id,summary,reporter,owner,description,type,status,milestone,component,version,severity,resolution,keywords,cc
5098,[result_of] decltype-based result_of cannot handle rvalue-reference correctly,mimomorin@…,Daniel Walker,"The implementation of decltype-based boost::result_of is essentially the same as 
{{{
// This code is taken from N1454 (author: Douglas Gregor)
template <typename F, typename T1, typename T2, ..., typename TN>
class result_of<F(T1, T2, ..., TN)> {
    static F f;
    static T1 t1;
    static T2 t2;
         .
         .
         .
    static TN tN;
    
public:
    // Note: even if Ti is rvalue reference, ti is treated as lvalue.
    typedef decltype(f(t1, t2, ..., tN)) type;
};
}}}
So, the implementation cannot handle rvalue-reference correctly (it becomes lvalue). 

For example, in the following code
{{{
struct func
{
    unsigned char operator()(int&&     ) { return 0; }
      signed char operator()(int&      ) { return 0; }
             char operator()(int const&) { return 0; }
};
}}}
`boost::result_of<func(int)>::type` is `signed char` (which should be `unsigned char`).

I will attach a patch for fixing this issue.
The patch uses `declval` rather than static members. ",Patches,closed,To Be Determined,utility,Boost Development Trunk,Problem,fixed,result_of decltype,