How to escape implicit 'with (this)' of a method body

P T Withington ptw at
Tue Jul 29 06:18:41 PDT 2008

On 2008-07-29, at 01:19EDT, Brendan Eich wrote:

> On Jul 28, 2008, at 10:05 PM, Jon Zeppieri wrote:
> The original code used "without (this)", not "with", which I took to  
> mean "avoid instance properties shadowing globals".

Indeed.  Perhaps I was being too clever in my pseudo-code.

> If you read the original as "with", then there is no such problem.  
> But if you construct a problematic case using 'with' and dynamic  
> properties, then I concede that 'global' could be shadowed. This is  
> a reason to avoid 'with'. In the ES4 proposals last sent out, you  
> could always use __ES4__::global if you really wanted to avoid  
> conflicts -- unless someone perversely added '__ES4__' as a dynamic  
> instance property.
> There's no solution to this problem other than reserving at least  
> one name, and we can't do that compatibly. We could reserve __ES4__  
> in version-selected ES4 mode, but that seems unnecessary.

I guess this is considered a small penalty to pay in exchange for  
adding the magical instance scope to methods (which O-O programmers  
seem to expect these days).  Something we'd regret more if we had  
multi-methods, perhaps...

More information about the Es4-discuss mailing list