title: g++ warning options for casting pair?
body: <p>I just found that C++ doesn't give any warnings for casting from <code>pair&lt;double, int&gt;</code> to <code>pair&lt;int, int&gt;</code>, which is a little surprising. Here is my program <code>test_pair.cpp</code>:</p>
  
  <pre><code>#include &lt;vector&gt;
  #include &lt;utility&gt;
  using namespace std;
  
  
  int main()
  {
      std::vector&lt;pair&lt;int, int&gt; &gt; v;
      pair&lt;double, int&gt; p = make_pair(3.8, 3);
      v.push_back(p);                                                           
  }
  </code></pre>
  
  <p>I compile it using <code>g++ test_type.cpp -Wall -Wconversion</code>, but still no warnings are generated. I am using g++ v4.6.1. Anyone got any idea how to make g++ generate a warning for this, or it just can't be done?</p>