Goal:
  
  x : t
  X : lt x x
  X0 := {| pr1 := {| pr1 := x; pr2 := x |}; pr2 := X |}
     : sigma
         (fun index : sigma (fun _ : t => t) => lt_ (pr1 index) (pr2 index))
  ============================
   (let H := CoreTactics.block in let H0 := CoreTactics.block in False)


DEBUG:Going to execute:
set (id'2 := pr2 id'); set (id'1 := pr1 id') in id'2