Goal:
  
  A : Type
  P : nat → A → A → Type
  i : nat
  hd : A
  tl : list A
  tl' : list A
  a : OnOne2i P (S i) tl tl'
  i0 : nat
  hd0 : A
  tl0 : list A
  tl'0 : list A
  b : OnOne2i P (S i0) tl0 tl'0
  ============================
   (∀ e : NoConfusion_OnOne2i A P
            {|
              pr1 :=
                {|
                  pr1 := i; pr2 := {| pr1 := hd :: tl; pr2 := hd :: tl' |}
                |};
              pr2 := OnOne2i_tl P i hd tl tl' a
            |}
            {|
              pr1 :=
                {|
                  pr1 := i0;
                  pr2 := {| pr1 := hd0 :: tl0; pr2 := hd0 :: tl'0 |}
                |};
              pr2 := OnOne2i_tl P i0 hd0 tl0 tl'0 b
            |},
      let H := CoreTactics.block in
      noConfusion_OnOne2i_obligation_2 A P
        {|
          pr1 :=
            {| pr1 := i; pr2 := {| pr1 := hd :: tl; pr2 := hd :: tl' |} |};
          pr2 := OnOne2i_tl P i hd tl tl' a
        |}
        {|
          pr1 :=
            {|
              pr1 := i0; pr2 := {| pr1 := hd0 :: tl0; pr2 := hd0 :: tl'0 |}
            |};
          pr2 := OnOne2i_tl P i0 hd0 tl0 tl'0 b
        |}
        (noConfusion_OnOne2i_obligation_1 A P
           {|
             pr1 :=
               {| pr1 := i; pr2 := {| pr1 := hd :: tl; pr2 := hd :: tl' |} |};
             pr2 := OnOne2i_tl P i hd tl tl' a
           |}
           {|
             pr1 :=
               {|
                 pr1 := i0;
                 pr2 := {| pr1 := hd0 :: tl0; pr2 := hd0 :: tl'0 |}
               |};
             pr2 := OnOne2i_tl P i0 hd0 tl0 tl'0 b
           |} e) = e)


DEBUG:Going to execute:
intro; CoreTactics.intros_until_block