title: React children[] issue with TypeScript
body: <p>I have one component <code>Radio</code>:</p>
  
  <pre><code>import { RadioItemProps } from './Item';
  
  type Props = {
    children: ReactElement&lt;RadioItemProps&gt;[];
  };
  
  export default function Radio(props: Props) {
    return props.children;
  }
  </code></pre>
  
  <p>and a component <code>RadioItem</code> that should be a direct child of <code>Radio</code>:</p>
  
  <pre><code>export type RadioItemProps = {
    value: string;
    children: ReactText;
  };
  
  export default function RadioItem(props: RadioItemProps) {
    return &lt;input type="radio" name="xxx" value={props.value} /&gt;;
  }
  </code></pre>
  
  <p>When I use them:</p>
  
  <pre><code>&lt;Radio&gt;
    &lt;RadioItem value="option-1"&gt;Option 1&lt;/RadioItem&gt;
    &lt;RadioItem value="option-1"&gt;Option 1&lt;/RadioItem&gt;
  &lt;/Radio&gt;
  </code></pre>
  
  <p>I have the TypeScript error: <code>JSX element type 'ReactElement&lt;RadioItemProps, ...&gt;[]' is missing the following properties f rom type 'Element': type, props, key</code></p>
  
  <p>If I change the children type to <code>ReactElement&lt;RadioItemProps&gt;</code>, and add only one child, it works. But once I put the array, I get this error.</p>
  
  <p>What I am missing?</p>
  
  <pre><code>"typescript": "^3.2.2",
  "react": "16.7.0-alpha.2",
  "react-dom": "16.7.0-alpha.2",
  "@types/react": "^16.8.3",
  "@types/react-dom": "^16.0.11",
  </code></pre>