Goal:
  
  G : t
  y_0 : V.t
  x_0 : V.t
  K : Z
  x : V.t
  y : V.t
  z : V.t
  e : EdgeOf G x y
  p : PathOf G y z
  IHp : weight (to_G' p) = weight p
  ============================
   (e.π1 + weight p = e.π1 + weight p)


DEBUG:Going to execute:
(solve [ do_atom | use_hyps; do_ccl ]) ||
             fail "Cannot solve this goal"