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:
intros until H
Level 2: Backtrace:

No quantified hypothesis named b in current goal even after head-reduction.
Level 2: Backtrace:

No quantified hypothesis named b in current goal even after head-reduction.