Goal:
    X1' : list A.t  X1 : list A.t  X : lt_ X1' X1
  ============================
   (let H := CoreTactics.block in
    forall x : t,
    {| pr1 := x; pr2 := x |} = {| pr1 := X1'; pr2 := X1 |} ->
    let H0 := CoreTactics.block in let H1 := CoreTactics.block in False)


DEBUG:Going to execute:
fun tac p =>
             let ty := type of p in
             let eliminator := eval simpl in DepElim.elim in
             tac p eliminator