Goal:
  
  A : Type
  B : Type
  P : A → B → Type
  Q : A → B → Type
  H1' : list A
  H1 : list B
  H : All2 Q H1' H1
  ============================
   ({| pr1 := []; pr2 := [] |} = {| pr1 := H1'; pr2 := H1 |}
    → let H := CoreTactics.block in
      let H0 := CoreTactics.block in All2 (Trel_conj P Q) [] [])


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