Property 'xxxx' does not exist on type '{ [key: string]: AbstractControl; }'

import { FormGroup } from '@angular/forms';

export class MasterVendorFormContactComponent implements OnInit {
  @Input() formContactGroup: FormGroup;
// rest of the code 
}


<fieldset [formGroup]="formContactGroup" class="master-vendor-form-contact">
  <md-input-container class="master-vendor-form-contact__phone"
                      [dividerColor]="formContactGroup.controls.phone?.valid ? 'default' : 'warn'">
    <input mdInput placeholder="Enter phone" formControlName="phone">
    <md-hint align="end"
             *ngIf="!formContactGroup.controls.phone?.valid">
      Vendor phone number must be in (XXX) XXX-XXXX format
    </md-hint>
  </md-input-container>
  <!-- Rest of the code -->
</fieldset>

on compiling this code with aot it gives following error:

angular_app/src/$$_gendir/app/master-vendors/master-vendor-form-contact/master-vendor-form-contact.component.ngfactory.ts (465,73): Property 'phone' does not exist on type '{ [key: string]: AbstractControl; }'.
angular_app/src/$$_gendir/app/master-vendors/master-vendor-form-contact/master-vendor-form-contact.component.ngfactory.ts (465,143): Property 'phone' does not exist on type '{ [key: string]: AbstractControl; }'.
angular_app/src/$$_gendir/app/master-vendors/master-vendor-form-contact/master-vendor-form-contact.component.ngfactory.ts (476,77): Property 'phone' does not exist on type '{ [key: string]: AbstractControl; }'.
angular_app/src/$$_gendir/app/master-vendors/master-vendor-form-contact/master-vendor-form-contact.component.ngfactory.ts (476,147): Property 'phone' does not exist on type '{ [key: string]: AbstractControl; }'.

I tried following this approach:

Don’t use form.controls.controlName, use form.get(‘controlName’)

but here I have formContactGroup so it seems not working for me.

There are two options, you can update to the latest typescript version. Since version 2.2 they allow the dot notation for types with string index signatures.

Or you can change your template, which makes more sense because that's the proper way to do it :) documentation:

<md-input-container [dividerColor]="formContactGroup.get('phone').valid ? 'default' : 'warn'">