Re: [boost] [type_traits][multi_index][msvc-7.1] problems with is_const in VC 7.1

Subject: Re: [boost] [type_traits][multi_index][msvc-7.1] problems with is_const in VC 7.1
From: Ion Gaztañaga (igaztanaga_at_[hidden])
Date: 2015-10-15 13:00:42

On 15/10/2015 13:22, Joaquin M LópezMuñoz wrote:
>>
>
> Hi,
>
> Boost.MultiIndex is failing at master for VC 7.1:
>
> http://tinyurl.com/oxflkj6
>
> .\boost\multi_index\identity.hpp(75) : error C2535:
> 'Type &boost::multi_index::detail::const_identity_base<Type>::operator()
> (const boost::reference_wrapper<Type> &) const' : member function already
> defined or declared
>
> the problem seemingly being with boost::is_const. The offending code
> looks like
>
> template<typename Type>
> struct const_identity_base
> {
>    // produces the error above if Type is not const
> };
>
> template<typename Type>
> struct non_const_identity_base
> {
>    ...
> };
>
> template<class Type>
> struct identity:
>    mpl::if_c<
>      is_const<Type>::value,
>      detail::const_identity_base<Type>,
>      detail::non_const_identity_base<Type>
>    >::type
> {
> };

Sometimes MSVC-7.1 seems to be happier with a bit more flattened 
template instantiation chain. Maybe if you SFINAE it with partial 
specialization of identity it will work.

Another option is to use if_<> instead of if_c. It could make MSVC happier.

Best,

Ion