src/v8/src/builtins/proxy-is-extensible.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-isextensible
  // https://tc39.github.io/ecma262/#sec-proxy-object-internal-methods-and-internal-slots-isextensible
  transitioning builtin ProxyIsExtensible(implicit context:
                                              Context)(proxy: JSProxy): Object {
    PerformStackCheck();
    const kTrapName: constexpr string = 'isExtensible';
    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, "isExtensible").
      // 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 = ToBoolean(Call(context, trap, handler, target));

      // 8. Let targetResult be ? IsExtensible(target).
      const targetResult: bool = ToBoolean(object::ObjectIsExtensible(target));

      // 9. If SameValue(booleanTrapResult, targetResult) is false, throw a
      // TypeError exception.
      if (trapResult != targetResult) {
        ThrowTypeError(
            kProxyIsExtensibleInconsistent,
            SelectBooleanConstant(targetResult));
      }
      // 10. Return booleanTrapResult.
      return SelectBooleanConstant(trapResult);
    }
    label TrapUndefined(target: Object) {
      // 6.a. Return ? IsExtensible(target).
      return object::ObjectIsExtensible(target);
    }
    label ThrowProxyHandlerRevoked deferred {
      ThrowTypeError(kProxyRevoked, kTrapName);
    }
  }
}