plug this into regenerator: the transpiled argument to spawn matches the interface to generators 1-1 so it has no issues

spawn-case.js

// spawn() taken unmodified from https://gist.github.com/Benvie/8327917
// See http://taskjs.org for the original.
function spawn(thunk) {
  return new Promise(function(resolve, reject) {
    var gen = thunk();
 
    function _next(v) {
      return handle(gen.next(v));
    }
 
    function _throw(e) {
      return handle(gen.throw(e));
    }
 
    function handle(result) {
      var value = result.value;
      if (!result.done && value && typeof value.then === "function") {
        return value.then(_next, _throw);
      }
      return value;
    }
 
    Promise.cast(_next()).then(resolve, reject);
  });
}
spawn(function* () {
  var hello = 'hello';
  var result = yield new Promise(function (f,r) {
    setTimeout(function () {
      f(hello + ' world!');
    }, 1e3);
  });
  console.log(result);
});