问在实现类外模板类的模板方法时，C2244:无法将函数定义与现有声明匹配

EN

#include <concepts>

template <template <class...> class Template, class... Args>
void derived_from_specialization_impl(const Template<Args...>&);

template <class T, template <class...> class Template>
concept derived_from_specialization_of = requires(const T& t) {
    derived_from_specialization_impl<Template>(t);
};

template <class T>
class A
{
public:
    A() = default;
};

template <derived_from_specialization_of<A> T>
class B;

template <derived_from_specialization_of<B> T>
class C
{
public:
    C() = default;
};

template <derived_from_specialization_of<A> T>
class B
{
public:
    B() = default;

    template <derived_from_specialization_of<B> U>
    C<U> Foo();

    template <derived_from_specialization_of<B> U>
    C<U> Bar()
    {
        return C<U>();
    }
};

template <derived_from_specialization_of<A> T>
template <derived_from_specialization_of<B> U>
C<U> B<T>::Foo() 
{
    return C<U>();
}