Crow：Middlewares 庖丁解牛5 context

Crow：Middlewares 庖丁解牛4 partial_context-CSDN博客

基于partial_context再来解释context

namespace detail
{
    template
    struct partial_context : public pop_back::template rebind, public last_element_type::type::context
    {
        using parent_context = typename pop_back::template rebind;
        template
        using partial = typename std::conditional