Goal:
  
  G : t
  HG : acyclic_no_loop
  x : V.t
  y : V.t
  z : V.t
  e : EdgeOf x y
  p : PathOf y z
  IHp : weight p <= sweight (simplify2 p)
  F0 : true = true -> VSet.In x (snodes (simplify2 p))
  F1 : ~ VSet.In x (snodes (simplify2 p)) <-> true = false
  ============================
   (e.π1 + weight p <=
    sweight
      (SPath_sub
         (VSetProp.subset_add_2 (s2:=nodes p) x (reflexivity (nodes p)))
         (split (simplify2 p) x (left (F0 eq_refl))).2))


DEBUG:Going to execute:
<coq-core.plugins.ssreflect::ssrrewrite@0> $1 $2
DEBUG LTAC Evaluated term: (VSet.mem x (snodes (simplify2 p)))