将 NULL/nullptr 转换为 std：：function<>& 时失败

这段代码在VC2013中无法构建：(编辑：我不是在问为什么它无法构建(

#include <functional>
struct MyStruct
{
    std::function<void()> m_Func;
    MyStruct( const std::function<void()>& func) :  m_Func(func)   {}
};

int main()
{
    MyStruct rc( NULL );
    return 0;
}

有错误：

1>c:program files (x86)microsoft visual studio 12.0vcincludexrefwrap(283): error C2064: term does not evaluate to a function taking 0 arguments
1>          c:program files (x86)microsoft visual studio 12.0vcincludefunctional(228) : see reference to function template instantiation '_Ret std::_Callable_obj<int,false>::_ApplyX<_Rx,>(void)' being compiled
1>          with
1>          [
1>              _Ret=void
1>  ,            _Rx=void
1>          ]
1>          c:program files (x86)microsoft visual studio 12.0vcincludefunctional(228) : see reference to function template instantiation '_Ret std::_Callable_obj<int,false>::_ApplyX<_Rx,>(void)' being compiled
1>          with
1>          [
1>              _Ret=void
1>  ,            _Rx=void
1>          ]
1>          c:program files (x86)microsoft visual studio 12.0vcincludefunctional(226) : while compiling class template member function 'void std::_Func_impl<_MyWrapper,_Alloc,_Ret,>::_Do_call(void)'
1>          with
1>          [
1>              _Alloc=std::allocator<std::_Func_class<void,>>
1>  ,            _Ret=void
1>          ]
1>          c:program files (x86)microsoft visual studio 12.0vcincludefunctional(495) : see reference to class template instantiation 'std::_Func_impl<_MyWrapper,_Alloc,_Ret,>' being compiled
1>          with
1>          [
1>              _Alloc=std::allocator<std::_Func_class<void,>>
1>  ,            _Ret=void
1>          ]
1>          c:program files (x86)microsoft visual studio 12.0vcincludefunctional(396) : see reference to function template instantiation 'void std::_Func_class<_Ret,>::_Do_alloc<_Myimpl,_Ty,_Alloc>(_Fty &&,_Alloc)' being compiled
1>          with
1>          [
1>              _Ret=void
1>  ,            _Ty=int
1>  ,            _Alloc=std::allocator<std::_Func_class<void,>>
1>  ,            _Fty=int
1>          ]
1>          c:program files (x86)microsoft visual studio 12.0vcincludefunctional(396) : see reference to function template instantiation 'void std::_Func_class<_Ret,>::_Do_alloc<_Myimpl,_Ty,_Alloc>(_Fty &&,_Alloc)' being compiled
1>          with
1>          [
1>              _Ret=void
1>  ,            _Ty=int
1>  ,            _Alloc=std::allocator<std::_Func_class<void,>>
1>  ,            _Fty=int
1>          ]
1>          c:program files (x86)microsoft visual studio 12.0vcincludefunctional(385) : see reference to function template instantiation 'void std::_Func_class<_Ret,>::_Reset_alloc<_Ty,std::allocator<std::_Func_class<_Ret,>>>(_Fty &&,_Alloc)' being compiled
1>          with
1>          [
1>              _Ret=void
1>  ,            _Ty=int
1>  ,            _Fty=int
1>  ,            _Alloc=std::allocator<std::_Func_class<void,>>
1>          ]
1>          c:program files (x86)microsoft visual studio 12.0vcincludefunctional(385) : see reference to function template instantiation 'void std::_Func_class<_Ret,>::_Reset_alloc<_Ty,std::allocator<std::_Func_class<_Ret,>>>(_Fty &&,_Alloc)' being compiled
1>          with
1>          [
1>              _Ret=void
1>  ,            _Ty=int
1>  ,            _Fty=int
1>  ,            _Alloc=std::allocator<std::_Func_class<void,>>
1>          ]
1>          c:program files (x86)microsoft visual studio 12.0vcincludefunctional(671) : see reference to function template instantiation 'void std::_Func_class<_Ret,>::_Reset<_Ty>(_Fty &&)' being compiled
1>          with
1>          [
1>              _Ret=void
1>  ,            _Ty=int
1>  ,            _Fty=int
1>          ]
1>          c:program files (x86)microsoft visual studio 12.0vcincludefunctional(671) : see reference to function template instantiation 'void std::_Func_class<_Ret,>::_Reset<_Ty>(_Fty &&)' being compiled
1>          with
1>          [
1>              _Ret=void
1>  ,            _Ty=int
1>  ,            _Fty=int
1>          ]
1>          f:workteststdfunctionteststdfunction.cpp(16) : see reference to function template instantiation 'std::function<void (void)>::function<int>(_Fx &&)' being compiled
1>          with
1>          [
1>              _Fx=int
1>          ]
1>          f:workteststdfunctionteststdfunction.cpp(16) : see reference to function template instantiation 'std::function<void (void)>::function<int>(_Fx &&)' being compiled
1>          with
1>          [
1>              _Fx=int
1>          ]

(请注意最后两个报告错误的"_Fx=int"(。

我可以忍受这一点，因为将MyStruct rc(NULL)更改为MyStruct rc(nullptr)可以解决错误。 然而，有两件事仍然是个谜：

1(从MyStruct ctor中删除常量限定符(MyStruct( std::function<void()>& func)会给出一个非常非常不同的错误：

1>f：\work\main\dev\common\teststdfunction\teststdfunction\teststdfunction.cpp(16(： 错误 C2664： 'MyStruct：：MyStruct(const MyStruct &(' ： 无法转换 参数 1 从 'int' 到 'std：：function &'

这比原始错误更有意义，现在将 NULL 修复为 nullptr 并不能解决它。 为什么int(或nullptr(拒绝投射到std::function<>&而是同意投射到const std::function<>&？

2(原始代码在VS2010中按预期编译和工作。 这是一个晦涩难懂的VS2010库错误吗？

编辑：就 const/non const 问题而言，我现在认为所涉及的演员阵容和潜在的类型不匹配可能是一个红鲱鱼。 传递的参数 - NULL 或 nullptr - 是一个文字，因此是一个常量。它只是无法绑定到非常量引用。 例如：

const int& a = 8;   // Ok
int& b = 9;    // error C2440: 'initializing' : cannot convert from 'int' to 'int &' 

听起来对吗？ 我还缺少什么吗？