title: using declaration cannot refer to class member
body: <p>Basically, there is a class <code>Foo</code> defined in namespace <code>np</code>:</p>
  
  <pre><code>//Foo.h
  namespace np {
  
      class Foo {
          public:
            static void static_member();
           ...
          }
  ...
  }
  </code></pre>
  
  <p>I wanted to reference the static member in other sources, say <code>src.cc</code></p>
  
  <pre><code>//src.cc
  #include "Foo.h"
  
  using np::Foo::static_member;
  ...
  static_member()
  ...
  </code></pre>
  
  <p>after launching compiler, it complained:</p>
  
  <pre><code> error: using declaration cannot refer to class member
  </code></pre>
  
  <p>However, it worked when I changed the line to <code>np::Foo::static_member()</code>. So, what are proper ways to omit the interminable scope prefixes?</p>