title: Flowtype: Specify that array of functions can not be empty
body: <p>I have the following code:</p>
  
  <pre><code>function injectSagas (sagas: Array&lt;Function&gt;) {
    sagas.map(store.runSaga)
  }
  </code></pre>
  
  <p>Can I somehow make flow trow an error if <code>sagas</code> array is empty? </p>