WebStorm autocomplete with NodeJS and Koa js

Question

It may sounds like a joke, but I'm really demoralized with several things about Autocomplete in WebStorm.

1. When I try to put Generator-function into koajs use method, I get error.
2. There is no autocomplete with Koa JS methods.

I tried to fix problem with TypeScript-definitions, but It is not work.

But if I create Koa instance with new, autocomplete will appears.

But another problem appears.

This code works good, but I'm demoralized with these errors and can't write my project.... :( Help me!

P.S. I have set ES6 standard in JavaScript settings.