Re: [boost] [enable_if] usage in class specialization

From: Peter Dimov (pdimov_at_[hidden])
Date: 2007-06-25 11:50:15

Maurizio Vitale wrote:

> In short, the documentation for enable_if shows that it can be used
> for selecting a class specialization depending on a predicate. Now
> Intel C++ refuses to do that and the frontend team at Intel believes
> this
> is the right thing to do (although they'll look into the issue
> further for the sake of compatibility with GCC). Their argument is
> that the SFINAE rule applies to the selection of the overload set for
> functions only and not to partial specialization for classes.

I think that the compiler is right to reject your code since the predicate 
doesn't depend on T. The S in SFINAE stands for 'substitution', and no 
substitution occurs in your predicate. The instantiation of S<B> can fail 
even without a reference to foo because your second declaration of foo is 
ill-formed.