C++0x Concepts - Dead?

[Walter Bright]

Christian Kamm wrote:
>> Christian Kamm wrote:
>>> Is there a difference between
>>> template Foo(T : U) {} and
>>> template Foo(T) if(is(T : U)) {} ?
>>>
> 
> Walter Bright wrote:
>> Yes. Constraints determine the list of candidate template declarations,
>> but do not participate in the partial ordering of candidates to
>> determine the 'best' match.
> 
> Thanks for the explanation!
> 
> I expect the reason is that for constrained templates it is impossible to 
> determine whether all valid template arguments for one would lead to a valid 
> instantiation of another?
> 
> 

That's a good technical reason, but I also felt that the current way 
just made intuitive sense.