code: private boolean addCovarientProxyBridgeMethods( DynamicFunctionSymbol dfs )
    {
      IGosuClassInternal gsProxyClass = dfs.getGosuClass();
      if( gsProxyClass == null || !gsProxyClass.isProxy() )
      {
        // Not a proxy class so no java method to override
        return false;
      }
  
      if( dfs.getReturnType().isPrimitive() )
      {
        // Void or primitive return means no covariant override possible
        return false;
      }
  
      IJavaTypeInternal javaType = (IJavaTypeInternal)gsProxyClass.getJavaType();
      if( javaType.isInterface() )
      {
        IJavaClassMethod m = getMethodOverridableFromDfs( dfs, javaType.getBackingClassInfo() );
        if( m != null && Modifier.isAbstract( m.getModifiers() ) )
        {
          return genInterfaceProxyBridgeMethod( m, javaType.getBackingClassInfo() );
        }
      }
      return false;
    }
docs: Add a bridge method for a Java interface method that is not only implemented
  by a method in this Gosu class, but is also itself a covariant "override" of
  its super interface E.g.,
  <pre>
  interface JavaBase {
  public CharSequence makeText();
  }
  
  interface JavaSub extends JavaBase {
  public String makeText();
  }
  
  class GosuSub extends JavaSub {
  function makeText() : String ...
  }
  </pre>
  Here we need for this class to define a bridge method implementing JavaBase#makeText() : CharSequence