Goal:
  
  G : t
  HI : invariants G
  HG : acyclic_no_loop G
  x : V.t
  z : Z
  p : SPath G (V G) x (s G)
  wp : sweight p = z
  H0 : ~ VSet.In x (V G)
  ============================
   (z = 0)


DEBUG:Going to execute:
fun tac H =>
             try intros until H; intro_block H;
              (try simpl in H; DepElim.simplify_equations_in H);
              DepElim.generalize_by_eqs_vars H; CoreTactics.block_goal; 
              tac H; CoreTactics.intros_until_block; DepElim.simpl_dep_elim;
              CoreTactics.unblock_goal