proxy-get-prototype-of.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
  ProxyGetPrototypeOf(implicit context: Context)(proxy: JSProxy): Object {
    PerformStackCheck();
    const kTrapName: constexpr string = 'getPrototypeOf';
    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, "getPrototypeOf").
      // 6. If trap is undefined, then (see 6.a below).
      const trap: Callable = GetMethod(handler, kTrapName)
          otherwise goto TrapUndefined(target);

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

      // 8. If Type(handlerProto) is neither Object nor Null, throw a TypeError
      // exception.
      if (!Is<JSReceiver>(handlerProto) && handlerProto != Null) {
        goto ThrowProxyGetPrototypeOfInvalid;
      }

      // 9. Let extensibleTarget be ? IsExtensible(target).
      // 10. If extensibleTarget is true, return handlerProto.
      const extensibleTarget: Object = object::ObjectIsExtensible(target);
      assert(extensibleTarget == True || extensibleTarget == False);
      if (extensibleTarget == True) {
        return handlerProto;
      }

      // 11. Let targetProto be ? target.[[GetPrototypeOf]]().
      const targetProto = object::ObjectGetPrototypeOf(target);

      // 12. If SameValue(handlerProto, targetProto) is false, throw a TypeError
      // exception.
      // 13. Return handlerProto.
      if (BranchIfSameValue(targetProto, handlerProto)) {
        return handlerProto;
      }
      ThrowTypeError(kProxyGetPrototypeOfNonExtensible);
    }
    label TrapUndefined(target: Object) {
      // 6.a. Return ? target.[[GetPrototypeOf]]().
      return object::ObjectGetPrototypeOf(target);
    }
    label ThrowProxyHandlerRevoked deferred {
      ThrowTypeError(kProxyRevoked, kTrapName);
    }
    label ThrowProxyGetPrototypeOfInvalid deferred {
      ThrowTypeError(kProxyGetPrototypeOfInvalid);
    }
  }
}