Goal:
  
  G1 : t
  G2 : t
  H : invariants G1
  ext := EdgeSet.diff (E G2) (E G1) : EdgeSet.t
  bs := border_set G1 ext : VSet.t
  H0 : invariants G2
  H1 : acyclic_no_loop G1
  H2 : acyclic_no_loop G2
  h : forall x y : VSet.elt,
      VSet.In x bs -> VSet.In y bs -> (lsp G2 x y <= lsp G1 x y)%nbar
  x : VSet.elt
  y : VSet.elt
  hx : VSet.In x (V G1)
  hy : VSet.In y (V G1)
  _a_ : Z
  p : SPath G2 (V G2) x y
  hp : sweight p = _a_
  hb : (Some (sweight p) <=
        lsp G2 x (first_in G1 G2 p) + lsp G1 (first_in G1 G2 p) y)%nbar
  ============================
   (Some _a_ <= lsp G1 x y)%nbar


DEBUG:Going to execute:
<coq-core.plugins.ssreflect::ssrmove@1> $1 $2
DEBUG LTAC Evaluated term: E
DEBUG LTAC Evaluated term: lsp0_spec_eq
DEBUG LTAC Evaluated term: (lsp0_spec_eq ?t ?z ?e)
DEBUG LTAC Evaluated term: (lsp0_spec_eq G2 _a_ _view_subject_)
DEBUG LTAC Evaluated term: (sweight_bound0 h (V G2) x y p hy)