Goal:
  
  G1 : t
  G2 : t
  l : labelling
  Gl := relabel_on G1 G2 l : t
  H : invariants G1
  preserves_edges : forall e : EdgeSet.elt,
                    EdgeSet.In e (E G1) -> EdgeSet.In e (E G2)
  HGl : correct_labelling G1 l
  H0 : invariants G2
  H1 : acyclic_no_loop G2
  embed : forall v1 v2 : VSet.elt,
          VSet.In v1 (V G1) ->
          VSet.In v2 (V G1) -> (lsp G2 v1 v2 <= lsp G1 v1 v2)%nbar
  G : t
  s0 : VSet.t
  s' : VSet.t
  x : V.t
  y : V.t
  z : V.t
  d : DisjointAdd x s0 s'
  e : EdgeOf G x y
  p0 : SPath G s0 y z
  s1 : VSet.t
  x1 : V.t
  p1 : SPath G s1 x1 z
  H2 : DisjointAdd x s1 s'
  H3 : EdgeOf G x x1
  H4 : SPath_sig_pack G s' x z (spath_step G s0 s' x y z d e p0) =
       SPath_sig_pack G s' x z (spath_step G s1 s' x x1 z H2 H3 p1)
  ============================
   ({| pr1 := {| pr1 := s0; pr2 := {| pr1 := y; pr2 := z |} |}; pr2 := p0 |} =
    {| pr1 := {| pr1 := s1; pr2 := {| pr1 := x1; pr2 := z |} |}; pr2 := p1 |})


DEBUG:Going to execute:
CoreTactics.block_goal; CoreTactics.revert_until H;
            CoreTactics.block_goal;
            CoreTactics.on_last_hyp ltac:(fun H' => revert H');
            DepElim.simplify_dep_elim; CoreTactics.intros_until_block
Level 2: evaluation returns
CoreTactics.block_goal; CoreTactics.revert_until H; CoreTactics.block_goal;
 CoreTactics.on_last_hyp ltac:(fun H' => revert H');
 DepElim.simplify_dep_elim; CoreTactics.intros_until_block;
 CoreTactics.intros_until_block
where
H := H4
of type
constr of type tacvalue

Level 1: evaluation returns
CoreTactics.block_goal; CoreTactics.revert_until H; CoreTactics.block_goal;
 CoreTactics.on_last_hyp ltac:(fun H' => revert H');
 DepElim.simplify_dep_elim; CoreTactics.intros_until_block;
 CoreTactics.intros_until_block
where
H := H4
of type
constr of type tacvalue