TextRange class raises RTE at the run-time because owner paramter passed into the constuctor must have defined "getTextField()" method in mx:internal namespace

Steps to reproduce:
1. I've created a new custom component that extends from UIComponent called ExtendedText (see simplified code in the attached file)

2. I'd like to allow the users of my ExtendedText component to allow modify its selected text via following API

------------
public function get selection() : TextRange {
return new TextRange(this, true);
}
------------

3. I try to access selection property of ExtendedText, by calling

var selection : TextRange = myExtendedText.selection;

Actual Results:

RTE is raised

ReferenceError: Error #1069: Property http://www.adobe.com/2006/flex/mx/internal::getTextField not found on com.myCompany.controls.ExtendedText and there is no default value.

Expected Results:

TextRange component must impose at the compile time at "owner " component to have getTextField() method implemented as PUBLIC , this can be done by creating a new interface class called ITextElement with single method getTextField()

Now TextRange constructor is

public function TextRange(owner:UIComponent,
modifiesSelection:Boolean = false,
beginIndex:int = -1, endIndex:int = -1)

and I propose to change it to

public function TextRange(owner:ITextElement,
modifiesSelection:Boolean = false,
beginIndex:int = -1, endIndex:int = -1)

Workaround (if any):