title: Using ReactiveFormsModule on module lazyloaded
body: <p>I have this main module in Angular 4:</p>
  
  <pre><code>@NgModule({
      imports: [
          //.. other modules
          ReactiveFormsModule,
      ],
      declarations: [
          AppComponent,
          ...routingComponents,
      ],
      providers: [
          ...routingGuards,
      ],
      exports: [
          ReactiveFormsModule,
      ],
      bootstrap: [AppComponent]
  })
  
  export class AppModule { }
  </code></pre>
  
  <p>I also have another module, AdminModule, that is lazy loaded from this main AppModule. On the AdminModule I have some routes where I also use the reactive form. However, when I try to create a new form I keep getting errors like these:</p>
  
  <blockquote>
    <p>Error: Template parse errors: Can't bind to 'formGroup' since it isn't a known property of 'form'.</p>
  </blockquote>
  
  <p>Trying to fix this problem, I saw that I had to export the ReactiveFormsModule from the main module in order to use with other modules, but I'm doing so and still getting the error. What am I doing wrong in here?</p>