Goal:
  
  X1' : t
  X1 : t
  X : lt_ (pr1 {| pr1 := X1'; pr2 := X1 |}) (pr2 {| pr1 := X1'; pr2 := X1 |})
  ============================
   (forall x : t,
    {| pr1 := x; pr2 := x |} = {| pr1 := X1'; pr2 := X1 |} ->
    let H := CoreTactics.block in let H0 := CoreTactics.block in False)


DEBUG:Going to execute:
DepElim.decompose_exists xn id