Check at Compile-Time if Template Argument is void

I'm trying to wrap the Windows API functions to check errors when I so choose. As I found out in a previous SO question, I could use a template function to call the API function, and then call GetLastError() to retrieve any error it might have set. I could then pass this error to my Error class to let me know about it.

Here's the code for the template function:

template<typename TRet, typename... TArgs>
TRet Wrap(TRet(WINAPI *api)(TArgs...), TArgs... args)
{
    TRet ret = api(args...);
    //check for errors
    return ret;
}

Using this I can have code as follows

int WINAPI someFunc (int param1, BOOL param2); //body not accessible

int main()
{
    int ret = someFunc (5, true); //works normally
    int ret2 = Wrap (someFunc, 5, true); //same as above, but I'll get a message if there's an error
}

This works wonderfully. However, there is one possible problem. Take the function

void WINAPI someFunc();

When subbing this into the template function, it looks as follows:

void Wrap(void(WINAPI *api)())
{
    void ret = api(); //<-- ahem! Can't declare a variable of type void...
    //check for errors
    return ret; //<-- Can't return a value for void either
}

To get around this, I tried creating a version of the template where I replaced TRet with void. Unfortunately, this actually just causes an ambiguity of which one to use.

That aside, I tried using

if (strcmp (typeid (TRet).name(), "v") != 0) //typeid(void).name() == "v"
{
    //do stuff with variable to return
}

else
{
    //do stuff without returning anything
}

However, typeid is a runtime comparison, so the code still doesn't compile due to trying to declare a void variable, even if it never will.

Next, I tried using std::is_same <TRe