title: Property 'xxx' does not exist on type '{}'
body: <p>I run into a strange behavior in my angular app today.</p>
  
  <pre><code>ERROR in src/main(A,B): error TS2339: Property 'XXX' does not exist on type '{}'.
  </code></pre>
  
  <p>The error occured at the following line of code</p>
  
  <pre><code>xxx.subscribe(data =&gt; {
      this.var = data.XXX
  });
  </code></pre>
  
  <p>So basically i subscribe to an observable and map the data from the observable to an global var. My angular App works as intended, so this error seems to have no effect on the app itself, but I still can't figure out whats wrong here. Below is the console log of <code>data</code>:</p>
  
  <pre><code>console.log(data)
  //{"XXX": "test"}
  </code></pre>