Why thrift not add Closure for async call?

[易剑 <ey...@gmail.com>]

// specified for 0 argument
template <typename R>
class Closure<R> : public ClosureBase
{
public:
    virtual R Run() = 0;
};

// specified for 1 argument
template <typename R, typename Arg1>
class Closure<R, Arg1> : public ClosureBase
{
public:
    virtual R Run(Arg1 arg1) = 0;
};

// specified for 2 arguments
template <typename R, typename Arg1, typename Arg2>
class Closure<R, Arg1, Arg2> : public ClosureBase
{
public:
    virtual R Run(Arg1 arg1, Arg2 arg2) = 0;
};

template <
    bool SelfDeleting,
    typename R,
    typename Class, typename MethodClass
>
class MethodClosure_Arg0_Bind0 : public Closure<R> {
    typedef R (MethodClass::*MethodType)();
public:
    MethodClosure_Arg0_Bind0(Class *object, MethodType method):
        m_object(object), m_method(method) {}
    virtual ~MethodClosure_Arg0_Bind0() {
        m_object = 0;
        m_method = 0;
    }
    virtual R Run() {
        ConditionalAutoDeleter<SelfDeleting, MethodClosure_Arg0_Bind0>
self_deleter(this);
        return (m_object->*m_method)();
    }
    virtual bool IsSelfDelete() const { return SelfDeleting; }
private:
    Class* m_object;
    MethodType m_method;
};

template <
    bool SelfDeleting,
    typename R,
    typename Arg1,
    typename Arg2,
    typename Arg3,
    typename PreArg1
>
class FunctionClosure_Arg2_Bind1 : public Closure<R, Arg2, Arg3> {
    typedef R (*FunctionType)(Arg1, Arg2, Arg3);
public:
    FunctionClosure_Arg2_Bind1(FunctionType function, PreArg1 pa1):
        m_function(function), m_pa1(pa1) {}
    virtual ~FunctionClosure_Arg2_Bind1() {
        m_function = 0;
    }
    virtual R Run(Arg2 arg2, Arg3 arg3) {
        ConditionalAutoDeleter<SelfDeleting, FunctionClosure_Arg2_Bind1>
self_deleter(this);
        return m_function(m_pa1, arg2, arg3);
    }
    virtual bool IsSelfDelete() const { return SelfDeleting; }
private:
    FunctionType m_function;
    PreArg1 m_pa1;
};