Goal:
  
  G : t
  s0 : VSet.t
  x : V.t
  s1 : VSet.t
  x0 : V.t
  H : {| pr1 := s0; pr2 := x |} = {| pr1 := s1; pr2 := x0 |}
  ============================
   ({|
      pr1 := {| pr1 := s0; pr2 := {| pr1 := x; pr2 := x |} |};
      pr2 := spath_refl s0 x
    |} =
    {|
      pr1 := {| pr1 := s1; pr2 := {| pr1 := x0; pr2 := x0 |} |};
      pr2 := spath_refl s1 x0
    |})


DEBUG:Going to execute:
let rhs := fresh in
           set (rhs := y) in *; pattern sigma rhs; clearbody rhs; destruct H;
            simpl
DEBUG LTAC Evaluated term: H
DEBUG LTAC Evaluated term: ({| pr1 := s0; pr2 := x |} =
                            {| pr1 := s1; pr2 := x0 |})
Level 6: type of H
 has value 
({| pr1 := s0; pr2 := x |} = {| pr1 := s1; pr2 := x0 |})