Goal:
  
  A : Type
  P : list A → list A → A → A → Type
  d : A
  d' : A
  Γ : list A
  Γ' : list A
  a : All2_fold P Γ Γ'
  p : P Γ Γ' d d'
  d0 : A
  d'0 : A
  Γ0 : list A
  Γ'0 : list A
  b : All2_fold P Γ0 Γ'0
  p0 : P Γ0 Γ'0 d0 d'0
  H : NoConfusion_All2_fold A P
        {|
          pr1 := {| pr1 := d :: Γ; pr2 := d' :: Γ' |};
          pr2 := All2_fold_cons P a p
        |}
        {|
          pr1 := {| pr1 := d0 :: Γ0; pr2 := d'0 :: Γ'0 |};
          pr2 := All2_fold_cons P b p0
        |}
  ============================
   (let H := CoreTactics.block in
    {|
      pr1 := {| pr1 := d :: Γ; pr2 := d' :: Γ' |};
      pr2 := All2_fold_cons P a p
    |} =
    {|
      pr1 := {| pr1 := d0 :: Γ0; pr2 := d'0 :: Γ'0 |};
      pr2 := All2_fold_cons P b p0
    |})


DEBUG:Going to execute:
match goal with
           | |- let _ := CoreTactics.block in _ => intros _
           | |- _ => try (intro; CoreTactics.intros_until_block)
           end