title: C++: "incomplete type is not allowed" when declaring an object - What is the cause?
body: <p>The following code was provided to me by one of the JUCE admins, and on his Mac he says it is working, but for me, I get "incomplete type is not allowed" on the object declarations in "Private".</p>
  
  <p>I cannot understand the cause of the error.</p>
  
  <pre><code>class LabeledSlider : public GroupComponent
  
  {
      public:
      LabeledSlider (const String&amp; name)
      {
          setText (name);
          setTextLabelPosition (Justification::centredTop);
          addAndMakeVisible (slider);
      }
  
      void resized() override
      {
          slider.setBounds (getLocalBounds().reduced (10));
      }
  
      Slider slider 
      { 
          Slider::RotaryHorizontalVerticalDrag, Slider::TextBoxBelow 
      };
  
   private:
      LabeledSlider frequency { "Frequency" };
      LabeledSlider level { "Level" };
  
  };
  </code></pre>
  
  <p>Screencap of Visual Studio Error</p>
  
  <p><img src="https://i.stack.imgur.com/mV04R.png" alt=""></p>
  
  <p>My Visual Studio Community 2017 is fully up to date, so I'm not sure why it works for him and not me. </p>
  
  <p>What would be the issue here? How do I fix it? </p>
  
  <p>Please if you know the fix be specific or really clear about what you mean </p>