[boost] [tr1/result_of] SFINAE propagation by design?

From: Tobias Schwinger (tschwinger_at_[hidden])
Date: 2006-12-27 07:51:46

Hi Doug and Boost community,

I noticed that the Boost implementation of result_of uses inheritance to forward the type member of a nested result metafunction, so that result_of<...>::type can result in a substitution failure (and not an error when used in an appropriate context) if the nested result class template does not have a type member. 

It's surely a nice feature (also because it usually stops trace diagnostics at a reasonable point in case of an error). Should the standard text perhaps encforce that kind of implementation - e.g:

    [tr.func.ret.ret] 2 5 (b) 

        If N>0, result_of<F(T1, T2, ... TN)> inherits from 
        F::result<F(T1, T2, ... TN)>

? Comments?

Regards,
Tobias