在combineLatest到mapTo时得到错误

Question

export function handleAction(action$) {
    return combineLatest(
                    action$.ofType(actions.LAYOUT_READY),
                action$.ofType(actions.LOADING))
        .mapTo(lastViewedPending())
        .mergeMap((action)=> {
            return leadService.getLastPxls()
                .map(items => lastViewedSucceed(items))
                .startWith(action)
        });
}

我收到错误：

  TS2345: Argument of type 'LAST_VIEWED_PENDING' is not assignable to parameter of type 'IScheduler | LAST_VIEWED_SUCCESS'.

类型'LAST_VIEWED_PENDING'不能指定为'LAST_VIEWED_SUCCESS'类型。     “LAST_VIEWED_PENDING”类型中缺少属性“有效负载”。

我正在使用redux-observable