Backend fails on when equations

[Martin Sjölund]

Backend fails to generate residuals for the following Modelica code:

model WhenValidResult 
  Real x,y; 
equation 
  x + y = 5; 
  when sample(0,2) then 
  y = 7 - 2*x; 
  end when; 
end WhenValidResult;

Note: Changing the problem slightly does change the error messages from the backend.
x = y-5 removes "findDiscreteEquation failed, searching for $x" for example.

From forums: ​http://www.openmodelica.org/index.php/forum/topic?id=64&p=1#p284