title: Angular 2 - Directives declared yet still have errors
body: <p>In <code>RootModule</code>:</p>
  
  <pre><code>@NgModule({
      imports: [
          ModuleA
      ],
      declarations: [
          ScrollToWhen
      ],
      bootstrap: [BootComponent],
  })
  class RootModule {}
  </code></pre>
  
  <p>In one of the component template inside Module A, I use <code>ScrollToWhen</code>, but I got error: <code>Can't bind to 'scrollToWhen' since it isn't a known property of 'div'</code>.</p>
  
  <p>Why?</p>
  
  <p><a href="https://i.stack.imgur.com/ti8cb.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ti8cb.png" alt=""></a></p>
  
  <p><code>Error: Unexpected directive 'HbClass' imported by the module 'Module'</code></p>