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): JSAny {
  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 (ToBoolean(trapResult)) {
      const extensibleTarget: JSAny = object::ObjectIsExtensibleImpl(target);
      assert(extensibleTarget == True || extensibleTarget == False);
      if (extensibleTarget == True) {
        ThrowTypeError(MessageTemplate::kProxyPreventExtensionsExtensible);
      }
    } else {
      if (doThrow == True) {
        ThrowTypeError(MessageTemplate::kProxyTrapReturnedFalsish, kTrapName);
      }
      return False;
    }

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