TypeError: this.form._updateTreeValidity is not a function

Binding the template variable #contactForm appears to cause a name conflict and blow up the template processor as it tries to turn the attached template variable into an NgForm on the backend. Everywhere I have seen model driven forms used there is no template variable binding on the form, whereas there is a #tv="ngForm" utilized in template driven forms. It appears there was a miss on the mixing of the two forms approaches which resulted in the error.

Simply removing it will resolve the issue.

It's been a while, but for me the problem was passing the formGroup to the template instead of referencing it directly.

E.g. this is not working

<ng-template #selectField             let-field             let-group             let-frmName="frmName">    <ng-container [formGroup]="group">        <mat-form-field fxFlex="32"                        floatLabel="always">            <mat-label>{{field.label}}</mat-label>            <mat-select [formControlName]="frmName"                        [required]="field.required">                <mat-option *ngFor="let option of field.options"                            [value]="option.value">                    {{option.description}}                </mat-option>            </mat-select>        </mat-form-field>    </ng-container></ng-template>

If I use directly my formGroup instance it works just fine.

Hope this helps.

When you incorrectly add to your template formGroup="..." instead of [formGroup]="..." you'll also get this error message.