title: Invalid Modelica model works fine when instantiated in another model. Why?
body: <p>I have 2 Modelica models:</p>
  
  <pre><code>model parent
    child dingus;
  equation 
    dingus.a = 37;
    dingus.c = 666;
  end parent;
  </code></pre>
  
  <p>and </p>
  
  <pre><code>model child
    Real a;
    Real b;
    Real c;
  equation 
    a^3 + b^3 + c^3 = 1;
  end child;
  </code></pre>
  
  <p>When I check the code, <code>parent</code> checks out okay, but <code>child</code> gives errors about the mismatch of unknowns and equations, as expected.  Why does it work in <code>parent</code>, and is there a cleaner, best practice way of implementing this?  I want to use child in multiple different parents, and I may want to change how I interface with it so I don't want to overly define it.  </p>