Property enumeration for NodeList, etc.

Cameron,

I've just read your new (from 5/25) section on property enumeration order:
>
>
>         4.6.7. Property enumeration
>
> This document does not define a complete property enumeration order 
> for all host objects implementing interfaces 
> <http://dev.w3.org/2006/webapi/WebIDL/#dfn-interface> (neither for 
> host exception objects 
> <http://dev.w3.org/2006/webapi/WebIDL/#dfn-host-exception-object>). 
> However, if a host object implements an interface that supports 
> indexed 
> <http://dev.w3.org/2006/webapi/WebIDL/#dfn-support-indexed-properties> 
> or named properties 
> <http://dev.w3.org/2006/webapi/WebIDL/#dfn-support-named-properties>, 
> then properties on the object MUST be enumerated in the following order:
>
>    1. If the object supports indexed properties
>       <http://dev.w3.org/2006/webapi/WebIDL/#dfn-support-indexed-properties>,
>       then the object's supported property indexes
>       <http://dev.w3.org/2006/webapi/WebIDL/#dfn-supported-property-indexes>
>       are enumerated first, in numerical order.
>    2. If the object supports named properties
>       <http://dev.w3.org/2006/webapi/WebIDL/#dfn-support-named-properties>,
>       then the object's supported property names
>       <http://dev.w3.org/2006/webapi/WebIDL/#dfn-supported-property-names>
>       are enumerated next, in the order given in the definition of the
>       set of supported property names.
>    3. No further own properties or properties from the object's
>       prototype chain are enumerated.
>

Is point 3 for real?  If I get a NodeList like document.childNodes and 
use it in a for/in loop, I'll just get the index elements and not the 
enumerable inherited length and item?  And if I add an enumerable 
expando property to that NodeList, it won't be enumerated either?

Is there any precedent for this?  What other objects behave this way?

     David