Goal:
  
  G : t
  HI : invariants G
  HG : acyclic_no_loop G
  z : Z
  wp : sweight (spath_refl G (V G) (s G)) = z
  ============================
   (~ VSet.In (s G) (V G) -> let H := CoreTactics.block in z = 0)


DEBUG:Going to execute:
<coq-core.plugins.ltac::intro@0>