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