static EncodedJSValue JSC_HOST_CALL constructMap(ExecState* exec)
{
    // Until we have iterators we throw if we've been given
    // any arguments that could require us to throw.
    if (!exec->argument(0).isUndefinedOrNull())
        return JSValue::encode(throwTypeError(exec, ASCIILiteral("Map constructor does not accept arguments")));
    if (!exec->argument(1).isUndefined())
        return throwVMError(exec, createRangeError(exec, WTF::ASCIILiteral("Invalid comparator function")));

    JSGlobalObject* globalObject = asInternalFunction(exec->callee())->globalObject();
    Structure* mapStructure = globalObject->mapStructure();
    return JSValue::encode(JSMap::create(exec, mapStructure));
}
static EncodedJSValue JSC_HOST_CALL constructMap(ExecState* exec)
{
    JSValue prototype = JSValue();
    JSValue newTarget = exec->newTarget();

    if (newTarget != exec->callee())
        prototype = newTarget.get(exec, exec->propertyNames().prototype);

    JSGlobalObject* globalObject = asInternalFunction(exec->callee())->globalObject();
    Structure* mapStructure = Structure::createSubclassStructure(exec->vm(), globalObject->mapStructure(), prototype);
    JSMap* map = JSMap::create(exec, mapStructure);
    JSValue iterable = exec->argument(0);
    if (iterable.isUndefinedOrNull())
        return JSValue::encode(map);

    JSValue adderFunction = map->JSObject::get(exec, exec->propertyNames().set);
    if (exec->hadException())
        return JSValue::encode(jsUndefined());

    CallData adderFunctionCallData;
    CallType adderFunctionCallType = getCallData(adderFunction, adderFunctionCallData);
    if (adderFunctionCallType == CallTypeNone)
        return JSValue::encode(throwTypeError(exec));

    JSValue iteratorFunction = iterable.get(exec, exec->propertyNames().iteratorSymbol);
    if (exec->hadException())
        return JSValue::encode(jsUndefined());

    CallData iteratorFunctionCallData;
    CallType iteratorFunctionCallType = getCallData(iteratorFunction, iteratorFunctionCallData);
    if (iteratorFunctionCallType == CallTypeNone)
        return JSValue::encode(throwTypeError(exec));

    ArgList iteratorFunctionArguments;
    JSValue iterator = call(exec, iteratorFunction, iteratorFunctionCallType, iteratorFunctionCallData, iterable, iteratorFunctionArguments);
    if (exec->hadException())
        return JSValue::encode(jsUndefined());

    if (!iterator.isObject())
        return JSValue::encode(throwTypeError(exec));

    while (true) {
        JSValue next = iteratorStep(exec, iterator);
        if (exec->hadException())
            return JSValue::encode(jsUndefined());

        if (next.isFalse())
            return JSValue::encode(map);

        JSValue nextItem = iteratorValue(exec, next);
        if (exec->hadException())
            return JSValue::encode(jsUndefined());

        if (!nextItem.isObject()) {
            throwTypeError(exec);
            iteratorClose(exec, iterator);
            return JSValue::encode(jsUndefined());
        }

        JSValue key = nextItem.get(exec, 0);
        if (exec->hadException()) {
            iteratorClose(exec, iterator);
            return JSValue::encode(jsUndefined());
        }

        JSValue value = nextItem.get(exec, 1);
        if (exec->hadException()) {
            iteratorClose(exec, iterator);
            return JSValue::encode(jsUndefined());
        }

        MarkedArgumentBuffer arguments;
        arguments.append(key);
        arguments.append(value);
        call(exec, adderFunction, adderFunctionCallType, adderFunctionCallData, map, arguments);
        if (exec->hadException()) {
            iteratorClose(exec, iterator);
            return JSValue::encode(jsUndefined());
        }
    }
    RELEASE_ASSERT_NOT_REACHED();
    return JSValue::encode(map);
}