Goal:
    A : Type  P : list A → list A → A → A → Type
  ============================
   (NoConfusion_All2_fold A P
      {| pr1 := {| pr1 := []; pr2 := [] |}; pr2 := All2_fold_nil P |}
      {| pr1 := {| pr1 := []; pr2 := [] |}; pr2 := All2_fold_nil P |}
    → let H := CoreTactics.block in
      {| pr1 := {| pr1 := []; pr2 := [] |}; pr2 := All2_fold_nil P |} =
      {| pr1 := {| pr1 := []; pr2 := [] |}; pr2 := All2_fold_nil P |})


DEBUG:Going to execute:
CoreTactics.intros_until_block
DEBUG LTAC Evaluated term: (NoConfusion_All2_fold A P
                              {|
                                pr1 := {| pr1 := []; pr2 := [] |};
                                pr2 := All2_fold_nil P
                              |}
                              {|
                                pr1 := {| pr1 := []; pr2 := [] |};
                                pr2 := All2_fold_nil P
                              |}
                            → let H := CoreTactics.block in
                              {|
                                pr1 := {| pr1 := []; pr2 := [] |};
                                pr2 := All2_fold_nil P
                              |} =
                              {|
                                pr1 := {| pr1 := []; pr2 := [] |};
                                pr2 := All2_fold_nil P
                              |})