Compiler does not report errors for Declarations tag within default property value

Steps to reproduce:
1. In an app, paste the following MXML:
<s:RichEditableText x="291" y="147" text="my text"/>
<fx:Declarations>
<s:RadioButtonGroup id="radiogroup1"/>
</fx:Declarations>

<mx:RadioButton x="74" y="217" label="Button 1" groupName="radiogroup1"/>
<mx:RadioButton x="74" y="243" label="Button 2" groupName="radiogroup1"/>

Actual Results:
The compiler does not yield any errors for this. This is inconsistent with the behavior for Script, MetaData, Style, etc, cases in which you'd see the error: "Child elements specifying default property must be contiguous."