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|
  ============================
   (∀ (H := CoreTactics.block) (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 H0 := 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:
match goal with
           | hyp:context [ CoreTactics.block ]
             |- _ =>
                 cbn beta in hyp; eqns_specialize_eqs_block hyp;
                  cbn[eq_rect_r eq_rect] in hyp
           end