title: FormGroup Angular issue (missing in type)
body: <p>When I run the command <strong>ng serve --prod</strong> I have this issue:</p>
  
  <blockquote>
    <p>ERROR in ng:///home/cristopher_ramirez/Development/angularProjects/lazyPagesRouterTest/src/app/service-order/add-service-order/add-service-order.component.html (28,51): Argument of type 'FormGroup' is not assignable to parameter of type 'ServiceOrder'.<br>
        Property 'cylinderRefsList' is missing in type 'FormGroup'.</p>
  </blockquote>
  
  <p>Note that this only happens when i use the --prod command.</p>
  
  <p>this is my HTML code (add-service-order.component-html):</p>
  
  <pre><code>&lt;div class="container"&gt;
  &lt;form [formGroup]="serviceOrderForm" novalidate (ngSubmit)="save(serviceOrderForm)"&gt;
  &lt;div formArrayName="cylinderRefsList"&gt;
    &lt;div class="card cardCylinder"&gt;
      &lt;div *ngFor="let cylinder of serviceOrderForm.controls['cylinderRefsList']['controls']; let i=index" class="panel panel-default"&gt;
        &lt;div class="card-header"&gt;
          &lt;span&gt;Cilindro {{i + 1}}&lt;/span&gt;
          &lt;button type="button" class="close" aria-label="Close" *ngIf="serviceOrderForm.controls['cylinderRefsList']['controls'].length &gt; 1"
            (click)="removeCylinder(i)"&gt;
            &lt;span aria-hidden="true"&gt;&amp;times;&lt;/span&gt;
          &lt;/button&gt;
        &lt;/div&gt;
        &lt;div class="card-body" [formGroupName]="i"&gt;
          &lt;app-cylinder [group]="serviceOrderForm.controls['cylinderRefsList']['controls'][i]"&gt;&lt;/app-cylinder&gt;
        &lt;/div&gt;
      &lt;/div&gt;
    &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>I was following this guide  <a href="https://scotch.io/tutorials/how-to-build-nested-model-driven-forms-in-angular-2" rel="nofollow noreferrer">https://scotch.io/tutorials/how-to-build-nested-model-driven-forms-in-angular-2</a>  so as you can see i actually added the cylinderRefsList in the formgroup (my TS file is almost the same as the guide) the only difference is that i use models instead of interface.</p>
  
  <p>EDIT 1: this is my TS file</p>
  
  <pre><code>export class AddServiceOrderComponent implements OnInit {
  
    public serviceOrderForm: FormGroup;
  
    errMessage: string;
    model;
    structures: any = [];
    structureName = 'Obras';
    isStructure = false;
    isDate = false;
    websafeKey: any;
   orderDate: any;
   dateTicks = 0;
   role: string;
  
    constructor(
      private router: Router,
     private structureService: StructureService,
   private serviceOrderService: ServiceOrderService,
   private fb: FormBuilder,
   private userService: UserService
   ) {
   this.structureService.getAllStructures().subscribe(data =&gt; {
     this.structures = data;
     console.log(this.structures);
   });
   this.role = this.userService.getRoleUser();
   }
  
   ngOnInit() {
  this.serviceOrderForm = this.fb.group({
    cylinderRefsList: this.fb.array([])
   });
   this.addCylinder();
     }
  
     initCylinders() {
      return this.fb.group({
       colado: ['', Validators.required],
         ruptura: ['', Validators.required],
       edad: ['', Validators.required],
       rev: ['', Validators.required],
       altura: ['', Validators.required],
       area: ['', Validators.required],
      cargaKn: ['', Validators.required],
     cargaKgf: ['', Validators.required],
      resistenciaKgf: ['', Validators.required],
      resistenciaMpa: ['', Validators.required],
      resistenciaProy: ['', Validators.required],
      resistenciaPorce: ['', Validators.required],
      ubicacion: ['', Validators.required]
    });
    }
  
    addCylinder() {
     const control = 
   &lt;FormArray&gt;this.serviceOrderForm.controls['cylinderRefsList'];
  const addrCtrl = this.initCylinders();
  control.push(addrCtrl);
     }
  
    removeCylinder(i: number) {
     // remove address from the list
      const control = 
   &lt;FormArray&gt;this.serviceOrderForm.controls['cylinderRefsList'];
  control.removeAt(i);
    }
  
    save(model: ServiceOrder) {
        this.orderDate = new Date(this.model.year, this.model.month - 1, 
      this.model.day);
       this. dateTicks = ((this.orderDate.getTime() * 10000) + 
    621356076000000000);
    this.serviceOrderService.postServiceOrder(this.dateTicks, this.websafeKey, 
     model['controls']['cylinderRefsList']['value'] )
    .subscribe(data =&gt; {
      if (this.role === 'Admin' || this.role === 'Director') {
        this.router.navigate(['/home/service-order']);
      } else if (this.role === 'Tecnico') {
        this.router.navigate(['/home-tecnician/service-order']);
      } else if (this.role === 'Supervisor') {
        this.router.navigate(['/home-supervisor/service-order']);
      }
    });
    }
  
    structureInfo(structureName: string, websafeKey: string) {
  this.structureName = structureName;
  this.websafeKey = websafeKey;
   }
  </code></pre>