title: Property missing in state but is only a prop with flow
body: <pre><code>import * as React from 'react';
  
  type Props = {
    number: number,
  }
  
  type State = {
  
  }
  
  class Other extends React.Component &lt;State, Props&gt; {
    render() {
      const { number } = this.props;
      return (
        &lt;div className="container"&gt;
          {number}
        &lt;/div&gt;
      );
    }
  }
  </code></pre>
  
  <p>//</p>
  
  <pre><code>import * as React from 'react';
  type Props = {
  
  }
  
  type State = {
    number: number,
    cards: Array&lt;{suit: string} | {rank: number}&gt;,
  }
  
  class Example extends React.Component &lt;Props, State&gt;{
       &lt;Other
         number={this.state.number}
       /&gt;
  }
  </code></pre>
  
  <p>so, I'm getting this weird error with flow after integrating with React. My <code>Example</code> component passes <code>number</code> state down as a prop to <code>Other</code>. and in <code>Other</code> I have told it that <code>number</code> is a prop that should be of type number. however, it complains and says that it should be in state??</p>
  
  <p>I get it should be state in the original component but why is it wanting it to be state in the new component? surely declaring it in state doesn't make sense as it's just a read-only prop that I want to render</p>