title: Can you declare a object literal type that allows unknown properties in typescript?
body: <p>Essentially I want to ensure that an object argument contains all of the required properties, but can contain any other properties it wants.  For example:</p>
  
  <pre><code>function foo(bar: { baz: number }) : number {
      return bar.baz;
  }
  
  foo({ baz: 1, other: 2 });
  </code></pre>
  
  <p>But this results in:</p>
  
  <pre><code>Object literal may only specify known properties, and 'other' does not exist in type '{ baz: number; }'.
  </code></pre>