title: Source has X element(s) but target allows only 1
body: <p>The typescript compile show this error:</p>
  <blockquote>
  <p>Source has X element(s) but target allows only 1.</p>
  </blockquote>
  <pre><code>export const FooMapping: [{id: FooOperation, display: string}] = [
      { id: FooOperation.Undefined, display: 'Nothing' },
      { id: FooOperation.A, display: 'I'm A' },
      { id: FooOperation.B, display: 'I'm B' }
  ];
  
  export enum FooOperation {
      Undefined = 0,
      A = 1,
      B = 2,
  }
  </code></pre>
  <p>What is the correct way to define an array of special object of <code>{id: FooOperation, display: string}</code>?</p>