mode_edit codeAPI / @angular/formsAsyncValidatorFnlinkinterface 稳定interface AsyncValidatorFn { (c: AbstractControl): Promise<ValidationErrors | null> | Observable<ValidationErrors | null> }方法link调用签名 linkmode_edit code(c: AbstractControl): Promise<ValidationErrors | null> | Observable<ValidationErrors | null>参数cType: AbstractControl.返回值Promise<ValidationErrors | null> | Observable<ValidationErrors | null>