context has_q
    with parameters
      T: a type

    with members
      q: a function
          with parameters
            instance of type T 
          returning 
            instance of type T 


f: a function
    with forall
      z: a type
        with assertions
          instance of context has_q 
            with parameters
              instance of type z 


    returning 
      void 
    with body 
      Declaration of context has_r
          with parameters
            T: a type
            U: a type

          with members
            r: a function
                with parameters
                  instance of type T 
                  function
                      with parameters
                        instance of type T 
                        instance of type U 
                      returning 
                        instance of type T 

                returning 
                  instance of type T 


      Declaration of x: a extern type
      Declaration of y: a extern type
        with assertions
          instance of context has_r 
            with parameters
              instance of type x 
              instance of type y