为什么是B<int>::bar<int> == true以及如何解决这个问题？
编辑：看起来问题在于B专门化不正确

#include <iostream>

template <class T>
struct A {
  static bool foo;
};

template <class T>
struct B {
  template <class U>
  static bool bar;
};

// assigning default values (works as expected)
template <class T>
bool A<T>::foo = true;

template <class T> template <class U>
bool B<T>::bar = true;

// template specialization
template <>
bool A<int>::foo = false; // works as expected

template <> template <class U>
bool B<int>::bar = false; // not working

int main() {
  std::cout << A<char>::foo << '\n';       // 1
  std::cout << A<int>::foo << '\n';        // 0   works fine
  std::cout << B<char>::bar<char> << '\n'; // 1
  std::cout << B<int>::bar<int> << '\n';   // 1   why is it true?
}

看起来由于某种原因，这些代码行没有将B<int>::bar<int>设置为false：

template <> template <class U>
bool B<int>::bar = false;