title: Typescript cannot find interface name
body: <p>In my Typescript file <em>(which is a part of Aurelia View-Model)</em>, I have following structure:</p>
  
  <pre><code>import {Chart} from './chart';
  
  interface IMargin {
      top: number, right: number, bottom: number, left: number
  }
  
  export class App{
  
      chartOptions: any;
  
      constructor(margin: IMargin) { // No error here
  
          this.chartOptions = {
              element: "#chart",
              margin: IMargin    // Error: Cannot find name "IMargin"
          };
      }
  
      attached() {
          var chart = new Chart(this.chartOptions);
          chart.addChart();
      }
  }
  </code></pre>
  
  <p><code>Typescript</code> compiler has no problem with using interface in the constructor, but it gives the error <code>Cannot find name "IMargin"</code> when I use it to define <code>margin</code> inside the constructor. Why is that? </p>
  
  <p>Also, Where is the best place to declare interfaces, if this is not the correct way? Thank you. </p>