title: Property 'section 1' does not exist on type 'FormGroup'. aot build
body: <p>When I take aot build in angular I got an error Property 'section 1' does not exist on type 'FormGroup'. I had added </p>
  
  <pre><code>&lt;form [formGroup]="currentMonthForm" novalidate&gt;
  &lt;table class="table spinwheel-table-blk"&gt;
        &lt;thead&gt;
          &lt;tr COLSPAN=2 class="spinwheel-table-heading-block"&gt;
            &lt;th&gt;Section ID&lt;/th&gt;
            &lt;th&gt;&lt;span&gt;Points&lt;/span&gt;&lt;/th&gt;
          &lt;/tr&gt;
        &lt;/thead&gt;
        &lt;tbody&gt;
          &lt;tr COLSPAN=2&gt;
            &lt;td&gt;1&lt;/td&gt;
            &lt;td&gt;
              &lt;div class="input-group wingsclub-inputgroup"&gt;
                &lt;input type="text" class="form-control validation-field" placeholder="Points" aria-label="Recipient's username"
                  aria-describedby="basic-addon2" maxlength="3" formControlName="section1" [ngClass]="{ 'is-invalid': currentMonthForm.section1 }"
                  (input)="section1Change(1)"&gt;
                &lt;small class="text-danger" *ngIf="sectionFormErrors.section1"&gt;
                  &lt;small class="text-danger" *ngIf="sectionFormErrors.section1"&gt;{{sectionFormErrors.section1}}&lt;/small&gt;
                &lt;/small&gt;
              &lt;/div&gt;
            &lt;/td&gt;
          &lt;/tr&gt;
  &lt;table&gt;
  </code></pre>
  
  <p> </p>
  
  <p>and in component I had </p>
  
  <pre><code>currentMonthForm: FormGroup;
  constructor(){
  this.buildForm();
  }
      buildForm() {
          this.currentMonthForm = this.fb.group({
            section1: [null, Validators.compose([Validators.required, Validators.maxLength(3),
            CustomValidators.number, this.validateNumber, CustomValidatorsInUse.isInteger, CustomValidatorsInUse.isPositiveInteger,])],})
  </code></pre>
  
  <p>But I get error Property 'section 1' does not exist on type 'FormGroup'. in aot build. But in general build its working correctly.</p>