title: Function definition not found for a function declared inside unnamed namespace - how to resolve? (Visual Studio 2015)
body: <p>I installed Visual Studio <strong>2015</strong> and found that some of my code (that hadn't any problems in VS <strong>2013</strong>) now has got some errors indicated by green squiggles (which are supposed to be a <em>new productivity feature</em>). Yet the code still compiles successfully.</p>
  <p>Here's a quick example:</p>
  <pre><code>namespace
  {
      void test1(); // what once was OK in VS 2013,
      void test2(); // is now marked with squiggles in VS 2015
  }
  
  namespace named
  {
      void test3(); // OK, no problem
  }
  
  void        test1() { /*...*/ }
  void      ::test2() { /*...*/ }
  void named::test3() { /*...*/ }
  
  int main() { /*...*/ }
  </code></pre>
  <p>Theese are the squiggles in question</p>
  <p><a href="https://i.stack.imgur.com/sytZY.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/sytZY.png" alt="enter image description here" /></a></p>
  <p>Moving the mouse over them tells me that</p>
  <blockquote>
  <p>Function definition for 'test1' not found</p>
  <p>Function definition for 'test2' not found</p>
  </blockquote>
  <hr />
  <p>Somehow it turns out that only functions declared inside unnamed namespace trigger the squiggles.</p>
  <p>How is it supposed to be resolved?</p>