问角形“确认密码”显示错误

EN

this.registerForm = this.formBuilder.group({
  firstName: ['', Validators.required],
  lastName: ['', Validators.required],
  email: ['', [Validators.required, Validators.email]],
  password: ['', [Validators.required]],
  confirmPassword: ['', [Validators.required]]
  },
  { validator: this.checkPasswords });


checkPasswords(group: FormGroup) {
  // here we have the 'passwords' group
  let pass = group.get('password').value;
  let confirmPassword = group.get('confirmPassword').value;
  return pass === confirmPassword ? null : { notSame: true };
}

<mat-form-field required>
    <input matInput type="password" placeholder="Password" formControlName="password">
    <mat-error>Password is not valid</mat-error>
</mat-form-field>

<mat-form-field required>
    <input matInput type="password" placeholder="Confirm password"
           formControlName="confirmPassword"
           [errorStateMatcher]="matcher">
    <mat-error *ngIf="registerForm.hasError('notSame')">Passwords do not match</mat-error>
</mat-form-field>