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
  IHp0 : Acc
           (fun
              x
               y : sigma
                     (fun
                        index : sigma
                                  (fun _ : VSet.t =>
                                   sigma (fun _ : V.t => V.t)) =>
                      SPath G (pr1 index) (pr1 (pr2 index)) (pr2 (pr2 index)))
            =>
            SPath_direct_subterm G (pr1 (pr1 x)) (pr1 (pr2 (pr1 x)))
              (pr2 (pr2 (pr1 x))) (pr1 (pr1 y)) (pr1 (pr2 (pr1 y)))
              (pr2 (pr2 (pr1 y))) (pr2 x) (pr2 y))
           {|
             pr1 := {| pr1 := s0; pr2 := {| pr1 := y; pr2 := z |} |};
             pr2 := p0
           |}
  s1 : VSet.t
  x1 : V.t
  y1 : V.t
  p1 : SPath G s1 x1 y1
  h1 : sigma
         (fun H : VSet.t =>
          sigma
            (fun H0 : V.t =>
             sigma
               (fun H1 : V.t =>
                sigma
                  (fun H2 : VSet.t =>
                   sigma
                     (fun H3 : V.t =>
                      sigma
                        (fun H4 : V.t =>
                         sigma (fun _ : SPath G H H0 H1 => SPath G H2 H3 H4)))))))
  h : SPath_direct_subterm G (pr1 h1) (pr1 (pr2 h1)) 
        (pr1 (pr2 (pr2 h1))) (pr1 (pr2 (pr2 (pr2 h1))))
        (pr1 (pr2 (pr2 (pr2 (pr2 h1)))))
        (pr1 (pr2 (pr2 (pr2 (pr2 (pr2 h1))))))
        (pr1 (pr2 (pr2 (pr2 (pr2 (pr2 (pr2 h1)))))))
        (pr2 (pr2 (pr2 (pr2 (pr2 (pr2 (pr2 h1)))))))
  ============================
   ({|
      pr1 := s1;
      pr2 :=
        {|
          pr1 := x1;
          pr2 :=
            {|
              pr1 := y1;
              pr2 :=
                {|
                  pr1 := s';
                  pr2 :=
                    {|
                      pr1 := x;
                      pr2 :=
                        {|
                          pr1 := z;
                          pr2 :=
                            {|
                              pr1 := p1;
                              pr2 := spath_step G s0 s' x y z d e p0
                            |}
                        |}
                    |}
                |}
            |}
        |}
    |} = h1 ->
    let H := CoreTactics.block in
    let H0 := CoreTactics.block in
    Acc
      (fun
         x
          y : sigma
                (fun
                   index : sigma
                             (fun _ : VSet.t => sigma (fun _ : V.t => V.t))
                 => SPath G (pr1 index) (pr1 (pr2 index)) (pr2 (pr2 index)))
       =>
       SPath_direct_subterm G (pr1 (pr1 x)) (pr1 (pr2 (pr1 x)))
         (pr2 (pr2 (pr1 x))) (pr1 (pr1 y)) (pr1 (pr2 (pr1 y)))
         (pr2 (pr2 (pr1 y))) (pr2 x) (pr2 y))
      {|
        pr1 := {| pr1 := s1; pr2 := {| pr1 := x1; pr2 := y1 |} |}; pr2 := p1
      |})


DEBUG:Going to execute:
try rename id into id',id' into id
Level 3: evaluation returns
try rename id into id',id' into id; cont id'1 id
where
t := {|
       pr1 := s1;
       pr2 :=
         {|
           pr1 := x1;
           pr2 :=
             {|
               pr1 := y1;
               pr2 :=
                 {|
                   pr1 := s';
                   pr2 :=
                     {|
                       pr1 := x;
                       pr2 :=
                         {|
                           pr1 := z;
                           pr2 :=
                             {|
                               pr1 := p1;
                               pr2 := spath_step G s0 s' x y z d e p0
                             |}
                         |}
                     |}
                 |}
             |}
         |}
     |}
of type
constr
id'1 := h1
of type
constr
id' := h
of type
constr
id := h
of type
constr
cont := fun id id' => DepElim.decompose_exists id id'
        where
        id := h
        of type
        constr
of type
tacvalue of type tacvalue