docs: Documents utility functions for narrowing form control types (#64373)

PR Close #64373

packages/forms/src/model/form_array.ts

@@ -582,6 +582,8 @@ export const UntypedFormArray: UntypedFormArrayCtor = FormArray;
  * @description
  * Asserts that the given control is an instance of `FormArray`
  *
+ * @see [Utility functions for narrowing form control types](guide/forms/reactive-forms#utility-functions-for-narrowing-form-control-types)
+ *
  * @publicApi
  */
 export const isFormArray = (control: unknown): control is FormArray => control instanceof FormArray;

packages/forms/src/model/form_control.ts

@@ -621,6 +621,8 @@ export const UntypedFormControl: UntypedFormControlCtor = FormControl;
  * @description
  * Asserts that the given control is an instance of `FormControl`
  *
+ * @see [Utility functions for narrowing form control types](guide/forms/reactive-forms#utility-functions-for-narrowing-form-control-types)
+ *
  * @publicApi
  */
 export const isFormControl = (control: unknown): control is FormControl =>

packages/forms/src/model/form_group.ts

@@ -709,6 +709,8 @@ export const UntypedFormGroup: UntypedFormGroupCtor = FormGroup;
  * @description
  * Asserts that the given control is an instance of `FormGroup`
  *
+ * @see [Utility functions for narrowing form control types](guide/forms/reactive-forms#utility-functions-for-narrowing-form-control-types)
+ *
  * @publicApi
  */
 export const isFormGroup = (control: unknown): control is FormGroup => control instanceof FormGroup;
@@ -827,6 +829,8 @@ export interface FormRecord<TControl> {
  * @description
  * Asserts that the given control is an instance of `FormRecord`
  *
+ * @see [Utility functions for narrowing form control types](guide/forms/reactive-forms#utility-functions-for-narrowing-form-control-types)
+ *
  * @publicApi
  */
 export const isFormRecord = (control: unknown): control is FormRecord =>