deps/v8/src/js/promise.js
function PromiseHasUserDefinedRejectHandlerCheck(handler, deferred) {
  if (handler !== PromiseIdRejectHandler) {
    var combinedDeferred = GET_PRIVATE(handler, promiseCombinedDeferredSymbol);
    if (IS_UNDEFINED(combinedDeferred)) return true;
    if (PromiseHasUserDefinedRejectHandlerRecursive(combinedDeferred.promise)) {
      return true;
    }
  } else if (PromiseHasUserDefinedRejectHandlerRecursive(deferred.promise)) {
    return true;
  }
  return false;
}
function PromiseHasUserDefinedRejectHandlerCheck(handler, deferred) {
  if (handler !== PromiseIdRejectHandler) {
    var combinedDeferred = GET_PRIVATE(handler, promiseCombinedDeferredSymbol);
    if (IS_UNDEFINED(combinedDeferred)) return true;
    if (PromiseHasUserDefinedRejectHandlerRecursive(combinedDeferred.promise)) {
      return true;
    }
  } else if (PromiseHasUserDefinedRejectHandlerRecursive(deferred.promise)) {
    return true;
  }
  return false;
}
Utility for debugger