title: X is not a function in onClick
body: <p>I have a basic loop:</p>
  
  <pre><code>    markers.forEach((marker) =&gt; {
        marker.addListener('click', this.openInfoWindow(marker));
      })
  </code></pre>
  
  <p>I have a TypeScript function declared as:</p>
  
  <pre><code>openInfoWindow(marker) { }
  </code></pre>
  
  <p>I am getting:</p>
  
  <blockquote>
    <p>zone-evergreen.js:172 Uncaught TypeError: this.openInfoWindow is not a
    function
        at some.component.ts:147
        at Array.forEach ()
        at Di. (some.component.ts:145)
        at ne.H
        at Object.<em>.N.trigger
        at re
        at Di.</em>.O.set
        at Di.setZoom
        at map.js:29
        at xw.T (map.js:41)</p>
  </blockquote>
  
  <p>Why is this occuring?  What is wrong with my <code>click</code> call that would result in TypeScript not seeing this function?</p>