title: Make typescript see props from decorators
body: <p>I have simple component that uses mobx and decorators like this</p>
  
  <pre><code>import * as React from "react";
  import { observer, inject } from "mobx-react/native";
  import { Router as ReactRouter, Switch, Route } from "react-router-native";
  import Dashboard from "./_dashboard";
  import { RouterInterface } from "../store/_router";
  
  // -- types ----------------------------------------------------------------- //
  export interface Props {
    router: RouterInterface;
  }
  
  @inject("router")
  @observer
  class Router extends React.Component&lt;Props, {}&gt; {
    // -- render -------------------------------------------------------------- //
    render() {
      const { router } = this.props;
      return (
        &lt;ReactRouter history={router.history}&gt;
          &lt;Switch location={router.location}&gt;
            &lt;Route path="/" component={Dashboard} /&gt;
          &lt;/Switch&gt;
        &lt;/ReactRouter&gt;
      );
    }
  }
  
  export default Router;
  </code></pre>
  
  <p>essentially <code>@inject("router")</code> adds <code>this.props.router</code> that satisfies Props interface above, however typescript doesn't account for this and whenever I use this component somewhere I get an error if I don't pass down <code>router</code> in props, hence I need to change to <code>router?: RouterInterface;</code> which is fine, but not ideal.</p>
  
  <p>Is there a way to fix this issue where typescript accounts for decorators injecting the props?</p>