Goal:
  
  G : t
  s0 : VSet.t
  s' : VSet.t
  x : V.t
  y : V.t
  z : V.t
  d : DisjointAdd x s0 s'
  e : EdgeOf x y
  a : SPath s0 y z
  idx3 : VSet.t
  idx4 : V.t
  idx2 : V.t
  b : SPath idx3 idx4 idx2
  H : NoConfusion_SPath
        {|
          pr1 := {| pr1 := s'; pr2 := {| pr1 := x; pr2 := z |} |};
          pr2 := spath_step d e a
        |}
        {|
          pr1 := {| pr1 := idx3; pr2 := {| pr1 := idx4; pr2 := idx2 |} |};
          pr2 := b
        |}
  ============================
   ({|
      pr1 := {| pr1 := s'; pr2 := {| pr1 := x; pr2 := z |} |};
      pr2 := spath_step d e a
    |} =
    {|
      pr1 := {| pr1 := idx3; pr2 := {| pr1 := idx4; pr2 := idx2 |} |};
      pr2 := b
    |})


DEBUG:Going to execute:
intro_block_id H
DEBUG LTAC Evaluated term: (let H := CoreTactics.block in
                            NoConfusion_SPath
                              {|
                                pr1 :=
                                  {|
                                    pr1 := s0;
                                    pr2 := {| pr1 := x; pr2 := x |}
                                  |};
                                pr2 := spath_refl s0 x
                              |}
                              {|
                                pr1 :=
                                  {|
                                    pr1 := idx3;
                                    pr2 := {| pr1 := idx4; pr2 := idx2 |}
                                  |};
                                pr2 := b
                              |} ->
                            let H0 := CoreTactics.block in
                            {|
                              pr1 :=
                                {|
                                  pr1 := s0; pr2 := {| pr1 := x; pr2 := x |}
                                |};
                              pr2 := spath_refl s0 x
                            |} =
                            {|
                              pr1 :=
                                {|
                                  pr1 := idx3;
                                  pr2 := {| pr1 := idx4; pr2 := idx2 |}
                                |};
                              pr2 := b
                            |})