sizeof…的可变模板递归。。。,但编译错误:没有匹配函数

#include <iostream>
using std::ostream; using std::istream;
using std::cin; using std::cout; using std::endl;

template <typename T, typename... Args>
ostream &myprint(ostream &os, const T &t, const Args&... rest) {
    if (sizeof...(rest)) {
        os << t << ", ";
        return myprint(os, rest...);
    }
    else
        return os << t;
}

int main(int argc, char *argv[]) {
    myprint(cout, "hello");
    return 0;
}

但是当我用 g++ -std=c++1y ,它抱怨:

error: no matching function for call to ‘myprint(std::ostream&)’
     return myprint(os, rest...);

myprint ,我已经检查了 sizeof...(rest) myprint(os, rest...) . 所以我不知道为什么它会呼叫 myprint(std::ostream&) .

基本情况 sizeof...

对于简单的不定递归情况:

template <typename T, typename... Args>
ostream &myprint(ostream &os, const T &t, const Args&... rest) {
    os << t << ", ";            // print the first argument
    return print(os, rest...);  // recursive call; print the other arguments
}

对于同一个错误,上面的代码根本无法编译。