title: call rvalue-constructor from an lvalue-constructor
body: <p>I'd like to provide a constructor definition only once – for both lvalue and rvalue.</p>
  
  <pre><code>class A;
  
  class B {
      B(A const&amp; a): B(A(a)) {}
      B(A&amp;&amp;);
  };
  </code></pre>
  
  <p>Is <code>B::B(A&amp;&amp;)</code> guaranteed to be called by <code>B::B(A const&amp;)</code>?</p>