条件类型特征通用引用的问题

因此，我有一个函数用于检查值，如果值无效，则抛出异常，否则在收到值时将其返回。我试图用普遍的虔诚和类型特征来概括这种惯例。我觉得我的例子在某些情况下有效，但不是全部。它似乎只适用于右值。

#include <iostream>
#include <utility>
#include <type_traits>
#include <string>
#include <vector>
using namespace std;
struct error_type{};
template <class T>
class has_empty
{
   template<class U, class = typename std::enable_if<std::is_member_pointer<decltype(&U::empty)>::value>::type>
      static std::true_type check(int);
   template <class>
      static std::false_type check(...);
public:
   static constexpr bool value = decltype(check<T>(0))::value;
};
template <bool invalid>
struct valid {};

template <>
struct valid<false>
{
   template<typename U, typename E>
   static inline U&& check(U&& toCheck, const E& toThrow)
   {
      if (!toCheck)
        std::cout << "NoEmpty Throw" << 'n';
      else
        std::cout << "NoEmpty valid" << 'n';
      return std::forward<U>(toCheck);
   }
};
template <>
struct valid<true>
{
   template<typename U, typename E>
   static inline U&& check(U&& toCheck, const E& toThrow)
   {
      if (toCheck.empty())
        std::cout << "HasEmpty Throw" << 'n';
      else
        std::cout << "HasEmpty valid" << 'n';
      return std::forward<U>(toCheck);
   }
};
template<typename T
   , typename E
   , typename  = typename std::enable_if<std::is_base_of<error_type, E>::value>::type>
   inline T&& do_check(T&& toCheck, const E& toThrow)
{
   return valid<has_empty<T>::value>::check(std::forward<T>(toCheck), toThrow);
}
struct HasEmpty
{
    bool empty() {return false;}
};
struct NoEmpty
{
};

int main()
{
    error_type e;
    cout << has_empty<std::wstring>::value << 'n';
    cout << has_empty<std::vector<std::wstring>>::value << 'n';
    cout << has_empty<int>::value << 'n';
    cout << has_empty<HasEmpty>::value << 'n';
    cout << has_empty<NoEmpty>::value << 'n';
    do_check(true, e);
    do_check(false, e);
    do_check(std::string("45"), e);
    do_check(HasEmpty(), e);
    do_check(std::vector<bool>(), e);
    HasEmpty he;
    do_check(std::move(he), e);
    //do_check(he, e); // does not work, has_empty<T>::value is 0
}

生成输出

1
1
0
1
0
NoEmpty valid
NoEmpty Throw
HasEmpty valid
HasEmpty valid
HasEmpty Throw
HasEmpty valid

如果我取消注释最后一行，我会得到以下错误：

prog.cpp: In instantiation of 'static T&& valid<false, T, E>::check(T&&, const E&) [with T = HasEmpty&; E = error_type]':
prog.cpp:56:84:   required from 'T&& do_check(T&&, const E&) [with T = HasEmpty&; E = error_type; <template-parameter-1-3> = void]'
prog.cpp:87:19:   required from here
prog.cpp:30:11: error: no match for 'operator!' (operand type is 'HasEmpty')
       if (!toCheck)
           ^
prog.cpp:30:11: note: candidate is:
prog.cpp:30:11: note: operator!(bool) <built-in>
prog.cpp:30:11: note:   no known conversion for argument 1 from 'HasEmpty' to 'bool'

这表明CCD_ 1正在对CCD_ 2求值。我相信我可以做一些不同的工作来实现这一点，所以在这一点上，这是一种学术性的。尽管如此，任何帮助都将不胜感激。