert(extensibleTarget == True || extensibleTarget == False);
        if (extensibleTarget == True) {
          ThrowTypeError(kProxyPreventExtensionsExtensible);
        }
      } else {
        if (doThrow == True) {
          ThrowTypeError(kProxyTrapReturnedFalsish, kTrapName);
        }
        return False;
      }

      // 9. Return booleanTrapResult.
      return True;
    }
    label TrapUndefined(target: Object) {
      // 6.a. Return ? target.[[PreventExtensions]]().
      if (doThrow == True) {
        return object::ObjectPreventExtensionsThrow(target);
      }
      return object::ObjectPreventExtensionsDontThrow(target);
    }
    label ThrowProxyHandlerRevoked deferred {
      ThrowTypeError(kProxyRevoked, kTrapName);
    }
  }
}  // namespace proxy