anchor.diff:  function identity = |x| -> x
   ----
   
  -is expandend to :
  +is expandend to:
   
   [source,golo]
   ----
  
positive.code: 
  === Principles and syntax ===
  
  A function call can be marked with a bang like in this example :
  
  [source,golo]
  ----
  
negative.code: function identity = |x| -> x
  ----
  
  is expandend to:
  
  [source,golo]
  ----
  