Goal:
  
  G : t
  HI : invariants
  H : VSet.For_all (fun x : VSet.elt => lsp x x = Some 0) (V G)
  x : V.t
  p : PathOf x x
  Hp : weight p > 0
  hw : 0 < weight p + sweight (spath_refl (V G) x)
  q := simplify p (spath_refl (V G) x)
         (transitivity (VSetProp.union_sym (V G) (nodes p))
            (transitivity
               (VSetProp.union_subset_equal (s:=nodes p) (s':=
                  V G) (nodes_subset p)) (reflexivity (V G))))
    : ∑ x' : V.t, SPath (V G) x' x'
  Hq : 0 < sweight q.π2
  ============================
   False


DEBUG:Going to execute:
destruct q as [x' q]