exports.async = function()

in packages/runtime/runtime.js [229:242]


  exports.async = function(innerFn, outerFn, self, tryLocsList, PromiseImpl) {
    if (PromiseImpl === void 0) PromiseImpl = Promise;

    var iter = new AsyncIterator(
      wrap(innerFn, outerFn, self, tryLocsList),
      PromiseImpl
    );

    return exports.isGeneratorFunction(outerFn)
      ? iter // If outerFn is a generator, return the full iterator.
      : iter.next().then(function(result) {
          return result.done ? result.value : iter.next();
        });
  };