title: TypeScript property decorator : access to other properties
body: <p>I have a class Point like this :</p>
  
  <pre><code>class Point {
      @test('admin') x: number = 6
  
      y: number = 5
  }
  </code></pre>
  
  <p>With Test decorator : </p>
  
  <pre><code>function test(myValue: string) {
      function t(target: Object, propertyKey: string, descriptor: 
      TypedPropertyDescriptor&lt;any&gt;) {
          //want to test y value &gt; x value 
      }
  return &lt;any&gt;t
  }
  </code></pre>
  
  <p>In my test I want to check y value for exemple throw an error if x &lt; y</p>
  
  <p>Is it possible ?</p>