Goal:
  
  A : Type
  B : Type
  P : B → A → A → Type
  b0 : B
  bs : list B
  hd : A
  hd' : A
  tl : list A
  p : P b0 hd hd'
  e0 : #|bs| = #|tl|
  b : B
  bs0 : list B
  hd0 : A
  hd'0 : A
  tl0 : list A
  p0 : P b hd0 hd'0
  e : #|bs0| = #|tl0|
  ============================
   (∀ e1 : NoConfusion_OnOne2All A B P
             {|
               pr1 :=
                 {|
                   pr1 := b0 :: bs;
                   pr2 := {| pr1 := hd :: tl; pr2 := hd' :: tl |}
                 |};
               pr2 := OnOne2All_hd P b0 bs hd hd' tl p e0
             |}
             {|
               pr1 :=
                 {|
                   pr1 := b :: bs0;
                   pr2 := {| pr1 := hd0 :: tl0; pr2 := hd'0 :: tl0 |}
                 |};
               pr2 := OnOne2All_hd P b bs0 hd0 hd'0 tl0 p0 e
             |},
      let H := CoreTactics.block in
      noConfusion_OnOne2All_obligation_2 A B P
        {|
          pr1 :=
            {|
              pr1 := b0 :: bs; pr2 := {| pr1 := hd :: tl; pr2 := hd' :: tl |}
            |};
          pr2 := OnOne2All_hd P b0 bs hd hd' tl p e0
        |}
        {|
          pr1 :=
            {|
              pr1 := b :: bs0;
              pr2 := {| pr1 := hd0 :: tl0; pr2 := hd'0 :: tl0 |}
            |};
          pr2 := OnOne2All_hd P b bs0 hd0 hd'0 tl0 p0 e
        |}
        (noConfusion_OnOne2All_obligation_1 A B P
           {|
             pr1 :=
               {|
                 pr1 := b0 :: bs;
                 pr2 := {| pr1 := hd :: tl; pr2 := hd' :: tl |}
               |};
             pr2 := OnOne2All_hd P b0 bs hd hd' tl p e0
           |}
           {|
             pr1 :=
               {|
                 pr1 := b :: bs0;
                 pr2 := {| pr1 := hd0 :: tl0; pr2 := hd'0 :: tl0 |}
               |};
             pr2 := OnOne2All_hd P b bs0 hd0 hd'0 tl0 p0 e
           |} e1) = e1)


DEBUG:Going to execute:
try (intro; CoreTactics.intros_until_block)